Light-emitting element, display device, electronic device and lighting device

Abstract

Light-emitting element (150) comprising: a pair of electrodes (101; 102); and a layer (130) between the pair of electrodes (101; 102), wherein the layer (130) comprises a guest material (131) and a host material (132), wherein the guest material (131) can convert a triplet excitation energy into a light emission, wherein the host material (132) comprises a pyrimidine skeleton, a pyridazine skeleton and / or a triazine skeleton, where a HOMO level of the guest material (131) is higher than a HOMO level of the host material (132), where an energy difference between a LUMO level of the guest material (131) and the HOMO level of the guest material (131) is greater than an energy difference between a LUMO level of the host material (132) and the HOMO level of the host material (132), and wherein an energy difference between the LUMO level of the host material (132) and the HOMO level of the guest material (131) is greater than or equal to a transition energy calculated from an absorption edge of an absorption spectrum of the guest material (131).

Description

Technical field

[0001] One embodiment of the present invention relates to a light-emitting element. State of the art

[0002] In recent years, intensive research and development have been conducted on light-emitting elements that utilize electroluminescence (EL). In a basic structure of such a light-emitting element, a layer containing a light-emitting material (an EL layer) is positioned between a pair of electrodes. By applying a voltage between the electrode pair of this element, light emission can be obtained from the light-emitting material.

[0003] Since the aforementioned light-emitting element is of a self-illuminating type, a display device using this light-emitting element offers the following advantages: high visibility, no need for backlighting, low power consumption, and the like. Furthermore, the display device is also advantageous in that it can be made thin and lightweight and exhibits a high response speed.

[0004] In a light-emitting element (e.g., an organic EL element) whose EL layer contains an organic material as the light-emitting material and is positioned between a pair of electrodes, applying a voltage between the electrode pair causes the injection of electrons from a cathode and holes from an anode into the light-emitting EL layer, resulting in a current flow. As a consequence of recombination of the injected electrons and holes, the light-emitting organic material is excited to a state that produces light emission.

[0005] It should be noted that an excitation state formed by an organic material can be a singlet excitation state (S*) or a triplet excitation state (T*). Light emission from the singlet excitation state is called fluorescence, and light emission from the triplet excitation state is called phosphorescence. The S* to T* generation ratio in the light-emitting element is 1:3. In other words, a light-emitting element containing a phosphorescent compound has a higher light emission efficiency than a light-emitting element containing a fluorescent compound.Consequently, light-emitting elements containing phosphorescent materials that can convert the energy of the triplet excitation state into light emission have been actively developed in recent years (see, for example, patent document 1).

[0006] The energy required to excite an organic material depends on the energy difference between its LUMO and HOMO levels. This energy difference is approximately equal to the singlet excitation energy. In a light-emitting element containing a phosphorescent organic material, triplet excitation energy is converted into light emission energy. Consequently, when the energy difference between the singlet and triplet excitation states of an organic material is large, the energy required to excite the organic material is higher than the light emission energy by an amount equal to this energy difference. This difference between the energy required to excite the organic material and the light emission energy affects the properties of a light-emitting element: the driving voltage of the light-emitting element increases.Techniques for reducing the drive voltage are being researched and developed (see patent document 2). Further light-emitting elements are disclosed in patent documents 3 to 7.

[0007] Among light-emitting elements containing phosphorescent materials, one element in particular that emits blue light has not yet been used in practice, as it is difficult to develop a stable organic material with a high triplet excitation energy level. This has motivated researchers to develop highly reliable light-emitting elements that exhibit phosphorescence with high emission efficiency. [Reference][Patent documents] [Patent Document 1] JP 2010-182699 A [Patent Document 2] JP 2012-212879 A [Patent Document 3] US 2013 / 0134395 A1 [Patent Document 4] US 2011 / 0279020 A1 [Patent Document 5] US 2012 / 0098417 A1 [Patent Document 6] US 2012 / 0153268 A1 [Patent document 7] WO 2012 / 108881 A1 Disclosure of the invention

[0008] An iridium complex is known as a phosphorescent material with high emission efficiency. An iridium complex comprising a pyridine framework or a nitrogen-containing five-membered heterocyclic framework as ligands is known as a high-emission iridium complex. Although the pyridine and nitrogen-containing five-membered heterocyclic frameworks exhibit high triplet excitation energies, they have poor electron-accepting properties. Consequently, the HOMO and LUMO levels of the iridium complex with these frameworks as ligands are high, and hole charge carriers are readily injected into them, whereas this is not the case for electron charge carriers. Therefore, in the high-emission iridium complex, excitation of charge carriers by direct charge carrier recombination is difficult, meaning that efficient light emission is challenging.

[0009] In light of the foregoing, one object of an embodiment of the present invention is to provide a light-emitting element that has high emission efficiency and contains a phosphorescent material. Another object of an embodiment of the present invention is to provide a light-emitting element with low power consumption. Another object of an embodiment of the present invention is to provide a light-emitting element with high reliability. Another object of an embodiment of the present invention is to provide a novel light-emitting element. Another object of an embodiment of the present invention is to provide a novel light-emitting device. Another object of an embodiment of the present invention is to provide a novel display device.

[0010] It should be noted that the description of the foregoing problem does not preclude the existence of further problems. In one embodiment of the present invention, it is unnecessary to fulfill all problems. Further problems are apparent from the explanation of the description and the like, and can be derived from it.

[0011] One embodiment of the present invention is a light-emitting element comprising a guest material and a host material comprising a pyrimidine framework, a pyridazine framework and / or a triazine framework, wherein a HOMO level of the guest material is higher than a HOMO level of the host material, wherein an energy difference between a LUMO level of the guest material and the HOMO level of the guest material is greater than an energy difference between a LUMO level of the host material and the HOMO level of the host material, wherein the guest material has a function for converting a triplet excitation energy into light emission, and wherein an energy difference between the LUMO level of the host material and the HOMO level of the guest material is greater than or equal to a transition energy calculated from an absorption edge of an absorption spectrum of the guest material.

[0012] One embodiment of the present invention is a light-emitting element comprising a guest material and a host material comprising a pyrimidine framework, a pyridazine framework and / or a triazine framework, wherein a HOMO level of the guest material is higher than a HOMO level of the host material, wherein an energy difference between a LUMO level of the guest material and the HOMO level of the guest material is greater than an energy difference between a LUMO level of the host material and the HOMO level of the host material, wherein the guest material has a function for converting a triplet excitation energy into a light emission, and wherein an energy difference between the LUMO level of the host material and the HOMO level of the guest material is greater than or equal to a light emission energy of the guest material.

[0013] In each of the above structures, the energy difference between the LUMO level of the guest material and the HOMO level of the guest material is preferably 0.4 eV or more greater than the transition energy calculated from the absorption edge of the absorption spectrum of the guest material. Preferably, the energy difference between the LUMO level of the guest material and the HOMO level of the guest material is 0.4 eV or more greater than the light emission energy of the guest material.

[0014] In each of the aforementioned structures, the host material preferably exhibits a difference between a singlet excitation energy level and a triplet excitation energy level of greater than 0 eV and less than or equal to 0.2 eV. Preferably, the host material includes a function for providing thermally activated delayed fluorescence.

[0015] In each of the aforementioned structures, the host material preferably has a function for supplying excitation energy to the guest material. An emission spectrum of the host material preferably comprises a wavelength range that overlaps with an absorption band on the lowest energy side of the absorption spectrum of the guest material.

[0016] In each of the above structures, the guest material preferably contains iridium. Preferably, the guest material emits light.

[0017] In each of the aforementioned structures, the host material preferably has a function for transporting an electron. Preferably, the host material has a function for transporting a hole. The host material preferably further comprises a framework with a π-electron-rich heteroaromatic ring and / or an aromatic amine framework. The framework with the π-electron-rich heteroaromatic ring preferably comprises an acridine framework, a phenoxazine framework, a phenothiazine framework, a furan framework, a thiophene framework, and / or a pyrrole framework.

[0018] It should be noted that the description of the foregoing effects does not preclude the existence of further effects. In one embodiment of the present invention, it is unnecessary to achieve all effects. Further effects are apparent from the explanation of the description, the drawings, the claims, and the like, and can be derived from them. Brief description of the drawings Fig. 1A and Fig. Figure 1B shows schematic cross-sectional views of a light-emitting element of an embodiment of the present invention. Fig. 2A and Fig. Figure 2B are schematic illustrations showing a correlation of energy levels and a correlation between energy bands in a light-emitting layer of a light-emitting element of an embodiment of the present invention. Fig. 3A and Fig. Figure 3B are schematic cross-sectional views of a light-emitting element of an embodiment of the present invention. Fig. 4A and Fig. Figure 4B shows schematic diagrams illustrating a correlation between energy levels and a correlation between energy bands in a light-emitting layer of a light-emitting element of an embodiment of the present invention. Fig. 5A and Fig. Figure 5B are schematic cross-sectional views of a light-emitting element of an embodiment of the present invention, and Fig. 5C is a schematic diagram showing a correlation between energy levels in a light-emitting layer. Fig. 6A and Fig. Figure 6B shows schematic cross-sectional views of a light-emitting element of an embodiment of the present invention, and Fig. 6C is a schematic diagram showing a correlation between energy levels in a light-emitting layer. Fig. 7A and Fig. Figures 7B are each a schematic cross-sectional view of a light-emitting element of an embodiment of the present invention. Fig. 8A and Fig. Figure 8B each shows a schematic cross-sectional view of a light-emitting element of an embodiment of the present invention. Fig. 9A to Fig. Figure 9C are schematic cross-sectional views illustrating a method for manufacturing a light-emitting element of an embodiment of the present invention. Fig. 10A to Fig. Figure 10C are schematic cross-sectional views illustrating the method for manufacturing a light-emitting element of an embodiment of the present invention. Fig. 11A and Fig. Figures 11B are a top view and a schematic cross-sectional view representing a display device of an embodiment of the present invention. Fig. 12A and Fig. Figures 12B are each a schematic cross-sectional view representing a display device of an embodiment of the present invention. Fig. Figure 13 is a schematic cross-sectional view representing a display device of an embodiment of the present invention. Fig. 14A and Fig. Figure 14B are schematic cross-sectional views, each representing a display device of an embodiment of the present invention. Fig. 15A and Fig. Figure 15B are schematic cross-sectional views representing a display device of an embodiment of the present invention. Fig. Figure 16 is a schematic cross-sectional view representing a display device of an embodiment of the present invention. Fig. 17A and Fig. Figures 17B are each a schematic cross-sectional view representing a display device of an embodiment of the present invention. Fig. Figure 18 is a schematic cross-sectional view representing a display device of an embodiment of the present invention. Fig. 19A and Fig. Figures 19B are each a schematic cross-sectional view representing a display device of an embodiment of the present invention. Fig. 20A and Fig. Figures 20B are a block diagram and a circuit diagram illustrating a display device of an embodiment of the present invention. Fig. 21A and Fig. Figures 21B are circuit diagrams, each representing a pixel circuit of a display device of an embodiment of the present invention. Fig. 22A and Fig. Figures 22B are circuit diagrams, each representing a pixel circuit of a display device of an embodiment of the present invention. Fig. 23A and Fig. Figures 23B are perspective views of an example of a touchscreen of an embodiment of the present invention. Fig. 24A to Fig. Figures 24C are cross-sectional views of examples of a display device and a touch sensor of an embodiment of the present invention. Fig. 25A and Fig. Figures 25B are cross-sectional views, each representing an example of a touchscreen of an embodiment of the present invention. Fig. 26A and Fig. Figures 26B are a block diagram and a timing diagram of a touch sensor of an embodiment of the present invention. Fig. Figure 27 is a circuit diagram of a touch sensor of an embodiment of the present invention. Fig. Figure 28 is a perspective view showing a display module of an embodiment of the present invention. Fig. 29A to Fig. 29G represent electronic devices of an embodiment of the present invention. Fig. 30A to Fig. 30F represent electronic devices of an embodiment of the present invention. Fig. 31A to Fig. Figure 31D represents electronic devices of an embodiment of the present invention. Fig. 32A and Fig. Figures 32B are perspective views showing a display device of an embodiment of the present invention. Fig. 33A to Fig. Figures 33C are a perspective view and cross-sectional views depicting light-emitting devices of an embodiment of the present invention. Fig. 34A to Fig. Figures 34D are each a cross-sectional view representing a light-emitting device of an embodiment of the present invention. Fig. 35A to Fig. 35C represent an electronic device and a lighting device of an embodiment of the present invention. Fig. Figure 36 represents lighting devices of an embodiment of the present invention. Fig. Figure 37 is a schematic cross-sectional view representing a light-emitting element of an example. Fig. Figure 38 shows the power efficiency-luminance properties of light-emitting elements of an example. Fig. Figure 39 shows luminance-voltage properties of light-emitting elements of an example. Fig. Figure 40 shows the external quantum efficiency luminance properties of light-emitting elements of an example. Fig. Figure 41 shows the power efficiency-luminance properties of light-emitting elements of an example. Fig. Figure 42 shows electroluminescence spectra of light-emitting elements of an example. Fig. Figure 43 shows emission spectra of a host material of an example. Fig. Figure 44 shows transient fluorescence properties of a host material of an example. Fig. Figure 45 shows an absorption spectrum and an emission spectrum of a guest material of an example. Fig. Figure 46 shows the power efficiency-luminance properties of light-emitting elements of an example. Fig. Figure 47 shows luminance-voltage properties of light-emitting elements of an example. Fig. Figure 48 shows external quantum efficiency luminance properties of light-emitting elements of an example. Fig. Figure 49 shows the power efficiency-luminance properties of light-emitting elements of an example. Fig. Figure 50 shows electroluminescence spectra of light-emitting elements of an example. Fig. Figure 51 shows the power efficiency-luminance properties of a light-emitting element of an example. Fig. Figure 52 shows luminance-voltage properties of a light-emitting element of an example. Fig. Figure 53 shows external quantum efficiency luminance properties of a light-emitting element of an example. Fig. Figure 54 shows the power efficiency-luminance properties of a light-emitting element of an example. Fig. Figure 55 shows an electroluminescence spectrum of a light-emitting element of an example. Fig. Figure 56 shows an absorption spectrum and an emission spectrum of a guest material of an example. Fig. Figure 57 shows the power efficiency-luminance properties of a light-emitting element of an example. Fig. Figure 58 shows luminance-voltage properties of a light-emitting element of an example. Fig. Figure 59 shows external quantum efficiency luminance properties of a light-emitting element of an example. Fig. Figure 60 shows the power efficiency-luminance properties of a light-emitting element of an example. Fig. Figure 61 shows an electroluminescence spectrum of a light-emitting element of an example. Fig. Figure 62 shows emission spectra of a host material of an example. Fig. 63A and Fig. Figure 63B shows transient fluorescence properties of a host material of an example. Fig. Figure 64 shows the power efficiency-luminance properties of a light-emitting element of an example. Fig. Figure 65 shows luminance-voltage properties of a light-emitting element of an example. Fig. Figure 66 shows external quantum efficiency luminance properties of a light-emitting element of an example. Fig. Figure 67 shows the power efficiency-luminance properties of a light-emitting element of an example. Fig. Figure 68 shows an electroluminescence spectrum of a light-emitting element of an example. Fig. Figure 69 shows the power efficiency-luminance properties of a light-emitting element of an example. Fig. Figure 70 shows the luminance-voltage properties of a light-emitting element of an example. Fig. Figure 71 shows the external quantum efficiency luminance properties of a light-emitting element of an example. Fig. Figure 72 shows the power efficiency-luminance properties of a light-emitting element of an example. Fig. Figure 73 shows an electroluminescence spectrum of a light-emitting element of an example. Fig. Figure 74 shows emission spectra of a host material of an example. Fig. Figure 75 shows an absorption spectrum and an emission spectrum of a guest material of an example. Fig. Figure 76 shows the power efficiency-luminance properties of a light-emitting element of an example. Fig. Figure 77 shows luminance-voltage properties of a light-emitting element of an example. Fig. Figure 78 shows external quantum efficiency luminance properties of a light-emitting element of an example. Fig. Figure 79 shows the power efficiency-luminance properties of a light-emitting element of an example. Fig. Figure 80 shows an electroluminescence spectrum of a light-emitting element of an example. Fig. Figure 81 shows emission spectra of a host material of an example. Best way to implement the invention

[0019] Embodiments of the present invention are described in detail below with reference to the drawings. However, the present invention is not limited to the following description, and its modes and details can be modified in various ways without departing from the essence and scope of the present invention. Therefore, the present invention should not be considered as limited to the content of the following embodiments.

[0020] It should be noted that, for the sake of simplicity, the position, size, area, or the like of any structure shown in drawings and the like is not always precisely depicted. The disclosed invention is therefore not necessarily limited to the position, size, area, or the like disclosed in the drawings and the like.

[0021] It should be noted that ordinal numbers, such as "first," "second," and the like, are used in this description and the like for convenience only, and they do not indicate the sequence of steps or the order of layers. Therefore, for example, an adequate description may be given even if "first" is replaced by "second" or "third." Furthermore, the ordinal numbers in this description and the like are not necessarily the same as those that specify an embodiment of the present invention.

[0022] In the explanations of the modes of the present invention in this description and the like, which are based on the drawings, in some cases identical components in different drawings are generally provided with the same reference numerals.

[0023] In this description and similar texts, the terms "film" and "layer" can be used interchangeably. For example, in some cases, the term "conducting layer" can be replaced by the term "conducting film." Similarly, in some cases, the term "insulating film" can be replaced by the term "insulating layer."

[0024] In this description and the like, a singlet excitation state (S*) denotes a singlet state with excitation energy . An S1 level denotes the lowest level of the singlet excitation energy levels, i.e., the excitation energy level of the lowest singlet excitation state. A triplet excitation state (T*) denotes a triplet state with excitation energy . A T1 level denotes the lowest level of the triplet excitation energy levels, i.e., the excitation energy level of the lowest triplet excitation state. It should be noted that in this description and the like, a singlet excitation state and a singlet excitation energy level sometimes refer to the lowest singlet excitation state and the S1 level, respectively. A triplet excitation state and a triplet excitation energy level sometimes refer to the lowest triplet excitation state and the T1 level, respectively.

[0025] In this description and similar usage, a fluorescent material refers to a material that emits light in the visible spectrum when it relaxes from the singlet excitation state to the ground state. A phosphorescent material refers to a material that emits light in the visible spectrum at room temperature when it relaxes from the triplet excitation state to the ground state. That is, a phosphorescent material refers to a material that can convert triplet excitation energy into visible light.

[0026] Phosphorescence emission energy or triplet excitation energy can be obtained from a wavelength of an emission peak (including a shoulder) or a rising section on the shortest wavelength side of the phosphorescence emission. It should be noted that phosphorescence emission in a low-temperature environment (e.g., 10 K) can be observed by time-resolved photoluminescence. The emission energy of thermally activated delayed fluorescence can be obtained from a wavelength of an emission peak (including a shoulder) or a rising section on the shortest wavelength side of the thermally activated delayed fluorescence.

[0027] It should be noted that in this description and similar texts, "room temperature" refers to a temperature higher than or equal to 0 °C and lower than or equal to 40 °C.

[0028] In this description and similar usage, a wavelength range of blue refers to a wavelength range greater than or equal to 400 nm and less than 500 nm, and blue light has at least one peak in this region of its emission spectrum. A wavelength range of green refers to a wavelength range greater than or equal to 500 nm and less than 580 nm, and green light has at least one peak in this region of its emission spectrum. A wavelength range of red refers to a wavelength range greater than or equal to 580 nm and less than or equal to 680 nm, and red light has at least one peak in this region of its emission spectrum. (Version 1)

[0029] In this embodiment, a light-emitting element of an embodiment of the present invention is subsequently described using the following: Fig. 1A and Fig. 1B, Fig. 2A and Fig. 2B, Fig. 3A and Fig. 3B as well as Fig. 4A and Fig. 4B described. <Strukturbeispiel 1 des Licht emittierenden Elements>

[0030] First, a structure of the light-emitting element of an embodiment of the present invention will be described below based on Fig. 1A and Fig. 1B described.

[0031] Fig. Figure 1A is a schematic cross-sectional view of a light-emitting element 150 of an embodiment of the present invention.

[0032] The light-emitting element 150 comprises a pair of electrodes (an electrode 101 and an electrode 102) and an EL layer 100 between the pair of electrodes. The EL layer 100 comprises at least one light-emitting layer 130.

[0033] The EL layer 100, which is in Fig. Figure 1A shows that, in addition to the light-emitting layer, 130 functional layers are included, such as a hole injection layer 111, a hole transport layer 112, an electron transport layer 118 and an electron injection layer 119.

[0034] Although this embodiment is described assuming that electrode 101 and electrode 102 of the electrode pair serve as the anode and cathode, respectively, this is not the case for the structure of the light-emitting element 150. That is to say, electrode 101 can be a cathode and electrode 102 an anode, and the order of the layers between the electrodes can be reversed. In other words, the hole injection layer 111, the hole transport layer 112, the light-emitting layer 130, the electron transport layer 118, and the electron injection layer 119 can be arranged in that order, starting from the anode side.

[0035] The structure of the EL layer 100 is not based on the one in Fig. The structure shown in Figure 1A is limited, and a structure comprising at least one layer selected from the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119 can be used. Alternatively, the EL layer 100 can, for example, include a functional layer capable of lowering a hole or electron injection barrier, improving a hole or electron transport property, reducing a hole or electron transport property, or suppressing an electrode quenching effect. It should be noted that the functional layers can each be a single layer or stacked layers.

[0036] Fig. Figure 1B is a schematic cross-sectional view showing an example of the light-emitting layer 130 in Fig. 1A represents the light-emitting layer 130 in Fig. 1B contains a guest material 131 and a host material 132.

[0037] In the light-emitting layer 130, the host material 132 is present with the highest weight fraction, and the guest material 131 is dispersed in the host material 132.

[0038] Guest material 131 is an organic, light-emitting material. The organic light-emitting material preferably has a function for converting triplet excitation energy into light emission and is preferably a material suitable for providing phosphorescence (hereinafter also referred to as the phosphorescent material). In the following description, a phosphorescent material is used as guest material 131. Guest material 131 can also be referred to as the phosphorescent material. <Lichtemissionsmechanismus 1 des Licht emittierenden Elements>

[0039] Next, the light emission mechanism of the light-emitting layer 130 will be described.

[0040] In the light-emitting element 150 of an embodiment of the present invention, applying a voltage between the pair of electrodes (electrodes 101 and 102) causes electrons and holes to be injected from the cathode and the anode, respectively, into the EL layer 100, thereby generating a current. By recombinating the injected electrons and holes, the guest material 131 in the light-emitting layer 130 of the EL layer 100 is excited to a state in order to provide light emission.

[0041] It should be noted that light emission from the guest material 131 can be obtained through the following two processes: (α) a direct recombination process; and (β) an energy transfer process. <<(α) Direct recombination process>>

[0042] First, the direct recombination process in guest material 131 is described. Charge carriers (electrons and holes) recombine in guest material 131, and the guest material 131 is excited. In this case, the energy required to excite guest material 131 by the direct charge carrier recombination process depends on the energy difference between the lowest unoccupied molecular orbital (LUMO) level and the highest occupied molecular orbital (HOMO) level of guest material 131, and this energy difference is approximately equal to the singlet excitation energy. Since guest material 131 is a phosphorescent material, a triplet excitation energy is converted into light emission.If the energy difference between the singlet excitation state and the triplet excitation state of the guest material 131 is large, then the energy required to excite the guest material 131 is higher than the light emission energy by the amount corresponding to the energy difference.

[0043] The energy difference between the energy required to excite the guest material 131 and the light emission energy influences the element properties of a light-emitting element: The drive voltage of the light-emitting element varies. Consequently, in the (α) direct recombination process, the light emission start voltage of the light-emitting element is higher than the voltage corresponding to the light emission energy in the guest material 131.

[0044] In the case where the guest material 131 has a high light emission energy, it exhibits a high LUMO level. Consequently, the injection of electrons as charge carriers into the guest material 131 is made more difficult, and the direct recombination of charge carriers (electrons and holes) occurs less likely in the guest material 131. Therefore, a high emission efficiency is unlikely to be achieved in the light-emitting element. <<(β) Energy transfer process>>

[0045] Next, we will show Fig. 2A is a schematic representation of the correlation of energy levels to describe the energy transfer process between host material 132 and guest material 131. The following clarifies what terms and symbols in Fig. 2A represents: Guest (131): the guest material 131 (the phosphorescent material); Host (132): the host material 132; S G: an S1 level of the guest material 131 (the phosphorescent material); T G : a T1 level of the guest material 131 (the phosphorescent material); S H : an S1 level of host material 132; and T H : a T1 level of host material 132.

[0046] In the case where charge carriers recombine in the host material 132 and the singlet excitation state and the triplet excitation state of the host material 132 are formed, as in Route E1 and Route E2 in Fig. 2A shows both the singlet excitation energy and the triplet excitation energy of the host material 132 from the singlet excitation energy level (S H ) and the triplet excitation energy level (T H ) of the host material 132 to the triplet excitation energy level (T GThe energy of the guest material 131 is transferred, and the guest material 131 is brought into a triplet excitation state. Phosphorescence is obtained from the guest material 131 in the triplet excitation state.

[0047] It should be noted that both the singlet excitation energy level (S H ) as well as the triplet excitation energy level (T H ) of the host material 132 preferably higher than or equal to the triplet excitation energy level (T G ) of the host material 131. In this case, the singlet excitation energy and the triplet excitation energy generated in the host material 132 can be efficiently derived from the singlet excitation energy level (S). H ) and the triplet excitation energy level (T H ) of the host material 132 to the triplet excitation energy level (T G ) of the guest material 131 will be transferred.

[0048] In other words, in the light-emitting layer 130, excitation energy is transferred from the host material 132 to the guest material 131.

[0049] It should be noted that in the case where the light-emitting layer 130 contains the host material 132, the guest material 131 and a material that differs from the host material 132 and the guest material 131, the material that differs from the host material 132 and the guest material 131 preferably has a triplet excitation energy level in the light-emitting layer 130 that is higher than the triplet excitation energy level (T). H ) of the host material 132. Consequently, a quenching of the triplet excitation energy of the host material 132 occurs with a lower probability, leading to an efficient energy transfer to the guest material 131.

[0050] To reduce an energy loss that occurs when the singlet excitation energy of the host material 132 drops to the triplet excitation energy level (T G ) of the guest material 131 is transferred, the energy difference between the singlet excitation energy level (S H ) and the triplet excitation energy level (T H ) of the host material 132 preferably small.

[0051] Fig. Figure 2B is an energy band diagram of guest material 131 and host material 132. Fig. 2B represents “Guest (131)” the guest material 131, “Host (132)” represents the host material 132, ΔE G The energy difference between the LUMO level and the HOMO level of the guest material 131 is represented by ΔE H represents the energy difference between the LUMO level and the HOMO level of the host material 132 and represents ΔE Brepresents the energy difference between the LUMO level of the host material 132 and the HOMO level of the guest material 131.

[0052] To cause the guest material 131 to emit light with a short wavelength and high emission energy, the following applies: The greater the energy difference (ΔE) G The smaller the energy difference (ΔE) between the LUMO level and the HOMO level of the host material 131, the better. However, the excitation energy in the light-emitting element 150 is preferably as small as possible to reduce the drive voltage; therefore, the following applies: The smaller the excitation energy of an excited state formed by the host material 132, the better. Therefore, the energy difference (ΔE) H ) between the LUMO level and the HOMO level of the host material 132 preferably small.

[0053] Guest material 131 is a phosphorescent material and thus possesses the function of converting triplet excitation energy into light emission. Furthermore, the energy in a triplet excitation state is more stable than in a singlet excitation state. Consequently, guest material 131 can emit light with an energy lower than the energy difference (ΔE). G ) between the LUMO level and the HOMO level of the guest material 131. The inventors of the present invention have found that even in the case where the energy difference (ΔE G ) between the LUMO level and the HOMO level of the guest material 131 is greater than the energy difference (ΔE) H) between the LUMO level and the HOMO level of the host material 132, the excitation energy transfer from an excited state of the host material 132 to the guest material 131 is possible and light emission from the guest material 131 can be obtained as long as a light emission energy (abbreviation: ΔE) Em ) of the guest material 131 or a transition energy (abbreviation: ΔE) abs ), calculated from an absorption edge of an absorption spectrum of the guest material 131, equal to or less than ΔE H is. If ΔE G of the guest material 131 is greater than the light emission energy (ΔE) Em ) of the guest material 131 or the transition energy (ΔE abs ), calculated from the absorption edge of the absorption spectrum of the guest material 131, is a high electrical energy, which ΔE GThis corresponds to the necessary voltage to directly bring about an electrical excitation of the host material 131, thereby increasing the drive voltage of the light-emitting element. However, in one embodiment of the present invention, the host material 132 is electrically excited with an electrical energy that corresponds to ΔE. H corresponds to (which is smaller than ΔE) G ), and the guest material 131 is brought into an excited state by an energy transfer from it, so that light emission from the guest material 131 can be obtained with a low drive voltage and high efficiency. Therefore, the light emission start voltage (a voltage at the time when the luminance reaches 1 cd / m²) can be 2 exceeds) of the light-emitting element of an embodiment of the present invention shall be lower than the voltage corresponding to the light emission energy (ΔE). Em) of the guest material. That is to say, an embodiment of the present invention is particularly useful in the case where ΔE G is significantly larger than the light emission energy (ΔE) Em ) of the guest material 131 or the transition energy (ΔE abs ), calculated from the absorption edge of the absorption spectrum of the guest material 131 (for example, in the case where the guest material is a blue light-emitting material). It should be noted that the light emission energy (ΔE) Em ) can be derived from a wavelength of an emission peak (the maximum value or including a shoulder) on the shortest wavelength side or a wavelength of an increasing section of the emission spectrum.

[0054] It should be noted that if the guest material 131 contains a heavy metal, intersystem crossing between a singlet state and a triplet state is promoted by a spin-orbit interaction (an interaction between the spin angular momentum and the orbital angular momentum of an electron), and a transition between a singlet ground state and a triplet excitation state of the guest material 131 is enabled in some cases. Consequently, the emission efficiency and absorption probability relating to the transition between the singlet ground state and the triplet excitation state of the guest material 131 can be increased. Accordingly, the guest material 131 preferably contains a metallic element with a large spin-orbit interaction, in particular an element of the platinum group (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), or platinum (Pt)).Iridium is particularly preferred because it can increase the absorption probability, which concerns the direct transition between a singlet ground state and a triplet excited state.

[0055] To enable the guest material 131 to emit light with a high luminous emission energy (light with a short wavelength), the lowest triplet excitation energy level of the guest material 131 is preferably high. To achieve this high lowest triplet excitation energy level, a ligand coordinated to a heavy metal atom of the guest material 131 preferably exhibits a high lowest triplet excitation energy level, low electron acceptor properties, and a high LUMO level.

[0056] Such a guest material tends to have a molecular structure with a high HOMO level and high hole-accepting properties. If the guest material 131 has a molecular structure with high hole-accepting properties, the HOMO level of the guest material 131 is sometimes higher than that of the host material 132. Furthermore, if ΔE G is greater than ΔE H The LUMO level of guest material 131 is higher than the LUMO level of host material 132. It should be noted that the energy difference between the LUMO level of guest material 131 and the LUMO level of host material 132 is greater than the energy difference between the HOMO level of guest material 131 and the HOMO level of host material 132.

[0057] In the light-emitting layer 130, when the HOMO level of the guest material 131 is higher than that of the host material 132 and the LUMO level of the guest material 131 is higher than that of the host material 132, charge carriers (holes and electrons) injected by the pair of electrodes (electrode 101 and electrode 102) readily inject holes injected from the anode into the guest material 131 and electrons injected from the cathode readily inject electrons into the host material 132. Consequently, in some cases, the guest material 131 and the host material 132 form an exciplex. In particular, when the energy difference (ΔE) B ) between the LUMO level of the host material 132 and the HOMO level of the guest material 131 becomes smaller than the emission energy of the guest material 131 (ΔE Em), the generation of exciplexes formed by the guest material 131 and the host material 132 is predominant. In such a case, the probability that the guest material 131 itself forms an excited state is lower, which reduces the emission efficiency of the light-emitting element.

[0058] It should be noted that the reactions described above can be represented by the general formula (G11) or (G12). H−+G+→(H⋅G)* H+G*→(H⋅G)*

[0059] The general formula (G11) represents a reaction in which the host material 132 donates an electron (H - ) records and the guest material 131 a hole (G +The general formula (G12) represents a reaction in which the guest material 131 (G*) in the excited state interacts with the host material 132 (H) in the ground state, thereby forming an exciplex ((H·G)*). The formation of the exciplex ((H·G)*) by the host material 132 and the guest material 131 makes it more difficult for the host material 131 alone to form an excited state (G*).

[0060] An exciplex formed by the host material 132 and the guest material 131 has an excitation energy that is approximately equal to the energy difference (ΔE). B ) between the LUMO level of the host material 132 and the HOMO level of the guest material 131. The inventors of the present invention have found that when the energy difference (ΔE) B) between the LUMO level of the host material 132 and the HOMO level of the guest material 131 greater than or equal to an emission energy (ΔE) Em ) of the guest material 131 or a transition energy (ΔE abs ) calculated from the absorption edge of the absorption spectrum of guest material 131, the reaction to form an exciplex by the host material 132 and the guest material 131 can be prevented, thus allowing light emission from the guest material 131 to be obtained efficiently. At this point, the guest material 131 readily absorbs excitation energy, since ΔE abs is smaller than ΔE B . Excitation of the guest material 131 by absorbing the excitation energy requires less energy and provides a more stable excitation state than the formation of an exciplex by the host material 132 and the guest material 131.

[0061] As described above, even if the energy difference (ΔE) G ) between the LUMO level and the HOMO level of the guest material 131 is greater than the energy difference (ΔE) H ) between the LUMO level and the HOMO level of the host material 132, an excitation energy is efficiently transferred from the host material 132 in an excited state to the guest material 131, as long as the transition energy (ΔE abs ), calculated from the absorption edge of the absorption spectrum of the guest material 131, equal to or less than ΔE H This results in a light-emitting element with high emission efficiency and low drive voltage, which is a feature of one embodiment of the present invention. In this case, the formula ΔE G > ΔE H ≥ ΔE abs (ΔE G is greater than ΔE H , and ΔE H is greater than or equal to ΔE abs) fulfilled. Therefore, the mechanism of an embodiment of the present invention is suitable in the case where the energy difference (ΔE) G ) between the LUMO level and the HOMO level of the guest material 131 is greater than the transition energy (ΔE) abs ), calculated from the absorption edge of the absorption spectrum of the guest material 131. In particular, the energy difference (ΔE) G ) between the LUMO level and the HOMO level of the guest material 131 preferably by 0.3 eV or more, more preferably by 0.4 eV or more, greater than the transition energy (ΔE) abs ), calculated from the absorption edge of the absorption spectrum of the guest material 131. Since the light emission energy (ΔE Em ) of the guest material 131 equal to or less than ΔE abs is the energy difference (ΔE G) between the LUMO level and the HOMO level of the guest material 131 preferably by 0.3 eV or more, more preferably by 0.4 eV or more, greater than the light emission energy (ΔE) Em ) of the guest material 131.

[0062] Furthermore, if the HOMO level of the guest material 131 is higher than the HOMO level of the host material 132, the formula ΔE is preferably used. B ≥ ΔE abs (ΔE G is greater than or equal to ΔE abs ) or ΔE B ≥ ΔE Em (ΔE B is greater than or equal to ΔE Em ) is satisfied. Therefore, the formula ΔE is preferably used. G > ΔE H > ΔE B ≥ ΔE abs (ΔE G is greater than ΔE H , ΔE H is greater than ΔE B , and ΔE B is greater than or equal to ΔE abs ) or the formula ΔE G > ΔE H > ΔE B ≥ ΔE Em (ΔE G is greater than ΔE H , ΔEH is greater than ΔE B , and ΔE B is greater than or equal to ΔE Em ) fulfilled. The foregoing conditions also represent important discoveries of an embodiment of the present invention.

[0063] The energy difference (ΔE) H ) between the LUMO level and the HOMO level of the host material 132 is equal to or slightly greater than the singlet excitation energy level (S H ) of the host material 132. The singlet excitation energy level (S H ) of host material 132 is higher than the triplet excitation energy level (T H ) of the host material 132. The triplet excitation energy level (T H ) of host material 132 is higher than or equal to the triplet excitation energy level (T G ) of the guest material 131. Consequently, the formula ΔE G > ΔE H ≥ S H > T H ≥ T G (ΔE G is greater than ΔE H , ΔEH is greater than or equal to S H , S H is higher than T H , and T H is higher than or equal to T G ) is satisfied. It should be noted that ΔT G equal to or slightly less than ΔE abs in the case where the absorption affecting the absorption edge of the absorption spectrum of guest material 131 is related to the transition between the singlet ground state and the triplet excited state of guest material 131. To determine ΔE G to obtain a value that is at least 0.3 eV larger than ΔE abs , is therefore the energy difference between S H and T H preferably smaller than the energy difference between ΔE G and ΔE abs In particular, the energy difference between S H and T H preferably greater than 0 eV and less than or equal to 0.2 eV, more preferably greater than 0 eV and less than or equal to 0.1 eV.

[0064] As an example of a material exhibiting a small energy difference between the singlet and triplet excitation energy levels and suitable for use as host material 132, a thermally activated delayed fluorescent (TADF) material can be specified. The thermally activated delayed fluorescent material exhibits a small energy difference between the singlet and triplet excitation energy levels and a function for converting triplet excitation energy to singlet excitation energy by reverse intersystem crossing. It should be noted that the host material 132 of an embodiment of the present invention does not necessarily exhibit high reverse intersystem crossing efficiency. H to S H and a high luminescence quantum yield of S Hmust have this feature; thus, materials can be selected from a wide range of options.

[0065] To exhibit a small difference between the singlet and triplet excitation energy levels, the host material 132 preferably comprises a framework with a hole-transporting function (a hole-transporting property) and a framework with an electron-transporting function (an electron-transporting property). In this case, in the excited state of the host material 132, the framework with a hole-transporting property exhibits the HOMO, and the framework with an electron-transporting property exhibits the LUMO; thus, there is very little overlap between the HOMO and the LUMO. This means that a donor-acceptor excitation state is readily formed in a single molecule, and the difference between the singlet and triplet excitation energy levels is small. It should be noted that in the host material 132, the difference between the singlet excitation energy level (S) H) and the triplet excitation energy level (T H ) preferably greater than 0 eV and less than or equal to 0.2 eV.

[0066] It should be noted that a molecular orbital describes the spatial distribution of electrons in a molecule and can indicate the probability of finding electrons. Furthermore, the molecular orbital can be used to describe the electron configuration of the molecule (the spatial distribution and energy of the electrons) in detail.

[0067] In the case where the host material 132 comprises a framework with strong donor properties, a hole injected into the light-emitting layer 130 is readily injected into and transported within the host material 132. Similarly, in the case where the host material 132 comprises a framework with strong acceptor properties, an electron injected into the light-emitting layer 130 is readily injected into and transported within the host material 132. Both holes and electrons are preferably injected into the host material 132, in which case the excited state of the host material 132 is readily established.

[0068] The shorter the emission wavelength of the guest material 131 (the higher the light emission energy ΔE) Em The greater the energy difference (ΔE), the greater the energy difference (ΔE). G) between the LUMO level and the HOMO level of the guest material 131, and consequently a greater energy is required for the direct electrical excitation of the guest material. However, in one embodiment of the present invention, when the transition energy (ΔE) abs ), calculated from the absorption edge of the absorption spectrum of the guest material 131, equal to or less than ΔE H is, the guest material 131 with an energy as small as ΔE H is, which is smaller than ΔE G , are stimulated, thereby reducing the power consumption of the light-emitting element. Consequently, the effect of the light emission mechanism of an embodiment of the present invention becomes effective in the case where the energy difference between the transition energy (ΔE) abs ), calculated from the absorption edge of the absorption spectrum of the guest material 131, and the energy difference (ΔE G) between the LUMO level and the HOMO level of the guest material is 131 (i.e., especially in the case where the guest material is a blue light-emitting material).

[0069] If the transition energy (ΔE) abs ), calculated from the absorption edge of the absorption spectrum of the guest material 131, decreases, the light emission energy (ΔE) also decreases. Em ) of the guest material 131. In this case, it is difficult to obtain a light emission that requires high energy, such as blue light emission. That is: If there is a difference between ΔE abs and ΔE G If the size is too large, it is difficult to obtain high-energy light emission, such as blue light emission.

[0070] For these reasons, the energy difference (ΔE G) between the LUMO level and the HOMO level of the guest material 131 preferably by 0.3 eV to and including 0.8 eV, more preferably by 0.4 eV to and including 0.8 eV, and even more preferably by 0.5 eV to and including 0.8 eV greater than the transition energy (ΔE) abs ), calculated from the absorption edge of the absorption spectrum of the guest material 131. Since the light emission energy (ΔE Em ) of the guest material 131 equal to or less than ΔE abs is the energy difference (ΔE G ) between the LUMO level and the HOMO level of the guest material 131 preferably by 0.3 eV to and including 0.8 eV, more preferably by 0.4 eV to and including 0.8 eV, and even more preferably by 0.5 eV to and including 0.8 eV greater than the light emission energy (ΔE) Em ) of the guest material 131.

[0071] Furthermore, the guest material 131 acts as a hole trap in the light-emitting layer 130, since its HOMO level is higher than that of the host material 132. This is preferable because the charge carrier balance in the light-emitting layer can be easily controlled, resulting in a longer lifetime. However, if the HOMO level of the guest material 131 is too high, the ΔE described above will occur. B small. Consequently, the energy difference between the HOMO level of the guest material 131 and the HOMO level of the host material 132 is preferably greater than or equal to 0.05 eV and less than or equal to 0.4 eV. Furthermore, the energy difference between the LUMO level of the guest material 131 and the LUMO level of the host material 132 is preferably 0.05 eV or more, more preferably 0.1 eV or more, and even more preferably 0.2 eV or more. This is suitable for easy injection of electron carriers into the host material 132.

[0072] Furthermore, since the energy difference (ΔE H ) between the LUMO level and the HOMO level of the host material 132 is smaller than the energy difference (ΔE) G) between the LUMO level and the HOMO level of the guest material 131, as an excitation state formed by recombination of charge carriers (holes and electrons) injected into the light-emitting layer 130, an excitation state formed by the host material 132 is energetically more stable. Consequently, most excitation states generated by direct recombination of charge carriers in the light-emitting layer 130 are present as excitation states formed by the host material 132. Accordingly, the structure of one embodiment of the present invention facilitates the excitation energy transfer from the host material 132 to the guest material 131, resulting in a lower drive voltage of the light-emitting element and higher emission efficiency.

[0073] According to the relationship between the LUMO level and the HOMO level described above, the oxidation potential of the guest material 131 is preferably lower than the oxidation potential of the host material 132. It should be noted that the oxidation potential and the reduction potential can be measured by cyclic voltammetry (CV).

[0074] If the light-emitting layer 130 has the structure described above, light emission from the guest material 131 of the light-emitting layer 130 can be obtained efficiently. <Energieübertragungsmechanismus>

[0075] Next, factors that control the processes of intermolecular energy transfer between host material 132 and guest material 131 are described. Two mechanisms have been proposed for intermolecular energy transfer: the Förster mechanism (dipole-dipole interaction) and the Dexter mechanism (electron exchange interaction). <<Förster-Mechanismus> >

[0076] In energy transfer via the Förster mechanism, no direct contact between molecules is necessary; energy is transferred through a resonance phenomenon of a dipole vibration between the host material 132 and the guest material 131. Through this resonance phenomenon, the host material 132 transfers energy to the guest material 131, thus bringing the excited host material 132 to a ground state and the guest material 131 to an excited state. It should be noted that the rate constant k h*→g the Förster mechanism is represented by formula (1). kh*→g=9000c4K2ϕIn10128π5n4NτR6∫f'h(v)εg(v)v4dv

[0077] In formula (1) v represents a frequency, f' represents h(v) represents a normalized emission spectrum of the host material 132 (a fluorescence spectrum during energy transfer from a singlet excitation state and a phosphorescence spectrum during energy transfer from a triplet excitation state), ε g (v) represents a molar absorption coefficient of the guest material 131, N represents Avogadro's number, n represents a refractive index of a medium, R represents an intermolecular distance between the host material 132 and the guest material 131, τ represents a measured lifetime of an excitation state (fluorescence lifetime or phosphorescence lifetime), c represents the speed of light, ϕ represents a luminescence quantum yield (a fluorescence quantum yield for energy transfer from a singlet excitation state and a phosphorescence quantum yield for energy transfer from a triplet excitation state), and K represents 2represents a coefficient (0 to 4) for the orientation of a transition dipole moment between the host material 132 and the guest material 131. It should be noted that with random orientation K 2 = 2 / 3 applies. < <dexter-mechanismus>>

[0078] In the Dexter mechanism, the host material 132 and the guest material 131 are located near a contact-effective region where their orbitals overlap, and the host material 132, in an excited state, and the guest material 131, in a ground state, exchange electrons, resulting in energy transfer. It should be noted that the rate constant k h*→g the Dexter mechanism is represented by formula (2). kh*→g=(2πh)K2exp(−2RL)∫f'h(v)ε'g(v)dv

[0079] In formula (2), h represents a Planck constant, K represents a constant with an energy dimension, v represents a frequency, f' represents h (v) represents a normalized emission spectrum of the host material 132 (a fluorescence spectrum during energy transfer from a singlet excitation state and a phosphorescence spectrum during energy transfer from a triplet excitation state), ε' g (v) represents a normalized absorption spectrum of the guest material 131, L represents an effective molecular radius and R represents an intermolecular distance between the host material 132 and the guest material 131.

[0080] Here, the efficiency of energy transfer from the host material 132 to the guest material 131 (energy transfer efficiency ϕ) is measured. ET ) represented by formula (3). In the formula, k represents r a rate constant of a light emission process (fluorescence in the energy transfer from a singlet excitation state and phosphorescence in the energy transfer from a triplet excitation state) of the host material 132 represents k n a rate constant in a process without light emission (during thermal deactivation or intersystem crossing) of the host material 132 and τ represents a measured lifetime of an excitation state of the host material 132. ϕET=kh*→gkr+kn+kh*→g=kh*→g(1τ)+kh*→g

[0081] According to formula (3), it has been found that the energy transfer efficiency ϕ ET by increasing the velocity constant k h*→g during energy transfer, so that another competing velocity constant k r + k n (= 1 / τ) becomes relatively small. < <Konzept zur Förderung der Energieübertragung»

[0082] Energy transfer via the Förster mechanism results in a high energy transfer efficiency ϕ. ET A high emission quantum yield ϕ (a fluorescence quantum yield during energy transfer from a singlet excitation state and a phosphorescence quantum yield during energy transfer from a triplet excitation state) is obtained. Furthermore, the emission spectrum (the fluorescence spectrum during energy transfer from the singlet excitation state) of the host material 132 preferably overlaps to a large extent with the absorption spectrum (absorption corresponding to the transition from the singlet ground state to the triplet excitation state) of the guest material 131. It is also preferred that the molar absorption coefficient of the guest material 131 is also high. That is, the emission spectrum of the host material 132 overlaps with the absorption band of the absorption spectrum of the guest material 131 that is located on the longest wavelength side.

[0083] To determine the velocity constant k h*→g To increase the energy transfer efficiency via the Dexter mechanism, the emission spectrum (a fluorescence spectrum during energy transfer from a singlet excitation state and a phosphorescence spectrum during energy transfer from a triplet excitation state) of the host material 132 preferably overlaps to a large extent with the absorption spectrum (absorption corresponding to the transition from a singlet ground state to a triplet excitation state) of the guest material 131. Therefore, the energy transfer efficiency can be optimized by ensuring that the emission spectrum of the host material 132 overlaps with the absorption band of the absorption spectrum of the guest material 131 that lies on the longest wavelength side. <Strukturbeispiel 2 des Licht emittierenden Elements>

[0084] Next, a light-emitting element with a structure that differs from the one in Fig. 1A and Fig. The structure shown in 1B differs based on Fig. 3A and Fig. 3B described.

[0085] Fig. Figure 3A is a schematic cross-sectional view of a light-emitting element 152 of an embodiment of the present invention. Fig. In some cases, section 3A has a similar function to the one in Fig. 1A through the same hatching pattern as in Fig. Sections 1A are shown without a separate reference symbol. Furthermore, common reference symbols are used for sections with similar functions, and a detailed description of the sections is omitted in some cases.

[0086] The light-emitting element 152 comprises the pair of electrodes (electrode 101 and electrode 102) and the EL layer 100 between the pair of electrodes. The EL layer 100 comprises at least one light-emitting layer 135.

[0087] Fig. Figure 3B is a schematic cross-sectional view showing an example of the light-emitting layer 135 in Fig. 3A represents the light-emitting layer 135 in Fig. 3B contains at least the guest material 131, the host material 132 and a host material 133.

[0088] In the light-emitting layer 135, the host material 132 or the host material 133 is present with the highest weight fraction, and the guest material 131 is dispersed in the host material 132 and the host material 133. <Lichtemissionsmechanismus 2 des Licht emittierenden Elements>

[0089] Next, the light emission mechanism of the light-emitting layer 135 will be described.

[0090] In the light-emitting element 152 of an embodiment of the present invention, the guest material 131 in the light-emitting layer 135 of the EL layer 100 is also brought into an excited state to provide light emission by electrons and holes that are injected by the pair of electrodes (the electrode 101 and the electrode 102).

[0091] It should be noted that light emission from the guest material 131 can be obtained through the following two processes: (α) a direct recombination process; and (β) an energy transfer process.

[0092] It should be noted that the direct recombination process (α) is not described here, as it is similar to the direct recombination process in the description of the light emission mechanism of the light-emitting layer 130. <<(β) Energy transfer process>>

[0093] To describe the energy transfer process of host material 132, host material 133 and guest material 131, shows Fig. 4A is a schematic representation of the correlation of energy levels. The following clarifies what terms and symbols in Fig. 4A represents, and the other terms and symbols in Fig. 4A are the same as those in Fig. 2A: Host (133): the host material 133; S A : an S1 level of host material 133; and T A : a T1 level of host material 133.

[0094] In the case where charge carriers recombine in the host material 132 and the singlet excitation state and the triplet excitation state of the host material 132 are formed, as in Route E1 and Route E2 in Fig. 4A shows both the singlet excitation energy and the triplet excitation energy of the host material 132 from the singlet excitation energy level (S H ) and the triplet excitation energy level (T H ) of the host material 132 to the triplet excitation energy level (T G The energy of the guest material 131 is transferred, and the guest material 131 is brought into a triplet excitation state. Phosphorescence is obtained from the guest material 131 in the triplet excitation state.

[0095] It should be noted that, in order to efficiently transfer excitation energy from the host material 132 to the guest material 131, the triplet excitation energy level (T) A ) of the host material 133 is preferably higher than the triplet excitation energy level (T H ) of the host material 132. Consequently, a quenching of the triplet excitation energy of the host material 132 occurs with a lower probability, leading to an efficient energy transfer to the guest material 131.

[0096] If the HOMO level of the guest material is 131, as shown in an energy band diagram in Fig. As shown in Figure 4B, the energy difference (ΔE) is higher than the HOMO level of the host material 132. G ) between the LUMO level and the HOMO level of the guest material 131 preferably greater than the energy difference (ΔE) H ) between the LUMO level and the HOMO level of the host material 132 and is ΔE H preferably greater than the energy difference (ΔE) B ) between the LUMO level of the host material 132 and the HOMO level of the guest material 131, as described in the light emission mechanism 1 of the light-emitting element.

[0097] Preferably, the LUMO level of host material 133 is higher than the LUMO level of host material 132, and the HOMO level of host material 133 is lower than the HOMO level of guest material 131. That is, the energy difference between the LUMO level and the HOMO level of host material 133 is greater than the energy difference (ΔE). B ) between the LUMO level of host material 132 and the HOMO level of guest material 131. Consequently, the reaction to form an exciplex by host material 133 and host material 132 and the reaction to form an exciplex by host material 133 and guest material 131 can be prevented. In Fig. 4B represents “host (133)” the host material 133, and the other terms and symbols are the same as those in Fig. 2B.

[0098] It should be noted that the difference between the LUMO level of the host material 133 and the LUMO level of the host material 132, as well as the difference between the HOMO level of the host material 133 and the HOMO level of the guest material 131, are each preferably greater than or equal to 0.1 eV, more preferably greater than or equal to 0.2 eV. This energy difference is suitable because electron charge carriers and hole charge carriers injected by the pair of electrodes (electrode 101 and electrode 102) are readily injected into the host material 132 and the guest material 131, respectively.

[0099] It should be noted that the LUMO level of host material 133 may be either higher or lower than the LUMO level of guest material 131, and that the HOMO level of host material 133 may be either higher or lower than the HOMO level of host material 132.

[0100] Furthermore, the energy difference between the LUMO level and the HOMO level of the host material 133 is preferably greater than the energy difference (ΔE). H ) between the LUMO level and the HOMO level of the host material 132. In this case, since the energy difference (ΔE H ) between the LUMO level and the HOMO level of the host material 132 is smaller than the energy difference (ΔE) G ) between the LUMO level and the HOMO level of the guest material 131, as an excitation state formed by recombination of charge carriers (holes and electrons) injected into the light-emitting layer 135, an excitation state formed by the host material 132, which is energetically more stable than an excitation state formed by the host material 133, and an excitation state formed by the guest material 131. Therefore, most of the excitation states generated by recombination of charge carriers in the light-emitting layer 135 are present as excitation states formed by the host material 132.Accordingly, in the light-emitting layer 135, excitation energy transfer from an excitation state of the host material 132 to the guest material 131 occurs just as easily as in the structure of the light-emitting layer 130, so that the light-emitting element 152 can be driven with low drive voltage and high emission efficiency.

[0101] Even in the case where holes and electrons recombine in the host material 133 and an excited state is formed by the host material 133, an excitation energy of the host material 133 can be immediately transferred to the host material 132 if the energy difference between the LUMO level and the HOMO level of the host material 133 is greater than the energy difference between the LUMO level and the HOMO level of the host material 132. Subsequently, the excitation energy is transferred to the guest material 131 by a process similar to that described in the light emission mechanism of the light-emitting layer 130, thereby enabling light emission from the guest material 131.It should be noted that when the possibility of holes and electrons also recombinating in the host material 133 is taken into consideration, the host material 133, like the host material 132, is preferably a material with a small energy difference between the singlet excitation energy level and the triplet excitation energy level, and particularly preferably a thermally activated, delayed fluorescent material.

[0102] In order to obtain light emission from the guest material 131 in an efficient manner, the singlet excitation energy level (S) A ) of the host material 133 preferably higher than or equal to the singlet excitation energy level (S H ) of host material 132 and is the triplet excitation energy level (T A ) of the host material 133 preferably higher than or equal to the triplet excitation energy level (T H ) of the host material 132.

[0103] According to the relationships between the LUMO levels and the HOMO levels described above, it is preferable that a reduction potential of the host material 133 is lower than a reduction potential of the host material 132 and that an oxidation potential of the host material 133 is higher than the oxidation potential of the guest material 131.

[0104] In the case where the combination of host material 132 and host material 133 is a combination of a material with a hole-transporting function and a material with an electron-transporting function, the charge carrier balance can be easily controlled depending on the mixing ratio. In particular, the ratio of the material with a hole-transporting function to the material with an electron-transporting function is preferably within a range of 1:9 to 9:1 (weight ratio). Since the charge carrier balance can be easily controlled by the structure, a charge carrier recombination range can also be easily controlled.

[0105] If the light-emitting layer 135 has the structure described above, light emission from the guest material 131 of the light-emitting layer 135 can be obtained efficiently. <material>

[0106] Next, the components of a light-emitting element of an embodiment of the present invention will be described in detail. <<Licht emittierende Schicht> >

[0107] In the light-emitting layer 130 and the light-emitting layer 135, the weight percent of the host material 132 is at least higher than that of the guest material 131, and the guest material 131 (the phosphorescent material) is dispersed in the host material 132. <<Wirtsmaterial 132> >

[0108] The energy difference between the S1 level and the T1 level of the host material 132 is preferably small, in particular greater than 0 eV and less than or equal to 0.2 eV.

[0109] The host material 132 preferably comprises a framework with hole transport properties and a framework with electron transport properties. Alternatively, the host material 132 preferably comprises a framework with a π-electron-deficient heteroaromatic ring, a framework with a π-electron-rich heteroaromatic ring, or an aromatic amine framework. Consequently, a donor-acceptor excitation state is readily formed in a molecule. Furthermore, a structure in which the framework with electron transport properties and the framework with hole transport properties are directly bonded to one another is preferably included in order to enhance both the donor and acceptor properties in the molecule of host material 132.Alternatively, a structure is preferably included in which a framework with a π-electron-deficient heteroaromatic ring is directly bonded to a framework with a π-electron-rich heteroaromatic ring or to an aromatic amine framework. By enhancing both the donor and acceptor properties in the molecule, the overlap between a region where the HOMO is distributed and a region where the LUMO is distributed in host material 132 can be small, and the energy difference between the singlet excitation energy level and the triplet excitation energy level of host material 132 can be small. Furthermore, the triplet excitation energy level of host material 132 can be kept high.

[0110] As an example of a material in which the energy difference between the triplet excitation energy level and the singlet excitation energy level is small, a thermally activated delayed fluorescent (TADF) material can be cited. It should be noted that a thermally activated delayed fluorescent material has the ability to convert triplet excitation energy to singlet excitation energy via reverse intersystem crossing, due to the small difference between the triplet and singlet excitation energy levels. Thus, the TADF material can, using a small amount of thermal energy, convert a triplet excitation state to a singlet excitation state (i.e., reverse intersystem crossing is possible) and efficiently emit light (fluorescence) from the singlet excitation state.The TADF material is efficiently obtained under the condition where the difference between the triplet excitation energy level and the singlet excitation energy level is preferably greater than 0 eV and less than or equal to 0.2 eV, more preferably greater than 0 eV and less than or equal to 0.1 eV.

[0111] In the case where the TADF material consists of one type of material, any of the following materials can be used, for example.

[0112] Firstly, a fullerene, a derivative thereof, or an acridine derivative, such as proflavin, eosin, and the like, can be identified. Furthermore, a metal-containing porphyrin, such as one containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd), can be identified. Examples of metal-containing porphyrin include a protoporphyrin tin fluoride complex (SnF2(Proto IX)), a mesoporphyrin tin fluoride complex (SnF2(Meso IX)), a hematoporphyrin tin fluoride complex (SnF2(Hämato IX)), a coproporphyrin tetramethyl ester tin fluoride complex (SnF2(Copro III-4Me)), an octaethylporphyrin tin fluoride complex (SnF2(OEP)), an etioporphyrin tin fluoride complex (SnF2(Etio I)) and an octaethylporphyrin platinum chloride complex (PtCl2OEP).

[0113] A heterocyclic compound comprising a π-electron-rich heteroaromatic ring and a π-electron-poor heteroaromatic ring can also be used as a TADF material consisting of one type of material. In particular, 2-(Biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 2-J4-[3-(N-Phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl)-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-Phenoxazine-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-Phenyl-5,10-dihydrophenazine-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-Dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), Bis[4-(9,9-dimethyl-9,10-dihydroacridin)phenyl]sulfone (abbreviation: DMAC-DPS) or 10-Phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (abbreviation: ACRSA) are used.The heterocyclic compound is preferably used because it has both the π-electron-rich heteroaromatic ring and the π-electron-deficient heteroaromatic ring; therefore, its electron transport and hole transport properties are high. Under frameworks with the π-electron-deficient heteroaromatic ring, a pyrimidine framework, a pyridazine framework, and a triazine framework exhibit high stability and reliability and are therefore used in the present invention. Under frameworks with the π-electron-rich heteroaromatic ring, an acridine framework, a phenoxazine framework, a phenothiazine framework, a furan framework, a thiophene framework, and a pyrrole framework exhibit high stability and reliability; consequently, at least one of these frameworks is preferably included. A dibenzofuran framework is preferable as the furan framework. A dibenzothiophene skeleton is preferable to a thiophene skeleton.An indole, carbazole, or 9-phenyl-3,3'-bi-9H-carbazole framework is particularly preferable as a pyrrole skeleton. It should be noted that a substance in which the π-electron-rich heteroaromatic ring is directly bonded to the π-electron-deficient heteroaromatic ring is especially preferred, since both the donor property of the π-electron-rich heteroaromatic ring and the acceptor property of the π-electron-deficient heteroaromatic ring are enhanced, and the difference between the singlet and triplet excitation levels becomes small. It should be noted that an aromatic ring to which an electron-withdrawing group, such as a cyano group, is bonded can be used instead of the π-electron-deficient heteroaromatic ring.

[0114] Among scaffolds with the π-electron-deficient heteroaromatic ring, a benzofuropyrimidine scaffold and a benzothienopyrimidine scaffold are particularly preferable because they exhibit higher acceptor properties. For example, a benzofuropyrimidine scaffold is given as a benzofuropyrimidine scaffold. For example, a benzothieno[3,2-d]pyrimidine scaffold is given as a benzothienopyrimidine scaffold. For example, a benzothieno[3,2-d]pyrimidine scaffold is given as a benzothienopyrimidine scaffold.

[0115] Among scaffolds with the π-electron-rich heteroaromatic ring, a bicarbazole scaffold is preferable because it exhibits high excitation energy, high stability, and high reliability. For example, a bicarbazole scaffold in which any 2- to 4-position of one carbazolyl group is bonded to any 2- to 4-position of another carbazolyl group is particularly preferred due to its high donor properties. Examples of such bicarbazole scaffolds include a 2,2'-Bi-9H-carbazole scaffold, a 3,3'-Bi-9H-carbazole scaffold, a 4,4'-Bi-9H-carbazole scaffold, a 2,3'-Bi-9H-carbazole scaffold, a 2,4'-Bi-9H-carbazole scaffold, a 3,4'-Bi-9H-carbazole scaffold, and the like.

[0116] With regard to increasing the band gap and triplet excitation energy, a compound is preferable in which the 9-position of one of the carbazolyl groups in the bicarbazole backbone is directly bonded to the benzofuropyrimidine or benzothienopyrimidine backbone. In the case where the bicarbazole backbone is directly bonded to the benzofuropyrimidine or benzothienopyrimidine backbone, a relatively low molecular weight compound is formed, and consequently, a structure suitable for vacuum evaporation (a structure that can be formed by vacuum evaporation at a relatively low temperature) is obtained, which is preferable. Generally, a lower molecular weight tends to decrease the heat resistance after film formation.However, a compound comprising the benzofuropyrimidine, benzothienopyrimidine, or bicarbazole scaffold can exhibit sufficient heat resistance even at a relatively low molecular weight due to its high rigidity. This structure is preferable because it increases the band gap and excitation energy level.

[0117] In the case where the bicarbazole framework is linked to the benzofuropyrimidine or benzothienopyrimidine framework via an arylene group with 6 to 25 carbon atoms, preferably with 6 to 13 carbon atoms, the band gap is kept large, and the triplet excitation energy can be maintained at a high level. Furthermore, a relatively low molecular weight compound is formed, and consequently, a structure suitable for vacuum evaporation (a structure that can be formed by vacuum evaporation at a relatively low temperature) is obtained.

[0118] In the case where a bicarbazole scaffold in a compound is directly or via an arylene group bonded to a benzofuro[3,2-d]pyrimidine scaffold or a benzothieno[3,2-d]pyrimidine scaffold, preferably to the 4-position of the benzofuro[3,2-d]pyrimidine scaffold or the benzothieno[3,2-d]pyrimidine scaffold, the compound exhibits high charge carrier transport properties. Accordingly, a light-emitting element in which the compound is used can be driven at a low voltage. < <Beispiel 1 für die Verbindung»

[0119] The compound described above, which is preferably used in a light-emitting element of an embodiment of the present invention, is a compound represented by the general formula (G0).

[0120] In the general formula (G0), A represents a substituted or unsubstituted benzofuropyrimidine framework or a substituted or unsubstituted benzothienopyrimidine framework. In cases where the benzofuropyrimidine framework or benzothienopyrimidine framework has a substituent, the substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group with 3 to 7 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.

[0121] Furthermore, R 1 to R 15 Each of these groups is independently defined as hydrogen, a substituted or unsubstituted alkyl group with 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 7 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group with 3 to 7 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.The aforementioned alkyl, cycloalkyl, and aryl groups can comprise one or more substituents, and the substituents can be bonded together to form a ring. The substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or an aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 7 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.

[0122] Furthermore, Ar 1 An arylene group can consist of 6 to 25 carbon atoms or a single bond. The arylene group can include one or more substituents, and the substituents can be bonded to each other to form a ring. For example, a carbon atom at the 9-position of a fluorenyl group has two phenyl groups as substituents, and the phenyl groups are bonded to form a spirofluorene framework. Specific examples of arylene groups with 6 to 25 carbon atoms include phenylene, naphthylene, biphenyldiyl, fluorendiyl, and the like. In cases where the arylene group has a single substituent, the substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or an aryl group with 6 to 13 carbon atoms.Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 7 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, fluorenyl, and the like.

[0123] In the compound represented by the general formula (G0), the benzofuropyrimidine skeleton is preferably a benzofuro[3,2-d]pyrimidine skeleton and the benzothienopyrimidine skeleton is preferably a benzothieno[3,2-d]pyrimidine skeleton.

[0124] The compound represented by the general formula (G0), in which the 9-position of one of the carbazolyl groups in the bicarbazole skeleton is bonded directly or via the arylene group to the 4-position of the benzofuro[3,2-d]pyrimidine skeleton or the benzothieno[3,2-d]pyrimidine skeleton, exhibits high donor properties, high acceptor properties, and a large band gap. Consequently, it can be used appropriately, and preferably, in a light-emitting element that emits high-energy light, such as blue light. The compound described above is represented by the general formula (G1).

[0125] In the general formula (G1), Q represents oxygen or sulfur.

[0126] Furthermore, R 1 to R 20 Each of these groups is independently defined as hydrogen, a substituted or unsubstituted alkyl group with 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 7 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group with 3 to 7 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.The aforementioned alkyl, cycloalkyl, and aryl groups can comprise one or more substituents, and the substituents can be bonded together to form a ring. The substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or an aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 7 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.

[0127] Furthermore, Ar 1 An arylene group can consist of 6 to 25 carbon atoms or a single bond. The arylene group can include one or more substituents, and the substituents can be bonded to each other to form a ring. For example, a carbon atom at the 9-position of a fluorenyl group has two phenyl groups as substituents, and the phenyl groups are bonded to form a spirofluorene framework. Specific examples of arylene groups with 6 to 25 carbon atoms include phenylene, naphthylene, biphenyldiyl, fluorendiyl, and the like. In cases where the arylene group has a single substituent, the substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or an aryl group with 6 to 13 carbon atoms.Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 7 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, fluorenyl, and the like.

[0128] The compound represented by general formula (G1), in which the bicarbazole framework is a 3,3'-Bi-9H-carbazole framework and the 9 position of one of the carbazolyl groups in the bicarbazole framework is directly or via the arylene group linked to the 4 position of the benzofuro[3,2-d]pyrimidine framework or the benzothieno[3,2-d]pyrimidine framework, exhibits high charge carrier transport properties, and a light-emitting element containing the compound can be driven at a low voltage, which is preferable. The compound described above is one represented by general formula (G2).

[0129] In the general formula (G2), Q represents oxygen or sulfur.

[0130] Furthermore, R 1 to R 20 Each of these groups is independently defined as hydrogen, a substituted or unsubstituted alkyl group with 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 7 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group with 3 to 7 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.The aforementioned alkyl, cycloalkyl, and aryl groups can comprise one or more substituents, and the substituents can be bonded together to form a ring. The substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or an aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 7 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.

[0131] Furthermore, Ar 1 A fluorenyl group can be an arylene group with 6 to 25 carbon atoms or a single bond. The arylene group can include one or more substituents, and the substituents can be bonded to each other to form a ring. For example, a carbon atom at the 9-position of a fluorenyl group has two phenyl groups as substituents, and the phenyl groups are bonded to form a spirofluorene framework. Specific examples of arylene groups with 6 to 13 carbon atoms include phenylene, naphthylene, biphenyldiyl, fluorendiyl, and the like. In cases where the arylene group has a substituent, the substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or another aryl group with 6 to 13 carbon atoms.Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 7 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, fluorenyl, and the like.

[0132] In the case where the bicarbazole scaffold is directly bonded to the benzofuropyrimidine scaffold or the benzothienopyrimidine scaffold in the compound represented by the general formula (G1) or (G2), the compound exhibits a larger band gap and can be synthesized with higher purity, which is preferable. Since the compound has excellent charge carrier transport properties, a light-emitting element containing the compound can be driven at a low voltage, which is also preferable.

[0133] In the case where R 1 to R 14 and R 16 to R 20 If hydrogen is represented in the general formula (G1) or (G2), the compound is advantageous in terms of simplicity of synthesis and material costs, and has a relatively low molecular weight suitable for vacuum evaporation, which is particularly preferable. The compound is one represented by the general formula (G3) or (G4).

[0134] In the general formula (G3), Q represents oxygen or sulfur.

[0135] Furthermore, R 15 Hydrogen, a substituted or unsubstituted alkyl group with 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 7 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group with 3 to 7 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.The aforementioned alkyl, cycloalkyl, and aryl groups can comprise one or more substituents, and the substituents can be bonded together to form a ring. The substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or an aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 7 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.

[0136] Furthermore, Ar 1 An arylene group can consist of 6 to 25 carbon atoms or a single bond. The arylene group can include one or more substituents, and the substituents can be bonded to each other to form a ring. For example, a carbon atom at the 9-position of a fluorenyl group has two phenyl groups as substituents, and the phenyl groups are bonded to form a spirofluorene framework. Specific examples of arylene groups with 6 to 25 carbon atoms include phenylene, naphthylene, biphenyldiyl, fluorendiyl, and the like. In cases where the arylene group has a single substituent, the substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or an aryl group with 6 to 13 carbon atoms.Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 7 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, fluorenyl, and the like.

[0137] In the general formula (G4), Q represents oxygen or sulfur.

[0138] Furthermore, R 15 Hydrogen, a substituted or unsubstituted alkyl group with 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 7 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group with 3 to 7 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.The aforementioned alkyl, cycloalkyl, and aryl groups can comprise one or more substituents, and the substituents can be bonded together to form a ring. The substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or an aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 7 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.

[0139] Furthermore, Ar 1 An arylene group can consist of 6 to 25 carbon atoms or a single bond. The arylene group can include one or more substituents, and the substituents can be bonded to each other to form a ring. For example, a carbon atom at the 9-position of a fluorenyl group has two phenyl groups as substituents, and the phenyl groups are bonded to form a spirofluorene framework. Specific examples of arylene groups with 6 to 25 carbon atoms include phenylene, naphthylene, biphenyldiyl, fluorendiyl, and the like. In cases where the arylene group has a single substituent, the substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or an aryl group with 6 to 13 carbon atoms.Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 7 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, fluorenyl, and the like.

[0140] For example, any of the structures represented by structural formulas (Ht-1) to (Ht-24) can be used as the benzofuropyrimidine scaffold or benzothienopyrimidine scaffold represented by A in the general formula (G0). It should be noted that a structure that can be used as A is not limited to these.

[0141] In the structural formulas (Ht-1) to (Ht-24) R 16 to R 20 Each of these is independently defined as hydrogen, a substituted or unsubstituted alkyl group with 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 7 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group with 3 to 7 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.The aforementioned alkyl, cycloalkyl, and aryl groups can comprise one or more substituents, and the substituents can be bonded together to form a ring. The substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or an aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 7 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.

[0142] Any of the structures represented by structural formulas (Cz-1) to (Cz-9) can be used as the bicarbazole scaffold in the general formulas (G0) and (G1). It should be noted that the structure that can be used as the bicarbazole scaffold is not limited to these.

[0143] In the structural formulas (Cz-1) to (Cz-9) R 1 to R 15 Each of these groups is independently defined as hydrogen, a substituted or unsubstituted alkyl group with 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 7 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group with 3 to 7 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.The aforementioned alkyl, cycloalkyl, and aryl groups can comprise one or more substituents, and the substituents can be bonded together to form a ring. The substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, or an aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 7 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.

[0144] As an arylene group, which is formed by Ar 1 In the general formulas (G0) to (G4), any of the groups represented by structural formulas (Ar-1) to (Ar-27) can be used, for example. It should be noted that the group used for Ar 1 can be used, is not limited to these, and can include a substituent.

[0145] For example, any of the groups represented by structural formulas (R-1) to (R-29) can be used for the alkyl group, the cycloalkyl group or the aryl group represented by R 1 to R 20 in the general formulas (G1) and (G2), R 1 to R 15 in the general formula (G0) and R 15 in the general formulas (G3) and (G4). It should be noted that the group, which can be used as an alkyl group, cycloalkyl group, or aryl group, is not limited to these and may include a substituent. <<Spezifische Beispiele für Verbindungen> >

[0146] Specific examples of the structures of the compounds represented by the general formulas (G0) to (G4) include compounds represented by structural formulas (100) to (147). It should be noted that the compounds represented by the general formulas (G0) to (G4) are not limited to the following examples. <<Beispiel 2 für die Verbindung> >

[0147] It should be noted that, although the host material 132 preferably has a small difference between the singlet excitation energy level and the triplet excitation energy level, the host material 132 does not necessarily have to have a high reverse intersystem crossing efficiency, a high luminescence quantum yield, or a function to provide a thermally activated luminescence quantum yield or a function to provide thermally activated delayed fluorescence. In this case, the host material 132 preferably has a structure in which a framework with the π-electron-deficient heteroaromatic ring and a framework with the π-electron-rich heteroaromatic ring and / or an aromatic amine framework are linked to one another via a structure comprising an m-phenylene group and / or an o-phenylene group. Alternatively, the frameworks are preferably linked to one another via a biphenyldiyl group.Alternatively, the host material 132 preferably has a structure in which the frameworks are linked to one another via an arylene group with an m-phenylene group and / or an o-phenylene group, and more preferably the arylene group is a biphenyldiyl group. The host material 132 with the structure described above can have a high T1 level. It should be noted that in this case, too, the framework with the π-electron-deficient heteroaromatic ring is provided to have a pyrimidine framework, a pyridazine framework, and / or a triazine framework. The framework with the π-electron-rich heteroaromatic ring preferably comprises an acridine framework, a phenoxazine framework, a phenothiazine framework, a furan framework, a thiophene framework, and / or a pyrrole framework. A dibenzofuran skeleton is preferable as a furan skeleton. A dibenzothiophene skeleton is preferable as a thiophene skeleton.For the pyrrole framework, an indole framework, a carbazole framework, or a 9-phenyl-3,3'-bi-9H-carbazole framework is particularly preferred. For the aromatic amine framework, a tertiary amine lacking an NH bond is preferred, and a triarylamine framework is especially preferred. For the aryl groups of the triarylamine framework, substituted or unsubstituted aryl groups with 6 to 13 carbon atoms forming rings are preferred, and examples include phenyl groups, naphthyl groups, and fluorenyl groups.

[0148] As examples of the aromatic amine framework described above and the framework with the π-electron-rich heteroaromatic ring, frameworks represented by general formulas (401) to (417) are given. It should be noted that X in general formulas (413) to (416) represents an oxygen atom or a sulfur atom.

[0149] As examples of the framework described above with the π-electron-deficient heteroaromatic ring, frameworks represented by the general formulas (201) to (218) are given.

[0150] In the case where a framework with a hole-transport property (e.g., the framework with the π-electron-rich heteroaromatic ring and / or the aromatic amine framework) and a framework with an electron-transport property (e.g., the framework with the π-electron-deficient heteroaromatic ring) are bonded to each other via a bonding group comprising the m-phenylene group and / or the o-phenylene group, via a biphenyldiyl group as a bonding group, or via a bonding group comprising an arylene group comprising the m-phenylene group and / or the o-phenylene group, examples of the bonding group include frameworks represented by the general formulas (301) to (315). Examples of the arylene group described above include a phenylene group, a biphenyldiyl group, a naphthalenediyl group, a fluorenediyl group, and a phenanthrenediyl group.

[0151] The aromatic amine framework described above (e.g. the triarylamine framework), the framework with the π-electron-rich heteroaromatic ring described above (e.g. a ring comprising the acridine framework, the phenoxazine framework, the phenothiazine framework, the furan framework, the thiophene framework and / or the pyrrole framework) and the framework with the π-electron-deficient heteroaromatic ring described above (e.g. a ring comprising the diazine framework and / or the triazine framework) or the general formulas (401) to (417), the general formulas (201) to (218) and the general formulas (301) to (315) may each contain a substituent. A substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 12 carbon atoms.Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. Specific examples of aryl groups with 6 to 12 carbon atoms include phenyl, naphthyl, biphenyl, and the like. The aforementioned substituents may be bonded to one another to form a ring. For example, when a carbon atom at the 9-position of a fluorene framework has two phenyl groups as substituents, the phenyl groups are bonded to form a spirofluorene framework.It should be noted that an unsubstituted group is advantageous in that it can be easily synthesized and its raw material is inexpensive.

[0152] Furthermore, Ar 2 This represents an arylene group with 6 to 13 carbon atoms. The arylene group can include one or more substituents, and the substituents can be bonded to each other to form a ring. For example, a carbon atom at the 9-position of a fluorenyl group has two phenyl groups as substituents, and the phenyl groups are bonded to form a spirofluorene framework. Specific examples of the 6- to 13-carbon arylene group include a phenylene group, a naphthylene group, a biphenyldiyl group, a fluorenediyl group, and the like. In the case where the arylene group has one substituent, the substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or an aryl group with 6 to 12 carbon atoms.Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. Specific examples of aryl groups with 6 to 12 carbon atoms include phenyl, naphthyl, biphenyl, and the like.

[0153] As an arylene group, which is formed by Ar 2 For example, the groups represented by the structural formulas (Ar-1) to (Ar-18) can be used. It should be noted that the groups representing Ar 2 can be used, but are not limited to these.

[0154] Furthermore, R 21 and R 22 Each of these groups independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.The preceding aryl or phenyl group can comprise one or more substituents, and the substituents can be bonded together to form a ring. The substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or an aryl group with 6 to 12 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like. Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. Specific examples of the aryl group with 6 to 12 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and the like.

[0155] For example, the groups represented by structural formulas (R-1) to (R-29) can be used as alkyl or aryl groups, represented by R 21 and R 22 can be represented. It should be noted that the group which can be used as an alkyl group or aryl group is not limited to this.

[0156] As a substituent, which appears in the general formulas (401) to (417), the general formulas (201) to (218), the general formulas (301) to (315), Ar 2 , R 21 and R 22 The group that can be used, for example, is the alkyl group or the aryl group represented by structural formulas (R-1) to (R-24). It should be noted that the group that can be used as an alkyl or aryl group is not limited to these.

[0157] Preferably, the host material 132 and the guest material 131 (the phosphorescent material) are selected such that the emission peak of the host material 132 overlaps with an absorption band, in particular with an absorption band on the longest wavelength side, of a triplet metal-to-ligand charge transfer (MLCT) transition of the guest material 131 (the phosphorescent material). This allows a light-emitting element with drastically improved emission efficiency to be provided. It should be noted that if a thermally activated, delayed-release fluorescent material is used instead of the phosphorescent material, the absorption band on the longest wavelength side is preferably a singlet absorption band. <<Gastmaterial 131> >

[0158] The guest material 131 (as phosphorescent material) can be an organometallic complex or a metal complex based on iridium, rhodium, or platinum; in particular, an organoiridium complex, such as an orthometallated complex based on iridium, is preferred. The orthometallated ligand can be a 4H-triazole ligand, a 1H-triazole ligand, an imidazole ligand, a pyridine ligand, a pyrimidine ligand, a pyrazine ligand, an isoquinoline ligand, or the like. The metal complex can be a platinum complex with a porphyrin ligand or the like.

[0159] Preferably, the host material 132 and the guest material 131 (the phosphorescent material) are selected such that the HOMO level of the guest material 131 (the phosphorescent material) is higher than the HOMO level of the host material 132, and that the energy difference between the LUMO level and the HOMO level of the guest material 131 (the phosphorescent material) is greater than the energy difference between the LUMO level and the HOMO level of the host material 132. With this structure, a light-emitting element with high emission efficiency and low drive voltage can be obtained.

[0160] Examples of the substance exhibiting an emission peak in the green or yellow wavelength range include organometallic iridium complexes with a pyrimidine framework, such as:Tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)3), Tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm)3), (Acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)2(acac)), (Acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm)2(acac)), (Acetylacetonato)bis[4-(2-norbornyl)-6-phenylpyrimidinato]iridium(III) (abbreviation: Ir(nbppm)2(acac)), (Acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: Ir(mpmppm)2(acac)), (Acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κ C}iridium(III) (abbreviation: Ir(dmppm-dmp)2(acac)) and (Acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: Ir(dppm)2(acac)); organometallic iridium complexes with a pyrazine framework, such as(Acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-Me)2(acac)) and (Acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-iPr)2(acac)); organometallic iridium complexes with a pyridine skeleton, such as Tris(2-phenylpyridinato-N,C. 2' )iridium(III) (abbreviation: Ir(ppy)3), Bis(2-phenylpyridinato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(ppy)2(acac)), Bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation: Ir(bzq)2(acac)), Tris(benzo[h]quinolinato)iridium(III) (abbreviation: Ir(bzq)3), Tris(2-phenylquinolinato-N,C 2' )iridium(III) (abbreviation: Ir(pq)3) and bis(2-phenylquinolinato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(pq)2(acac)); organometallic iridium complexes, such as bis(2,4-diphenyl-1,3-oxazolato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(dpo)2(acac)), Bis{2-[4'-(perfluorophenyl)phenyl]pyridinato-N,C 2'}iridium(III)acetylacetonate (abbreviation: Ir(p-PF-ph)2(acac)) and bis(2-phenylbenzothiazolato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(bt)2(acac)); and a rare-earth metal complex, such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: Tb(acac)3(Phen)). Among the materials mentioned above, the organometallic iridium complex with a pyrimidine framework exhibits very high reliability and very high emission efficiency and is therefore particularly preferred.

[0161] Examples of the substance exhibiting an emission peak in the yellow or red wavelength range include organometallic iridium complexes with a pyrimidine backbone, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: Ir(5mdppm)2(dibm)), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(5mdppm)2(dpm)) and bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(d1npm)2(dpm)); organometallic iridium complexes with a pyrazine backbone, such as... B. (Acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: Ir(tppr)2(acac)), Bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr)2(dpm)) and (Acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: Ir(Fdpq)2(acac)); organometallic iridium complexes with a pyridine skeleton, such as Tris(1-phenylisoquinolinato-N,C 2' )iridium(III) (abbreviation: Ir(piq)3) and bis(1-phenylisoquinolinato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(piq)2(acac)); a platinum complex, such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin-platinum(II) (abbreviation: PtOEP); and rare earth metal complexes, such as tris(1,3-diphenyl-1,3-propanediumato)(monophenanthroline)europium(III) (abbreviation: Eu(DBM)3(Phen)) and tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: Eu(TTA)3(Phen)). Among the materials mentioned above, the organometallic iridium complex with a pyrimidine framework exhibits very high reliability and very high emission efficiency and is therefore particularly preferred. Furthermore, the organometallic iridium complexes with pyrazine frameworks can provide red light emission with advantageous chromaticity.

[0162] Examples of the substance exhibiting an emission peak in the blue or green wavelength range include organometallic iridium complexes with a 4H-triazole framework, such as... B. Tris {2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}i iridium(III) (abbreviation: Ir(mpptz-dmp)3), Tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Mptz)3), Tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPrptz-3b)3) and Tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPr5btz)3); Organometallic iridium complexes with a 4H-triazole skeleton featuring an electron-withdrawing group, such as (OC-6-22)-Tris { 5-cyano-2-[4-(2,6-diisopropylphenyl)-5-(2-methylphenyl)-4H-1,2,4-triazole -3-yl-ĸN} 2 ]phenyl-ĸC}iridium(III) (Abbreviation: fac-Ir(mpCNptz-diPrp)3), (OC-6-21)-Tris{5-cyano-2-[4-(2,6-diisopropylphenyl)-5-(2-methylphenyl)-4H-1 ,2,4-triazol -3-yl-κN 2 ]phenyl-κC}iridium(III) (abbreviation: mer-Ir(mpCNptz-diPrp)3) and Tris{2-[4-(4-cyano-2,6-diisobutylphenyl)-5-(2-methylphenyl)-4H-1,2,4-triazol-3-yl-κN 2 ]phenyl-κC}iridium(III) (abbreviation: Ir(mpptz-diBuCNp)3); organometallic iridium complexes with a 1H-triazole skeleton, such as Tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(Mptz1-mp)3) and Tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Prptz1-Me)3); organometallic iridium complexes with an imidazole skeleton, such as... B. fac-Tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: Ir(iPrpmi)3) and Tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: Ir(dmpimpt-Me)3); and organometallic iridium complexes in which a phenylpyridine derivative with an electron-withdrawing group is a ligand, such as Bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2' ]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: Flr6), Bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2' ]iridium(III)picolinate (abbreviation: Flrpic), Bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C 2' } iridium(III)picolinate (abbreviation: Ir(CF3ppy)2(pic)) and Bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2' ]Iridium(III)acetylacetonate (abbreviation: Flr(acac)). Among the substances mentioned above, the organometallic iridium complexes comprising a nitrogen-containing five-membered heterocyclic framework, such as a 4H-triazole framework, a 1H-triazole framework, or an imidazole framework, exhibit high triplet excitation energy, high reliability, and high emission efficiency and are therefore particularly preferred.

[0163] The above-described organometallic iridium complexes, which have a nitrogen-containing five-membered heterocyclic framework, such as a 4H-triazole framework, a 1H-triazole framework and an imidazole framework, and the above-described iridium complexes which have a pyridine framework, have ligands with low electron acceptor properties and readily exhibit a high HOMO level; therefore, these complexes are suitable for an embodiment of the present invention.

[0164] Among the aforementioned organometallic iridium complexes having a nitrogen-containing five-membered heterocyclic framework, at least those iridium complexes containing a cyano group substituent can be suitable for use as the light-emitting element of an embodiment of the present invention, since they exhibit sufficiently reduced LUMO and HOMO levels due to the high electron-withdrawing property of the cyano group. Furthermore, a light-emitting element containing the iridium complex can emit blue light with high emission efficiency because the iridium complex has a high triplet excitation energy level. Since the iridium complex is very resistant to repeated oxidation and reduction, a light-emitting element containing the iridium complex can have a long service life.

[0165] It should be noted that, with regard to stability and reliability of the elemental properties, the iridium complex preferably comprises a ligand in which an aryl group is bonded to a cyano group on the nitrogen-containing five-membered heterocyclic framework, the number of carbon atoms of the aryl group preferably being 6 to 13. In this case, the iridium complex can be evaporated at a relatively low temperature in a vacuum, and thus deterioration due to pyrolysis or the like during evaporation is unlikely.

[0166] The iridium complex, comprising a ligand in which a cyano group is bonded via an arylene group to a nitrogen atom of a nitrogenous five-membered heterocyclic framework, can maintain a high triplet excitation energy level and is therefore preferably used in a light-emitting element that emits high-energy light, such as blue light. The light-emitting element containing the iridium complex can emit high-energy light, such as blue light, with higher efficiency than a light-emitting element that does not include a cyano group. Furthermore, a highly reliable light-emitting element that emits high-energy light, such as blue light, can be obtained by bonding a cyano group to a specific position, as described above.It should be noted that the nitrogen-containing five-membered heterocyclic skeleton and the cyano group are preferably bonded to each other via an arylene group, such as a phenylene group.

[0167] If the number of carbon atoms in the arylene group is 6 to 13, the iridium complex is a compound with a relatively low molecular weight, making it suitable for vacuum evaporation (allowing it to be evaporated at a relatively low temperature in a vacuum). Generally, a lower molecular weight compound tends to exhibit lower heat resistance after film formation. However, the iridium complex, even with its low molecular weight, has the following advantage: sufficient heat resistance can be ensured because the iridium complex comprises a variety of ligands.

[0168] This means that, in addition to ease of evaporation and electrochemical stability, the iridium complex possesses a characteristic namely a high triplet excitation energy level. Consequently, the iridium complex is preferably used as a guest material in a light-emitting layer of a light-emitting element in an embodiment of the present invention, particularly in a blue light-emitting element. <<Beispiele für den Iridiumkomplex> >

[0169] The iridium complex described above is represented by the general formula (G11).

[0170] In the general formula (G11) Ar 11 and Ar 12 Each of these is independently a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl. In the case where the aryl group has a substituent, the substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and n-hexyl. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group.

[0171] Q 1 and Q 2 Each independently represents N or CR, and R represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a haloalkyl group with 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Q 1 and / or Q 2 CR includes / includes. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. The haloalkyl group with 1 to 6 carbon atoms is an alkyl group in which at least one hydrogen atom is replaced by an element of Group 17 (fluorine, chlorine, bromine, iodine, or astatine). Examples of the haloalkyl group with 1 to 6 carbon atoms include an alkyl fluoride group, an alkyl chloride group, an alkyl bromide group, and an alkyl iodide group. Specific examples include a methyl fluoride group, a methyl chloride group, an ethyl fluoride group, and an ethyl chloride group. It should be noted that the number and types of halogen elements can be one, two, or more.Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl. The aryl group may have a substituent, and aryl substituents may be bonded together to form a ring. The substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or an aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and n-hexyl. Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group.

[0172] At least one of the aryl groups represented by Ar 11 and Ar 12 are represented, and / or the aryl group represented by R includes / includes a cyano group.

[0173] An iridium complex that can be advantageously used for a light-emitting element of an embodiment of the present invention is preferably an ortho-metallated complex. This iridium complex is represented by the general formula (G12).

[0174] In the general formula (G12) Ar represents 11 A 6-carbon aryl group is a substituted or unsubstituted group with 6 to 13 carbon atoms. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl. If the aryl group has a substituent, the substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and n-hexyl. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group.

[0175] R 31 to R 34 Each independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, a substituted or unsubstituted aryl group with 6 to 13 carbon atoms, or a cyano group. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group. The case in which R 31 to R 34 Since each of these are hydrogen, this is advantageous in terms of the simplicity of synthesis and material costs.

[0176] Q 1 and Q 2 Each independently represents N or CR, and R represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a haloalkyl group with 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Q 1 and / or Q 2 CR includes / includes. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. The haloalkyl group with 1 to 6 carbon atoms is an alkyl group in which at least one hydrogen atom is replaced by an element of Group 17 (fluorine, chlorine, bromine, iodine, or astatine). Examples of the haloalkyl group with 1 to 6 carbon atoms include an alkyl fluoride group, an alkyl chloride group, an alkyl bromide group, and an alkyl iodide group. Specific examples include a methyl fluoride group, a methyl chloride group, an ethyl fluoride group, and an ethyl chloride group. It should be noted that the number and types of halogen elements can be one, two, or more.Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl. The aryl group may have a substituent, and aryl substituents may be bonded together to form a ring. The substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or an aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and n-hexyl. Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group.

[0177] At least one of R 31 to R 34 and the aryl groups that are linked by Ar 11 , R 31 to R 34 and R, which is represented as a cyano group.

[0178] An iridium complex that can be advantageously used for a light-emitting element of an embodiment of the present invention comprises a 4H-triazole framework as a ligand, which is preferable because the iridium complex can have a high triplet excitation energy level and can be used appropriately in a light-emitting element that emits high-energy light, such as blue light. This iridium complex is represented by the general formula (G13).

[0179] In the general formula (G13), Ar represents 11 A 6-carbon aryl group is a substituted or unsubstituted group with 6 to 13 carbon atoms. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl. If the aryl group has a substituent, the substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and n-hexyl. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group.

[0180] R 31 to R 34 Each independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, a substituted or unsubstituted aryl group with 6 to 13 carbon atoms, or a cyano group. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group. The case in which R 31 to R 34 Since each of these are hydrogen, this is advantageous in terms of the simplicity of synthesis and material costs.

[0181] R 35 Represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a haloalkyl group with 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. The haloalkyl group with 1 to 6 carbon atoms is an alkyl group in which at least one hydrogen atom is replaced by an element from Group 17 (fluorine, chlorine, bromine, iodine, or astatine). Examples of the haloalkyl group with 1 to 6 carbon atoms include an alkyl fluoride group, an alkyl chloride group, an alkyl bromide group, and an alkyl iodide group. Specific examples include a methyl fluoride group, a methyl chloride group, an ethyl fluoride group, and an ethyl chloride group.It should be noted that the number and types of halogen elements can be one, two, or more. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl. The aryl group may have one substituent, and aryl substituents may be bonded together to form a ring. An alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or an aryl group with 6 to 13 carbon atoms can also be chosen as the substituent. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and n-hexyl.Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl.

[0182] At least one of R 31 to R 34 and the aryl groups that are linked by Ar 11 and R 31 to R 35 The representation includes a cyanogroup.

[0183] An iridium complex that can be advantageously used for a light-emitting element of an embodiment of the present invention comprises an imidazole framework as a ligand, which is preferable because the iridium complex can have a high triplet excitation energy level and can be used appropriately in a light-emitting element that emits high-energy light, such as blue light. This iridium complex is represented by the general formula (G14).

[0184] In the general formula (G14) Ar represents 11 A 6-carbon aryl group is a substituted or unsubstituted group with 6 to 13 carbon atoms. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl. If the aryl group has a substituent, the substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and n-hexyl. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group.

[0185] R 31 to R 34 Each independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group. The case in which R 31 to R 34 Since each of these are hydrogen, this is advantageous in terms of the simplicity of synthesis and material costs.

[0186] R 35 and R 36 Each of these terms independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a haloalkyl group with 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. The haloalkyl group with 1 to 6 carbon atoms is an alkyl group in which at least one hydrogen atom is replaced by an element from Group 17 (fluorine, chlorine, bromine, iodine, or astatine). Examples of the haloalkyl group with 1 to 6 carbon atoms include an alkyl fluoride group, an alkyl chloride group, an alkyl bromide group, and an alkyl iodide group. Specific examples include a methyl fluoride group, a methyl chloride group, an ethyl fluoride group, and an ethyl chloride group.It should be noted that the number and types of halogen elements can be one, two, or more. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl. The aryl group may have one substituent, and aryl substituents may be bonded together to form a ring. An alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or an aryl group with 6 to 13 carbon atoms can also be chosen as the substituent. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and n-hexyl.Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl.

[0187] At least one of R 31 to R 34 and the aryl groups that are linked by Ar 11 and R 31 to R 36 The representation includes a cyanogroup.

[0188] An iridium complex that can be advantageously used for a light-emitting element of an embodiment of the present invention comprises a nitrogen-containing five-membered heterocyclic framework, and an aryl group bonded to the nitrogen of the framework is preferably a substituted or unsubstituted phenyl group. In this case, the iridium complex can be evaporated in a vacuum at a relatively low temperature and exhibits a high triplet excitation energy level, and thus it can be used in a light-emitting element that emits high-energy light, such as blue light. The iridium complex is represented by the general formula (G15) or (G16).

[0189] In the general formula (G15) R 37 and R 41 each represents an alkyl group with 1 to 6 carbon atoms, and R 37 and R 41 They exhibit the same structure. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group.

[0190] R 38 to R 40 Each of these groups independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, a substituted or unsubstituted phenyl group, or a cyano group. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. It should be noted that at least one of R 38 to R 40 includes a cyanogroup.

[0191] R 31 to R 34 Each independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like. The case in which R 31 to R 34 Since each of these are hydrogen, this is advantageous in terms of the simplicity of synthesis and material costs.

[0192] R 33 Represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a haloalkyl group with 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. The haloalkyl group with 1 to 6 carbon atoms is an alkyl group in which at least one hydrogen atom is replaced by an element from Group 17 (fluorine, chlorine, bromine, iodine, or astatine). Examples of the haloalkyl group with 1 to 6 carbon atoms include an alkyl fluoride group, an alkyl chloride group, an alkyl bromide group, and an alkyl iodide group. Specific examples include a methyl fluoride group, a methyl chloride group, an ethyl fluoride group, and an ethyl chloride group.It should be noted that the number and types of halogen elements can be one, two, or more. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, fluorenyl, and the like. The aryl group may have a substituent, and aryl substituents may be bonded together to form a ring. An alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or an aryl group with 6 to 13 carbon atoms can also be chosen as the substituent. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like.Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, fluorenyl, and the like.

[0193] In the general formula (G16) R 37 and R 41 each represents an alkyl group with 1 to 6 carbon atoms, and R 37 and R 41 They exhibit the same structure. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like.

[0194] R 38 to R 40 Each of these groups independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, a substituted or unsubstituted phenyl group, or a cyano group. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. It should be noted that at least one of R 38 to R 40 preferably includes a cyano group.

[0195] R 31 to R 34 Each independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like. The case in which R 31 to R 34 Since each of these are hydrogen, this is advantageous in terms of the simplicity of synthesis and material costs.

[0196] R 35 and R 36 Each of these terms independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a haloalkyl group with 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. The haloalkyl group with 1 to 6 carbon atoms is an alkyl group in which at least one hydrogen atom is replaced by an element from Group 17 (fluorine, chlorine, bromine, iodine, or astatine). Examples of the haloalkyl group with 1 to 6 carbon atoms include an alkyl fluoride group, an alkyl chloride group, an alkyl bromide group, and an alkyl iodide group. Specific examples include a methyl fluoride group, a methyl chloride group, an ethyl fluoride group, and an ethyl chloride group.It should be noted that the number and types of halogen elements can be one, two, or more. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, fluorenyl, and the like. The aryl group may have a substituent, and aryl substituents may be bonded together to form a ring. An alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or an aryl group with 6 to 13 carbon atoms can also be chosen as the substituent. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like.Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, fluorenyl, and the like.

[0197] Iridium complexes that can be advantageously used for light-emitting elements of an embodiment of the present invention each comprise a 1H-triazole framework as a ligand, which is preferable because the iridium complexes can exhibit a high triplet excitation energy level and can be used appropriately for light-emitting elements that emit high-energy light, such as blue light. The iridium complexes are represented by the general formulas (G17) and (G18).

[0198] In the general formula (G17) Ar represents 11 A substituted or unsubstituted aryl group with 6 to 13 carbon atoms is represented. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, fluorenyl, and the like. If the aryl group has a substituent, the substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, n-hexyl, and the like.Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of an aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.

[0199] R 31 to R 34 Each independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group. The case in which R 31 to R 34 Since each of these are hydrogen, this is advantageous in terms of the simplicity of synthesis and material costs.

[0200] R 36 Represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a haloalkyl group with 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. The haloalkyl group with 1 to 6 carbon atoms is an alkyl group in which at least one hydrogen atom is replaced by an element from Group 17 (fluorine, chlorine, bromine, iodine, or astatine). Examples of the haloalkyl group with 1 to 6 carbon atoms include an alkyl fluoride group, an alkyl chloride group, an alkyl bromide group, and an alkyl iodide group. Specific examples include a methyl fluoride group, a methyl chloride group, an ethyl fluoride group, and an ethyl chloride group.It should be noted that the number and types of halogen elements can be one, two, or more. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl. The aryl group may have one substituent, and aryl substituents may be bonded together to form a ring. An alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or an aryl group with 6 to 13 carbon atoms can also be chosen as the substituent. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and n-hexyl.Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl.

[0201] At least one of R 31 to R 34 and the aryl groups that are linked by Ar 11 , R 31 to R 34 and R 36 The representation includes a cyanogroup.

[0202] In the general formula (G18) R 37 and R 41 each represents an alkyl group with 1 to 6 carbon atoms, and R 37 and R 41 They exhibit the same structure. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group.

[0203] R 38 to R 40 Each of these groups independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, a substituted or unsubstituted phenyl group, or a cyano group. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. It should be noted that at least one of R 38 to R 40 includes a cyanogroup.

[0204] R 31 to R 34 Each independently represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. Specific examples of a cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group. The case in which R 31 to R 34 Since each of these are hydrogen, this is advantageous in terms of the simplicity of synthesis and material costs.

[0205] R 36 Represents hydrogen, an alkyl group with 1 to 6 carbon atoms, a haloalkyl group with 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. The haloalkyl group with 1 to 6 carbon atoms is an alkyl group in which at least one hydrogen atom is replaced by an element from Group 17 (fluorine, chlorine, bromine, iodine, or astatine). Examples of the haloalkyl group with 1 to 6 carbon atoms include an alkyl fluoride group, an alkyl chloride group, an alkyl bromide group, and an alkyl iodide group. Specific examples include a methyl fluoride group, a methyl chloride group, an ethyl fluoride group, and an ethyl chloride group.It should be noted that the number and types of halogen elements can be one, two, or more. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl. The aryl group may have one substituent, and aryl substituents may be bonded together to form a ring. An alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or an aryl group with 6 to 13 carbon atoms can also be chosen as the substituent. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and n-hexyl.Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Specific examples of aryl groups with 6 to 13 carbon atoms include phenyl, naphthyl, biphenyl, and fluorenyl.

[0206] As alkyl group and aryl group, which are connected by R 31 to R 34 The groups represented by the structural formulas (R-1) to (R-29), for example, can be used in the general formulas (G12) to (G18). It should be noted that groups that can be used as alkyl and aryl groups are not limited to these.

[0207] For example, the groups represented by the structural formulas (R-12) to (R-29) can be described as an aryl group, represented by Ar 11 represented in the general formulas (G11) to (G14) and (G17), and used as an aryl group, which is represented by Ar 12 is represented in the general formula (G11). It should be noted that groups designated as Ar 11 and Ar 12 can be used, but are not limited to these groups.

[0208] For example, the groups represented by the structural formulas (R-1) to (R-10) can be used as alkyl groups represented by R 37 and R 41 They are represented in the general formulas (G15), (G16) and (G18). It should be noted that groups which can be used as alkyl groups are not limited to these groups.

[0209] As an alkyl group or as a substituted or unsubstituted phenyl group, which is represented by R 38 to R 40 The groups represented in the general formulas (G15), (G16) and (G18) can, for example, be those represented by the structural formulas (R-1) to (R-22) above. It should be noted that groups that can be used as alkyl or phenyl groups are not limited to these.

[0210] For example, groups represented by structural formulas (R-1) to (R-29) and structural formulas (R-30) to (R-37) can be used as alkyl groups, aryl groups and haloalkyl groups, respectively, represented by R 35 in the general formulas (G13) to (G16) and by R 36 in the general formulas (G14) and (G16) to (G18). It should be noted that a group which can be used as an alkyl group, aryl group or haloalkyl group is not limited to these groups. <<Spezifische Beispiele für Iridiumkomplexe> >

[0211] Specific examples of structures of the iridium complexes represented by the general formulas (G11) to (G18) are compounds represented by structural formulas (500) to (534). It should be noted that the iridium complexes represented by the general formulas (G11) to (G18) are not limited to the examples shown below.

[0212] The iridium complex described above by way of example has, as described above, relatively low HOMO and LUMO levels and is therefore preferred as a guest material of a light-emitting element in an embodiment of the present invention. In this case, the light-emitting element can have a high emission efficiency. Furthermore, the iridium complex described above by way of example has a high triplet excitation energy level and is therefore particularly preferred as a guest material of a blue light-emitting element. In this case, the blue light-emitting element can have a high emission efficiency. Moreover, since the iridium complex described above by way of example is very resistant to repeated oxidation and reduction, a light-emitting element containing the iridium complex can have a long operating lifetime.Therefore, the iridium complex of an embodiment of the present invention is a material that is used in a suitable manner in a light-emitting element.

[0213] Any material capable of converting triplet excitation energy into light emission can be used as the light-emitting material in light-emitting layer 130 and light-emitting layer 135. In addition to phosphorescent material, a thermally activated, delayed-release fluorescent material can be specified as an example of a material capable of converting triplet excitation energy into light emission. Therefore, the term "phosphorescent material" in the description can be replaced by the term "thermally activated, delayed-release fluorescent material". <<Wirtsmaterial 133> >

[0214] Preferably, the host material 133, the host material 132, and the guest material 131 are selected such that the LUMO level of the host material 133 is higher than the LUMO level of the host material 132, and that the HOMO level of the host material 133 is lower than the HOMO level of the guest material 131. With this structure, a light-emitting element with high emission efficiency and low drive voltage can be obtained. It should be noted that the material described as an example of the host material 132 can also be used as the host material 133.

[0215] A material that has the property of transporting more electrons than holes can be used as host material 133, wherein a material with an electron mobility of 1 × 10 -6 cm 2 / Vs or higher is preferable. A compound comprising a framework with a π-electron-deficient heteroaromatic ring, such as a nitrogen-containing heteroaromatic compound, or a zinc- or aluminum-based metal complex, can be used, for example, as a material that readily accepts electrons (as a material with electron transport properties). Specific examples include a metal complex with a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand; an oxadiazole derivative; a triazole derivative; a benzimidazole derivative; a quinoxaline derivative; a dibenzoquinoxaline derivative; a phenanthroline derivative; a pyridine derivative; a bipyridine derivative; a pyrimidine derivative; and a triazine derivative.

[0216] Specific examples include metal complexes with a quinoline or benzoquinoline skeleton, such as tris(8-quinolinolato)aluminium(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminium(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminium(III) (abbreviation: BAlq), and bis(8-quinolinolato)zinc(II) (abbreviation: Znq), and the like. A metal complex with an oxazole-based or thiazole-based ligand, such as... B. Bis[2-(2-benzoxazolyl)phenolate]zinc(II) (abbreviation: ZnPBO) or bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), can be used as an alternative. Besides such metal complexes, any of the following compounds can be used: heterocyclic compounds, such as...2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 9-[4-(4,5-Diphenyl-4H-1,2,4-triazol-3-yl)phenyl]-9H-carbazole (abbreviation: CzTAZ1), 2,2',2"-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), bathophenanthroline (abbreviation: BPhen) and bathocuproine (abbreviation: BCP); heterocyclic compounds with a diazine backbone, such as2-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(Dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-Carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4-(3,6-Diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II) 6-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 2-[3-(3,9'-Bi-9H-Carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzCzPDBq), 4,6-Bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-Bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II) and 4,6-Bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm); heterocyclic compounds with a triazine skeleton, such as... B.2-{4-[3-(N-Phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn); heterocyclic compounds with a pyridine backbone, such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy); and heteroaromatic compounds, such as 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs). Among the heterocyclic compounds, those with a triazine backbone, a diazine backbone (pyrimidine, pyrazine, pyridazine), and / or a pyridine backbone are very reliable and stable and are therefore preferred. Furthermore, the heterocyclic compounds with the frameworks exhibit high electron transport properties, contributing to a reduction in the drive voltage. A high-molecular-weight compound, such as...Poly(2,5-pyridindiyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), or poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)] (abbreviation: PF-BPy) can be used as a further alternative. The substances described here are mainly substances that have an electron mobility of 1 × 10⁻⁵. -6 cm 2 exhibiting / Vs or higher. It should be noted that other substances can also be used, as long as their electron transport properties are higher than their hole transport properties.

[0217] The following materials with hole transport properties can be used as host material 133.

[0218] A material that has the property of transporting more holes than electrons can be used as a hole transport material, where a material with a hole mobility of 1 × 10 -6 cm 2 / Vs or higher is preferable. In particular, an aromatic amine, a carbazole derivative, an aromatic hydrocarbon, a stilbene derivative, or the like can be used. Furthermore, the hole transport material can be a high-molecular-weight compound.

[0219] Examples of materials with high hole transport properties are N,N'-Di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4'-Bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N,N'-Bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD), 1,3,5-Tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B) and the like.

[0220] Specific examples of the carbazole derivative are 3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1), 3,6-Bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA2), 3,6-Bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole (abbreviation: PCzTPN2), 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-Bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), 3-[N-(1-Naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1) and the like.

[0221] Other examples of the carbazole derivative are 4,4'-Di(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3,5-Tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), 9-[4-(10-Phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA), 1,4-Bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene and the like.

[0222] Examples of aromatic hydrocarbons include 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9,10-di(1-naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene (abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene (abbreviation: DMNA). 2-tert-Butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene, 2,3,6,7-Tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9'-bianthryl, 10,10'-diphenyl-9,9'-bianthryl, 10,10'-bis(2-phenylphenyl)-9,9'-bianthryl, 10,10'-Bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bianthryl, anthracene, tetracene, rubrene, perylene, 2,5,8,11-Tetra(tert-butyl)perylene and the like. Pentacene, coronene, or similar compounds can also be used.The aromatic hydrocarbon, which has a hole mobility of 1 × 10. -6 cm 2 A material with a density of / Vs or higher and having 14 to 42 carbon atoms is particularly preferred.

[0223] The aromatic hydrocarbon may contain a vinyl skeleton. Examples of aromatic hydrocarbons with a vinyl group include: 4,4'-Bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi), 9,10-Bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA), and the like.

[0224] Furthermore, a high molecular weight compound, such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA) or poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: poly-TPD), can also be used.

[0225] Examples of materials with high hole transport properties include aromatic amine compounds, such as... B. 4,4'-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-Bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4',4''-Tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), 4,4',4''-Tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1'-TNATA), 4,4',4''-Tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4',4''-Tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), 4,4'-Bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-Phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-Phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), N-(9,9-Dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine (abbreviation: DFLADFL), N-(9,9-Dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine (abbreviation: DPNF), 2-[N-(4-Diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPASF), 4-Phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-Diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-Naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-Di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB) 4-Phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl)amine (abbreviation: PCA1BP), N,N'-Bis(9-phenylcarbazol-3-yl)-N,N'-diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N,N',N''-Triphenyl-N,N',N''-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine (abbreviation: PCA3B), N-(4-Biphenyl)-N-(9,9-Dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine (abbreviation: PCBiF), N-(1,1'-Biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), 9,9-Dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), N-Phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF), 2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), 2,7-Bis[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPA2SF), N-[4-(9H-carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline (abbreviation: YGA1BP) and N,N'-Bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F). Other examples include amine compounds, carbazole compounds, thiophene compounds, furan compounds, fluorene compounds, triphenylene compounds, phenanthrene compounds, and the like, such as 3-[4-(1-naphthyl)phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 3-[4-(9-phenanthryl)phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn), 3,3'-Bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 1,3-Bis(N-carbazolyl)benzene (abbreviation: mCP), 3,6-Bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3,6-Di(9H-carbazol-9-yl)-9-phenyl-9H-carbazole (abbreviation: PhCzGI), 2,8-Di(9H-carbazol-9-yl)-dibenzothiophene (abbreviation: Cz2DBT), 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II), 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 1,3,5-Tri(dibenzothiophene-4-yl)benzene (abbreviation: DBT3P-II), 2,8-Diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (Abbreviation: DBTFLP-III), 4-[4-(9-Phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV) and 4-[3-(Triphenylen-2-yl)phenyl]dibenzothiophene (abbreviation: mDBTPTp-II). Among the above compounds, those comprising a pyrrole framework, a furan framework, a thiophene framework and / or an aromatic amine framework are preferred due to their high stability and reliability. Furthermore, compounds with such frameworks exhibit high hole transport properties.to contribute to a reduction in the drive voltage.

[0226] Light-emitting layer 130 and light-emitting layer 135 can have a structure in which two or more layers are stacked on top of each other. For example, if light-emitting layer 130 or light-emitting layer 135 is formed by stacking a first light-emitting layer and a second light-emitting layer in that order, starting from the hole-transport layer side, the first light-emitting layer is formed using a material with hole-transport properties as the host material, and the second light-emitting layer is formed using a material with electron-transport properties as the host material.A light-emitting material contained in the first light-emitting layer can be the same as, or different from, a light-emitting material contained in the second light-emitting layer. Furthermore, the materials can have emission properties for emitting light of the same color or light of different colors. Two types of light-emitting materials with emission properties for different colors are used for the two light-emitting layers, so that light of a variety of emission colors can be obtained simultaneously. In particular, the light-emitting materials of the light-emitting layers are preferably selected such that white light can be obtained by combining the light emissions from the two light-emitting layers.

[0227] The light-emitting layer 130 can contain an additional material besides the host material 132 and the guest material 131. The light-emitting layer 135 can contain an additional material besides the host material 133, the host material 132, and the guest material 131.

[0228] It should be noted that the light-emitting layers 130 and 135 can be formed by an evaporation process (including a vacuum evaporation process), an inkjet process, a coating process, gravure printing, or the like. In addition to the materials mentioned above, an inorganic compound, such as a quantum dot, or a high-molecular-weight compound (e.g., an oligomer, a dendrimer, or a polymer) can be used. < <quantenpunkt>>

[0229] A quantum dot is a semiconductor nanocrystal with a size of several nanometers to several tens of nanometers, and it contains approximately 1 × 10 3 up to 1 × 10 6 Atoms. Since the energy shift of quantum dots depends on their size, quantum dots made of the same substance emit light with different wavelengths depending on their size; therefore, emission wavelengths can be easily regulated by changing the size of the quantum dots.

[0230] Since a quantum dot exhibits an emission spectrum with a narrow peak, emission with high color purity can be obtained. Furthermore, a quantum dot is thought to have a theoretical internal quantum efficiency of 100%, which far surpasses that of a fluorescent organic compound (i.e., 25%) and is comparable to that of a phosphorescent organic compound. Therefore, a quantum dot can be used as a light-emitting material to obtain a light-emitting element with high light emission efficiency. Moreover, a light-emitting element with advantageous lifetime characteristics can be obtained because a quantum dot, being an inorganic material, possesses high inherent stability.

[0231] Examples of quantum dot materials include a group 14 element, a group 15 element, a group 16 element, a compound of a variety of group 14 elements, a compound of an element belonging to one of groups 4 to 14 and a group 16 element, a compound of a group 2 element and a group 16 element, a compound of a group 13 element and a group 15 element, a compound of a group 13 element and a group 17 element, a compound of a group 14 element and a group 15 element, a compound of a group 11 element and a group 17 element, iron oxides, titanium oxides, spinel chalcogenides, and semiconductor clusters.

[0232] Specific examples include, but are not limited to, cadmium selenide, cadmium sulfide, cadmium telluride, zinc selenide, zinc oxide, zinc sulfide, zinc telluride, mercury sulfide, mercury selenide, mercury telluride, indium arsenide, indium phosphide, gallium arsenide, gallium phosphide, indium nitride, gallium nitride, indium antimonide, gallium antimonide, aluminum phosphide, aluminum arsenide, aluminum antimonide, lead selenide, lead telluride, lead sulfide, indium selenide, indium telluride, indium sulfide, gallium selenide, arsenic sulfide, arsenic selenide, arsenic telluride, antimony sulfide, antimony selenide, antimony telluride, bismuth sulfide, bismuth selenide, bismuth telluride, silicon, silicon carbide, germanium, tin, selenium. Tellurium, boron, carbon, phosphorus, boron nitride, boron phosphide, boron arsenide, aluminum nitride, aluminum sulfide, barium sulfide, barium selenide, barium telluride, calcium sulfide, calcium selenide, calcium telluride, beryllium sulfide, beryllium selenide, beryllium telluride, magnesium sulfide, magnesium selenide, germanium sulfide,Germanium selenide, germanium telluride, tin sulfide, tin selenide, tin telluride, lead oxide, copper fluoride, copper chloride, copper bromide, copper iodide, copper oxide, copper selenide, nickel oxide, cobalt oxide, cobalt sulfide, iron oxide, iron sulfide, manganese oxide, molybdenum sulfide, vanadium oxide, tungsten oxide, tantalum oxide, titanium oxide, zirconium oxide, silicon nitride, germanium nitride, aluminum oxide, barium titanate, a compound of selenium, zinc and cadmium, a compound of indium, arsenic and phosphorus, a compound of cadmium, selenium and sulfur, a compound of cadmium, selenium and tellurium, a compound of indium, gallium and arsenic, a compound of indium, gallium and selenium, a compound of indium, selenium and sulfur, a compound of copper, indium and sulfur, and combinations thereof. A so-called alloyed quantum dot, whose composition is represented by a given ratio, can be used. For example, an alloyed quantum dot made of cadmium,Selenium and sulfur are an effective means of obtaining blue light, since the emission wavelength can be changed by altering the composition ratio of the elements.

[0233] Any quantum dot can be a core-based quantum dot, a core-shell quantum dot, a core-multishell quantum dot, or the like. It should be noted that when a core is covered with a shell composed of a different inorganic material with a larger band gap, the influence of defects and free bonds present on the surface of a nanocrystal can be reduced. Since such a structure can greatly improve the quantum efficiency of light emission, a core-shell or core-multishell quantum dot is preferably used. Examples of shell materials include zinc sulfide and zinc oxide.

[0234] Quantum dots have a high proportion of surface atoms and, consequently, exhibit high reactivity and readily cohere with each other. For this reason, a protecting agent or protecting group is preferably applied to the surfaces of the quantum dots. Applying the protecting agent or providing the protecting group can prevent cohesion and increase solubility in a solvent. It can also reduce reactivity and improve electrical stability. Examples of the protecting agent (or protecting group) include polyoxyethylene alkyl ethers, such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; trialkyl phosphines, such as tripropyl phosphine, tributyl phosphine, trihexyl phosphine, and trioctyl phosphine; polyoxyethylene alkyl phenyl ethers, such as polyoxyethylene n-octyl phenyl ether and polyoxyethylene n-nonyl phenyl ether; and tertiary amines, such as...Tri(n-hexyl)amine, tri(n-octyl)amine, and tri(n-decyl)amine; organophosphorus compounds, such as tripropylphosphine oxide, tributylphosphine oxide, trihexylphosphine oxide, trioctylphosphine oxide, and tridecylphosphine oxide; polyethylene glycol diesters, such as polyethylene glycol dilaurate and polyethylene glycol distearate; organic nitrogen compounds, such as nitrogenous aromatic compounds, for example, pyridines, lutidines, collidines, and quinolones; aminoalkanes, such as hexylamine, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine; dialkyl sulfides, such as dibutyl sulfide; dialkyl sulfoxides, such as dimethyl sulfoxide and dibutyl sulfoxide; organic sulfur compounds, such as sulfur-containing aromatic compounds, for example, thiophene; higher fatty acids, such as...a palmitic acid, a stearic acid and an oleic acid; alcohols; sorbitan fatty acid esters; fatty acid-modified polyesters; tertiary amine-modified polyurethanes; and polyethyleneimines.

[0235] Since the band gaps of quantum dots increase with decreasing size, the size is regulated as needed to obtain light with a desired wavelength. Light emission from quantum dots shifts towards a blue color side, i.e., a high-energy side, as the crystal size decreases; consequently, the emission wavelengths of the quantum dots can be regulated across a wavelength range of the ultraviolet, visible, and infrared spectra by changing the size of the quantum dots. The size (diameter) range of the quantum dots typically used is from 0.5 nm to 20 nm, preferably from 1 nm to 10 nm. The emission spectra narrow with decreasing size distribution of the quantum dots, and consequently, light with high color purity can be obtained.The shape of quantum dots is not particularly restricted and can be spherical, rod-shaped, circular, or the like. Quantum rods, which are rod-shaped quantum dots, exhibit a function for emitting directional light; consequently, quantum rods can be used as a light-emitting material to obtain a light-emitting element with higher external quantum efficiency.

[0236] In most organic EL elements, the concentration quenching of the light-emitting materials is suppressed to improve emission efficiency by dispersing the light-emitting materials in host materials. These host materials must have singlet or triplet excitation energy levels higher than or equal to those of the light-emitting materials. When using blue phosphorescent materials as light-emitting materials, it is particularly difficult to develop host materials that possess triplet excitation energy levels higher than or equal to those of the blue phosphorescent materials and have excellent lifetimes.Even if a light-emitting layer consists of quantum dots and is formed without a host material, the quantum dots ensure emission efficiency; consequently, a light-emitting element with advantageous lifetime can be obtained. In the case where the light-emitting layer consists of quantum dots, the quantum dots preferably exhibit core-shell structures (including core-multishell structures).

[0237] In the case of using quantum dots as the light-emitting material in the light-emitting layer, the thickness of the light-emitting layer is adjusted to 3 nm to 100 nm, preferably 10 nm to 100 nm, and it is ensured that the light-emitting layer contains 1 vol.% to 100 vol.% quantum dots. It should be noted that it is preferable for the light-emitting layer to consist entirely of the quantum dots. To form a light-emitting layer in which the quantum dots are dispersed as light-emitting materials in host materials, the quantum dots can be dispersed in the host materials, or the host materials and the quantum dots can be dissolved or dispersed in a suitable liquid medium, and then a wet process (e.g.,A rotary coating process, a casting process, a nozzle coating process, a blade coating process, a roller coating process, an inkjet process, a printing process, a spray coating process, a curtain coating process, or a Langmuir-Blodgett process can be used. For a light-emitting layer containing a phosphorescent material, a vacuum evaporation process can be used in a suitable manner, as can the wet process.

[0238] An example of the liquid medium used for the wet process is an organic solvent consisting of ketones, such as methyl ethyl ketone and cyclohexanone, fatty acid esters, such as ethyl acetate, halogenated hydrocarbons, such as dichlorobenzene, aromatic hydrocarbons, such as toluene, xylene, mesitylene and cyclohexylbenzene, aliphatic hydrocarbons, such as cyclohexane, decalin and dodecane, dimethylformamide (DMF), dimethyl sulfoxide (DMSO) or the like. < <lochinjektionsschicht>>

[0239] The hole injection layer 111 has a function of reducing the barrier to hole injection from one electrode of the electrode pair (electrode 101 or electrode 102) to promote hole injection, and is formed, for example, using a transition metal oxide, a phthalocyanine derivative, or an aromatic amine. The transition metal oxide can be molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide, or the like. The phthalocyanine derivative can be phthalocyanine, metal phthalocyanine, or the like. The aromatic amine can be a benzidine derivative, a phenylenediamine derivative, or the like. It is also possible to use a high-molecular-weight compound, such as polythiophene or polyaniline; a typical example is poly(ethylenedioxythiophene) / poly(styrenesulfonic acid), which is self-doped polythiophene.

[0240] The hole injection layer 111 can also be a layer containing a composite material of a hole transport material and a material exhibiting the property of accepting electrons from the hole transport material. Alternatively, a layer arrangement consisting of a layer containing a material with electron-accepting properties and a layer containing a hole transport material can be used. In a stable state or in the presence of an electric field, electrical charges can be transferred between these materials. Examples of materials with electron-accepting properties include organic acceptors such as a quinodimethane derivative, a chloranil derivative, and a hexaazatriphenylene derivative. A specific example is a compound with an electron-withdrawing group (a halogen group or a cyano group), such as...7,7,8,8-Tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, or 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN). Alternatively, a transition metal oxide, such as an oxide of a metal from Groups 4 to 8, can be used. In particular, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, or the like can be used. Molybdenum oxide is especially preferred because it is stable in air, has low hygroscopic properties, and is easy to handle.

[0241] A material that has the property of transporting more holes than electrons can be used as a hole transport material, where a material with a hole mobility of 1 × 10 -6 cm 2 / Vs or higher is preferable. In particular, any of the aromatic amines, carbazole derivatives, aromatic hydrocarbons, stilbene derivatives, and the like, which have been described as examples of hole transport materials that can be used in the light-emitting layer, can be used. Furthermore, the hole transport material can be a high-molecular-weight compound. < <lochtransportschicht>>

[0242] The hole transport layer 112 is a layer containing a hole transport material and can be configured using any of the hole transport materials given as examples of the material for the hole injection layer 111. For the hole transport layer 112 to function as a transporter of holes injected into the hole injection layer 111 to the light-emitting layer, the highest occupied molecular orbital (HOMO) level of the hole transport layer 112 is preferably equal to or close to the HOMO level of the hole injection layer 111.

[0243] Preferably, a substance with a hole mobility of 1 × 10⁻⁵ is used. -6 cm 2 / Vs or higher is used as a hole transport material. It should be noted that, apart from these substances, any substance with the property of transporting more holes than electrons can be used. The layer containing a substance with high hole transport properties is not limited to a single layer and can comprise two or more stacked layers containing the aforementioned substances. < <elektronentransportschicht>>

[0244] The electron transport layer 118 has the function of transporting electrons injected from the other electrode of the electrode pair (electrode 101 or electrode 102) via the electron injection layer 119 to the light-emitting layer. A material exhibiting the property of transporting more electrons than holes can be used as the electron transport material, with a material having an electron mobility of 1 × 10 -6 cm 2 A material with an electron mobility of 1 × 10⁻⁶ Vs or higher is preferable. A π-electron-deficient heteroaromatic compound, such as a nitrogen-containing heteroaromatic compound, a metal complex, or the like, can be used as a compound that readily accepts electrons (as a material with electron transport properties). In particular, a metal complex with a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand, which have been described as electron transport materials suitable for use in the light-emitting layer, can be specified. Furthermore, an oxadiazole derivative, a triazole derivative, a benzimidazole derivative, a quinoxaline derivative, a dibenzoquinoxaline derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, or a triazine derivative can be specified. A substance with an electron mobility of 1 × 10⁻⁶ Vs or higher is also suitable. -6 cm 2 / Vs is preferred. It should be noted that, apart from the substances mentioned above, any substance may be used as long as it has a higher electron transport property than its hole transport property. The electron transport layer 118 is not limited to a single layer and may comprise two or more superimposed layers containing the aforementioned substances.

[0245] A layer controlling the transport of electron charge carriers can be provided between the electron transport layer 118 and the light-emitting layer. This layer is formed by adding a small amount of a substance with high electron-capture properties to a previously described material with high electron transport properties, and the layer can regulate the charge carrier balance by suppressing the movement of electron charge carriers. Such a structure is very effective in preventing a problem (such as a reduction in the lifetime of the element) that arises when electrons pass through the light-emitting layer.

[0246] An n-type compound semiconductor can also be used, and for example an oxide, such as titanium oxide, zinc oxide, silicon oxide, tin oxide, tungsten oxide, tantalum oxide, barium titanate, barium zirconate, zirconium oxide, hafnium oxide, aluminum oxide, yttrium oxide or zirconium silicate, or a nitride, such as silicon nitride, cadmium sulfide, zinc selenide or zinc sulfide, can be used. < <elektroneninjektionsschicht>>

[0247] The electron injection layer 119 has a function for reducing the barrier to electron injection from the electrode 102 in order to promote electron injection, and can, for example, be formed using a metal of group 1 or a metal of group 2, or an oxide, halide, or carbonate of any of the metals. Alternatively, a composite material can be used that includes an electron transport material (described above) and a material that has the property of donating electrons to the electron transport material. A metal of group 1, a metal of group 2, an oxide of any of the metals, or the like can be specified as a material with an electron-donating property. In particular, an alkali metal, an alkaline earth metal, or a compound thereof, such as...Lithium fluoride, sodium fluoride, cesium fluoride, calcium fluoride, or lithium oxide can be used. A rare-earth metal compound such as erbium fluoride can be used alternatively. An electride can also be used for the electron injection layer 119. Examples of electrides include substances in which electrons are added to calcium oxide-aluminum oxide in a high concentration. The electron injection layer 119 can be formed using the same substance that can be used for the electron transport layer 118.

[0248] A composite material in which an organic compound and an electron donor (donor) are mixed can also be used for the electron injection layer 119. Such a composite material exhibits excellent electron injection and electron transport properties, since electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material that can transport the generated electrons excellently. In particular, the substances listed above (e.g., the metal complexes and the heteroaromatic compounds) can be used to form the electron transport layer 118. A substance that has the property of donating electrons to the organic compound can be used as the electron donor.In particular, an alkali metal, an alkaline earth metal, and a rare earth metal are preferred, and lithium, sodium, cesium, magnesium, calcium, erbium, and ytterbium are specified. Furthermore, an alkali metal oxide or an alkaline earth metal oxide is preferred, and lithium oxide, calcium oxide, barium oxide, and the like are specified. A Lewis base, such as magnesium oxide, may also be used. An organic compound, such as tetrathiafulvalene (abbreviation: TTF), may also be used.

[0249] It should be noted that the light-emitting layer, the hole injection layer, the hole transport layer, the electron transport layer, and the electron injection layer described above can each be formed by an evaporation process (including a vacuum evaporation process), an inkjet process, a coating process, a gravure printing process, or the like. In addition to the materials mentioned above, an inorganic compound, such as a quantum dot, or a high-molecular-weight compound (e.g., an oligomer, a dendrimer, and a polymer) can be used in the light-emitting layer, the hole injection layer, the hole transport layer, the electron transport layer, and the electron injection layer. <<Paar von Elektroden> >

[0250] Electrodes 101 and 102 serve as the anode and cathode of each light-emitting element. Electrodes 101 and 102 can be formed using a metal, an alloy, a conductive compound, a mixture, or a layered arrangement of these or the like.

[0251] Either electrode 101 or electrode 102 is preferably designed using a conductive material with a light-reflecting function. Examples of the conductive material include aluminum (Al), an alloy containing Al, and the like. Examples of the alloy containing Al include an alloy containing Al and L (where L represents one or more of titanium (Ti), neodymium (Nd), nickel (Ni), and lanthanum (La)), such as an alloy containing Al and Ti, and an alloy containing Al, Ni, and La. Aluminum has low resistance and high light reflectivity. Aluminum is abundant in the Earth's crust and is inexpensive; therefore, it is possible to reduce the cost of manufacturing a light-emitting element using aluminum.Alternatively, silver (Ag), an alloy of Ag and N (where N represents one or more of yttrium (Y), Nd, magnesium (Mg), ytterbium (Yb), Al, Ti, gallium (Ga), zinc (Zn), indium (In), tungsten (W), manganese (Mn), tin (Sn), iron (Fe), Ni, copper (Cu), palladium (Pd), iridium (Ir), and gold (Au)), or the like may be used. Examples of silver-containing alloys include an alloy containing silver, palladium, and copper; an alloy containing silver and copper; an alloy containing silver and magnesium; an alloy containing silver and nickel; an alloy containing silver and gold; an alloy containing silver and ytterbium; and the like. In addition, a transition metal, such as tungsten, chromium (Cr), molybdenum (Mo), copper, or titanium, may be used.

[0252] Light emitted by the light-emitting layer is extracted via electrode 101 and / or electrode 102. Accordingly, electrode 101 and / or electrode 102 are preferably designed using a conductive material with a light-transmitting function. The conductive material can be one that has a visible light transmittance of 40% or higher and 100% or lower, preferably 60% or higher and 100% or lower, and a resistivity of 1 × 10⁻⁶ or lower. -2 exhibits Ω·cm.

[0253] Electrodes 101 and 102 can each be configured using a conductive material with properties for transmitting and reflecting light. The conductive material can be one that has a visible light reflectance of 20% or higher and 80% or lower, preferably 40% or higher and 70% or lower, and a resistivity of 1 × 10⁻⁶ Ω or lower. -2 Ω·cm. For example, one or more types of conductive metals and alloys, conductive compounds, and the like may be used. In particular, a metal oxide such as indium tin oxide (hereinafter referred to as ITO), silicon- or silicon-oxide-containing indium tin oxide (ITSO), indium zinc oxide, titanium-containing indium tin oxide, indium titanium oxide, or tungsten oxide and zinc oxide-containing indium oxide may be used. A thin metal film with a thickness that allows the transmission of light (preferably a thickness greater than or equal to 1 nm and less than or equal to 30 nm) may also be used. The metal may be Ag, an alloy of Ag and Al, an alloy of Ag and Mg, an alloy of Ag and Au, an alloy of Ag and Yb, or the like.

[0254] In this description and similar texts, the term "transmitting material" refers to a material that transmits visible light and exhibits conductivity. Examples of such a material include, in addition to the oxide conductor described above, which is typically ITO, an oxide semiconductor and an organic conductor containing an organic substance. Examples of the organic conductor containing an organic substance include a composite material in which an organic compound and an electron donor (donor material) are blended, and a composite material in which an organic compound and an electron acceptor (acceptor material) are blended. Alternatively, an inorganic, carbon-based material, such as graphene, may be used. The resistivity of the material is preferably less than or equal to 1 × 10⁻⁶. 5 Ω·cm, preferably lower than or equal to 1 × 10 4 Ω·cm.

[0255] Alternatively, electrode 101 and / or electrode 102 can be formed by arranging two or more of these materials on top of each other.

[0256] To improve light extraction efficiency, a material with a higher refractive index than that of a transmitting electrode can be formed in contact with the electrode. The material can be electrically conductive or non-conductive, as long as it transmits visible light. In addition to the oxide conductors described above, an oxide semiconductor and an organic substance are given as examples of such materials. Examples of organic substances include materials for the light-emitting layer, the hole injection layer, the hole transport layer, the electron transport layer, and the electron injection layer. Alternatively, an inorganic, carbon-based material or a metal film thin enough to transmit light can be used.As another alternative, several layers, each formed using the material with a high refractive index and having a thickness of several nanometers to several tens of nanometers, can be arranged on top of each other.

[0257] In the case where electrode 101 or electrode 102 serves as the cathode, the electrode preferably contains a material with a low work function (less than or equal to 3.8 eV). Examples include an element belonging to Group 1 or 2 of the periodic table (e.g., an alkali metal such as lithium, sodium, or cesium; an alkaline earth metal such as calcium or strontium; or magnesium); an alloy containing any of these elements (e.g., Ag-Mg or Al-Li); a rare earth metal such as europium (Eu) or Yb; an alloy containing any of these rare earth metals; an alloy containing aluminum and silver; and the like.

[0258] If electrode 101 or electrode 102 is used as the anode, a material with a high work function (4.0 eV or higher) is preferably used.

[0259] Electrode 101 and electrode 102 can be layered arrangements consisting of a conductive material with a light-reflecting function and a conductive material with a light-transmitting function. In this case, electrode 101 and electrode 102 can have a function for regulating the optical path length, so that light of a desired wavelength emitted by each light-emitting layer oscillates and is amplified, which is preferable.

[0260] Depending on requirements, a sputtering process, an evaporation process, a printing process, a coating process, a molecular beam epitaxy (MBE) process, a CVD process, a pulsed laser deposition process, an atomic layer deposition (ALD) process or the like can be used as a method for forming the electrode 101 and the electrode 102. < <substrat>>

[0261] A light-emitting element of an embodiment of the present invention can be formed on a substrate made of glass, plastic, or the like. As one possibility for arranging layers on top of each other on the substrate, layers can be arranged successively from the side of electrode 101 or successively from the side of electrode 102.

[0262] For the substrate on which the light-emitting element of an embodiment of the present invention can be formed, glass, quartz, plastic, or the like can be used, for example. Alternatively, a flexible substrate can be used. The flexible substrate means, for example, a substrate that can be bent, such as a plastic substrate made of polycarbonate or polyarylate. Alternatively, a film, an inorganic film deposited by evaporation, or the like can be used. Another material can be used as long as the substrate serves as a support in a manufacturing process of the light-emitting element or an optical element, or as long as it has a function of protecting the light-emitting element or an optical element.

[0263] In this description and similar examples, a light-emitting element can be formed using any number of different substrates. The type of substrate is not particularly limited. Examples of substrates include a semiconductor substrate (e.g., a single-crystal substrate or a silicon substrate), an SOI substrate, a glass substrate, a quartz substrate, a plastic substrate, a metal substrate, a stainless steel substrate, a substrate containing a stainless steel foil, a tungsten substrate, a substrate containing a tungsten foil, a flexible substrate, a mounting film, paper containing a fiber material, a base material film, and the like. Examples of glass substrates include a barium borosilicate glass substrate, an aluminum borosilicate glass substrate, a soda-lime glass substrate, and the like.Examples of flexible substrates, mounting films, base material films, and the like include plastic substrates typically made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). Another example is a resin, such as acrylic. Polypropylene, polyester, polyvinyl fluoride, and polyvinyl chloride can also be cited as examples. Further examples include polyamide, polyimide, aramid, epoxy, an evaporation-deposited inorganic film, paper, and the like.

[0264] Alternatively, a flexible substrate can be used such that the light-emitting element is placed directly on the flexible substrate. Another alternative is to provide a separating layer between the substrate and the light-emitting element. The separating layer can be used when part or all of the light-emitting element formed above the separating layer is separated from the substrate and transferred to another substrate. In such a case, the light-emitting element can also be transferred to a substrate with low heat resistance or to a flexible substrate. For the separating layer described above, for example, a layer arrangement including inorganic films, namely a tungsten film and a silicon oxide film, or a structure in which a resin film of polyimide or the like is formed over a substrate can be used.

[0265] In other words, once the light-emitting element has been formed using a substrate, it can be transferred to another substrate. Examples of substrates onto which the light-emitting element can be transferred, in addition to those mentioned above, include cellophane, rock, wood, fabric (including natural fibers such as silk, cotton, or hemp; synthetic fibers such as nylon, polyurethane, or polyester; regenerated fibers such as acetate, cupro, viscose, or regenerated polyester); leather; rubber; and the like. Using such a substrate allows for the creation of a light-emitting element with high durability, high heat resistance, reduced weight, or reduced thickness.

[0266] The light-emitting element 150 can, for example, be formed over an electrode that is electrically connected to a field-effect transistor (FET) formed over any of the substrates described above. In this way, an active-matrix display device can be produced in which the FET controls the operation of the light-emitting element 150.

[0267] In embodiment 1, one embodiment of the present invention has been described. Further embodiments of the present invention are described in embodiments 2 to 9. It should be noted that an embodiment of the present invention is not limited to these. That is to say, an embodiment of the present invention is not limited to a specific embodiment, since various embodiments of the present invention are disclosed in embodiment 1 and embodiments 2 to 9. Although the example described involves the use of an embodiment of the present invention with a light-emitting element, an embodiment of the present invention is not limited to this. For example, depending on the circumstances or conditions, an embodiment of the present invention is not necessarily used with a light-emitting element.One embodiment of the present invention shows, but is not limited to, an example in which a guest material suitable for converting triplet excitation energy into light emission and at least one host material are included, wherein the HOMO level of the guest material is higher than the HOMO level of the host material, and the energy difference between the LUMO level and the HOMO level of the guest material is greater than the energy difference between the LUMO level and the HOMO level of the host material. Depending on the circumstances or conditions, the guest material of an embodiment of the present invention does not necessarily have a function for converting the triplet excitation energy into light emission. Alternatively, the HOMO level of the guest material is not necessarily higher than the HOMO level of the host material.Alternatively, the energy difference between the LUMO level and the HOMO level of the guest material is not necessarily greater than the energy difference between the LUMO level and the HOMO level of the host material. One embodiment of the present invention shows, but is not limited to, an example in which the host material has a difference of greater than 0 eV and less than or equal to 0.2 eV between the singlet excitation energy level and the triplet excitation energy level. Depending on the circumstances or conditions, the host material of an embodiment of the present invention, for example, does not necessarily have a difference of greater than 0.2 eV between the singlet excitation energy level and the triplet excitation energy level.

[0268] The structure described above for this embodiment can optionally be combined with any of the structures described for the other embodiments. (Version 2)

[0269] In this embodiment, a light-emitting element with a structure that differs from that described in embodiment 1, and light-emission mechanisms of the light-emitting element are described below based on Fig. 5A to Fig. 5C and Fig. 6A to Fig. 6C described. In Fig. 5A and Fig. In some cases, section 6A has a similar function to the one in Fig. 1A through the same hatching pattern as in Fig. Sections 1A are shown without a separate reference symbol. Furthermore, common reference symbols are used for sections with similar functions, and a detailed description of the sections is omitted in some cases. <Strukturbeispiel 1 des Licht emittierenden Elements>

[0270] Fig. 5A is a schematic cross-sectional view of a light-emitting element 250.

[0271] The light-emitting element 250, which is in Fig. 5A, as shown, includes a variety of light-emitting units (one light-emitting unit 106 and one light-emitting unit 108 in Fig. 5A) between a pair of electrodes (electrode 101 and electrode 102). One of the light-emitting units preferably has the same structure as the EL layer 100. That is to say: Preferably, both the light-emitting element 150 in Fig. 1A and Fig. 1B as well as the light-emitting element 152 in Fig. 3A and Fig. 3B is a light-emitting unit, whereas the light-emitting element 250 comprises a plurality of light-emitting units. It should be noted that in the following description of the light-emitting element 250, electrode 101 and electrode 102 serve as the anode and cathode, respectively; however, these functions can be interchanged in the light-emitting element 250.

[0272] The light-emitting element 250, which is in Fig. As shown in Figure 5A, the light-emitting unit 106 and the light-emitting unit 108 are arranged one above the other, and a charge-generating layer 115 is provided between the light-emitting unit 106 and the light-emitting unit 108. It should be noted that the light-emitting unit 106 and the light-emitting unit 108 can have the same structure or different structures. For example, the EL layer 100 is preferably used in the light-emitting unit 106.

[0273] The light-emitting element 250 comprises a light-emitting layer 120 and a light-emitting layer 170. The light-emitting unit 106 comprises, in addition to the light-emitting layer 170, the hole injection layer 111, the hole transport layer 112, an electron transport layer 113, and an electron injection layer 114. The light-emitting unit 108 comprises, in addition to the light-emitting layer 120, a hole injection layer 116, a hole transport layer 117, an electron transport layer 118, and an electron injection layer 119.

[0274] The charge-generating layer 115 can either have a structure in which an acceptor substance, which is an electron acceptor, is added to a hole transport material, or a structure in which a donor substance, which is an electron donor, is added to an electron transport material. Alternatively, both of these structures can be arranged one above the other.

[0275] In the case where the charge-generating layer 115 contains a composite material of an organic compound and an acceptor substance, the composite material that can be used for the hole injection layer 111 described in embodiment 1 can be used as the composite material. Various compounds can be used as the organic compound, such as an aromatic amine compound, a carbazole compound, an aromatic hydrocarbon, and a high-molecular-weight compound (such as an oligomer, a dendrimer, or a polymer). A material with a hole mobility of 1 × 10 -6 cm 2 A voltage of / Vs or higher is preferably used as an organic compound. It should be noted that another material may be used as long as it has the property of transporting more holes than electrons. Since the composite material of an organic compound and an acceptor substance exhibits excellent charge carrier injection and charge carrier transport properties, operation at low voltage or low current can be achieved. It should be noted that if a surface of a light-emitting unit on the anode side is in contact with the charge-generating layer 115, the charge-generating layer 115 can also serve as a hole injection layer or hole transport layer of the light-emitting unit; therefore, a hole injection layer or a hole transport layer need not necessarily be included in the light-emitting unit.If a surface of a light-emitting unit on the cathode side is in contact with the charge-generating layer 115, the charge-generating layer 115 can also serve as an electron injection layer or electron transport layer of the light-emitting unit; therefore, an electron injection layer or an electron transport layer does not necessarily have to be included in the light-emitting unit.

[0276] The charge-generating layer 115 can have a multilayer structure consisting of a layer containing the composite material of an organic compound and an acceptor substance, and a layer containing another material. For example, the charge-generating layer 115 can be formed using a combination of a layer containing the composite material of an organic compound and an acceptor substance with a layer containing a compound selected from electron-donating materials and a compound with high electron transport properties. Furthermore, the charge-generating layer 115 can be formed using a combination of a layer containing the composite material of an organic compound and an acceptor substance with a layer containing a transparent conductive film.

[0277] The charge-generating layer 115, provided between the light-emitting unit 106 and the light-emitting unit 108, can have any structure as long as electrons can be injected into the light-emitting unit on one side and holes can be injected into the light-emitting unit on the other side when a voltage is applied between electrode 101 and electrode 102. For example, injected into Fig. 5A the charge-generating layer 115 electrons into the light-emitting unit 106 and holes into the light-emitting unit 108 when a voltage is applied such that the potential of electrode 101 is higher than that of electrode 102.

[0278] It should be noted that, with regard to light extraction efficiency, the charge-generating layer 115 preferably has a visible light transmittance (in particular, a visible light transmittance of 40% or higher). The charge-generating layer 115 functions even if it has a lower conductivity than the pair of electrodes (electrodes 101 and 102).

[0279] It should be noted that forming the charge-generating layer 115 using any of the above materials can suppress an increase in the drive voltage caused by the layer arrangement of the light-emitting layers.

[0280] The light-emitting element with two light-emitting units is defined by Fig. 5A has been described; however, a similar structure can be applied to a light-emitting element in which three or more light-emitting units are arranged one above the other. With a plurality of light-emitting units separated by the charge-generating layer between a pair of electrodes, a light-emitting element can be provided, just as with the light-emitting element 250, that can emit light with high luminance while keeping the current density low and exhibiting a long lifetime. A low-power light-emitting element can be provided.

[0281] If the structure described in embodiment 1 is used for at least one of the plurality of units, a light-emitting element with high emission efficiency can be provided.

[0282] Preferably, the light-emitting layer 170 of the light-emitting unit 106 has the structure of the light-emitting layer 130 or the light-emitting layer 135 described in embodiment 1, wherein in this case the light-emitting element 250 has a sufficiently high emission efficiency.

[0283] The light-emitting layer 120, which is contained in the light-emitting unit 108, contains a guest material 121 and a host material 122, as shown in Fig. 5B is shown. It should be noted that the guest material 121 is subsequently described as a fluorescent material. <<Lichtemissionsmechanismus der Licht emittierenden Schicht 120> >

[0284] The following describes the light emission mechanism of the light-emitting layer 120.

[0285] Excitons are formed when the electrons and holes injected from the pair of electrodes (electrode 101 and electrode 102) or the charge-generating layer recombine in the light-emitting layer 120. Since the amount of host material 122 is greater than that of guest material 121, the host material 122 is excited by the exciton generation.

[0286] It should be noted that the term "exciton" refers to a charge carrier (electron and hole) pair. Since excitons possess energy, a material in which excitons are generated is brought into an excited state.

[0287] In the case where the excitation state formed of the host material 122 is a singlet excitation state, the singlet excitation energy is transferred from the S1 level of the host material 122 to the S1 level of the guest material 121, thereby forming the singlet excitation state of the guest material 121.

[0288] Since the guest material 121 is a fluorescent material, it emits light immediately upon the formation of a singlet excitation state. To achieve a high light emission efficiency in this case, the fluorescence quantum yield of the guest material 121 is preferably high. The same applies if a singlet excitation state is formed by recombination of charge carriers in the guest material 121.

[0289] Next, a case is described in which the recombination of charge carriers forms a triplet excitation state of the host material 122. The correlation of the energy levels of the host material 122 and the guest material 121 in this case is given in Fig. 5C shown. The following clarifies what terms and symbols in Fig. 5C. It should be noted that, since the T1 level of the host material 122 is preferably lower than the T1 level of the guest material 121, Fig. 5C shows this preferable case. However, the T1 level of the host material 122 can be higher than the T1 level of the guest material 121. Guest (121): the guest material 121 (the fluorescent material); Host (122): the host material 122; S FG : the S1 level of guest material 121 (the fluorescent material); T FG : the T1 level of guest material 121 (the fluorescent material); S FH : the S1 level of host material 122; and T FH : the T1 level of host material 122.

[0290] As in Fig. As shown in 5C, a triplet-triplet annihilation (TTA) occurs; that is, triplet excitons formed by charge carrier recombination interact with each other, and excitation energy is transferred and spin angular momenta are exchanged; as a result, a reaction occurs in which the triplet excitons are converted into singlet excitons, which increase the energy of the S1 level of the host material 122 (S FH ) exhibit (see TTA in Fig. 5C). The singlet excitation energy of the host material 122 is determined by S FH to the S1 level of the guest material 121 (S FG ) transferred, which has a lower energy than S FH (see Route E5 in Fig. 5C), and a singlet excitation state of the guest material 121 is formed, causing the guest material 121 to emit light.

[0291] It should be noted that in the case where the density of triplet excitons in the light-emitting layer is sufficiently high (e.g. 1 × 10⁻¹²), -12 cm -3 or higher), only the response of two triplet excitons that are close together can be considered, whereas the deactivation of a single triplet exciton can be ignored.

[0292] In the case where a triplet excitation state of the guest material 121 is formed by charge carrier recombination, the triplet excitation state of the guest material 121 is thermally deactivated, and it is difficult to use it for light emission. However, in the case where the T1 level of the host material 122 (T FH ) is lower than the T1 level of the guest material 121 (T FG ), the triplet excitation energy of guest material 121 from the T1 level of guest material 121 (T FG ) to the T1 level of host material 122 (T FH ) transferred (see Route E6 in Fig. 5C) and then used for a TTA.

[0293] In other words, the host material 122 preferably has a function for converting triplet excitation energy into singlet excitation energy by inducing a TTA, such that the triplet excitation energy generated in the light-emitting layer 120 can be partially converted into singlet excitation energy in the host material 122 by the TTA. The singlet excitation energy can be transferred to the guest material 121 and extracted as fluorescence. To obtain this effect, the S1 level of the host material 122 (S FH ) preferably higher than the S1 level of the guest material 121 (S FG ). Furthermore, the T1 level of the host material is 122 (T FH ) preferably lower than the T1 level of the guest material 121 (T FG ).

[0294] It should be noted that especially in the case where the T1 level of the guest material is 121 (T FG ) is lower than the T1 level of the host material 122 (T FH ), the weight ratio of the guest material 121 to the host material 122 is preferably low. In particular, the weight ratio of the guest material 121 to the host material 122 is preferably greater than 0 and less than or equal to 0.05, in which case the probability of charge carrier recombination in the guest material 121 can be reduced. Furthermore, the probability of energy transfer from the T1 level of the host material 122 (T FH ) to the T1 level of the guest material 121 (T FG ) will be reduced.

[0295] It should be noted that the host material 122 can consist of a single compound or a multitude of compounds.

[0296] In the case where the light-emitting units 106 and 108 contain guest materials with different emission colors, light emitted by the light-emitting layer 120 preferably exhibits a peak on the shorter wavelength side than light emitted by the light-emitting layer 170. The luminance of a light-emitting element using a material with a high triplet excitation energy level tends to degrade rapidly. TTA (triplet excitation absorption) is utilized in the light-emitting layer emitting short-wavelength light, thus providing a light-emitting element with less luminance degradation. <Strukturbeispiel 2 des Licht emittierenden Elements>

[0297] Fig. 6A is a schematic cross-sectional view of a light-emitting element 252.

[0298] The light-emitting element 252, which is in Fig. Figure 6A shows that, like the light-emitting element 250 described above, it includes a plurality of light-emitting units (the light-emitting unit 106 and a light-emitting unit 110 in Fig. 6A) between a pair of electrodes (electrode 101 and electrode 102). At least one of the light-emitting units has a structure similar to that of the EL layer 100. It should be noted that light-emitting unit 106 and light-emitting unit 110 may have the same structure or different structures.

[0299] The light-emitting element 252, which is in Fig. As shown in Figure 6A, the light-emitting unit 106 and the light-emitting unit 110 are arranged one above the other, and a charge-generating layer 115 is provided between the light-emitting unit 106 and the light-emitting unit 110. For example, the EL layer 100 is preferably used in the light-emitting unit 106.

[0300] The light-emitting element 252 comprises a light-emitting layer 140 and a light-emitting layer 170. The light-emitting unit 106 comprises, in addition to the light-emitting layer 170, the hole injection layer 111, the hole transport layer 112, an electron transport layer 113, and an electron injection layer 114. The light-emitting unit 110 comprises, in addition to the light-emitting layer 140, a hole injection layer 116, a hole transport layer 117, an electron transport layer 118, and an electron injection layer 119.

[0301] If the structure described in embodiment 1 is used for at least one of the plurality of units, a light-emitting element with high emission efficiency can be provided.

[0302] The light-emitting layer of the light-emitting unit 110 preferably contains a phosphorescent material. In other words, the light-emitting layer 140 contained in the light-emitting unit 110 preferably contains a phosphorescent material, and the light-emitting layer 170 contained in the light-emitting unit 106 preferably has the structure of the light-emitting layer 130 or the light-emitting layer 135 described in embodiment 1. A structural example of the light-emitting element 252 in this case is described below.

[0303] The light-emitting layer 140, which is contained in the light-emitting unit 110, contains a guest material 141 and a host material 142, as shown in Fig. Figure 6B shows the host material 142 containing an organic compound 142_1 and an organic compound 142_2. In the following description, the guest material 141, contained in the light-emitting layer 140, is a phosphorescent material. <<Lichtemissionsmechanismus der Licht emittierenden Schicht 140> >

[0304] The light emission mechanism of the light-emitting layer 140 will be described below.

[0305] The organic compound 142_1 and the organic compound 142_2, which are contained in the light-emitting layer 140, form an exciplex.

[0306] The combination of organic compound 142_1 and organic compound 142_2 is acceptable as long as it can form an exciplex; however, preferably one of them is a compound with a hole transport property and the other is a compound with an electron transport property.

[0307] Fig. 6C shows a correlation between the energy levels of organic compound 142_1, organic compound 142_2, and guest material 141 in the light-emitting layer 140. The following clarifies what terms and numerical symbols in Fig. Represent 6C: Guest (141): the guest material 141 (phosphorescent material); Host (142_1): the organic compound 142_1 (host material); Host (142_2): the organic compound 142_2 (host material); T PG : a T1 level of the guest material 141 (the phosphorescent material); S PH1 : an S1 level of the organic compound 142_1 (of the host material); T PH1 : a T1 level of the organic compound 142_1 (of the host material); S PH2 : an S1 level of the organic compound 142_2 (of the host material); T PH2 : a T1 level of the organic compound 142_2 (of the host material); S PE : an S1 level of the exciplex; and T PE : a T1 level of the exciplex.

[0308] Organic compound 142_1 and organic compound 142_2 form an exciplex, and this is at the S1 level (S PE ) and the T1 level (T PE ) of the exciplex around energy levels that are close together (see Route E7 in Fig. 6C).

[0309] One of the organic compounds 142_1 and 142_2 accepts a hole, and the other accepts an electron, readily forming an exciplex. Alternatively, when one of the organic compounds is excited to a certain state, the other immediately interacts with it to form an exciplex. Consequently, most excitons in the light-emitting layer 140 exist as exciplexes. The excitation state of the host material 142 can be formed with low excitation energy because the excitation energy levels (S1, S2, S3, S4, S5, S6, S7, S8, S9, S1 ... PE and T PE ) of the exciplex are lower than the S1 levels (S PH1 and S PH2 ) of the host materials (the organic compounds 142_1 and 142_2) that form the exciplex. This can reduce the drive voltage of the light-emitting element.

[0310] Both energies on S PE and T PE The exciplex signals are then transferred to the T1 level of the guest material 141 (the phosphorescent material); thus, a light emission is obtained (see routes E8 and E9 in Fig. 6C).

[0311] Furthermore, the T1 level (T PE ) of the exciplex preferably higher than the T1 level (T PG ) of the guest material 141. Accordingly, the singlet excitation energy and the triplet excitation energy of the formed exciplex can be determined from the S1 level (S PE ) and the T1 level (T PE ) of the exciplex to the T1 level (T PG ) of the guest material 141 will be transferred.

[0312] It should be noted that, in order to efficiently transfer excitation energy from the exciplex to the guest material 141, the T1 level (T PE ) of the exciplex preferably lower than or equal to the T1 levels (T PH1 and T PH2 ) of the organic compounds (organic compound 142_1 and organic compound 142_2) that form the exciplex. Consequently, quenching of the triplet excitation energy of the exciplex due to the organic compounds (organic compounds 142_1 and 142_2) is less likely, leading to efficient energy transfer from the exciplex to the guest material 141.

[0313] To efficiently form an exciplex through organic compound 142_1 and organic compound 142_2, the following is preferably fulfilled: The HOMO level of one of organic compound 142_1 and organic compound 142_2 is higher than that of the other, and the LUMO level of one of organic compound 142_1 and organic compound 142_2 is higher than that of the other. For example, if organic compound 142_1 has hole-transport properties and organic compound 142_2 has electron-transport properties, the HOMO level of organic compound 142_1 is preferably higher than the HOMO level of organic compound 142_2, and the LUMO level of organic compound 142_1 is preferably higher than the LUMO level of organic compound 142_2.Alternatively, if organic compound 142_2 has a hole transport property and organic compound 142_1 has an electron transport property, the HOMO level of organic compound 142_2 is preferably higher than the HOMO level of organic compound 142_1, and the LUMO level of organic compound 142_2 is preferably higher than the LUMO level of organic compound 142_1. In particular, the energy difference between the HOMO level of organic compound 142_1 and the HOMO level of organic compound 142_2 is preferably greater than or equal to 0.05 eV, more preferably greater than or equal to 0.1 eV, and even more preferably greater than or equal to 0.2 eV.Alternatively, the energy difference between the LUMO level of organic compound 142_1 and the LUMO level of organic compound 142_2 is preferably greater than or equal to 0.05 eV, more preferably greater than or equal to 0.1 eV, and even more preferably greater than or equal to 0.2 eV.

[0314] In the case where the combination of organic compounds 142_1 and 142_2 is a combination of a compound with hole transport properties and a compound with electron transport properties, the charge carrier balance can be easily controlled by regulating the mixing ratio. In particular, the weight ratio of the compound with hole transport properties to the compound with electron transport properties is preferably within a range of 1:9 to 9:1. Since the charge carrier balance can be easily controlled by the structure, a charge carrier recombination range can also be easily controlled.

[0315] Furthermore, the mechanism of the energy transfer process between the molecules of the host material 142 (exciplex) and the guest material 141 can be described, as in embodiment 1, using two mechanisms, namely the Förster mechanism (dipole-dipole interaction) and the Dexter mechanism (electron exchange interaction). Reference can be made to embodiment 1 for the Förster and Dexter mechanisms.

[0316] To promote energy transfer from the singlet excitation state of the host material (exciplex) to the triplet excitation state of the guest material 141, which serves as an energy acceptor, the emission spectrum of the exciplex preferably overlaps with the absorption band of the guest material 141 located on the longest wavelength side (lowest energy side). Consequently, the efficiency of generating the triplet excitation state of the guest material 141 can be increased.

[0317] If the light-emitting layer 140 has the structure described above, light emission from the guest material 141 (the phosphorescent material) of the light-emitting layer 140 can be obtained efficiently.

[0318] It should be noted that in this description and the like, the processes described above via routes E7, E8, and E9 can be referred to as exciplex triplet energy transfer (ExTET). In other words, in the light-emitting layer 140, excitation energy is transferred from the exciplex to the guest material 141. In this case, the efficiency of the reverse intersystem crossing of T PE to S PE and the emission quantum yield of S PE not necessarily high; thus, materials can be selected from a wide range of options.

[0319] It should be noted that light emitted by the light-emitting layer 170 preferably exhibits a peak on the shorter wavelength side than light emitted by the light-emitting layer 140. Since the luminance of a light-emitting element using a phosphorescent material emitting short-wavelength light tends to degrade rapidly, short-wavelength fluorescence is employed to provide a light-emitting element with less luminance degradation.

[0320] It should be noted that in each of the structures described above, the emission colors of the guest materials used in light-emitting units 106 and 108, or in light-emitting units 106 and 110, may be the same or different. If the same guest materials, emitting light of the same color, are used in light-emitting units 106 and 108, or in light-emitting units 106 and 110, light-emitting elements 250 and 252 can exhibit high emission luminance at a low current value, which is preferable.In the case where guest materials emitting light of different colors are used for light-emitting units 106 and 108, or for light-emitting units 106 and 110, light-emitting elements 250 and 252 can exhibit multicolored light emission, which is preferable. In this case, when a variety of light-emitting materials with different emission wavelengths are used in one or both of light-emitting layers 120 and 170, or in one or both of light-emitting layers 140 and 170, lights with different emission peaks synthesize light emission from light-emitting elements 250 and 252. That is, the emission spectrum of light-emitting element 250 has at least two peak values.

[0321] The above structure is also suitable for obtaining white light emission. If the light-emitting layer 120 and the light-emitting layer 170, or the light-emitting layer 140 and the light-emitting layer 170, emit light of complementary colors, white light emission can be obtained. In particular, the guest materials are preferably selected such that white light emission with high color rendering properties, or at least light emission in red, green, and blue, can be obtained.

[0322] At least one of the light-emitting layers 120, 140, and 170 can be subdivided into layers, and the subdivided layers can each contain a different light-emitting material. That is, at least one of the light-emitting layers 120, 140, and 170 can consist of two or more layers. For example, in the case where the light-emitting layer is formed by stacking a first light-emitting layer and a second light-emitting layer on top of each other in that order, starting from the hole-transport layer side, the first light-emitting layer is formed using a material with hole-transport properties as its host material, and the second light-emitting layer is formed using a material with electron-transport properties as its host material.In this case, a light-emitting material contained in the first light-emitting layer can be the same as, or different from, a light-emitting material contained in the second light-emitting layer. Furthermore, the materials can have properties for emitting light of the same color or light of different colors. White light emission with high color rendering, composed of three primary colors or four or more colors, can be obtained by using a variety of light-emitting materials that emit light of different colors. <Material, das bei den Licht emittierenden Schichten verwendet werden kann>

[0323] Next, materials that can be used in the light-emitting layers 120, 140 and 170 are described. <<Material, das bei der Licht emittierenden Schicht 120 verwendet werden kann> >

[0324] In the light-emitting layer 120, the host material 122 is present in the highest weight fraction, and the guest material 121 (the fluorescent material) is dispersed in the host material 122. The S1 level of the host material 122 is preferably higher than the S1 level of the guest material 121 (the fluorescent material), while the T1 level of the host material 122 is preferably lower than the T1 level of the guest material 121 (the fluorescent material).

[0325] In the light-emitting layer 120, the guest material 121 is preferably, but not specifically limited to, an anthracene derivative, a tetracene derivative, a chrysene derivative, a phenanthrene derivative, a pyrene derivative, a perylene derivative, a stilbene derivative, an acridone derivative, a coumarin derivative, a phenoxazine derivative, a phenothiazine derivative or the like, and for example any of the following materials can be used.

[0326] The examples include 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-Bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-bis(4-tert-butylphenyl)pyrene-1,6-diamine (abbreviation: 1,6tBu-FLPAPrn), N,N'-Diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-3,8-dicyclohexylpyrene-1,6-diamine (abbreviation: ch-1,6FLPAPrn), N,N'-Bis[4-(9H-carbazol-9-yl)phenyl)-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-Tetra(tert-butyl)perylene (abbreviation: TBP), 4-(10-Phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N''-(2-tert-Butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA), N,9-Diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-Diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA) N,N,N,N,N',N',N',N'',N'''-Octaphenyldibenzo[g,p]chrysen-2,7,10,15-tetraamine (abbreviation: DBC1), Coumarin 30, N-(9,10-Diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-Biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), N-(9,10-Diphenyl-2-anthηl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-Bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPhA), 9,10-Bis(1,1'-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-Triphenylanthracene-9-amine (abbreviation: DPhAPhA), Coumarin 6, Coumarin 545T, N,N'-Diphenylquinacridone (abbreviation: DPQd), Rubrene, 2,8-Di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (abbreviation: TBRb), Nile Red, 5,12-Bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT) 2-(2-{2-[4-(Dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-Methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N',N'-Tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-Diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-Isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[lj]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[lj]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanenitrile (abbreviation: DCJTB), 2-(2,6-Bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanenitrile (abbreviation: BisDCM), 2-{2,6-Bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[lj]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanenitrile (abbreviation: BisDCJTM) and 5,10,15,20-Tetraphenylbisbenzo[5,6]indeno[1,2,3-cd:1',2',3'-lm]perylene.,

[0327] Although there is no particular restriction regarding a material that can be used as the host material 122 in the light-emitting layer 120, any of the following materials, for example, can be used: metal complexes, such as... B. Tris(8-quinolinolato)aluminium(III) (abbreviation: Alq), Tris(4-methyl-8-quinolinolato)aluminium(III) (abbreviation: Almq3), Bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), Bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminium(III) (abbreviation: BAlq), Bis(8-quinolinolato)zinc(II) (abbreviation: Znq), Bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO) and Bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ); heterocyclic compounds, such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 2,2',2''-(1,3,5-Benzenetriyl)-tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), bathophenanthroline (abbreviation: BPhen), bathocuproine (abbreviation: BCP) and 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11); and aromatic amine compounds, such as... Examples include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), and 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB). Additionally, condensed polycyclic aromatic compounds, such as... B. anthracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives and dibenzo[g,p]chrysene derivatives, are given, and specific examples are 9,10-diphenylanthracene (abbreviation: DPAnth), N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine (abbreviation: DPhPA),4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), N,9-Diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine (abbreviation: PCAPBA), N,9-diphenyl-N-(9,10-diphenyl-2-anthryl)-9H-carbazol-3-amine (abbreviation: 2PCAPA), 6,12-Dimethoxy-5,11-diphenylchrysene, N,N,N',N',N',N'',N'',N''',N'''-Octaphenyldibenzo[g,p]chηsene-2,7,10,15-tetramine (abbreviation: DBC1), 9-[4-(10-Phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA), 3,6-Diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: DPCzPA), 9,10-Bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 9,10-Di(2-naphthyl)anthracene (abbreviation: DNA), 2-tert-Butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 9,9'-Bianthryl (Abbreviation: BANT), 9,9'-(Stilben-3,3'-diyl)diphenanthrene (Abbreviation: DPNS), 9,9'-(Stilben-4,4'-diyl)diphenanthrene (Abbreviation: DPNS2), 1,3,5-Tri(1-pyrenyl)benzene (abbreviation: TPB3) and the like. One or more substances with a larger energy gap than guest material 121 are preferably selected from these substances and known substances.

[0328] The light-emitting layer 120 can have a structure in which two or more layers are arranged one above the other. For example, if the light-emitting layer 120 is formed by arranging a first light-emitting layer and a second light-emitting layer on top of each other in that order, starting from the side of the hole transport layer, the first light-emitting layer is formed using a substance with hole transport properties as the host material, and the second light-emitting layer is formed using a substance with electron transport properties as the host material.

[0329] In the light-emitting layer 120, the host material 122 can consist of one type of compound or a variety of compounds. Alternatively, the light-emitting layer 120 can contain an additional material besides the host material 122 and the guest material 121. <<Material, das bei der Licht emittierenden Schicht 140 verwendet werden kann> >

[0330] In the light-emitting layer 140, the host material 142 is present in the highest weight fraction, and the guest material 141 (the phosphorescent material) is dispersed in the host material 142. The T1 levels of the host materials 142 (the organic compounds 142_1 and 142_2) of the light-emitting layer 140 are preferably higher than the T1 level of the guest material 141 of the light-emitting layer 140.

[0331] Examples of organic compound 142_1 include a zinc- or aluminum-based metal complex, an oxadiazole derivative, a triazole derivative, a benzimidazole derivative, a quinoxaline derivative, a dibenzoquinoxaline derivative, a dibenzothiophene derivative, a dibenzofuran derivative, a pyrimidine derivative, a triazine derivative, a pyridine derivative, a bipyridine derivative, and a phenanthroline derivative. Further examples include an aromatic amine and a carbazole derivative. In particular, the electron transport material and the hole transport material described in embodiment 1 can be used.

[0332] The organic compound 142_2 is preferably a substance that can form an exciplex together with the organic compound 142_1. In particular, the electron transport material and the hole transport material described in embodiment 1 can be used. In this case, the organic compound 142_1, the organic compound 142_2, and the guest material 141 (the phosphorescent material) are preferably selected such that the emission peak of the exciplex formed by the organic compound 142_1 and the organic compound 142_2 overlaps with an absorption band, in particular with an absorption band on the longest wavelength side, of a triplet metal-to-ligand charge transfer (MLCT) transition of the guest material 141 (the phosphorescent material). This makes it possible to provide a light-emitting element with drastically improved emission efficiency.It should be noted that in the case where a thermally activated, delayed fluorescent material is used instead of the phosphorescent material, the absorption band on the longest wavelength side is preferably a singlet absorption band.

[0333] The guest material 141 (as phosphorescent material) can be an organometallic complex or a metal complex based on iridium, rhodium, or platinum; in particular, an organoiridium complex, such as an orthometallated complex based on iridium, is preferred. The orthometallated ligand can be a 4H-triazole ligand, a 1H-triazole ligand, an imidazole ligand, a pyridine ligand, a pyrimidine ligand, a pyrazine ligand, an isoquinoline ligand, and the like. The metal complex can be a platinum complex with a porphyrin ligand, and the like. In particular, the material described in embodiment 1 as an example of guest material 131 can be used.

[0334] Any material can be used as the light-emitting material contained in the light-emitting layer 140, as long as the material can convert the triplet excitation energy into light emission. In addition to a phosphorescent material, a thermally activated, delayed-release fluorescent material can be specified as an example of a material that can convert the triplet excitation energy into light emission. Therefore, it is acceptable to replace "phosphorescent material" with "thermally activated, delayed-release fluorescent material" in the description.

[0335] The material exhibiting thermally activated delayed fluorescence can be a material capable of forming a singlet excitation state from a triplet excitation state through reverse intersystem crossing, or a combination of a variety of materials forming an exciplex.

[0336] In the case where the material exhibiting thermally activated delayed fluorescence consists of a single material type, in particular any of the thermally activated delayed fluorescent materials described in embodiment 1 may be used.

[0337] In the case where the thermally activated, delayed-fluorescence material is used as the host material, a combination of two types of compounds forming an exciplex is preferably used. In this case, the exciplex-forming combination of a compound that readily accepts electrons and a compound that readily accepts holes, as described above, is particularly preferred. <<Material, das bei der Licht emittierenden Schicht 170 verwendet werden kann> >

[0338] A material suitable for the light-emitting layer 170 can be used, such that a light-emitting element with high emission efficiency can be formed.

[0339] There is no restriction regarding the emission colors of the light-emitting materials contained in the light-emitting layers 120, 140, and 170, and they can be the same or different. Light emitted by the light-emitting materials is mixed and extracted from the element; therefore, for example, if their emission colors are complementary, the light-emitting element can emit white light. Considering the reliability of the light-emitting element, the emission peak wavelength of the light-emitting material contained in the light-emitting layer 120 is preferably shorter than that of the light-emitting material contained in the light-emitting layer 170.

[0340] It should be noted that the light-emitting units 106, 108 and 110 and the charge-generating layer 115 can be formed by an evaporation process (including a vacuum evaporation process), an inkjet process, a coating process, gravure printing or the like.

[0341] The structure described in this embodiment can be used in a suitable combination with any of the structures described in the other embodiments. (Version 3)

[0342] In this embodiment, examples of light-emitting elements with structures that differ from those described in embodiments 1 and 2 are given below, based on Fig. 7A and Fig. 7B, Fig. 8A and Fig. 8B, Fig. 9A to Fig. 9C as well Fig. 10A to Fig. 10C described. <Strukturbeispiel 1 des Licht emittierenden Elements>

[0343] Fig. 7A and Fig. Figure 7B are cross-sectional views, each representing a light-emitting element of an embodiment of the present invention. Fig. 7A and Fig. In some cases, section 7B has a similar function to the one in Fig. 1A through the same hatching pattern as in Fig. Sections 1A are shown without a separate reference symbol. Furthermore, common reference symbols are used for sections with similar functions, and a detailed description of the sections is omitted in some cases.

[0344] Light-emitting elements 260a and 260b in Fig. 7A and Fig. 7B can have a bottom-emission structure, in which light is extracted via the substrate 200, or a top-emission structure, in which light emitted by the light-emitting element is extracted in the direction opposite to the substrate 200. However, an embodiment of the present invention is not limited to this structure, and a light-emitting element with a dual-emission structure, in which light emitted by the light-emitting element is extracted both upwards and downwards with respect to the substrate 200, can be used.

[0345] In the case where the light-emitting elements 260a and 260b each have a bottom-emission structure, the electrode 101 preferably has a light-transmitting function and the electrode 102 preferably has a light-reflecting function. Alternatively, in the case where the light-emitting elements 260a and 260b each have a top-emission structure, the electrode 101 preferably has a light-reflecting function and the electrode 102 preferably has a light-transmitting function.

[0346] The light-emitting elements 260a and 260b each comprise electrode 101 and electrode 102 above substrate 200. Between electrodes 101 and 102, a light-emitting layer 123B, a light-emitting layer 123G, and a light-emitting layer 123R are provided. The hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119 are also provided.

[0347] The light-emitting element 260b includes, as part of the electrode 101, a conductive layer 101a, a conductive layer 101b above the conductive layer 101a, and a conductive layer 101c below the conductive layer 101a. In other words, the light-emitting element 260b includes the electrode 101 with a structure in which the conductive layer 101a is arranged between the conductive layer 101b and the conductive layer 101c.

[0348] In the light-emitting element 260b, the conductive layer 101b and the conductive layer 101c can be formed from different materials or from the same material. The electrode 101 preferably has a structure in which the conductive layer 101a is arranged between the layers formed from the same conductive material, in which case structuring by etching can be easily carried out in the process for forming the electrode 101.

[0349] In the light-emitting element 260b, the electrode 101 can include either the conductive layer 101b or the conductive layer 101c.

[0350] For each of the conductive layers 101a, 101b and 101c contained in the electrode 101, the structure and materials of the electrode 101 or 102 described in embodiment 1 can be used.

[0351] In Fig. 7A and Fig. 7B is a partition 145 provided between a region 221B, a region 221G, and a region 221R, which are arranged between electrode 101 and electrode 102. The partition 145 has insulating properties. The partition 145 covers end sections of electrode 101 and has openings that overlap with the electrode. The partition 145 allows the electrode 101, which is provided above the substrate 200 in the regions, to be divided into island shapes.

[0352] It should be noted that the light-emitting layer 123B and the light-emitting layer 123G can overlap each other in an area where they overlap with the partition 145. The light-emitting layer 123G and the light-emitting layer 123R can overlap each other in an area where they overlap with the partition 145. The light-emitting layer 123R and the light-emitting layer 123B can overlap each other in an area where they overlap with the partition 145.

[0353] The partition 145 has insulating properties and is formed using an inorganic or organic material. Examples of inorganic materials include silicon dioxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, and aluminum nitride. Examples of organic materials include photosensitive resin materials, such as acrylic resins and polyimide resins.

[0354] It should be noted that a silicon oxynitride film refers to a film in which the oxygen content is higher than the nitrogen content. The silicon oxynitride film preferably contains oxygen, nitrogen, silicon, and hydrogen in the respective ranges of 55 atomic percent to 65 atomic percent, 1 atomic percent to 20 atomic percent, 25 atomic percent to 35 atomic percent, and 0.1 atomic percent to 10 atomic percent. A silicon nitride oxide film refers to a film in which the nitrogen content is higher than the oxygen content. The silicon nitride oxide film preferably contains nitrogen, oxygen, silicon, and hydrogen in the respective ranges of 55 atomic percent to 65 atomic percent, 1 atomic percent to 20 atomic percent, 25 atomic percent to 35 atomic percent, and 0.1 atomic percent to 10 atomic percent.

[0355] The light-emitting layers 123R, 123G, and 123B preferably contain light-emitting materials with functions for emitting light of different colors. For example, if light-emitting layer 123R contains a light-emitting material with a function for emitting red, region 221R emits red light. If light-emitting layer 123G contains a light-emitting material with a function for emitting green, region 221G emits green light. If light-emitting layer 123B contains a light-emitting material with a function for emitting blue, region 221B emits blue light. The light-emitting element 260a or 260b with such a structure is used in a pixel of a display device, thereby enabling the production of a full-color display device. The thicknesses of the light-emitting layers can be the same or different.

[0356] One or more of the light-emitting layer 123B, the light-emitting layer 123G, and the light-emitting layer 123R preferably have at least one of the structures of the light-emitting layers 130 and 135 described in embodiment 1. In this case, a light-emitting element with high emission efficiency can be produced.

[0357] One or more of the light-emitting layers 123B, 123G and 123R may contain two or more layers arranged on top of each other.

[0358] If at least one light-emitting layer comprises the light-emitting layer described in embodiments 1 and 2, and the light-emitting element 260a or 260b, which includes the light-emitting layer, is used in pixels of a display device, a display device with high emission efficiency can be manufactured. The display device, which includes the light-emitting element 260a or 260b, can thus have reduced power consumption.

[0359] By providing an optical element (e.g., a color filter, a polarizing plate, and an anti-reflective film) on the light extraction side of the electrode from which light is extracted, the color purity of each of the light-emitting elements 260a and 260b can be improved. Consequently, the color purity of a display device incorporating light-emitting element 260a or 260b can be improved. Alternatively, the reflection of external light from each of the light-emitting elements 260a and 260b can be reduced. Consequently, the contrast ratio of a display device incorporating light-emitting element 260a or 260b can be improved.

[0360] For the other components of the light-emitting elements 260a and 260b, reference can be made to the components of the light-emitting element of embodiments 1 and 2. <Strukturbeispiel 2 des Licht emittierenden Elements>

[0361] Next, structural examples that differ from the light-emitting elements described in will be presented. Fig. 7A and Fig. 7B are shown, based on Fig. 8A and Fig. 8B described.

[0362] Fig. 8A and Fig. Figure 8B shows cross-sectional views of a light-emitting element of an embodiment of the present invention. Fig. 8A and Fig. In some cases, section 8B has a similar function to the one in Fig. 7A and Fig. 7B through the same hatching pattern as in Fig. 7A and Fig. 7B is shown and not specifically marked with a reference symbol. Furthermore, common reference symbols are used for sections with similar functions, and a detailed description of such sections is not repeated in some cases.

[0363] Fig. 8A and Fig. Figure 8B presents structural examples of a light-emitting element that includes the light-emitting layer between a pair of electrodes. A light-emitting element 262a, which is in Fig. 8A shows a top-emission structure in which light is extracted in a direction opposite to the substrate 200, and a light-emitting element 262b which is in Fig. Figure 8B shows a bottom-emission structure in which light is extracted towards the side of the substrate 200. However, an embodiment of the present invention is not limited to these structures and may have a dual-emission structure in which light emitted by the light-emitting element is extracted both upwards and downwards with respect to the substrate 200 above which the light-emitting element is formed.

[0364] The light-emitting elements 262a and 262b each comprise electrode 101, electrode 102, electrode 103, and electrode 104 above substrate 200. At least one light-emitting layer 170, one light-emitting layer 190, and the charge-generating layer 115 are provided between electrode 101 and electrode 102, between electrode 102 and electrode 103, and between electrode 102 and electrode 104. The hole injection layer 111, the hole transport layer 112, the electron transport layer 113, the electron injection layer 114, the hole injection layer 116, the hole transport layer 117, the electron transport layer 118, and the electron injection layer 119 are also provided.

[0365] Electrode 101 includes a conductive layer 101a and a conductive layer 101b above and in contact with the conductive layer 101a. Electrode 103 includes a conductive layer 103a and a conductive layer 103b above and in contact with the conductive layer 103a. Electrode 104 includes a conductive layer 104a and a conductive layer 104b above and in contact with the conductive layer 104a.

[0366] The light-emitting element 262a, which is in Fig. 8A is shown, and the light-emitting element 262b, which is in Fig. As shown in Figure 8B, each includes a partition 145 between a region 222B, located between electrodes 101 and 102, a region 222G, located between electrodes 102 and 103, and a region 222R, located between electrodes 102 and 104. The partition 145 has insulating properties. The partition 145 covers end sections of electrodes 101, 103, and 104 and has openings that overlap with the electrodes. The partition 145 allows the electrodes, which are positioned above the substrate 200 in the regions, to be separated into island configurations.

[0367] The charge-generating layer 115 can be formed with a material obtained by adding an electron acceptor to a hole transport material, or with a material obtained by adding an electron donor to an electron transport material. It should be noted that if the conductivity of the charge-generating layer 115 is as high as that of the electrode pair, charge carriers generated in the charge-generating layer 115 could migrate to a neighboring pixel, potentially causing light emission in that pixel. To prevent such erroneous light emission from a neighboring pixel, the charge-generating layer 115 is preferably formed with a material whose conductivity is lower than that of the electrode pair.

[0368] The light-emitting elements 262a and 262b each comprise a substrate 220 provided with an optical element 224B, an optical element 224G, and an optical element 224R, in the direction in which light emitted from area 222B, light emitted from area 222G, and light emitted from area 222R are extracted. The light emitted from each area is emitted to the outside of the light-emitting element via each optical element. In other words, the light from area 222B, the light from area 222G, and the light from area 222R are emitted via optical element 224B, optical element 224G, and optical element 224R, respectively.

[0369] Optical elements 224B, 224G, and 224R each have a function for selectively transmitting light of a specific color from the incident light. For example, the light emitted from area 222B via optical element 224B is blue light, the light emitted from area 222G via optical element 224G is green light, and the light emitted from area 222R via optical element 224R is red light.

[0370] For example, a color layer (also called a color filter), a bandpass filter, a multilayer filter, or the like can be used for the optical elements 224R, 224G, and 224B. Alternatively, color conversion elements can be used as optical elements. A color conversion element is an optical element that converts incident light into light with a longer wavelength than the incident light. Quantum dot elements can be advantageously used as color conversion elements. The use of quantum dots can increase the color reproducibility of the display device.

[0371] One or more optical elements may be arranged over each of the optical elements 224R, 224G, and 224B. An additional optical element may be, for example, a circularly polarizing plate, an antireflection film, or the like. A circularly polarizing plate placed on the side from which light emitted by the light-emitting element of the display device is extracted can prevent a phenomenon in which light incident from the outside of the display device is reflected within the display device and directed back outwards. An antireflection film can attenuate external light reflected from a surface of the display device. This results in a clear observation of light emitted by the display device.

[0372] It should be noted that in Fig. 8A and Fig. 8B Blue light (B), green light (G) and red light (R) emitted from the areas via the optical elements are schematically represented by dashed arrows.

[0373] An opaque layer 223 is provided between the optical elements. The opaque layer 223 serves to block light emitted from adjacent areas. It should be noted that a structure without the opaque layer 223 can also be used.

[0374] The opaque layer 223 has the function of reducing the reflection of external light. The opaque layer 223 also has the function of preventing the mixing of light emitted by a neighboring light-emitting element. The opaque layer 223 can be a metal, a resin containing a black pigment, carbon black, a metal oxide, a composite oxide containing a solid solution of a variety of metal oxides, or the like.

[0375] It should be noted that optical element 224B and optical element 224G can overlap in an area where they overlap with the opaque layer 223. Furthermore, optical element 224G and optical element 224R can overlap in an area where they overlap with the opaque layer 223. Additionally, optical element 224R and optical element 224B can overlap in an area where they overlap with the opaque layer 223.

[0376] For the structures of substrate 200 and substrate 220, which is provided with the optical elements, reference can be made to embodiment 1.

[0377] Furthermore, the light-emitting elements 262a and 262b have a microcavity structure. < <Mikrokavitätsstruktur»

[0378] Light emitted by light-emitting layer 170 and light-emitting layer 190 oscillates between a pair of electrodes (e.g., electrode 101 and electrode 102). Light-emitting layer 170 and light-emitting layer 190 are positioned such that light of a desired wavelength is amplified relative to the light to be emitted. For example, by controlling the optical length from a reflective region of electrode 101 to the light-emitting region of light-emitting layer 170, as well as the optical length from a reflective region of electrode 102 to the light-emitting region of light-emitting layer 170, the light of a desired wavelength can be amplified relative to the light emitted by light-emitting layer 170.By controlling the optical length from the reflective region of electrode 101 to the light-emitting region of the light-emitting layer 190, as well as the optical length from the reflective region of electrode 102 to the light-emitting region of the light-emitting layer 190, the light with a desired wavelength can be amplified from the light emitted by the light-emitting layer 190. In the case of a light-emitting element in which several light-emitting layers (here, the light-emitting layers 170 and 190) are arranged one above the other, the optical lengths of the light-emitting layers 170 and 190 are preferably optimized.

[0379] For each of the light-emitting elements 262a and 262b, the amount of light with a desired wavelength emitted by the light-emitting layers 170 and 190 can be increased by regulating the thicknesses of the conductive layers (conductive layer 101b, conductive layer 103b, and conductive layer 104b) in each region. It should be noted that the thickness(es) of the hole injection layer 111 and / or the hole transport layer 112 or the electron injection layer 119 and / or the electron transport layer 118 can differ between the regions to increase the amount of light emitted by the light-emitting layers 170 and 190.

[0380] For example, in the case where the refractive index of the conductive material with a function for reflecting light in the electrodes 101 to 104 is lower than the refractive index of the light-emitting layer 170 or 190, the thickness of the conductive layer 101b of the electrode 101 is regulated such that the optical length between the electrode 101 and the electrode 102 is equal to m B λ B / 2 is (m B is a natural number, and λ B (is the wavelength of the light that is amplified in region 222B). The thickness of the conductive layer 103b of electrode 103 is similarly regulated such that the optical length between electrode 103 and electrode 102 is equal to m G λ G / 2 is (m G is a natural number, and λ G (is the wavelength of the light that is amplified in the region 222G). Furthermore, the thickness of the conductive layer 104b of the electrode 104 is regulated such that the optical length between the electrode 104 and the electrode 102 is equal to m R λ R / 2 is (m R is a natural number, and λ R is the wavelength of the light that is amplified in the 222R range).

[0381] In cases where it is difficult to precisely determine the reflective areas of electrodes 101 to 104, the optical length for increasing the intensity of the light emitted by light-emitting layer 170 or light-emitting layer 190 can be derived by assuming that certain areas of electrodes 101 to 104 are the reflective areas. Similarly, in cases where it is difficult to precisely determine the light-emitting areas of light-emitting layer 170 and light-emitting layer 190, the optical length for increasing the intensity of the light emitted by light-emitting layer 170 and light-emitting layer 190 can be derived by assuming that certain areas of light-emitting layer 170 and light-emitting layer 190 are the light-emitting areas.

[0382] In the above manner, the microcavity structure, in which the optical length between the pair of electrodes in the respective areas is regulated, can suppress scattering and absorption of light near the electrodes, resulting in high light extraction efficiency.

[0383] In the above structure, the conductive layers 101b, 103b, and 104b preferably have a light-transmitting function. The materials of the conductive layers 101b, 103b, and 104b can be the same or different. Preferably, the same material is used for the conductive layer 101b, the conductive layer 103b, and the conductive layer 104b, since structuring by etching can be easily carried out during the formation process of the electrode 101, the electrode 103, and the electrode 104. Each of the conductive layers 101b, 103b, and 104b can have a multilayer structure consisting of two or more layers.

[0384] Since the light-emitting element 262a, which is in Fig. Figure 8A shows a top-emission structure, and the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a preferably have a light-reflecting function. Furthermore, the electrode 102 preferably has light-transmitting and light-reflecting functions.

[0385] Since the light-emitting element 262b, which is in Fig. Figure 8B shows a bottom-emission structure, and the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a preferably have functions for transmitting and reflecting light. Furthermore, the electrode 102 preferably has a function for reflecting light.

[0386] In each of the light-emitting elements 262a and 262b, the conductive layers 101a, 103a, and 104a can be made of different materials or of the same material. If the conductive layers 101a, 103a, and 104a are made of the same material, the manufacturing costs of the light-emitting elements 262a and 262b can be reduced. It should be noted that each of the conductive layers 101a, 103a, and 104a can have a multilayer structure comprising two or more layers.

[0387] At least one of the structures described in embodiments 1 and 2 is preferably used for at least one of the light-emitting layers 170 and 190 contained in the light-emitting elements 262a and 262b. In this way, the light-emitting elements can exhibit a high emission efficiency.

[0388] One or both of the light-emitting layers 170 and 190 can, like light-emitting layers 190a and 190b, have a multilayer structure consisting of two layers. Two types of light-emitting materials (a first compound and a second compound) for emitting light of different colors are used in the two light-emitting layers, so that light of a variety of colors can be obtained simultaneously. In particular, the light-emitting materials of the light-emitting layers are preferably selected such that white light can be obtained by combining light emissions from light-emitting layers 170 and 190.

[0389] One or both of the light-emitting layers 170 and 190 may have a multilayer structure consisting of three or more layers, in which one layer may contain no light-emitting material.

[0390] By using the light-emitting element 262a or 262b, which includes the light-emitting layer having at least one of the structures described in embodiments 1 and 2, in pixels of a display device in the manner described above, a display device with high emission efficiency can be produced. The display device, which includes the light-emitting element 262a or 262b, can thus have low power consumption.

[0391] For the other components of the light-emitting elements 262a and 262b, reference can be made to the components of the light-emitting element 260a or 260b or of the light-emitting element of embodiments 1 and 2. <Herstellungsverfahren des Licht emittierenden Elements>

[0392] Next, a method for manufacturing a light-emitting element of an embodiment of the present invention will be described below using the following: Fig. 9A to Fig. 9C and Fig. 10A to Fig. 10C is described. Here, a method for producing the light-emitting element 262a is described, which is described in Fig. 8A is shown.

[0393] Fig. 9A to Fig. 9C and Fig. 10A to Fig. Figure 10C are cross-sectional views illustrating a method for manufacturing the light-emitting element of an embodiment of the present invention.

[0394] The following described procedure for producing the light-emitting element 262a comprises a first to seventh step. <<Erster Schritt> >

[0395] In the first step, the electrodes (in particular the conductive layer 101a of electrode 101, the conductive layer 103a of electrode 103 and the conductive layer 104a of electrode 104) of the light-emitting elements are formed over the substrate 200 (see Fig. 9A).

[0396] In this embodiment, a conductive layer with a light-reflecting function is formed over the substrate 200 and processed into a desired shape, thereby forming the conductive layers 101a, 103a, and 104a. An alloy film of silver, palladium, and copper (also known as an Ag-Pd-Cu film or APC) is used as the conductive layer with a light-reflecting function. The conductive layers 101a, 103a, and 104a are preferably formed in a single step for processing the same conductive layer, as this reduces manufacturing costs.

[0397] It should be noted that a large number of transistors can be formed above substrate 200 before the first step. These transistors can be electrically connected to the conductive layers 101a, 103a, and 104a. <<Zweiter Schritt> >

[0398] In the second step, the transparent conductive layer 101b with a function for transmitting light is formed over the conductive layer 101a of the electrode 101, the transparent conductive layer 103b with a function for transmitting light is formed over the conductive layer 103a of the electrode 103, and the transparent conductive layer 104b with a function for transmitting light is formed over the conductive layer 104a of the electrode 104 (see Fig. 9B).

[0399] In this embodiment, the conductive layers 101b, 103b, and 104b, each having a function for transmitting light, are formed over the respective conductive layers 101a, 103a, and 104a, each having a function for reflecting light, thereby forming electrode 101, electrode 103, and electrode 104. ITSO films are used as the conductive layers 101b, 103b, and 104b.

[0400] The conductive layers 101b, 103b, and 104b, which have a light-transmitting function, can be formed in a variety of steps. When these conductive layers are formed in a variety of steps, they can be configured to have thicknesses that allow for suitable microcavity structures in the respective regions. <<Dritter Schritt> >

[0401] In the third step, the partition 145 is formed, covering the end sections of the electrodes of the light-emitting element (see Fig. 9C).

[0402] The partition 145 includes an opening that overlaps the electrode. The conductive film exposed through the opening serves as the anode of the light-emitting element. In this embodiment, a polyimide-based resin is used as the partition 145.

[0403] In the first to third steps, various film formation processes and micromachining techniques can be employed, as there is no possibility of damaging the EL layer (a layer containing an organic compound). In this embodiment, a reflective conductive layer is formed by a sputtering process, a pattern is formed over the conductive layer by a lithography process, and then the conductive layer is processed into an island shape by a dry or wet etching process to form the conductive layer 101a of electrode 101, the conductive layer 103a of electrode 103, and the conductive layer 104a of electrode 104.Subsequently, a transparent conductive film is formed by a sputtering process, a pattern is formed over the transparent conductive film by a lithography process, and then the transparent conductive film is processed into island shapes by a wet etching process to form the electrodes 101, 103 and 104. <<Vierter Schritt> >

[0404] In the fourth step, the hole injection layer 111, the hole transport layer 112, the light-emitting layer 190, the electron transport layer 113, the electron injection layer 114 and the charge generation layer 115 are formed (see Fig. 10A).

[0405] The hole injection layer 111 can be formed by co-evaporation of a hole transport material and a material containing an acceptor substance. It should be noted that a co-evaporation process is an evaporation process in which several different substances are evaporated simultaneously from different evaporation sources. The hole transport layer 112 can be formed by evaporation of a hole transport material.

[0406] The light-emitting layer 190 can be formed by evaporating a guest material that emits light of at least one color selected from violet, blue, blue-green, green, yellow-green, yellow, orange, and red. A fluorescent or phosphorescent organic material can be used as the guest material. The structure of the light-emitting layer described in embodiments 1 and 2 is preferably employed. The light-emitting layer 190 can have a two-layer structure. In such a case, the two light-emitting layers preferably each contain a light-emitting material that emits light of a different color.

[0407] The electron transport layer 113 can be formed by evaporating a substance with high electron transport properties. The electron injection layer 114 can be formed by evaporating a substance with high electron injection properties.

[0408] The charge-generating layer 115 can be formed by evaporating a material obtained by adding an electron acceptor (acceptor) to a hole transport material, or a material obtained by adding an electron donor (donor) to an electron transport material. <<Fünfter Schritt> >

[0409] In the fifth step, the hole injection layer 116, the hole transport layer 117, the light-emitting layer 170, the electron transport layer 118, the electron injection layer 119 and the electrode 102 are formed (see Fig. 10B).

[0410] The hole injection layer 116 can be formed using a material and a process similar to those of the hole injection layer 111. The hole transport layer 117 can be formed using a material and a process similar to those of the hole transport layer 112.

[0411] The light-emitting layer 170 can be formed by evaporating a guest material that emits light of at least one color selected from violet, blue, blue-green, green, yellow-green, yellow, orange, and red. A fluorescent or phosphorescent organic compound can be used as the guest material. The structure of the light-emitting layer described in embodiments 1 and 2 is preferably employed. It should be noted that the light-emitting layer 170 and / or the light-emitting layer 190 preferably have the structure of a light-emitting layer described in embodiment 1. The light-emitting layer 170 and the light-emitting layer 190 preferably contain light-emitting organic compounds that emit light of different colors.

[0412] The electron transport layer 118 can be formed using a material and a process similar to those of the electron transport layer 113. The electron injection layer 119 can be formed using a material and a process similar to those of the electron injection layer 114.

[0413] Electrode 102 can be formed by layering a reflective conductive film and a translucent conductive film on top of each other. Electrode 102 can have a single-layer or a multi-layer structure.

[0414] By the steps described above, the light-emitting element, which includes area 222B, area 222G and area 222R above electrode 101, electrode 103 and electrode 104 respectively, is formed above substrate 200. <<Sechster Schritt> >

[0415] In the sixth step, the opaque layer 223, the optical element 224B, the optical element 224G and the optical element 224R are formed over the substrate 220 (see Fig. 10C).

[0416] The opaque layer 223 consists of a resin film containing a black pigment, which is formed in a desired area. Subsequently, the optical elements 224B, 224G, and 224R are formed over the substrate 220 and the opaque layer 223. The optical element 224B consists of a resin film containing a blue pigment, the optical element 224G consists of a resin film containing a green pigment, and the optical element 224R consists of a resin film containing a red pigment, which is formed in a desired area. <<Siebter Schritt> >

[0417] In the seventh step, the light-emitting element formed over the substrate 200 is attached to the opaque layer 223, the optical element 224B, the optical element 224G and the optical element 224R formed over the substrate 220 and sealed with a sealant (not shown).

[0418] The steps described above allow the light-emitting element 262a, which is in Fig. 8A is shown, to be trained.

[0419] The structure described in this embodiment can be used in a suitable combination with any of the structures described in the other embodiments. (Version 4)

[0420] In this embodiment, a display device of an embodiment of the present invention is described below by reference to Fig. 11A and Fig. 11B, Fig. 12A and Fig. 12B, Fig. 13, Fig. 14A and Fig. 14B, Fig. 15A and Fig. 15B, Fig. 16, Fig. 17A and Fig. 17B, Fig. 18 as well Fig. 19A and Fig. 19B described. <Strukturbeispiel 1 der Anzeigevorrichtung>

[0421] Fig. Figure 11A is a top view showing a display device 600, and Fig. 11B is a cross-sectional view along the dashed-dotted line AB and the dashed-dotted line CD in Fig. 11A. The display device 600 includes driver circuit sections (a signal line driver circuit section 601 and a scanning line driver circuit section 603) and a pixel section 602. It should be noted that the signal line driver circuit section 601, the scanning line driver circuit section 603, and the pixel section 602 have a function for controlling a light emission from a light-emitting element.

[0422] The display device 600 also includes an element substrate 610, a sealing substrate 604, a sealing agent 605, a region 607 enclosed by the sealing agent 605, a connecting line 608 and an FPC 609.

[0423] It should be noted that the connecting line 608 is a line for transmitting signals input to the signal line driver circuit section 601 and the sample line driver circuit section 603, and for receiving a video signal, clock signal, start signal, reset signal, and the like from the FPC 609, which serves as an external input connector. Although only the FPC 609 is shown here, the FPC 609 can be mounted on a printed circuit board (PWB).

[0424] The signal line driver circuit section 601 is a CMOS circuit combining an n-channel transistor 623 and a p-channel transistor 624. Various circuit types, such as a CMOS circuit, a PMOS circuit, or an NMOS circuit, can be used as the signal line driver circuit section 601 or as the sample line driver circuit section 603. Although a driver, in which a driver circuit section is formed, and a pixel are formed over the same surface of a substrate in the display device of this embodiment, the driver circuit section is not necessarily formed over the substrate and can be formed outside of the substrate.

[0425] The pixel section 602 includes a switching transistor 611, a current control transistor 612, and a lower electrode 613, which is electrically connected to a drain of the current control transistor 612. It should be noted that a partition 614 is configured to cover end sections of the lower electrode 613. A positive photosensitive acrylic resin film, for example, can be used as the partition 614.

[0426] To achieve advantageous coverage, the partition 614 is designed to have a curved surface with a curvature at its upper or lower end section. For example, if a positive photosensitive acrylic is used as the material of the partition 614, preferably only the upper end section of the partition 614 has a curved surface with a curvature (where the radius of curvature is 0.2 µm to 3 µm). Either a negative photosensitive resin or a positive photosensitive resin can be used as the partition 614.

[0427] It should be noted that there is no particular restriction regarding the structure of any of the transistors (transistors 611, 612, 623, and 624). For example, a staggered transistor may be used. Furthermore, there is no particular restriction regarding the polarity of these transistors. For example, n-channel and p-channel transistors may be used, or either n-channel or p-channel transistors may be used. In addition, there is no particular restriction regarding the crystallinity of a semiconductor film used for these transistors. For example, an amorphous semiconductor film or a crystalline semiconductor film may be used. Examples of semiconductor materials include Group 14 semiconductors (e.g., a semiconductor including silicon), compound semiconductors (including oxide semiconductors), organic semiconductors, and the like.For example, an oxide semiconductor having an energy gap of 2 eV or more, preferably 2.5 eV or more, and more preferably 3 eV or more, is preferably used for the transistors so that the reverse current of the transistors can be reduced. Examples of the oxide semiconductor include an In-Ga oxide and an In-M-Zn oxide (M is aluminum (Al), gallium (Ga), yttrium (Y), zirconium (Zr), lanthanum (La), cerium (Ce), tin (Sn), hafnium (Hf), or neodymium (Nd)).

[0428] An EL layer 616 and an upper electrode 617 are formed above the lower electrode 613. Here, the lower electrode 613 serves as the anode, and the upper electrode 617 serves as the cathode.

[0429] Furthermore, the EL layer 616 is formed using various methods, such as evaporation via an evaporation mask, inkjet printing, or rotational coating. The EL layer 616 can also contain low-molecular-weight or high-molecular-weight compounds (including oligomers and dendrimers).

[0430] It should be noted that a light-emitting element 618 is formed with the lower electrode 613, the EL layer 616, and the upper electrode 617. The light-emitting element 618 preferably has any of the structures described in embodiments 1 to 3. In the case where the pixel section includes a plurality of light-emitting elements, the pixel section can include either one of the light-emitting elements described in embodiments 1 to 3 or a light-emitting element with a different structure.

[0431] When the sealing substrate 604 and the element substrate 610 are joined together with the sealant 605, the light-emitting element 618 is provided in the area 607 enclosed by the element substrate 610, the sealing substrate 604, and the sealant 605. The area 607 is filled with a filler material. In some cases, the area 607 is filled with an inert gas (nitrogen, argon, or the like) or with a UV-curing or thermosetting resin that can be used for the sealant 605. For example, a polyvinyl chloride (PVC)-based resin, an acrylic-based resin, a polyimide-based resin, an epoxy-based resin, a silicone-based resin, a polyvinyl butyral (PVB)-based resin, or an ethylene vinyl acetate (EVA)-based resin can be used.Preferably, the sealing substrate is provided with a recessed part and a desiccant is provided in the recessed part, whereby deterioration due to the influence of moisture can be prevented.

[0432] An optical element 621 is provided beneath the sealing substrate 604 to overlap with the light-emitting element 618. An opaque layer 622 is provided beneath the sealing substrate 604. The structures of the optical element 621 and the opaque layer 622 can be identical to the respective structures of the optical element and the opaque layer of embodiment 3.

[0433] An epoxy-based resin or a glass frit is preferably used for the sealant 605. Preferably, such a material allows as little moisture or oxygen to pass through as possible. The sealant substrate 604 can be a glass substrate, a quartz substrate, or a plastic substrate made of fiber-reinforced plastic (FRP), polyvinyl fluoride (PVF), polyester, acrylic, or the like.

[0434] The display device, which includes any of the light-emitting elements and optical elements described in embodiments 1 to 3, can be obtained in the manner described above. <Strukturbeispiel 2 der Anzeigevorrichtung>

[0435] Next, another example of the display device will be given using... Fig. 12A and Fig. 12B as well Fig. 13 described. It should be noted that Fig. 12A and Fig. 12B as well Fig. 13 each represent a cross-sectional view of a display device of an embodiment of the present invention.

[0436] In Fig. Figure 12A shows a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007 and 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral section 1042, a pixel section 1040, a driver circuit section 1041, lower electrodes 1024R, 1024G and 1024B of light-emitting elements, a partition 1025, an EL layer 1028, an upper electrode 1026 of the light-emitting elements, a sealing layer 1029, a sealing substrate 1031, a sealing agent 1032 and the like.

[0437] In Fig. Figure 12A provides examples of the optical elements, i.e., color layers (a red color layer 1034R, a green color layer 1034G, and a blue color layer 1034B), on a transparent base material 1033. An opaque layer 1035 can also be provided. The transparent base material 1033, provided with the color layers and the opaque layer, is positioned on and attached to the substrate 1001. It should be noted that the color layers and the opaque layer are covered with a cover layer 1036. In the structure in Fig. 12A allows red light, green light and blue light to pass through, and therefore an image can be displayed using the pixels of three colors.

[0438] Fig. Figure 12B provides an example in which the color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) are provided as examples of the optical elements between the gate insulating film 1003 and the first intermediate insulating film 1020. Similar to this structure, the color layers can be provided between the substrate 1001 and the sealing substrate 1031.

[0439] Fig. Figure 13 provides an example in which the color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) are provided as examples of the optical elements between the first interlayer insulating film 1020 and the second interlayer insulating film 1021. As with this structure, the color layers can be provided between the substrate 1001 and the sealing substrate 1031.

[0440] The display device described above has a structure in which light is extracted from the side of the substrate 1001 on which the transistors are formed (a bottom-emission structure), but it can have a structure in which light is extracted from the side of the sealing substrate 1031 (a top-emission structure). <Strukturbeispiel 3 der Anzeigevorrichtung>

[0441] Fig. 14A and Fig. Figures 14B are examples of cross-sectional views of a display device with a top-emission structure. It should be noted that Fig. 14A and Fig. 14B each are a cross-sectional view representing the display device of an embodiment of the present invention, and the driver circuit section 1041, the peripheral section 1042 and the like, which are shown in Fig. 12A and Fig. 12B as well Fig. 13 are shown, but are not shown in these.

[0442] In this case, a substrate that does not transmit light can be used as substrate 1001. The process up to the step of forming a connecting electrode that links the transistor and the anode of the light-emitting element is carried out in a similar manner to that of the display device with a bottom-emission structure. Subsequently, a third interlayer insulating film 1037 is formed such that it covers an electrode 1022. This insulating film can have a leveling function. The third interlayer insulating film 1037 can be formed using a material similar to that of the second interlayer insulating film or can be formed using any different other materials.

[0443] The lower electrodes 1024R, 1024G, and 1024B of the light-emitting elements each serve as anodes, but they can also function as cathodes. In the case of a display device with a top-emission structure, as in Fig. 14A and Fig. As shown in Figure 14B, the lower electrodes 1024R, 1024G, and 1024B preferably also have a light-reflecting function. The upper electrode 1026 is provided above the EL layer 1028. Preferably, the upper electrode 1026 has both a light-reflecting and a light-transmitting function, and a microcavity structure is used between the upper electrode 1026 and the lower electrodes 1024R, 1024G, and 1024B, in which case the intensity of the light with a specific wavelength is increased.

[0444] In the case of a top-emissions structure, as in Fig. As shown in Figure 14A, sealing can be carried out using the sealing substrate 1031, on which the color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) are provided. The sealing substrate 1031 can be provided with the opaque layer 1035, which is positioned between pixels. It should be noted that a translucent substrate is advantageously used instead of the sealing substrate 1031.

[0445] Fig. Figure 14A provides an example of the structure provided with the light-emitting elements and the color layers for the light-emitting elements; however, the structure is not limited to this. For example, as shown in Fig. Figure 14B shows a structure that includes the red color layer 1034R and the blue color layer 1034B, but no green color layer, to obtain a full-color display with the three colors, namely red, green, and blue. The structure shown in Fig. The structure shown in Figure 14A, in which the light-emitting elements are provided with the color layers, is effective in suppressing the reflection of external light. In contrast, the structure shown in Fig. The structure shown in Figure 14B, in which the light-emitting elements are provided with the red color layer and the blue color layer, but no green color layer, effectively reduces power consumption due to a low energy loss of the light emitted by the green light-emitting element. <Strukturbeispiel 4 der Anzeigevorrichtung>

[0446] Although a display device containing subpixels of three colors (red, green and blue) has been described above, the number of colors of subpixels can be four (red, green, blue and yellow, or red, green, blue and white). Fig. 15A and Fig. 15B, Fig. 16 as well Fig. 17A and Fig. 17B represent structures of display devices, each incorporating the lower electrodes 1024R, 1024G, 1024B and 1024Y. Fig. 15A and Fig. 15B as well Fig. 16 each represent a display device with a structure in which light is extracted from the side of the substrate 1001 on which transistors are formed (bottom-emission structure), and Fig. 17A and Fig. 17B each represent a display device with a structure in which light is extracted from the ...

Claims

[1] Light-emitting element (150) comprising: a pair of electrodes (101; 102); and a layer (130) between the pair of electrodes (101; 102), wherein the layer (130) comprises a guest material (131) and a host material (132), wherein the guest material (131) can convert a triplet excitation energy into a light emission, wherein the host material (132) comprises a pyrimidine skeleton, a pyridazine skeleton and / or a triazine skeleton, where a HOMO level of the guest material (131) is higher than a HOMO level of the host material (132), where an energy difference between a LUMO level of the guest material (131) and the HOMO level of the guest material (131) is greater than an energy difference between a LUMO level of the host material (132) and the HOMO level of the host material (132), and wherein an energy difference between the LUMO level of the host material (132) and the HOMO level of the guest material (131) is greater than or equal to a transition energy calculated from an absorption edge of an absorption spectrum of the guest material (131). [2] Light-emitting element (150) according to claim 1, wherein the energy difference between the LUMO level of the guest material (131) and the HOMO level of the guest material (131) is greater than the transition energy calculated from the absorption edge of the absorption spectrum of the guest material (131) by 0.4 eV or more. [3] Light-emitting element (150) comprising: a pair of electrodes (101; 102); and a layer (130) between the pair of electrodes (101; 102), wherein the layer (130) comprises a guest material (131) and a host material (132), wherein the guest material (131) can convert a triplet excitation energy into a light emission, wherein the host material (132) comprises a pyrimidine skeleton, a pyridazine skeleton and / or a triazine skeleton, where a HOMO level of the guest material (131) is higher than a HOMO level of the host material (132), where an energy difference between a LUMO level of the guest material (131) and the HOMO level of the guest material (131) is greater than an energy difference between a LUMO level of the host material (132) and the HOMO level of the host material (132), and where an energy difference between the LUMO level of the host material (132) and the HOMO level of the guest material (131) is greater than or equal to a light emission energy of the guest material (131). [4] Light-emitting element (150) according to claim 3, wherein the energy difference between the LUMO level of the guest material (131) and the HOMO level of the guest material (131) is greater than a transition energy calculated from an absorption edge of an absorption spectrum of the guest material (131) by 0.4 eV or more. [5] Light-emitting element (150) according to claim 3, wherein the energy difference between the LUMO level of the guest material (131) and the HOMO level of the guest material (131) is greater than the light emission energy of the guest material (131) by 0.4 eV or more. [6] Light-emitting element (150) according to any one of claims 1 to 5, wherein the host material (132) has a difference between a singlet excitation energy level and a triplet excitation energy level of greater than 0 eV and less than or equal to 0.2 eV. [7] Light-emitting element (150) according to any one of claims 1 to 5, wherein the host material (132) can exhibit thermally activated delayed fluorescence at room temperature. [8] Light-emitting element (150) according to any one of claims 1 to 5, wherein the host material (132) can supply excitation energy to the guest material (131). [9] Light-emitting element (150) according to any one of claims 1 to 5, wherein an emission spectrum of the host material (132) comprises a wavelength range which overlaps with an absorption band on the lowest energy side in an absorption spectrum of the guest material (131). [10] Light-emitting element (150) according to any one of claims 1 to 5, wherein the guest material (131) comprises iridium. [11] Light-emitting element (150) according to any one of claims 1 to 5, wherein the guest material (131) can emit light. [12] Light-emitting element (150) according to any one of claims 1 to 5, wherein the host material (132) can transport an electron and a hole. [13] Light-emitting element (150) according to any one of claims 1 to 5, wherein the host material (132) further comprises a framework with a π-electron-rich heteroaromatic ring and / or an aromatic amine framework. [14] Light-emitting element (150) according to claim 13, wherein the framework with the π-electron-rich heteroaromatic ring comprises an acridine framework, a phenoxazine framework, a phenothiazine framework, a furan framework, a thiophene framework and / or a pyrrole framework.

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