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

Abstract

Light-emitting element (150) comprising: a light-emitting layer (130) comprising a first organic compound and a second organic compound, where the LUMO level of the first organic compound is higher than or equal to the LUMO level of the second organic compound, where the HOMO level of the first organic compound is higher than or equal to the HOMO level of the second organic compound, wherein a combination of the first organic compound and the second organic compound forms an exciplex, the first organic compound is configured to convert triplet excitation energy into light emission, where a lowest triplet excitation level of the second organic compound is higher than or equal to a lowest triplet excitation level of the first organic compound, wherein the lowest triplet excitation level of the first organic compound is higher than or equal to a lowest triplet excitation level of the exciplex, and wherein light emission from the light-emitting layer (130) includes light emission from the first organic compound and light emission from the exciplex.

Description

Background of the invention 1. Field of the invention

[0001] An embodiment of the present invention relates to a light-emitting element, a display device comprising the light-emitting element, an electronic device comprising the light-emitting element, or a lighting device comprising the light-emitting element. 2. Background of the invention

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

[0003] Since the above light-emitting element is a self-luminous type, a display device using this light-emitting element has the following advantages: high visibility, no need for backlighting, and low power consumption. Furthermore, such a light-emitting element is also advantageous in that the element can be manufactured thinly and lightweight, and it has a high response speed.

[0004] In a light-emitting element (e.g., an organic EL element) whose EL layer contains an organic compound as a light-emitting substance and is provided between a pair of electrodes, applying a voltage between the pair of electrodes causes the injection of electrons from a cathode and holes from an anode into the EL layer with a light-emitting property, thereby causing a current to flow. As a result of recombination of the injected electrons and holes, the organic compound with a light-emitting property is excited, resulting in light emission from the excited organic compound with a light-emitting property.

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

[0006] In addition to phosphorescent compounds, thermally activated delayed fluorescence (TADF) materials are known as materials that can convert part of the energy of a triplet excited state into light emission. In a thermally activated delayed fluorescence material, a singlet excited state is formed from a triplet excited state through reverse intersystem crossing, and the singlet excited state is converted into light emission.

[0007] For example, a method is disclosed in which an exciplex formed by two organic compounds and having a small energy difference between a singlet excitation state and a triplet excitation state is used as a thermally activated delayed fluorescent material (see, for example, Patent Document 1). Other exemplary light-emitting elements are disclosed in Patent Documents 2 to 4 and Publication 1. [Reference] [Patent Document 1] JP 2014-45184 A [Patent document 2] DE 11 2012 001 504 T5 [Patent document 3] US 2016 / 0 064 684 A1 [Patent Document 4] WO 2016 / 051 309 A1 [Publication 1] Shi-Jian Su et al.; Organic Electronics 2012, 13(10), 1937-1947. Summary of the invention

[0008] To increase the emission efficiency of a light-emitting element containing a thermally activated, delayed fluorescent material, efficient formation of a singlet excited state from a triplet excited state is preferred. Regarding a light-emitting element using an exciplex as the thermally activated, delayed fluorescent material, the development of a method to further increase the emission efficiency has been called for.

[0009] To obtain multicolored light emission, such as white, from a light-emitting element, it is necessary to cause light-emitting substances of different colors to emit light efficiently at the same time. However, it is difficult to control the light emission to obtain a desired emission color.

[0010] In view of the foregoing, an object of an embodiment of the present invention is to provide a light-emitting element having high emission efficiency. Another object of an embodiment of the present invention is to provide a light-emitting element that emits light in a broad emission spectrum. 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 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.

[0011] It should be noted that the description of the above objects does not preclude the existence of further objects. In one embodiment of the present invention, it is unnecessary to fulfill all of the objects. Further objects will become apparent from the explanation of the description and the like and can be derived therefrom.

[0012] One embodiment of the present invention is a light-emitting element comprising a light-emitting layer. The light-emitting layer comprises a first organic compound and a second organic compound. The first organic compound has a LUMO level higher than or equal to the LUMO level of the second organic compound and has a HOMO level higher than or equal to the HOMO level of the second organic compound. A combination of the first organic compound and the second organic compound forms an exciplex. The first organic compound has a function of converting triplet excitation energy into light emission.The lowest triplet excitation level of the second organic compound is higher than or equal to the lowest triplet excitation level of the first organic compound, and the lowest triplet excitation level of the first organic compound is higher than or equal to the lowest triplet excitation level of the exciplex. Light emission from the light-emitting layer includes light emission from the first organic compound and light emission from the exciplex.

[0013] Another embodiment of the present invention is a light-emitting element comprising a light-emitting layer. The light-emitting layer comprises a first organic compound and a second organic compound. The LUMO level of the first organic compound is higher than or equal to the LUMO level of the second organic compound. The HOMO level of the first organic compound is higher than or equal to the HOMO level of the second organic compound. A combination of the first organic compound and the second organic compound forms an exciplex. The first organometallic compound is an organometallic complex having an absorption band based on a triplet MLCT transition. The lowest triplet excitation level of the second organic compound is higher than or equal to the lowest triplet excitation level of the first organic compound.The lowest triplet excitation level of the first organic compound is higher than or equal to the lowest triplet excitation level of the exciplex. Light emission from the light-emitting layer includes light emission from the first organic compound and light emission from the exciplex.

[0014] In each of the above structures, the intensity ratio of the light emission from the exciplex to the light emission from the first organic compound is preferably in a range of 1:9 to 9:1. The light emission from the exciplex preferably has a higher intensity than the light emission from the first organic compound.

[0015] The light-emitting element having any of the above structures preferably further comprises a third organic compound. The HOMO level of the third organic compound is preferably higher than or equal to the HOMO level of the second organic compound. Furthermore, the third organic compound preferably has a hole-transporting function. Furthermore, the third organic compound preferably comprises a π-electron-rich heteroaromatic framework and / or an aromatic amine framework.

[0016] Furthermore, in each of the above structures, the second organic compound preferably has an electron-transporting function. The second organic compound preferably comprises a π-electron-deficient heteroaromatic framework.

[0017] In each of the above structures, the first organic compound preferably comprises iridium. Furthermore, the first organic compound preferably comprises a ligand coordinated to iridium, and the ligand preferably comprises a five-membered nitrogen-containing heterocyclic framework.

[0018] Another embodiment of the present invention is a display device comprising the light-emitting element having one of the above-described structures and a color filter and / or a transistor. Another embodiment of the present invention is an electronic device comprising the display device and a housing and / or a touch sensor. Another embodiment of the present invention is a lighting device comprising the light-emitting element having one of the above-described structures and a housing and / or a touch sensor. The category of an embodiment of the present invention includes not only a light-emitting device comprising a light-emitting element but also an electronic device comprising a light-emitting device.A light-emitting device in this specification therefore refers to an image display device or a light source (e.g., a lighting device). The light-emitting device may include, in its category, a display module in which a connector such as a flexible printed circuit (FPC) or a tape carrier package (TCP) is connected to a light-emitting element, a display module in which a printed circuit board is provided at the end of a TCP, or a display module in which an integrated circuit (IC) is directly mounted on a light-emitting element by a chip-on-glass (COG) method.

[0019] With one embodiment of the present invention, a light-emitting element with high emission efficiency can be provided. With one embodiment of the present invention, a light-emitting element that emits light in a broad emission spectrum can be provided. With one embodiment of the present invention, a light-emitting element with low power consumption can be provided. With one embodiment of the present invention, a novel light-emitting element can be provided. With one embodiment of the present invention, a novel light-emitting device can be provided. With one embodiment of the present invention, a novel display device can be provided.

[0020] It should be noted that the description of these effects does not preclude the existence of further effects. In one embodiment of the present invention, it is unnecessary to achieve all of the effects listed above. Further effects will become apparent from and can be derived from the explanation of the description, the drawings, the claims, and the like. Short description of the drawings Fig. 1 is a schematic cross-sectional view of a light-emitting element of an embodiment of the present invention. Fig. 2A is a schematic cross-sectional view of a light-emitting layer of a light-emitting element of an embodiment of the present invention, and Fig. 2B and Fig. 2C are diagrams each showing the correlation of energy levels. Fig. 3A is a schematic cross-sectional view of a light-emitting layer of a light-emitting element of an embodiment of the present invention, and Fig. 3B and Fig. 3C are diagrams each showing the correlation of energy levels. Fig. 4A and Fig. 4B are diagrams each illustrating the correlation of energy levels of a light-emitting layer of a light-emitting element of an embodiment of the present invention. Fig. 5 is a schematic cross-sectional view of a light-emitting element of an embodiment of the present invention. Fig. 6 is a schematic cross-sectional view of a light-emitting element of an embodiment of the present invention. Fig. 7A and Fig. 7B are each a schematic cross-sectional view of a light-emitting element of an embodiment of the present invention. Fig. 8A and Fig. 8B are a plan view and a schematic cross-sectional view illustrating a display device of an embodiment of the present invention. Fig. 9A and Fig. 9B are schematic cross-sectional views each illustrating a display device of an embodiment of the present invention. Fig. 10A and Fig. 10B are schematic cross-sectional views each illustrating a display device of an embodiment of the present invention. Fig. 11A to Fig. 11G each illustrates an electronic device of an embodiment of the present invention. Fig. 12A to Fig. 12C are perspective views illustrating a display device of an embodiment of the present invention. Fig. 13 illustrates a lighting device of an embodiment of the present invention. Fig. Figure 14 shows the luminance-current density characteristics of light-emitting elements of an example. Fig. Figure 15 shows the luminance-voltage characteristics of light-emitting elements of an example. Fig. 16 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 17 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 18 shows electroluminescence spectra of light-emitting elements of an example. Fig. 19 shows electroluminescence spectra of light-emitting elements of an example. Fig. Figure 20 shows the luminance-current density characteristics of light-emitting elements of an example. Fig. Figure 21 shows the luminance-voltage characteristics of light-emitting elements of an example. Fig. 22 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 23 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 24 shows electroluminescence spectra of light-emitting elements of an example. Fig. 25 shows electroluminescence spectra of light-emitting elements of an example. Fig. Figure 26 shows emission spectra of a thin film of an example. Fig. Figure 27 shows emission spectra of a thin film of an example. Fig. 28 shows an absorption spectrum of a guest material of an example. Fig. Figure 29 shows the luminance-current density characteristics of light-emitting elements of an example. Fig. 30 shows the luminance-voltage characteristics of light-emitting elements of an example. Fig. 31 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 32 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 33 shows electroluminescence spectra of light-emitting elements of an example. Fig. 34 shows electroluminescence spectra of light-emitting elements of an example. Fig. 35 shows emission spectra of a thin film of an example. Fig. 36 shows emission spectra of a thin film of an example. Fig. 37 shows an absorption spectrum of a guest material of an example. Fig. Figure 38 shows transient emission properties of thin films of an example. Fig. 39 shows a time-resolved emission spectrum of a thin film of an example. Fig. Figure 40 shows emission spectra of thin films of an example. Fig. 41 shows emission spectra of thin films of an example. Fig. Figure 42 shows transient emission properties of thin films of an example. Fig. Figure 43 shows transient emission properties of thin films of an example. Fig. 44 shows an emission spectrum of a thin film of an example. Fig. 45 shows an absorption spectrum of a guest material of an example. Detailed description of the invention

[0021] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following description, and the modes and details can be changed in various ways without departing from the spirit of the present invention. Therefore, the present invention should not be construed as being limited to the contents of the following embodiments.

[0022] Note that the position, size, range, or the like of each structure illustrated in drawings and the like may not be precisely illustrated in some cases for the sake of simplicity. Therefore, the disclosed invention is not necessarily limited to the position, size, range, or the like disclosed in the drawings and the like.

[0023] Note that ordinal numbers such as "first" and "second" are used in this specification and the like for convenience, and they do not indicate the order of steps or the arrangement order of layers. Therefore, for example, an appropriate description can be made even if "first" is replaced with "second" or "third." Furthermore, the ordinal numbers in this specification and the like are not necessarily the same as those specifying an embodiment of the present invention.

[0024] In explaining structures of the invention in this specification and the like with reference to drawings, in some cases, like components in different drawings are generally given the same reference numerals.

[0025] In this description and the like, the terms "film" and "layer" may be interchanged. For example, the term "conductive layer" may be converted to the term "conductive film" if necessary. Likewise, the term "insulating film" may be converted to the term "insulating layer" if necessary.

[0026] In this specification and the like, a singlet excited state (S*) refers to a singlet state with excitation energy. An S1 level means the lowest level of the singlet excitation energy level, that is, the excitation energy level of the lowest singlet excited state (S1 state). A triplet excited state (T*) refers to a triplet state with excitation energy. A T1 level means the lowest level of the triplet excitation energy level, that is, the excitation energy level of the lowest triplet excited state (T1 state). Note that in this specification and the like, simple terms such as a "singlet excited state" and a "singlet excited energy level" in some cases mean the S1 state and the S1 level, respectively. Terms such as "singlet excited state" and "singlet excited energy level" may be used instead of the S1 level. For example, “triplet excited state” and “triplet excited energy level” in some cases refer to the T1 state or the T1 level.

[0027] In this specification and the like, a fluorescent compound refers to a compound that emits light in the visible light range when relaxing from the singlet excited state to the ground state. A phosphorescent compound refers to a compound that emits light in the visible light range at room temperature when relaxing from the triplet excited state to the ground state. That is, a phosphorescent compound refers to a compound that can convert triplet excitation energy into visible light.

[0028] It should be noted that in this specification and the like, “room temperature” means a temperature in the range of higher than or equal to 0 °C and lower than or equal to 40 °C.

[0029] In this specification and the like, a wavelength range of blue refers to a wavelength range greater than or equal to 400 nm and less than 490 nm, and blue light has at least one peak in this wavelength range in an emission spectrum. A wavelength range of green refers to a wavelength range greater than or equal to 490 nm and less than 580 nm, and green light has at least one peak in this wavelength range in an emission spectrum. A wavelength range of red refers to a wavelength range greater than or equal to 580 nm and less than 680 nm, and red light has at least one peak in this wavelength range in an emission spectrum. (Embodiment 1)

[0030] In this embodiment, a light-emitting element of an embodiment of the present invention will be described below with reference to Fig. 1, Fig. 2A to Fig. 2C, Fig. 3A to Fig. 3C and Fig. 4A and Fig. 4B. <Strukturbeispiel 1 des Licht emittierenden Elements>

[0031] First, a structure of a light-emitting element of an embodiment of the present invention will be described below with reference to Fig. 1 described.

[0032] Fig. 1 is a schematic cross-sectional view of a light-emitting element 150 of an embodiment of the present invention.

[0033] The light-emitting element 150 includes 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 includes at least one light-emitting layer 130.

[0034] The EL layer 100, which is Fig. 1, comprises, in addition to the light-emitting layer 130, functional layers such as a hole injection layer 111, a hole transport layer 112, an electron transport layer 118, and an electron injection layer 119.

[0035] Although in this embodiment, a description is given assuming that the electrode 101 and the electrode 102 of the pair of electrodes serve as the anode and the cathode, respectively, the structure of the light-emitting element 150 is not limited to this. That is, the electrode 101 may be a cathode, the electrode 102 may be an anode, and the arrangement order of the layers between the electrodes may 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 may be arranged in this order from the anode side.

[0036] The structure of the EL layer 100 is not limited to the structure shown in Fig. 1, and a structure including 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 may be employed. Alternatively, the EL layer 100 may include, for example, a functional layer capable of lowering a hole-injection barrier or an electron-injection barrier, improving a hole-transport property or an electron-transport property, reducing a hole-transport property or an electron-transport property, or suppressing a quenching effect by an electrode. Note that the functional layers may each be a single layer or a multilayer. <Lichtemissionsmechanismus 1 des Licht emittierenden Elements>

[0037] Next, the light emission mechanism of the light-emitting layer 130 will be described below.

[0038] Fig. 2A is a schematic cross-sectional view showing an example of the light-emitting layer 130 in Fig. 1. The light-emitting layer 130, which in Fig. 2A, contains a guest material 131 and a host material 132.

[0039] In the light-emitting element 150 of one 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 anode, respectively, into the EL layer 100, causing a current to flow. Excitons are formed by recombination of the injected electrons and holes. The ratio of singlet excitons to triplet excitons (hereinafter referred to as exciton generation probability) generated by the recombination of charge carriers (electrons and holes) is approximately 1:3 according to the statistically obtained probability.In other words, the probability of generating singlet excitons is 25%, and the probability of generating triplet excitons is 75%; thus, it is important that triplet excitons contribute to light emission to increase the emission efficiency of the light-emitting element.

[0040] Accordingly, a material having a function of converting triplet excitation energy into light emission is preferably used for the light-emitting material used in the light-emitting layer 130. Among compounds having a light-emitting property, a compound capable of emitting phosphorescence (hereinafter also referred to as a phosphorescent compound) has a function of converting triplet excitation energy into light emission. Accordingly, a phosphorescent compound is preferably used for the light-emitting material of the light-emitting element 150.

[0041] When using a phosphorescent compound as the light-emitting material in the light-emitting layer 130, the T1 level of the phosphorescent compound is preferably lower than the T1 level of another material (host material 132 or the like) included in the light-emitting layer 130. Consequently, quenching of the triplet excitation energy of the phosphorescent compound is less likely to occur, allowing efficient light emission from the phosphorescent compound.

[0042] As a material capable of converting triplet excitation energy into light emission, a thermally activated delayed fluorescent (TADF) material can be specified, in addition to the phosphorescent compound. Note that the thermally activated delayed fluorescent material is a material that has a small difference between the S1 level and the T1 level and has the function of converting triplet excitation energy into singlet excitation energy through reverse intersystem crossing. Thus, the TADF material can upconvert triplet excitation energy into singlet excitation energy using a small amount of thermal energy (i.e., reverse intersystem crossing is possible) and efficiently emit light (fluorescence) from the singlet excited state.The exciplex, which forms an excited state of two types of substances, serves as a thermally activated, delayed fluorescent material capable of converting part of the triplet excitation energy into light emission. Thus, an exciplex is preferably used as the light-emitting material of the light-emitting element 150.

[0043] In the case of using an exciplex for the light-emitting material in the light-emitting layer 130, the T1 level of the exciplex is preferably lower than the T1 level of another material (host material 132 or the like) included in the light-emitting layer 130. Consequently, quenching of the triplet excitation energy of the exciplex is less likely to occur, whereby reverse intersystem crossing of the triplet excitation energy due to the exciplex and subsequent light emission from the singlet excitation energy can be efficiently obtained.

[0044] Due to the above relationship between energy levels, it is difficult to use a phosphorescent compound and an exciplex as light-emitting materials in the light-emitting layer 130 and efficiently obtain light emission from both the phosphorescent compound and the exciplex. However, the present inventors have found that when a phosphorescent compound is used as the guest material 131 and an exciplex is formed by the guest material 131 and the host material 132, light can be efficiently extracted from both the exciplex and the guest material 131. <Energieübertragungsmechanismus>

[0045] Here, factors that govern the processes of intermolecular energy transfer are described. Two mechanisms have been proposed for intermolecular energy transfer: the Förster mechanism (dipole-dipole interaction) and the Dexter mechanism (electron exchange interaction). Here, an energy transfer process is described between molecules of the first material in an excited state and the second material in a ground state; the same can also apply to the case where one of them is an exciplex. <<Förster-Mechanismus> >

[0046] In the Förster mechanism, energy transfer does not require direct contact between molecules, and energy is transferred through a resonance phenomenon of dipole vibration between a first material and a second material. Through the resonance phenomenon of dipole vibration, the first material transfers energy to the second material, and thus the first material, which is in an excited state, is brought to a ground state, and the second material, which is in a ground state, is brought to an excited state. Note that the rate constant k h*→g of the Förster mechanism is represented by formula (1). kh∗→g=9000c4K2ϕIn10128π5n4NτR6∫f′h(v)εgvv4dv

[0047] In formula (1) v represents a frequency, f' h(v) represents a normalized emission spectrum of the first material (a fluorescence spectrum upon energy transfer from a singlet excited state, and a phosphorescence spectrum upon energy transfer from a triplet excited state), ε g (v) represents a molar absorption coefficient of the second material, N represents the Avogadro number, n represents a refractive index of a medium, R represents an intermolecular distance between the first material and the second material, τ represents a measured lifetime of an excited state (fluorescence lifetime or phosphorescence lifetime), c represents the speed of light, ϕ represents an emission quantum yield (a fluorescence quantum yield upon energy transfer from a singlet excited state, and a phosphorescence quantum yield upon energy transfer from a triplet excited state), and K 2represents a coefficient (0 to 4) for the orientation of a transition dipole moment between the first material and the second material. It should be noted that for arbitrary orientation K 2 = 2 / 3 applies. < <dexter-mechanismus>>

[0048] In the Dexter mechanism, the first material and the second material are near a contact-effective region where their orbitals overlap, and the first material, which is in an excited state, and the second material, which is in a ground state, exchange their electrons, resulting in energy transfer. Note that the rate constant k h*→g of the Dexter mechanism is represented by formula (2). kh∗→g=(2πh)K2exp(−2RL)∫f′h(v)ε′g(v)dv

[0049] In formula (2), h represents a Planck constant, K represents a constant with an energy dimension, v represents a frequency, f' h (v) represents a normalized emission spectrum of the first material (the fluorescence spectrum upon energy transfer from a singlet excited state, and the phosphorescence spectrum upon energy transfer from a triplet excited state), ε' g (v) represents a normalized absorption spectrum of the second material, L represents an effective molecular radius, and R represents an intermolecular distance between the first material and the second material.

[0050] Here, the efficiency of energy transfer from the first material to the second material (energy transfer efficiency ϕ ET ) is represented by formula (3). In the formula, k r a rate constant of a light emission process (fluorescence during energy transfer from a singlet excited state, and phosphorescence during energy transfer from a triplet excited state) of the first material, k n represents a rate constant of a process without light emission (thermal deactivation or intersystem crossing) of the first material, and τ represents a measured lifetime of an excited state of the first material. ϕET=kh∗→gkr+kn+kh∗→g=kh*→g(1τ)+kh*→g

[0051] According to formula (3), it has been found that the energy transfer efficiency ϕ ET by increasing the rate constant k h*→g in the energy transfer can be increased, so that another competing rate constant k r + k n (= 1 / τ) becomes relatively small. <<Anregungsenergieübertragung auf einen Exciplex> >

[0052] First, energy transfer through the Förster mechanism is considered. If formula (1) is substituted into formula (3), τ can be eliminated. Thus, in the Förster mechanism, the energy transfer efficiency ϕ ET does not depend on the lifetime τ of the excited state of the first material. Furthermore, it can be stated that a high energy transfer efficiency ϕ ET is obtained when the emission quantum yield ϕ (the fluorescence quantum yield in energy transfer from a singlet excited state, and the phosphorescence quantum yield in energy transfer from a triplet excited state) is high.

[0053] Furthermore, the emission spectrum (the fluorescence spectrum during energy transfer from a singlet excited state, and the phosphorescence spectrum during energy transfer from a triplet excited state) of the first material preferably overlaps largely with the absorption spectrum (absorption corresponding to the transition from the singlet ground state to the singlet excited state) of the second material. Furthermore, it is preferred that the molar absorption coefficient of the second material also be high. This means that the emission spectrum of the first material overlaps with the absorption band of the second material, which is located on the longest wavelength side.It should be noted that when using an exciplex as the second material, the molar absorption coefficient of the second material can be ignored, since a direct transition from a singlet ground state to a singlet excited state, as well as a direct transition from a singlet ground state to a triplet excited state, is forbidden. Thus, the excitation energy transfer process from the first material to the second material through the Förster mechanism can be ignored.

[0054] Next, energy transfer through the Dexter mechanism is considered. To determine the rate constant k h*→g To increase the energy transfer efficiency, according to formula (2), the emission spectrum (the fluorescence spectrum during energy transfer from a singlet excited state, and the phosphorescence spectrum during energy transfer from a triplet excited state) of the first material preferably overlaps largely with an absorption spectrum (absorption corresponding to the transition from a singlet ground state to a singlet excited state) of the second material. Accordingly, the energy transfer efficiency can be optimized by ensuring that the emission spectrum of the first material overlaps with the absorption band of the second material located on the longest wavelength side.In this case, too, if an exciplex is used as the second material, the absorption spectrum of the second material can be ignored, since a direct transition from a singlet ground state to a singlet excited state, as well as a direct transition from a singlet ground state to a triplet excited state, is forbidden. Thus, the excitation energy transfer process from the first material to the second material through the Dexter mechanism can be ignored.

[0055] Thus, in case of using an exciplex as the second material, energy transfer occurs neither through the Förster mechanism nor through the Dexter mechanism in the energy transfer process from the first material to the second material. <<Korrelation von Energieniveaus> >

[0056] In one embodiment of the present invention, the guest material 131 is preferably a phosphorescent compound. A structure using a phosphorescent compound as the guest material 131 is described below. The guest material 131 may also be referred to as a phosphorescent compound.

[0057] Furthermore, the combination of the guest material 131 and the host material 132 contained in the light-emitting layer 130 preferably forms an exciplex.

[0058] As long as the combination of the guest material 131 and the host material 132 can form an exciplex, it is acceptable; however, preferably, one of them is a compound with a function of transporting holes (a hole-transport property) and the other is a compound with a function of transporting electrons (an electron-transport property). In this case, a donor-acceptor exciplex is easily formed; thus, an exciplex can be formed efficiently. In the case where the combination of the guest material 131 and the host material 132 is a combination of a compound with a hole-transport property and a compound with an electron-transport property, the carrier balance can be easily controlled by adjusting their mixing ratio.In particular, the weight ratio of the compound having a hole transport property to the compound having an electron transport property 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.

[0059] To efficiently form an exciplex, the combination of the guest material and the host material preferably satisfies the following: the highest occupied molecular orbital (also referred to as HOMO (highest occupied molecular orbital)) level of the guest material 131 or the host material 132 is higher than the HOMO level of the other of the guest material 131 and the host material 132, and the lowest unoccupied molecular orbital (also referred to as LUMO (lowest unoccupied molecular orbital)) level of the guest material 131 or the host material 132 is higher than the LUMO level of the other of the guest material 131 and the host material 132.

[0060] It should be noted that the LUMO levels and HOMO levels of the compounds can be obtained from the electrochemical properties (reduction potentials and oxidation potentials) of the compounds measured by cyclic voltammetry (CV).

[0061] For example, in the case where the guest material 131 has a hole transport property and the host material 132 has an electron transport property, the HOMO level of the guest material 131 is preferably higher than the HOMO level of the host material 132, and the LUMO level of the guest material 131 is preferably higher than the LUMO level of the host material 132, as shown in the energy band diagram in Fig. 2B. Specifically, the energy difference between the HOMO level of the guest material 131 and the HOMO level of the host material 132 is preferably 0.1 eV or more, more preferably 0.2 eV or more, or even more preferably 0.3 eV or more. Furthermore, the energy difference between the LUMO level of the guest material 131 and the LUMO level of the host material 132 is preferably 0.1 eV or more, more preferably 0.2 eV or more, or even more preferably 0.3 eV or more. Such an energy difference is suitable because electrons and holes injected from the pair of electrodes (the electrode 101 and the electrode 102) are easily injected into the guest material 131 and the host material 132.

[0062] It should be noted that in Fig. 2B "Guest (131)" represents the guest material 131, "Host (132)" represents the host material 132, ΔE G represents the energy difference between the LUMO level and the HOMO level of the guest material 131, ΔE H1 represents the energy difference between the LUMO level and the HOMO level of the host material 132, and ΔE Ex represents the energy difference between the LUMO level of the host material 132 and the HOMO level of the guest material 131.

[0063] Furthermore, in this case, an exciplex formed by the guest material 131 and the host material 132 has the HOMO in the guest material 131 and the LUMO in the host material 132. The excitation energy of the exciplex essentially corresponds to the energy difference between the LUMO level of the host material 132 and the HOMO level of the guest material 131 (ΔE Ex ) and is smaller than the energy difference between the LUMO level and the HOMO level of the guest material 131 (ΔE G ) and smaller than the energy difference between the LUMO level and the HOMO level of the host material 132 (ΔE H1 ). Thus, when the guest material 131 and the host material 132 form an exciplex, an excited state with a lower excitation energy can be formed. Furthermore, a stable excited state can be formed because the exciplex has an energy corresponding to the lower excitation energy.

[0064] Fig. Figure 2C shows a correlation of energy levels of the guest material 131 and the host material 132 in the light-emitting layer 130. The following clarifies what terms and symbols in Fig. 2C represent: Guest (131): the guest material 131 (phosphorescent compound); Host (132): the host material 132; S G : an S1 level of guest material 131; T G : a T1 level of guest material 131; S H1 : an S1 level of the host material 132; T H1 : a T1 level of host material 132; S E : an S1 level of the exciplex; and T E : a T1 level of the exciplex.

[0065] In the light-emitting element of one embodiment of the present invention, an exciplex is formed by the guest material 131 and the host material 132 contained in the light-emitting layer 130. The S1 level of the exciplex (S E ) and the T1 level of the exciplex (T E ) are close to each other (see route E1 in Fig. 2C).

[0066] An exciplex is an excited state formed by two types of substances. Under light excitation, the exciplex is formed by the interaction between a substance in an excited state and another substance in a ground state that are close to each other. The two types of substances that formed the exciplex return to a ground state by emitting light, and then they serve as the original two types of substances again. Under electrical excitation, when one substance is brought into an excited state, it immediately interacts with the other substance that is close to it to form an exciplex. Alternatively, one substance receives a hole and the other substance receives an electron, and they interact with each other to readily form an exciplex. Since the excitation energy levels (S E and T E ) of the exciplex is lower than the S1 levels (S G and S H1 ) of the substances (the guest material 131 and the host material 132) forming the exciplex, the excited state can be formed with lower excitation energy. Accordingly, the drive voltage of the light-emitting element 150 can be reduced.

[0067] Since the S1 level and the T1 level of the exciplex (S E and T E ) are close to each other, the exciplex has a function to emit thermally activated delayed fluorescence. In other words, the exciplex has a function to convert triplet excitation energy into singlet excitation energy by reverse intersystem crossing (upconversion) (see route E2 in Fig. 2C). Thus, part of the triplet excitation energy generated in the light-emitting layer 130 is converted into singlet excitation energy by the exciplex. To achieve this conversion, the energy difference between the S1 level and the T1 level of the exciplex (S E and T E ) 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. It should be noted that the T1 level of the exciplex (T E ) is preferably lower than the T1 levels of the substances forming an exciplex (the guest material 131 and the host material 132) (T G and T H1 ) to efficiently induce reverse intersystem crossing. Thus, the probability of quenching of the triplet excitation energy of the exciplex due to the guest material 131 and the host material 132 is reduced, leading to the efficient induction of reverse intersystem crossing.

[0068] Furthermore, the exciplex exists only in one excited state, and the excitation energy levels (S E and T E ) of the exciplex are only present in a state in which an exciplex is formed; thus, a direct transition from the ground state of the substances (guest material 131 and host material 132) forming the exciplex to the excited state of the exciplex does not occur. Consequently, an excitation energy transfer does not occur either from the excitation energy levels (S G and T G ) of the guest material 131 itself nor from the excitation energy levels (S H1 and T H1 ) of the host material 132 itself on the excitation energy levels (S E and T E ) of the exciplex. Thus, light can be efficiently extracted from both the exciplex and the guest material 131 by adequately controlling the generation probability of the exciplex formed by the guest material 131 and the host material 132.

[0069] Thus, the T1 level (T H1 ) of the host material 132 is preferably higher than or equal to the T1 level (T G ) of the guest material 131. Furthermore, the T1 level (T G ) of the guest material 131 preferably higher than or equal to the T1 level (T E ) of the exciplex formed by the guest material 131 and the host material 132. Thus, the probability of quenching of the excitation energy of the exciplex formed by the guest material 131 and the host material 132 is lower, whereby reverse intersystem crossing from the triplet excitation energy to the singlet excitation energy due to the exciplex and subsequent light emission from the singlet excitation energy can be efficiently obtained. Furthermore, since quenching of the excitation energy of the guest material 131 is also less likely to occur, efficient light emission from the guest material 131 can be obtained, as described above.

[0070] Furthermore, a process for forming the exciplex by the guest material 131 and the host material 132 is less likely to occur when the direct charge carrier recombination process dominates in the guest material 131. Thus, it is preferable that the process in which charge carriers recombine directly and the process in which energy is transferred via the exciplex generation process (routes E1 and E2 in Fig. 2C), with a desired probability in the guest material 131. Furthermore, the weight ratio of the guest material 131 to the host material 132 is preferably low, particularly preferably greater than or equal to 0.01 and less than or equal to 0.5, more preferably greater than or equal to 0.05 and less than or equal to 0.3.

[0071] By extracting light from the guest material 131 and light from the exciplex formed by the guest material 131 and the host material 132 in a desired ratio, the color of the light emitted by the light-emitting element can be controlled. For example, the ratio of the light emission from the guest material 131 to the light emission from the exciplex formed by the guest material 131 and the host material 132 can be adjusted so that the color of the light emitted by the light-emitting element is white or almost white; specifically, the ratio of the light emission from the guest material 131 to the light emission from the exciplex formed by the guest material 131 and the host material 132 is preferably 1:9 to 9:1, and more preferably 1:5 to 5:1. It should be noted that the light emission from the light-emitting element may include further light emission.

[0072] It should be noted that a structure may be used in which the guest material 131 has an electron transport property and the host material 132 has a hole transport property. In this case, the HOMO level of the host material 132 is preferably higher than the HOMO level of the guest material 131, and the LUMO level of the host material 132 is preferably higher than the LUMO level of the guest material 131, as shown in the energy band diagram in Fig. 4A shown. <Lichtemissionsmechanismus 2 des Licht emittierenden Elements>

[0073] Next, a structural example different from that of the light-emitting layer used in Fig. 2A, is shown, in the following by means of Fig. 3A described.

[0074] Fig. 3A is a schematic cross-sectional view showing an example of the light-emitting layer 130 in Fig. 1. The light-emitting layer 130 in Fig. 3A includes the guest material 131, the host material 132 and a host material 133.

[0075] In the light-emitting layer 130, the host material 132 or the host material 133 is present in the highest weight fraction, and the guest material 131 is dispersed in the host material 132 or the host material 133. Here, the guest material 131 is preferably a phosphorescent compound. Furthermore, the combination of the guest material 131 and the host material 132 preferably forms an exciplex.

[0076] In order to efficiently form an exciplex, the combination of the host materials preferably satisfies the following: The HOMO level of one of the guest material 131 and the host material 132 is the highest among the materials in the light-emitting layer 130, and the LUMO level of the other is the lowest in the light-emitting layer 130. In other words, the HOMO level of one of the guest material 131 and the host material 132 is preferably higher than the HOMO level of the other of the guest material 131 and the host material 132 and higher than the HOMO level of the host material 133, and the LUMO level of the other of the guest material 131 and the host material 132 is preferably lower than the LUMO level of one of the guest material 131 and the host material 132 and lower than the LUMO level of host material 133. Thus, a reaction to form an exciplex can be inhibited by host material 132 and host material 133.

[0077] For example, in the case where the guest material 131 has a hole transport property and the host material 132 has an electron transport property, the HOMO level of the guest material 131 is preferably higher than the HOMO level of the host material 132 and the HOMO level of the host material 133, and the LUMO level of the host material 132 is preferably lower than the LUMO level of the guest material 131 and the LUMO level of the host material 133, as shown in the energy band diagram in Fig. 3B. In this case, the LUMO level of the host material 133 can be higher or lower than the LUMO level of the guest material 131. Furthermore, the HOMO level of the host material 133 can be higher or lower than the HOMO level of the host material 132.

[0078] It should be noted that in Fig. 3B "Guest (131)" represents the guest material 131, "Host (132)" represents the host material 132, "Host (133)" represents the host material 133, ΔE G represents the energy difference between the LUMO level and the HOMO level of the guest material 131, ΔE H1 represents the energy difference between the LUMO level and the HOMO level of the host material 132, ΔE H2 represents the energy difference between the LUMO level and the HOMO level of the host material 133, and ΔE Ex represents the energy difference between the LUMO level of the host material 132 and the HOMO level of the guest material 131.

[0079] Furthermore, in this case, the excitation energy of the exciplex formed by the guest material 131 and the host material 132 essentially corresponds to the energy difference between the LUMO level of the host material 132 and the HOMO level of the guest material 131 (ΔE Ex ) and is preferably smaller than the energy difference between the LUMO level and the HOMO level of the host material 133 (ΔE H2 ).

[0080] Fig. Figure 3C shows the correlation between energy levels of the guest material 131, the host material 132 and the host material 133 in the light-emitting layer 130, which is Fig. 3A. The following explains what terms and symbols in Fig. 3C represent: Guest (131): the guest material 131 (phosphorescent compound); Host (132): the host material 132; Host (133): the host material 133; S G : an S1 level of guest material 131; T G : a T1 level of guest material 131; S H1 : an S1 level of the host material 132; T H1 : a T1 level of host material 132; S H2 : an S1 level of the host material 133; T H2 : a T1 level of host material 133; S E : an S1 level of the exciplex; and T E : a T1 level of the exciplex.

[0081] In the light-emitting element of one embodiment of the present invention, an exciplex is formed by the guest material 131 and the host material 132 contained in the light-emitting layer 130. The S1 level of the exciplex (S E ) and the T1 level of the exciplex (T E ) are close to each other (see route E1 in Fig. 3C).

[0082] The T1 level (T H1 ) of the host material 132 and the T1 level (T H2 ) of the host material 133 are preferably higher than or equal to the T1 level (T G ) of the guest material 131. Furthermore, the T1 level (T G ) of the guest material 131 preferably higher than or equal to the T1 level (T E ) of the exciplex formed by the guest material 131 and the host material 132. Thus, the probability of quenching of the excitation energy of the exciplex formed by the guest material 131 and the host material 132 is lower, whereby reverse intersystem crossing from the triplet excitation energy to the singlet excitation energy due to the exciplex and subsequent light emission from the singlet excitation energy can be efficiently obtained. Furthermore, since quenching of the excitation energy of the guest material 131 is also less likely to occur, efficient light emission from the guest material 131 can be obtained.

[0083] It should be noted that a process for forming the exciplex by the guest material 131 and the host material 132 is less likely to occur when the direct charge carrier recombination process dominates in the guest material 131. Thus, it is preferable that the process in which charge carriers recombine directly and the process in which energy is transferred via the exciplex generation process (routes E1 and E2 in Fig. 3C), with a desired probability in the guest material 131. Accordingly, another material is preferably added to the light-emitting layer 130 in addition to the guest material 131 and the host material 132. In other words, by using the host material 133 in the light-emitting layer 130 in addition to the guest material 131 and the host material 132, the generation probability of the exciplex formed by the guest material 131 and the host material 132 can be adequately controlled. Furthermore, the weight of the guest material 131 to the total weight of the host material 132 and the host material 133 is preferably low, particularly preferably greater than or equal to 0.01 and less than or equal to 0.5, more preferably greater than or equal to 0.05 and less than or equal to 0.3.

[0084] It should be noted that a structure may be used in which the guest material 131 has an electron transport property and the host material 132 has a hole transport property. In this case, the HOMO level of the host material 132 is preferably higher than the HOMO level of the guest material 131 and the HOMO level of the host material 133, and the LUMO level of the guest material 131 is preferably lower than the LUMO level of the host material 132 and the LUMO level of the host material 133, as shown in the energy band diagram in Fig. 4B. In this case, the LUMO level of the host material 133 may be higher or lower than the LUMO level of the host material 132. Furthermore, the HOMO level of the host material 133 may be higher or lower than the HOMO level of the guest material 131. <material>

[0085] Next, components of a light-emitting element of an embodiment of the present invention will be described in detail below. <<Licht emittierende Schicht> >

[0086] Materials that can be used for the light-emitting layer 130 are described below.

[0087] As long as the combination of the guest material 131 and the host material 132 can form an exciplex, there is no particular limitation; however, it is preferable that one of them has a function of transporting electrons and the other has a function of transporting holes.

[0088] When the host material 132 has a hole transporting function, the host material 132 preferably comprises a π-electron-rich heteroaromatic framework and / or an aromatic amine framework.

[0089] As the π-electron-rich heteroaromatic skeleton contained in the host material 132, one or more of a furan skeleton, a thiophene skeleton, and a pyrrole skeleton are preferable due to their high stability and reliability. As the furan skeleton, a dibenzofuran skeleton is preferable. As the thiophene skeleton, a dibenzothiophene skeleton is preferable. Note that as the pyrrole skeleton, an indole skeleton or a carbazole skeleton, particularly a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton, is preferable. Each of these skeletons may further have a substituent.

[0090] As the aromatic amine skeleton contained in the host material 132, a tertiary amine that does not contain an NH bond, particularly a triarylamine skeleton, is preferably used. As the aryl group of a triarylamine skeleton, a substituted or unsubstituted aryl group having 6 to 13 carbon atoms arranged in a ring is preferably used, and examples thereof include a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, a triphenylenyl group, and the like.

[0091] A structure comprising a π-electron-rich heteroaromatic framework and an aromatic amine framework, which exhibits excellent hole-transport properties and is thus stable and highly reliable, is particularly preferable. An example of such a structure is a structure comprising a carbazole framework and an arylamine framework.

[0092] As examples of the above-described π-electron-rich heteroaromatic skeleton and the above-described aromatic amine skeleton, skeletons represented by the following general formulas (101) to (117) are given. Note that X in the general formulas (115) to (117) represents an oxygen atom or a sulfur atom.

[0093] Furthermore, when the host material 132 has a function of transporting electrons, the host material 132 preferably comprises a π-electron-deficient heteroaromatic framework. As the π-electron-deficient heteroaromatic framework, a pyridine framework, a diazine framework (a pyrimidine framework, a pyrazine framework, or a pyridazine framework), or a triazine framework is preferable; in particular, the diazine framework or the triazine framework is preferable due to its high stability and reliability.

[0094] As examples of the π-electron-deficient heteroaromatic framework described above, frameworks represented by the following general formulas (201) to (218) are given. Note that X in general formulas (209) to (211) represents an oxygen atom or a sulfur atom.

[0095] Alternatively, a compound in which a framework with a hole-transporting property (e.g., a π-electron-rich heteroaromatic framework and / or an aromatic amine framework) and a framework with an electron-transporting property (e.g., a π-electron-poor heteroaromatic framework) are bonded directly or via an arylene group can be used. Examples of the arylene group include a phenylene group, a biphenyldiyl group, a naphthalenediyl group, a fluorenediyl group, and the like.

[0096] As examples of a bonding group that bonds the above framework having a hole transport property and the above framework having an electron transport property to each other, frameworks represented by the following general formulas (301) to (315) are given.

[0097] The above aromatic amine skeleton (e.g., the triarylamine skeleton), the above π-electron-rich heteroaromatic skeleton (e.g., a ring comprising the furan skeleton, the thiophene skeleton, or the pyrrole skeleton), the above π-electron-deficient heteroaromatic skeleton (e.g., a ring comprising the diazine skeleton or the triazine skeleton), or the above general formulas (101) to (117), general formulas (201) to (218), and general formulas (301) to (315) may each have a substituent. An alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms can also be selected as the substituent.Specific examples of the alkyl group having 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 having 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 having 6 to 12 carbon atoms include a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted biphenyl group, and the like. The above substituents may be bonded to each other to form a ring.For example, in the case where a carbon atom at the 9-position in a fluorene skeleton has two phenyl groups as substituents, the phenyl groups are bonded to each other to form a spirofluorene skeleton. It should be noted that an unsubstituted group is advantageous in that it is easy to synthesize and its raw material is inexpensive.

[0098] Furthermore, Ar represents a single-bonded arylene group or an arylene group having 6 to 13 carbon atoms. The arylene group may contain one or more substituents, and the substituents may be bonded to each other to form a ring. For example, a carbon atom at the 9-position in a fluorenyl group has two phenyl groups as substituents, and the phenyl groups are bonded to each other to form a spirofluorene skeleton. Specific examples of the arylene group having 6 to 13 carbon atoms include a phenylene group, a naphthalenediyl group, a biphenyldiyl group, a fluorenediyl group, and the like. In the case where the arylene group has a substituent, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms can also be selected as the substituent.Specific examples of the alkyl group having 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 having 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 having 6 to 12 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and the like.

[0099] For example, the arylene group represented by Ar can be represented by groups represented by the following structural formulas (Ar-1) to (Ar-18). Note that the group that can be used for Ar is not limited to these.

[0100] Furthermore, R 1 and R 2 each independently represents hydrogen, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 13 carbon atoms. Specific examples of the alkyl group having 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 having 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 having 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.The above aryl group or phenyl group may include one or more substituents, and the substituents may be bonded to each other to form a ring. An alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms can also be selected as the substituent. Specific examples of the alkyl group having 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 having 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 having 6 to 12 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and the like.

[0101] For example, groups represented by the following structural formulas (R-1) to (R-29) can be used as an alkyl group or aryl group represented by R 1 and R 2 It should be noted that the group that can be used as an alkyl group or aryl group is not limited to this.

[0102] As a substituent present in the general formulas (101) to (117), the general formulas (201) to (218), the general formulas (301) to (315), Ar, R 1 and R 2 For example, the alkyl group or the aryl group represented by the above structural formulas (R-1) to (R-24) can be used. Note that the group that can be used as the alkyl group or the aryl group is not limited to these.

[0103] For example, any of the following hole transport materials and electron transport materials can be used as the host material 132.

[0104] A material with a property of transporting more holes than electrons can be used as a hole transport material, whereby 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, or the like can be used. Furthermore, the hole-transporting material can be a high-molecular compound.

[0105] Examples of the material having a high hole-transport property include aromatic amine compounds such as 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,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD), 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B) and the like.

[0106] Specific examples of the carbazole derivatives include 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.

[0107] Other examples of the carbazole derivatives include 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), 1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene and the like.

[0108] Examples of the material with a high hole transport property 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: m-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), 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(dibenzothiophen-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). The substances listed here are mainly those with a hole mobility of 1 × 10, -6 cm 2 / Vs or higher. Note that, in addition to these substances, any substance that has the property of transporting more holes than electrons can be used.

[0109] A material with a property of transporting more electrons than holes can be used as an electron transport material, whereby a material with an electron mobility of 1 × 10 -6 cm 2 / Vs or higher is preferable. A π-electron-deficient heteroaromatic compound, such as a nitrogen-containing heteroaromatic compound, or a zinc- or aluminum-based metal complex can be used as a material that readily accepts electrons (the material having an electron-transport property). Examples of the metal complex include a metal complex having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, and a thiazole ligand. Further, as the π-electron-deficient heteroaromatic compound, there can be given an oxadiazole derivative, a triazole derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, a triazine derivative, and the like.

[0110] Examples include metal complexes having a quinoline skeleton or a benzoquinoline skeleton, such as tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), and the like. A metal complex having an oxazole-based or thiazole-based ligand, such as tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Alq3), bis(10-hydroxybenzo[h]quinolinolato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), and the like. B. Bis[2-(2-benzoxazolyl)phenolate]zinc(II) (abbreviation: ZnPBO) or bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ) can be used alternatively. In addition to such metal complexes, any of the following materials can be used: heterocyclic compounds, such as2-(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), 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), bathocuproine (abbreviation: BCP) and 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen); heterocyclic compounds with a diazine skeleton, 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), 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 skeleton, such as3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy) and 1,3,5-tris[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB); and heteroaromatic compounds such as 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs). A high-molecular compound such as Poly(2,5-pyridinediyl) (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 also be used as an alternative. The substances mentioned here are mainly those with an electron mobility of 1 × 10 -6 cm 2 / Vs or higher. However, any substance other than those described above may also be used, as long as it is a substance whose electron-transport property is higher than its hole-transport property.

[0111] The guest material 131 preferably has a function for converting triplet excitation energy into light emission. In the case where 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 a spin angular momentum and an orbital angular momentum of an electron), and a transition between a singlet ground state and a triplet excited state of the guest material 131 is enabled. Consequently, the emission efficiency and absorption probability related to the transition between the singlet ground state and the triplet excited state of the guest material 131 can be increased.Accordingly, the guest material 131 preferably contains a metal element with a large spin-orbit interaction, particularly a platinum group element (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), or platinum (Pt)). Iridium is particularly preferred because it can increase the transition probability, which involves the direct transition between a singlet ground state and a triplet excited state.

[0112] As the guest material 131 (phosphorescent compound), an iridium-, rhodium-, or platinum-based organometallic complex or metal complex can be used. Furthermore, a platinum complex with a porphyrin ligand, an organoiridium complex, and the like can be cited; particularly, an organoiridium complex, such as an iridium-based ortho-metalated complex, is preferred. As the ortho-metalated ligand, 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 can be cited. In this case, the guest material 131 (phosphorescent compound) exhibits an absorption band based on a triplet MLCT (metal to ligand charge transfer) transition.

[0113] Examples of the substance exhibiting an emission peak in the blue or green wavelength range include organometallic iridium complexes having a 4H-triazole skeleton, such as: B. Tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phe nyl-κC}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 1H-triazole framework, 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 framework, such asfac-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 above-mentioned materials, organometallic iridium complexes comprising a five-membered nitrogen-containing heterocyclic framework, such as a 4H-triazole framework, a 1H-triazole framework, or an imidazole framework, exhibit high triplet excitation energy, reliability, and emission efficiency and are therefore particularly preferred.

[0114] Examples of the substance that exhibits an emission peak in the green or yellow wavelength range include organometallic iridium complexes with a pyrimidine skeleton, such asTris(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]p henyl-κC}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 framework, 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 listed above, the organometallic iridium complexes with a pyrimidine framework exhibit very high reliability and very high emission efficiency and are therefore particularly preferred.

[0115] Examples of the substance exhibiting an emission peak in the yellow or red wavelength range include organometallic iridium complexes having a pyrimidine skeleton, 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 having a pyrazine skeleton, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: Ir(5mdppm)2(dpm)). 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 framework, 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-propanedionato)(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 listed above, organometallic iridium complexes with a pyrimidine framework exhibit very high reliability and very high emission efficiency and are therefore particularly preferred. Furthermore, organometallic iridium complexes with a pyrazine framework can exhibit red light emission with favorable chromaticity.

[0116] Although there is no particular limitation on a material that can be used as the host material 133 in the light-emitting layer 130, for example, any of the following materials can be used: metal complexes such as; B. Tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(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 B. 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. B. 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or a-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). In addition, condensed polycyclic aromatic compounds such as anthracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives, and dibenzo[g,p]chrysene derivatives can be given, and specific examples include 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'''-Octaphenyldibenzo[g,p]chrysene-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'-(Stilbene-3,3'-diyl)diphenanthrene (Abbreviation: DPNS), 9,9'-(Stilbene-4,4'-diyl)diphenanthrene (Abbreviation: DPNS2), 3,3',3"-(Benzene-1,3,5-triyl)tripyrene (abbreviation: TPB3) and the like. One or more substances with a larger energy gap than the guest material 131 are preferably selected from these substances and known substances.

[0117] The light-emitting layer 130 may have a structure in which two or more layers are stacked. For example, in the case where the light-emitting layer 130 is formed by stacking a first light-emitting layer and a second light-emitting layer in this order from the hole-transport layer side, the first light-emitting layer is formed using a substance having a hole-transport property as a host material, and the second light-emitting layer is formed using a substance having an electron-transport property as a host material.

[0118] The light-emitting layer 130 may contain another material in addition to the guest material 131, the host material 132 and the host material 133.

[0119] A fluorescent compound may further be used in the light-emitting layer 130. The fluorescent compound is preferably, but is not 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.

[0120] 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'''-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-anthryl)-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: 2DPABPhA), 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)tetracen-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[ij]chino lizin-9-yl)ethenyl]-4H-pyran-4-ylidene} propandinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2,6-Bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-Bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), 5,10,15,20-Tetraphenylbisbenzo[5,6]indeno[1,2,3-cd:1',2',3'-Im]perylene and the like.

[0121] Furthermore, any material capable of converting triplet excitation energy into singlet excitation energy can be used as the guest material 131. As a material capable of converting triplet excitation energy into singlet excitation energy, a thermally activated delayed fluorescent material can be specified in addition to the phosphorescent compound. Accordingly, "phosphorescent compound" in the description can be replaced with "thermally activated delayed fluorescent material." The thermally activated delayed fluorescence is efficiently obtained under the condition where the difference between the S1 level and the T1 level is greater than 0 eV and less than or equal to 0.2 eV, preferably greater than 0 eV and less than or equal to 0.1 eV.

[0122] The material exhibiting thermally activated delayed fluorescence may be a material that can spontaneously form a singlet excited state from a triplet excited state through reverse intersystem crossing. In the case where the thermally activated delayed fluorescent material consists of one type of material, for example, any of the following materials can be used.

[0123] First, a fullerene, a derivative thereof, an acridine derivative such as proflavin, eosin, and the like can be mentioned. Other examples include a metal-containing porphyrin, such as porphyrin containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd). Examples of the metal-containing porphyrin include a protoporphyrin-tin fluoride complex (abbreviation: SnF2(Proto IX)), a mesoporphyrin-tin fluoride complex (abbreviation: SnF2(Meso IX)), a hematoporphyrin-tin fluoride complex (abbreviation: SnF2(Hemato IX)), a coproporphyrin-tetramethyl ester-tin fluoride complex (abbreviation: SnF2(Copro III-4Me)), an octaethylporphyrin-tin fluoride complex (abbreviation: SnF2(OEP)), an etioporphyrin-tin fluoride complex (abbreviation: SnF2(Etio I)), an octaethylporphyrin-platinum chloride complex (abbreviation: PtCl2OEP) and the like.

[0124] For the thermally activated delayed fluorescent material consisting of one type of material, a heterocyclic compound comprising a π-electron-rich heteroaromatic framework and a π-electron-poor heteroaromatic framework can also be used. 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-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3, 5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-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-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), 10-phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (abbreviation: ACRSA) or the like.The heterocyclic compound is preferably used because it has a π-electron-rich heteroaromatic skeleton and a π-electron-poor heteroaromatic skeleton; therefore, the electron-transport property and hole-transport property are high. Note that a substance in which the π-electron-rich heteroaromatic skeleton is directly bonded to the π-electron-poor heteroaromatic skeleton is particularly preferred because both the donor property of the π-electron-rich heteroaromatic skeleton and the acceptor property of the π-electron-poor heteroaromatic skeleton are enhanced, and the difference between the S1 level and the T1 level becomes small. <<Paar von Elektroden> >

[0125] The electrode 101 and the electrode 102 have functions of injecting holes and electrons into the light-emitting layer 130. The electrodes 101 and 102 can be formed, for example, using a metal, an alloy, a conductive compound, or a mixture or stack of these. A typical example of the metal is aluminum (Al); in addition, a transition metal such as silver (Ag), tungsten, chromium, molybdenum, copper, or titanium; an alkali metal such as lithium (Li) or cesium; or a Group 2 metal such as calcium or magnesium (Mg) can also be used. As the transition metal, a rare earth metal such as ytterbium (Yb) can be used. An alloy containing any of the above metals can be used as an alloy, and MgAg and AlLi can be cited as examples. Examples of the conductive compound include metal oxides such asIndium tin oxide (hereinafter referred to as ITO), indium tin oxide containing silicon or silicon oxide (ITSO), indium zinc oxide, indium oxide containing tungsten and zinc, and the like. It is also possible to use an inorganic carbon-based material such as graphene as the conductive compound. As described above, the electrode 101 and / or the electrode 102 may be formed by stacking two or more of these materials.

[0126] Light emitted from the light-emitting layer 130 is extracted via the electrode 101 and / or the electrode 102. Accordingly, at least one of the electrode 101 and the electrode 102 transmits visible light. As the conductive material that transmits light, a conductive material whose visible light transmittance is higher than or equal to 40% and lower than or equal to 100%, preferably higher than or equal to 60% and lower than or equal to 100%, and whose specific resistance is lower than or equal to 1×10 -2 Ω cm. The electrode on the light extraction side can be formed using a conductive material with light transmitting and light reflecting functions. As the conductive material, a conductive material whose visible light reflectance is higher than or equal to 20% and lower than or equal to 80%, preferably higher than or equal to 40% and lower than or equal to 70%, and whose resistivity is lower than or equal to 1×10 -2 Ω cm. In the case where the electrode through which light is taken out is formed using a material with low light transmittance, such as a metal or an alloy, the electrode 101 and / or the electrode 102 are / is formed to a thickness thin enough to transmit visible light (e.g., a thickness of 1 nm to 10 nm).

[0127] In this specification and the like, a material that transmits visible light and has conductivity is used as the light-transmitting electrode. Examples of the material include, in addition to the above-described oxide conductive layer, of which ITO is a typical example, an oxide semiconductor layer and an organic conductive layer containing an organic substance. Examples of the organic conductive layer containing an organic substance include a layer containing a composite material in which an organic compound and an electron donor (donor) are mixed, and a layer containing a composite material in which an organic compound and an electron acceptor (acceptor) are mixed. The specific resistance of the transparent conductive layer is preferably less than or equal to 1 × 10 5 Ω·cm, more preferably lower than or equal to 1×10 4 Ω·cm.

[0128] As a method for forming the electrode 101 and the electrode 102, a sputtering method, an evaporation method, a printing method, a coating method, a molecular beam epitaxy (MBE) method, a CVD method, a pulse laser deposition method, an atomic layer deposition (ALD) method, or the like can be used as needed. < <lochinjektionsschicht>>

[0129] The hole-injection layer 111 has a function of reducing a barrier to hole injection from one of the pair of electrodes (the electrode 101 or the electrode 102) to promote hole injection, and is formed using, for example, a transition metal oxide, a phthalocyanine derivative, or an aromatic amine. Molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide, or the like can be cited as the transition metal oxide. Phthalocyanine, metal phthalocyanine, or the like can be cited as the phthalocyanine derivative. A benzidine derivative, a phenylenediamine derivative, or the like can be cited as the aromatic amine. It is also possible to use a high-molecular compound such as polythiophene or polyaniline. A typical example is poly(ethylenedioxythiophene) / poly(styrenesulfonic acid), which is a self-doped polythiophene.

[0130] As the hole-injection layer 111, a layer containing a composite material of a hole-transporting material and a material having a property of accepting electrons from the hole-transporting material can also be used. Alternatively, a layer arrangement of a layer containing a material having an electron-accepting property and a layer containing a hole-transporting material can also be used. In a stable state or in the presence of an electric field, electric charges can be transferred between these materials. As examples of the material having a property of accepting electrons, organic acceptors such as a quinodimethane derivative, a chloranil derivative, and a hexaazatriphenylene derivative can be given. A specific example is a compound having an electron-withdrawing group (a halogen group or a cyano group), such as7,7,8,8-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 Group 4 to Group 8 metal, can also be used. Specifically, 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 particularly preferred because it is stable in air, has low hygroscopicity, and is easy to handle.

[0131] A material with a property of transporting more holes than electrons can be used as a hole transport material, whereby a material with a hole mobility of 1×10 -6 cm 2 / Vs or higher is preferable. Specifically, any of the above aromatic amines, carbazole derivatives, aromatic hydrocarbons, stilbene derivatives, and the like can be used as the hole-transporting material that can be used in the light-emitting layer 130. Furthermore, the hole-transporting material may be a high-molecular compound.

[0132] Examples of the aromatic hydrocarbon 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'-blanthryl, anthracene, tetracene, rubrene, perylene, 2,5,8,11-Tetra(tert-butyl)perylene and the like. Other examples include pentacene, coronene, and the like.The aromatic hydrocarbon, which has a hole mobility of 1×10. -6 cm 2 / Vs or higher and 14 to 42 carbon atoms is particularly preferred.

[0133] The aromatic hydrocarbon may have 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.

[0134] Further examples include high molecular weight compounds 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) and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: poly-TPD). < <lochtransportschicht>>

[0135] The hole-transport layer 112 is a layer containing a hole-transport material and can be formed using any of the materials given as examples of the material of the hole-injection layer 111. In order for the hole-transport layer 112 to have a function of transporting holes injected into the hole-injection layer 111 to the light-emitting layer 130, the HOMO level of the hole-transport layer 112 is preferably equal to or close to the HOMO level of the hole-injection layer 111.

[0136] Any of the materials given as examples for the material of the hole injection layer 111 can be used as the hole transport material. Furthermore, a substance having a hole mobility of 1×10 -6 cm 2 / Vs or higher is used. Note that, in addition to these substances, any substance that has the property of transporting more holes than electrons can be used. The layer containing a substance with a high hole-transport property is not limited to a single layer, and two or more layers containing the above substances can be stacked. < <elektronentransportschicht>>

[0137] The electron-transport layer 118 has a function of transporting electrons injected from the other electrode of the pair of electrodes (the electrode 101 or the electrode 102) via the electron-injection layer 119 to the light-emitting layer 130. A material having a property of transporting more electrons than holes can be used as the electron-transport material, and a material having an electron mobility of 1×10 -6 cm 2 / Vs or higher is preferable. As a compound that readily accepts electrons (a material with an electron-transport property), for example, a π-electron-deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound, a metal complex, or the like can be used. Specifically, a metal complex having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand can be cited, which has been described as an electron-transport material that can be used in the light-emitting layer 130. In addition, an oxadiazole derivative, a triazole derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, and the like can be cited. A substance having an electron mobility of 1×10 -6 cm 2 / Vs or higher is preferable. Note that a substance other than the above substances can be used as long as it has a higher electron-transport property than a hole-transport property. The electron-transport layer 118 is not limited to a single layer, and it may be a stacked arrangement of two or more layers containing the above-mentioned substances.

[0138] Between the electron-transport layer 118 and the light-emitting layer 130, a layer that controls the transport of electron carriers can be provided. This layer is formed, as described above, by adding a small amount of a substance with a high electron-capturing property to a material with a high electron-transporting property. The layer is capable of adjusting the carrier balance by suppressing the transport of electron carriers. Such a structure is very effective in preventing a problem (such as a reduction in the element's lifetime) that arises when electrons pass through the light-emitting layer. < <elektroneninjektionsschicht>>

[0139] The electron injection layer 119 has a function of reducing a barrier to electron injection from the electrode 102 to promote electron injection, and can be formed using, for example, a Group 1 metal or a Group 2 metal, or an oxide, a halide, or a carbonate of one of the metals. Alternatively, a composite material containing an electron-transport material (described above) and a material having a property of donating electrons to the electron-transport material can also be used. As the material having a property of donating electrons, a Group 1 metal, a Group 2 metal, an oxide of the metal, or the like can be specified. Specifically, an alkali metal, an alkaline earth metal, or a compound thereof, such as hydroxide, can be used.Lithium fluoride (LiF), sodium fluoride (NaF), cesium fluoride (CsF), calcium fluoride (CaF2) or lithium oxide (LiO). x ) can be used. A rare earth metal compound, such as erbium fluoride (ErF3), can also be used. An electride can also be used for the electron-injection layer 119. Examples of the electride include a substance in which electrons have been added at a high concentration to calcium oxide-alumina. The electron-injection layer 119 can be formed using the substance that can be used for the electron-transport layer 118.

[0140] 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 has excellent electron injection properties and electron transport properties because electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material that can excellently transport the generated electrons. Specifically, for example, the substances listed above (e.g., metal complexes and heteroaromatic compounds) can be used for forming the electron-transport layer 118. As the electron donor, a substance that has an electron-donating property with respect to the organic compound can be used.In particular, an alkali metal, an alkaline earth metal, and a rare earth metal are preferred, and lithium, cesium, magnesium, calcium, erbium, ytterbium, and the like can be cited. Furthermore, an alkali metal oxide or an alkaline earth metal oxide is preferred, and lithium oxide, calcium oxide, barium oxide, and the like can be cited. A Lewis base such as magnesium oxide can be used alternatively. An organic compound such as tetrathiafulvalene (abbreviation: TTF) can be used as a further alternative.

[0141] Note that the light-emitting layer, hole-injection layer, hole-transport layer, electron-transport layer, and electron-injection layer described above can each be formed by an evaporation method (including a vacuum evaporation method), an inkjet method, a coating method, a jet printing method, a gravure printing method, or the like. In addition to the above-mentioned materials, an inorganic compound such as a quantum dot or a high-molecular compound (e.g., an oligomer, a dendrimer, or 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.

[0142] The quantum dot can be, for example, a gelatinous quantum dot, an alloyed quantum dot, a core-shell quantum dot, or a core quantum dot. The quantum dot containing elements belonging to groups 2 and 16, elements belonging to groups 13 and 15, elements belonging to groups 13 and 17, elements belonging to groups 11 and 17, or elements belonging to groups 14 and 15 can be used. Alternatively, the quantum dot containing an element such as cadmium (Cd), selenium (Se), zinc (Zn), sulfur (S), phosphorus (P), indium (In), tellurium (Te), lead (Pb), gallium (Ga), arsenic (As), or aluminum (Al) can be used.

[0143] An example of a liquid medium used for a wet process includes an organic solvent 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.

[0144] Examples of the high molecular compound that can be used for the light-emitting layer include a phenylenevinylene (PPV) derivative such as poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (abbreviation: MEH-PPV) or poly(2,5-dioctyl-1,4-phenylenevinylene); a polyfluorene derivative such as poly(ethylenediamine dimethyl ether). B. Poly(9,9-di-n-octylfluorenyl-2,7-diyl) (abbreviation: PF8), poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazole-4,8-diyl)] (abbreviation: F8BT), poly(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(2,2'-bithiophene-5,5'-diyl)] (abbreviation: F8T2), poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-(9,10-anthracene)] or poly[(9,9-dihexylfluorene-2,7-diyl)-alt-(2,5-dimethyl-1,4-phenylene)]; a polyalkylthiophene (PAT) derivative, such as poly(3-hexylthiophene-2,5-diyl) (abbreviation: P3HT); a polyphenylene derivative, or the like. These high-molecular-weight compounds or a high-molecular-weight compound, such asPoly(9-vinylcarbazole) (abbreviation: PVK), poly(2-vinylnaphthalene), or poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (abbreviation: PTAA) can be doped with a compound having a light-emitting property and used for the light-emitting layer. Any of the compounds having a light-emitting property described above can be used as the compound having a light-emitting property. < <substrat>>

[0145] A light-emitting element of one embodiment of the present invention can be formed over a substrate made of glass, plastic, or the like. As one way to stack layers over the substrate, layers can be arranged sequentially from the electrode 101 side or sequentially from the electrode 102 side.

[0146] For the substrate over which the light-emitting element of one embodiment of the present invention can be formed, for example, glass, quartz, plastic, or the like can be used. Alternatively, a flexible substrate can be used. The flexible substrate is, for example, a substrate that can be bent, such as a plastic substrate made of polycarbonate or polyarylate. Alternatively, a film, an inorganic film formed by vapor deposition, 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 elements or the optical elements. Another material having a function of protecting the light-emitting elements or the optical elements can be used.

[0147] For example, in this specification and the like, a light-emitting element can be formed using various substrates. The type of substrate is not particularly limited. Examples of the substrate include a semiconductor substrate (e.g., a single-crystal substrate or a silicon substrate), a 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, an attachment film, a cellulose nanofiber (CNF) and paper containing a fiber material, a base material film, and the like. As an example of a glass substrate, a barium borosilicate glass substrate, an aluminum borosilicate glass substrate, a soda-lime glass substrate, or the like can be given.Examples of the flexible substrate, the fixing film, the base material film, and the like include substrates made of plastics, typical examples being polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). Another example includes a resin such as acrylic. Alternatively, polypropylene, polyester, polyvinyl fluoride, polyvinyl chloride, or the like may be used. Alternatively, polyamide, polyimide, aramid, epoxy, an inorganic film formed by vapor deposition, paper, or the like may be used.

[0148] Alternatively, a flexible substrate may be used as the substrate, and the light-emitting element may be provided directly above the flexible substrate. Alternatively, a separation layer may be provided between the substrate and the light-emitting element. The separation layer may be used when a part or all of the light-emitting element formed above the separation layer is completed, separated from the substrate, and transferred to another substrate. In such a case, the light-emitting element may also be transferred to a substrate with low heat resistance or to a flexible substrate. For the above separation layer, for example, a layer assembly comprising inorganic films, namely a tungsten film and a silicon oxide film, or a resin film of polyimide or the like formed over a substrate may be used.

[0149] In other words, after the light-emitting element is formed using a substrate, the light-emitting element can be transferred to another substrate. Examples of a substrate to which the light-emitting element is transferred include, in addition to the substrates described above, a cellophane substrate, a stone substrate, a wood substrate, a fabric substrate (including a natural fiber (e.g., silk, cotton, or hemp), a synthetic fiber (e.g., nylon, polyurethane, or polyester), a regenerated fiber (e.g., acetate, cupro, viscose, or regenerated polyester), or the like), a leather substrate, and a rubber substrate. When such a substrate is used, a light-emitting element with high durability, a light-emitting element with high heat resistance, a light-emitting element with reduced weight, or a light-emitting element with reduced thickness can be formed.

[0150] The light-emitting element 150 can, for example, be formed over an electrode electrically connected to a field-effect transistor (FET) formed over one of the substrates described above. In this way, an active matrix display device can be fabricated in which the FET controls the operation of the light-emitting element.

[0151] The structure described above in this embodiment can be appropriately combined with any of the other embodiments. (Embodiment 2)

[0152] In this embodiment, a light-emitting element having a structure different from that described in Embodiment 1 and light-emitting mechanisms of the light-emitting element will be described below with reference to Fig. 5. In Fig. 5, in some cases, a section with a similar function to that in Fig. 1 by the same hatching pattern as in Fig. 1 and are not specifically identified by a reference symbol. In addition, the same reference symbols are used for sections with similar functions, and a detailed description of the sections is omitted in some cases. <Strukturbeispiel des Licht emittierenden Elements>

[0153] Fig. 5 is a schematic cross-sectional view of a light-emitting element 250.

[0154] The light-emitting element 250, which is in Fig. 5 comprises a plurality of light-emitting units (a light-emitting unit 106 and a light-emitting unit 108 in Fig. 5) between a pair of electrodes (the electrode 101 and the electrode 102). A light-emitting unit has the same structure as the EL layer 100 shown in Fig. 1. That is, the light-emitting element 150 shown in Fig. 1 includes one light-emitting unit, whereas the light-emitting element 250 includes a plurality of light-emitting units. Note that the electrode 101 serves as the anode and the electrode 102 serves as the cathode in the following description of the light-emitting element 250; however, the functions of the light-emitting element 250 may be interchanged.

[0155] In the light emitting element 250, which is in Fig. 5, the light-emitting unit 106 and the light-emitting unit 108 are arranged one above the other, and a charge generation 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 may have the same structure or may have different structures. For example, the structure of the EL layer 100 shown in Fig. 1 is preferably used for the light-emitting unit 106.

[0156] The light-emitting element 250 includes the light-emitting layer 130 and a light-emitting layer 170. The light-emitting unit 106 includes the hole-injection layer 111, the hole-transport layer 112, the electron-transport layer 113, and the electron-injection layer 114 in addition to the light-emitting layer 130. The light-emitting unit 108 includes, in addition to the light-emitting layer 170, a hole-injection layer 116, a hole-transport layer 117, an electron-transport layer 118, and an electron-injection layer 119.

[0157] The charge generation layer 115 may have either a structure in which an acceptor substance, which is an electron acceptor, is added to a hole-transporting material, or a structure in which a donor substance, which is an electron donor, is added to an electron-transporting material. Alternatively, both of these structures may be arranged one above the other.

[0158] In the case where the charge generation 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 for the composite material. Various compounds, such as an aromatic amine compound, a carbazole compound, an aromatic hydrocarbon, and a high-molecular compound (such as an oligomer, a dendrimer, or a polymer), can be used as the organic compound. A substance with a hole mobility of 1×10 -6 cm 2 / Vs or higher is preferably used as the organic compound. Note that any other substance can be used as long as it has a property of transporting more holes than electrons. Since the composite material of an organic compound and an acceptor substance has excellent charge injection and charge transport properties, low-voltage operation or low-current operation can be achieved. Note that when a surface of a light-emitting unit on the anode side is in contact with the charge generation layer 115, as in the light-emitting unit 108, the charge generation layer 115 can also serve as a hole injection layer or a hole transport layer of the light-emitting unit; therefore, a hole injection layer or a hole transport layer may not necessarily be included in the light-emitting unit.

[0159] The charge generation layer 115 may have a multilayer structure composed 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 generation layer 115 may be formed by combining a layer containing the composite material of an organic compound and an acceptor substance with a layer containing a compound selected from materials having an electron-donating property and a compound having a high electron-transporting property. Furthermore, the charge generation layer 115 may be formed by combining a layer containing the composite material of an organic compound and an acceptor substance with a layer containing a transparent conductive material.

[0160] The charge generation layer 115 provided between the light-emitting unit 106 and the light-emitting unit 108 may 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 the electrode 101 and the electrode 102. For example, Fig. 5 the charge generation 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 the electrode 101 becomes higher than that of the electrode 102.

[0161] Note that, in terms of light extraction efficiency, the charge generation layer 115 preferentially transmits visible light (specifically, it has a visible light transmittance of greater than or equal to 40%). The charge generation layer 115 operates even if it has a lower conductivity than the pair of electrodes (electrodes 101 and 102). In the case where the conductivity of the charge generation layer 115 is the same as that of the pair of electrodes, charge carriers generated in the charge generation layer 115 flow toward the film surface, so that light is emitted in some cases in a region where the electrode 101 and the electrode 102 do not overlap with each other.To suppress such a defect, the charge generation layer 115 is preferably formed using a material whose conductivity is lower than those of the pair of electrodes.

[0162] By forming the charge generation layer 115 using any of the above materials, an increase in the driving voltage caused by the stacking of the light-emitting layers can be suppressed.

[0163] The light-emitting element, which comprises two light-emitting units, was designed using Fig. 5; however, a similar structure can also be applied to a light-emitting element in which three or more light-emitting units are stacked. By placing a plurality of light-emitting units separated by the charge generation layer between a pair of electrodes, just as in the light-emitting element 250, a light-emitting element capable of emitting light with high luminance while keeping the current density low and having a long lifetime can be provided. A light-emitting element with low power consumption can also be provided.

[0164] If the structure of the EL layer 100 shown in Fig. 1 is used for at least one of the plurality of units, a light-emitting element with high emission efficiency can be provided.

[0165] Preferably, the light-emitting layer 130 of the light-emitting unit 106 has the structure described in Embodiment 1. In this case, the light-emitting element 250 has high emission efficiency.

[0166] It should be noted that the guest materials used in the light-emitting unit 106 and the light-emitting unit 108 may be the same or different from each other. In the case where the same guest material is used for the light-emitting unit 106 and the light-emitting unit 108, the light-emitting element 250 can have high emission luminance at a small current value, which is preferable. In the case where different guest materials are used for the light-emitting unit 106 and the light-emitting unit 108, the light-emitting element 250 can have multicolor light emission, which is preferable. In particular, the guest materials are preferably selected such that white light emission with high color rendering properties or light emission of at least red, green, and blue can be obtained.

[0167] Note that the light-emitting units 106 and 108 and the charge generation layer 115 can be formed by an evaporation method (including a vacuum evaporation method), an inkjet method, a coating method, gravure printing, or the like.

[0168] It should be noted that the structure described in this embodiment can be used in an appropriate combination with any of the structures described in the other embodiments. (Embodiment 3)

[0169] In this embodiment, examples of the light-emitting elements having structures different from those described in Embodiments 1 and 2 will be described below with reference to Fig. 6 and Fig. 7A and Fig. 7B. <Strukturbeispiel 1 des Licht emittierenden Elements>

[0170] Fig. 6 is a cross-sectional view of a light-emitting element of an embodiment of the present invention. In Fig. 6, in some cases, a section with a similar function to that in Fig. 1 by the same hatching pattern as in Fig. 1 and are not specifically identified by a reference symbol. In addition, the same reference symbols are used for sections with similar functions, and a detailed description of the sections is omitted in some cases.

[0171] A light-emitting element 260 in Fig. 6 may have a bottom-emission structure in which light is extracted via a substrate 200, or may have a top-emission structure in which light emitted from 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 having a dual-emission structure in which light emitted from the light-emitting element is extracted in both the top and bottom directions of the substrate 200 may be employed.

[0172] In the case where the light-emitting element 260 has a bottom-emission structure, the electrode 101 preferably has a function of transmitting light. Furthermore, the electrode 102 preferably has a function of reflecting light. In the case where the light-emitting element 260 has a top-emission structure, the electrode 101 preferably has a function of reflecting light. Furthermore, the electrode 102 preferably has a function of transmitting light.

[0173] The light-emitting element 260 includes the electrode 101 and the electrode 102 above the substrate 200. Between the 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.

[0174] Furthermore, the electrode 101 can be formed from a plurality of conductive layers. In this case, a structure in which a conductive layer with a function of reflecting light and a conductive layer with a function of transmitting light are stacked is preferred.

[0175] For the electrode 101, the structure and materials of the electrode 101 or the electrode 102 described in Embodiment 1 can be used.

[0176] In Fig. 6, a partition wall 145 is provided between a region 221B, a region 221G, and a region 221R, which are arranged between the electrode 101 and the electrode 102. The partition wall 145 has an insulating property. The partition wall 145 covers end portions of the electrode 101 and has openings that overlap with the electrode. The partition wall 145 allows the electrode 101, which is provided above the substrate 200 in the regions, to be divided into island shapes.

[0177] Note that the light-emitting layer 123B and the light-emitting layer 123G may overlap each other in a region where they overlap with the partition wall 145. The light-emitting layer 123G and the light-emitting layer 123R may overlap each other in a region where they overlap with the partition wall 145. The light-emitting layer 123R and the light-emitting layer 123B may overlap each other in a region where they overlap with the partition wall 145.

[0178] The partition wall 145 has an insulating property and is formed using an inorganic or organic material. Examples of the inorganic material include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum nitride, and the like. Examples of the organic material include photosensitive resin materials such as acrylic resin and polyimide resin.

[0179] Light-emitting layers 123R, 123G, and 123B preferably contain light-emitting materials with functions for emitting light of different colors. For example, when light-emitting layer 123R includes a light-emitting material with a red-emitting function, region 221R emits red light. When light-emitting layer 123G includes a light-emitting material with a green-emitting function, region 221G emits green light. When light-emitting layer 123B includes a light-emitting material with a blue-emitting function, region 221B emits blue light. By using the light-emitting element 260 with such a structure in a pixel of a display device, a full-color display device can be manufactured. The thicknesses of the light-emitting layers may be the same or different from each other.

[0180] One or more of the light-emitting layer 123B, the light-emitting layer 123G, and the light-emitting layer 123R preferably have the structure of the light-emitting layer 130 described in Embodiment 1. In this case, a light-emitting element with high emission efficiency can be manufactured.

[0181] One or more of the light-emitting layers 123B, 123G and 123R may comprise two or more layers arranged one above the other.

[0182] When at least one light-emitting layer includes the light-emitting layer described in Embodiment 1, and the light-emitting element 260 including 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 including the light-emitting element 260 can thus have reduced power consumption.

[0183] By providing a color filter over the electrode through which light is extracted, the color purity of the light-emitting element 260 can be improved. Consequently, the color purity of a display device including the light-emitting element 260 can be improved.

[0184] The reflection of external light from the light-emitting element 260 can be reduced by providing a polarizing plate over the electrode through which light is extracted. Consequently, the contrast ratio of a display device including the light-emitting element 260 can be improved.

[0185] Note that for the other components of the light-emitting element 260, reference may be made to the components of the light-emitting elements of Embodiment 1. <Strukturbeispiel 2 des Licht emittierenden Elements>

[0186] Next, a structural example that is different from the light-emitting element used in Fig. 6 is shown, in the following using Fig. 7A and Fig. 7B.

[0187] Fig. 7A and Fig. 7B are cross-sectional views each illustrating a light-emitting element of an embodiment of the present invention. In Fig. 7A and Fig. 7B, in some cases, a section with a similar function to that in Fig. 6 by the same hatching pattern as in Fig. 6 and are not specifically designated with a reference symbol. In addition, the same reference symbols are used for sections with similar functions, and a detailed description of the sections is omitted in some cases.

[0188] Fig. 7A and Fig. 7B illustrate structural examples of a light-emitting element including the light-emitting layer between a pair of electrodes. A light-emitting element 262a shown in Fig. 7A has a top-emission structure in which light is taken out in a direction opposite to the substrate 200, and a light-emitting element 262b arranged in Fig. 7B has a bottom-emission structure in which light is extracted to 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 from the light-emitting element is extracted in both the top and bottom directions with respect to the substrate 200 over which the light-emitting element is formed.

[0189] The light-emitting elements 262a and 262b each include the electrode 101, the electrode 102, an electrode 103, and an electrode 104 above the substrate 200. At least one light-emitting layer 130 and a charge generation layer 115 are provided between the electrode 101 and the electrode 102, between the electrode 102 and the electrode 103, and between the electrode 102 and the electrode 104. The hole-injection layer 111, the hole-transport layer 112, a light-emitting layer 170, 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 further provided.

[0190] The electrode 101 comprises a conductive layer 101a and a conductive layer 101b over and in contact with the conductive layer 101a. The electrode 103 comprises a conductive layer 103a and a conductive layer 103b over and in contact with the conductive layer 103a. The electrode 104 comprises a conductive layer 104a and a conductive layer 104b over and in contact with the conductive layer 104a.

[0191] The light-emitting element 262a, which is in Fig. 7A, and the light emitting element 262b shown in Fig. 7B, each includes the partition wall 145 between a region 222B disposed between the electrode 101 and the electrode 102, a region 222G disposed between the electrode 102 and the electrode 103, and a region 222R disposed between the electrode 102 and the electrode 104. The partition wall 145 has an insulating property. The partition wall 145 covers end portions of the electrodes 101, 103, and 104 and has openings that overlap with the electrodes. By the partition wall 145, the electrodes provided above the substrate 200 in the regions can be divided into island shapes.

[0192] The light-emitting elements 262a and 262b each include 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 the region 222B, the light emitted from the region 222G, and the light emitted from the region 222R are taken out. The light emitted from each region is emitted to the outside of the light-emitting element via the corresponding optical element. In other words, the light from the region 222B, the light from the region 222G, and the light from the region 222R are emitted via the optical element 224B, the optical element 224G, and the optical element 224R, respectively.

[0193] Optical elements 224B, 224G, and 224R each have a function of selectively transmitting light of a specific color of the incident light. For example, the light emitted from region 222B via optical element 224B is blue light, the light emitted from region 222G via optical element 224G is green light, and the light emitted from region 222R via optical element 224R is red light.

[0194] 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 the 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 the color conversion elements. The use of quantum dots can increase the color reproducibility of the display device.

[0195] A plurality of optical elements may also be arranged over each of the optical elements 224R, 224G, and 224B. As another optical element, for example, a circularly polarizing plate, an anti-reflection film, or the like may be provided. A circularly polarizing plate provided on the side where light emitted from the light-emitting element of the display device is taken out can prevent a phenomenon in which light incident from the outside of the display device is reflected inside the display device and redirected to the outside. An anti-reflection film can attenuate external light reflected from a surface of the display device. This leads to clear observation of light emitted from the display device.

[0196] It should be noted that in Fig. 7A and Fig. 7B blue light (B), green light (G) and red light (R) emitted from the regions via the optical elements are schematically represented by arrows of dashed lines.

[0197] An opaque layer 223 is provided between the optical elements. The opaque layer 223 has a function of blocking light emitted from adjacent regions. Note that a structure without the opaque layer 223 can also be used.

[0198] The opaque layer 223 has a function of reducing the reflection of external light. The opaque layer 223 has a function of preventing mixing of light emitted from an adjacent light-emitting element. A metal, a resin containing a black pigment, carbon black, a metal oxide, a composite oxide containing a solid solution of a plurality of metal oxides, or the like can be used as the opaque layer 223.

[0199] For the substrate 200 and the substrate 220 provided with the optical elements, reference may be made to the substrate of Embodiment 1.

[0200] Furthermore, the light-emitting elements 262a and 262b have a microcavity structure. <<Mikrokavitätsstruktur> >

[0201] Light emitted from the light-emitting layer 130 and the light-emitting layer 170 oscillates between a pair of electrodes (e.g., the electrode 101 and the electrode 102). The light-emitting layer 130 and the light-emitting layer 170 are each formed at a location such that they amplify the light of a desired wavelength among light to be emitted. For example, by adjusting the optical length from a reflecting region of the electrode 101 to a light-emitting region of the light-emitting layer 130 and the optical length from a reflecting region of the electrode 102 to the light-emitting region of the light-emitting layer 130, the light of a desired wavelength among light emitted from the light-emitting layer 130 can be amplified.By adjusting the optical length from a reflective region of the electrode 101 to a light-emitting region of the light-emitting layer 170 and the optical length from a reflective region of the electrode 102 to the light-emitting region of the light-emitting layer 170, light of a desired wavelength can also be amplified among light emitted from the light-emitting layer 170. In the case of a light-emitting element in which a plurality of light-emitting layers (here, the light-emitting layers 130 and 170) are stacked, the optical lengths of the light-emitting layers 130 and 170 are preferably optimized.

[0202] In each of the light-emitting elements 262a and 262b, the light of a desired wavelength can be amplified among the light emitted from the light-emitting layers 130 and 170 by adjusting the thicknesses of the conductive layers (the conductive layer 101b, the conductive layer 103b, and the conductive layer 104b) in each region. Note that the thickness of at least one of the hole-injection layer 111 and the hole-transport layer 112 may differ between regions to amplify the light emitted from the light-emitting layers 130 and 170.

[0203] For example, in the case where the refractive index of the conductive material having a function of reflecting light in the electrodes 101 to 104 is lower than the refractive index of the light-emitting layer 170 or the light-emitting layer 170, the thickness of the conductive layer 101b of the electrode 101 is adjusted such that the optical length between the electrode 101 and the electrode 102 becomes m B λ B / 2 becomes (m B is a natural number and λ B is the wavelength of the light amplified in the region 222B). The thickness of the conductive layer 103b of the electrode 103 is similarly adjusted such that the optical length between the electrode 103 and the electrode 102 becomes m G λ G / 2 becomes (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 adjusted such that the optical length between the electrode 104 and the electrode 102 is m R λ R / 2 becomes (m R is a natural number and λ R is the wavelength of light that is amplified in the 222R range).

[0204] In the above manner, the microcavity structure in which the optical length between the pair of electrodes is adjusted in the respective regions can suppress light scattering and absorption in the vicinity of the electrodes, resulting in high light extraction efficiency. In the above structure, the conductive layers 101b, 103b, and 104b preferably have a light transmission function. The materials for the conductive layers 101b, 103b, and 104b may be the same as or different from each other. Each of the conductive layers 101b, 103b, and 104b may have a multilayer structure composed of two or more layers.

[0205] Since the light-emitting element 262a, which is Fig. 7A, has a top-emission structure, the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a preferably have a function of reflecting light. Furthermore, the electrode 102 preferably has functions of transmitting and reflecting light.

[0206] Since the light-emitting element 262b, which is Fig. 7B, has a bottom-emission structure, the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a preferably have light transmitting and reflecting functions. Furthermore, the electrode 102 preferably has a light reflecting function.

[0207] In each of the light-emitting elements 262a and 262b, the conductive layers 101a, 103a, and 104a can be formed from different materials or the same material. If the conductive layers 101a, 103a, and 104a are formed from the same material, the manufacturing cost of the light-emitting elements 262a and 262b can be reduced. Note that each of the conductive layers 101a, 103a, and 104a can have a multilayer structure composed of two or more layers.

[0208] Furthermore, the light-emitting layer 130 in the light-emitting element 262a and the light-emitting element 262b preferably has the structure described in Embodiment 1. In this way, the light-emitting elements can have high emission efficiency.

[0209] One or both of the light-emitting layers 130 and 170, like the light-emitting layers 170a and 170b, may, for example, have a multilayer structure composed of two layers. The two light-emitting layers, which include two types of light-emitting materials (a first light-emitting material and a second light-emitting material) for emitting light of different colors, enable light emission of a variety of colors. Preferably, the light-emitting materials of the light-emitting layers are selected in particular such that white light can be obtained by combining light emissions from the light-emitting layers 130 and 170.

[0210] One or both of the light-emitting layers 130 and 170 may have a multilayer structure of three or more layers, which may include a layer that does not contain light-emitting material.

[0211] By using the light-emitting element 262a or 262b including the light-emitting layer having one of the structures described in Embodiment 1 in a pixel of a display device as described above, a display device with high emission efficiency can be manufactured. The display device including the light-emitting element 262a or 262b can thus have low power consumption.

[0212] For the other components of the light-emitting elements 262a and 262b, reference may be made to the components of the light-emitting element 260 or the light-emitting elements of Embodiments 1 and 2.

[0213] It should be noted that a structure described in this embodiment may be used in an appropriate combination with any of the structures described in the other embodiments. (Embodiment 4)

[0214] In this embodiment, a display device including a light-emitting element of an embodiment of the present invention is described with reference to Fig. 8A and Fig. 8B, Fig. 9A and Fig. 9B and Fig. 10A and Fig. 10B described. <Strukturbeispiel 1 der Anzeigevorrichtung>

[0215] Fig. Fig. 8A is a plan view showing a display device 600, and Fig. 8B is a cross-sectional view taken along the dashed line AB and the dashed line CD in Fig. 8A. The display device 600 includes driver circuit sections (a signal line driver circuit section 601 and a scan line driver circuit section 603) and a pixel section 602. Note that the signal line driver circuit section 601, the scan line driver circuit section 603, and the pixel section 602 have a function of controlling light emission from a light-emitting element.

[0216] The display device 600 also includes an element substrate 610, a sealing substrate 604, a sealant 605, a region 607 enclosed by the sealant 605, a lead wire 608, and an FPC 609.

[0217] Note that the connecting line 608 is a line for transmitting signals input to the signal line driver circuit section 601 and the scanning line driver circuit section 603, and for receiving a video signal, a clock signal, a start signal, a reset signal, and the like from the FPC 609, which serves as an external input terminal. Although only the FPC 609 is illustrated here, the FPC 609 may be provided with a printed wiring board (PWB).

[0218] As the signal line driver circuit section 601, a CMOS circuit combining an n-channel transistor 623 and a p-channel transistor 624 is formed. Various types of circuits, such as a CMOS circuit, a PMOS circuit, or an NMOS circuit, can be used as the signal line driver circuit section 601 or the scan 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 may be formed outside the substrate.

[0219] The pixel section 602 includes a switching transistor 611, a current control transistor 612, and a lower electrode 613 electrically connected to a drain of the current control transistor 612. Note that a partition wall 614 is formed to cover end portions of the lower electrode 613. A positive photosensitive acrylic resin film, for example, can be used as the partition wall 614.

[0220] To achieve favorable coverage, the partition wall 614 is formed to have a curved surface with a curvature at its upper or lower end portion. For example, in the case where a positive photosensitive acrylic is used as the material of the partition wall 614, preferably only the upper end portion of the partition wall 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 wall 614.

[0221] Note that there is no particular limitation on the structure of the transistors (transistors 611, 612, 623, and 624). For example, a staggered transistor may be used. Furthermore, there is no particular limitation on the polarity of these transistors. For example, n-channel and p-channel transistors may be used for these transistors, or either n-channel transistors or p-channel transistors may be used. Furthermore, there is no particular limitation on the crystallinity of a semiconductor film used for the transistors. For example, an amorphous semiconductor film or a crystalline semiconductor film may be used. Examples of a semiconductor material 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 off-state current of the transistors can be reduced. Examples of the oxide semiconductor include an In-Ga oxide, 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)), and the like.

[0222] An EL layer 616 and an upper electrode 617 are formed over the lower electrode 613. Here, the lower electrode 613 serves as the anode and the upper electrode 617 serves as the cathode.

[0223] In addition, the EL layer 616 is formed by any of various methods, such as an evaporation method (including a vacuum evaporation method) using an evaporation mask, a droplet ejection method (also referred to as an inkjet method), a coating method such as a spin coating method, and a gravure printing method. As another material contained in the EL layer 616, a low-molecular compound or a high-molecular compound (including an oligomer or a dendrimer) can be used.

[0224] Note that a light-emitting element 618 is formed including 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 portion includes a plurality of light-emitting elements, the pixel portion may include either one of the light-emitting elements described in Embodiments 1 to 3 or a light-emitting element having a different structure.

[0225] When the sealing substrate 604 and the element substrate 610 are bonded together with the sealant 605, the light-emitting element 618 is provided in the region 607 enclosed by the element substrate 610, the sealing substrate 604, and the sealant 605. The region 607 is filled with a filler material. In some cases, the region 607 is filled with an inert gas (nitrogen, argon, or the like) or filled with a UV-curing resin or a 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 arranged in the recessed part, in which case deterioration due to the influence of moisture can be prevented.

[0226] An optical element 621 is provided under the sealing substrate 604 to overlap with the light-emitting element 618. An opaque layer 622 is provided under the sealing substrate 604. The structures of the optical element 621 and the opaque layer 622 may be the same as those of the optical element and the opaque layer of Embodiment 3, respectively.

[0227] 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 permeation as possible. A glass substrate, a quartz substrate, or a plastic substrate made of fiber-reinforced plastic (FRP), poly(vinyl fluoride) (PVF), polyester, acrylic, or the like can be used as the sealant substrate 604.

[0228] In the manner described above, a display device comprising any of the light-emitting elements and the optical elements described in Embodiments 1 to 3 can be obtained. <Strukturbeispiel 2 der Anzeigevorrichtung>

[0229] Next, another example of the display device is shown using Fig. 9A and Fig. 9B. It should be noted that Fig. 9A and Fig. 9B are each a cross-sectional view of a display device of an embodiment of the present invention.

[0230] In Fig. 9A, 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 portion 1042, a pixel portion 1040, a driving circuit portion 1041, lower electrodes 1024R, 1024G, and 1024B of the light-emitting elements, a partition wall 1025, an EL layer 1028, an upper electrode 1026 of the light-emitting elements, a sealing layer 1029, a sealing substrate 1031, a sealant 1032, and the like are illustrated.

[0231] In Fig. 9A, 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), are provided on a transparent base material 1033. An opaque layer 1035 may be further provided. The transparent base material 1033, which is provided with the color layers and the opaque layer, is located on and fixed to the substrate 1001. Note that the color layers and the opaque layer are covered with a covering layer 1036. In the structure in Fig. 9A, red light, green light, and blue light are transmitted through the color layers, and accordingly, an image can be displayed using the pixels of three colors.

[0232] Fig. 9B illustrates an example in which the color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) as examples of the optical elements are provided between the gate insulating film 1003 and the first interlayer insulating film 1020. As in this structure, the color layers may be arranged between the substrate 1001 and the sealing substrate 1031.

[0233] 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.

[0234] The display device described above has a structure in which light is taken out from the side of the substrate 1001 on which the transistors are formed (a bottom-emission structure), but it may have a structure in which light is taken out from the side of the sealing substrate 1031 (a top-emission structure). <Strukturbeispiel 3 der Anzeigevorrichtung>

[0235] Fig. 10A and Fig. 10B are each an example of a cross-sectional view of a display device having a top-emission structure. It should be noted that Fig. 10A and Fig. 10B are each a cross-sectional view illustrating the display device of an embodiment of the present invention, and the driving circuit section 1041, the peripheral section 1042 and the like shown in Fig. 9A and Fig. 9B are not shown in these.

[0236] In this case, a substrate that does not transmit light can be used as the substrate 1001. The process up to the step of forming a connection electrode connecting the transistor and the anode of the light-emitting element is performed in a manner similar to that of the display device with a bottom emission structure. Next, a third interlayer insulating film 1037 is formed to cover an electrode 1022. This insulating film may have a planarization function. The third interlayer insulating film 1037 may be formed using a material similar to that of the second interlayer insulating film, or may be formed using various other materials.

[0237] The lower electrodes 1024R, 1024G and 1024B of the light-emitting elements each serve as anode, but they can also serve as cathode. In the case of a Fig. 10A and Fig. In the display device having a top-emission structure shown in FIG. 10B, the lower electrodes 1024R, 1024G, and 1024B preferably further have a function of reflecting light. The upper electrode 1026 is provided above the EL layer 1028. Preferably, the upper electrode 1026 has a function of reflecting light as well as a function of transmitting light, 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 light having a specific wavelength is increased.

[0238] In case of a Fig. In the top-emission structure illustrated in Figure 10A, sealing can be performed 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 positioned between pixels. Note that a transparent substrate is advantageously used as the sealing substrate 1031.

[0239] Fig. 10A exemplifies the structure provided with the light-emitting elements and the color layers for the light-emitting elements; however, the structure is not limited thereto. For example, as shown in Fig. 10B, a structure including the red color layer 1034R and the blue color layer 1034B, but no green color layer, can be used to obtain a full-color display with the three colors of red, green, and blue. Fig. The structure shown in Figure 10A, 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. 10B, in which the light-emitting elements are provided with the red color layer and the blue color layer but without the green color layer, is effective for reducing power consumption due to a small energy loss of the light emitted from the green light-emitting element.

[0240] Although a display device including subpixels of three colors (red, green, and blue) was described above, the number of colors of subpixels may be four (red, green, blue, and yellow, or red, green, blue, and white). In this case, a color layer having a yellow light transmitting function or a function of transmitting light of a plurality of colors selected from blue, green, yellow, and red may be used. If the color layer can transmit light of a plurality of colors selected from blue, green, yellow, and red, light transmitted by the color layer may be white light. Since the light-emitting element that emits yellow or white light has high emission efficiency, the display device with such a structure can have low power consumption.

[0241] Furthermore, in the display device 600, which is shown in Fig. 8A and Fig. 8B, a sealing layer may be formed in the region 607 enclosed by the element substrate 610, the sealing substrate 604, and the sealant 605. For the sealing layer, a resin such as 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 may be used. Alternatively, an inorganic material such as silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, or aluminum nitride may be used. Forming the sealing layer in the region 607 can prevent the light-emitting element 618 from deteriorating due to contaminants such as water, which is preferable.Note that in the case where the sealing layer is formed, the sealant 605 is not necessarily provided.

[0242] When the sealing layer has a multi-layer structure, contaminants such as water can be effectively prevented from penetrating from the outside of the display device 600 into the light-emitting element 618 located inside the display device. In the case where the sealing layer has a multi-layer structure, a resin and an inorganic material are preferably stacked.

[0243] The structures described in this embodiment may be appropriately combined with any of the other structures of this embodiment and the other embodiments. (Embodiment 5)

[0244] In this embodiment, electronic devices, a light-emitting device, and lighting devices each including the light-emitting element of one embodiment of the present invention are described with reference to Fig. 11A to Fig. 11G, Fig. 12A to Fig. 12C and Fig. 13 described. <Elektronisches Gerät>

[0245] Fig. 11A to Fig. 11G show electronic devices. These electronic devices may each include a housing 9000, a display section 9001, a speaker 9003, operation buttons 9005 (including a power button or an operation switch), a connection terminal 9006, a sensor 9007 (a sensor having a function of measuring or detecting force, displacement, position, speed, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, electric power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared ray), a microphone 9008, and the like. Furthermore, the sensor 9007 may have a function of measuring biological information, just like a pulse sensor and a fingerprint sensor.

[0246] The electronic devices used in Fig. 11A to Fig. 11G may have various functions, such as a function for displaying various data (a still image, a moving image, a text image, and the like) on the display section, a touch sensor function, a function for displaying a calendar, the date, the time, and the like, a function for controlling a process with various types of software (programs), a wireless communication function, a function for connecting to various computer networks using a wireless communication function, a function for transmitting and receiving various data using a wireless communication function, a function for reading a program or data stored in a storage medium and displaying the program or data on the display section, and the like. It should be noted that functions of the electronic devices shown in Fig. 11A to Fig. 11G are not limited to those described above, and the electronic devices may have additional functions. Although Fig. 11A to Fig. 11G, the electronic devices may include a plurality of display sections. The electronic devices may have a camera or the like, and a function for capturing a still image, a function for capturing a moving image, a function for storing the captured image in a storage medium (an external storage medium or a storage medium built into the camera), a function for displaying the captured image on the display section, or the like.

[0247] The electronic devices in Fig. 11A to Fig. 11G are described in detail below.

[0248] Fig. 11A is a perspective view of a portable information terminal 9100. The display section 9001 of the portable information terminal 9100 is flexible. Therefore, the display section 9001 can be installed along a curved surface of a curved housing 9000. The display section 9001 further includes a touch sensor, and an operation can be performed by touching the screen with a finger, a stylus, or the like. For example, when an icon displayed on the display section 9001 is touched, an application can be launched.

[0249] Fig. 11B is a perspective view of a portable information terminal 9101. The portable information terminal 9101 serves, for example, as one or more of a telephone, a laptop, and an information search system. In particular, the portable information terminal can be used as a smartphone. Note that the speaker 9003, the connection terminal 9006, the sensor 9007, and the like shown in Fig. 11B, in the portable information terminal 9101, as in the portable information terminal 9100 shown in Fig. 11A. The portable information terminal 9101 can display characters and image information on its plurality of surfaces. For example, three operation buttons 9050 (also referred to as operation icons, or simply as icons) may be displayed on one surface of the display section 9001. In addition, information 9051 represented by dashed rectangles may be displayed on another surface of the display section 9001. Examples of the information 9051 include an indication indicating the arrival of an incoming email, a message from a social networking service (SNS), a call, and the like, the subject and sender of an email and an SNS message, the date, time, remaining battery capacity, and an indication indicating the strength of a received signal such as a radio wave.Instead of the information 9051, the operation buttons 9050 or the like may be displayed at the position where the information 9051 is displayed.

[0250] As the material for the casing 9000, for example, an alloy, a plastic, or ceramic can be used. A reinforced plastic can also be used as the plastic. A carbon fiber reinforced plastic (CFRP), which is a type of reinforced plastic, is advantageous in that it is lightweight and corrosion-free. Other examples of the reinforced plastic include one containing a glass fiber and one containing an aramid fiber. As the alloy, an aluminum alloy and a magnesium alloy can be cited. An amorphous alloy (also called metallic glass) containing zirconium, copper, nickel, and titanium, in particular, has high elastic strength.This amorphous alloy has a glass transition region at room temperature, is also called a bulk-solidified amorphous alloy, and essentially has an amorphous atomic structure. An alloy material is modeled into a shape of at least a part of the housing and solidified by a solidification-casting process, thereby forming a part of the housing with the bulk-solidified amorphous alloy. The amorphous alloy may contain, in addition to zirconium, copper, nickel, and titanium, beryllium, silicon, niobium, boron, gallium, molybdenum, tungsten, manganese, iron, cobalt, yttrium, vanadium, phosphorus, carbon, or the like. The amorphous alloy may be formed by a vacuum evaporation method, a sputtering method, an electroplating method, an electroless plating method, or the like instead of the solidification-casting method.The amorphous alloy may contain a microcrystal or a nanocrystal, as long as a state of no long-range order (a periodic structure) is maintained as a whole. Note that the term alloy includes both a complete solid-solution alloy with a single solid-phase structure and a partial solution with two or more phases. The casing 9000 using the amorphous alloy can exhibit high elastic strength. Even if the portable information terminal 9101 is dropped and the impact causes temporary deformation, the use of the amorphous alloy in the casing 9000 enables it to return to its original shape; accordingly, the shock resistance of the portable information terminal 9101 can be improved.

[0251] Fig. 11C is a perspective view of a portable information terminal 9102. The portable information terminal 9102 has a function of displaying information on three or more surfaces of the display section 9001. Here, information 9052, information 9053, and information 9054 are displayed on different surfaces. For example, a user of the portable information terminal 9102 can view the display (here, information 9053) with the portable information terminal 9102 placed in a breast pocket of his / her shirt. Specifically, the telephone number, name, or the like of a caller can be displayed in a location visible from above the portable information terminal 9102. Therefore, the user can view the display without removing the portable information terminal 9102 from the pocket and decide whether to answer the call.

[0252] Fig. 11D is a perspective view of a portable information terminal 9200 in the form of a wristwatch. The portable information terminal 9200 can run various applications, such as mobile phone calls, sending and receiving emails, displaying and editing text, playing music, Internet communication, and computer games. The display surface of the display section 9001 is curved, and images can be displayed on the curved display surface. The portable information terminal 9200 can utilize short-range communication according to an existing communication standard. For example, in this case, two-way communication can be performed between the portable information terminal 9200 and a headset capable of wireless communication, enabling hands-free telephone conversation.The portable information terminal 9200 includes the connection port 9006, and data can be sent and received directly to / from another information terminal via a connecting element. Charging with power through the connection port 9006 is possible. Note that charging can be performed without the connection port 9006 by wireless power supply.

[0253] Fig. 11E, Fig. 11F and Fig. 11G are perspective views of a foldable portable information terminal 9201. Fig. 11E is a perspective view illustrating the portable information terminal 9201 being opened. Fig. 11F is a perspective view illustrating the portable information terminal 9201 being changed from the opened state to the folded state or from the folded state to the opened state. Fig. 11G is a perspective view illustrating the portable information terminal 9201 being folded. The portable information terminal 9201 is highly portable when folded. When the portable information terminal 9201 is opened, a seamless large display area is easily browsed. The display section 9001 of the portable information terminal 9201 is supported by three housings 9000 connected to each other by hinges 9055. By folding the portable information terminal 9201 at a junction between two housings 9000 at the hinges 9055, the shape of the portable information terminal 9201 can be reversibly changed from the opened state to the folded state. For example, the portable information terminal 9201 can be bent with a radius of curvature greater than or equal to 1 mm and less than or equal to 150 mm.

[0254] Examples of electronic devices include a television set (also called a TV or TV receiver), a monitor for a computer or the like, a camera such as a digital camera or digital video camera, a digital photo frame, a mobile phone (also called a cellular phone or portable telephone device), video glasses (a head-mounted display), a portable game console, a portable information terminal, an audio playback device, and a large gaming machine such as a pachinko machine.

[0255] Furthermore, the electronic device of one embodiment of the present invention may comprise a secondary battery. Preferably, the secondary battery can be charged by contactless energy transfer.

[0256] Examples of the secondary battery include a lithium-ion secondary battery such as a lithium polymer battery (lithium-ion polymer battery) using a gel electrolyte, a lithium-ion battery, a nickel-hydride battery, a nickel-cadmium battery, an organic radical battery, a lead-acid battery, an air secondary battery, a nickel-zinc battery, and a silver-zinc battery.

[0257] The electronic device of one embodiment of the present invention may include an antenna. When a signal is received from the antenna, the electronic device can display an image, data, or the like on a display section. If the electronic device includes a secondary battery, the antenna can be used for contactless power transmission.

[0258] The electronic device or lighting device of one embodiment of the present invention has flexibility and can therefore be integrated along a curved interior / exterior wall surface of a house or building, or along a curved interior / exterior surface of a car. For example, the electronic device or lighting device can be used for lighting a dashboard, windshield, vehicle ceiling, and the like. <Licht emittierende Vorrichtung>

[0259] Fig. 12A is a perspective view of a light-emitting device 3000 shown in this embodiment, and Fig. 12B is a cross-sectional view taken along the dashed line EF in Fig. 12A. It should be noted that in Fig. 12A some components are represented by dashed lines to avoid complicating the drawing.

[0260] The light emitting device 3000, which in Fig. 12A and Fig. 12B includes a substrate 3001, a light-emitting element 3005 over the substrate 3001, a first sealing region 3007 provided around the light-emitting element 3005, and a second sealing region 3009 provided around the first sealing region 3007.

[0261] Light is emitted from the light-emitting element 3005 via the substrate 3001 and / or a substrate 3003. In Fig. 12A and Fig. 12B, a structure in which light is emitted from the light-emitting element 3005 toward the lower side (the substrate 3001 side) is illustrated.

[0262] As in Fig. 12A and Fig. As shown in Figure 12B, the light-emitting device 3000 has a double sealing structure in which the light-emitting element 3005 is enclosed by the first sealing region 3007 and the second sealing region 3009. With the double sealing structure, the entry of impurities (e.g., water, oxygen, and the like) from the outside into the light-emitting element 3005 can be advantageously suppressed. Note that it is unnecessary to provide both the first sealing region 3007 and the second sealing region 3009. For example, only the first sealing region 3007 may be provided.

[0263] It should be noted that in Fig. 12B, the first sealing region 3007 and the second sealing region 3009 are provided in contact with the substrate 3001 and the substrate 3003, respectively. However, without being limited to such a structure, for example, the first sealing region 3007 and / or the second sealing region 3009 may be provided in contact with an insulating film or a conductive film provided on the substrate 3001. Alternatively, the first sealing region 3007 and / or the second sealing region 3009 may be provided in contact with an insulating film or a conductive film provided on the substrate 3003.

[0264] Substrate 3001 and substrate 3003 may have structures similar to those of substrate 200 and substrate 220 described in the above embodiment, respectively. Light-emitting element 3005 may have a structure similar to that of any of the light-emitting elements described in the above embodiments.

[0265] For the first sealing portion 3007, a material containing glass (e.g., a glass frit, a glass ribbon, and the like) can be used. For the second sealing portion 3009, a material containing a resin can be used. By using the material containing glass for the first sealing portion 3007, productivity and sealing performance can be improved. Furthermore, by using the material containing a resin for the second sealing portion 3009, impact resistance and heat resistance can be improved. However, the materials used for the first sealing portion 3007 and the second sealing portion 3009 are not limited to these, and the first sealing portion 3007 can be formed using the material containing a resin, and the second sealing portion 3009 can be formed using the material containing glass.

[0266] The glass frit may contain, for example, magnesium oxide, calcium oxide, strontium oxide, barium oxide, cesium oxide, sodium oxide, potassium oxide, boron oxide, vanadium oxide, zinc oxide, tellurium oxide, aluminum oxide, silicon dioxide, lead oxide, tin oxide, phosphorus oxide, ruthenium oxide, rhodium oxide, iron oxide, copper oxide, manganese dioxide, molybdenum oxide, niobium oxide, titanium oxide, tungsten oxide, bismuth oxide, zirconium oxide, lithium oxide, antimony oxide, lead borate glass, tin phosphate glass, vanadate glass, or borosilicate glass. The glass frit preferably contains at least one type of transition metal to absorb infrared light.

[0267] For the above glass frits, for example, a frit paste is applied to a substrate and subjected to heat treatment, laser light irradiation, or the like. The frit paste contains the glass frit and a resin (also called a binder) diluted with an organic solvent. Note that an absorbent that absorbs light with the wavelength of the laser light may be added to the glass frit. For example, an Nd:YAG laser or a semiconductor laser is preferably used as the laser. The shape of the laser light can be circular or square.

[0268] For the above resin-containing material, for example, polyester, polyolefin, polyamide (e.g., nylon, aramid), polyimide, polycarbonate, or an acrylic resin, polyurethane, or epoxy resin can be used. Alternatively, a material containing a resin with a siloxane bond, such as silicone, can be used.

[0269] Note that in the case where the material containing glass is used for the first sealing portion 3007 and / or the second sealing portion 3009, the material containing glass preferably has a thermal expansion coefficient close to that of the substrate 3001. With the above structure, the formation of a crack in the material containing glass or the substrate 3001 due to thermal stress can be suppressed.

[0270] For example, the following advantageous effects can be obtained in the case where the material containing glass is used for the first sealing portion 3007 and the material containing a resin is used for the second sealing portion 3009.

[0271] The second sealing portion 3009 is provided closer to an outer portion of the light-emitting device 3000 than the first sealing portion 3007. In the light-emitting device 3000, deformation due to external force or the like increases toward the outer portion. Accordingly, the outer portion of the light-emitting device 3000, which is more deformed, that is, the second sealing portion 3009, is sealed using the material containing a resin, and the first sealing portion 3007, provided on an inner side of the second sealing portion 3009, is sealed using the material containing glass, whereby the light-emitting device 3000 is less likely to be damaged even if deformation due to external force or the like occurs.

[0272] Furthermore, as in Fig. 12B, a first region 3011 corresponds to the region enclosed by the substrate 3001, the substrate 3003, the first sealing region 3007, and the second sealing region 3009. A second region 3013 corresponds to the region enclosed by the substrate 3001, the substrate 3003, the light-emitting element 3005, and the first sealing region 3007.

[0273] The first region 3011 and the second region 3013 are preferably filled with, for example, an inert gas such as a rare gas or a nitrogen gas. Alternatively, the first region 3011 and the second region 3013 are preferably filled with a resin such as an acrylic resin or an epoxy resin. Note that for the first region 3011 and the second region 3013, a reduced pressure state is preferable to an atmospheric pressure state.

[0274] Fig. Figure 12C shows a modification example of the structure in Fig. 12B. Fig. 12C is a cross-sectional view illustrating the modification example of the light-emitting device 3000.

[0275] Fig. Fig. 12C illustrates a structure in which a desiccant 3018 is provided in a recessed portion provided in a part of the substrate 3003. The other components are the same as those of the structure shown in Fig. 12B.

[0276] As the desiccant 3018, a substance that adsorbs moisture and the like by chemical adsorption or a substance that adsorbs moisture and the like by physical adsorption can be used. Examples of the substance that can be used as the desiccant 3018 include alkali metal oxides, alkaline earth metal oxides (such as calcium oxide, barium oxide, and the like), sulfate, metal halides, perchlorate, zeolite, silica gel, and the like. <beleuchtungsvorrichtung>

[0277] Fig. 13 illustrates an example in which the light-emitting element is used for an indoor lighting device 8501. Since the light-emitting element can have a larger area, a lighting device with a large area can also be formed. In addition, a lighting device 8502 in which a light-emitting region has a curved surface can also be formed using a housing with a curved surface. The light-emitting element described in this embodiment is in the form of a thin film, which makes it possible to design the housing more freely. Consequently, the lighting device can be artistically designed in various ways. Furthermore, a wall of the room can be provided with a large lighting device 8503.Touch sensors may be arranged in the lighting devices 8501, 8502 and 8503 to control the switching on or off of the lighting devices.

[0278] Furthermore, when the light-emitting element is used on the surface side of a table, a lighting device 8504 having a function as a table can be obtained. When the light-emitting element is used as part of another piece of furniture, a lighting device having a function as the relevant piece of furniture can be obtained.

[0279] As described above, display modules, light-emitting devices, electronic devices, and lighting devices can be obtained using the light-emitting element of one embodiment of the present invention. Note that the light-emitting element can be used for electronic devices in various fields, without being limited to the lighting devices and electronic devices described in this embodiment.

[0280] The structure described in this embodiment may be used in a suitable combination with any of the structures described in the other embodiments. [Example 1]

[0281] In this example, examples of manufacturing light-emitting elements of the embodiments of the present invention and characteristics of the light-emitting elements are described. The structure of each of the light-emitting elements manufactured in this example is the same as that described in Fig. 1. Table 1 and Table 2 show the detailed structures of the elements. In addition, the structures and abbreviations of the compounds used here are given below. [Table 1] Schicht Bezugszeichen Dicke (nm) Material Gewichtsverhältnis Licht emittierendes Element 1 Elektrode 102 200 Al - Elektroneninjektionsschicht 119 1 LiF - Elektronentransportschicht 118(2) 15 BPhen - 118(1) 10 Pm-01 - Light-emitting layer 130 30 Pm-01 : Ir(iPrpim)3 1:0,06 Hole transport layer 112 20 PCCP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 110 ITSO - Light-emitting element 2 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 15 BPhen - 118(1) 10 Pm-01 - Light-emitting layer 130 30 PCCP : Pm-01 : Ir(iPrpim)3 0,33:0,66:0,06 Hole transport layer 112 20 PCCP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 110 ITSO - Light-emitting element 3 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 15 BPhen - 118(1) 10 Pm-01 - Light-emitting layer 130 30 PCCP : Pm-01 : Ir(iPrpim)3 0,66:0,33:0,06 Hole transport layer 112 20 PCCP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 110 ITSO - Light-emitting element 4 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 15 BPhen - 118(1) 10 Pm-01 - Light-emitting layer 130 30 PCCP : Ir(iPrpim)3 1:0,06 Hole transport layer 112 20 PCCP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 110 ITSO - [Table 2] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting element 5 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 15 BPhen - 118(1) 10 Pm-01 - Light-emitting layer 130 30 PCCP : Pm-01 : Ir(iPrpim)3 0,3:0,6:0,05 Hole transport layer 112 20 PCCP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 110 ITSO - Light-emitting element 6 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 15 BPhen - 118(1) 10 Pm-01 - Light-emitting layer 130 30 PCCP : Pm-01 : Ir(iPrpim)3 0,3:0,6:0,1 Hole transport layer 112 20 PCCP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 110 ITSO - Light-emitting element 7 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 15 BPhen - 118(1) 10 Pm-01 - Light-emitting layer 130 30 PCCP : Pm-01 : Ir(iPrpim)3 0,3:0,6:0,2 Hole transport layer 112 20 PCCP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 110 ITSO - Light-emitting element 8 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 15 BPhen - 118(1) 10 Pm-01 - Light-emitting layer 130 30 PCCP : Pm-01 : Ir(iPrpim)3 0,3:0,6:0,3 Hole transport layer 112 20 PCCP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 110 ITSO - <Herstellung der Licht emittierenden Elemente>

[0282] Methods for manufacturing the light-emitting elements of this example are described below. <Herstellung des Licht emittierenden Elements 1>

[0283] As electrode 101, an ITSO film with a thickness of 110 nm was formed over a glass substrate. The electrode area of ​​electrode 101 was 4 mm 2 (2 mm × 2 mm).

[0284] As hole injection layer 111, DBT3P-II and molybdenum oxide (MoO3) were deposited over the electrode 101 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 in a thickness of 60 nm.

[0285] Next, PCCP was deposited as hole transport layer 112 by evaporation to a thickness of 20 nm over the hole injection layer 111.

[0286] Next, 4-[3'-(9H-carbazol-9-yl)-1,1'-biphenyl-3-yl]-2,6-diphenylpyrimidine (abbreviation: Pm-01) and Tris{2-[1-(2,6-diisopropylphenyl)-1H-imidazol-2-yl-κN 3 [phenyl-κC]iridium(III) (abbreviation: Ir(iPrpim)3) is deposited by co-evaporation over the hole-transport layer 112 in a weight ratio of Pm-01:Ir(iPrpim)3 = 1:0.06 to a thickness of 30 nm. In the light-emitting layer 130, Ir(iPrpim)3 corresponds to the guest material (the first organic compound) and Pm-01 to the host material (the second organic compound).

[0287] As the electron-transport layer 118, Pm-01 and BPhen were successively deposited by evaporation in a thickness of 10 nm and 15 nm, respectively, over the light-emitting layer 130. As the electron-injection layer 119, LiF was subsequently deposited by evaporation in a thickness of 1 nm over the electron-transport layer 118.

[0288] As electrode 102, aluminum (Al) was deposited in a thickness of 200 nm over the electron injection layer 119.

[0289] Next, the light-emitting element 1 was sealed in a glove box having a nitrogen atmosphere by fixing a glass substrate for sealing to a glass substrate on which the organic materials were deposited using a sealant for an organic EL device. Specifically, after the sealant was applied to enclose the organic materials deposited on the glass substrate and the glass substrates were bonded together, irradiation with UV light having a wavelength of 365 nm at 6 J / cm 2 and a heat treatment at 80 °C for one hour. This process resulted in the light-emitting element 1. <Herstellung der Licht emittierenden Elemente 2 bis 8>

[0290] The light-emitting elements 2 to 8 were manufactured through the same steps as those of the light-emitting element 1, except for the step of forming the light-emitting layer 130.

[0291] As the light-emitting layer 130 of the light-emitting element 2, PCCP, Pm-01 and Ir(iPrpim)3 were deposited by co-evaporation in a weight ratio of PCCP:Pm-01:Ir(iPrpim)3 = 0.33:0.66:0.06 to a thickness of 30 nm.

[0292] As the light-emitting layer 130 of the light-emitting element 3, PCCP, Pm-01 and Ir(iPrpim)3 were deposited by co-evaporation in a weight ratio of PCCP:Pm-01:Ir(iPrpim)3 = 0.66:0.33:0.06 to a thickness of 30 nm.

[0293] As the light-emitting layer 130 of the light-emitting element 4, PCCP and Ir(iPrpim)3 were deposited by co-evaporation in a weight ratio of PCCP:Ir(iPrpim)3 = 1:0.06 to a thickness of 30 nm. Note that the light-emitting element 4 is a comparative light-emitting element in which the light-emitting layer does not contain the second organic compound Pm-01.

[0294] As the light-emitting layer 130 of the light-emitting element 5, PCCP, Pm-01 and Ir(iPrpim)3 were deposited by co-evaporation in a weight ratio of PCCP:Pm-01:Ir(iPrpim)3 = 0.3:0.6:0.05 to a thickness of 30 nm.

[0295] As the light-emitting layer 130 of the light-emitting element 6, PCCP, Pm-01 and Ir(iPrpim)3 were deposited by co-evaporation in a weight ratio of PCCP:Pm-01:Ir(iPrpim)3 = 0.3:0.6:0.1 to a thickness of 30 nm.

[0296] As the light-emitting layer 130 of the light-emitting element 7, PCCP, Pm-01 and Ir(iPrpim)3 were deposited by co-evaporation in a weight ratio of PCCP:Pm-01:Ir(iPrpim)3 = 0.3:0.6:0.2 to a thickness of 30 nm.

[0297] As the light-emitting layer 130 of the light-emitting element 8, PCCP, Pm-01 and Ir(iPrpim)3 were deposited by co-evaporation in a weight ratio of PCCP:Pm-01:Ir(iPrpim)3 = 0.3:0.6:0.3 to a thickness of 30 nm. <Eigenschaften der Licht emittierenden Elemente>

[0298] Next, the properties of the fabricated light-emitting elements 1 to 8 were measured. The luminance and CIE chromaticity were measured using a luminance colorimeter (BM-5A, manufactured by TOPCON TECHNOHOUSE CORPORATION). The electroluminescence spectrum was measured using a multi-channel spectrometer (PMA-11, manufactured by Hamamatsu Photonics KK).

[0299] Fig. 14, Fig. 15, Fig. 16 and Fig. 17 shows the luminance-current density characteristics, the luminance-voltage characteristics, the current efficiency-luminance characteristics, and the power efficiency-luminance characteristics of the light-emitting elements 1 to 4, respectively. Fig. 20, Fig. 21, Fig. 22 and Fig. 23 show the luminance-current density characteristics, the luminance-voltage characteristics, the current efficiency-luminance characteristics, and the power efficiency-luminance characteristics of the light-emitting elements 5 to 8, respectively. The measurement of the light-emitting elements was conducted at room temperature (in an atmosphere maintained at 23 °C).

[0300] Tables 3 and 4 show the element properties of the light-emitting elements 1 to 8 at about 1000 cd / m 2 . [Table 3] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x;y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (lm / W) Light-emitting element 1 3,40 6,14 (0,278;0,431) 960 15,6 14,4 Light-emitting element 2 3,40 3,87 (0,261;0,414) 800 20,7 19,2 Light-emitting element 3 4,00 4,20 (0,225;0,371) 1070 25,3 19,9 Light-emitting element 4 6,80 4,82 (0,185;0,313) 1020 21,2 9,8 [Table 4] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x;y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (lm / W) Light-emitting element 5 4,00 4,60 (0,227;0,376) 1090 23,8 18,7 Light-emitting element 6 4,00 3,83 (0,241;0,392) 930 24,4 19,2 Light-emitting element 7 4,00 4,21 (0,293;0,438) 850 20,2 15,9 Light-emitting element 8 4,00 4,89 (0,321;0,456) 890 18,1 14,2

[0301] Fig. 18 and Fig. 24 shows the electroluminescence spectra at the time when a current with a current density of 2.5 mA / cm 2 flows.

[0302] As in Fig. 18 and Fig. 24, the electroluminescence spectrum of the light-emitting element 4 has a peak at a wavelength of 470 nm and mainly represents blue light emission. Whereas, the electroluminescence spectra of the light-emitting elements 1 to 3 and the light-emitting elements 5 to 8 not only have a peak at a wavelength of 470 nm and represent blue light emission, but also represent broad light emission in a wavelength range from green to yellow. In the light-emitting elements 1 to 8, the half-widths of the electroluminescence spectra are 119 nm, 106 nm, 75 nm, 54 nm, 83 nm, 92 nm, 134 nm, and 153 nm, respectively. The electroluminescence spectra of the light-emitting elements 1 to 3 and the light-emitting elements 5 to 8 have a broader spectrum shape than the electroluminescence spectrum of the light-emitting element 4.Whereas the electroluminescence spectrum of the light-emitting element 4 has a narrow spectrum shape and thus mainly represents light emitted by the guest material Ir(iPrpim)3.

[0303] Next, difference spectra obtained by subtracting the electroluminescence spectrum of the light-emitting element 4 from each of the electroluminescence spectra of the light-emitting elements 1 to 3 and the light-emitting elements 5 to 8 normalized by the intensity of the peak wavelength of the light-emitting element 4 are Fig. 19 and Fig. 25. As the Fig. 19 and the Fig. 25, the light-emitting elements 1 to 3 and the light-emitting elements 5 to 8 have a broad light emission in the yellow wavelength range in addition to the light emission of the guest material represented by the electroluminescence spectrum of the light-emitting element 4. Furthermore, the peak wavelengths of the broad light emission are approximately in the range of 540 nm to 550 nm. Furthermore, the intensity ratios of the light emission of the guest material to the broad light emission in the light-emitting element 1, the light-emitting element 2, the light-emitting element 3, the light-emitting element 5, the light-emitting element 6, the light-emitting element 7, and the light-emitting element 8 are 1:0.65, 1:0.45, 1:0.20, 1:0.22, 1:0.29, 1:0.68, and 1:1.04, respectively.

[0304] The combination of Pm-O1 and Ir(iPrpim)3 used in the light-emitting layers of light-emitting elements 1 to 3 and light-emitting elements 5 to 8 forms an exciplex, as described later. Thus, it can be stated that the reason behind the broad spectra of light-emitting elements 1 to 3 and light-emitting elements 5 to 8 lies in the fact that light emission is obtained from the exciplex formed by Pm-O1 and Ir(iPrpim)3.

[0305] Light-emitting element 2 and light-emitting element 3 contain PCCP (the third organic compound) in addition to Pm-O1 (the second organic compound) and Ir(iPrpim)3 (the first organic compound). Light-emitting element 1 does not contain PCCP (the third organic compound). Light-emitting element 4 does not contain Pm-O1 (the second organic compound). Light-emitting element 3 has a higher PCCP content than light-emitting element 2. Thus, it was found that the proportion of broad light emission originating from the exciplex formed by Pm-O1 (the second organic compound) and Ir(iPrpim)3 (the first organic compound) differs between light-emitting elements 1 to 4.In this way, by changing the proportion of PCCP (the third organic compound) in the light-emitting layer, the interaction between Pm-O1 (the second organic compound) and Ir(iPrpim)3 (the first organic compound) can be controlled; thus, the generation ratio of the exciplex formed by Pm-O1 (the second organic compound) and Ir(iPrpim)3 (the first organic compound) can be controlled. As a result, the emission color of a light-emitting element can be controlled.

[0306] Furthermore, the proportion of Ir(iPrpim)3 (the first organic compound) in the light-emitting layers increases steadily from the light-emitting element 5 to the light-emitting element 8. It has been found that, as a result, the proportion of broad light emission originating from the exciplex formed by Pm-O1 (the second organic compound) and Ir(iPrpim)3 (the first organic compound) differs between the light-emitting elements 5 to 8. In this way, by changing the proportion of Ir(iPrpim)3 (the first organic compound) in the light-emitting layer, the interaction between Pm-O1 (the second organic compound) and Ir(iPrpim)3 (the first organic compound) can be controlled; and thus, the generation ratio of the exciplex formed by Pm-O1 (the second organic compound) and Ir(iPrpim)3 (the first organic compound) can be controlled.As a result, the emission color of a light-emitting element can be controlled.

[0307] Again Fig. 14 to Fig. 17, the Fig. 20 to Fig. 23 and Tables 3 and 4, the light-emitting elements 1 to 3 and the light-emitting elements 5 to 8 are driven at a lower voltage than the light-emitting element 4. Furthermore, the power efficiency of each of the light-emitting elements 1 to 3 and the light-emitting elements 5 to 8 is higher than that of the light-emitting element 4, that is, higher than or equal to 10 μm / W. Consequently, the light-emitting element of one embodiment of the present invention containing the first organic compound (Ir(iPrpim)3) and the second organic compound (Pm-01) can be driven at a low voltage and has low power consumption.

[0308] Furthermore, it was found that the light-emitting element 2, the light-emitting element 3, and the light-emitting elements 5 to 8 have a current efficiency higher than or equal to 20 cd / A. In other words, a light-emitting element having a structure in which a light-emitting layer contains another material (PCCP) in addition to the first organic compound (Ir(iPrpim)3) and the second organic compound (Pm-01) has high current efficiency. <Ergebnisse der CV-Messung>

[0309] The electrochemical properties (oxidation reaction properties and reduction reaction properties) of the above compounds were measured by cyclic voltammetry (CV). Note that an electrochemical analyzer (ALS Model 600A or 600C, manufactured by BAS Inc.) was used for the measurement, and the measurement was performed on a solution obtained by dissolving each compound in N,N-dimethylformamide (abbreviation: DMF). During the measurements, the potential of a working electrode with respect to the reference electrode was changed within an appropriate range to obtain the oxidation peak potential and the reduction peak potential. Furthermore, the HOMO and LUMO levels of each compound were calculated from the assumed redox potential of the reference electrode of -4.94 eV and the obtained peak potentials.

[0310] According to the CV measurement results, the oxidation potential and reduction potential of Pm-01 were 0.95 V and -2.17 V, respectively. Furthermore, the HOMO level and LUMO level of Pm-01 calculated from the CV measurement were -5.89 eV and -2.78 eV, respectively. Thus, the LUMO level of Pm-01 was found to be low. Furthermore, the oxidation potential of Ir(iPrpim)3 was 0.11 V. The HOMO level of Ir(iPrpim)3 calculated from the CV measurement was -5.05 eV. Thus, the HOMO level of Ir(iPrpim)3 was found to be high. It should be noted that the LUMO level of Ir(iPrpim)3 was presumably high because the reduction potential of Ir(iPrpim)3 was low, and a reduction peak was not clearly observed. Furthermore, the oxidation potential and reduction potential of PCCP were 0.685 V and -2.98 V, respectively. Furthermore, the HOMO and LUMO levels of PCCP, calculated from the CV measurement, were -5.63 eV and -1.96 eV, respectively.

[0311] As described above, the LUMO level of Pm-01 is lower than the LUMO level of PCCP and the LUMO level of Ir(iPrpim)3, and the HOMO level of Ir(iPrpim)3 is higher than the HOMO level of PCCP and the HOMO level of Pm-01. Thus, in the case where the compounds are used in a light-emitting layer, as in the light-emitting elements 1 to 3 and the light-emitting elements 5 to 8, electrons and holes serving as charge carriers are efficiently injected from a pair of electrodes into Pm-01 and Ir(iPrpim)3, so that Pm-01 and Ir(iPrpim)3 can form an exciplex.

[0312] The exciplex formed by Pm-01 and Ir(iPrpim)3 has the LUMO level in Pm-01 and the HOMO level in Ir(iPrpim)3. The energy difference between the LUMO level of Pm-01 and the HOMO level of Ir(iPrpim)3 is 2.28 eV. This value is essentially equal to the light emission energy determined from the peak wavelength of the electroluminescence spectrum of the light-emitting element 8 in Fig. 24 (2.28 eV). Furthermore, this value also essentially corresponds to the light emission energy in a wide wavelength range of the electroluminescence spectra of the light-emitting elements 1 to 3 ( Fig. 18) and the light-emitting elements 5 to 7 ( Fig. 24). These results imply that the electroluminescence spectra of light-emitting elements 1 to 3 and light-emitting elements 5 to 8 represent the light emission from the exciplex formed by Pm-01 and Ir(iPrpim)3, and the light emission from Ir(iPrpim)3, respectively. Note that since the difference between the S1 level and the T1 level of the exciplex is small, the light emission energy can be regarded as the energy of the T1 level of the exciplex (2.28 eV). <Messung des T1-Niveaus>

[0313] Next, in order to obtain the T1 levels of the compounds used in the light-emitting layer 130, thin films of Pm-01 and PCCP were each formed over a quartz substrate by a vacuum evaporation method, and then the emission spectra of these thin films were measured at a low temperature (10 K).

[0314] The measurement was performed using a PL microscope, LabRAM HR-PL, manufactured by HORIBA, Ltd., a He-Cd laser with a wavelength of 325 nm as excitation light and a CCD detector at a measurement temperature of 10 K.

[0315] In addition to the measurement of normal emission spectra, time-resolved emission spectra were also measured, focusing on long-lifetime light emission. Since the measurement temperature was set to a low temperature (10 K) for this emission spectra measurement, phosphorescence was observed in addition to fluorescence, which is the main emission component, in the measurement of normal emission spectra. Furthermore, phosphorescence was mainly observed in the measurement of time-resolved emission spectra, focusing on long-lifetime light emission. The time-resolved emission spectra of Pm-01 and PCCP, which were measured at a low temperature, are shown in Figure 1. Fig. 26 and Fig. 27 shown.

[0316] As shown in the measurement results of the emission spectra, the emission spectrum of Pm-01 has a peak (including a shoulder) of the phosphorescent component on the shortest wavelength side at 451 nm, and the emission spectrum of PCCP has a peak (including a shoulder) of the phosphorescent component on the shortest wavelength side at 467 nm.

[0317] Thus, from the peak wavelengths, the T1 level of Pm-01 and the T1 level of PCCP were calculated to be 2.75 eV and 2.66 eV, respectively. <Absorptionsspektren der Gastmaterialien>

[0318] Fig. Figure 28 shows the measurement result of the absorption spectrum of Ir(iPrpim)3, which is a guest material used in the above light-emitting elements.

[0319] To measure the absorption spectrum, a dichloromethane solution was prepared in which Ir(iPrpim)3 was dissolved, and a quartz cell was used. The absorption spectrum was measured using a UV-VIS spectrophotometer (V-550, manufactured by JASCO Corporation). Subsequently, the absorption spectra of a quartz cell and a solvent were subtracted from the measured spectrum of the sample. The measurement was performed at room temperature (in an atmosphere maintained at 23 °C).

[0320] As in Fig. As shown in Figure 28, the absorption edge on the lowest energy side (the longest wavelength side) of the absorption spectrum of Ir(iPrpim)3 is located at approximately 460 nm. The absorption edge was calculated from the absorption spectrum data, and the transition energy was estimated assuming a direct transition. It was found that the absorption edge of Ir(iPrpim)3 was located at 474 nm, and the transition energy was 2.61 eV. Since Ir(iPrpim)3 is a phosphorescent compound, the absorption edge on the lowest energy side is an absorption band due to a triplet MLCT transition. Consequently, the T1 level of Ir(iPrpim)3 was calculated from the absorption edge to be 2.61 eV.

[0321] According to the above measurement results, the T1 level of PCCP and the T1 level of Pm-01 are higher than the T1 level of Ir(iPrpim)3, and the T1 level of Ir(iPrpim)3 is higher than the energy level of the exciplex formed by Pm-01 and Ir(iPrpim)3 (2.28 eV), in other words, higher than the T1 level of the exciplex. Thus, both the light emission of the exciplex formed by Ir(iPrpim)3 and Pm-01 and the light emission of Ir(iPrpim)3 can be efficiently obtained.

[0322] The energy level of the exciplex is lower than the energy difference (3.67 eV) between the LUMO level and the HOMO level of PCCP and lower than the energy difference (3.11 eV) between the LUMO level and the HOMO level of Pm-01. Therefore, the formation of the exciplex can produce a light-emitting element with a low drive voltage.

[0323] One embodiment of the present invention can provide a light-emitting element with high emission efficiency. One embodiment of the present invention can provide a light-emitting element that emits light in a broad emission spectrum. One embodiment of the present invention can further provide a light-emitting element with low drive voltage and low power consumption. [Example 2]

[0324] In this example, examples of manufacturing light-emitting elements of the embodiments of the present invention and characteristics of the light-emitting elements are described. The structure of each of the light-emitting elements manufactured in this example is the same as that described in Fig. 1. Table 5 shows details of the elemental structure. In addition, the structures and abbreviations of the compounds used herein are given below. [Table 5] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting element 9 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 15 BPhen - 118(1) 10 4.6mCzP2Pm - Light-emitting layer 130(2) 10 4.6mCzP2Pm : Ir(mpptz-diPrp)3 1:0,06 130(1) 30 PCCP : 4.6mCzP2Pm : Ir(mpptz-diPrp)3 1:0,3:0,06 Hole transport layer 112 20 PCCP - Hole injection layer 111 15 DBT3P-II : MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting element 10 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 15 BPhen - 118(1) 10 35DCzPPy - Light-emitting layer 130(2) 10 35DCzPPy : Ir(mpptz-diPrp)3 1:0,06 130(1) 30 PCCP : 35DCzPPy : Ir(mpptz-diPrp)3 1:0,3:0,06 Hole transport layer 112 20 PCCP - Hole injection layer 111 15 DBT3P-II : MoO3 1:0,5 electrode 101 70 ITSO - <Herstellung der Licht emittierenden Elemente>

[0325] Methods for manufacturing the light-emitting elements of this example are described below. (Production of the light-emitting element 9)

[0326] As electrode 101, an ITSO film with a thickness of 70 nm was formed over a glass substrate. The electrode area of ​​electrode 101 was 4 mm 2 (2 mm × 2 mm).

[0327] As hole injection layer 111, DBT3P-II and molybdenum oxide (MoO3) were deposited over the electrode 101 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 in a thickness of 15 nm.

[0328] Next, PCCP was deposited as hole transport layer 112 by evaporation to a thickness of 20 nm over the hole injection layer 111.

[0329] Next, as the light-emitting layer 130, PCCP, 4,6mCzP2Pm and Tris{2-[5-(2-methylphenyl)-4-(2,6-diisopropylphenyl)-4H-1,2,4-triazol-3-yl-κN2]p henyl-κC}iridium(III) (abbreviation: Ir(mpptz-diPrp)3) were co-evaporated over the hole transport layer 112 in a weight ratio of PCCP:4,6mCzP2Pm:Ir(mpptz-diPrp)3 = 1:0.3:0.06 to a thickness of 30 nm, and then 4,6mCzP2Pm and Ir(mpptz-diPrp)3 were co-evaporated in a weight ratio of 4.6mCzP2Pm:Ir(mpptz-diPrp)3 = 1:0.06 was deposited at a thickness of 10 nm. In the light-emitting layer 130, Ir(mpptz-diPrp)3 corresponds to the guest material (the first organic compound) and 4.6mCzP2Pm to the host material (the second organic compound).

[0330] Next, 4.6mCzP2Pm and BPhen were successively deposited by evaporation over the light-emitting layer 130 as the electron-transport layer 118 to a thickness of 10 nm and 15 nm, respectively. LiF was then deposited by evaporation over the electron-transport layer 118 to a thickness of 1 nm, as the electron-injection layer 119.

[0331] As electrode 102, aluminum (Al) was deposited in a thickness of 200 nm over the electron injection layer 119.

[0332] Next, the light-emitting element 9 was sealed in a glove box having a nitrogen atmosphere by fixing a glass substrate for sealing to a glass substrate over which the organic materials were deposited using a sealant for an organic EL device. For the detailed procedure, refer to the description of the light-emitting element 1. Through the above steps, the light-emitting element 9 was obtained. (Manufacturing of the light-emitting element 10)

[0333] A light-emitting element 10 was manufactured through the same steps as those of the light-emitting element 9, except for the steps of forming the light-emitting layer 130 and the electron-transport layer 118.

[0334] As the light-emitting layer 130 of the light-emitting element 2, PCCP, 35DCzPPy, and Ir(mpptz-diPrp)3 were co-evaporated in a weight ratio of PCCP: 35DCzPPy:Ir(mpptz-diPrp)3 = 1:0.3:0.06 to a thickness of 30 nm. Subsequently, 35DCzPPy and Ir(mpptz-diPrp)3 were co-evaporated in a weight ratio of 35DCzPPy:Ir(mpptz-diPrp)3 = 1:0.06 to a thickness of 10 nm. In the light-emitting layer 130, Ir(mpptz-diPrp)3 corresponds to the guest material (the first organic compound), and 35DCzPPy to the host material (the second organic compound).

[0335] As electron transport layer 118, 35DCzPPy and BPhen were successively deposited by evaporation in a thickness of 10 nm and 15 nm respectively over the light-emitting layer 130. <Eigenschaften der Licht emittierenden Elemente>

[0336] Fig. 29, Fig. 30, Fig. 31 and Fig. 32 show the luminance-current density characteristics, the luminance-voltage characteristics, the current efficiency-luminance characteristics, and the power efficiency-luminance characteristics of the fabricated light-emitting elements 9 and 10, respectively. Note that the measurement for each light-emitting element was performed at room temperature (in an atmosphere maintained at 23°C) by a measurement method similar to that used in Example 1.

[0337] Table 6 shows the element properties of the light-emitting elements 9 and 10 at about 1000 cd / m 2 . [Table 6] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x;y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) Licht emittierendes Element 9 4,00 2,17 (0189;0,411) 1050 48,4 38,0 Licht emittierendes Element 10 4,40 2,01 (0,170;0,371) 1220 60,7 43,3

[0338] Fig. Figure 33 shows the electroluminescence spectra at the time when a current with a current density of 2.5 mA / cm 2 flows.

[0339] As in Fig. 33, the electroluminescence spectra of the light-emitting elements 9 and 10 have a half-width of 74 nm and 64 nm, respectively, and the light-emitting element 9 has a wider electroluminescence spectrum than the light-emitting element 10. The electroluminescence spectrum of the light-emitting element 9 not only has a peak at a wavelength of 473 nm and represents blue light emission, but also represents broad light emission in a wavelength range of green. Whereas, in the light-emitting element 10, light is mainly emitted from the guest material Ir(mpptz-diPrp)3.

[0340] Next, a difference spectrum obtained by subtracting the electroluminescence spectrum of the light-emitting element 10 from the electroluminescence spectrum of the light-emitting element 9 normalized by the intensity of the peak wavelength of the light-emitting element 10 is Fig. 34. As the Fig. As can be seen from Figure 34, the light-emitting element 9 exhibits light emission on the long wavelength side in addition to the light emission from the guest material, which is represented by the electroluminescence spectrum of the light-emitting element 10. Furthermore, the peak wavelength of the long wavelength side is approximately 520 nm. Furthermore, the intensity ratio of the light emission originating from the guest material to the light emission on the long wavelength side in the light-emitting element 9 is 1:0.15.

[0341] The combination of 4,6mCzP2Pm and Ir(mpptz-diPrp)3 used in the light-emitting layer of the light-emitting element 9 forms an exciplex, as described later. Thus, it can be stated that the reason behind the broad spectrum of the light-emitting element 9 lies in the fact that light emission is obtained from the exciplex formed by 4,6mCzP2Pm and Ir(mpptz-diPrp)3.

[0342] Again Fig. 29 to Fig. As can be seen from Figure 32 and Table 6, the light-emitting element 9 is driven at a lower voltage than the light-emitting element 10. Furthermore, the power efficiency of the light-emitting element 9 is high. Consequently, the light-emitting element of one embodiment of the present invention containing the first organic compound (Ir(mpptz-diPrp)3) and the second organic compound (4,6mCzP2Pm) can be driven at a low voltage and has low power consumption. <Ergebnisse der CV-Messung>

[0343] The electrochemical properties (oxidation reaction properties and reduction reaction properties) of the above compounds were measured by cyclic voltammetry (CV). Note that the measurement method is similar to that used in Example 1. Furthermore, for the measurement results of PCCP, please refer to Example 1.

[0344] According to the CV measurement results, the oxidation potential and reduction potential of 4.6mCzP2Pm were 0.95 V and -2.06 V, respectively. Furthermore, the HOMO and LUMO levels of 4.6mCzP2Pm, calculated from the CV measurement, were -5.89 eV and -2.88 eV, respectively. Thus, the LUMO level of 4.6mCzP2Pm was found to be low. Furthermore, the oxidation potential and reduction potential of Ir(mpptz-diPrp)3 were 0.34 V and -2.98 V, respectively. The HOMO and LUMO levels of Ir(mpptz-diPrp)3, calculated from the CV measurement, were -5.28 eV and -1.96 eV, respectively. Thus, the HOMO level of Ir(mpptz-diPrp)3 was found to be high. Furthermore, the oxidation potential and reduction potential of 35DCzPPy were 0.96 V and -2.56 V, respectively. Furthermore, the HOMO level and LUMO level of 35DCzPPy, calculated from the CV measurement, were -5.90 eV and -2.39 eV, respectively.

[0345] As described above, the LUMO level of 4,6mCzP2Pm is lower than the LUMO level of PCCP and the LUMO level of Ir(mpptz-diPrp)3, and the HOMO level of Ir(mpptz-diPrp)3 is higher than the HOMO level of PCCP and the HOMO level of 4,6mCzP2Pm. Thus, in the case where the compounds are used in a light-emitting layer, as in the light-emitting element 9, electrons and holes serving as charge carriers are efficiently injected from a pair of electrodes into 4,6mCzP2Pm and Ir(mpptz-diPrp)3, so that 4,6mCzP2Pm and Ir(mpptz-diPrp)3 can form an exciplex.

[0346] The exciplex formed by 4,6mCzP2Pm and Ir(mpptz-diPrp)3 further exhibits the LUMO level in 4,6mCzP2Pm and the HOMO level in Ir(mpptz-diPrp)3. The energy difference between the LUMO level of 4,6mCzP2Pm and the HOMO level of Ir(mpptz-diPrp)3 is 2.40 eV. This value is essentially equal to the light emission energy in a broad wavelength range of the electroluminescence spectrum of the light-emitting element 9 in Fig. 33 (2.38 eV). These results imply that the electroluminescence spectrum of the light-emitting element 9 represents the light emission from the exciplex formed by 4,6mCzP2Pm and Ir(mpptz-diPrp)3 and the light emission from Ir(mpptz-diPrp)3. Note that since the difference between the S1 level and the T1 level of the exciplex is small, the light emission energy can be considered the energy of the T1 level of the exciplex (2.38 eV).

[0347] Note that the LUMO level of 35DCzPPy is lower than the LUMO level of PCCP and the LUMO level of Ir(mpptz-diPrp)3, and the HOMO level of Ir(mpptz-diPrp)3 is higher than the HOMO level of PCCP and the HOMO level of 35DCzPPy. Thus, in the case where the compounds are used in a light-emitting layer, as in the light-emitting element 10, electrons and holes serving as charge carriers are efficiently injected from a pair of electrodes into 35DCzPPy and Ir(mpptz-diPrp)3.

[0348] However, the energy difference between the LUMO level of 35DCzPPy and the HOMO level of Ir(mpptz-diPrp)3 is as large as 2.90 eV. Since this energy difference is larger than the light emission energy obtained from the peak wavelength of the electroluminescence spectrum of the light-emitting element 10, which is Fig. 33 (2.61 eV), the light emission from the excited Ir(mpptz-diPrp)3 is energetically more stable than the exciplex formation by 35DCzPPy and Ir(mpptz-diPrp)3. In other words, the combination of 35DCzPPy and Ir(mpptz-diPrp)3 does not form an exciplex. The light emission from the exciplex formed by 35DCzPPy and Ir(mpptz-diPrp)3 is not observed by the light-emitting element 10. <Messung des T1-Niveaus>

[0349] Next, to obtain the T1 levels of the compounds used in the light-emitting layer 130, the emission spectra of 4,6mCzP2Pm and 35DCzPPy were measured at a low temperature (10 K). Note that the measurement method is similar to that used in Example 1. Furthermore, for the measurement results of PCCP, reference can be made to Example 1. Time-resolved emission spectra of 4,6mCzP2Pm and 35DCzPPy measured at a low temperature are shown in Figure 1, respectively. Fig. 35 and Fig. 36 shown.

[0350] As shown in the measurement results of the emission spectra, the emission spectrum of 4.6mCzP2Pm exhibits a peak (including a shoulder) of the phosphorescent component on the shortest wavelength side at 459 nm, and the emission spectrum of 35DCzPPy exhibits a peak (including a shoulder) of the phosphorescent component on the shortest wavelength side at 451 nm.

[0351] Thus, from the peak wavelengths, the T1 level of 4.6mCzP2Pm and the T1 level of 35DCzPPy were calculated to be 2.70 eV and 2.75 eV, respectively. <Absorptionsspektren der Gastmaterialien>

[0352] Fig. Figure 37 shows the measurement result of the absorption spectrum of Ir(mpptz-diPrp)3, a guest material used in the light-emitting elements. Note that the measurement method is similar to that used in Example 1.

[0353] As in Fig. As shown in Figure 37, the absorption edge on the lowest energy side (the longest wavelength side) of the absorption spectrum of Ir(mpptz-diPrp)3 is located at approximately 460 nm. The absorption edge was obtained from absorption spectrum data, and the transition energy was estimated assuming a direct transition. It was found that the absorption edge of Ir(mpptz-diPrp)3 was located at 472 nm, and its transition energy was 2.63 eV. Since Ir(mpptz-diPrp)3 is a phosphorescent compound, the absorption edge on the lowest energy side is an absorption band due to a triplet MLCT transition. As a result, the T1 level of Ir(mpptz-diPrp)3 was calculated from the absorption edge to be 2.63 eV.

[0354] According to the above measurement results, the T1 level of PCCP and the T1 level of 4,6mCzP2Pm are higher than the T1 level of Ir(mpptz-diPrp)3, and the T1 level of Ir(mpptz-diPrp)3 is higher than the energy level of the exciplex formed by 4,6mCzP2Pm and Ir(mpptz-diPrp)3 (2.38 eV), in other words, higher than the T1 level of the exciplex. Thus, both the light emission of the exciplex formed by Ir(mpptz-diPrp)3 and 4,6mCzP2Pm and the light emission of Ir(mpptz-diPrp)3 can be efficiently obtained.

[0355] The energy level of the exciplex is lower than the energy difference (3.67 eV) between the LUMO level and the HOMO level of PCCP and lower than the energy difference (3.01 eV) between the LUMO level and the HOMO level of 4.6mCzP2Pm. Therefore, the formation of the exciplex can yield a low-voltage light-emitting device.

[0356] The T1 level of PCCP and the T1 level of 35DCzPPy are higher than the T1 level of Ir(mpptz-diPrp)3, and the T1 level of Ir(mpptz-diPrp)3 is lower than the energy difference (2.90 eV) between the LUMO level of 35DCzPPy and the HOMO level of Ir(mpptz-diPrp)3. Thus, the light emission from the excited Ir(mpptz-diPrp)3 is energetically more stable than the formation of an exciplex by 35DCzPPy and Ir(mpptz-diPrp)3. In other words, the combination of 35DCzPPy and Ir(mpptz-diPrp)3 does not form an exciplex. The light emission from the exciplex formed by 35DCzPPy and Ir(mpptz-diPrp)3 is not observed from the light-emitting element 10. <Zeitaufgelöste Emissionsmessung>

[0357] Next, a thin film sample comprising the combination of the compounds used in the above light-emitting layer was prepared, and then the transient emission characteristics thereof were measured using a time-resolved emission measurement.

[0358] As thin film 1, 4.6mCzP2Pm and Ir(mpptz-diPrp)3 were deposited over a quartz substrate by co-evaporation in a weight ratio of 4.6mCzP2Pm:Ir(mpptz-diPrp)3 = 1:0.125 in a thickness of 50 nm.

[0359] As thin film 2, 35DCzPPy and Ir(mpptz-diPrp)3 were deposited over a quartz substrate by co-evaporation in a weight ratio of 35DCzPPy:Ir(mpptz-diPrp)3 = 1:0.125 in a thickness of 50 nm.

[0360] A picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics KK) was used for the measurement. In this measurement, the thin film was irradiated with a pulsed laser, and the light emission from the thin film, which was attenuated by the laser irradiation, was subjected to time-resolved measurement using a streak camera to measure the light emission lifetime of the thin film. A nitrogen gas laser with a wavelength of 337 nm was used as the pulsed laser. The thin film was irradiated with a pulsed laser with a pulse width of 500 ps at a repetition rate of 10 Hz. By summing the data obtained from the repeated measurements, data with a high S / N ratio were obtained. The measurement was performed at room temperature (in an atmosphere maintained at 23 °C).

[0361] Fig. Figure 38 shows the transient emission properties of thin films 1 and 2 obtained by the measurements.

[0362] The transient emission properties of thin film 2 exhibit a first-order decay that fits well with a monoexponential function. Furthermore, it was found that the transient emission properties of thin film 1 include a delayed emission component in addition to an immediate emission component. In other words, it was suggested that the light emission of thin film 1 includes light emission from at least two components.

[0363] Next, Fig. 39 the emission spectra of the immediate emission component and the delayed emission component of the thin film 1. The emission spectrum of the immediate emission component is a spectrum obtained by measuring the emission of the thin film 1 in a period from -0.8 µs to 0.9 µs, and the emission spectrum of the delayed emission component is a spectrum obtained by measuring the emission of the thin film 1 in a period from 0.9 µs to 44 µs.

[0364] As in Fig. As shown in Figure 39, the emission spectrum of the immediate emission component and the emission spectrum of the delayed emission component of the thin film 1 have different spectrum shapes. As shown in the emission spectra, the emission wavelength of the light emission of the delayed emission component is longer than the emission wavelength of the light emission of the immediate emission component.

[0365] The light emission energy (2.39 eV), calculated from the peak wavelength of the emission spectrum of the delayed emission component of thin film 1, is essentially equal to the energy of the exciplex formed by 4,6mCzP2Pm and Ir(mpptz-diPrP)3. Since the exciplex has a function of emitting thermally activated delayed fluorescence, it can be assumed that the delayed emission component of thin film 1 exhibits light emission due to the exciplex formed by 4,6mCzP2Pm and Ir(mpptz-diPrP)3.

[0366] As described above, the light-emitting element 9 manufactured in this example is a light-emitting element of one embodiment of the present invention, which comprises the first organic compound (Ir(mpptz-diPrP)3) and the second organic compound (4,6mCzP2Pm), the combination of which forms an exciplex.

[0367] One embodiment of the present invention can provide a light-emitting element with high emission efficiency. One embodiment of the present invention can provide a light-emitting element that emits light in a broad emission spectrum. One embodiment of the present invention can further provide a light-emitting element with low drive voltage and low power consumption. [Example 3]

[0368] This example describes the emission properties of thin films that can be used in a light-emitting element according to one embodiment of the present invention. Structures and abbreviations of the compounds used in this example are given below. <Herstellung der Dünnfilmproben>

[0369] As thin film 3, m-MTDATA and bis[2-methyl-3-(6-tert-butyl-4-pyrimidinyl-κN 3 )pyridyl-κC](2,4-pentanedionato-κ 2 O,O')iridium(III) (abbreviation: Ir(tBumpypm)2(acac)) was deposited over a quartz substrate by co-evaporation in a weight ratio of m-MTDATA:Ir(tBumpypm)2(acac) = 1:0.01 in a thickness of 50 nm.

[0370] As thin film 4, m-MTDATA and Ir(tBumpypm)2(acac) were deposited over a quartz substrate by co-evaporation in a weight ratio of m-MTDATA:Ir(tBumpypm)2(acac) = 1:0.25 in a thickness of 50 nm.

[0371] As thin film 5, mCP and Ir(tBumpypm)2(acac) were deposited over a quartz substrate by co-evaporation in a weight ratio of mCP:Ir(tBumpypm)2(acac) = 1:0.01 in a thickness of 50 nm.

[0372] As thin film 6, mCP and Ir(tBumpypm)2(acac) were deposited over a quartz substrate by co-evaporation in a weight ratio of mCP:Ir(tBumpypm)2(acac) = 1:0.25 in a thickness of 50 nm. <emissionsspektrum>

[0373] The emission spectra of the thin films 3 to 6 prepared above were measured. Note that the emission spectra were measured using a PL-EL meter (manufactured by Hamamatsu Photonics KK). The measurement was performed at room temperature (in an atmosphere maintained at 23 °C). Measurement results are shown in Fig. 40 and Fig. 41 shown.

[0374] Green light emission emitted by the phosphorescent compound Ir(tBumpypm)2(acac) was observed from thin film 5 and thin film 6. Whereas, in addition to the light emission from Ir(tBumpypm)2(acac), light emission with a broad spectrum covering the long wavelength side was observed from thin film 3 and thin film 4. <Zeitaufgelöste Emissionsmessung>

[0375] Next, a time-resolved emission measurement was performed on thin films 3 to 6. A picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics KK) was used for the measurement. The measurement procedure is similar to that used in Example 2.

[0376] In Fig. 42 and Fig. 43 shows the measured transient emission properties of thin films 3 to 6.

[0377] The transient emission properties of thin films 5 and 6 exhibit attenuation curves close to a monoexponential function. In contrast, the transient emission properties of thin films 3 and 4 have been found to include a delayed emission component in addition to an immediate emission component. In other words, it has been suggested that the light emission of thin films 3 and 4 includes light emission from at least two components. <Ergebnisse der CV-Messung>

[0378] The electrochemical properties (oxidation reaction properties and reduction reaction properties) of the above compounds were measured by cyclic voltammetry (CV). Note that the measurement method is similar to that used in Example 1.

[0379] According to the CV measurement results, the oxidation potential and reduction potential of m-MTDATA were 0.04 V and -2.72 V, respectively. Furthermore, the HOMO level and LUMO level of m-MTDATA, calculated from the CV measurement, were -4.98 eV and -2.22 eV, respectively. Thus, the HOMO level of m-MTDATA was found to be high. Furthermore, the oxidation potential and reduction potential of Ir(tBumpypm)2(acac) were 0.91 V and -2.04 V, respectively. Furthermore, the HOMO level and LUMO level of Ir(tBumpypm)2(acac) calculated from the CV measurement were -5.85 eV and -2.90 eV, respectively. Thus, the LUMO level of Ir(tBumpypm)2(acac) was found to be low. The oxidation potential of mPC was 0.97 V. The HOMO level of mCp, calculated from the CV measurement, was -5.91 eV. Note that the LUMO level of mCP was presumably high because the reduction potential of mCP was low, and a reduction peak was not clearly observed.

[0380] As described above, the LUMO level of Ir(tBumpypm)2(acac) is lower than the LUMO level of m-MTDATA, and the HOMO level of Ir(tBumpypm)2(acac) is lower than the HOMO level of m-MTDATA. Thus, the combination of Ir(tBumpypm)2(acac) and m-MTDATA can form an exciplex.

[0381] The exciplex formed by Ir(tBumpypm)2(acac) and m-MTDATA has the LUMO level in Ir(tBumpypm)2(acac) and the HOMO level in m-MTDATA. Furthermore, the energy difference between the LUMO level of Ir(tBumpypm)2(acac) and the HOMO level of m-MTDATA is 2.08 eV. This value is essentially equal to the light emission energy (2.06 eV) obtained from the peak wavelength of the emission spectrum of thin film 4 formed in Fig. 40. These results imply that the emission spectra of thin films 3 and 4 represent the light emission from the exciplex formed by Ir(tBumpypm)2(acac) and m-MTDATA, and the light emission from Ir(tBumpypm)2(acac). Note that since the difference between the S1 level and the T1 level of the exciplex is small, the light emission energy can be regarded as the energy of the T1 level of the exciplex (2.06 eV).

[0382] Note that the HOMO level of mCP is lower than that of Ir(tBumpypm)2(acac). Thus, the combination of mCP and Ir(tBumpypm)2(acac) does not form an exciplex. Light emission from the exciplex formed by mCP and Ir(tBumpypm)2(acac) is not observed in thin films 5 and 6. <Messung des T1-Niveaus>

[0383] Next, to obtain the T1 levels of the compounds used in thin films 3 and 4, the emission spectrum of m-MTDATA was measured at a low temperature (10 K). Note that the measurement method is similar to that used in Example 1. A time-resolved emission spectrum of m-MTDATA measured at a low temperature is shown in Fig. 44 shown.

[0384] As shown in the emission spectrum measurement results, the emission spectrum of m-MTDATA exhibits a peak (including a shoulder) of the phosphorescent component on the shortest wavelength side at 484 nm. Thus, from the peak wavelength, the T1 level of m-MTDATA was calculated to be 2.56 eV. <Absorptionsspektren der Gastmaterialien>

[0385] Fig. Figure 45 shows the measurement results of the absorption spectrum of Ir(tBumpypm)2(acac), which is the guest material in thin films 3 and 4. Note that the measurement method is similar to that used in Example 1.

[0386] As in Fig. As shown in Figure 45, the absorption edge on the lowest energy side (the longest wavelength side) of the absorption spectrum of Ir(tBumpypm)2(acac) is located at approximately 490 nm. The absorption edge was obtained from absorption spectrum data, and the transition energy was estimated assuming a direct transition. It was found that the absorption edge of Ir(mpptz-diPrp)3 was located at 496 nm, and its transition energy was 2.50 eV. Since Ir(tBumpypm)2(acac) is a phosphorescent compound, the absorption edge on the lowest energy side is an absorption band due to a triplet MLCT transition. Consequently, the T1 level of Ir(tBumpypm)2(acac) was calculated from the absorption edge to be 2.50 eV.

[0387] According to the above measurement results, the T1 level of m-MTDATA is higher than the T1 level of Ir(tBumpypm)2(acac), and the T1 level of Ir(tBumpypm)2(acac) is higher than the energy difference (2.08 eV) between the LUMO level of Ir(tBumpypm)2(acac) and the HOMO level of m-MTDATA or higher than the light emission energy of the exciplex formed by Ir(tBumpypm)2(acac) and m-MTDATA (2.06 eV), in other words, higher than the T1 level of the exciplex. Thus, both the light emission of the exciplex formed by Ir(tBumpypm)2(acac) and m-MTDATA and the light emission of Ir(tBumpypm)2(acac) can be efficiently obtained.

[0388] As described above, the thin films 3 and 4 prepared in this example are thin films comprising the first organic compound (Ir(tBumpypm)2(acac)) and the second organic compound (m-MTDATA), the combination of which forms an exciplex, and the films can be appropriately applied to a light-emitting element of one embodiment of the present invention.

[0389] With an embodiment of the present invention, a light-emitting element can be provided that emits light in a broad emission spectrum.< / emissionsspektrum> < / beleuchtungsvorrichtung> < / substrat> < / elektroneninjektionsschicht> < / elektronentransportschicht> < / lochtransportschicht> < / lochinjektionsschicht> < / material>

Claims

[1] Light-emitting element (150) comprising: a light-emitting layer (130) comprising a first organic compound and a second organic compound, wherein a LUMO level of the first organic compound is higher than or equal to a LUMO level of the second organic compound, wherein a HOMO level of the first organic compound is higher than or equal to a HOMO level of the second organic compound, wherein a combination of the first organic compound and the second organic compound forms an exciplex, wherein the first organic compound is configured to convert triplet excitation energy into light emission, wherein a lowest triplet excitation level of the second organic compound is higher than or equal to a lowest triplet excitation level of the first organic compound, wherein the lowest triplet excitation level of the first organic compound is higher than or equal to a lowest triplet excitation level of the exciplex, and wherein light emission from the light-emitting layer (130) comprises light emission from the first organic compound and light emission from the exciplex. [2] Light-emitting element (150) comprising: a light-emitting layer (130) comprising a first organic compound and a second organic compound, wherein a LUMO level of the first organic compound is higher than or equal to a LUMO level of the second organic compound, wherein a HOMO level of the first organic compound is higher than or equal to a HOMO level of the second organic compound, wherein a combination of the first organic compound and the second organic compound forms an exciplex, wherein the first organic compound is a metal-organic complex having an absorption band based on a triplet MLCT transition, wherein a lowest triplet excitation level of the second organic compound is higher than or equal to a lowest triplet excitation level of the first organic compound, wherein the lowest triplet excitation level of the first organic compound is higher than or equal to a lowest triplet excitation level of the exciplex, and wherein light emission from the light-emitting layer (130) comprises light emission from the first organic compound and light emission from the exciplex. [3] The light-emitting element (150) of claim 2, wherein the second organic compound is configured to transport an electron. [4] The light-emitting element (150) of claim 2, wherein the second organic compound comprises a π-electron-deficient heteroaromatic framework. [5] Light-emitting element (150) according to claim 2, wherein the light-emitting layer (130) further comprises a third organic compound, and where a HOMO level of the third organic compound is higher than or equal to the HOMO level of the second organic compound. [6] Light-emitting element (150) according to claim 2, wherein the light-emitting layer (130) further comprises a third organic compound, wherein a HOMO level of the third organic compound is higher than or equal to the HOMO level of the second organic compound, and wherein the third organic compound is configured to transport a hole. [7] Light-emitting element (150) according to claim 2, wherein the light-emitting layer (130) further comprises a third organic compound, and wherein the third organic compound comprises a π-electron-rich heteroaromatic framework and / or an aromatic amine framework. [8] The light-emitting element (150) according to claim 1 or 2, wherein an intensity ratio of the light emission from the exciplex to the light emission from the first organic compound is in the range of 1:9 to 9:

1. [9] The light-emitting element (150) according to claim 1 or 2, wherein the light emission from the exciplex has a higher intensity than the light emission from the first organic compound. [10] The light-emitting element (150) of claim 1 or 2, wherein the first organic compound comprises iridium. [11] Light-emitting element (150) according to claim 1 or 2, wherein the first organic compound comprises a ligand coordinated to iridium, and wherein the ligand comprises a five-membered nitrogen-containing heterocyclic framework. [12] Display device comprising: the light-emitting element (150) according to claim 1 or 2; and at least one of a color filter and a transistor. [13] Electronic device comprising: the display device according to claim 1 or 2; and at least one of a housing and a touch sensor. [14] Lighting device comprising: the light-emitting element (150) according to claim 1 or 2; and at least one of a housing and a touch sensor. [15] Light-emitting element (150) comprising: a light-emitting layer (130) comprising a first organic compound and a second organic compound, wherein the second organic compound is configured to transport an electron, wherein a LUMO level of the first organic compound is higher than or equal to a LUMO level of the second organic compound, wherein a HOMO level of the first organic compound is higher than or equal to a HOMO level of the second organic compound, wherein a combination of the first organic compound and the second organic compound forms an exciplex, wherein a lowest triplet excitation level of the second organic compound is higher than or equal to a lowest triplet excitation level of the first organic compound, wherein the lowest triplet excitation level of the first organic compound is higher than or equal to a lowest triplet excitation level of the exciplex, and wherein light emission from the light-emitting layer (130) comprises light emission from the first organic compound and light emission from the exciplex. [16] The light-emitting element (150) according to claim 15, wherein an intensity ratio of the light emission from the exciplex to the light emission from the first organic compound is in the range of 1:9 to 9:

1. [17] The light-emitting element (150) of claim 15, wherein the light emission from the exciplex has a higher intensity than the light emission from the first organic compound. [18] The light-emitting element (150) of claim 15, wherein the first organic compound comprises iridium. [19] Light-emitting element (150) according to claim 15, wherein the first organic compound comprises a ligand coordinated to iridium, and wherein the ligand comprises a five-membered nitrogen-containing heterocyclic framework. [20] The light-emitting element (150) of claim 15, wherein the second organic compound comprises a π-electron-deficient heteroaromatic framework. [21] Light-emitting element (150) according to claim 15, wherein the light-emitting layer (130) further comprises a third organic compound, and where a HOMO level of the third organic compound is higher than or equal to the HOMO level of the second organic compound. [22] Light-emitting element (150) according to claim 15, wherein the light-emitting layer (130) further comprises a third organic compound, wherein a HOMO level of the third organic compound is higher than or equal to the HOMO level of the second organic compound, and wherein the third organic compound is configured to transport a hole. [23] Light-emitting element (150) according to claim 15, wherein the light-emitting layer (130) further comprises a third organic compound, and wherein the third organic compound comprises a π-electron-rich heteroaromatic framework and / or an aromatic amine framework. [24] The light-emitting element (150) according to claim 15, wherein the weight ratio of the first organic compound to the second organic compound is greater than or equal to 0.01 and less than or equal to 0.

5. [25] Light-emitting element (150) comprising: a light-emitting layer (130) comprising a guest material (131) and a host material (132), wherein the host material (132) is configured to transport an electron, wherein the guest material (131) is configured to transport a hole, wherein a LUMO level of the guest material (131) is higher than or equal to a LUMO level of the host material (132), wherein a HOMO level of the guest material (131) is higher than or equal to a HOMO level of the host material (132), wherein a combination of the guest material (131) and the host material (132) forms an exciplex, wherein a lowest triplet excitation level of the host material (132) is higher than or equal to a lowest triplet excitation level of the guest material (131), wherein the lowest triplet excitation level of the guest material (131) is higher than or equal to a lowest triplet excitation level of the exciplex, and wherein light emission from the light-emitting layer (130) comprises light emission from the guest material (131) and light emission from the exciplex. [26] The light-emitting element (150) according to claim 25, wherein an intensity ratio of the light emission from the exciplex to the light emission from the guest material (131) is in the range of 1:9 to 9:

1. [27] The light-emitting element (150) of claim 25, wherein the light emission from the exciplex has a higher intensity than the light emission from the guest material (131). [28] The light-emitting element (150) of claim 25, wherein the guest material (131) comprises iridium. [29] Light-emitting element (150) according to claim 25, wherein the guest material (131) comprises a ligand coordinated to iridium, and wherein the ligand comprises a five-membered nitrogen-containing heterocyclic framework. [30] The light-emitting element (150) of claim 25, wherein the host material (132) comprises a π-electron-deficient heteroaromatic framework. [31] Light-emitting element (150) according to claim 25, wherein the light-emitting layer (130) further comprises an organic compound, and where a HOMO level of the organic compound is higher than or equal to the HOMO level of the host material (132). [32] Light-emitting element (150) according to claim 25, wherein the light-emitting layer (130) further comprises an organic compound, wherein a HOMO level of the organic compound is higher than or equal to the HOMO level of the host material (132), and wherein the organic compound is configured to transport a hole. [33] Light-emitting element (150) according to claim 25, wherein the light-emitting layer (130) further comprises an organic compound, and wherein the organic compound comprises a π-electron-rich heteroaromatic framework and / or an aromatic amine framework. [34] The light-emitting element (150) according to claim 25, wherein the weight ratio of the guest material (131) to the host material (132) is greater than or equal to 0.01 and less than or equal to 0.5.

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