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

Abstract

Light-emitting device comprising: a first electrode (101); a light-emitting layer (130) above the first electrode (101), wherein the light-emitting layer (130) comprises: a first organic compound (131) for converting triplet excitation energy into light; a second organic compound (132) with a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton; and a third organic compound (133) for converting singlet excitation energy into light; and a second electrode (102) above the light-emitting layer (130), wherein light emitted by the light-emitting layer (130) includes light emitted by the third organic compound (133) and wherein the first organic compound (131) comprises Ru, Rh, Pd, Os, Ir or Pt.

Description

Technical field

[0001] One embodiment of the present invention relates to a light-emitting device, a display device, an electronic device and a lighting device, each comprising the light-emitting element.

[0002] It should be noted that an embodiment of the present invention is not limited to the aforementioned technical field. The technical field of an embodiment of the invention disclosed in this description and the like relates to an object, a method, or a manufacturing process. An embodiment of the present invention relates to a process, a machine, a product, or a composition. Specific examples of the technical field of an embodiment of the present invention disclosed in this description include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, an energy storage device, a storage device, a control method for any one of them, and a manufacturing process for any one of them. State of the art

[0003] In recent years, intensive research and development has been conducted on light-emitting elements that utilize electroluminescence (EL). In a basic structure of such a light-emitting element, a layer containing a light-emitting substance (an EL layer) is positioned between a pair of electrodes. Applying a voltage between the electrodes of this element causes light to be emitted by the light-emitting substance.

[0004] Since the aforementioned light-emitting element is of a self-illuminating type, a display device using this light-emitting element offers the following advantages: high visibility, no need for backlighting, and low power consumption. Furthermore, such a display device also offers the following advantages: thinness, light weight, and high response speed.

[0005] In a light-emitting cell (EL cell) where an EL layer containing an organic compound as the light-emitting substance is positioned between a pair of electrodes (e.g., in an organic EL cell), applying a voltage between the electrodes causes electrons from a cathode and holes from an anode to be injected into the light-emitting EL layer, resulting in a current flow. Recombination of the injected electrons and holes excites the light-emitting organic compound to a state that produces light emission.

[0006] An organic compound can be in a singlet (S*) or triplet (T*) excitation state. Light emission from the singlet excitation state is called fluorescence, and light emission from the triplet excitation state is called phosphorescence. The statistical generation ratio of these states in a light-emitting element is assumed to be S*:T* = 1:3. Therefore, a light-emitting element containing a phosphorescent compound has a higher emission efficiency than a light-emitting element containing a fluorescent compound. For this reason, light-emitting elements containing phosphorescent compounds capable of converting triplet excitation energy into light have been actively developed in recent years.

[0007] Among light-emitting elements containing phosphorescent compounds, a light-emitting element that emits blue light, in particular, has not yet been used in practice because it is difficult to develop a stable compound with a high triplet excitation energy level. For this reason, light-emitting elements containing more stable fluorescent compounds have been developed, and a technique for increasing the emission efficiency of a light-emitting element containing a fluorescent compound (a fluorescent element) has been investigated.

[0008] A well-known example is a light-emitting element containing a thermally activated delayed fluorescent (TADF) material. In a thermally activated delayed fluorescent material, a singlet excitation state is generated from a triplet excitation state by reverse intersystem crossing, and the singlet excitation energy is converted into light.

[0009] Patent document 1 discloses a method: In a light-emitting element containing a thermally activated, delayed fluorescent material and a fluorescent compound, the singlet excitation energy of the thermally activated, delayed fluorescent material is transferred to the fluorescent compound and light emission is obtained from the fluorescent compound. [Reference][Patent document]

[0010] Patent Document 1: JP 2014-045179 A [Non-patent document]

[0011] Non-patent document 1: T. Sajoto et al., J. Am. Chem. Soc., 2009, 131, pp. 9813-9822

[0012] WO2017 / 115788A1 relates to an organic electroluminescent device comprising an anode, an emitting layer, and a cathode. The emitting layer contains a delayed fluorescent first compound, a fluorescent second compound, and a third compound represented by Cz-Az. The second compound emits light with a main peak wavelength in the range of 430 nm to 540 nm.

[0013] US2011 / 0309345A1 relates to a compound of formula (I) for an organic electroluminescent device.

[0014] US2010 / 0265187A1 concerns the signal guidance for an organic light-emitting diode (OLED) structure that includes a submersible sensor configuration.

[0015] US2005 / 0089715A1 relates to an OLED device comprising an anode and a cathode and having between them a light-emitting layer containing a light-emitting dopant and a host material comprising a monoanthracene derivative of formula (I).

[0016] WO2017 / 109637A1 relates to a compound comprising a benzofuropyrimidine framework or a benzothienopyrimidine framework, a first substituent, and a second substituent. The first and second substituents each comprise a furan framework, a thiophene framework, or a pyrrole framework, respectively. The document further discloses a light-emitting element comprising this compound. Disclosure of the invention

[0017] To increase the emission efficiency of a fluorescent element, efficient generation of a singlet excitation state from a triplet excitation state and highly efficient energy transfer to a fluorescent material are desirable. Accordingly, there is a need to develop a method and a material for efficiently generating a singlet excitation state from a triplet excitation state to further increase the emission efficiency of a light-emitting element. Furthermore, a material with advantageous charge carrier transport properties must be used for the light-emitting layer to reduce the drive voltage.

[0018] In light of the foregoing, one object of an embodiment of the present invention is to provide a light-emitting element with high emission efficiency. Another object of an embodiment of the present invention is to provide a light-emitting element with a low drive voltage. Another object of an embodiment of the present invention is to provide a very reliable light-emitting element. 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 electronic device.

[0019] It should be noted that the description of the foregoing tasks does not preclude the existence of further tasks. In one embodiment of the present invention, it is unnecessary to fulfill all tasks. Further tasks will become apparent from the explanation of the description and the like, and can be derived from it.

[0020] As described above, there is an increasing demand for the development of a method for the efficient conversion of the triplet excitation energy of a fluorescent element into light. Therefore, the energy transfer efficiency between materials used in the light-emitting layer must be improved.

[0021] In light of the foregoing, one embodiment of the present invention is a light-emitting device according to claim 1. The light-emitting device comprises a light-emitting layer between a pair of electrodes. The light-emitting layer contains a first organic compound, a second organic compound, and a third organic compound. The first organic compound has a function for converting triplet excitation energy into light. The second organic compound comprises a benzofuropyrimidine scaffold or a benzothienopyrimidine scaffold. The third organic compound has a function for converting singlet excitation energy into light. Light emitted by the light-emitting layer includes light emitted by the third organic compound.

[0022] In the above structure, the first organic compound preferably has a function for supplying excitation energy to the third organic compound.

[0023] In a further embodiment of the present invention, the light-emitting device is described in claim 3. The light-emitting device comprises a light-emitting layer between a pair of electrodes. The light-emitting layer contains a first organic compound, a second organic compound, and a third organic compound. The first organic compound and the second organic compound can form an exciplex. The first organic compound has a function for converting triplet excitation energy into light. The second organic compound comprises a benzofuropyrimidine scaffold or a benzothienopyrimidine scaffold. The third organic compound has a function for converting singlet excitation energy into light. Light emitted by the light-emitting layer includes light emitted by the third organic compound.

[0024] In the above structure, the exciplex preferably has a function for supplying excitation energy to the third organic compound.

[0025] In one of the above structures, it is preferred that the benzofuropyrimidine framework is a benzofuro[3,2-d]pyrimidine framework or that the benzothienopyrimidine framework is a benzothieno[3,2-d]pyrimidine framework.

[0026] In the above structure, the benzofuro[3,2-d]pyrimidine skeleton or the benzothieno[3,2-d]pyrimidine skeleton preferably has a substituent at the 4-position or the 8-position.

[0027] In one of the above structures, the first organic compound contains Ru, Rh, Pd, Os, Ir or Pt.

[0028] In one of the above structures, the first organic compound preferably emits phosphorescence.

[0029] In one of the above structures, it is preferred that the emission spectrum of the exciplex partially overlaps with an absorption band on the longest wavelength side of an absorption spectrum of the third organic compound.

[0030] In one of the above structures, the first organic compound preferably exhibits an emission quantum yield of higher than or equal to 0% and lower than or equal to 40% at room temperature.

[0031] In one of the above structures, the exciplex preferably has a function for emitting light with a higher emission efficiency than that of the first organic compound.

[0032] In one of the above structures, the third organic compound preferably emits fluorescence.

[0033] In one of the above structures, the difference between the singlet excitation energy and the triplet excitation energy of the first organic compound is preferably greater than or equal to 0 eV and less than or equal to 0.2 eV.

[0034] In another embodiment of the present invention, a display device comprises the light-emitting element having one of the aforementioned structures and a color filter and / or a transistor. In another embodiment of the present invention, an electronic device comprises the display device and a housing and / or a touch sensor. In another embodiment of the present invention, a lighting device comprises the light-emitting element having one of the aforementioned structures and a housing and / or a touch sensor. The category of one 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 description therefore means an image display device or a light source (including a lighting device). The light-emitting device may, in its category, include 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; and a display module in which an integrated circuit (IC) is mounted directly onto a light-emitting element by a chip-on-glass (COG) process.

[0035] One embodiment of the present invention may provide a light-emitting element with high emission efficiency, a light-emitting element with low drive voltage, a very reliable light-emitting element, a light-emitting element with low power consumption, a novel light-emitting element, a novel light-emitting device or a novel electronic device.

[0036] It should be noted that the description of these effects does not preclude the existence of further effects. An embodiment of the present invention need not necessarily achieve all of these effects. Further effects will become apparent from the explanation of the description, the drawings, the claims, and the like, and can be derived from them. Brief description of the drawings

[0037] In the accompanying drawings: Fig. 1A and Fig.Figure 1B shows schematic cross-sectional views of a light-emitting element of an embodiment of the present invention, and Fig. Figure 1C shows the energy level correlation in a light-emitting layer; Fig. 2A and Fig. Figure 2B shows the energy level correlation in a light-emitting layer of a light-emitting element of an embodiment of the present invention; Fig. Figure 3 shows the energy level correlation in a light-emitting layer of a light-emitting element of an embodiment of the present invention; Fig. 4A and Fig. Figure 4B shows the energy level correlation in a light-emitting layer of a light-emitting element of an embodiment of the present invention; Fig. Figure 5 is a schematic cross-sectional view of a light-emitting element of an embodiment of the present invention; Fig.6A and Fig. Figure 6B are a top view and a schematic cross-sectional view representing a display device of an embodiment of the present invention; Fig. 7A and Fig. Figures 7B are schematic cross-sectional views, each representing a display device of an embodiment of the present invention; Fig. 8A and Fig. Figure 8B are schematic cross-sectional views, each representing a display device of an embodiment of the present invention; Fig. 9A to Fig. 9D represent electronic devices of embodiments of the present invention; Fig. 10A to Fig. 10C represent electronic devices of embodiments of the present invention; Fig. 11A and Fig. 11B represent an electronic device of an embodiment of the present invention; Fig.Figure 12 represents lighting devices of embodiments of the present invention; Fig. Figure 13 shows the power efficiency-luminance properties of light-emitting elements of an example; Fig. Figure 14 shows the current-voltage properties of light-emitting elements of an example; Fig. Figure 15 shows external quantum efficiency luminance properties of light-emitting elements of an example; Fig. Figure 16 shows emission spectra of light-emitting elements of an example; Fig. Figure 17 shows the power efficiency-luminance properties of light-emitting elements of an example; Fig. Figure 18 shows the current-voltage properties of light-emitting elements of an example; Fig. Figure 19 shows external quantum efficiency luminance properties of light-emitting elements of an example; Fig.Figure 20 shows emission spectra of light-emitting elements of an example; Fig. Figure 21 shows the results of a time-resolved emission measurement of an example; Fig. Figure 22 shows the relationship between an emission spectrum and an absorption spectrum of an example; Fig. Figure 23 shows the results of the reliability test of an example; Fig. Figure 24 shows the power efficiency-luminance properties of light-emitting elements of an example; Fig. Figure 25 shows the current-voltage properties of light-emitting elements of an example; Fig. Figure 26 shows external quantum efficiency luminance properties of light-emitting elements of an example; Fig. Figure 27 shows emission spectra of light-emitting elements of an example; and Fig.Figure 28 shows the relationship between an emission spectrum and an absorption spectrum of an example. Best way to implement the invention

[0038] Embodiments of the present invention are described in detail below with reference to the drawings.

[0039] It should be noted that the position, size, area, or the like of each component shown in drawings and the like is, in some cases, not shown precisely for ease of understanding. The disclosed invention is therefore not necessarily limited to the position, size, area, or the like disclosed in the drawings and the like.

[0040] It should be noted that the ordinal numbers, such as first and second, are used in this description and the like for the sake of simplicity, and in some cases they do not indicate the sequence of steps or the order of layers. Therefore, for example, an adequate description may still be given if "first" is replaced by "second" or "third". Furthermore, the ordinal numbers used in this description and the like are not necessarily the same as those used to specify an embodiment of the present invention.

[0041] In the explanation of the structures of the invention in this description and the like, based on the drawings, in some cases identical components in different drawings are provided with the same reference numerals.

[0042] In this description and similar texts, the terms "film" and "layer" may be used interchangeably. For example, in some cases the term "conducting film" may be used instead of the term "conducting layer," and the term "insulating layer" may be used instead of the term "insulating film."

[0043] In this description and similar texts, a singlet excitation state (S*) denotes a singlet state with excitation energy . An S1 level denotes the lowest singlet excitation energy level, i.e., the excitation energy level of the lowest singlet excitation state (S1 state). A triplet excitation state (T*) denotes a triplet state with excitation energy . A T1 level denotes the lowest triplet excitation energy level, i.e., the excitation energy level of the lowest triplet excitation state (T1 state). It should be noted that in this description and similar texts, "singulet excitation state" and "singulet excitation energy level" sometimes refer to the S1 state and the S1 level, respectively. Furthermore, in some cases, “triplet excitation state” and “triplet excitation energy level” refer to the T1 state or the T1 level, respectively.

[0044] In this description and similar usage, a fluorescent compound refers to a compound that emits light in the visible spectrum when it relaxes from the singlet excitation state to the ground state. A phosphorescent compound refers to a compound that emits light in the visible spectrum at room temperature when it relaxes from the triplet excitation state to the ground state. That is, a phosphorescent compound refers to a compound that can convert triplet excitation energy into visible light.

[0045] It should be noted that in this description and similar texts, "room temperature" refers to a temperature in the range of 0 °C to 40 °C.

[0046] In this description and similar examples, a blue wavelength range lies in the range of 400 nm to less than 490 nm, and blue light exhibits at least one peak in its emission spectrum within this wavelength range. A green wavelength range lies in the range of 490 nm to less than 580 nm, and green light exhibits at least one peak in its emission spectrum within this wavelength range. A red wavelength range lies in the range of 580 nm to 680 nm, and red light exhibits at least one peak in its emission spectrum within this wavelength range. (Version 1)

[0047] In this embodiment, a light-emitting element of an embodiment of the present invention is described below by reference to Fig. 1A to Fig. 1C, Fig. 2A and Fig. 2B, Fig. 3 as well as Fig. 4A and Fig. 4B described. <Strukturbeispiel 1 des Licht emittierenden Elements>

[0048] First, the structure of the light-emitting element of an embodiment of the present invention will be described below with reference to Fig. 1A to Fig. 1C described.

[0049] Fig. Figure 1A is a schematic cross-sectional view of a light-emitting element 150 of an embodiment of the present invention.

[0050] The light-emitting element 150 comprises a pair of electrodes (an electrode 101 and an electrode 102) and an EL layer 100 between the pair of electrodes. The EL layer 100 comprises at least one light-emitting layer 130.

[0051] The EL layer 100, which is in Fig. Figure 1A shows that, in addition to the light-emitting layer, 130 functional layers are included, such as a hole injection layer 111, a hole transport layer 112, an electron transport layer 118 and an electron injection layer 119.

[0052] In this embodiment, electrodes 101 and 102 of the electrode pair are described as the anode and cathode, respectively; however, the structure of the light-emitting element 150 is not limited to this. That is, electrode 101 can be a cathode, electrode 102 can be an anode, and the arrangement order of the layers between the electrodes can be reversed. In other words, the hole injection layer 111, the hole transport layer 112, the light-emitting layer 130, the electron transport layer 118, and the electron injection layer 119 can be arranged in this order, starting from the anode side.

[0053] It should be noted that the structure of EL layer 100 is not limited to the structure described in Fig.Figure 1A is shown as long as it contains at least one layer each of the hole injection layer 111, hole transport layer 112, electron transport layer 118, and electron injection layer 119. Alternatively, the EL layer 100 can, for example, comprise a functional layer capable of lowering a hole or electron injection barrier, improving a hole or electron transport property, reducing a hole or electron transport property, or suppressing an electrode quenching effect. It should be noted that the functional layer can be a single layer or a multiple layer.

[0054] Next, the light-emitting layer 130 will be described.

[0055] In one embodiment of the present invention, the light-emitting element 150 is a fluorescent element containing a fluorescent compound in the light-emitting layer 130. A fluorescent element is very reliable and exhibits high color purity, as its emission spectrum tends to be sharper than that of a phosphorescent element. It should be noted that in an organic EL element, the generation ratio of singlet excitons to triplet excitons (hereinafter referred to as the exciton generation probability) is statistically 1:3. This means that in a fluorescent element emitting light using singlet excitons, typically only 25% of the generated excitons contribute to light emission.Therefore, it is important that triplet excitons contribute to light emission in order to achieve a higher efficiency of a fluorescent element.

[0056] In view of the foregoing, the inventors of the present invention have found that triplet excitons can efficiently contribute to fluorescence, i.e., that a very efficient fluorescent element can be obtained by using a light-emitting layer comprising an organic compound capable of converting triplet excitation energy into light, an organic compound comprising a benzofuropyrimidine scaffold or a benzothienopyrimidine scaffold, and an organic compound that emits fluorescence.

[0057] The benzofuropyrimidine framework is preferably a benzofuro[3,2-d]pyrimidine framework, and the benzothienopyrimidine framework is preferably a benzothieno[3,2-d]pyrimidine framework. Such a composition can improve the electron transport properties of the organic compound. Furthermore, such a composition reduces the lowest unoccupied molecular orbital (LUMO) level of the organic compound; therefore, the organic compound is more likely to accept electrons in the light-emitting layer, allowing the drive voltage of the light-emitting element to be reduced.

[0058] The benzofuro[3,2-d]pyrimidine framework or the benzothieno[3,2-d]pyrimidine framework preferably has a substituent at the 4-position and / or the 8-position. With such a structure, a light-emitting element with high emission efficiency and high reliability can be obtained.

[0059] The substituent at the 4-position and / or the 8-position preferably comprises a framework with a hole transport property, in particular e.g. a carbazole framework, a dibenzofuran framework or a dibenzothiophene framework.

[0060] An example of the aforementioned organic compound capable of converting triplet excitation energy into light is a compound capable of emitting phosphorescence (hereinafter also referred to as a phosphorescent compound). A phosphorescent compound in this description and the like is a compound that emits phosphorescence, but no fluorescence, at temperatures ranging from low temperatures (e.g., 77 K) to room temperature (i.e., from 77 K to 313 K). The phosphorescent compound preferably contains a heavy atom to efficiently convert triplet excitation energy into light. When the phosphorescent compound contains a heavy atom, a transition between a singlet ground state and a triplet excited state is permitted through a spin-orbit interaction (an interaction between the spin angular momentum and the orbital angular momentum of an electron).Consequently, the transition probability between the singlet ground state and the triplet excitation state of the phosphorescent compound is increased; therefore, the emission efficiency and absorption probability related to the transition can be enhanced. Furthermore, energy transfer from the triplet excitation energy level of the phosphorescent compound to the singlet excitation energy level of the fluorescent compound is also permitted via the Förster mechanism. To promote energy transfer, the phosphorescent compound preferably contains a metallic element with a strong spin-orbit interaction, particularly a transition metal element.It is particularly preferred that the phosphorescent compound contains a platinum group element (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) or platinum (Pt)), in particular iridium, in which case the probability of the direct transition between the singlet ground state and the triplet excitation state can be increased.

[0061] Another example of a material capable of converting triplet excitation energy into light is a thermally activated delayed fluorescent (TADF) material. It should be noted that the TADF material is one that exhibits a small difference between the S1 and T1 levels and can convert triplet excitation energy into singlet excitation energy through reverse intersystem crossing. Thus, using a small amount of thermal energy, the TADF material enables the upconversion of triplet excitation energy to singlet excitation energy (i.e., reverse intersystem crossing) and can efficiently generate a singlet excitation state. An exciplex, whose excitation state is formed by two types of substances, exhibits a very small difference between the S1 and T1 levels and serves as a TADF material capable of converting triplet excitation energy to singlet excitation energy.

[0062] Fig. Figure 1B is a schematic cross-sectional view showing an example of the light-emitting layer 130 in Fig. 1A represents the light-emitting layer 130, which is in Fig. Figure 1B shows a compound 131, a compound 132 and a compound 133. In one embodiment of the present invention, compound 131 can convert triplet excitation energy into light, compound 132 is an organic compound with a benzofuropyrimidine framework or a benzothienopyrimidine framework, and compound 133 is a guest material that emits fluorescence. <Strukturbeispiel 1 der Licht emittierenden Schicht>

[0063] Fig.Figure 1C shows an example of the energy level correlation in the light-emitting layer contained in the light-emitting element of an embodiment of the present invention. In this structural example, compound 131 is a phosphorescent compound.

[0064] In particular, it shows Fig. 1C the correlation of energy levels of compounds 131, 132 and 133 in the light-emitting layer 130. What terms and symbols in Fig. The 1C representations are as follows: Comp (131): the connection 131; Comp (132): the connection 132; Guest (133): the connection 133; T C1 : the T1 level of connection 131; S C2 : the S1 level of connection 132; T C2 : the T1 level of connection 132; S G : the S1 level of connection 133; and T G : the T1 level of connection 133.

[0065] In Fig. An excited state is formed when compound 131 or compound 132 accepts holes and electrons. Here, compound 131 is a phosphorescent compound, and therefore intersystem crossing between a singlet state and a triplet state is allowed. Thus, both the singlet excitation energy and the triplet excitation energy of compound 132 can be rapidly transferred to compound 131 (Route A1 in Fig. 1C). At this point, S C2 ≥ T C2 and T C2 ≥ T C1Preferably, the light-emitting layer 130 is formed with a mixture of compounds 131, 132, and 133; in the mixture, the proportion of compound 132 is preferably higher than that of compound 131, and in particular, the weight ratio of compound 131 to compound 132 is preferably in the range of 1:9 to 3:7. Such a composition enables the efficient excitation of compound 131. Furthermore, since compound 131 is a phosphorescent compound, the triplet excitation energy of compound 131 can be efficiently converted into the singlet excitation energy of compound 133 (Route A2 in Fig. 1C). Here, as in Fig. 1C shown, p C2 ≥ T C1 ≥ S G preferred, whereby in this case the singlet excitation energy is efficiently transferred to compound 133, which serves as the guest material. Furthermore, T C2 ≥ T C1 ≥ S Gpreferably, in which case the triplet excitation energy is efficiently converted into the singlet excitation energy and transferred to compound 133, which is the guest material.

[0066] The triplet excitation energy supplied by T C1 on T G The transfer will be deactivated (Route A3 in Fig. 1C). For this reason, the amount of energy transferred via route A3 is preferably small. To avoid energy transfer via route A3, the weight ratio of connection 133 to the total weight of connections 131 and 132 is preferably low, and in particular preferably in the range of 0.001 to 0.05, more preferably in the range of 0.001 to 0.01.

[0067] It should be noted that if the direct charge carrier recombination process is dominant in compound 133, a large number of triplet excitons are generated in compound 133, leading to reduced emission efficiency due to thermal deactivation. Therefore, the contribution of the energy transfer process via route A2 is preferably higher than that of the direct charge carrier recombination process in compound 133, in which case the probability of generating the triplet excitation state of compound 133 can be reduced and thermal deactivation can be minimized. To meet this condition, the weight ratio of compound 133 to the total weight of compounds 131 and 132 is preferably low, and in particular preferably in the range of 0.001 to 0.05, more preferably in the range of 0.001 to 0.01.

[0068] If the light-emitting layer 130 has the structure described above, light emitted by the fluorescent compound of the light-emitting layer 130 can be efficiently obtained.

[0069] Furthermore, T G preferably 2.0 eV or less, in which case a very reliable light-emitting element can be obtained.

[0070] With the above structure, a material with a high emission quantum yield does not need to be used for the phosphorescent compound; consequently, the material design is simplified, and the material can be selected from a wide range of possibilities. Specifically, the emission quantum yield of the compound can be in the range of 0% to 50%, 0% to 40%, 0% to 25%, 0% to 10%, or 0% to 1% at room temperature or normal temperature.

[0071] As described above, an organic compound with a benzofuro[3,2-d]pyrimidine skeleton or a benzothieno[3,2-d]pyrimidine skeleton exhibits a low LUMO level among organic compounds with a benzofuro[3,2-d]pyrimidine skeleton or a benzothienopyrimidine skeleton and is therefore suitable for compound 132 with an electron transport property. <Strukturbeispiel 2 der Licht emittierenden Schicht>

[0072] Fig. Figure 2B shows an example of the energy level correlation in the light-emitting layer 130 of the light-emitting element 150 of an embodiment of the present invention. In this structural example, compound 131 is a phosphorescent compound, and compound 131 and compound 132 form an exciplex.

[0073] As long as the combination of compound 131 and compound 132 can form an exciplex, it is acceptable; however, preferably one of them is a compound with hole transport properties and the other is a compound with electron transport properties. In this case, a donor-acceptor exciplex is readily formed; thus, an exciplex can be formed efficiently. If compounds 131 and 132 are a combination of a compound with hole transport properties and a compound with electron transport properties, the charge carrier balance can be easily controlled by adjusting the mixing ratio. In particular, the weight ratio of the compound with hole transport properties to the compound with electron transport properties is preferably within a range of 1:9 to 9:1.Since the charge carrier equilibrium can be easily controlled by the above composition, a charge carrier recombination range can also be easily controlled.

[0074] The formation of an exciplex can be detected, for example, by comparing the emission spectra of compound 131, compound 132, and a mixed film containing these compounds, and observing a phenomenon in which the emission spectrum of the mixed film shifts toward the longer wavelength side than that of any single compound (or exhibits a new peak on the long wavelength side). Alternatively, the formation of an exciplex can be detected by comparing the transient photoluminescence (PL) of compound 131, compound 132, and a mixed film containing these compounds, and observing a difference in the transient response (e.g., a phenomenon in which the lifetime of the transient PL of the mixed film exhibits longer-lived components or a larger proportion of retardation components than that of any single compound).

[0075] For the efficient formation of an exciplex, the following is preferably fulfilled when combining the materials: The highest occupied molecular orbital (HOMO) level of one of compounds 131 and 132 is higher than that of the other compound, and the LUMO level of one of the compounds is higher than that of the other compound. In particular, the energy difference between the HOMO levels of compound 131 and compound 132 is preferably greater than or equal to 0.1 eV, more preferably greater than or equal to 0.2 eV, and even more preferably greater than or equal to 0.3 eV. Furthermore, the energy difference between the LUMO levels of compound 131 and compound 132 is preferably greater than or equal to 0.1 eV, more preferably greater than or equal to 0.2 eV, and even more preferably greater than or equal to 0.3 eV.Such an energy level correlation is preferred because electrons and holes, which are charge carriers, injected by the pair of electrodes (electrodes 101 and 102) are readily injected into compound 131 and compound 132. It should be noted that the HOMO level of compound 131 may be equal to that of compound 132, or the LUMO level of compound 131 may be equal to that of compound 132.

[0076] It should be noted that the LUMO levels and the HOMO levels of the compounds can be obtained from the electrochemical properties (the reduction potentials and the oxidation potentials) of the compounds, which are measured by cyclic voltammetry (CV).

[0077] For example, if compound 131 has a hole transport property and compound 132 has an electron transport property, the HOMO level of compound 131 is preferably higher than that of compound 132, and the LUMO level of compound 131 is preferably higher than that of compound 132, as shown in an energy band diagram in Fig. 2A shown. Such an energy level correlation is preferred because electrons and holes, which are charge carriers injected by the pair of electrodes (electrodes 101 and 102), are readily injected into compound 131 and compound 132, respectively.

[0078] In Fig. 2A represents “Comp (131)” compound 131; “Comp (132)” compound 132; ΔE C1 , the energy difference between the LUMO level and the HOMO level of compound 131; ΔE C2 , the energy difference between the LUMO level and the HOMO level of compound 132; and ΔE E, the energy difference between the LUMO level of compound 132 and the HOMO level of compound 131.

[0079] The exciplex formed by compound 131 and compound 132 has the HOMO in compound 131 and the LUMO in compound 132. The excitation energy of the exciplex roughly corresponds to the energy difference (ΔE). E ) between the LUMO level of compound 132 and the HOMO level of compound 131, which is smaller than the energy difference (ΔE) C1 ) between the LUMO level and the HOMO level of compound 131, as well as the energy difference (ΔE) C2 ) between the LUMO level and the HOMO level of compound 132. Thus, if compound 131 and compound 132 form an exciplex, an excited state with a lower excitation energy can be formed. The exciplex can form a stable excited state because it has a lower excitation energy.

[0080] Fig. Figure 2B shows the correlation of energy levels of compounds 131, 132, and 133 in the light-emitting layer 130. Fig. 2B represents S C1 represents the S1 level of connection 131; S E , the S1 level of the exciplex; and T E , the T1 level of the exciplex. The other terms and symbols in Fig. 2B are the same as those who are in Fig. 1C will be shown.

[0081] In this structural example, compound 131 and compound 132, contained in the light-emitting layer 130, form the exciplex in the light-emitting element of an embodiment of the present invention. The S1 level (S E ) and the T1 level (T E ) of the Exciplex are located next to each other (see Route A4 in Fig. 2B).

[0082] If the exciplex formed by the above process loses excitation energy and is returned to a ground state, for example by light emission or by supplying excitation energy to another material, the two substances forming the exciplex behave individually as originally separate substances.

[0083] Since the excitation energy levels (S E and T E ) of the exciplex lower than the S1 levels (S C1 and S C2 Since the substances forming the exciplex (i.e., compounds 131 and 132) are low, an excitation state with a lower excitation energy can be formed. Accordingly, the drive voltage of the light-emitting element 150 can be reduced.

[0084] Since the S1 level and the T1 level (S E and T ESince the exciplex's energy levels are adjacent to each other, the exciplex has a function for emitting thermally activated delayed fluorescence. In other words, the exciplex has a function for converting triplet excitation energy to singlet excitation energy by upconversion. Thus, a portion of the triplet excitation energy generated in the light-emitting layer 130 is converted into singlet excitation energy by the exciplex. To bring about this conversion, the energy difference between the S1 level and the T1 level (S) E and T E ) of the exciplex 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 (T E ) of the exciplex preferably lower than the T1 levels (T C1 and T C2) of compounds 131 and 132, which form the exciplex, to efficiently bring about the reverse intersystem crossing. Accordingly, quenching of the triplet excitation energy of the exciplex formed by compound 131 and compound 132 does not occur as readily, leading to the efficient inducement of the reverse intersystem crossing from triplet excitation energy to singlet excitation energy by the exciplex.

[0085] The singlet excitation energy level (S E ) of the exciplex is preferably higher than the singlet excitation energy level (S G ) of compound 133, which serves as a light-emitting material. With such an energy level correlation, the singlet excitation energy of the formed exciplex can be determined from the singlet excitation energy level (S). E ) of the exciplex to the singlet excitation energy level (S G ) will be transmitted via connection 133.

[0086] Here, the energy level correlation between compound 131 and compound 132 does not correspond to the one in Fig. 2B shown is limited. In other words: The singlet excitation energy level (S C1 ) of compound 131 can be higher or lower than the singlet excitation energy level (S C2 ) of compound 132 and the triplet excitation energy level (T C1 ) of compound 131 can be higher or lower than the triplet excitation energy level (T C2 ) of connection 132.

[0087] In one embodiment of the present invention, a phosphorescent compound is used as one of the compounds forming the exciplex, which allows intersystem crossing between a singlet state and a triplet state. Thus, an exciplex can be formed in which the triplet excitation state can be converted to the singlet ground state. In this case, the triplet excitation energy level (T)E ) of the exciplex preferably higher than the singlet excitation energy level (S G ) of compound 133, which is a light-emitting material. With such an energy level correlation, the triplet excitation energy of the formed exciplex can be determined from the triplet excitation energy level (T). E ) of the exciplex to the singlet excitation energy level (S G ) of compound 133. It should be noted that it can be difficult to clearly distinguish fluorescence and phosphorescence from each other in an emission spectrum, since the S1 level and the T1 level (S E and T E ) of the exciplex lie next to each other. In this case, fluorescence and phosphorescence can sometimes be distinguished from each other by their emission lifetime.

[0088] Through the energy transfer process described above, junction 133 is brought into a singlet excitation state and can emit light (see Route A5 in Fig. 2B).

[0089] The triplet excitation energy supplied by T E on T G The transfer will be deactivated (Route A6 in Fig. 2B). For this reason, the amount of energy transferred via route A6 is preferably small. To avoid energy transfer via route A6, the weight ratio of connection 133 to the total weight of connections 131 and 132 is preferably low, and in particular preferably in the range of 0.001 to 0.05, more preferably in the range of 0.001 to 0.01.

[0090] It should be noted that if the direct charge carrier recombination process is dominant in compound 133, a large number of triplet excitons are generated in compound 133, leading to reduced emission efficiency due to thermal deactivation. Therefore, the contribution of energy transfer via the exciplex formation process (route A5 in) is preferable. Fig. 2B) higher than that of the direct charge carrier recombination process in compound 133, in which case the probability of generating the triplet excitation state of compound 133 can be reduced and the thermal deactivation can be reduced. To meet this condition, the weight ratio of compound 133 to the total weight of compounds 131 and 132 is preferably low, and in particular preferably in the range of 0.001 to 0.05, more preferably in the range of 0.001 to 0.01.

[0091] Furthermore, T Gpreferably 2.0 eV or less, in which case a very reliable light-emitting element can be obtained.

[0092] Alternatively, compound 131 can exhibit electron transport properties and compound 132 can exhibit hole transport properties. In this case, the HOMO level of compound 132 is preferably higher than that of compound 131, and the LUMO level of compound 132 is preferably higher than that of compound 131.

[0093] The weight ratio of compound 131 to compound 132 is preferably low. In particular, the weight ratio of compound 131 to compound 132 is preferably in the range of 0.01 to 0.5, more preferably in the range of 0.05 to 0.3.

[0094] If all energy transfer processes via route A4 and route A5 occur efficiently in the manner described above, both the singlet excitation energy and the triplet excitation energy generated in the light-emitting layer 130 will be efficiently converted into the singlet excitation energy of the compound 133, enabling the light-emitting element 150 to emit light with high emission efficiency.

[0095] In the light-emitting element of an embodiment of the present invention, the benzofuropyrimidine framework contained in compound 132 is preferably a benzofuro[3,2-d]pyrimidine framework, and the benzothienopyrimidine framework contained in compound 132 is preferably a benzothieno[3,2-d]pyrimidine framework. Such a composition reduces the LUMO level of compound 132, which is suitable for the formation of an exciplex.

[0096] The benzofuro[3,2-d]pyrimidine skeleton or the benzothieno[3,2-d]pyrimidine skeleton preferably has a substituent at the 4-position and / or the 8-position. Such a composition reduces the LUMO level of compound 132, which is suitable for the formation of an exciplex.

[0097] The process described above via route A4 and route A5 can be referred to in this description and the like as exciplex singlet energy transfer (ExSET) or exciplex-enhanced fluorescence (ExEF). In other words, in the light-emitting layer 130, excitation energy is supplied to the fluorescent compound by the exciplex.

[0098] If the light-emitting layer 130 has the structure described above, light emitted by the fluorescent compound can be obtained efficiently. <Strukturbeispiel 3 der Licht emittierenden Schicht>

[0099] Fig. Figure 3 shows an example of the energy level correlation in the light-emitting layer contained in the light-emitting element of an embodiment of the present invention. In this structural example, compound 131 is a thermally activated, delayed-release fluorescent material. It should be noted that S C1 represents the S1 level of connection 131, and the other terms and symbols in Fig. 3 are the same as those who are in Fig. 1C will be shown.

[0100] In Fig. 3. An excited state is formed when junction 131 or junction 132 accepts holes and electrons. The excitation energy of junction 132 can be rapidly transferred to junction 131 (route A7). At this time, S C2 ≥ S C1 and T C2 ≥ T C1Preferably, the light-emitting layer 130 is formed with a mixture of compounds 131, 132, and 133; in the mixture, the proportion of compound 132 is preferably higher than that of compound 131, and in particular, the weight ratio of compound 131 to compound 132 is preferably in the range of 1:9 to 3:7. Such a composition enables the efficient excitation of compound 131. Since compound 131 is a thermally activated, delayed-fluorescence material, the triplet excitation energy of compound 131 is converted upwards to the singlet excitation energy at approximately room temperature (Route A8). Furthermore, since energy transfer from the singlet excitation energy level (S1) is possible, C1 ) of compound 131 to the singlet excitation energy level (S G) of compound 133 (i.e. route A9) is allowed to raise the triplet excitation energy of compound 131 to the singlet excitation energy level (S) via the processes via route A8 and route A9. G ) of connection 133. Here, as in Fig. 3 shown, T C2 ≥ T C1 ≥ S G preferably, wherein in this case both the singlet excitation energy and the triplet excitation energy are efficiently transferred from compound 131 and compound 132 to compound 133, which is the guest material.

[0101] To efficiently drive the upconversion described above, the energy difference between the S1 level (S C1 ) and the T1 level (T C1 ) of the thermally activated, delayed fluorescent material 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.

[0102] The triplet excitation energy supplied by T C2 on T G The transmission will be deactivated (Route A) 10 in Fig. 3) For this reason, the amount of energy that is transported via Route A 10 is transmitted, preferably small. To facilitate energy transmission via Route A 10 To avoid the energy difference between T C1 and T G preferably large; thus T G preferably 2.0 eV or less. With such a structure, a very reliable light-emitting element with high emission efficiency can be obtained.

[0103] If the light-emitting layer 130 has the structure described above, light emitted by the fluorescent compound of the light-emitting layer 130 can be efficiently obtained. <Strukturbeispiel 4 der Licht emittierenden Schicht>

[0104] Fig.Figure 4A shows the light-emitting layer 130, which contains four types of materials. Fig. 4A contains the light-emitting layer 130, compound 131, compound 132, compound 133, and compound 134. In one embodiment of the present invention, compound 131 can convert triplet excitation energy into light, compound 132 is an organic compound with a benzofuropyrimidine framework or a benzothienopyrimidine framework, compound 133 is a guest material that emits fluorescence, and compound 134 is an organic compound that forms an exciplex together with compound 132.

[0105] Fig. Figure 4B shows the correlation of energy levels of compounds 131, 132, 133 and 134 in the light-emitting layer 130. Fig. 4B place S C3 and T C3 This represents the S1 level and the T1 level of connection 134. The other terms and symbols in Fig.4B are the same as those who are in Fig. 2B will be shown.

[0106] In this structural example, compound 132 and compound 134, contained in the light-emitting layer 130, form the exciplex in the light-emitting element of an embodiment of the present invention. The S1 level (S E ) and the T1 level (T E The exciplexes are located next to each other (see Route A). 11 in Fig. 4B).

[0107] As described above, when the exciplex formed by the aforementioned process loses excitation energy, the two substances forming the exciplex behave individually as originally separate substances.

[0108] Since the excitation energy levels (S E and T E ) of the exciplex lower than the S1 levels (S C2 and S C3Since the substances forming the exciplex (i.e., compounds 132 and 134) are low, an excitation state with a lower excitation energy can be formed. Accordingly, the drive voltage of the light-emitting element 150 can be reduced.

[0109] Here, compound 131 is a phosphorescent compound, and therefore intersystem crossing between a singlet state and a triplet state is permitted. Thus, both the singlet excitation energy and the triplet excitation energy of the exciplex are rapidly transferred to compound 131 (Route A). 12 ). At this point, T E ≥ T C1 preferred. Furthermore, the triplet excitation energy of compound 131 can be efficiently converted into the singlet excitation energy of compound 133 (Route A). 13 ). Here T E ≥ T C1 ≥ S G , as in Fig.4B shown, preferably, wherein in this case the excitation energy of compound 131 is efficiently transferred as singlet excitation energy to compound 133, which is the guest material.

[0110] Any combination of compound 132 and compound 134 capable of forming an exciplex is acceptable; however, preferably one of them is a compound with hole transport properties and the other is a compound with electron transport properties. In this case, a donor-acceptor exciplex is readily formed; thus, an exciplex can be efficiently formed. If compounds 132 and 134 are a combination of a compound with hole transport properties and a compound with electron transport properties, the charge carrier balance can be easily controlled by adjusting the mixing ratio. In particular, the weight ratio of the compound with hole transport properties to the compound with electron transport properties is preferably within a range of 1:9 to 9:1.Since the charge carrier equilibrium can be easily controlled by the above composition, a charge carrier recombination range can also be easily controlled.

[0111] For the efficient formation of an exciplex, the following is preferably fulfilled when combining the materials: The HOMO level of one of the compounds 132 and 134 is higher than that of the other compound, and the LUMO level of one of the compounds is higher than that of the other compound. In particular, the energy difference between the HOMO levels of compound 132 and compound 134 is preferably greater than or equal to 0.1 eV, more preferably greater than or equal to 0.2 eV, and even more preferably greater than or equal to 0.3 eV. Furthermore, the energy difference between the LUMO levels of compound 132 and compound 134 is preferably greater than or equal to 0.1 eV, more preferably greater than or equal to 0.2 eV, and even more preferably greater than or equal to 0.3 eV.Such an energy level correlation is preferred because electrons and holes, which are charge carriers, injected by the pair of electrodes (electrodes 101 and 102) are readily injected into compound 132 and compound 134. It should be noted that the HOMO level of compound 132 may be equal to that of compound 134, or the LUMO level of compound 132 may be equal to that of compound 134.

[0112] The energy level correlation between compound 132 and compound 134 is not applicable to the one in Fig. 4B shown is limited. In other words: The singlet excitation energy level (S C2 ) of compound 132 can be higher or lower than the singlet excitation energy level (S C3 ) of compound 134 and the triplet excitation energy level (T C1 ) of compound 131 can be higher or lower than the triplet excitation energy level (T C3 ) of connection 134.

[0113] In compound 132 of the light-emitting element of an embodiment of the present invention, the benzofuropyrimidine framework is preferably a benzofuro[3,2-d]pyrimidine framework, and the benzothienopyrimidine framework is preferably a benzothieno[3,2-d]pyrimidine framework. Such a composition reduces the LUMO level of compound 132, which is suitable for the formation of an exciplex.

[0114] The benzofuro[3,2-d]pyrimidine skeleton or the benzothieno[3,2-d]pyrimidine skeleton preferably has a substituent at the 4-position and / or the 8-position. Such a composition reduces the LUMO level of compound 132, which is suitable for the formation of an exciplex.

[0115] The triplet excitation energy supplied by T C1 on T G The transmission will be deactivated (Route A) 14 in Fig. 4B). For this reason, the amount of energy that travels via Route A 14is transmitted, preferably small. To facilitate energy transmission via Route A 14 To avoid this, the weight ratio of compound 133 to the total weight of compounds 131, 132 and 134 is preferably low, and in particular it is preferably in the range of 0.001 to 0.05, more preferably in the range of 0.001 to 0.01.

[0116] Furthermore, T G preferably 2.0 eV or less, in which case a very reliable light-emitting element can be obtained. <Energieübertragungsmechanismus>

[0117] This section describes factors that control the processes of intermolecular energy transfer. Two mechanisms have been proposed for intermolecular energy transfer: the Förster mechanism (dipole-dipole interaction) and the Dexter mechanism (electron exchange interaction). Here, an intermolecular energy transfer process between a first material in an excited state and a second material in a ground state is described; this energy transfer process can also apply to the case where one of the materials is an exciplex. <<Förster-Mechanismus> >

[0118] In the Förster mechanism, energy transfer does not require direct contact between molecules; instead, energy is transferred through the resonance of a dipole vibration between the first and second materials. Through this resonance, the first material transfers energy to the second, thus transforming the excited first material into a ground state and the ground second material into an excited state. The rate constant k h*→g The Förster mechanism is represented by Formula 1. kh*→g=9000c4K2ϕ ln 10128π5 n4 NτR6∫f'h(v)εg(v)v4dv

[0119] In Formula 1, v represents a frequency; f' h(v), a normalized emission spectrum of the first material (a fluorescence spectrum for discussion of energy transfer from a singlet excitation state, and a phosphorescence spectrum for discussion of energy transfer from a triplet excitation state); ε g (v), a molar absorption coefficient of the second material; N, Avogadro's number; n, a refractive index of a medium; R, an intermolecular distance between the first and second materials; τ, a measured lifetime of an excitation state (fluorescence lifetime or phosphorescence lifetime); c, the speed of light; ϕ, an emission quantum yield (a fluorescence quantum yield for discussing energy transfer from a singlet excitation state, and a phosphorescence quantum yield for discussing energy transfer from a triplet excitation state); and K 2, a coefficient (0 to 4) representing the orientation of a transition dipole moment of the first material and the second material. It should be noted that for random orientation K 2 2 / 3 is. < <dexter-mechanismus>>

[0120] In the Dexter mechanism, the first and second materials are located near a contact-effective region where their orbitals overlap, and energy is transferred by electron exchange between the first material in an excited state and the second material in a ground state. The rate constant k h*→g The Dexter mechanism is represented by Formula 2. kh*→g=(2πh)K2exp(−2RL)∫f'h(v)ε'g(v)dv

[0121] In formula 2, h represents the Planck constant; K, a constant with an energy dimension; v, a frequency; f' h (v), a normalized emission spectrum of the first material (a fluorescence spectrum for discussion of energy transfer from a singlet excitation state, and a phosphorescence spectrum for discussion of energy transfer from a triplet excitation state); ε' g (v) is a normalized absorption spectrum of the second material; L is an effective molecular radius; and R is an intermolecular distance between the first material and the second material.

[0122] Here, the energy transfer efficiency from the first material to the second material (energy transfer efficiency ϕ) is calculated. ET ) is represented by formula 3. In the formula, k represents r a rate constant of a light emission process (fluorescence for the discussion of energy transfer from a singlet excitation state, and phosphorescence for the discussion of energy transfer from a triplet excitation state) of the first material; k n , a rate constant of a process without light emission (thermal deactivation or intersystem crossing) of the first material; and τ, a measured lifetime of an excitation state of the first material. ϕET=kh*→gkr+kn+kh*→g=kh*→g(1τ)+kh*→g

[0123] Formula 3 shows that the energy transfer efficiency ϕ ET by increasing the velocity constant k h*→g during energy transfer, the other competing rate constant k r + k n (= 1 / τ) becomes relatively small. <<Konzept zur Förderung der Energieübertragung> >

[0124] First, energy transfer via the Förster mechanism is described. Substituting formula 1 into formula 3 allows for elimination. Thus, the energy transfer efficiency ϕ in the Förster mechanism depends on... ET does not depend on the lifetime τ of the excitation state of the first material. Furthermore, it can be stated that a higher energy transfer efficiency ϕ ET with the higher emission quantum yield ϕ (the fluorescence quantum yield for discussing the energy transfer from a singlet excitation state, and the phosphorescence quantum yield for discussing the energy transfer from a triplet excitation state).

[0125] Preferably, the emission spectrum (the fluorescence spectrum for discussing energy transfer from a singlet excitation state, and the phosphorescence spectrum for discussing energy transfer from a triplet excitation state) of the first material largely overlaps with the absorption spectrum (the absorption corresponding to the transition from the singlet ground state to the singlet excitation state) of the second material. Furthermore, the molar absorption coefficient of the second material is preferably high. This means that the emission spectrum of the first material overlaps with the absorption band on the longest wavelength side of the second material. Since the direct transition from the singlet ground state to the triplet excitation state is forbidden in the second material, the molar absorption coefficient of the second material in the triplet excitation state is negligible.Therefore, a process of energy transfer from the excitation state of the first material to the triplet excitation state of the second material can be ignored by the Förster mechanism, and only a process of energy transfer to the singlet excitation state of the second material is considered.

[0126] Next, the energy transfer via the Dexter mechanism is described. To determine the rate constant k h*→g To increase the energy transfer efficiency, according to Formula 2, the emission spectrum (the fluorescence spectrum for discussing energy transfer from a singlet excitation state, and the phosphorescence spectrum for discussing energy transfer from a triplet excitation state) of the first material preferably overlaps to a large extent with the absorption spectrum (absorption corresponding to the transition from a singlet ground state to a singlet excitation state) of the second material. Therefore, the energy transfer efficiency can be optimized by ensuring that the emission spectrum of the first material overlaps with the absorption band on the longest wavelength side of the second material.

[0127] When formula 2 is substituted into formula 3, it becomes apparent that the energy transfer efficiency ϕ ET in the Dexter mechanism of τ. In the Dexter mechanism, which is the energy transfer process based on electron exchange, an energy transfer occurs from the triplet excitation state of the first material to the triplet excitation state of the second material, as well as an energy transfer from the singlet excitation state of the first material to the singlet excitation state of the second material.

[0128] In a manner similar to that of energy transfer from the first material to the second material, energy transfer occurs through both the Förster mechanism and the Dexter mechanism in the energy transfer process from the exciplex to the fluorescent compound.

[0129] In the light-emitting element of an embodiment of the present invention, in which the second material is a fluorescent compound, the energy transfer efficiency to the triplet excitation state of the second material is preferably low. That is, the energy transfer efficiency based on the Dexter mechanism from the first material to the second material is preferably low, and the energy transfer efficiency based on the Förster mechanism from the first material to the second material is preferably high.

[0130] As described above, the energy transfer efficiency of the Förster mechanism does not depend on the lifetime τ of the excitation state of the first material. In contrast, the energy transfer efficiency of the Dexter mechanism does depend on the lifetime τ of the excitation state of the first material. To reduce the energy transfer efficiency of the Dexter mechanism, the lifetime τ of the excitation state of the first material is preferably small.

[0131] In light of the foregoing, in one embodiment of the present invention, an exciplex or a TADF material is used for the first material, and one of the compounds forming the exciplex can convert triplet excitation energy into light. With the structure of one embodiment of the present invention, reverse intersystem crossing from the triplet excitation state to the singlet excitation state of the exciplex (first material) can be promoted, and the lifetime τ of the triplet excitation state of the exciplex (first material) can be shortened. Furthermore, the transition from the triplet excitation state to the singlet ground state of the exciplex (first material) can be promoted, and the lifetime τ of the triplet excitation state of the exciplex (first material) can be shortened.As a result, the energy transfer efficiency in the Dexter mechanism can be reduced from the triplet excitation state of the exciplex (first material) to the triplet excitation state of the fluorescent compound (second material); therefore, a light-emitting element with high emission efficiency can be provided in one embodiment of the present invention.

[0132] Furthermore, the fluorescence lifetime of a thermally activated, delayed fluorescent component under light emitted by the exciplex is preferably short and is particularly preferably in the range of 10 ns to 50 µs, more preferably from 10 ns to 20 µs, and even more preferably from 10 ns to 10 µs.

[0133] The rate constant of the Förster mechanism is inversely proportional to the sixth power of the distance between the first and second materials, and the rate constant of the Dexter mechanism is inversely proportional to the exponential function of the distance between the first and second materials. Therefore, when the distance between the two molecules is approximately 1 nm or less, the Dexter mechanism is dominant, while the Förster mechanism is dominant when the distance is approximately 1 nm or more. To reduce the energy transfer efficiency of the Dexter mechanism, the distance between the first and second materials is preferably long, and more preferably 0.7 nm or more, more preferably 0.9 nm or more, and even more preferably 1 nm or more.To efficiently bring about energy transfer in the Förster mechanism, the distance between the first material and the second material is preferably 5 nm or less.

[0134] In light of the foregoing, in one embodiment of the present invention, compound 133, which is a fluorescent compound, preferably comprises at least two alkyl groups, each having two or more carbon atoms. Alternatively, compound 133 preferably comprises at least two branched alkyl groups, each having three to ten carbon atoms. As a further alternative, compound 133 preferably comprises at least two cyclic hydrocarbon groups, each having three to ten carbon atoms, or at least two bridged cyclic hydrocarbon groups, each having three to ten carbon atoms. Furthermore, compound 133 preferably comprises a condensed aromatic hydrocarbon having three to twelve carbon atoms. <materialien>

[0135] Next, the components of the light-emitting element of an embodiment of the present invention will be described in detail. <<Licht emittierende Schicht> >

[0136] The following describes materials that can be used for the light-emitting layer 130.

[0137] Compound 132 is an organic compound with a benzofuropyrimidine or benzothienopyrimidine framework. This organic compound exhibits advantageous electron transport properties and a high T1 level, and is therefore suitable as a host material for the light-emitting layer.

[0138] The benzofuropyrimidine framework or the benzothienopyrimidine framework is preferably a benzofuro[3,2-d]pyrimidine framework or a benzothieno[3,2-d]pyrimidine framework, and the benzofuro[3,2-d]pyrimidine framework or the benzothieno[3,2-d]pyrimidine framework preferably has a substituent at the 4-position and / or the 8-position. With such a composition, a light-emitting element with high emission efficiency and high reliability can be obtained.

[0139] An example of a compound with the benzofuropyrimidine framework or the benzothienopyrimidine framework is an organic compound with a naphthofuropyrimidinyl group or a naphthothienopyrimidinyl group. An organic compound with a naphthofuropyrimidinyl group or a naphthothienopyrimidinyl group is very reliable and is advantageously used for the light-emitting element of an embodiment of the present invention.

[0140] Examples of the benzofuropyrimidine framework and the benzothienopyrimidine framework are frameworks represented by the following general formulas (101) to (114). In general formulas (101) to (114), X represents an oxygen atom or a sulfur atom; Ht 1 and ht 2 each independently represents hydrogen or one of the following shown (Ht-1) to (Ht-13); and Ar 1 and Ar 2 Each of these compounds independently represents hydrogen or one of the following (Ar-1) to (Ar-27). It should be noted that an organic compound with a benzofuropyrimidine backbone or a benzothienopyrimidine backbone that may be used in an embodiment of the present invention is not limited to those described below by way of example.

[0141] A substituent bonded at the 4-position and / or the 8-position of the benzofuro[3,2-d]pyrimidine framework or the benzothieno[3,2-d]pyrimidine framework is preferably a substituent with a π-electron-rich heteroaromatic framework represented by Ht in the general formulas (101) to (114). The framework is preferably a furan, thiophene, or pyrrole framework, due to their high stability and reliability, and more preferably a carbazole, dibenzofuran, or dibenzothiophene framework. A highly reliable light-emitting element can be obtained with such a structure.

[0142] Examples of the π-electron-rich heteroaromatic framework include frameworks represented by the following general formulas (Ht-1) to (Ht-13). It should be noted that X in the general formulas (Ht-1) to (Ht-13) represents an oxygen atom or a sulfur atom.

[0143] The general formulas (101) to (114) and general formulas (Ht-1) to (Ht-13) shown above may contain a substituent. The substituent may be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 12 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. Specific examples of the cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the aryl group with 6 to 12 carbon atoms include a phenyl group, a naphthyl group, and a biphenyl group.The aforementioned substituents can be bonded to one another to form a ring. For example, in the case where a carbon atom at the 9 position in a fluorene framework has two phenyl groups as substituents, the phenyl groups are bonded to form a spirofluorene framework. It should be noted that an unsubstituted group is advantageous in that it can be easily synthesized and is an inexpensive starting material.

[0144] For example, the substituents that are known as Ar 1 and Ar 2 The groups designated in the general formulas (101) to (114) each independently represent hydrogen or a substituted or unsubstituted aryl group with 6 to 25 carbon atoms. Examples of the aryl group with 6 to 25 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a terphenyl group, and a fluorenyl group. Specific examples are groups represented by the following structural formulas (Ar-28) to (Ar-46). It should be noted that the substituents represented by Ar 1 and Ar 2 They are not limited to those described here as examples.

[0145] In the general formulas (Ht-2), (Ht-5), (Ht-8), and (Ht-11) through (Ht-13), Ar can represent a single-bonded arylene group or an arylene group with 6 to 25 carbon atoms. The arylene group may have 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 framework. Specific examples of the 6- to 25-carbon arylene group include a phenylene group, a naphthalenediyl group, a biphenylediyl group, and a fluorenediyl group. In the case where the arylene group has a substituent, the substituent can be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or an aryl group with 6 to 12 carbon atoms.Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and n-hexyl. Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Specific examples of aryl groups with 6 to 12 carbon atoms include phenyl, naphthyl, and biphenyl.

[0146] For example, any of the groups represented by the following structural formulas (Ar-1) to (Ar-27) can be used as the arylene group, denoted by Ar. It should be noted that the group that can be used as Ar is not limited to these.

[0147] In the general formulas (Ht-3), (Ht-6) and (Ht-9) R represents 1 Hydrogen, an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms. Specific examples of the alkyl group with 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and an n-hexyl group. Specific examples of the cycloalkyl group with 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the aryl group with 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and a fluorenyl group. The preceding aryl or phenyl group may have substituents, and the substituents may be bonded together to form a ring.A substituent can also be an alkyl group with 1 to 6 carbon atoms, a cycloalkyl group with 3 to 6 carbon atoms, or an aryl group with 6 to 12 carbon atoms. Specific examples of alkyl groups with 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and n-hexyl. Specific examples of cycloalkyl groups with 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Specific examples of aryl groups with 6 to 12 carbon atoms include phenyl, naphthyl, and biphenyl.

[0148] As an alkyl group or aryl group, which is represented by R 1 Any of the groups represented by the following structural formulas (R-1) to (R-32) can be used, for example. It should be noted that the group that can be used as an alkyl or aryl group is not limited to these.

[0149] As a substituent found in the general formulas (101) to (114), the general formulas (Ht-1) to (Ht-13), Ar and R 1 The group that can be used, for example, is the alkyl group or the aryl group represented by the structural formulas (R-1) to (R-32) above. It should be noted that the group that can be used as an alkyl or aryl group is not limited to these.

[0150] As described above, compound 131 preferably has a function for converting triplet excitation energy into light. Examples of organic compounds with this function include a phosphorescent material and a thermally activated, delayed-release fluorescent material.

[0151] Examples of the phosphorescent compound include an iridium-, rhodium-, or platinum-based organometallic complex and a metal complex, particularly a platinum complex and an organoiridium complex with a porphyrin ligand. In particular, an organoiridium complex, such as an iridium-based orthometallated complex, is preferred. Examples of ligands to be orthometallated include a 4H-triazole ligand, a 1H-triazole ligand, an imidazole ligand, a pyridine ligand, a pyrimidine ligand, a pyrazine ligand, and an isoquinoline ligand. Here, compound 131 (the phosphorescent compound) exhibits an absorption band corresponding to a triplet metal-to-ligand charge transfer (MLCT) transition.

[0152] Examples of substances exhibiting an emission peak in the blue or green wavelength range include organometallic iridium complexes with a 4H-triazole skeleton, such as Tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN 2 ]phenyl-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 skeleton, such as... B. Tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(Mptz1-mp)3) and Tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Prptz1-Me)3); organometallic iridium complexes with an imidazole skeleton, such 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: FIr6), 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(pi C )) and Bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2' ]Iridium(III)acetylacetonate (abbreviation: Flr(acac)). Among the materials mentioned above, the organometallic iridium complexes comprising a five-membered nitrogenous heterocyclic framework, such as a 4H-triazole framework, a 1H-triazole framework, or an imidazole framework, exhibit high triplet excitation energy, high reliability, and high emission efficiency and are therefore particularly preferred.

[0153] Examples of substances exhibiting an emission peak in the green or yellow wavelength range include organometallic iridium complexes with a pyrimidine framework, such as... B. Tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)3), Tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm)3), (Acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)2(acac)), (Acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm)2(acac)), (Acetylacetonato)bis[4-(2-norbornyl)-6-phenylpyrimidinato]iridium(III) (abbreviation: Ir(nbppm)2(acac)), (Acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (Abbreviation: Ir(mpmppm)2(acac)), (Acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN 3 ]phenyl-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 skeleton, such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-Me)2(acac)) and (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-iPr)2(acac)); organometallic iridium complexes with a pyridine skeleton, such as Tris(2-phenylpyridinato-N,C 2' )iridium(III) (abbreviation: Ir(ppy)3), Bis(2-phenylpyridinato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(ppy)2(acac)), Bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation: Ir(bzq)2(acac)), Tris(benzo[h]quinolinato)iridium(III) (abbreviation: Ir(bzq)3), Tris(2-phenylquinolinato-N,C 2' )iridium(III) (abbreviation: Ir(pq)3) and bis(2-phenylquinolinato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(pq)2(acac)); organometallic iridium complexes, such as bis(2,4-diphenyl-1,3-oxazolato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(dpo)2(acac)), Bis{2-[4'-(perfluorophenyl)phenyl]pyridinato-N,C 2' }iridium(III)acetylacetonate (abbreviation: Ir(p-PF-ph)2(acac)) and bis(2-phenylbenzothiazolato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(bt)2(acac)); and rare-earth metal complexes, such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: Tb(acac)3(Phen)). Among the materials mentioned above, the organometallic iridium complexes with a pyrimidine framework exhibit significantly high reliability and emission efficiency and are therefore particularly preferred.

[0154] Examples of substances exhibiting an emission peak in the yellow or red wavelength range include organometallic iridium complexes with a pyrimidine backbone, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: Ir(5mdppm)2(dibm)), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(5mdppm)2(dpm)) and bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(d1npm)2(dpm)); organometallic iridium complexes with a pyrazine backbone, such as... B. (Acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: Ir(tppr)2(acac)), Bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr)2(dpm)) and (Acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: Ir(Fdpq)2(acac)); organometallic iridium complexes with a pyridine skeleton, such as Tris(1-phenylisoquinolinato-N,C 2' )iridium(III) (abbreviation: Ir(piq)3) and bis(1-phenylisoquinolinato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(piq)2(acac)); platinum complexes, 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-propanediumoate)(monophenanthroline)europium(III) (abbreviation: Eu(DBM)3(Phen)) and tris[1-(2-thenoyl)-3,3,3-trifluoroacetonate](monophenanthroline)europium(III) (abbreviation: Eu(TTA)3(Phen)). Among the materials mentioned above, the organometallic iridium complexes with a pyrimidine framework exhibit significantly high reliability and emission efficiency and are therefore particularly preferred. Furthermore, the organometallic iridium complexes with a pyrazine framework can provide red light emission with advantageous chromaticity.

[0155] Another material that can be used for compound 131 is, as mentioned above, a thermally activated, delayed-release fluorescent material. In particular, any of the following materials can be used.

[0156] Firstly, a fullerene, a derivative thereof, or an acridine derivative, such as proflavin, eosin, and the like, can be mentioned. Further examples include a metal-containing porphyrin, such as one containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd). Examples of metal-containing porphyrin include a protoporphyrin tin fluoride complex (SnF2(Proto IX)), a mesoporphyrin tin fluoride complex (SnF2(Meso IX)), a hematoporphyrin tin fluoride complex (SnF2(Hämato IX)), a coproporphyrin tetramethyl ester tin fluoride complex (SnF2(Copro III-4Me)), an octaethylporphyrin tin fluoride complex (SnF2(OEP)), an etioporphyrin tin fluoride complex (SnF2(Etio I)) and an octaethylporphyrin platinum chloride complex (PtCl2(OEP)).

[0157] A heterocyclic compound comprising a π-electron-rich heteroaromatic ring and a π-electron-poor heteroaromatic ring can also be used as a thermally activated, delayed fluorescent material consisting of one type of material. Specific examples include 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-Phenoxazine-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-Phenyl-5,10-dihydrophenazine-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-Dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), Bis[4-(9,9-dimethyl-9,10-dihydroacridin)phenyl]sulfone (abbreviation: DMAC-DPS) and 10-Phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (abbreviation: ACRSA).Since the heterocyclic compound comprises the π-electron-rich heteroaromatic ring and the π-electron-poor heteroaromatic ring, it exhibits high electron transport and hole transport properties and is therefore preferred. Among frameworks with the π-electron-poor heteroaromatic ring, a diazine framework (a pyrimidine framework, a pyrazine framework, or a pyridazine framework) and a triazine framework are particularly preferred due to their high stability and reliability. Among frameworks with the π-electron-rich heteroaromatic ring, an acridine framework, a phenoxazine framework, a thiophene framework, a furan framework, and a pyrrole framework exhibit high stability and reliability; consequently, one or more of these frameworks is / are preferably included. An indole skeleton, a carbazole skeleton or a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton is particularly preferable as a pyrrole skeleton.It should be noted that a substance in which the π-electron-rich heteroaromatic ring is directly bonded to the π-electron-poor heteroaromatic ring is particularly preferred, since both the donor property of the π-electron-rich heteroaromatic ring and the acceptor property of the π-electron-poor heteroaromatic ring are high, and the difference between the energy level in the singlet excitation state and the energy level in the triplet excitation state becomes small.

[0158] Compound 133 in the light-emitting layer 130 is preferably a fluorescent compound. The fluorescent compound is, but is not limited to, preferably 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.

[0159] Specific 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-Bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-diphenyl-3,8-dicyclohexylpyrene-1,6-diamine (abbreviation: ch-1,6FLPAPrn), N,N'-Bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-Tetra(tert-butyl)perylene (abbreviation: TBP), 4-(10-Phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N''-(2-tert-Butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA), N,9-Diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-Diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N',N',N',N'',N'',N''',N'''-Octaphenyldibenzo[g,p]chrysen-2,7,10,15-tetraamine (abbreviation: DBC1), Coumarin 30, N-(9,10-Diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), N-[9,10-Bis(1,1'-Biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), N-(9,10-Diphenyl-2-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: 2DPAPPhA), 9,10-Bis(1,1'-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-Triphenylanthracene-9-amine (abbreviation: DPhAPhA), Coumarin 6, Coumarin 545T, N,N'-Diphenylquinacridone (abbreviation: DPQd), Rubrene, 2,8-Di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (abbreviation: TBRb), Nile Red, 5,12-Bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT) 2-(2-{2-[4-(Dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-Methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzene[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N',N'-Tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-Diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-Isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[lj]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanenitrile (abbreviation: DCJTB), 2-(2,6-Bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanenitrile (abbreviation: BisDCM), 2-{2,6-Bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzenol[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanenitrile (abbreviation: BisDCJTM) and 5,10,15,20-Tetraphenylbisbenzo[5,6]indeno[1,2,3-cd:1',2',3'-lm]perylene.,

[0160] In the case where compound 131 and compound 132 form an exciplex, compound 131, compound 132, and compound 133 are preferably selected such that the emission peak of the formed exciplex overlaps with an absorption band on the longest wavelength side (low energy side) of compound 133, which serves as the light-emitting material. This allows a light-emitting element with drastically improved emission efficiency to be provided.

[0161] It should be noted that the light-emitting layer 130 can have a structure in which two or more layers are arranged one above the other. In the case, for example, where the light-emitting layer 130 is formed by arranging a first light-emitting layer and a second light-emitting layer on top of each other in that order from the side of the hole transport layer, the first light-emitting layer is formed using a substance with a hole transport property as the host material, and the second light-emitting layer is formed using a substance with an electron transport property as the host material.

[0162] As in Fig. 4A and Fig. As shown in Figure 4B, the light-emitting layer 130 can contain an additional material (compound 134) besides compounds 131, 132, and 133. In this case, it is preferred that compound 132 and compound 134 form an exciplex. Here, one of the compounds 132 and 134 preferably has the highest HOMO level among the materials of the light-emitting layer 130, and the other of the compounds 132 and 134 preferably has the lowest LUMO level among the materials of the light-emitting layer 130. This means that the HOMO level of one of the compounds 132 and 134 is preferably higher than the HOMO level of compound 131 and that of the other of the compounds 132 and 134, and the LUMO level of the other of the compounds 132 and 134 is preferably lower than the LUMO level of compound 131 and that of one of the compounds 132 and 134.With such a structure, the reaction can be prevented in which compound 131 and compound 132 form an exciplex.

[0163] Compound 134 can, for example, be any of the following hole transport materials and electron transport materials. As already described, compound 132 has a low LUMO level and high electron transport properties because it has a benzofuropyrimidine or benzothienopyrimidine framework. Accordingly, compound 134 is preferably an organic compound with advantageous hole transport properties (a hole transport material) whose HOMO level is higher than that of compound 132.

[0164] A material that has the property of transporting more holes than electrons can be used as a hole transport material, with a material having a hole mobility of 1 × 10 -6 cm 2 A value of / Vs or higher is preferable. In particular, an aromatic amine, a carbazole derivative, or the like can be used. Furthermore, the hole transport material can be a high-molecular-weight compound.

[0165] Examples of aromatic amine compounds that can be used as materials with high hole transport properties include N,N'-Di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4'-Bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N,N'-Bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD) and 1,3,5-Tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B).

[0166] Specific examples of usable 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) and 3-[N-(1-Naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1).

[0167] Other examples of usable carbazole derivatives are 4,4'-Di(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3,5-Tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB) and 1,4-Bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene.

[0168] Other examples of materials with high hole transport properties are 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, and phenanthrene compounds, 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 described here are mainly substances with a hole mobility of 1 × 10⁻⁶. -6 cm 2 / Vs or higher. It should be noted that, apart from these substances, any substance can be used that has the property of transporting more holes than electrons. <<Paar von Elektroden> >

[0169] Electrode 101 and electrode 102 have functions for injecting holes and electrons into the light-emitting layer 130. Electrodes 101 and 102 can be formed using a metal, an alloy, a conductive compound, a mixture, or a layer arrangement of these or the like. A typical example of the metal is aluminum (Al); however, 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. A rare-earth metal, such as ytterbium (Yb), can be used as the transition metal. The alloy can be one containing any of the aforementioned metals and is, for example, MgAg or AlLi. Examples of the conductive compound include metal oxides, such as...Indium tin oxide (hereinafter referred to as ITO), silicon- or silicon-containing indium tin oxide (ITSO), indium zinc oxide, and tungsten- and zinc-containing indium oxide. The conductive compound can be an inorganic, carbon-based material, such as graphene. As described above, electrode 101 and / or electrode 102 can be formed by stacking at least two of these materials on top of each other.

[0170] Light emitted by the light-emitting layer 130 is extracted via electrode 101 and / or electrode 102; consequently, at least one of electrodes 101 and 102 transmits visible light. An example of a conductive material that transmits light is a conductive material whose transmittance for visible light is 40% to 100%, preferably 60% to 100%, and whose resistivity is 1 × 10⁻⁶ -2 Ω·cm or lower. The electrode from which light is extracted can be designed using a conductive material with transmitting and reflecting properties. An example of such a conductive material is one whose reflectance for visible light is 20% to 80%, preferably 40% to 70%, and whose resistivity is 1 × 10 -2 Ω·cm or lower. If the electrode from which light is extracted is formed using a material with low light transmittance, such as a metal or alloy, electrode 101 and / or electrode 102 will be formed in a thickness thin enough to allow visible light to pass through (e.g., in a thickness of 1 nm to 10 nm).

[0171] It should be noted that in this description and the like, the electrode used is a material that transmits visible light and is conductive. For example, in addition to a layer of an oxide conductor typed by the aforementioned ITO, an oxide semiconductor layer or an organic conductive layer containing an organic substance may be used. 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 are mixed, and a layer containing a composite material in which an organic compound and an electron acceptor are mixed. The resistivity of the translucent conductive layer is preferably less than or equal to 1 × 10⁻⁶. 5 Ω·cm, preferably lower than or equal to 1 × 10 4 Ω·cm.

[0172] Depending on requirements, a sputtering process, an evaporation process, a printing process, a coating process, a molecular beam epitaxy (MBE) process, a chemical vapor deposition (CVD) process, a pulsed laser deposition process, an atomic layer deposition (ALD) process or the like can be used as a method for forming the electrode 101 and the electrode 102. < <lochinjektionsschicht>>

[0173] The hole injection layer 111 has a function to promote hole injection by reducing the barrier to hole injection from one electrode of the electrode pair (electrode 101 or electrode 102) and is formed, for example, using a transition metal oxide, a phthalocyanine derivative, or an aromatic amine. Examples of transition metal oxides include molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide. Examples of phthalocyanine derivatives include phthalocyanine and a metal phthalocyanine. Examples of aromatic amines include a benzidine derivative and a phenylenediamine derivative. It is also possible to use a high-molecular-weight compound, such as polythiophene or polyaniline; a typical example is poly(ethylenedioxythiophene) / poly(styrenesulfonic acid), which is a self-doped polythiophene.

[0174] A hole injection layer 111 can also be a layer containing a composite material of a hole transport material and a material exhibiting electron-accepting properties from the hole transport material. Alternatively, a layer arrangement consisting of a layer containing a material with electron-accepting properties and a layer containing a hole transport material can be used. In a stable state or in the presence of an electric field, electrical charges can be transferred between these materials. Examples of materials exhibiting electron-accepting properties include organic acceptors such as a quinodimethane derivative, a chloranil derivative, and a hexaazatriphenylene derivative. Specific examples are compounds with an electron-withdrawing group (a halogen group or a cyano group), such as...7,7,8,8-Tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, and 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN) can be used. Alternatively, a transition metal oxide, such as an oxide of a metal from Groups 4 to 8, can be used. Specific examples include vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide. Molybdenum oxide is particularly preferred because it is stable in air, has low hygroscopic properties, and is easy to handle.

[0175] A material that has the property of transporting more holes than electrons can be used as a hole transport material, with a material having a hole mobility of 1 × 10 -6 cm 2 / Vs or higher is preferable. In particular, an aromatic amine or a carbazole derivative, which is shown as an example as a hole transport material that can be used in the light-emitting layer 130, as well as an aromatic hydrocarbon or a stilbene derivative, can be used. Alternatively, the hole transport material can be a high-molecular-weight compound.

[0176] 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'-bianthryl, anthracene, tetracene, rubrene, perylene and 2,5,8,11-Tetra(tert-butyl)perylene. Other examples are pentacene and coronene.The aromatic hydrocarbon, which has a hole mobility of 1 × 10. -6 cm 2 A material with a density of / Vs or higher and having 14 to 42 carbon atoms is particularly preferred.

[0177] The aromatic hydrocarbon may contain a vinyl skeleton. Examples of aromatic hydrocarbons with a vinyl group include 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi) and 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA).

[0178] It is also possible to use a high molecular weight compound, such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-fN'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA) or poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: poly-TPD). < <lochtransportschicht>>

[0179] 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 for the material of the hole injection layer 111. For the hole transport layer 112 to function as a transporter of holes injected into the hole injection layer 111 to the light-emitting layer 130, the HOMO level of the hole transport layer 112 is preferably equal to or close to that of the hole injection layer 111.

[0180] Any of the materials given as examples for the material of the hole injection layer 111 can be used as the hole transport material. Preferably, a substance with a hole mobility of 1 × 10⁻⁶ is used. -6 cm 2 / Vs or higher is used as a hole transport material. It should be noted that, apart from these substances, any substance exhibiting the property of transporting more holes than electrons can be used. The layer containing a substance with high hole transport properties is not limited to a single layer and can be a layered arrangement of two or more layers, each containing any of the aforementioned substances. < <elektronentransportschicht>>

[0181] The electron transport layer 118 has the function of transporting electrons injected from the other electrode of the electrode pair (electrode 101 or electrode 102) via the electron injection layer 119 to the light-emitting layer 130. A material capable of transporting more electrons than holes can be used as the electron transport material, with a material having an electron mobility of 1 × 10 -6 cm 2 A material with electron transport properties of Vs or higher is preferable. A π-electron-deficient heteroaromatic compound, such as a nitrogen-containing heteroaromatic compound, a metal complex, or the like, can be used as a readily accepting electron material (a material with electron transport properties). In particular, an organic compound with a benzofuropyrimidine or benzothienopyrimidine framework is preferably used. Other specific examples include metal complexes with a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand. Further examples include an oxadiazole derivative, a triazole derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, and a pyrimidine derivative. It should be noted that, apart from these substances, any substance that has the property of transporting more electrons than holes can be used for the electron transport layer.The electron transport layer 118 is not limited to a single layer and can be a layer arrangement of two or more layers, each containing any of the substances mentioned above.

[0182] Specific examples of the electron transport material include metal complexes with a quinoline or benzoquinoline framework, such as tris(8-quinolinolato)aluminium(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminium(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminium(III) (abbreviation: BAlq), and bis(8-quinolinolato)zinc(II) (abbreviation: Znq). Further examples include metal complexes with an oxazole-based or thiazole-based ligand, such as... B. Bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO) and Bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ). Besides such metal complexes, any of the following materials can be used: heterocyclic compounds, such as...2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-Bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-Phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 3-(4-Biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 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 backbone, such as2-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(Dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-Carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4-(3,6-Diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II) 6-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 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-Tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB); and heteroaromatic compounds, such as 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs). Alternatively, a high-molecular-weight compound, such as... Examples include poly(2,5-pyridindiyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), or poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)] (abbreviation: PF-BPy). The substances described here are mainly substances with an electron mobility of 1 × 10⁻⁶. -6 cm 2 / Vs or higher. It should be noted that any other substance can be used as long as it has the property of transporting more electrons than holes. Furthermore, an organic compound with a benzofuropyrimidine or benzothienopyrimidine framework is preferably used.

[0183] A layer controlling electron carrier transfer can be provided between the electron transport layer 118 and the light-emitting layer 130. This layer is formed by adding a small amount of a substance with high electron capture properties to the aforementioned material with high electron transport properties. By preventing electron carrier transfer, this layer can adjust the charge carrier balance. Such a structure is very effective in preventing problems that arise when electrons pass through the light-emitting layer (such as a reduction in the element's lifetime). < <elektroneninjektionsschicht>>

[0184] The electron injection layer 119 has a function for promoting electron injection by reducing a barrier to electron injection from the electrode 102 and can be formed, for example, using a Group 1 metal or a Group 2 metal, or an oxide, halide, or carbonate of one of these metals. Alternatively, a composite material can be used that includes the aforementioned electron transport material and a material that has the property of donating electrons to the electron transport material. Examples of the material that has the property of donating electrons include a Group 1 metal, a Group 2 metal, and an oxide of one of these metals. In particular, an alkali metal, an alkaline earth metal, or a compound thereof, such as lithium fluoride (LiF), sodium fluoride (NaF), cesium fluoride (CsF), calcium fluoride (CaF₂), or lithium oxide (LiO₂), can be used. x ). 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. An example of the electride comprises a substance in which electrons are added to calcium oxide-aluminum oxide at a high concentration. The electron injection layer 119 can be formed using any of the substances that can be used for the electron transport layer 118.

[0185] A composite material in which an organic compound and an electron donor (donor) are mixed can also be used for the electron injection layer 119. Such a composite material exhibits high electron injection and electron transport properties, since electrons in the organic compound are generated by the electron donor. In this case, the organic compound is preferably a material that can transport the generated electrons excellently. In particular, for example, any of the substances listed above (e.g., the metal complexes and heteroaromatic compounds) can be used to form the electron transport layer 118. The electron donor can be any substance that has the property of donating electrons to the organic compound. In particular, an alkali metal, an alkaline earth metal, or a rare earth metal, such as, for example,Lithium, cesium, magnesium, calcium, erbium, or ytterbium can be used. It is also preferable to use an alkali metal oxide or an alkaline earth metal oxide, such as lithium oxide, calcium oxide, or barium oxide. Alternatively, a Lewis base, such as magnesium oxide, can be used. Another alternative is an organic compound, such as tetrathiafulvalene (abbreviation: TTF).

[0186] It should be noted that the light-emitting layer, the hole injection layer, the hole transport layer, the electron transport layer, and the electron injection layer described above can each be formed by an evaporation process (including a vacuum evaporation process), an inkjet process, a coating process, a nozzle printing process, a gravure printing process, or the like. In addition to the materials mentioned above, an inorganic compound, such as a quantum dot, or a high-molecular-weight compound (e.g., an oligomer, a dendrimer, 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.

[0187] The quantum dot can be, for example, a gelatinous quantum dot, an alloyed quantum dot, a core-shell quantum dot, or a core-quantum quantum dot. A quantum dot containing elements from groups 2 and 16, elements from groups 13 and 15, elements from groups 13 and 17, elements from groups 11 and 17, or elements from groups 14 and 15 can be used. Alternatively, a 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.

[0188] Examples of liquid media used for the wet process include organic solvents 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); and dimethyl sulfoxide (DMSO).

[0189] Examples of high-molecular-weight compounds that can be used for the light-emitting layer include a polyphenylenevinylene (PPV) derivative, such as poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (abbreviation: MEH-PPV) and poly(2,5-dioctyl-1,4-phenylenevinylene); a polyfluorene derivative, such as... 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]thiadiazol-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)] and 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); and a polyphenylene derivative. Any of these high-molecular-weight compounds or a single high-molecular-weight compound, such as...PVK, poly(2-vinylnaphthalene), or poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (abbreviation: PTAA) can be doped with a light-emitting compound and used for the light-emitting layer. Any of the aforementioned compounds with light-emitting properties can be used as the light-emitting compound.

[0190] In one embodiment of the present invention, the light-emitting layer 130 is formed using a combination of three organic compounds: an organic compound with a benzofuropyrimidine framework or a benzothienopyrimidine framework, an organic compound capable of converting triplet excitation energy into light, and an organic compound emitting fluorescence. Alternatively, a high-molecular-weight compound having the aforementioned framework or function may also be used. For example, the light-emitting layer 130 may be formed using a high-molecular-weight compound having a benzofuropyrimidine framework or a benzothienopyrimidine framework, a substituent capable of converting triplet excitation energy into light, and a substituent emitting fluorescence.Alternatively, the light-emitting layer 130 can be formed using a mixture of a high-molecular-weight compound having a benzofuropyrimidine framework or a benzothienopyrimidine framework and a substituent capable of converting triplet excitation energy into light, and a low-molecular-weight compound that emits fluorescence. The use of such a high-molecular-weight compound allows for increased material utilization efficiency and a reduction in manufacturing costs. < <substrat>>

[0191] The light-emitting element of an embodiment of the present invention is formed on a substrate made of glass, plastic, or the like. As one possibility for arranging layers on top of each other on the substrate, the layers can be arranged sequentially from the side of electrode 101 or from the side of electrode 102.

[0192] For the substrate on which the light-emitting element of an embodiment of the present invention can be formed, glass, quartz, or plastic, for example, 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 deposited by evaporation, or the like can be used. Another material can be used as long as the substrate serves as a support in a manufacturing process for the light-emitting elements or has a function for protecting the light-emitting elements.

[0193] For example, in this description and similar examples, a light-emitting element can be formed using various substrates. There is no particular restriction regarding the type of substrate. Examples of substrates include a semiconductor substrate (e.g., a single-crystal substrate and 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, a mounting film, a cellulose nanofiber (CNF), paper containing a fiber material, and a base material film. For the glass substrate, for example, barium borosilicate glass, aluminum borosilicate glass, or soda-lime glass can be used.Examples of materials for the flexible substrate, mounting film, base material film, and the like include plastics typical of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). Other examples include resins such as acrylic, polypropylene, polyester, polyvinyl fluoride, and polyvinyl chloride. Further examples include polyamide, polyimide, aramid, epoxy, an evaporation-deposited inorganic film, and paper.

[0194] Alternatively, a flexible substrate can be used, allowing the light-emitting element to be deposited directly onto the substrate. A separating layer can be placed between the substrate and the light-emitting element. This separating layer can be used to separate part or all of the light-emitting element formed above the separating layer from the substrate and transfer the separated component to another substrate. In such a case, the light-emitting element can be transferred to a substrate with low heat resistance or to a flexible substrate. The separating layer can be, for example, a layer arrangement comprising inorganic films, namely a tungsten film and a silicon oxide film, or a resin film of polyimide or the like, formed above the substrate.

[0195] In other words, once a light-emitting element has been formed using a substrate, the light-emitting element can be transferred to another substrate. Examples of substrates onto which the light-emitting element is transferred include, in addition to the substrates mentioned above, a cellophane substrate, a rock 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), and the like), a leather substrate, and a rubber substrate. When such a substrate is used, a light-emitting element with high durability, high heat resistance, reduced weight, or reduced thickness can be formed.

[0196] A field-effect transistor (FET) can, for example, be formed over any of the aforementioned substrates, and the light-emitting element 150 can be formed over an electrode electrically connected to the FET. Accordingly, an active-matrix display device can be fabricated in which the FET controls the operation of the light-emitting element.

[0197] The structure described above for this embodiment can be used in a suitable combination with another embodiment. (Version 2)

[0198] In this embodiment, a light-emitting element with a structure that differs from that described in embodiment 1 is described below, based on Fig. 5 described. Fig. In some cases, section 5 will have a function similar to the one in Fig. 1A through the same hatching pattern as in Fig. Sections are shown in 1A and are not specifically marked with a reference symbol. Furthermore, the same reference symbols are used for sections with similar functions, and a detailed description of the sections is omitted in some cases. <Strukturbeispiel 2 eines Licht emittierenden Elements>

[0199] Fig. Figure 5 is a schematic cross-sectional view of a light-emitting element 250.

[0200] The light-emitting element 250, which is in Fig. Figure 5 shows a plurality of light-emitting units (one light-emitting unit 106 and one light-emitting unit 108) between a pair of electrodes (electrode 101 and electrode 102). One of the light-emitting units preferably has a structure similar to that of the one shown in Figure 5. Fig. The EL layer 100 shown in Figure 1A is similar. That is to say: It is preferred that the light-emitting element 150, which is in Fig. Figure 1A comprises a single light-emitting unit, while light-emitting element 250 comprises a plurality of light-emitting units. It should be noted that electrode 101 serves as the anode and electrode 102 as the cathode in the following description of light-emitting element 250; however, the functions of light-emitting element 250 can be interchanged.

[0201] In the light-emitting element 250, which is in Fig. As shown in Figure 5, the light-emitting unit 106 and the light-emitting unit 108 are arranged one above the other, and a charge-generating layer 115 is provided between the light-emitting unit 106 and the light-emitting unit 108. It should be noted that the light-emitting unit 106 and the light-emitting unit 108 can have the same structure or different structures. For example, the light-emitting unit 108 preferably uses a structure similar to that of the EL layer 100.

[0202] The light-emitting element 250 comprises a light-emitting layer 120 and a light-emitting layer 170. The light-emitting unit 106 comprises, in addition to the light-emitting layer 120, the hole injection layer 111, the hole transport layer 112, an electron transport layer 113, and an electron injection layer 114. The light-emitting unit 108 comprises, in addition to the light-emitting layer 170, a hole injection layer 116, a hole transport layer 117, the electron transport layer 118, and the electron injection layer 119.

[0203] In the light-emitting element 250, any layer in each of the light-emitting units 106 and 108 contains the organic compound of an embodiment of the present invention. It should be noted that the layer containing the organic compound is preferably the electron transport layer 113 or the electron transport layer 118, and more preferably the light-emitting layer 120 or the light-emitting layer 170.

[0204] The charge-generating layer 115 can either have a structure in which an acceptor substance (an electron acceptor) is added to a hole transport material, or a structure in which a donor substance (an electron donor) is added to an electron transport material. Alternatively, the charge-generating layer 115 can be a layer arrangement of both these structures.

[0205] If the charge-generating layer 115 contains a composite material of an organic compound and an acceptor substance, the composite material can be any composite material suitable for the hole injection layer 111 described in embodiment 1. The organic compound can be any of several compounds, such as an aromatic amine compound, a carbazole compound, an aromatic hydrocarbon, or a high-molecular-weight compound (e.g., an oligomer, a dendrimer, or a polymer). The organic compound preferably has a hole mobility of 1 × 10⁻⁶. -6 cm 2 / Vs or higher. It should be noted that any other substance can be used as long as it has the property of transporting more holes than electrons. Since the composite material of an organic compound and an acceptor substance has excellent charge carrier injection and charge carrier transport properties, operation at a low voltage or low current can be achieved. It should be noted that if a surface of a light-emitting unit on the anode side is in contact with the charge-generating layer 115, the charge-generating layer 115 can also serve as a hole injection layer or hole transport layer of the light-emitting unit; therefore, a hole injection layer or a hole transport layer need not necessarily be included in the light-emitting unit.Alternatively, if a surface of the light-emitting unit on the cathode side is in contact with the charge-generating layer 115, the charge-generating layer 115 can also serve as an electron injection layer or electron transport layer of the light-emitting unit; therefore, an electron injection layer or an electron transport layer need not necessarily be included in the light-emitting unit.

[0206] The charge-generating layer 115 can have a multilayer structure consisting of a layer containing the composite material of an organic compound and an acceptor substance, and a layer containing another material. For example, the charge-generating layer 115 can be formed by combining a layer containing the composite material of an organic compound and an acceptor substance with a layer containing a compound selected from substances with electron-donating properties and a compound with high electron transport properties. Alternatively, the charge-generating layer 115 can 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 film.

[0207] The charge-generating layer 115, provided between light-emitting unit 106 and light-emitting unit 108, is configured to inject electrons into one of the light-emitting units and to inject holes into the other light-emitting unit when a voltage is applied to electrode 101 and electrode 102. For example, injected into Fig. 5 the charge-generating layer 115 electrons into the light-emitting unit 106 and holes into the light-emitting unit 108 when a voltage is applied such that the potential of electrode 101 is higher than that of electrode 102.

[0208] It should be noted that, with regard to light extraction efficiency, the charge-generating layer 115 preferably has a transmittance for visible light (in particular, it has a transmittance for visible light of 40% or higher). The charge-generating layer 115 itself operates at a lower conductivity than the pair of electrodes (electrodes 101 and 102).

[0209] The charge-generating layer 115, which is formed using one of the aforementioned materials, can suppress an increase in the drive voltage caused by the layer arrangement of the light-emitting layers.

[0210] Although Fig. Figure 5 represents a light-emitting element comprising two light-emitting units. A similar structure can also be applied to a light-emitting element in which three or more light-emitting units are stacked vertically. If a multitude of light-emitting units, separated from the charge-generating layer, are arranged between a pair of electrodes, as in Light-Emitting Element 250, a light-emitting element can be provided that can emit light with high luminance while keeping the current density low and exhibiting a long lifetime. Furthermore, a low-power light-emitting element can be obtained.

[0211] It should be noted that in each of the above structures, the emission colors of the guest materials used in light-emitting unit 106 and light-emitting unit 108 can be the same or different. If guest materials emitting light of the same color are used for light-emitting unit 106 and light-emitting unit 108, light-emitting element 250 advantageously achieves a high luminance at a low current value. Conversely, if guest materials emitting light of different colors are used for light-emitting unit 106 and light-emitting unit 108, light-emitting element 250 advantageously exhibits multicolored light emission.In this case, when a variety of light-emitting materials with different emission wavelengths are used in one or both of the light-emitting layers 120 and 170, the light-emitting element 250 emits light obtained by synthesizing lights with different emission peaks. This means that the emission spectrum of the light-emitting element 250 has at least two local maximum values.

[0212] The above structure is also suitable for obtaining white light emission. White light emission can be obtained if the light-emitting layer 120 and the light-emitting layer 170 emit light of complementary colors. Preferably, the guest materials are selected such that white light emission with high color rendering properties or light emission of at least red, green, and blue can be obtained.

[0213] One or both of the light-emitting layers 120 and 170 preferably have the structure of the light-emitting layer 130 shown in embodiment 1, in which case a very reliable light-emitting element with high emission efficiency can be obtained. The guest material contained in the light-emitting layer 130 is a fluorescent material; thus, if the structure of the light-emitting layer 130 shown in embodiment 1 is used in one or both of the light-emitting layers 120 and 170, a light-emitting element with a sharp emission spectrum and high color purity can be obtained.

[0214] In the case of a light-emitting element in which three or more light-emitting units are stacked vertically, the colors of light emitted by the host materials within the units can be the same or different. If the light-emitting element comprises a multitude of units emitting light of the same color, these units can emit light of the color with higher luminance at a lower current value compared to the light of the other colors. Such a structure can be used to adjust emission colors. This structure is particularly well-suited when using host materials that emit light of different colors with varying emission efficiencies.For example, if the light-emitting element comprises three light-emitting units, the intensity of the fluorescence and phosphorescence can be adjusted by providing two light-emitting units containing a fluorescent material of the same color and one light-emitting unit containing a phosphorescent material that emits light in a color different from the emission color of the fluorescent material. Therefore, the intensity of the emitted light of each color can be adjusted by changing the number of light-emitting units.

[0215] If a light-emitting element comprises two light-emitting units for fluorescence and one light-emitting unit for phosphorescence in the manner described above, the preferred combinations of the light-emitting units are as follows: a combination of two light-emitting units containing a blue fluorescent material and one light-emitting unit containing a yellow phosphorescent material; a combination of two light-emitting units containing a blue fluorescent material and one light-emitting unit containing a red phosphorescent material and a green phosphorescent material; and a combination of two light-emitting units containing a blue fluorescent material and one light-emitting unit containing a red phosphorescent material, a yellow phosphorescent material, and a green phosphorescent material.Such combinations are preferable because they enable efficient white light emission.

[0216] At least one of the light-emitting layers 120 and 170 can be divided into layers, and the divided layers can each contain different light-emitting materials. That is, at least one of the light-emitting layers 120 and 170 can consist of two or more layers. For example, if the light-emitting layer is formed by stacking a first light-emitting layer and a second light-emitting layer on top of each other in that order, starting from the hole-transport layer side, the first light-emitting layer is formed using a material with hole-transport properties as its host material, and the second light-emitting layer is formed using a material with electron-transport properties as its host material.In this structure, a light-emitting material contained in the first light-emitting layer can be the same as or different from a light-emitting material contained in the second light-emitting layer, and the materials can have functions for emitting light of the same color or light of different colors. White light emission with high color rendering properties, formed from three primary colors or four or more colors, can be obtained by using a variety of light-emitting materials with functions for emitting light of different colors.

[0217] It should be noted that this embodiment can be appropriately combined with one of the other embodiments. (Version 3)

[0218] In this embodiment, a light-emitting device, which includes the light-emitting element described in embodiment 1 and embodiment 2, is used by means of Fig. 6A and Fig. 6B described.

[0219] Fig. Figure 6A is a top view of the light-emitting device. Fig. 6B is a cross-sectional view along lines AB and CD in Fig. 6A. The light-emitting device comprises a source driver section 601, a pixel section 602, and a gate driver section 603, which are indicated by dashed lines and control the light emission from light-emitting elements. A reference numeral 604 denotes a sealing substrate, a reference numeral 625 denotes a desiccant, and a reference numeral 605 denotes a sealant. A section enclosed by the sealant 605 is a space 607.

[0220] It should be noted that a connecting line 608 is a line for transmitting signals input to the source driver circuit 601 and the gate driver circuit 603, and for receiving a video signal, clock signal, start signal, reset signal, and the like from a flexible printed circuit (FPC) 609, which serves as an external input terminal. Although only the FPC is shown here, a printed wiring board (PWB) can be attached to the FPC. A light-emitting device in this description includes, in its category, not only a light-emitting device per se, but also a light-emitting device equipped with an FPC or a PWB.

[0221] Next, a cross-sectional structure of the light-emitting device will be shown based on Fig. 6B is described. The driver circuit sections and the pixel section are formed on an element substrate 610. Here, it is shown that Fig. 6B represents the source driver circuit 601, which is the driver circuit section, and a pixel of the pixel section 602.

[0222] In the source driver circuit 601, a CMOS circuit is formed, consisting of an n-channel TFT 623 and a p-channel TFT 624. The driver circuit can be formed using one of the various circuits, such as a CMOS circuit, a PMOS circuit, and an NMOS circuit. Although this embodiment shows a driver-integrated light-emitting device in which the driver circuit is formed above the substrate, the driver circuit does not necessarily have to be formed above the substrate and can be formed outside the substrate.

[0223] The pixel section 602 consists of pixels, each containing a switching TFT 611, a current-controlling TFT 612, and a first electrode 613 electrically connected to a drain of the current-controlling TFT 612. It should be noted that an insulator 614 is provided to cover an end section of the first electrode 613. The insulator 614 can be formed using a positive photosensitive resin film.

[0224] To improve the coverage with a film formed over the insulator 614, the insulator 614 is designed to have a curved surface with a curvature at its upper or lower end section. For example, if a photosensitive acrylic is used for the insulator 614, preferably only the upper end section of the insulator 614 has a curved surface. The radius of curvature of the curved surface is preferably greater than or equal to 0.2 µm and less than or equal to 0.3 µm. Either a negatively photosensitive or a positively photosensitive material can be used for the insulator 614.

[0225] An EL layer 616 and a second electrode 617 are formed over the first electrode 613. A material with a high work function is preferably used for the first electrode 613, which serves as the anode. For example, a single-layer film, such as an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing 2 wt% to 20 wt% zinc oxide, a titanium nitride film, a chromium film, a tungsten film, a zinc film, or a platinum film, a layered arrangement of a titanium nitride film and a film containing aluminum as the main component, or a layered arrangement of three layers, namely a titanium nitride film, a film containing aluminum as the main component, and a titanium nitride film, can be used. The first electrode 613 with a multilayer structure enables low conduction resistance and good ohmic contact, as well as functioning as an anode.

[0226] The EL layer 616 is formed by one of several processes, such as evaporation using an evaporation mask, inkjet printing, and rotational coating. The material incorporated into the EL layer 616 can be a low-molecular-weight compound or a high-molecular-weight compound (including oligomers and dendrimers).

[0227] The material used for the second electrode 617, which is formed above the EL layer 616 and serves as the cathode, is preferably a material with a low work function (e.g., Al, Mg, Li, Ca, or an alloy or compound thereof, such as MgAg, MgIn, or AlLi). In cases where light generated in the EL layer 616 passes through the second electrode 617, a layer arrangement consisting of a thin metal film and a transparent conductive film (e.g., ITO, indium oxide containing 2 wt.% to 20 wt.% zinc oxide, indium tin oxide containing silicon, or zinc oxide (ZnO)) is preferably used for the second electrode 617.

[0228] A light-emitting element 618 consists of the first electrode 613, the EL layer 616, and the second electrode 617. The light-emitting element 618 preferably has the structure described in embodiment 1 or embodiment 2. In the light-emitting device of this embodiment, the pixel section, which consists of a plurality of light-emitting elements, can include both the light-emitting element with the structure described in embodiment 1 or embodiment 2 and a light-emitting element with a different structure.

[0229] The sealing substrate 604 is attached to the element substrate 610 by means of the sealing agent 605, so that the light-emitting element 618 is provided in the space 607, which is surrounded by the element substrate 610, the sealing substrate 604, and the sealing agent 605. The space 607 is filled with a filler. The filler can be an inert gas (e.g., nitrogen or argon) or a resin and / or a desiccant.

[0230] An epoxy-based resin or a glass frit is preferably used for the sealant 605. It is preferred that such a material be as permeable to moisture or oxygen as possible. The sealant substrate 604 can be a glass substrate, a quartz substrate, or a plastic substrate made of fiber-reinforced plastic (FRP), polyvinyl fluoride (PVF), polyester, acrylic, or the like.

[0231] As described above, the light-emitting device which includes the light-emitting element described in embodiment 1 or embodiment 2 can be obtained. <Strukturbeispiel 1 einer Licht emittierenden Vorrichtung>

[0232] Fig. 7A and Fig. Figure 7B each represents an example of a light-emitting device comprising a light-emitting element having white light emission and a color layer (a color filter).

[0233] Fig. 7A comprises a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007 and 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral section 1042, a pixel section 1040, a driver circuit section 1041, first electrodes 1024W, 1024R, 1024G and 1024B of light-emitting elements, a partition 1026, an EL layer 1028, a second electrode 1029 of the light-emitting elements, a sealing substrate 1031, a sealant 1032, a red pixel 1044R, a green pixel 1044G, a blue pixel 1044B, a white pixel 1044W and the like.

[0234] In Fig. 7A 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. A black layer (black matrix) 1035 may also be provided. The transparent base material 1033, which is provided with the color layers and the black layer, is correctly aligned and attached to the substrate 1001. The color layers and the black layer are covered with a cover layer 1036. In Fig. 7A comprises light received from EL layer 1028, light that is not extracted through any color layers, and light that is extracted through the color layers. Since the light not passing through the color layers is white, and the light passing through one of the color layers is red, blue, or green, an image can be displayed using pixels of the four colors.

[0235] Fig. Figure 7B provides an example in which the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B are formed between the gate insulating film 1003 and the first intermediate insulating film 1020. As shown in Fig. As shown in Figure 7B, the color layers can be provided between the substrate 1001 and the sealing substrate 1031.

[0236] The light-emitting device described above has a structure in which light is extracted from the side of the substrate 1001 where the TFTs are formed (bottom-emission structure), but it can also have a structure in which light is extracted from the side of the sealing substrate 1031 (top-emission structure). <Strukturbeispiel 2 der Licht emittierenden Vorrichtung>

[0237] Fig. 8A and Fig. Figure 8B shows cross-sectional views of light-emitting top-emission devices. For a top-emission structure, an opaque substrate can be used as substrate 1001. The process up to the step of forming a connecting electrode that links the TFT and the anode of the light-emitting element is carried out in the same way as in the light-emitting bottom-emission device. Subsequently, a third interlayer insulating film 1037 is formed to cover an electrode 1022. This insulating film may have a flattening function. The third interlayer insulating film 1037 can be formed using a material that can be used for the second interlayer insulating film 1021 or one of other different materials.

[0238] The lower electrodes 1025W, 1025R, 1025G, and 1025B of the light-emitting elements serve as anodes here, but they can also serve as cathodes. In a top-emission light-emitting device, such as the one in Fig. 8A and Fig. In 8B, the lower electrodes 1025W, 1025R, 1025G, and 1025B are preferably reflective electrodes. It should be noted that the second electrode 1029 preferably has a function for reflecting light and a function for transmitting light. It is preferable that a microcavity structure is used between the second electrode 1029 and the lower electrodes 1025W, 1025R, 1025G, and 1025B, in which case light of a specific wavelength is amplified. The EL layer 1028 has a structure similar to that described in embodiment 1 or embodiment 2, so that white light emission can be obtained.

[0239] In Fig. 7A and Fig. 7B as well Fig. 8A and Fig. 8B The structure of the EL layer for providing white light emission can be achieved, for example, by using a multitude of light-emitting layers or a multitude of light-emitting units. It should be noted that the structure for providing white light emission is not limited to the above.

[0240] In the Fig. 8A and Fig. The top-emission structure shown in Figure 8B can be sealed 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 a black layer (black matrix) 1030 positioned between pixels. The color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) and the black layer (black matrix) 1030 can be covered with the cover layer. It should be noted that a translucent substrate is used as the sealing substrate 1031.

[0241] Fig. 8A represents a structure in which a full-color display is carried out using three colors, namely red, green, and blue; alternatively, a full-color display can be carried out using four colors, namely red, green, blue, and white, as shown in Fig. Figure 8B illustrates this. The structure for implementing a full-color display is not limited to the above. For example, a full-color display can be implemented using four colors: red, green, blue, and yellow.

[0242] In the light-emitting element of one embodiment of the present invention, a fluorescent material is used as the guest material. Since a fluorescent material has a sharper spectrum than a phosphorescent material, light emission with high color purity can be obtained. Accordingly, by using the light-emitting element, the light-emitting device shown in this embodiment can exhibit high color reproducibility.

[0243] In the above manner, the light-emitting device which includes the light-emitting element described in embodiment 1 or embodiment 2 can be obtained.

[0244] It should be noted that this embodiment can be appropriately combined with one of the other embodiments. (Version 4)

[0245] In this embodiment, electronic devices and display devices of embodiments of the present invention are described.

[0246] According to one embodiment of the present invention, an electronic device and a display device can be manufactured that have a flat surface, advantageous emission efficiency, and high reliability. According to another embodiment of the present invention, an electronic device and a display device can be manufactured that have a curved surface, advantageous emission efficiency, and high reliability. The light-emitting element of an embodiment of the present invention can emit light with high color purity. Accordingly, by using the light-emitting element in a light-emitting device as shown in this embodiment, an electronic device and a display device that exhibit high color reproducibility can be provided.

[0247] Examples of electronic devices include a television set, a desktop or notebook personal computer, a computer monitor or the like, a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable gaming console, a portable information terminal, an audio playback device, and a large gaming machine, such as a pinball machine.

[0248] A portable information terminal 900, which is in Fig. 9A and Fig. 9B, as shown, includes a housing 901, a housing 902, a display section 903, a hinge section 905 and the like.

[0249] Housing 901 and housing 902 are connected to each other by the hinge section 905. The portable information terminal 900 can, as shown in Fig. 9B shows a closed state ( Fig. 9A). Thus, the portable information terminal 900 offers high portability when worn and, thanks to its large display area, is highly visible when in use.

[0250] In the portable information terminal 900, the flexible display section 903 is provided across the housing 901 and the housing 902, which are connected to each other by the hinge section 905.

[0251] The light-emitting device, which is manufactured using an embodiment of the present invention, can be used for display section 903. Therefore, the portable information terminal can exhibit high reliability.

[0252] The display section 903 can show document data and / or a still image and / or a moving image and / or the like. When document data is displayed on the display section 903, the portable information terminal 900 can be used as an e-book reader.

[0253] When the portable information terminal 900 is opened, the display section 903 is distinctly curved. For example, the display section 903 is held while containing a curved section with a radius of curvature of 1 mm to 50 mm, preferably 5 mm to 30 mm. Part of the display section 903 can display an image in its curved state because pixels are arranged continuously from the housing 901 to the housing 902.

[0254] The display section 903 serves as a touchscreen and can be operated with a finger, a stylus or the like.

[0255] The display section 903 is preferably designed using a flexible display, in which case a continuous image can be displayed between the housing 901 and the housing 902. It should be noted that both the housing 901 and the housing 902 can be equipped with a display.

[0256] The hinge section 905 preferably includes a locking mechanism such that the angle formed between the housing 901 and the housing 902 does not exceed a predetermined angle when the portable information terminal 900 is open. For example, the angle at which the housing 901 and the housing 902 are locked (they are not opened further) is preferably greater than or equal to 90° and less than 180°, and may typically be 90°, 120°, 135°, 150°, 175°, or the like. Consequently, the practicality, safety, and reliability of the portable information terminal 900 can be improved.

[0257] If the joint section 905 includes a locking mechanism, no excessive force is exerted on the display section 903; thus, damage to the display section 903 can be prevented. Consequently, a highly reliable portable information terminal can be provided.

[0258] The 901 enclosure and the 902 enclosure may contain a power button, an operating button, an external connection port, a speaker, a microphone, or the like.

[0259] Either the 901 enclosure or the 902 enclosure is equipped with a wireless communication module, and data can be transmitted and received via a computer network, such as the Internet, a local area network (LAN) or Wi-Fi (registered trademark).

[0260] A portable information terminal 910, which is in Fig. The assembly shown in Figure 9C includes a housing 911, a display section 912, a control knob 913, an external connection port 914, a loudspeaker 915, a microphone 916, a camera 917 and the like.

[0261] The light-emitting device, which is manufactured using an embodiment of the present invention, can be used for the display section 912. This allows the portable information terminal to be manufactured with high efficiency.

[0262] The portable information terminal 910 includes a touch sensor in the display section 912. Operations, such as making calls and entering text, can be performed by touching the display section 912 with a finger, a stylus or the like.

[0263] The power can be switched on / off using control knob 913. It can also be used to switch between the types of images displayed on display section 912; for example, switching between images on a screen for writing an email and a main menu screen is done using control knob 913.

[0264] If a detection device, such as a gyroscope sensor or an accelerometer, is provided within the portable information terminal 910, the direction of the display on the screen of the display section 912 can be changed automatically by determining the orientation of the portable information terminal 910 (whether the portable information terminal 910 is oriented horizontally or vertically). Furthermore, the direction of the display on the screen can be changed, for example, by touching the display section 912, by operating the control knob 913, or by sound input via the microphone 916.

[0265] The Portable Information Terminal 910 serves, for example, as one or more devices combining a telephone, a notebook, and an information retrieval system. In particular, the Portable Information Terminal 910 can be used as a smartphone. The Portable Information Terminal 910 can run various applications, such as making mobile phone calls, sending and receiving emails, viewing and editing text, playing music, playing video, using the internet, and running computer games.

[0266] A 920 camera, which is in Fig. The camera 920, as shown in Figure 9D, includes a housing 921, a display section 922, control buttons 923, a release button 924, and the like. Furthermore, an attachable lens 926 is mounted on the camera 920.

[0267] The light-emitting device, which is manufactured using an embodiment of the present invention, can be used for display section 922. Therefore, the camera can be very reliable.

[0268] Although the lens 926 of the camera 920 is removable from the housing 921 for replacement, the lens 926 can be integrated into the housing 921.

[0269] Still or moving images can be taken with the camera 920 when the shutter release button 924 is pressed. Images can also be taken by touching the display section 922, which has a touchscreen function.

[0270] It should be noted that a stroboscope, a viewfinder or the like may be additionally attached to the camera 920 or alternatively integrated into the housing 921.

[0271] Fig. 10A is a schematic view that represents an example of a cleaning robot.

[0272] A 5100 cleaning robot includes a display 5101 on its top, multiple cameras 5102 on its side, a brush 5103, and control buttons 5104. Although not shown, the underside of the 5100 cleaning robot is equipped with a wheel, an inlet, and similar features. The 5100 cleaning robot also includes various sensors, such as an infrared sensor, an ultrasonic sensor, an accelerometer, a piezoelectric sensor, an optical sensor, and a gyroscope. The 5100 cleaning robot includes a wireless communication device.

[0273] The cleaning robot 5100 is self-driving, captures dust 5120 and vacuums up the dust through the inlet opening provided on the underside.

[0274] The 5100 cleaning robot can assess whether an obstacle, such as a wall, piece of furniture, or step, is present by analyzing images captured by the 5102 cameras. If the 5100 cleaning robot detects an object that could become entangled in the 5103 brush (e.g., a wire) by analyzing an image, the rotation of the 5103 brush can be stopped.

[0275] The 5101 display can show the remaining battery capacity, the amount of dust collected, and similar information. The 5101 display can also show the route the 5100 cleaning robot has traveled. The 5101 display may be a touchscreen, and the 5104 control buttons may be integrated into the 5101 display.

[0276] The 5100 cleaning robot can communicate with a portable electronic device 5140, such as a smartphone. The portable electronic device 5140 can display images captured by the 5102 cameras. Therefore, the owner of the 5100 cleaning robot can monitor their room even when they are not at home. The owner can also check the display on the 5101 screen via the portable electronic device 5140, such as a smartphone.

[0277] The light-emitting device of an embodiment of the present invention can be used for the display 5101.

[0278] A robot 2100, which is in Fig. Figure 10B includes an arithmetic device 2110, a light sensor 2101, a microphone 2102, an upper camera 2103, a speaker 2104, a display 2105, a lower camera 2106, an obstacle sensor 2107 and a movement mechanism 2108.

[0279] The microphone 2102 has a function to capture a user's voice, ambient noise, and the like. The speaker 2104 also has a function to output sound. The robot 2100 can communicate with a user using the microphone 2102 and the speaker 2104.

[0280] The Display 2105 has a function to display various types of information. The Robot 2100 can display user-requested information on the Display 2105. The Display 2105 can be equipped with a touchscreen. Furthermore, the Display 2105 can be a detachable information terminal, in which case charging and data communication can occur when the Display 2105 is positioned at the predetermined location of the Robot 2100.

[0281] The upper camera 2103 and the lower camera 2106 each have a function for capturing an image of the robot 2100's surroundings. The obstacle sensor 2107 can detect an obstacle in the direction in which the robot 2100 is moving forward using the movement mechanism 2108. The robot 2100 can move safely by perceiving its surroundings with the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107.

[0282] The light-emitting device of an embodiment of the present invention can be used for the display 2105.

[0283] Fig. Figure 10C provides an example of a spectacle-like display. The spectacle-like display includes, for example, a housing 5000, a display section 5001, a loudspeaker 5003, an LED lamp 5004, control buttons 5005 (including a power switch and an operating switch), a connection port 5006, a sensor 5007 (a sensor with a function for measuring force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, electrical energy, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays), a microphone 5008, a second display section 5002, a carrier 5012, and an earphone 5013.

[0284] The light-emitting device of an embodiment of the present invention can be used for the display section 5001 and the second display section 5002.

[0285] Fig. 11A and Fig. 11B represents a foldable, portable information terminal 5150. The foldable, portable information terminal 5150 includes a housing 5151, a display area 5152, and a curved section 5153. Fig. Figure 11A represents the portable information terminal 5150, which is unfolded. Fig. Figure 11B depicts the 5150 portable information terminal in its folded state. Despite its large display area 5152, the 5150 portable information terminal is compact and highly portable when folded.

[0286] The display area 5152 can be folded twice using the bending section 5153. The bending section 5153 includes a flexible element and a plurality of support elements. When the display area is folded, the flexible element expands, and the bending section 5153 has a radius of curvature of 2 mm or more, preferably 5 mm or more.

[0287] It should be noted that the display area 5152 can be a touchscreen (an input / output device) that includes a touch sensor (an input device). The light-emitting device of an embodiment of the present invention can be used for the display area 5152.

[0288] This embodiment can be appropriately combined with one of the other embodiments. (Version 5)

[0289] In this embodiment, an example in which the light-emitting element of an embodiment of the present invention is used for various lighting devices is illustrated by means of Fig. 12 described. Using the light-emitting element of an embodiment of the present invention, a very reliable lighting device with advantageous emission efficiency can be produced.

[0290] By forming the light-emitting element of an embodiment of the present invention over a flexible substrate, an electronic device and a lighting device having a light-emitting area with a curved surface can be obtained.

[0291] The light-emitting device, which includes the light-emitting element of an embodiment of the present invention, can also be used for lighting vehicles, in particular, for example, lighting for a windshield and a vehicle roof.

[0292] Fig. Figure 12 presents an example in which the light-emitting element is used for an interior lighting device 8501. Since the light-emitting element can have a larger area, a large-area lighting device can also be designed. Furthermore, a lighting device 8502, whose light-emitting area has a curved surface, can also be designed using a housing with a curved surface. The light-emitting element described in this embodiment has the form of a thin film, which allows for a more flexible design of the housing. Accordingly, the lighting device can be artistically designed in various ways. In addition, a wall of the room can be provided with a large lighting device 8503.Touch sensors can be arranged in the lighting devices 8501, 8502 and 8503 to control the turning on or off of the lighting devices.

[0293] If the light-emitting element is provided on the top of a table, a lighting device 8504, which has a function as a table, can be obtained. It should be noted that if the light-emitting element is used as part of another piece of furniture, a lighting device, which has a function as that piece of furniture, can be obtained.

[0294] As described above, lighting devices and electronic equipment can be obtained using the light-emitting element of an embodiment of the present invention. It should be noted that the light-emitting element can be used for lighting devices and electronic equipment in various fields, not limited to those described in this embodiment.

[0295] The structures described in this embodiment can be appropriately combined with any of the structures described in the other embodiments. [Example 1]

[0296] This example shows fabrication methods for the light-emitting element of an embodiment of the present invention. The structure of each light-emitting element fabricated in this example is the same as that described in Fig. Figure 1A is shown. Table 1 shows the details of the element structures. The structure and abbreviation of compounds used in this example are shown below. [Table 1] layer Reference sign Thickness (nm) material weight ratio Light-emitting element 1 electrode 102 200 Al - Electron injection layer 119 1 LiF - electron transport layer 118(2) 10 NB Phen - 118(1) 15 4mCzBPBfpm - light-emitting layer 130 30 4mCzBPBfpm:Ir(Mptz1-MP)3:1.6tBuFrBAPrn 0,8:0,2:0,01 Hole transport layer 112 20 mCzFLP - Hole injection layer 111 30 DBT3P-II:MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting element 2 electrode 102 200 Al - Electron injection layer 119 1 LiF - electron transport layer 118(2) 10 NB Phen - 118(1) 15 4mCzBPBfpm - light-emitting layer 130 30 4mCzBPBfpm:Ir(Mptz1-mp)3:coumarin 521T 0,8:0,2:0,005 Hole transport layer 112 20 mCzFLP - Hole injection layer 111 30 DBT3P-II:MoO3 1:0,5 electrode 101 70 ITSO - <Herstellung der Licht emittierenden Elemente>

[0297] Methods for manufacturing the light-emitting elements of this example are described below. <<Herstellung des Licht emittierenden Elements 1> >

[0298] Electrode 101 was formed from an ITSO film with a thickness of 70 nm on a glass substrate. It should be noted that the area of ​​electrode 101 was 4 mm². 2 (2 mm × 2 mm) was set.

[0299] Next, DBT3P-II and molybdenum oxide (MoO3) were deposited as a hole injection layer 111 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 in a thickness of 30 nm over the electrode 101.

[0300] The hole transport layer 112 was then 9-[3-(9-Phenyl-9H-fluoren-9-yl)phenyl]-9H-carbazole (abbreviation: mCzFLP) deposited by evaporation in a thickness of 20 nm over the hole injection layer 111.

[0301] Next, the light-emitting layer consisted of 130 4-{3-[3'-(9H-Carbazol-9-yl)]biphenyl-3-yl}benzofuro[3,2-d]pyrimidine (abbreviation: 4mCzBPBfpm), Tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(Mptz1-mp)3) and N,N'-Bis(4-tert-butylphenyl)-N,N'-bis[4-(dibenzofuran-2-yl)phenyl]pyren-1,6-diamine (abbreviation: 1,6tBuFrBAPrn) by co-evaporation in a weight ratio of 4mCzBPBfpm:Ir(Mptz1-mp)3:1,6tBuFrBAPrn = 0.8:0.2:0.01 is deposited in a thickness of 30 nm above the hole transport layer 112. In the light-emitting layer 130, 1.6tBuFrBAPrn is a fluorescent compound and Ir(Mptz1-mp)3 is a phosphorescent compound.

[0302] As an electron transport layer 118, 4mCzBPBfpm and NBPhen were successively deposited by evaporation to a thickness of 15 nm and 10 nm, respectively, over the light-emitting layer 130. Subsequently, as an electron injection layer 119, LiF was deposited by evaporation to a thickness of 1 nm over the electron transport layer 118.

[0303] Next, aluminum (Al) was formed as electrode 102 with a thickness of 200 nm above the electron injection layer 119.

[0304] Then, in a glovebox containing a nitrogen atmosphere, a glass substrate was fixed to the glass substrate on which the organic materials were deposited, using a sealant for an organic EL device, thereby sealing the light-emitting element 1. Specifically, after the sealant had been applied to enclose the organic materials deposited on the glass substrate and the glass substrate had been fixed to the glass substrate for sealing, the device was irradiated with UV light at a wavelength of 365 nm and an intensities of 6 J / cm². 2 and a heat treatment at 80 °C for one hour was carried out. The light-emitting element 1 was obtained through the preceding steps. <<Herstellung des Licht emittierenden Elements 2> >

[0305] Light-emitting element 2 was produced by the same steps as light-emitting element 1, except for the step to form light-emitting layer 130.

[0306] As light-emitting layer 130 of light-emitting element 2, 4mCzBPBfpm, Ir(Mptz1-mp)3, and 10-acetyl-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-[1]benzopyrano[6,7,8-ij]quinolizin-11-one (abbreviation: Coumarin 521T) were deposited by co-evaporation in a weight ratio of 4mCzBPBfpm:Ir(Mptz1-mp)3:Cumarin 521T = 0.8:0.2:0.005 to a thickness of 30 nm. In light-emitting layer 130, Coumarin 521T is a fluorescent compound, serving as the third organic compound, and Ir(Mptz1-mp)3 is a phosphorescent compound. <Eigenschaften der Licht emittierenden Elemente>

[0307] Subsequently, the properties of the fabricated light-emitting elements 1 and 2 were measured. The luminance and CIE chromaticity were measured using a luminance colorimeter (BM-5A, manufactured by Topcon Technohouse Corporation), and the electroluminescence spectra were measured using a multichannel spectrometer (PMA-11, manufactured by Hamamatsu Photonics KK).

[0308] Fig. 13, Fig. 14 and Fig. Figure 15 shows the luminance-current efficiency properties, the voltage-current properties, and the luminance-external quantum efficiency properties of the light-emitting elements 1 and 2. Fig. Figure 16 shows the electroluminescence spectra obtained when a current with a current density of 2.5 mA / cm² is applied. 2 The values ​​obtained for light-emitting elements 1 and 2 were obtained. It should be noted that the measurement of the light-emitting elements was carried out at room temperature (in an atmosphere maintained at 23 °C).

[0309] Table 2 shows the element properties of light-emitting elements 1 and 2 at approximately 1000 cd / m². 2 . [Table 2] Voltage (V) Current density (mA / cm³) 2 ) CIE chromaticity(x, y) Luminance (cd / m²) 2 ) Power efficiency (cd / A) Energy efficiency (lm / W) external quantum efficiency (%) Light-emitting element 1 3,70 5,31 (0,174, 0,424) 1100 20,8 17,7 8,93 Light-emitting element 2 3,80 6,98 (0,157, 0,363) 1100 15,9 13,1 7,62

[0310] Out of Fig. Figure 16 shows that light-emitting element 1 and light-emitting element 2 exhibit emission spectra with peak wavelengths of 487 nm and 480 nm, respectively, and blue light emission originating from fluorescent compounds 1,6tBuFrBAPrn and coumarin 521T. Furthermore, light-emitting elements 1 and 2, each representing an embodiment of the present invention, exhibit a narrow half-width of electroluminescence spectrum and emit light with high color purity, thus making them suitable for display devices.

[0311] As in Fig. 13, Fig. As shown in Figure 15 and Table 2, the light-emitting elements 1 and 2 exhibit high emission efficiency (current efficiency, power efficiency, and external quantum efficiency). Since the maximum probability of generating singlet excitons due to recombination of charge carriers (holes and electrons) injected from a pair of electrodes is 25%, the maximum external quantum efficiency, assuming an outcoupling efficiency of 25%, is 6.25%. Furthermore, the external quantum efficiency of each of the light-emitting elements 1 and 2 is higher than 6.25%. This is because, in light-emitting elements 1 and 2 of an embodiment of the present invention, not only singlet excitons but also triplet excitons can contribute to fluorescence via Ir(Mptz1-mp)3, which is the phosphorescent compound.

[0312] Furthermore, the efficiency drop (also known as roll-off) on the high-luminance side in the light-emitting elements 1 and 2 is small. Such a small roll-off is one of the features of the light-emitting element in an embodiment of the present invention.

[0313] An organic compound with a benzofuropyrimidine skeleton, such as 4mCzBPBfpm, which serves as the host material for light-emitting elements 1 and 2, exhibits high S1 and T1 levels. This allows for the creation of a highly efficient light-emitting element that emits blue fluorescence, similar to light-emitting elements 1 and 2. [Example 2]

[0314] This example shows fabrication examples of the light-emitting element of an embodiment of the present invention and light-emitting comparison elements. The structure of each light-emitting element fabricated in this example is the same as that described in Fig. Figure 1A is shown. Table 3 shows the details of the element structures. The structure and abbreviations of compounds used in this example are shown below. Note that for the structures and abbreviations of the other compounds, reference can be made to Example 1. [Table 3] layer Reference sign Thickness (nm) material weight ratio Light-emitting element 3 electrode 102 200 Al - Electron injection layer 119 1 LiF - electron transport layer 118(2) 20 NB Phen - 118(1) 15 4mCzBPBfpm - light-emitting layer 130 30 4mCzBPBfpm:Ir(ppz)3:coumarin 545T 0,8:0,2:0,005 Hole transport layer 112 20 mCzFLP - Hole injection layer 111 40 DBT3P-II: MoO3 1:0,5 electrode 101 70 ITSO - light-emitting reference element 4 electrode 102 200 Al - Electron injection layer 119 1 LiF - electron transport layer 118(2) 20 NB Phen - 118(1) 15 4mCzBPBfpm - light-emitting layer 130 30 4mCzBPBfpm:Ir(ppz)3 0,8:0,2 Hole transport layer 112 20 mCzFLP - Hole injection layer 111 40 DBT3P-II:MoO3 1:0,5 electrode 101 70 ITSO - light-emitting reference element 5 electrode 102 200 Al - Electron injection layer 119 1 LiF - electron transport layer 118(2) 20 BPhen - 118(1) 15 4.6mCzP2Pm - light-emitting layer 130 30 4.6mCzP2Pm:Ir(ppz) 3: Cumarin 545T 0,8:0,2:0,005 Hole transport layer 112 20 mCzFLP - Hole injection layer 111 40 DBT3P-II:MoO3 1:0,5 electrode 101 70 ITSO - <Herstellung der Licht emittierenden Elemente>

[0315] Methods for manufacturing the light-emitting elements of this example are described below. <<Herstellung des Licht emittierenden Elements 3> >

[0316] Electrode 101 was formed from an ITSO film with a thickness of 70 nm on a glass substrate. It should be noted that the area of ​​electrode 101 was 4 mm². 2 (2 mm × 2 mm) was set.

[0317] Next, DBT3P-II and molybdenum oxide (MoO3) were deposited as a hole injection layer 111 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 in a thickness of 40 nm over the electrode 101.

[0318] Then, 9-[3-(9-Phenyl-9H-fluoren-9-yl)phenyl]-9H-carbazole (abbreviation: mCzFLP) was deposited as a hole transport layer 112 by evaporation in a thickness of 20 nm over the hole injection layer 111.

[0319] Next, 130 4mCzBPBfpm, Tris[2-(1H-pyrazol-1-yl-κN] was used as the light-emitting layer. 2 )phenyl-κC]iridium(III) (abbreviation: Ir(ppz)3) and 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-[1]benzopyrano[6,7,8-ij]quinolizin-11-one (abbreviation: Coumarin 545T) were deposited by co-evaporation in a weight ratio of 4mCzBPBfpm:Ir(ppz)3:Cumarin 545T = 0.8:0.2:0.005 to a thickness of 30 nm. In the light-emitting layer 130, Coumarin 545T is a fluorescent compound.

[0320] Then, as an electron transport layer 118, 4mCzBPBfpm and NBPhen were successively deposited by evaporation to a thickness of 15 nm and 20 nm, respectively, over the light-emitting layer 130. Subsequently, as an electron injection layer 119, LiF was deposited by evaporation to a thickness of 1 nm over the electron transport layer 118.

[0321] Next, aluminum (Al) was formed as electrode 102 with a thickness of 200 nm above the electron injection layer 119.

[0322] Then, in a glovebox containing a nitrogen atmosphere, a glass substrate was fixed to the glass substrate on which the organic materials were deposited, using a sealant for an organic EL device, thereby sealing the light-emitting element 3. Specifically, after the sealant had been applied to enclose the organic materials deposited on the glass substrate and the glass substrate had been fixed to the glass substrate for sealing, irradiation with UV light at a wavelength of 365 nm at 6 J / cm² was performed. 2 and a heat treatment at 80 °C for one hour was carried out. The light-emitting element 3 was obtained through the preceding steps. <<Herstellung des Licht emittierenden Vergleichselements 4> >

[0323] The light-emitting reference element 4 was produced by the same steps as those of the light-emitting element 3, except for the step to form the light-emitting layer 130.

[0324] The light-emitting layer 130 of the light-emitting reference element 4 consisted of 4mCzBPBfpm and Ir(ppz)3, deposited by co-evaporation in a weight ratio of 4mCzBPBfpm:Ir(ppz)3 = 0.8:0.2 to a thickness of 30 nm. The light-emitting layer 130 of the light-emitting reference element 4 differs from that of the light-emitting element 3 in that it does not contain coumarin 545T, which is a fluorescent compound. <<Herstellung des Licht emittierenden Vergleichselements 5> >

[0325] The light-emitting reference element 5 was produced by the same steps as those of the light-emitting element 3, except for the steps to form the light-emitting layer 130 and the electron transport layer 118.

[0326] Light-emitting layer 130, consisting of 4.6mCzP2Pm, Ir(ppz)3, and coumarin 545T, was deposited by co-evaporation in a weight ratio of 4.6mCzP2Pm:Ir(ppz)3:coumarin 545T = 0.8:0.2:0.005 to a thickness of 30 nm. In light-emitting layer 130, coumarin 545T is a fluorescent compound that serves as the third organic compound. Light-emitting reference element 5 has the same structure as light-emitting element 3, except that 4.6mCzP2Pm, which comprises a pyrimidine framework, is used as the host material in light-emitting layer 130.

[0327] Then, as an electron transport layer 118, 4.6 mCzP2Pm and BPhen were successively deposited by evaporation to a thickness of 15 nm and 20 nm, respectively, over the light-emitting layer 130. Subsequently, as an electron injection layer 119, LiF was deposited by evaporation to a thickness of 1 nm over the electron transport layer 118. <Eigenschaften der Licht emittierenden Elemente>

[0328] Next, the properties of the fabricated light-emitting element 3 and the fabricated light-emitting reference elements 4 and 5 were measured. It should be noted that the measurement procedures are the same as those of Example 1.

[0329] Fig. 17, Fig. 18 and Fig. Figure 19 shows the luminance-current efficiency properties, the voltage-current properties, and the luminance-external quantum efficiency properties of the light-emitting element 3 and the light-emitting comparison elements 4 and 5. Fig. Figure 20 shows the electroluminescence spectra obtained when a current with a current density of 2.5 mA / cm² is applied. 2 The measurements were obtained for light-emitting element 3 and light-emitting reference elements 4 and 5. It should be noted that the measurement of the light-emitting elements was carried out at room temperature (in an atmosphere maintained at 23 °C).

[0330] Table 4 shows the element properties of light-emitting element 3 and light-emitting comparison elements 4 and 5 at approximately 1000 cd / m². 2 . [Table 4] Voltage (V) Current density (mA / cm³) 2 ) CIE chromaticity (x, y) Luminance (cd / m²) 2 ) Power efficiency (cd / A) Energy efficiency (lm / W) external quantum efficiency (%) Light-emitting element 3 3,40 2,3 (0,274, 0,655) 1030 44,8 41,4 12,9 light-emitting reference element 4 3,30 1,3 (0,334, 0,611) 885 65,7 62,5 18,9 light-emitting reference element 5 3,70 2,5 (0,275, 0,653) 1120 44,6 37,9 13,1

[0331] As in Fig. As shown in Figure 20, the electroluminescence spectrum of both light-emitting element 3 and light-emitting reference element 5 exhibits green light emission with a peak wavelength of 512 nm and a full width at half maximum (FWHM) of approximately 63 nm. Therefore, light emitted by light-emitting element 3 and light-emitting reference element 5 originates from coumarin 545T, which is the fluorescent compound. It should be noted that Ir(ppz)3, used in light-emitting element 3 and light-emitting reference element 5, is known to emit blue light at low temperatures and no observable light at room temperature; light originating from Ir(ppz)3 was not observed here.

[0332] The light-emitting reference element 4 has a broad electroluminescence spectrum with a peak wavelength of 532 nm and a full width at half maximum (FWHM) of 83 nm. Light emitted by the light-emitting reference element 4 originates from an exciplex formed by 4mCzBPBfpm and Ir(ppz)3, which will be described later. Therefore, in comparison to the light-emitting reference element 4, the light-emitting element 3 of an embodiment of the present invention has a short peak wavelength and a small FWHM in its electroluminescence spectrum and can emit light with high color purity. Accordingly, the light-emitting element of an embodiment of the present invention is suitable for display devices.

[0333] As in Fig. 17, Fig. As shown in Figure 19 and Table 4, the light-emitting element 3 and the light-emitting comparison elements 4 and 5 exhibit high emission efficiencies (current efficiency, power efficiency, and external quantum efficiency). Furthermore, the external quantum efficiency of the light-emitting element 3 is greater than 6.25%. This is because, in addition to light originating from singlet excitons generated by recombination of charge carriers (holes and electrons), the light-emitting element 3 emits light originating from triplet excitons or light originating from singlet excitons generated by reverse intersystem crossing in the exciplex of triplet excitons. The light-emitting comparison element 4 emits light originating from the exciplex, and the light-emitting element 3 is the light-emitting element of an embodiment of the present invention that utilizes ExEF. <Zeitaufgelöste Emissionsmessung>

[0334] Next, a time-resolved emission measurement was performed on the light-emitting element 3 and the light-emitting comparison element 4.

[0335] A picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics KK) was used for the measurement. To assess the lifetime of fluorescence in the light-emitting elements, a pulse voltage with a square wave was applied to the elements, and a time-resolved measurement of the emitted light attenuated by the voltage decay was performed using a streak camera. The pulse voltage was applied at a frequency of 10 Hz. Integration of data obtained from repeated measurements yielded data with a high signal-to-noise ratio. The measurement was performed at room temperature (300 K) under the following conditions: A pulse voltage of approximately 3 V to 4 V was applied, resulting in a luminance of the light-emitting elements close to 1000 cd / m². 2 The pulse time width was 100 µs, a negative bias voltage was -5 V (at the time when the elements were not operating) and the measurement time was 20 µs. Fig. Figure 21 shows the measurement results. Fig. 21 The vertical axis represents the emission intensity normalized to the value in a state in which charge carriers are continuously injected (i.e., the pulse voltage is applied), and the horizontal axis represents the time elapsed after the pulse voltage has dropped.

[0336] As in Fig. As shown in Figure 21, the attenuation rate of light emitted by light-emitting element 3 is higher than that of light emitted by light-emitting reference element 4. This means that the excitation energy is quickly converted into light in light-emitting element 3. Therefore, the light can be extracted efficiently even when the exciton density in the light-emitting layer is high (a large amount of current flows). For this reason, the roll-off at light-emitting element 3 is low, as shown in Figure 21. Fig. 17 and Fig. Figure 19 shows such a small roll-off. This is one of the features of the light-emitting element of an embodiment of the present invention. <cv-messergebnisse>

[0337] The electrochemical properties (oxidation and reduction reaction properties) of the aforementioned compounds were then measured by cyclic voltammetry (CV). An electrochemical analyzer (ALS 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 measurement, the potential of a working electrode relative to the reference electrode was varied within a reasonable range to obtain the oxidation and reduction peak potentials. Furthermore, the HOMO and LUMO levels of each compound were calculated from the assumed redox potential (-4.94 eV) of the reference electrode and the obtained peak potentials.

[0338] The HOMO and LUMO levels of Ir(ppz)3, obtained from the CV measurements, were -5.39 eV and -1.77 eV, respectively. The HOMO and LUMO levels of 4mCzBPBfpm were -5.91 eV and -2.97 eV, respectively. The HOMO and LUMO levels of 4.6mCzP2Pm were -5.89 eV and -2.88 eV, respectively.

[0339] As described above, the LUMO level of 4mCzBPBfpm is lower than that of Ir(ppz)3, and the HOMO level of Ir(ppz)3 is higher than that of 4mCzBPBfpm. Therefore, when these compounds are used for a light-emitting layer, as in the case of light-emitting element 3 and light-emitting reference element 4, electrons and holes, acting as charge carriers, are efficiently injected from a pair of electrodes into 4mCzBPBfpm and Ir(ppz)3, and thus 4mCzBPBfpm and Ir(ppz)3 can form an exciplex. Similarly, 4.6mCzP2Pm and Ir(ppz)3 can form an exciplex; thus, light-emitting reference element 5 is also a light-emitting element that utilizes ExEF.

[0340] The exciplex formed by 4mCzBPBfpm and Ir(ppz)3 has the LUMO level in 4mCzBPBfpm and the HOMO level in Ir(ppz)3. The energy difference between the LUMO level of 4mCzBPBfpm and the HOMO level of Ir(ppz)3 is 2.42 eV. This value is essentially the same as the emission energy (2.33 eV) derived from the peak wavelength of the emission spectrum of the light-emitting reference element 4 in Fig. 20 was calculated. This indicates that the emission spectrum of the light-emitting reference element 4 corresponds to the light emission of the exciplex formed by 4mCzBPBfpm and Ir(ppz)3. The difference between the S1 level and the T1 level of the exciplex is small; thus, the emission energy can be considered as the energy (2.33 eV) of the S1 level and the T1 level of the exciplex. <Beziehung zwischen dem Emissionsspektrum des Exciplexes und dem Absorptionsspektrum des Gastmaterials>

[0341] Fig. Figure 22 shows the measurement result of the absorption spectrum of coumarin 545T in a toluene solution. Fig. Figure 22 also shows the emission spectrum of the exciplex in the light-emitting reference element 4. The absorption spectrum was measured using a UV-VIS spectrophotometer (V-550, manufactured by JASCO Corporation) at room temperature (in an atmosphere maintained at 23 °C).

[0342] As in Fig. As shown in Figure 22, the absorption spectrum of coumarin 545T and the emission spectrum of the exciplex in the light-emitting reference element 4 partially overlap. Thus, the excitation energy can be efficiently transferred from the exciplex formed by 4mCzBPBfpm and Ir(ppz)3 to coumarin 545T, which is the fluorescent compound. Accordingly, a light-emitting element can be provided that emits light with a peak wavelength shorter than that of the electroluminescence spectrum of the exciplex, such as the light-emitting element 3 with the electroluminescence spectrum shown in Figure 22. Fig. 20 is shown. <Messung des T1-Niveaus>

[0343] Next, to obtain the T1 level of the compound used in the light-emitting layer 130, a thin film of 4 mCzBPBfpm was formed over a quartz substrate by a vacuum evaporation process, and then the emission spectrum of this thin film was measured at a low temperature (10 K). 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 temperature of 10 K.

[0344] As a result, the T1 level of 4mCzBPBfpm was calculated to be 2.68 eV.

[0345] Furthermore, an absorption spectrum and an emission spectrum were measured to estimate the T1 level of Ir(ppz)3. A dichloromethane solution in which Ir(ppz)3 was dissolved was prepared, and the absorption spectrum was measured using a quartz cell. The absorption spectrum was measured with a UV-VIS spectrophotometer (V-550, manufactured by JASCO Corporation). The absorption spectra of the quartz cell and the solvent were subtracted from the measured absorption spectrum of the sample. The measurement was performed at room temperature (in an atmosphere maintained at 23 °C).

[0346] The absorption edge was calculated from the data of the aforementioned absorption spectrum, and the transition energy was estimated assuming a direct transition; the transition energy of Ir(ppz)3 was calculated to be 3.27 eV. Since Ir(ppz)3 is a phosphorescent compound, the absorption edge on the lowest energy side is an absorption band based on the transition from the triplet excitation state. Thus, the T1 level of Ir(ppz)3 was calculated from the absorption edge to be 3.27 eV.

[0347] From the above measurements, the T1 level of 4mCzBPBfpm is lower than that of Ir(ppz)3, and the T1 level of 4mCzBPBfpm is higher than that (2.33 eV) of the exciplex formed by 4mCzBPBfpm and Ir(ppz)3. Therefore, the triplet excitation energy of the exciplex formed by 4mCzBPBfpm and Ir(ppz)3 is not deactivated by either 4mCzBPBfpm or Ir(ppz)3. Consequently, the triplet excitation energy of the exciplex can be converted into light, converted into singlet excitation energy by reverse intersystem crossing, or transferred to a fluorescent compound.

[0348] Furthermore, when measuring the emission spectrum of Ir(ppz)3 at room temperature, no light emitted by Ir(ppz)3 was observed. T. Sajoto et al., J. Am. Chem. Soc., 2009, 131, pp. 9813-9822, discloses that the emission quantum yield of Ir(ppz)3 at room temperature is less than 1%. This suggests that Ir(ppz)3 is a material that does not emit light at room temperature. This means that even when using a compound with an emission quantum yield of less than 1%, a light-emitting element with high emission efficiency can be obtained. <Zuverlässigkeit der Licht emittierenden Elemente>

[0349] Fig. Figure 23 shows the results of an operational test at a constant current of 0.5 mA, performed on the light-emitting element 3 and the light-emitting comparison elements 4 and 5. Fig. It was shown in Figure 23 that the light-emitting element 3 exhibited higher reliability than the light-emitting comparison elements 4 and 5. The difference between light-emitting element 3 and light-emitting comparison element 4 lies in whether the fluorescent compound is present. As described above, light from the fluorescent compound was obtained in light-emitting element 3, and light from the exciplex was obtained in light-emitting comparison element 4. This demonstrates that reliability is improved when light emission from the fluorescent compound is obtained, as in the light-emitting element of one embodiment of the present invention. Furthermore, the difference between light-emitting element 3 and light-emitting comparison element 5 is the host material.As described above, the host material of light-emitting element 3 is the material with a benzofuropyrimidine framework, while the host material of light-emitting reference element 5 is the material with a pyrimidine framework. By using a material with a benzofuropyrimidine framework, a very reliable light-emitting element can thus be obtained.

[0350] As already described, one embodiment of the present invention can provide a light-emitting element with high emission efficiency and high reliability. Furthermore, one embodiment of the present invention can provide a light-emitting element with low drive voltage and low power consumption. [Example 3]

[0351] This example shows fabrication examples of the light-emitting element of an embodiment of the present invention and light-emitting comparison elements. The structure of each light-emitting element fabricated in this example is the same as that described in Fig. Figure 1A is shown. Table 5 shows the details of the element structures. The structure and abbreviations of compounds used in this example are shown below. Note that for the structures and abbreviations of the other compounds, reference can be made to Example 1. [Table 5] layer Reference sign Thickness (nm) material weight ratio Light-emitting element 6 electrode 102 200 Al - Electron injection layer 119 1 LiF - electron transport layer 11 8 (2) 10 NB Phen - 118(1) 20 4.8mDBtP2Bfpm - light-emitting layer 130 40 4.8mDBtP2Bfpm:PCCP:Ir(ppy)2(4dppy):TBRb 0,6:0,4:0,1:0,01 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 45 DBT3P-II:MoO3 1:0,5 electrode 101 70 ITSO - light-emitting reference element 7 electrode 102 200 Al - Electron injection layer 119 1 LiF - electron transport layer 118(2) 10 NB Phen - 118(1) 20 4.8mDBtP2Bfpm - light-emitting layer 130 40 4.8mDBtP2Bfpm:PCCP:Ir(ppy)2(4dppy) 0,6:0,4:0,1 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 45 DBT3P-II:MoO3 1:0,5 electrode 101 70 ITSO - light-emitting reference element 8 electrode 102 200 Al - Electron injection layer 119 1 LiF - electron transport layer 118(2) 10 NB Phen - 118(1) 20 4.6mDBTP2Pm-II - light-emitting layer 130 40 4.6mDBTP2Pm-II:PCCP:Ir(ppy)2(4dppy):TBRb 0,6:0,4:0,1:0,01 Hole transport layer 112 20 PCBBi1BP - Hole injection layer 111 45 DBT3P-II:MoO3 1:0,5 electrode 101 70 ITSO - <Herstellung der Licht emittierenden Elemente>

[0352] Methods for manufacturing the light-emitting elements of this example are described below. <<Herstellung des Licht emittierenden Elements 6> >

[0353] Electrode 101 was formed from an ITSO film with a thickness of 70 nm on a glass substrate. It should be noted that the area of ​​electrode 101 was 4 mm². 2 (2 mm × 2 mm) was set.

[0354] Next, DBT3P-II and molybdenum oxide (MoO3) were deposited as a hole injection layer 111 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 in a thickness of 45 nm over the electrode 101.

[0355] Then, 4,4'-Diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP) was deposited as a hole transport layer 112 by evaporation in a thickness of 20 nm over the hole injection layer 111.

[0356] Next, the light-emitting layer consisted of 130 4,8-bis[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4.8mDBtP2Bfpm), 9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carbazole (abbreviation: PCCP), [2-(4-phenyl-2-pyridinyl-κN)phenyl-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: Ir(ppy)2(4dppy)) and 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (abbreviation: TBRb) by co-evaporation in a weight ratio of 4.8mDBtP2Bfpm:PCCP:Ir(ppy)2(4dppy):TBRb = 0.6:0.4:0.1:0.01 is deposited in a thickness of 40 nm above the hole transport layer 112. In the light-emitting layer 130, TBRb is a fluorescent compound.

[0357] Then, as an electron transport layer 118, 4.8 mDBtP2Bfpm and NBPhen were successively deposited by evaporation to a thickness of 20 nm and 10 nm, respectively, over the light-emitting layer 130. Subsequently, as an electron injection layer 119, LiF was deposited by evaporation to a thickness of 1 nm over the electron transport layer 118.

[0358] Then, aluminum (Al) was formed as electrode 102 with a thickness of 200 nm above the electron injection layer 119.

[0359] Then, in a glovebox containing a nitrogen atmosphere, a glass substrate was fixed to the glass substrate on which the organic materials were deposited, using a sealant for an organic EL device, thereby sealing the light-emitting element 6. Specifically, after the sealant had been applied to enclose the organic materials deposited on the glass substrate and the glass substrate had been fixed to the glass substrate for sealing, the device was irradiated with UV light at a wavelength of 365 nm and an intensities of 6 J / cm². 2 and a heat treatment at 80 °C for one hour was carried out. The light-emitting element 6 was obtained through the preceding steps. <<Herstellung des Licht emittierenden Vergleichselements 7> >

[0360] The light-emitting reference element 7 was produced by the same steps as those of the light-emitting element 6, except for the step to form the light-emitting layer 130.

[0361] Light-emitting layer 130 of light-emitting reference element 7 was deposited by co-evaporation in a weight ratio of 4.8 mDBtP2Bfpm:PCCP:Ir(ppy)2(4dppy) = 0.6:0.4:0.1 to a thickness of 40 nm. Light-emitting layer 130 of light-emitting reference element 7 differs from that of light-emitting element 6 in that it does not contain TBRb, which is a fluorescent compound. <<Herstellung des Licht emittierenden Vergleichselements 8> >

[0362] The light-emitting reference element 8 was produced by the same steps as those of the light-emitting element 6, except for the steps to form the light-emitting layer 130 and the electron transport layer 118.

[0363] The light-emitting layer 130 of the light-emitting reference element 8 consisted of 4,6-bis[3-(dibenzothiophen-4-yl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), PCCP, Ir(ppy)2(4dppy), and TBRb, deposited by co-evaporation in a weight ratio of 4.6mDBTP2Pm-II:PCCP:Ir(ppy)2(4dppy):TBRb = 0.6:0.4:0.1:0.01 to a thickness of 40 nm. The light-emitting layer 130 of the light-emitting reference element 8 differs from that of the light-emitting element 6 in that it contains the material with a pyrimidine framework as the host material.

[0364] Then, as electron transport layers 118, 4.6mDBTP2Pm-II and NBPhen were successively deposited by evaporation at a thickness of 20 nm and 10 nm respectively over the light-emitting layer 130. <Eigenschaften der Licht emittierenden Elemente>

[0365] Next, the properties of the fabricated light-emitting element 6 and the fabricated light-emitting reference elements 7 and 8 were measured. It should be noted that the measurement procedures are the same as those of Example 1.

[0366] Fig. 24, Fig. 25 and Fig. Figures 26 show the luminance-current efficiency properties, the voltage-current properties, and the luminance-external quantum efficiency properties of the light-emitting element 6 and the light-emitting comparison elements 7 and 8. Fig. Figure 27 shows the electroluminescence spectra obtained when a current with a current density of 2.5 mA / cm² is applied. 2 The values ​​obtained were obtained for light-emitting element 6 and light-emitting reference elements 7 and 8. It should be noted that the measurement of the light-emitting elements was carried out at room temperature (in an atmosphere maintained at 23 °C).

[0367] Table 6 shows the element properties of the light-emitting element 6 and the light-emitting comparison elements 7 and 8 at approximately 1000 cd / m². 2 . [Table 6] Voltage (V) Current density (mA / cm³) 2 ) CIE chromaticity(x, y) Luminance (cd / m²) 2 ) Power efficiency (cd / A) Power efficiency (lm / VV) extreme quantum efficiency (%) Light-emitting element 6 3,40 1,0 (0,461, 0,534) 875 84,2 77,8 25,5 light-emitting reference element 7 3,50 1,3 (0,420, 0,570) 1060 82,9 74,4 23,9 light-emitting reference element 8 3,70 1,4 (0,457, 0,538) 1077 76,3 64,8 22,8

[0368] As in Fig. As shown in Figure 27, the electroluminescence spectrum of both light-emitting element 6 and light-emitting reference element 8 exhibits yellow light emission with a peak wavelength of 563 nm and a full width at half maximum (FWHM) of approximately 72 nm. Therefore, light emitted by light-emitting element 6 and light-emitting reference element 8 originates from TBRb, which is the fluorescent compound. It should be noted that light originating from Ir(ppy)₂(4dpy) was not observed from light-emitting element 6 or light-emitting reference element 8.

[0369] The light-emitting reference element 7 has a broad emission spectrum with a peak wavelength of 557 nm and a full width at half maximum (FWHM) of 80 nm. Light emitted by the light-emitting reference element 7 originates from Ir(ppy)₂(4dpy). Therefore, the light-emitting element 6 of an embodiment of the present invention has a smaller FWHM in the electroluminescence spectrum and can emit light with higher color purity than the light-emitting reference element 7. Accordingly, an embodiment of the present invention is suitable for display devices.

[0370] As in Fig. 24, Fig. As shown in Figure 26 and Table 6, light-emitting element 6 and light-emitting comparison elements 7 and 8 exhibit very high emission efficiencies (current efficiency, power efficiency, and external quantum efficiency). Furthermore, the external quantum efficiency of light-emitting element 6 is much higher than 6.25%. This is because light emission originating from triplet excitons is obtained alongside light emission originating from singlet excitons, indicating that the excitation energy is transferred via Ir(ppy)₂(4dppy), the phosphorescent compound, to TBRb, the fluorescent compound. Additionally, light-emitting element 6 has a higher external quantum efficiency than light-emitting comparison element 7, proving that the excitation energy deactivation rate is reduced and the excitation energy can be efficiently converted into light.

[0371] Furthermore, the roll-off of the light-emitting element 6 is small. Such a small roll-off is one of the features of the light-emitting element of an embodiment of the present invention. <cv-messergebnisse>

[0372] Next, the HOMO and LUMO levels of the aforementioned compounds were obtained by cyclic voltammetry (CV) measurement of their electrochemical properties (oxidation and reduction properties). The measurement procedure is the same as that of Example 2.

[0373] From the CV measurements, the HOMO and LUMO levels of 4.8mDBtP2Bfpm were -6.18 eV and -3.02 eV, respectively. The HOMO and LUMO levels of PCCP were -5.63 eV and -1.96 eV, respectively. The HOMO and LUMO levels of 4.6mDBTP2Pm-II were -6.22 eV and -2.83 eV, respectively.

[0374] Thus, 4.8mDBtP2Bfpm exhibits a higher HOMO level and a lower LUMO level than PCCP; therefore, 4.8mDBtP2Bfpm and PCCP form an exciplex combination in the light-emitting layer. Similarly, 4.6mDBTP2Pm-II and PCCP also form an exciplex combination.

[0375] The S1 and T1 levels of the exciplex formed by 4.8mDBtP2Bfpm and PCCP, calculated from the emission energy derived from the peak wavelength of the emission spectrum, are 2.61 eV. Here, the T1 level of Ir(ppy)2(4dpy) is 2.40 eV (calculated from the absorption edge of a dichloromethane solution). Therefore, both the singlet and triplet excitation energies of the exciplex can be transferred to Ir(ppy)2(4dpy). <Beziehung zwischen dem Emissionsspektrum des Exciplexes und dem Absorptionsspektrum des Gastmaterials>

[0376] Fig. Figure 28 shows the measurement result of the absorption spectrum of TBRb in a toluene solution. Fig. Figure 28 also shows the emission spectrum of the light-emitting reference element 7. The measurement was carried out in the same way as in Example 2.

[0377] As in Fig. As shown in Figure 28, the absorption spectrum of TBRb and the emission spectrum of the light-emitting reference element 7 partially overlap. Thus, the excitation energy can be efficiently transferred from the exciplex formed by 4.8mDBtP2Bfpm and PCCP to TBRb (the fluorescent compound) via Ir(ppy)2(4dpy). This energy transfer to TBRb via Ir(ppy)2(4dpy), the phosphorescent compound, allows the triplet excitation energy to contribute to the fluorescence. It should be noted that a similar mechanism likely also occurs for the light-emitting reference element 8.

[0378] Here, light-emitting element 6 exhibits a higher emission efficiency than light-emitting comparison element 8. The difference between these elements lies in the host material; the material with a benzofuropyrimidine backbone is used in light-emitting element 6, while the material with a pyrimidine backbone is used in light-emitting comparison element 8. Therefore, a light-emitting element can exhibit a higher emission efficiency by using a material with a benzofuropyrimidine backbone as its host material. <Zuverlässigkeit der Licht emittierenden Elemente>

[0379] Next, an operational test was performed at a constant current of 2 mA on the light-emitting element 6 and the light-emitting comparison elements 7 and 8. Table 7 shows LT 40 (the point in time at which the luminance decreases by 60%) of these light-emitting elements. [Table 7] LT 40 (h) Light-emitting element 6 3560 Light-emitting reference element 7 3090 Light-emitting reference element 8 1200

[0380] From Table 7, the light-emitting element 6, which is the light-emitting element of one embodiment of the present invention, exhibited the highest reliability. The difference between light-emitting element 6 and the light-emitting comparison element 7 lies in whether the fluorescent compound is present. This suggests that the energy transfer to the fluorescent material via the phosphorescent material leads to higher reliability. Furthermore, light-emitting element 6 exhibits higher reliability than light-emitting comparison element 8, which proves that a very reliable light-emitting element can be obtained by using a material with a benzofuropyrimidine framework, as in Example 2. Reference sign

[0381] 100: EL layer, 101: Electrode, 102: Electrode, 106: Light-emitting unit, 108: Light-emitting unit, 111: Hole injection layer, 112: Hole transport layer, 113: Electron transport layer, 114: Electron injection layer, 115: Charge generation layer, 116: Hole injection layer, 117: Hole transport layer, 118: Electron transport layer, 119: Electron injection layer, 120: Light-emitting layer, 130: Light-emitting layer, 131: Junction, 132: Junction, 133: Junction, 134: Junction, 150: Light-emitting element, 170: Light-emitting layer, 250: Light-emitting element, 601: Source driver circuit, 602: Pixel section, 603: Gate driver circuit, 604: Sealing substrate, 605: Sealing compound, 607: Space, 608: Conduit, 609: FPC, 610: Element substrate, 611: Switching TFT, 612: Current-controlling TFT, 613: Electrode, 614: Insulator, 616: EL layer, 617: Electrode, 618: Light-emitting element, 623: n-channel TFT, 624: p-channel TFT625: Desiccant, 900: Portable information terminal, 901: Housing, 902: Housing, 903: Display section, 905: Hinge section, 910: Portable information terminal, 911: Housing, 912: Display section, 913: Control knob, 914: External connection port, 915: Speaker, 916: Microphone, 917: Camera, 920: Camera, 921: Housing, 922: Display section, 923: Control knob, 924: Shutter release button, 926: Lens, 1001: Substrate, 1002: Base insulating film, 1003: Gate insulating film, 1006: Gate electrode, 1007: Gate electrode, 1008: Gate electrode, 1020: Interlayer insulating film 1021: Intermediate layer insulating film, 1022: Electrode, 1024B: Electrode, 1024G: Electrode, 1024R: Electrode, 1024W: Electrode, 1025B: Lower electrode, 1025G: Lower electrode, 1025R: Lower electrode, 1025W: Lower electrode, 1026: Partition, 1028: EL layer, 1029: Electrode, 1030: Black layer, 1031: Sealing substrate, 1032: Sealant, 1033: Base material, 1034B: Paint layer, 1034G: Paint layer1034R: Color layer, 1035: Black layer, 1036: Cover layer, 1037: Intermediate insulating film, 1040: Pixel section, 1041: Driver circuit section, 1042: Peripheral section, 1044B: Blue pixel, 1044G: Green pixel, 1044R: Red pixel, 1044W: White pixel, 2100: Robot, 2101: Light sensor, 2102: Microphone, 2103: Top camera, 2104: Speaker, 2105: Display, 2106: Bottom camera, 2107: Obstacle sensor, 2108: Movement mechanism, 2110: Arithmetic device, 5000: Housing, 5001: Display section, 5002: Display section, 5003: Speaker 5004: LED lamp, 5005: Control button, 5006: Connection port, 5007: Sensor, 5008: Microphone, 5012: Carrier, 5013: Earpiece, 5100: Cleaning robot, 5101: Display, 5102: Camera, 5103: Brush, 5104: Control knob, 5120: Dust, 5140: Portable electronic device, 5150: Portable information terminal, 5151: Housing, 5152: Display area, 5153: Curved section, 8501: Lighting device, 8502: Lighting device8503: Lighting device, 8504: Lighting device. < / substrat> < / elektroneninjektionsschicht> < / elektronentransportschicht> < / lochtransportschicht> < / lochinjektionsschicht> < / materialien>

Claims

[1] Light-emitting device comprising: a first electrode (101); a light-emitting layer (130) above the first electrode (101), wherein the light-emitting layer (130) comprises: a first organic compound (131) for converting triplet excitation energy into light; a second organic compound (132) with a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton; and a third organic compound (133) for converting singlet excitation energy into light; and a second electrode (102) above the light-emitting layer (130), wherein light emitted by the light-emitting layer (130) includes light emitted by the third organic compound (133) and wherein the first organic compound (131) comprises Ru, Rh, Pd, Os, Ir or Pt. [2] Light-emitting device according to claim 1, wherein the first organic compound (131) supplies excitation energy to the third organic compound (133). [3] Light-emitting device comprising: a first electrode (101); a light-emitting layer (130) above the first electrode (101), wherein the light-emitting layer (130) comprises: a first organic compound (131) for converting triplet excitation energy into light; a second organic compound (132) with a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton; and a third organic compound (133) for converting singlet excitation energy into light; and a second electrode (102) above the light-emitting layer (130), wherein the first organic compound (131) and the second organic compound (132) can form an exciplex, wherein light emitted by the light-emitting layer (130) includes light emitted by the third organic compound (133) and wherein the first organic compound (131) comprises Ru, Rh, Pd, Os, Ir or Pt. [4] Light-emitting device according to claim 3, wherein the exciplex supplies excitation energy to the third organic compound (133). [5] Light-emitting device according to claim 1 or 3, wherein the benzofuropyrimidine skeleton is a benzofuro[3,2-d]pyrimidine skeleton, and where the benzothienopyrimidine skeleton is a benzothieno[3,2-d]pyrimidine skeleton. [6] Light-emitting device according to claim 5, wherein the benzofuro[3,2-d]pyrimidine skeleton has a substituent at the 4-position or a substituent at the 8-position, and wherein the benzothieno[3,2-d]pyrimidine skeleton has a substituent at the 4-position or a substituent at the 8-position. [7] Light-emitting device according to claim 1 or 3, wherein the first organic compound (131) can emit phosphorescence. [8] Light-emitting device according to claim 3, wherein an emission spectrum of the exciplex overlaps an absorption band with the longest wavelength in an absorption spectrum of the third organic compound (133). [9] Light-emitting device according to claim 1 or 3, wherein the first organic compound (131) has an emission quantum yield of greater than or equal to 0% and less than or equal to 40% at room temperature. [10] Light-emitting device according to claim 3, wherein the exciplex is configured to emit light with a higher emission efficiency than the emission efficiency of the first organic compound (131). [11] Light-emitting device according to claim 1 or 3, wherein the third organic (133) compound can emit fluorescence. [12] Light-emitting device according to claim 1 or 3, wherein the difference between the lowest singlet excitation energy and the lowest triplet excitation energy of the first organic compound (131) is greater than or equal to 0 eV and less than or equal to 0.2 eV. [13] Display device comprising: the light-emitting device according to claim 1 or 3; and a color filter and / or a transistor. [14] Electronic device comprising: the display device according to claim 13; and a housing (5000, 5151) and / or a touch sensor. [15] Lighting device (8051-8054) comprising: the light-emitting device according to claim 1 or 3; and a housing (5000, 5151) and / or a touch sensor.

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