Light-emitting element and display device

Abstract

Light-emitting element comprising: a light-emitting layer, wherein the light-emitting layer comprises a first organic compound, a second organic compound and a third organic compound, wherein a LUMO level of one of the first organic compound and the second organic compound is higher than a LUMO level of the other of the first organic compound and the second organic compound, wherein a HOMO level of one of the first organic compound and the second organic compound is higher than a HOMO level of the other of the first organic compound and the second organic compound, wherein the first organic compound and the second organic compound in combination may form an exciplex, wherein the first organic compound can convert triplet excitation energy into light emission at room temperature, wherein the third organic compound can convert singlet excitation energy into light emission, and wherein light emitted by the light-emitting layer comprises light emitted by the third organic compound.

Description

Technical area

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

[0002] It should be noted that an embodiment of the present invention is not limited to the above technical field. The technical field of an embodiment of the invention disclosed in this specification and the like relates to an article, a method, or a manufacturing method. An embodiment of the present invention additionally relates to a process, a machine, a product, or a composition. Examples of the technical field of an embodiment of the present invention disclosed in this specification specifically include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a memory device, a driving method for any of them, and a manufacturing method for any 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). The basic structure of such a light-emitting element consists of a layer containing a light-emitting substance (an EL layer) sandwiched between a pair of electrodes. By applying a voltage between the electrodes of this element, light emission from the light-emitting substance can be obtained.

[0004] Since the above light-emitting element is a self-luminous type, a display device using this light-emitting element has the following advantages: high visibility, no need for backlighting, and low power consumption. Such a light-emitting element is also advantageous in that the element can be manufactured thinly and lightweight, and has a high response speed.

[0005] In a light-emitting element (e.g., an organic EL element) whose EL layer contains a light-emitting organic compound as the light-emitting substance and is provided between a pair of electrodes, applying a voltage between the pair of electrodes causes the injection of electrons from a cathode and holes from an anode into the EL layer with a light-emitting property, causing a current to flow. Through recombination of the injected electrons and holes, the light-emitting organic compound is excited to provide light emission.

[0006] It should be noted that the excited states that can be formed by an organic compound are a singlet excited state (S*) and a triplet excited state (T*). Light emission from the singlet excited state is called fluorescence, and light emission from the triplet excited state is called phosphorescence. The statistical generation ratio of S* to T* in the light-emitting element is 1:3. In other words, a light-emitting element containing a compound that emits phosphorescence (phosphorescent compound) has a higher luminous efficiency than a light-emitting element containing a compound that emits fluorescence (fluorescent compound). Accordingly, light-emitting elements containing phosphorescent compounds that can convert the energy of the triplet excited state into light emission have been actively developed in recent years.For example, in Non-Patent Document 1, the temperature dependence of the luminescence quantum yield of an Ir complex, which is a phosphorescent compound, is investigated in detail to find out the relationship between the molecular structure of an Ir complex and its luminescence quantum yield and the reason for it.

[0007] Among light-emitting elements containing phosphorescent compounds, a light-emitting element that emits blue light, in particular, has not been put into practical use so far due to the difficulty of developing a stable compound with a high triplet excitation energy level. For this reason, a light-emitting element containing a more stable fluorescent compound has been developed, and a technique for increasing the light-emitting efficiency of a light-emitting element containing a fluorescent compound (a fluorescent element) has been researched.

[0008] In addition to phosphorescent compounds, thermally activated delayed fluorescent (TADF) materials are known as materials that can convert part of the triplet excitation energy into light emission. In a thermally activated delayed fluorescent material, a singlet excited state is formed from a triplet excited state through reverse intersystem crossing, and the singlet excited state is converted into light emission.

[0009] To increase the luminous efficacy of a light-emitting element using a thermally activated, delayed-fluorescence material, not only efficient generation of a singlet excited state from a triplet excited state but also efficient light emission from a singlet excited state—that is, a high fluorescence quantum yield—is important for a thermally activated, delayed-fluorescence material. However, it is difficult to create a light-emitting material that meets these two criteria.

[0010] Patent Document 1 discloses a method: In a light-emitting element containing a thermally activated delayed fluorescent material and a fluorescent compound, a 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.

[0011] From SU, Shi-Jian [et al.]: A host material with a small singlet-triplet exchange energy for phosphorescent organic light-emitting diodes: guest, host, and exciplex emission. In: Organic electronics, Vol. 13, 2012, No. 10, pp. 1937-1947. - ISSN 1878-5530. DOI: 10.1016 / j.orgel.2012.06.009, a host material with a small singlet-triplet exchange energy is known.

[0012] US 2016 / 0 064 684 A1 discloses a light-emitting element with high emission efficiency which contains a fluorescent material as a light-emitting substance. [Reference][Patent document]

[0013] [Patent Document 1] Japanese Patent Application No. JP 2014045179A [Non-patent document]

[0014] [Non-Patent Document 1] T. Sajoto et al., Journal of American Chemical Society, Vol. 131, 9813 (2009). Disclosure of the invention

[0015] To increase the luminous efficacy of a light-emitting element containing a thermally activated, delayed-fluorescent material and a fluorescent compound, efficient generation of a singlet excited state from a triplet excited state is preferred. A method for efficiently forming a singlet excited state from a triplet excited state in a light-emitting element using an exciplex as the thermally activated, delayed-fluorescent material needs to be developed to further improve the luminous efficacy of the light-emitting element.

[0016] In view of the foregoing, an object of an embodiment of the present invention is to provide a light-emitting element having a high luminous efficacy. Another object of an embodiment of the present invention is to provide a light-emitting element with a low driving voltage. 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 highly reliable light-emitting element. Another object of an embodiment of the present invention is to provide a novel light-emitting element. Another object of an embodiment of the present invention is to provide a novel light-emitting device.Another object of an embodiment of the present invention is to provide a novel display device.

[0017] It should be noted that the description of the above object does not preclude the existence of other objects. In one embodiment of the present invention, it is unnecessary to fulfill all of the objects. Objects other than the above objects will become apparent from the explanation of the description and the like and can be deduced therefrom.

[0018] One embodiment of the present invention is a light-emitting element comprising a light-emitting layer. The light-emitting layer contains a first organic compound, a second organic compound, and a third organic compound. A LUMO level of one of the first organic compound and the second organic compound is higher than a LUMO level of the other of the first organic compound and the second organic compound. A HOMO level of one of the first organic compound and the second organic compound is higher than a HOMO level of the other of the first organic compound and the second organic compound. The first organic compound and the second organic compound can form an exciplex in combination. The first organic compound can convert triplet excitation energy into light emission at room temperature.The third organic compound can convert singlet excitation energy into light emission. Light emitted by the light-emitting layer includes light emitted by the third organic compound.

[0019] Another embodiment of the present invention is a light-emitting element comprising a light-emitting layer. The light-emitting layer contains a first organic compound, a second organic compound, and a third organic compound. A LUMO level of one of the first organic compound and the second organic compound is higher than or equal to a LUMO level of the other of the first organic compound and the second organic compound. A HOMO level of one of the first organic compound and the second organic compound is higher than or equal to a HOMO level of the other of the first organic compound and the second organic compound. The first organic compound and the second organic compound can form an exciplex in combination.The first organic compound cannot emit fluorescence at room temperature, but can emit phosphorescence. The third organic compound can emit fluorescence. Light emitted by the light-emitting layer includes light emitted by the third organic compound.

[0020] Another embodiment of the present invention is a light-emitting element comprising a light-emitting layer. The light-emitting layer contains a first organic compound, a second organic compound, and a third organic compound. A LUMO level of the first organic compound is higher than a LUMO level of the second organic compound. A HOMO level of the first organic compound is higher than a HOMO level of the second organic compound. The first organic compound and the second organic compound can form an exciplex in combination. The first organic compound contains Ru, Rh, Pd, Os, Ir, or Pt. Light emitted from the light-emitting layer includes light emitted from the third organic compound.

[0021] In each of the above structures, a lowest triplet excitation energy level of the first organic compound is preferably higher than or equal to a lowest triplet excitation energy level of the second organic compound.

[0022] In each of the above structures, the exciplex can preferably supply excitation energy to the third organic compound. Furthermore, an emission spectrum of the exciplex preferably has a region that overlaps with an absorption band on the longest wavelength side of the absorption spectrum of the third organic compound.

[0023] In each of the above structures, the first organic compound preferably comprises iridium. The first organic compound preferably comprises a ligand coordinated to iridium. The ligand preferably comprises a five-membered nitrogen-containing heterocyclic framework.

[0024] In each of the above structures, the second organic compound is preferably capable of transporting an electron. The second organic compound preferably comprises a π-electron-deficient heteroaromatic framework.

[0025] In each of the above structures, the first organic compound preferably has a luminescence quantum yield of greater than or equal to 0% and less than or equal to 40% at room temperature.

[0026] In each of the above structures, the luminous efficacy of the light emitted by the exciplex is preferably higher than the luminous efficacy of the light emitted by the first organic compound.

[0027] Another embodiment of the present invention is a display device comprising the light-emitting element having one of the above structures and a color filter and / or a transistor. Another embodiment of the present invention is an electronic device comprising the display device and a housing and / or a touch sensor. Another embodiment of the present invention is a lighting device comprising the light-emitting element having one of the above structures and a housing and / or a touch sensor. The category of an embodiment of the present invention includes not only a light-emitting device comprising a light-emitting element but also an electronic device comprising a light-emitting device.The light-emitting device in this specification therefore refers to an image display device or a light source (e.g., a lighting device). The light-emitting device may include, in its category, a display module in which a connector such as a flexible printed circuit (FPC) or a tape carrier package (TCP) is connected to a light-emitting element, a display module in which a printed circuit board is provided at the end of a TCP, and a display module in which an integrated circuit (IC) is directly mounted on a light-emitting element by a chip-on-glass (COG) method.

[0028] One embodiment of the present invention can provide a light-emitting element with high luminous efficiency. Another embodiment of the present invention can provide a light-emitting element with a low driving voltage. Another embodiment of the present invention can provide a light-emitting element with low power consumption. Another embodiment of the present invention can provide a highly reliable light-emitting element. Another embodiment of the present invention can provide a novel light-emitting element. Another embodiment of the present invention can provide a novel light-emitting device. Another embodiment of the present invention can provide a novel display device.

[0029] It should be noted that the description of these effects does not preclude the existence of further effects. An embodiment of the present invention may not necessarily have all of the effects described above. Further effects will become apparent from and can be derived from the explanation of the description, the drawings, the claims, and the like. Short description of the drawings

[0030] In the accompanying drawings: Fig. 1 is a schematic cross-sectional view of a light-emitting element of an embodiment of the present invention; Fig. 2A is a schematic cross-sectional view of a light-emitting layer of a light-emitting element of an embodiment of the present invention, and Fig. 2B and Fig. 2C represent the correlations of energy levels; Fig. 3 illustrates the correlation of energy levels in a light-emitting layer of a light-emitting element of an embodiment of the present invention; Fig. 4 is a schematic cross-sectional view of a light-emitting element of an embodiment of the present invention; Fig. 5 is a schematic cross-sectional view of a light-emitting element of an embodiment of the present invention; Fig. 6A and Fig. 6B are each a schematic cross-sectional view of a light-emitting element of an embodiment of the present invention; Fig. 7A and Fig. 7B is a plan view and a schematic cross-sectional view illustrating a display device of an embodiment of the present invention; Fig. 8A and Fig. 8B are schematic cross-sectional views each illustrating a display device of an embodiment of the present invention; Fig. 9A and Fig. 9B are schematic cross-sectional views each illustrating a display device of an embodiment of the present invention; Fig. 10 is a perspective view illustrating a display module of an embodiment of the present invention; Fig. 11A to Fig. 11G illustrate electronic devices of embodiments of the present invention; Fig. 12A to Fig. 12C illustrates a display device of an embodiment of the present invention; Fig. 13 illustrates a lighting device of an embodiment of the present invention; Fig. 14 shows luminance-current density characteristics of light-emitting elements of an example; Fig. 15 shows luminance-voltage characteristics of light-emitting elements of an example; Fig. 16 shows power efficiency-luminance characteristics of light-emitting elements of an example; Fig. 17 shows power efficiency-luminance characteristics of light-emitting elements of an example; Fig. 18 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example; Fig. 19 shows electroluminescence spectra of light-emitting elements of an example; Fig. 20 shows emission spectra of a thin film of an example; Fig. 21 shows absorption and emission spectra of a compound of an example; Fig. 22 shows luminance-current density characteristics of light-emitting elements of an example; Fig. 23 shows luminance-voltage characteristics of light-emitting elements of an example; Fig. 24 shows power efficiency-luminance characteristics of light-emitting elements of an example; Fig. 25 shows power efficiency-luminance characteristics of light-emitting elements of an example; Fig. 26 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example; Fig. 27 shows electroluminescence spectra of light-emitting elements of an example; Fig. 28 shows an absorption spectrum of a compound of an example; Fig. 29 shows an absorption spectrum of a compound of an example; Fig. 30 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example; Fig. 31 shows electroluminescence spectra of light-emitting elements of an example; and Fig. 32 shows transient EL curves of an example. Best mode for carrying out the invention

[0031] Embodiments and examples of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following description, and the modes and details can be changed in various ways without departing from the scope and spirit of the present invention. Therefore, the present invention should not be interpreted as being limited to the contents of the following embodiments and examples.

[0032] Note that the position, size, range, or the like of each structure illustrated in the drawings and the like is not precisely illustrated in some cases for ease of understanding. Therefore, the disclosed invention is not necessarily limited to the position, size, range, or the like disclosed in the drawings and the like.

[0033] Note that ordinal numbers such as "first" or "second" and the like are used in this specification and the like for convenience, and they do not indicate the order of steps or the arrangement order of layers. Therefore, for example, even if the term "first" is replaced with the term "second" or "third," a description can be made. Furthermore, the ordinal numbers in this specification and the like are not necessarily the same as the ordinal numbers that specify an embodiment of the present invention.

[0034] In the explanations of the modes of the present invention in this specification and the like based on the drawings, in some cases, the same components in different drawings are denoted by the same reference numerals.

[0035] In this description and the like, the terms "film" and "layer" may be interchanged. For example, the term "conductive layer" may be converted to the term "conductive film" in some cases. The term "insulating film" may also be converted to the term "insulating layer" in some cases.

[0036] In this specification and the like, a singlet excited state (S*) refers to a singlet state with excitation energy. An S1 level means the lowest level of the singlet excitation energy level, that is, the excitation energy level of the lowest singlet excited state (S1 state). A triplet excited state (T*) refers to a triplet state with excitation energy. A T1 level means the lowest level of the triplet excitation energy level, that is, the excitation energy level of the lowest triplet excited state (T1 state). Note that in this specification and the like, simple terms such as a "singlet excited state" and a "singlet excited energy level" in some cases mean the S1 state and the S1 level, respectively. Terms such as "singlet excited state" and "singlet excited energy level" may be used instead of the "singlet excited state" or "singlet excited energy level." For example, “triplet excited state” and “triplet excited energy level” in some cases refer to the T1 state or the T1 level.

[0037] In this specification and the like, a fluorescent compound refers to a compound that emits light in the visible light range when relaxing from the singlet excited state to the ground state. A phosphorescent compound refers to a compound that emits light in the visible light range at room temperature when relaxing from the triplet excited state to the ground state. That is, a phosphorescent compound refers to a compound that can convert triplet excitation energy into visible light.

[0038] It should be noted that in this specification and the like, “room temperature” means a temperature in the range of higher than or equal to 0 °C and lower than or equal to 40 °C.

[0039] In this specification and the like, a wavelength range of blue refers to a wavelength range greater than or equal to 400 nm and less than 490 nm, and blue light has at least one peak in this wavelength range in an emission spectrum. A wavelength range of green refers to a wavelength range greater than or equal to 490 nm and less than 580 nm, and green light has at least one peak in this wavelength range in an emission spectrum. A wavelength range of red refers to a wavelength range greater than or equal to 580 nm and less than or equal to 680 nm, and red light has at least one peak in this wavelength range in an emission spectrum. (Embodiment 1)

[0040] In this embodiment, a light-emitting element of an embodiment of the present invention will be described below with reference to Fig. 1, Fig. 2A to Fig. 2C and Fig. 3 described. <Strukturbeispiel des Licht emittierenden Elements>

[0041] First, the structure of the light-emitting element of an embodiment of the present invention will be described below with reference to Fig. 1 described.

[0042] Fig. 1 is a schematic cross-sectional view of a light-emitting element 150 of an embodiment of the present invention.

[0043] The light-emitting element 150 includes a pair of electrodes (an electrode 101 and an electrode 102) and an EL layer 100 between the pair of electrodes. The EL layer 100 includes at least one light-emitting layer 130.

[0044] The EL layer 100, which is Fig. 1, comprises, in addition to the light-emitting layer 130, functional layers such as a hole injection layer 111, a hole transport layer 112, an electron transport layer 118, and an electron injection layer 119.

[0045] Although in this embodiment, a description is given assuming that the electrode 101 and the electrode 102 of the pair of electrodes serve as the anode and the cathode, respectively, the structure of the light-emitting element 150 is not limited to this. That is, the electrode 101 may be a cathode, the electrode 102 may be an anode, and the arrangement order of the layers between the electrodes may be reversed. In other words, the hole-injection layer 111, the hole-transport layer 112, the light-emitting layer 130, the electron-transport layer 118, and the electron-injection layer 119 may be arranged in this order from the anode side.

[0046] The structure of the EL layer 100 is not limited to the structure shown in Fig. 1, as long as at least one of the hole injection layer 111, the hole transport layer 112, the electron transport layer 118, and the electron injection layer 119 is included. Alternatively, the EL layer 100 may include, for example, a functional layer having a function of lowering a hole or electron injection barrier, improving a hole or electron transport property, reducing a hole or electron transport property, or suppressing a quenching effect by an electrode. Note that the functional layer may be either a single layer or a multilayer. <Lichtemissionsmechanismus des Licht emittierenden Elements>

[0047] Next, the light emission mechanism of the light-emitting layer 130 will be described below.

[0048] In the light-emitting element 150 of one embodiment of the present invention, applying a voltage between the pair of electrodes (electrodes 101 and 102) causes electrons and holes to be injected from the cathode and anode, respectively, into the EL layer 100, causing a current to flow. Excitons are formed by recombination of the injected electrons and holes. The ratio (generation probability) of singlet excitons to triplet excitons generated by the recombination of charge carriers (electrons and holes) is approximately 1:3 according to the statistically obtained probability. In other words, the generation probability of singlet excitons is 25%, and the generation probability of triplet excitons is 75%. Thus, triplet excitons are important for contributing to light emission to increase the light efficiency of the light-emitting element.Accordingly, a material having a function of converting triplet excitation energy into light emission is preferably used as the light-emitting material for the light-emitting layer 130.

[0049] As a material capable of converting triplet excitation energy into light emission, a compound capable of emitting phosphorescence (hereinafter also referred to as a phosphorescent compound) can be specified. A phosphorescent compound in this specification and the like is a compound that emits phosphorescence but not fluorescence at a temperature higher than or equal to a low temperature (e.g., 77 K) and lower than or equal to room temperature (i.e., higher than or equal to 77 K and lower than or equal to 313 K). The phosphorescent compound preferably contains a heavy atom to efficiently convert triplet excitation energy into light emission.In the case where the phosphorescent compound contains a heavy atom, intersystem crossing between a singlet state and a triplet state is promoted by a spin-orbit interaction (an interaction between a spin angular momentum and an orbital angular momentum of an electron), and a transition between a singlet ground state and a triplet excited state of the phosphorescent compound is permitted. This means that the transition probability between the singlet ground state and the triplet excited state of the phosphorescent compound is increased; consequently, the light yield and absorption probability related to the transition can be increased. Accordingly, the phosphorescent compound preferably contains a metal element with a large spin-orbit interaction, particularly a transition metal element.In particular, a platinum group element (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) or platinum (Pt)), in particular iridium, is preferably included, since the probability of the direct transition between a singlet ground state and a triplet excited state can be increased.

[0050] A thermally activated delayed fluorescent (TADF) material can also be specified as a material with the function of converting triplet excitation energy into light emission. Note that the thermally activated delayed fluorescent material is a material that has a small difference between the T1 level and the S1 level and has the function of converting triplet excitation energy into singlet excitation energy through reverse intersystem crossing. Thus, the thermally activated delayed fluorescent material can upconvert triplet excitation energy into singlet excitation energy (i.e., reverse intersystem crossing) using a small amount of thermal energy and efficiently generate a singlet excited state.An exciplex has a very small difference between the S1 level and the T1 level and serves as a thermally activated, delayed fluorescent material that can convert triplet excitation energy into singlet excitation energy.

[0051] In one embodiment of the present invention, the light-emitting layer 130 contains two types of substances that form an exciplex. Furthermore, the light-emitting layer 130 contains, as the light-emitting material, a material capable of converting singlet excitation energy into light emission. With such a structure, triplet excitation energy is converted into singlet excitation energy through reverse intersystem crossing in an exciplex, and the singlet excitation energy is transferred to a light-emitting material, whereby light emission can be efficiently obtained from the light-emitting material.

[0052] The present inventors have discovered that by using a compound capable of independently converting triplet excitation energy into light emission as one of the compounds forming an exciplex, an exciplex capable of efficiently converting non-radiative triplet excitation energy into radiative singlet excitation energy or radiative triplet excitation energy can be formed. When a compound containing a heavy atom is used for one of the compounds forming an exciplex, intersystem crossing between a singlet state and a triplet state is promoted through a spin-orbit interaction (an interaction between a spin angular momentum and an orbital angular momentum of an electron).In other words, reverse intersystem crossing from a triplet excited state to a singlet excited state in an exciplex is promoted; thus, the generation probability of singlet excited states in the exciplex can be increased. As a result, an exciplex can be formed that efficiently emits light from a singlet excited state. The transition probability from a triplet excited state to a singlet ground state can also be increased; thus, an exciplex can be formed that efficiently emits light from a triplet excited state. This means that in both cases, the exciplex is ideally suited as a medium for Förster energy transfer (donor). There is no restriction on the excited state from which an exciplex emits light (since the singlet and triplet energies of the exciplex are close to each other).It should be noted that the excitation (emission) lifetime of an exciplex is significantly shorter than that of a conventional thermally activated, delayed-fluorescence material. This feature is reflected in the energy transfer from the exciplex to the light-emitting material, resulting in the suppression of degradation from an excited state, thus allowing the production of a light-emitting element with a substantially long drive lifetime. To achieve this, one of the compounds forming an exciplex preferably contains a metal element with a large spin-orbit interaction, particularly a transition metal element.In particular, a platinum group element (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) or platinum (Pt)), especially iridium, is preferably contained, since intersystem crossing between a singlet excited state and a triplet excited state in the exciplex can be increased.

[0053] In the above structure, a material with a high luminescence quantum yield does not need to be used to form an exciplex; thus, the design of a material is facilitated and a material can be selected from a wide range of possibilities.In particular, in the case where at least one of the compounds constituting an exciplex has a function of independently converting triplet excitation energy into light emission, or in the case where at least one of the compounds contains a platinum group element (Ru, Rh, Pd, Os, Ir or Pt), the luminescence quantum yield of the compound may be higher than or equal to 0% and lower than or equal to 50%, higher than or equal to 0% and lower than or equal to 40%, higher than or equal to 0% and lower than or equal to 25%, higher than or equal to 0% and lower than or equal to 10%, or higher than or equal to 0% and lower than or equal to 1% at room temperature or normal temperature.

[0054] Fig. 2A is a schematic cross-sectional view showing an example of the light-emitting layer 130 in Fig. 1. The light-emitting layer 130, which in Fig. 2A contains a compound 131, a compound 132, and a compound 133. In one embodiment of the present invention, compound 133 is preferably a fluorescent compound. Furthermore, compound 131 is preferably a phosphorescent compound. Although a structure using a phosphorescent compound as compound 131 will be described below, a compound that does not emit light at room temperature can be used as long as the compound contains a platinum group element.

[0055] The compound 131 and the compound 132 contained in the light-emitting layer 130 preferably form an exciplex.

[0056] As long as compounds 131 and 132 can form an exciplex, it is acceptable; however, preferably, one of them is a compound having a function of transporting holes (a hole-transport property) and the other is a compound having a function of transporting electrons (an electron-transport property). In this case, a donor-acceptor exciplex is easily formed; thus, an exciplex can be formed efficiently. In the case where compounds 131 and 132 are a compound having a hole-transport property and a compound having an electron-transport property, the carrier balance can be easily controlled by adjusting the mixing ratio. Specifically, the weight ratio of the compound having a hole-transport property to the compound having an electron-transport property is preferably within a range of 1:9 to 9:1.Since the charge carrier equilibrium can be easily controlled by the structure, a charge carrier recombination region can also be easily controlled.

[0057] In order for compound 131 and compound 132 to efficiently form an exciplex, the following is preferably satisfied: the highest occupied molecular orbital (also referred to as HOMO (highest occupied molecular orbital)) level of one of compounds 131 and 132 is higher than the HOMO level of the other of compounds 131 and 132, and the lowest unoccupied molecular orbital (also referred to as LUMO (lowest unoccupied molecular orbital)) level of one of compounds 131 and 132 is higher than the LUMO level of the other of compounds 131 and 132. Note that the HOMO level of compound 131 may be the same as the HOMO level of compound 132, or the LUMO level of compound 131 may be the same as the LUMO level of compound 132.

[0058] It should be noted that the LUMO levels and HOMO levels of the compounds can be obtained from the electrochemical properties (reduction potentials and oxidation potentials) of the compounds measured by cyclic voltammetry (CV).

[0059] For example, in the case where 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 the HOMO level of compound 132, and the LUMO level of compound 131 is preferably higher than the LUMO level of compound 132, as shown in an energy band diagram in Fig. 2B. Such a correlation of energy levels is suitable because electrons and holes, which serve as charge carriers, are easily injected from the pair of electrodes (electrode 101 and electrode 102) into junction 131 and junction 132, respectively.

[0060] In Fig. 2B, “Comp (131)” represents compound 131, “Comp (132)” represents compound 132, ΔEc1 represents the energy difference between the LUMO level and the HOMO level of compound 131, ΔEc2 represents the energy difference between the LUMO level and the HOMO level of compound 132, and ΔE Ex the energy difference between the LUMO level of compound 132 and the HOMO level of compound 131.

[0061] 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 essentially corresponds to the energy difference between the LUMO level of compound 132 and the HOMO level of compound 131 (ΔE Ex ), which is smaller than the energy difference between the LUMO level and the HOMO level of compound 131 (ΔE C1) and is smaller than the energy difference between the LUMO level and the HOMO level of compound 132 (ΔE C2 ). Thus, when 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.

[0062] Fig. Figure 2C shows the correlation of energy levels of compounds 131, 132 and 133 in the light-emitting layer 130. The following clarifies what terms and symbols in Fig. 2C represent: Comp (131): compound 131 (phosphorescent compound); Comp (132): compound 132; Guest (133): compound 133 (fluorescent compound) S C1 : the S1 level of compound 131; T C1 : the T1 level of compound 131; S C2: the S1 level of compound 132; T C2 : the T1 level of compound 132; S G : the S1 level of compound 133; T G : the T1 level of compound 133; S Ex : the S1 level of the exciplex; and T Ex : the T1 level of the exciplex.

[0063] In the light-emitting element of one embodiment of the present invention, compound 131 and compound 132 contained in light-emitting layer 130 form the exciplex. The S1 level of the exciplex (S Ex ) and the T1 level of the exciplex (T Ex ) are close to each other (see route A1 in Fig. 2C).

[0064] An exciplex is an excited state formed by two types of materials and is mainly formed by one of the following two processes.

[0065] One of the processes is an electroplex. In this specification and the like, an electroplex refers to an exciplex formed by the interaction between the ionized compounds 131 and 132 (in a cation state or an anion state) formed as a result of charge carrier injection. Note that the formation process of an electroplex occurs upon electrical excitation. In this embodiment, the formation process of an electroplex corresponds to a process in which one of the compounds 131 and 132 accepts holes and the other accepts electrons, and the compounds 131 and 132 interact with each other to instantly form an exciplex. In the formation process of an electroplex, an exciplex is instantly formed without forming an excited state from the compound 131 or the compound 132 itself. Thus, the properties such asThe excitation lifetime and the luminescence quantum yields of the compounds (compounds 131 and 132) forming an exciplex have no effect on the exciplex formation process. In other words, an embodiment of the present invention can efficiently form an exciplex even when the luminescence quantum yields of the compounds (compounds 131 and 132) forming an exciplex are low. Note that in this formation process, the S1 level of compound 131 (S. C1 ) higher or lower than the S1 level of compound 132 (S C2 ) and the T1 level of compound 131 (T C1 ) higher or lower than the T1 level of compound 132 (T C2 ) can be.

[0066] The other of the processes is a process for forming an exciplex when a compound that is brought into an excited state interacts with the other compound in a ground state by receiving excitation energy. This exciplex formation process can occur upon light excitation and electrical excitation. In this embodiment, the exciplex formation process corresponds to a process in which one of the compounds 131 and 132 receives light or electrical energy to be brought into an excited state and immediately interacts with the other in a ground state to form an exciplex. In this exciplex formation process, excitation energy can be supplied from the T1 level of the compound (T C1 ) to the T1 level of compound 132 (T C2) even if the compound 131 is placed in an excited state and the deactivation rate of the excited state is fast, as long as the T1 level of the compound 131 (T C1 ) higher than or equal to the T1 level of compound 132 (T C2 ). After the excitation energy from the T1 level of compound 131 (T C1 ) to the T1 level of compound 132 (T C2 ), compound 131 and compound 132 can form an exciplex. Thus, an embodiment of the present invention can efficiently form an exciplex even when the deactivation rate of the excited state of compound 131 is fast and the luminescence quantum yield of compound 131 is low. It should be noted that in this formation process, the S1 level of compound 131 (S C1 ) higher or lower than the S1 level of compound 132 (S C2 ) can be.

[0067] When an exciplex formed by any of the above processes loses excitation energy and is brought into a ground state by light emission, supplying excitation energy to another material, or the like, two substances constituting the exciplex serve as the original two kinds of substances.

[0068] Since the excitation energy levels of the exciplex (S Ex and T Ex ) are lower than the S1 levels of the materials (compounds 131 and 132) forming an exciplex (S C1 and S C2 ), an excitation state with lower excitation energy can be formed. Accordingly, the drive voltage of the light-emitting element 150 can be reduced.

[0069] Since the S1 level and the T1 level of an exciplex (S Ex and T Ex) are close to each other, the exciplex has a function of emitting thermally activated delayed fluorescence. In other words, the exciplex has a function of converting triplet excitation energy into singlet excitation energy by reverse intersystem crossing (upconversion). Thus, part of the triplet excitation energy generated in the light-emitting layer 130 is converted into singlet excitation energy by the exciplex. To achieve this conversion, the energy difference between the S1 level and the T1 level of the exciplex (S Ex and T Ex ) is preferably greater than 0 eV and less than or equal to 0.2 eV, more preferably greater than 0 eV and less than or equal to 0.1 eV. It should be noted that the T1 level of the exciplex (T Ex ) is preferably lower than the T1 levels of the materials (compounds 131 and 132) forming an exciplex (T C1 and T C2) to efficiently induce reverse intersystem crossing. In this case, the probability of quenching of the triplet excitation energy of the exciplex formed by compound 131 and compound 132 is reduced, leading to efficient inducement of reverse intersystem crossing from triplet excitation energy to singlet excitation energy by the exciplex.

[0070] Furthermore, the singlet excitation energy level (S Ex ) of the exciplex is preferably higher than the singlet excitation energy level (S G ) of a 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 separated from the singlet excitation energy level of the exciplex (S Ex ) to the singlet excitation energy level of compound 133 (S G ) can be transferred.

[0071] A compound containing a heavy atom is used as one of the compounds forming an exciplex in one embodiment of the present invention, which promotes intersystem crossing between a singlet state and a triplet state. Thus, an exciplex can be formed in which the triplet excited state can be converted to the singlet ground state (i.e., an exciplex capable of emitting phosphorescence). In this case, the triplet excitation energy level (T Ex ) of the exciplex is preferably higher than the singlet excitation energy level (S G ) of a compound 133, which serves as a light-emitting material. With such an energy level correlation, the triplet excitation energy of the formed exciplex can be separated from the triplet excitation energy level of the exciplex (T Ex ) to the singlet excitation energy level of compound 133 (S G). It should be noted that in some cases it is difficult to clearly distinguish fluorescence and phosphorescence in an emission spectrum because the S1 level and the T1 level of the exciplex (S Ex and T Ex ) are close together. In this case, fluorescence and phosphorescence can sometimes be distinguished by their emission lifetimes.

[0072] Through the energy transfer process described above, compound 133 becomes a singlet excited state and can emit light (see route A2 in Fig. 2C).

[0073] In order to obtain efficient light emission from the singlet excited state of compound 133 serving as a light-emitting material, the fluorescence quantum yield of compound 133 is preferably high, particularly 50% or higher, more preferably 70% or higher, even more preferably 90% or higher.

[0074] It should be noted that since compound 133 serves as a fluorescent compound and the direct transition from a singlet ground state to a triplet excited state is forbidden in compound 133, it is unlikely that energy transfer from the singlet excitation energy level of the exciplex (S Ex ) to the triplet excitation energy level of compound 133 (T G ) is the main energy transfer process.

[0075] If a transfer of the triplet excitation energy from the triplet excitation energy level (T Ex ) of the exciplex to the triplet excitation energy level (T G ) of compound 133, the triplet excitation energy is deactivated (see route A3 in Fig. 2C). Therefore, energy transfer of route A3 is preferably less likely to occur because the efficiency of generating the triplet excited state of compound 133 may be reduced and thermal deactivation may be reduced. To satisfy this condition, the weight ratio of compound 133 to the total weight of compounds 131 and 132 is preferably low, particularly preferably greater than or equal to 0.001 and less than or equal to 0.05, even more preferably greater than or equal to 0.001 and less than or equal to 0.01.

[0076] It should be noted that when the direct charge carrier recombination process is dominant in the compound 133, a large number of triplet excitons are generated in the light-emitting layer 130, resulting in reduced light emission efficiency due to thermal deactivation. Therefore, the probability of the energy transfer process via the exciplex formation process (routes A1 and A2 in Fig. 2C) is higher than the probability of the direct charge carrier recombination process in compound 133, since the efficiency of generating the triplet excited state of compound 133 may be reduced and thermal deactivation may be reduced. Thus, as described above, the weight ratio of compound 133 to the total weight of compounds 131 and 132 is preferably low, particularly preferably greater than or equal to 0.001 and less than or equal to 0.05, more preferably greater than or equal to 0.001 and less than or equal to 0.01.

[0077] For example, in the case where 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 the HOMO level of compound 132, and the LUMO level of compound 131 is preferably higher than the LUMO level of compound 132 to make the formation process of an electroplex more likely. Specifically, 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 a correlation between energy levels is suitable because electrons and holes serving as charge carriers are easily injected from the pair of electrodes (electrodes 101 and 102) into junction 131 and junction 132, respectively.

[0078] Compound 131 may have an electron transport property, and compound 132 may have a hole transport property. In this case, the HOMO level of compound 132 is preferably higher than the HOMO level of compound 131, and the LUMO level of compound 132 is preferably higher than the LUMO level of compound 131, as shown in an energy band diagram in Fig. 3 shown.

[0079] 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 greater than or equal to 0.01 and less than or equal to 0.5, more preferably greater than or equal to 0.05 and less than or equal to 0.3.

[0080] By efficiently performing all the energy transfer processes of routes A1 and A2 in the manner described above, both the singlet excitation energy and the triplet excitation energy generated in the light-emitting layer 130 can be efficiently converted into the singlet excitation energy of the compound 133, whereby the light-emitting element 150 can emit light with high luminous efficiency.

[0081] The processes described above via routes A1 and A2 may be referred to in this specification 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 transferred from the exciplex to the fluorescent compound.

[0082] When the light-emitting layer 130 has the structure described above, light emission from the fluorescent compound of the light-emitting layer 130 can be obtained efficiently. <Energieübertragungsmechanismus>

[0083] Here, factors that govern the processes of intermolecular energy transfer are described. Two mechanisms have been proposed for intermolecular energy transfer: the Förster mechanism (dipole-dipole interaction) and the Dexter mechanism (electron exchange interaction). Here, an energy transfer process is described between molecules of the first material in an excited state and the second material in a ground state; the same can also apply to the case where one of them is an exciplex. <<Förster-Mechanismus> >

[0084] In the Förster mechanism, no direct contact between molecules is necessary for energy transfer, and energy is transferred through a resonance phenomenon of dipole vibration between a first material and a second material. Through the resonance phenomenon of dipole vibration, the first material transfers energy to the second material, and thus the first material, which is in an excited state, is brought to a ground state, and the second material, which is in a ground state, is brought to an excited state. Note that the rate constant k h*→g of the Förster mechanism is represented by formula (1). [Formula 1] kh*→g=9000c4K2ln10128π5n4NτR6∫f'h(v)εg(v)v4dv

[0085] In formula (1) v represents a frequency, f' h(v) represents a normalized emission spectrum of the first material (a fluorescence spectrum upon energy transfer from a singlet excited state, and a phosphorescence spectrum upon energy transfer from a triplet excited state), ε g (v) represents a molar absorption coefficient of the second material, N represents the Avogadro number, n represents a refractive index of a medium, R represents an intermolecular distance between the first material and the second material, τ represents a measured lifetime of an excited state (fluorescence lifetime or phosphorescence lifetime), c represents the speed of light, ϕ represents a luminescence quantum yield (a fluorescence quantum yield upon energy transfer from a singlet excited state, and a phosphorescence quantum yield upon energy transfer from a triplet excited state), and K 2represents a coefficient (0 to 4) for the orientation of a transition dipole moment between the first material and the second material. It should be noted that for random orientation K 2 = 2 / 3 applies. < <dexter-mechanismus>>

[0086] In the Dexter mechanism, the first material and the second material are near a contact-effective region where their orbitals overlap, and the first material, which is in an excited state, and the second material, which is in a ground state, exchange their electrons, resulting in energy transfer. Note that the rate constant k h*→g of the Dexter mechanism is represented by formula (2). [Formula 2] kh*→g=(2πh)K2exp(−2RL)∫f'h(v)ε'g(v)dv

[0087] In formula (2), h represents a Planck constant, K represents a constant with an energy dimension, v represents a frequency, f' h (v) represents a normalized emission spectrum of the first material (the fluorescence spectrum upon energy transfer from a singlet excited state, and the phosphorescence spectrum upon energy transfer from a triplet excited state), ε' g (v) represents a normalized absorption spectrum of the second material, L represents an effective molecular radius, and R represents an intermolecular distance between the first material and the second material.

[0088] Here, the energy transfer efficiency from the first material to the second material (energy transfer efficiency ϕ ET ) is represented by formula (3). In the formula, k r a rate constant of a light emission process (fluorescence during energy transfer from a singlet excited state, and phosphorescence during energy transfer from a triplet excited state) of the first material, k n represents a rate constant of a process without light emission (thermal deactivation or intersystem crossing) of the first material, and τ represents a measured lifetime of an excited state of the first material. [Formula 3] ϕET=kh*→gkr+kn+kh*→g=kh*→g(1τ)+kh*→g

[0089] According to formula (3), it has been found that the energy transfer efficiency ϕ ET by increasing the rate constant k h*→g in the energy transfer can be increased, so that another competing rate constant k r + k n (= 1 / τ) becomes relatively small. <<Konzept zur Förderung der Energieübertragung> >

[0090] First, energy transfer through the Förster mechanism is considered. If formula (1) is substituted into formula (3), τ can be eliminated. Thus, in the Förster mechanism, the energy transfer efficiency ϕ ET does not depend on the lifetime τ of the excited state of the first material. Furthermore, it can be stated that a high energy transfer efficiency ϕ ET is obtained when the luminescence quantum yield ϕ (the fluorescence quantum yield in the energy transfer from a singlet excited state, and the phosphorescence quantum yield in the energy transfer from a triplet excited state) is high.

[0091] Furthermore, it is preferable that the emission spectrum (the fluorescence spectrum upon energy transfer from a singlet excited state, and the phosphorescence spectrum upon energy transfer from a triplet excited state) of the first material largely overlaps with the absorption spectrum (absorption corresponding to the transition from the singlet ground state to the singlet excited state) of the second material. Furthermore, it is preferable that the molar absorption coefficient of the second material is also high. That is, the emission spectrum of the first material overlaps with the absorption band of the second material located on the longest wavelength side. Since the direct transition from the singlet ground state to the triplet excited state of the second material is forbidden, the molar absorption coefficient of the second material in the triplet excited state is negligible.Therefore, a process of energy transfer from an excited state of the first material to a triplet excited state of the second material by the Förster mechanism is negligible, and only a process of energy transfer to a singlet excited state of the second material is considered.

[0092] Next, energy transfer through the Dexter mechanism is considered. To determine the rate constant k h*→g To increase the energy transfer efficiency, according to formula (2), the emission spectrum (the fluorescence spectrum upon energy transfer from a singlet excited state, and the phosphorescence spectrum upon energy transfer from a triplet excited state) of the first material preferably overlaps largely with an absorption spectrum (absorption corresponding to the transition from a singlet ground state to a singlet excited state) of the second material. Accordingly, the energy transfer efficiency can be optimized by ensuring that the emission spectrum of the first material overlaps with the absorption band of the second material located on the longest wavelength side.

[0093] When formula (2) is inserted into formula (3), it becomes clear that the energy transfer efficiency ϕ ET in the Dexter mechanism depends on τ. In the Dexter mechanism, which is an energy transfer process based on electron exchange, energy transfer occurs from the triplet excited state of the first material to the triplet excited state of the second material, as does energy transfer from the singlet excited state of the first material to the singlet excited state of the second material.

[0094] In a manner similar to that of energy transfer from the first material to the second material, energy transfer by both the Förster mechanism and the Dexter mechanism also occurs in the energy transfer process from the exciplex to the fluorescent compound.

[0095] In the light-emitting element of one embodiment of the present invention, in which the second material is a fluorescent compound, the energy transfer efficiency to the triplet excited 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.

[0096] As described above, in the Förster mechanism, the energy transfer efficiency does not depend on the lifetime τ of the excited state of the first material. In contrast, the energy transfer efficiency in the Dexter mechanism depends on the excitation lifetime τ of the first material. To reduce the energy transfer efficiency in the Dexter mechanism, the excitation lifetime τ of the first material is preferably small.

[0097] In one embodiment of the present invention, an exciplex is used for the first material, and one of the compounds forming an exciplex is capable of converting triplet excitation energy into light emission. With the structure of one embodiment of the present invention, reverse intersystem crossing from the triplet excited state to the singlet excited state of an exciplex (first material) can be promoted, and the excitation lifetime τ of the triplet excited state of the exciplex (first material) can be short. Furthermore, the transition from the triplet excited state to the singlet ground state of the exciplex (first material) can be promoted, and the excitation lifetime τ of the triplet excited state of the exciplex (first material) can be short.As a result, the energy transfer efficiency from the triplet excited state of the exciplex (first material) to the triplet excited state of the fluorescent compound (second material) may be reduced in the Dexter mechanism.

[0098] As described above, a process of energy transfer from the excited state of the exciplex to the triplet excited state of the fluorescent compound (second material) by the Förster mechanism can be ignored. Thus, according to an embodiment of the present invention, in both the Förster mechanism and the Dexter mechanism, a process of energy transfer from the excited state of the exciplex to the triplet excited state of the fluorescent compound (second material) can be less likely to occur. As a result, deactivation of the triplet excitation energy at the light-emitting layer 130 can be suppressed, and a light-emitting element with high luminous efficiency can be provided.

[0099] In addition, the fluorescence lifetime of a thermally activated delayed fluorescent component in light emitted from the exciplex is preferably short, particularly preferably 10 ns or longer and 50 µs or shorter, more preferably 10 ns or longer and 20 µs or shorter, even more preferably 10 ns or longer and 10 µs or shorter.

[0100] The rate constant of the Förster mechanism is inversely proportional to the sixth power of the distance between the first material and the second material, and the rate constant of the Dexter mechanism is inversely proportional to the exponential function of the distance between the first material and the second material. Therefore, when the distance between the two molecules is approximately 1 nm or smaller, the Dexter mechanism is dominant, and when the distance is approximately 1 nm or more, the Förster mechanism is dominant. To reduce the energy transfer efficiency in the Dexter mechanism, the distance between the first material and the second material is preferably large, and in particular, 0.7 nm or more, preferably 0.9 nm or more, and more preferably 1 nm or more.In order to efficiently achieve energy transfer through the Förster mechanism, the distance between the first material and the second material is preferably 5 nm or less.

[0101] Thus, in one embodiment of the present invention, compound 133, which is a fluorescent compound, preferably comprises at least two alkyl groups, each having 2 or more carbon atoms. Alternatively, compound 133 preferably comprises at least two branched alkyl groups, each having 3 to 10 carbon atoms. Alternatively, compound 133 preferably comprises at least two cyclic hydrocarbon groups, each having 3 to 10 carbon atoms, or at least two bridged cyclic hydrocarbon groups, each having 3 to 10 carbon atoms. Furthermore, compound 133 preferably comprises a condensed aromatic hydrocarbon having 3 to 12 carbon atoms.

[0102] The proportion of a thermally activated, delayed fluorescent component in the light emitted by the exciplex is preferably high. In particular, the proportion of a thermally activated, delayed fluorescent component in the light emitted by the exciplex is preferably greater than or equal to 10%, more preferably greater than or equal to 30%, even more preferably greater than or equal to 50%. <material>

[0103] Next, components of a light-emitting element of an embodiment of the present invention will be described in detail below. <<Licht emittierende Schicht> >

[0104] Materials that can be used for the light-emitting layer 130 are described below.

[0105] As long as an exciplex can be formed, there is no particular limitation on compound 131 and compound 132; however, it is preferable that one of them has a function of transporting electrons and the other has a function of transporting holes.

[0106] When compound 132 has a hole transporting function, compound 132 preferably comprises a π-electron-rich heteroaromatic framework and / or an aromatic amine framework.

[0107] As the π-electron-rich heteroaromatic skeleton contained in compound 132, one or more of a furan skeleton, a thiophene skeleton, and a pyrrole skeleton are preferable due to their high stability and reliability. As the furan skeleton, a dibenzofuran skeleton is preferable. As the thiophene skeleton, a dibenzothiophene skeleton is preferable. Note that as the pyrrole skeleton, an indole skeleton, a carbazole skeleton, or a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton is preferable. Each of these skeletons may further have a substituent.

[0108] As the aromatic amine skeleton contained in compound 132, a tertiary amine not comprising an NH bond, particularly a triarylamine skeleton, is preferably used. As the aryl group of a triarylamine skeleton, a substituted or unsubstituted aryl group having 6 to 13 carbon atoms forming a ring is preferable, and examples thereof include a phenyl group, a naphthyl group, and a fluorenyl group.

[0109] A structure comprising a π-electron-rich heteroaromatic framework and an aromatic amine framework, which exhibits excellent hole-transport properties and is thus stable and highly reliable, is particularly preferable. An example of such a structure is a structure comprising a carbazole framework and an arylamine framework.

[0110] As examples of the above-described π-electron-rich heteroaromatic skeleton and the above-described aromatic amine skeleton, skeletons represented by the following general formulas (101) to (117) are given. Note that X in the general formulas (115) to (117) represents an oxygen atom or a sulfur atom.

[0111] In the case where compound 132 has an electron-transporting function, compound 132 preferably comprises a π-electron-deficient heteroaromatic skeleton. As the π-electron-deficient heteroaromatic skeleton, a pyridine skeleton, a diazine skeleton (a pyrimidine skeleton, a pyrazine skeleton, or a pyridazine skeleton), or a triazine skeleton is preferable; in particular, the diazine skeleton or the triazine skeleton is preferable due to its high stability and reliability.

[0112] As examples of the π-electron-deficient heteroaromatic framework described above, frameworks represented by the following general formulas (201) to (218) are given. Note that X in general formulas (209) to (211) represents an oxygen atom or a sulfur atom.

[0113] Alternatively, a compound can be used in which a framework with a hole-transporting property (e.g., a π-electron-rich heteroaromatic framework and / or an aromatic amine framework) and a framework with an electron-transporting property (e.g., a π-electron-poor heteroaromatic framework) are bonded directly or via an arylene group. Examples of the arylene group described above include a phenylene group, a biphenyldiyl group, a naphthalenediyl group, and a fluorenediyl group.

[0114] As examples of a bonding group that bonds the above framework having a hole transport property and the above framework having an electron transport property to each other, groups represented by the following general formulas (301) to (315) are given.

[0115] The above aromatic amine skeleton (e.g., the triarylamine skeleton), the above π-electron-rich heteroaromatic skeleton (e.g., a ring comprising the furan skeleton, the thiophene skeleton, or the pyrrole skeleton), the above π-electron-deficient heteroaromatic skeleton (e.g., a ring comprising the diazine skeleton or the triazine skeleton), or the above general formulas (101) to (117), (201) to (218), and (301) to (315) may each have a substituent. An alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms can also be selected as the substituent. Specific examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like.Specific examples of a cycloalkyl group having 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like. Specific examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and the like. The above substituents may be bonded to each other to form a ring. For example, in the case where a carbon atom at the 9-position in a fluorenyl group has two phenyl groups as substituents, the phenyl groups are bonded to form a spirofluorene skeleton. Note that an unsubstituted group is advantageous in that it can be easily synthesized and is a cheap starting material.

[0116] Furthermore, Ar represents a single-bonded arylene group or an arylene group having 6 to 13 carbon atoms. The arylene group may contain one or more substituents, and the substituents may be bonded to each other to form a ring. For example, a carbon atom at the 9-position in a fluorenyl group has two phenyl groups as substituents, and the phenyl groups are bonded to each other to form a spirofluorene skeleton. Specific examples of the arylene group having 6 to 13 carbon atoms include a phenylene group, a naphthalenediyl group, a biphenyldiyl group, a fluorenediyl group, and the like. In the case where the arylene group has a substituent, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms can also be selected as the substituent.Specific examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group having 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like. Specific examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and the like.

[0117] For example, the arylene group represented by Ar can be represented by groups represented by the following structural formulas (Ar-1) to (Ar-18). Note that the group that can be used as Ar is not limited to these.

[0118] Furthermore, R 1 and R 2 each independently represents hydrogen, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 13 carbon atoms. Specific examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group having 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like. Specific examples of the aryl group having 6 to 13 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, and the like.The above aryl group or phenyl group may include one or more substituents, and the substituents may be bonded to each other to form a ring. An alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms can also be selected as the substituent. Specific examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, and the like. Specific examples of a cycloalkyl group having 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like.Specific examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group, and the like.

[0119] For example, groups represented by the following structural formulas (R-1) to (R-29) can be used as an alkyl group or aryl group represented by R 1 and R 2 It should be noted that the groups that can be used as alkyl groups or aryl groups are not limited to these.

[0120] As a substituent present in the general formulas (101) to (117), (201) to (218), (301) to (315), Ar, R 1 and R 2 For example, the alkyl group or the aryl group represented by the above structural formulas (R-1) to (R-24) can be used. Note that the group that can be used as the alkyl group or the aryl group is not limited to these.

[0121] For example, any of the following hole transport materials and electron transport materials can be used as compound 132.

[0122] A material that has a property of transporting more holes than electrons can be used as a hole transport material, whereby a material with a hole mobility of 1 × 10 -6 cm 2 / Vs or higher is preferable. In particular, an aromatic amine, a carbazole derivative, or the like can be used. Furthermore, the hole-transporting material can be a high-molecular compound.

[0123] Examples of the aromatic amine compound having a high hole-transporting property 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), 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B) and the like.

[0124] Specific examples of the carbazole derivatives include 3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA2), 3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole (abbreviation: PCzTPN2), 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), 3-[N-(1-Naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1) and the like.

[0125] Other examples of the carbazole derivatives include 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), 1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene and the like.

[0126] Examples of the material with excellent hole transport property include aromatic amine compounds such as: B. 4,4'-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-Bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4',4"-Tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), 4,4',4"-Tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1-TNATA), 4,4',4"-Tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4',4"-Tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: m-MTDATA), 4,4'-Bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-Phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-Phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), N-(9,9-Dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine (abbreviation: DFLADFL), N-(9,9-Dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine (abbreviation: DPNF), 2-[N-(4-Diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPASF), 4-Phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-Diphenyl-4"-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-Naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-Di(1-naphthyl)-4"-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 4-Phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl)amine (abbreviation: PCA1BP), N,N'-bis(9-phenylcarbazol-3-yl)-N,N'-diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N,N',N"-triphenyl-N,N',N"-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine (abbreviation: PCA3B), N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine (abbreviation: PCBiF), N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), 9,9-Dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), N-Phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF), 2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), 2,7-Bis[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPA2SF), N-[4-(9H-Carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline (abbreviation: YGA1BP) and N,N'-Bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F). Other examples include amine compounds, carbazole compounds, thiophene compounds, furan compounds, fluorene compounds, triphenylene compounds, phenanthrene compounds, and the like, such as 3-[4-(1-naphthyl)phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 3-[4-(9-phenanthryl)phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II), 4,4',4"-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV) and 4-[3-(Triphenylen-2-yl)phenyl]dibenzothiophene (abbreviation: mDBTPTp-II). The substances described here are mainly substances with a hole mobility of 1 × 10, -6 cm 2 / Vs or higher. Note that in addition to these substances, any substance that has the property of transporting more holes than electrons can be used.

[0127] A material that has a property of transporting more electrons than holes can be used as an electron transport material, whereby a material with an electron mobility of 1 × 10 -6 cm 2 / Vs or higher is preferable. A zinc- or aluminum-containing metal complex, a π-electron-deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound, or the like can be used as the material that readily accepts electrons (the material having an electron-transport property). As the metal complex, a metal complex having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand can be used. As the π-electron-deficient heteroaromatic compound, an oxadiazole derivative, a triazole derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, a triazine derivative, or the like can be used.

[0128] Examples include metal complexes having a quinoline skeleton or a benzoquinoline skeleton, such as tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), and the like. A metal complex having an oxazole-based or thiazole-based ligand, such as tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Alq3), bis(10-hydroxybenzo[h]quinolinolato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), and the like. B. Bis[2-(2-benzoxazolyl)phenolate]zinc(II) (abbreviation: ZnPBO) or bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ) can be used alternatively. In addition to such metal complexes, any of the following materials can be used: heterocyclic compounds, such as2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-Bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 3-(4-Biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 2,2',2"-(1,3,5-Benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(Dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), bathophenanthroline (abbreviation: BPhen), bathocuproine (abbreviation: BCP) and 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen); heterocyclic compounds with a diazine skeleton, such as2-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(Dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-Carbazol-9-yl)biphenyl-3-yl]dibenzo[fh]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4-(3,6-Diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), 6-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II) and 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm); heterocyclic compounds with a triazine skeleton, such as B. 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn); heterocyclic compounds with a pyridine skeleton, such as3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy) and 1,3,5-tris[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB); and heteroaromatic compounds such as 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs). A high-molecular compound such as B. Poly(2,5-pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py) or poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)] (abbreviation: PF-BPy) can also be used as an alternative. A high-molecular compound, such as Poly(2,5-pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), or poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)] (abbreviation: PF-BPy) can also be used as an alternative. The substances described here are primarily those with an electron mobility of 1 × 10 -6 cm 2 / Vs or higher. It should be noted that other substances can also be used as long as their electron transport properties are higher than their hole transport properties.

[0129] Compound 131 preferably has a function of converting triplet excitation energy into light emission. Note that when compound 131 contains a heavy atom, intersystem crossing between a singlet state and a triplet state is promoted by spin-orbit interaction (an interaction between spin angular momentum and orbital angular momentum of an electron), and a transition between a singlet ground state and a triplet excited state of compound 131 is permitted. Consequently, the light yield and absorption probability related to the transition between the singlet ground state and the triplet excited state of compound 131 can be increased. Accordingly, compound 131 preferably contains a metal element having a large spin-orbit interaction, particularly a transition metal element.In particular, a platinum group element (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) or platinum (Pt)), in particular iridium, is preferably included, since it can increase the transition probability concerning the direct transition between a singlet ground state and a triplet excited state.

[0130] As compound 131 (phosphorescent compound), an iridium-, rhodium-, or platinum-based organometallic complex or metal complex, or a platinum or organoiridium complex containing a porphyrin ligand can be used. Particularly, an organoiridium complex such as an iridium-based ortho-metalated complex is preferred. As the ortho-metalated ligand, a 4H-triazole ligand, a 1H-triazole ligand, an imidazole ligand, a pyridine ligand, a pyrimidine ligand, a pyrazine ligand, an isoquinoline ligand, or the like can be used. Here, compound 131 (phosphorescent compound) exhibits an absorption band of a triplet MLCT (metal-to-ligand charge transfer) transition.

[0131] Examples of the substance exhibiting an emission peak in the blue or green wavelength range include organometallic iridium complexes having a 4H-triazole skeleton, such as: B. Tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-ĸN2]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 framework, such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(Mptz1-mp)3) and tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Prptz1-Me)3); organometallic iridium complexes with an imidazole framework, such asfac-Tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: Ir(iPrpmi)3) and tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: Ir(dmpimpt-Me)3); and organometallic iridium complexes in which a phenylpyridine derivative with an electron-withdrawing group is a ligand, such as bis[2-(4',6'-difluorophenyl)pyridinato-N,C. 2 ']iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: Flr6), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2 ']iridium(III)picolinate (abbreviation: Flrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C 2 '}iridium(III)picolinate (abbreviation: Ir(CF3ppy)2(pic)) and bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2 [Iridium(III) acetylacetonate (abbreviation: Flr(acac)). Among the above-mentioned materials, organometallic iridium complexes comprising a five-membered nitrogen-containing heterocyclic framework, such as a 4H-triazole framework, a 1H-triazole framework, or an imidazole framework, exhibit high triplet excitation energy, reliability, and light yield and are therefore particularly preferred.

[0132] Examples of the substance that exhibits an emission peak in the green or yellow wavelength range include organometallic iridium complexes with a pyrimidine skeleton, such asTris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)3), Tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm)3), (Acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: Ir(mppm)2(acac)), (Acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm)2(acac)), (Acetylacetonato)bis[4-(2-norbornyl)-6-phenylpyrimidinato]iridium(III) (endo and exo mixture) (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-ĸN3]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 framework, such as(Acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-Me)2(acac)) and (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-iPr)2(acac)); organometallic iridium complexes with a pyridine framework, such as tris(2-phenylpyridinato-N,C 2 )iridium(III) (abbreviation: Ir(ppy)3), bis(2-phenylpyridinato-N,C 2 )iridium(III)acetylacetonate (abbreviation: Ir(ppy)2(acac)), bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation: Ir(bzq)2(acac)), tris(benzo[h]quinolinato)iridium(III) (abbreviation: Ir(bzq)3), tris(2-phenylquinolinato-N,C 2 )iridium(III) (abbreviation: Ir(pq)3) and bis(2-phenylquinolinato-N,C 2 )iridium(III)acetylacetonate (abbreviation: Ir(pq)2(acac)); organometallic iridium complexes, such as bis(2,4-diphenyl-1,3-oxazolato-N,C 2 )iridium(III)acetylacetonate (abbreviation: Ir(dpo)2(acac)), bis {2-[4'-(perfluorophenyl)phenyl]pyridinato-N,C 2 '}iridium(III)acetylacetonate (abbreviation: Ir(p-PF-ph)2(acac)) and bis(2-phenylbenzothiazolato-N,C 2' iridium(III) acetylacetonate (abbreviation: Ir(bt)2(acac)); and a rare earth metal complex such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: Tb(acac)3(Phen)). Among the above-mentioned materials, the organometallic iridium complexes with a pyrimidine framework exhibit remarkably high reliability and luminous efficacy and are therefore particularly preferred.

[0133] Examples of the substance exhibiting an emission peak in the yellow or red wavelength range include organometallic iridium complexes having a pyrimidine skeleton, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: Ir(5mdppm)2(dibm)), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(5mdppm)2(dpm)) and bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(d1npm)2(dpm)); organometallic iridium complexes having a pyrazine skeleton, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: Ir(5mdppm)2(dpm)). B. (Acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: Ir(tppr)2(acac)), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr)2(dpm)) and (Acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: Ir(Fdpq)2(acac)); organometallic iridium complexes with a pyridine framework, such as tris(1-phenylisoquinolinato-N,C 2 ')iridium(III) (abbreviation: Ir(piq)3) and bis(1-phenylisoquinolinato-N,C 2' )iridium(III) acetylacetonate (abbreviation: Ir(piq)2(acac)); a platinum complex, such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviation: PtOEP); and rare earth metal complexes, such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: Eu(DBM)3(Phen)) and tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: Eu(TTA)3(Phen)). Among the materials listed above, organometallic iridium complexes with a pyrimidine framework exhibit remarkably high reliability and luminous efficacy and are therefore particularly preferred. Furthermore, organometallic iridium complexes with a pyrazine framework can provide red light emission with favorable chromaticity.

[0134] Furthermore, a fluorescent compound is preferably used for the compound 133 in the light-emitting layer 130. The fluorescent compound is preferably, but is not limited to, an anthracene derivative, a tetracene derivative, a chrysene derivative, a phenanthrene derivative, a pyrene derivative, a perylene derivative, a stilbene derivative, an acridone derivative, a coumarin derivative, a phenoxazine derivative, a phenothiazine derivative, or the like.

[0135] The examples include 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-Bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-bis(4-tert-butylphenyl)pyrene-1,6-diamine (abbreviation: 1,6tBu-FLPAPrn), N,N'-Diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-3,8-dicyclohexylpyrene-1,6-diamine (abbreviation: ch-1,6FLPAPrn), N,N'-Bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-Carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-Tetra(tert-butyl)perylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N"-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA), N,9-Diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-Diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N',N',N",N",N"',N"'-Octaphenyldibenzo[g,p]chrysen-2,7,10,15-tetraamine (abbreviation: DBC1), Coumarin 30, N-(9,10-Diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), N-[9,10-Bis(1,1'-Biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), N-(9,10-Diphenyl-2-anthryl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis(1,1'-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracene-9-amine (abbreviation: DPhAPhA), coumarin 6, coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (abbreviation: TBRb), Nile Red, 5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(Dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-Methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]cehinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N',N'-Tetrakis(4-methylphenyl)tetracen-5,11-diamine (abbreviation: p-mPhTD), 7,14-Diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-Isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]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}propanedinitrile (abbreviation: DCJTB), 2-(2,6-Bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-Bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), 5,10,15,20-Tetraphenylbisbenzo[5,6]indeno[1,2,3-cd:1',2',3'-Im]perylene and the like.

[0136] Preferably, compound 131, compound 132, and compound 133 are selected such that the emission peak of the exciplex formed by organic compound 131 and compound 132 overlaps with an absorption band on the longest wavelength side (low energy side) of compound 133 serving as the light-emitting material. This can provide a light-emitting element with drastically improved emission efficiency.

[0137] The light-emitting layer 130 may have a structure in which two or more layers are stacked. For example, in the case where the light-emitting layer 130 is formed by stacking a first light-emitting layer and a second light-emitting layer in this order from the hole-transport layer side, the first light-emitting layer is formed using a substance having a hole-transport property as a host material, and the second light-emitting layer is formed using a substance having an electron-transport property as a host material.

[0138] The light-emitting layer 130 may contain another material (a compound 134) in addition to the compounds 131, 132, and 133. In this case, in order for the compound 131 and the compound 132 to efficiently form an exciplex, the following preferably applies: The HOMO level of one of the compound 131 and the compound 132 is the highest among the materials in the light-emitting layer 130, and the LUMO level of the other is the lowest among the materials in the light-emitting layer 130.That is, the HOMO level of one of Compound 131 and Compound 132 is preferably higher than the HOMO level of the other of Compound 131 and Compound 132 and higher than the HOMO level of Compound 134, and the LUMO level of the other of Compound 131 and Compound 132 is preferably lower than the LUMO level of one of Compound 131 and Compound 132 and lower than the LUMO level of Compound 134. With such energy level correlation, a reaction to form an exciplex by Compound 132 and Compound 134 can be inhibited.

[0139] For example, in the case where 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 the HOMO level of compound 132 and the HOMO level of compound 134, and the LUMO level of compound 132 is preferably lower than the LUMO level of compound 131 and the LUMO level of compound 134. In this case, the LUMO level of compound 134 may be higher or lower than the LUMO level of compound 131. Furthermore, the HOMO level of compound 134 may be higher or lower than the HOMO level of compound 132.

[0140] Alternatively, compound 131 may have an electron-transport property, and compound 132 may have a hole-transport property. In this case, the HOMO level of compound 132 is preferably higher than the HOMO level of compound 131 and the HOMO level of compound 134, and the LUMO level of compound 131 is preferably lower than the LUMO level of compound 132 and the LUMO level of compound 134. In this case, the LUMO level of compound 134 may be higher or lower than the LUMO level of compound 132. Furthermore, the HOMO level of compound 134 may be higher or lower than the HOMO level of compound 131.

[0141] Although there is no particular limitation on a material (the compound 134) that can be used in the light-emitting layer 130, for example, any of the following materials can be used: metal complexes such as: B. Tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO) and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ); heterocyclic compounds, such as B. 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 2,2',2"-(1,3,5-Benzenetriyl)-tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), bathophenanthroline (abbreviation: BPhen), bathocuproine (abbreviation: BCP) and 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11); and aromatic amine compounds, such as. B. 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), and 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB). Additionally, condensed polycyclic aromatic compounds, such as B. Anthracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives and dibenzo[g,p]chrysene derivatives, and specific examples include 9,10-diphenylanthracene (abbreviation: DPAnth), N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine (abbreviation: DPhPA),4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), N,9-Diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine (abbreviation: PCAPBA), N,9-diphenyl-N-(9,10-diphenyl-2-anthryl)-9H-carbazol-3-amine (abbreviation: 2PCAPA), 6,12-Dimethoxy-5,11-diphenylchrysene, N,N,N',N',N" ,N",N"',N "-Octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: DPCzPA), 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 9,9'-bianthryl (abbreviation: BANT), 9,9'-(Stilbene-3,3'-diyl)diphenanthrene (abbreviation: DPNS), 9,9'-(Stilbene-4,4'-diyl)diphenanthrene (abbreviation: DPNS2), 1,3,5-Tri(1-pyrenyl)benzene (abbreviation: TPB3) and the like. One or more substances with a larger energy gap than compound 131 and compound 132 are selected from these substances and known substances. <<Paar von Elektroden> >

[0142] The electrode 101 and the electrode 102 have functions of injecting holes and electrons into the light-emitting layer 130. The electrodes 101 and 102 can be formed using a metal, an alloy, a conductive compound, a mixture, or a layered arrangement of these or the like. A typical example of the metal is aluminum (Al); in addition, a transition metal such as silver (Ag), tungsten, chromium, molybdenum, copper, or titanium; an alkali metal such as lithium (Li) or cesium; or a Group 2 metal such as calcium or magnesium (Mg) can also be used. As the transition metal, a rare earth metal such as ytterbium (Yb) can be used. An alloy containing any of the above metals can be used; examples include MgAg and AlLi. Examples of the conductive compound include metal oxides such asIndium tin oxide (hereinafter referred to as ITO), indium tin oxide containing silicon or silicon oxide (ITSO), indium zinc oxide, indium oxide containing tungsten and zinc, and the like. It is also possible to use an inorganic carbon-based material such as graphene as the conductive compound. As described above, the electrode 101 and / or the electrode 102 may be formed by stacking two or more of these materials.

[0143] Light emitted from the light-emitting layer 130 is extracted via the electrode 101 and / or the electrode 102. Accordingly, at least one of the electrode 101 and the electrode 102 transmits visible light. As the conductive material that transmits light, a conductive material whose visible light transmittance is higher than or equal to 40% and lower than or equal to 100%, preferably higher than or equal to 60% and lower than or equal to 100%, and whose specific resistance is lower than or equal to 1 × 10 -2 Ω cm. The electrode on the light extraction side can be formed using a conductive material with light transmitting and light reflecting functions. As the conductive material, a conductive material whose visible light reflectance is higher than or equal to 20% and lower than or equal to 80%, preferably higher than or equal to 40% and lower than or equal to 70%, and whose resistivity is lower than or equal to 1 × 10 -2 Ω cm. In the case where the electrode through which light is taken out is formed using a material with low light transmittance, such as a metal or an alloy, the electrode 101 and / or the electrode 102 are / is formed to a thickness thin enough to transmit visible light (e.g., a thickness of 1 nm to 10 nm).

[0144] In this specification and the like, a material that transmits visible light and has conductivity is used as the light-transmitting electrode. Examples of the material include, in addition to the above-described oxide conductor, of which ITO is a typical example, an oxide semiconductor layer and an organic conductive layer containing an organic substance. Examples of the organic conductive layer containing an organic substance include a layer containing a composite material in which an organic compound and an electron donor (donor material) are mixed, and a layer containing a composite material in which an organic compound and an electron acceptor (acceptor material) are mixed. The specific resistance of the transparent conductive layer is preferably less than or equal to 1 × 10 5 Ω·cm, more preferably less than or equal to 1 × 10 4 Ω·cm.

[0145] As a method for forming the electrode 101 and the electrode 102, a sputtering method, an evaporation method, a printing method, a coating method, a molecular beam epitaxy (MBE) method, a CVD method, a pulse laser deposition method, an atomic layer deposition (ALD) method, or the like can be used as needed. < <lochinjektionsschicht>>

[0146] The hole-injection layer 111 has a function of reducing a barrier to hole injection from one of the pair of electrodes (the electrode 101 or the electrode 102) to promote hole injection, and is formed using, for example, a transition metal oxide, a phthalocyanine derivative, or an aromatic amine. Examples of transition metal oxides include molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide, or the like. Examples of phthalocyanine derivatives include phthalocyanine, a metal phthalocyanine, or the like. Examples of aromatic amines include a benzidine derivative, a phenylenediamine derivative, or the like. It is also possible to use a high-molecular compound such as polythiophene or polyaniline. A typical example is poly(ethylenedioxythiophene) / poly(styrenesulfonic acid), which is a self-doped polythiophene.

[0147] As the hole-injection layer 111, a layer containing a composite material of a hole-transporting material and a material having a property of accepting electrons from the hole-transporting material can also be used. Alternatively, a layer arrangement of a layer containing a material having a property of accepting electrons and a layer containing a hole-transporting material can also be used. In a stable state or in the presence of an electric field, electric charges can be transferred between these materials. As examples of the material having a property of accepting electrons, organic acceptors such as a quinodimethane derivative, a chloranil derivative, and a hexaazatriphenylene derivative can be given. A specific example is a compound having an electron-withdrawing group (a halogen group or a cyano group), such as7,7,8,8-Tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, or 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN). Alternatively, a transition metal oxide, such as an oxide of a metal from Group 4 to Group 8, can also be used. In particular, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, or the like can be used. In particular, molybdenum oxide is preferred because it is stable in air, has low hygroscopic properties, and is easy to handle.

[0148] A material that has a property of transporting more holes than electrons can be used as a hole transport material, whereby a material with a hole mobility of 1 × 10 -6 cm 2 / Vs or higher is preferable. Specifically, any of the above aromatic amines, the above carbazole derivatives, the above aromatic hydrocarbons, the above stilbene derivatives, and the like described as examples of the hole-transport material that can be used in the light-emitting layer 130 can be used. Furthermore, the hole-transport material can be a high-molecular compound.

[0149] Examples of the aromatic hydrocarbon are 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9,10-di(1-naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene (abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene (abbreviation: DMNA), 2-tert-butyl-9, 10-bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene, 2,3,6,7-Tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9'-bianthryl, 10,10'-diphenyl-9,9'-bianthryl, 10,10'-bis(2-phenylphenyl)-9,9'-bianthryl, 10,10'-Bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'bianthryl, anthracene, tetracene, rubrene, perylene, 2,5,8,11-Tetra(tert-butyl)perylene and the like. Other examples include pentacene, coronene, and the like.The aromatic hydrocarbon, which has a hole mobility of 1 × 10. -6 cm 2 / Vs or higher and 14 to 42 carbon atoms is particularly preferred.

[0150] The aromatic hydrocarbon may have a vinyl skeleton. Examples of aromatic hydrocarbons with a vinyl group are 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi), 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA), and the like.

[0151] Further examples include high molecular weight compounds such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N-[4-(4-diphenylamino)phenyl]phenyl-N'phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA) and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: poly-TPD). < <lochtransportschicht>>

[0152] The hole-transport layer 112 is a layer containing a hole-transport material and can be formed using any of the materials given as examples of the material of the hole-injection layer 111. In order for the hole-transport layer 112 to have a function of transporting holes injected into the hole-injection layer 111 to the light-emitting layer 130, the HOMO level of the hole-transport layer 112 is preferably equal to or close to the HOMO level of the hole-injection layer 111.

[0153] 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 cm 2 / Vs or higher is used as a hole-transporting material. Note that, in addition to the above substances, any substance can be used as long as its hole-transporting property is higher than its electron-transporting property. The layer containing a substance with excellent hole-transporting property is not limited to a single layer, and two or more layers containing the above substances can be stacked. < <elektronentransportschicht>>

[0154] The electron-transport layer 118 has a function of transporting electrons injected from the other electrode of the pair of electrodes (the electrode 101 or the electrode 102) via the electron-injection layer 119 to the light-emitting layer 130. A material having a property of transporting more electrons than holes can be used as the electron-transport material, and a material having an electron mobility of 1 × 10 -6 cm 2 / Vs or higher is preferable. As a compound that readily accepts electrons (as a material with an electron-transport property), for example, a π-electron-deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound, a metal complex, or the like can be used. Specifically, a metal complex having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand can be cited, which have been described as electron-transport materials that can be used in the light-emitting layer 130. In addition, an oxadiazole derivative, a triazole derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, and the like can be cited. A substance having an electron mobility of 1 × 10 -6 cm 2 / Vs or higher is preferred. Note that instead of 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 may be a stacked arrangement of two or more layers containing the aforementioned substances.

[0155] Between the electron-transport layer 118 and the light-emitting layer 130, a layer that controls the transfer of electron carriers can be provided. The layer that controls the transfer of electron carriers is formed by adding a small amount of a substance with a high electron-capturing property to a material with a high electron-transporting property described above, and the layer can control the carrier balance by suppressing the transfer of electron carriers. Such a structure is very effective in preventing a problem (such as a shortening of the element's lifetime) caused when electrons pass through the light-emitting layer. < <elektroneninjektionsschicht>>

[0156] The electron injection layer 119 has a function of reducing a barrier to electron injection from the electrode 102 to promote electron injection, and can be formed using, for example, a Group 1 metal or a Group 2 metal, or an oxide, a halide, or a carbonate of one of the metals. Alternatively, a composite material containing an electron-transport material (described above) and a material having a property of donating electrons to the electron-transport material can also be used. As the material having a property of donating electrons, a Group 1 metal, a Group 2 metal, an oxide of one of these metals, or the like can be mentioned. Specifically, an alkali metal, an alkaline earth metal, or a compound thereof, such as hydroxide, can be used.Lithium fluoride (LiF), sodium fluoride (NaF), cesium fluoride (CsF), calcium fluoride (CaF2) or lithium oxide (LiO). x ), may be used. Alternatively, a rare earth metal compound such as erbium fluoride (ErF3) may also be used. An electride may also be used for the electron-injection layer 119. Examples of the electride include a substance in which electrons are added at a high concentration to calcium oxide-alumina. The electron-injection layer 119 may be formed using the substance that can be used for the electron-transport layer 118.

[0157] A composite material in which an organic compound and an electron donor (donor) are mixed can also be used for the electron-injection layer 119. Such a composite material has high electron injection and electron transport properties because electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material that can excellently transport the generated electrons. Specifically, for example, the substances listed above (e.g., metal complexes and heteroaromatic compounds) can be used for forming the electron-transport layer 118. As the electron donor, a substance that exhibits an electron-donating property with respect to the organic compound can be used.In particular, an alkali metal, an alkaline earth metal, and a rare earth metal are preferred, and lithium, cesium, magnesium, calcium, erbium, ytterbium, and the like can be mentioned. Furthermore, an alkali metal oxide or an alkaline earth metal oxide is preferred, and lithium oxide, calcium oxide, barium oxide, and the like can be mentioned. A Lewis base such as magnesium oxide can also be used. An organic compound such as tetrathiafulvalene (abbreviation: TTF) can also be used.

[0158] Note that the light-emitting layer, hole-injection layer, hole-transport layer, electron-transport layer, and electron-injection layer described above can each be formed by an evaporation method (including a vacuum evaporation method), an inkjet method, a coating method, a jet printing method, a gravure printing method, or the like. In addition to the above-mentioned materials, an inorganic compound such as a quantum dot or a high-molecular compound (e.g., an oligomer, a dendrimer, and a polymer) can be used in the light-emitting layer, the hole-injection layer, the hole-transport layer, the electron-transport layer, and the electron-injection layer.

[0159] The quantum dot can be, for example, a gelatinous quantum dot, an alloyed quantum dot, a core-shell quantum dot, or a core quantum dot. The quantum dot containing elements belonging to groups 2 and 16, elements belonging to groups 13 and 15, elements belonging to groups 13 and 17, elements belonging to groups 11 and 17, or elements belonging to groups 14 and 15 can be used. Alternatively, the quantum dot containing an element such as cadmium (Cd), selenium (Se), zinc (Zn), sulfur (S), phosphorus (P), indium (In), tellurium (Te), lead (Pb), gallium (Ga), arsenic (As), or aluminum (Al) can be used.

[0160] An example of the liquid medium used for the wet process includes an organic solvent of ketones such as methyl ethyl ketone and cyclohexanone; fatty acid esters such as ethyl acetate; halogenated hydrocarbons such as dichlorobenzene; aromatic hydrocarbons such as toluene, xylene, mesitylene, and cyclohexylbenzene; aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane; dimethylformamide (DMF); dimethyl sulfoxide (DMSO); or the like.

[0161] Examples of the high molecular compound that can be used for the light-emitting layer include a phenylenevinylene (PPV) derivative such as poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (abbreviation: MEH-PPV) or poly(2,5-dioctyl-1,4-phenylenevinylene); a polyfluorene derivative such as poly(ethylenediamine dimethyl ether); B. Poly(9,9-din-octylfluorenyl-2,7-diyl) (abbreviation: PF8), poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazole-4,8-diyl)] (abbreviation: F8BT), poly(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(2,2'-bithiophene-5,5'-diyl)] (abbreviation: F8T2), poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-(9,10-anthracene)] or poly[(9,9-dihexylfluorene-2,7-diyl)-alt-(2,5-dimethyl-1,4-phenylene)]; a polyalkylthiophene (PAT) derivative, such as B. Poly(3-hexylthiophene-2,5-diyl) (abbreviation: P3HT), and a polyphenylene derivative.These high-molecular-weight compounds, such as poly(9-vinylcarbazole) (abbreviation: PVK), poly(2-vinylnaphthalene), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (abbreviation: PTAA), or the like, can be doped with a light-emitting compound and used for the light-emitting layer. Any of the light-emitting compounds described above can be used as the light-emitting compound. < <substrat>>

[0162] A light-emitting element of one embodiment of the present invention can be formed over a substrate made of glass, plastic, or the like. As one way to stack layers over the substrate, layers can be arranged sequentially from the electrode 101 side or from the electrode 102 side.

[0163] For the substrate over which the light-emitting element of one embodiment of the present invention can be formed, for example, glass, quartz, plastic, or the like can be used. A flexible substrate can alternatively be used. The flexible substrate is, for example, a substrate that can be bent, such as a plastic substrate made of polycarbonate or polyarylate. Alternatively, a film, an inorganic film formed by vapor deposition, or the like can be used. Another material can be used as long as the substrate serves as a support in a manufacturing process of the light-emitting element or the optical element. Another material having a function of protecting the light-emitting element or the optical element can be used.

[0164] For example, in this specification and the like, a light-emitting element can be formed using various substrates. The type of substrate is not particularly limited. Examples of the substrate include a semiconductor substrate (e.g., a single-crystal substrate or a silicon substrate), an SOI substrate, a glass substrate, a quartz substrate, a plastic substrate, a metal substrate, a stainless steel substrate, a substrate containing a stainless steel foil, a tungsten substrate, a substrate containing a tungsten foil, a flexible substrate, an attachment film, a cellulose nanofiber (CFN) and paper containing a fiber material, a base material film, and the like. As an example of a glass substrate, a barium borosilicate glass substrate, an aluminum borosilicate glass substrate, a soda-lime glass substrate, or the like can be given.Examples of the flexible substrate, the fixing film, the base material film, and the like include substrates made of plastics, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). Another example is a resin such as acrylic. Alternatively, polypropylene, polyester, polyvinyl fluoride, polyvinyl chloride, or the like may be used. Further alternatives include polyamide, polyimide, aramid, epoxy, a vapor-deposited inorganic film, paper, or the like.

[0165] Alternatively, a flexible substrate may be used as the substrate, and a transistor or a light-emitting element may be provided directly above the flexible substrate. As a further alternative, a separation layer may be provided between the substrate and the light-emitting element. The separation layer may be used when a part of a light-emitting element or an entire light-emitting element formed above the separation layer is separated from the substrate and transferred to another substrate. In such a case, the light-emitting element may be transferred to a substrate with low heat resistance or to a flexible substrate.For the above separation layer, for example, a layered structure comprising inorganic films, namely a tungsten film and a silicon oxide film, or a structure in which a resin film of polyimide or the like is formed over a substrate can be used.

[0166] In other words, after the light-emitting element is formed using a substrate, the light-emitting element can be transferred to another substrate. Examples of a substrate to which the light-emitting element is transferred include, in addition to the substrates described above, a cellophane substrate, a stone substrate, a wood substrate, a fabric substrate (including a natural fiber (e.g., silk, cotton, or hemp), a synthetic fiber (e.g., nylon, polyurethane, or polyester), a regenerated fiber (e.g., acetate, cupro, viscose, or regenerated polyester), or the like), a leather substrate, and a rubber substrate. When such a substrate is used, a light-emitting element with high durability, high heat resistance, reduced weight, or reduced thickness can be formed.

[0167] The light-emitting element 150 can, for example, be formed over an electrode electrically connected to a field-effect transistor (FET) formed over one of the substrates described above. In this case, an active matrix display device can be fabricated in which the FET controls the operation of the light-emitting element.

[0168] The structure described above in this embodiment may be used in a suitable combination with any of the structures described in the other embodiments. (Embodiment 2)

[0169] In this embodiment, light-emitting elements having structures different from those described in Embodiment 1 and light-emitting mechanisms of the light-emitting elements will be described below with reference to Fig. 4. In Fig. 4, in some cases, a section with a similar function to that in Fig. 1 by the same hatching pattern as in Fig. 1 and are not specifically identified by a reference symbol. In addition, the same reference symbols are used for sections with similar functions, and a detailed description of the sections is omitted in some cases. <Strukturbeispiel eines Licht emittierenden Elements>

[0170] Fig. 4 is a schematic cross-sectional view of a light-emitting element 250.

[0171] The light-emitting element 250, which is in Fig. 4 comprises a plurality of light-emitting units (a light-emitting unit 106 and a light-emitting unit 108 in Fig. 4) between a pair of electrodes (the electrode 101 and the electrode 102). A light-emitting unit has the same structure as the EL layer 100 shown in Fig. 1. That is, the light-emitting element 150 shown in Fig. 1 includes one light-emitting unit, whereas the light-emitting element 250 includes a plurality of light-emitting units. Note that the electrode 101 serves as the anode and the electrode 102 serves as the cathode in the following description of the light-emitting element 250; however, the functions of the light-emitting element 250 may be interchanged.

[0172] In the light emitting element 250, which is in Fig. 4, the light-emitting unit 106 and the light-emitting unit 108 are arranged one above the other, and a charge generation layer 115 is provided between the light-emitting unit 106 and the light-emitting unit 108. It should be noted that the structures of the light-emitting unit 106 and the light-emitting unit 108 may be the same or different from each other. For example, the light-emitting unit 106 has a structure similar to that of the EL layer 100 shown in Fig. 1 is similar.

[0173] The light-emitting element 250 includes the light-emitting layer 130 and a light-emitting layer 140. The light-emitting unit 106 includes the hole-injection layer 111, the hole-transport layer 112, an electron-transport layer 113, and an electron-injection layer 114 adjacent to the light-emitting layer 130. The light-emitting unit 108 includes a hole-injection layer 116, a hole-transport layer 117, an electron-transport layer 118, and the electron-injection layer 119 adjacent to the light-emitting layer 140.

[0174] The charge generation layer 115 may have either a structure in which an acceptor substance, which is an electron acceptor, is added to a hole-transporting material, or a structure in which a donor substance, which is an electron donor, is added to an electron-transporting material. Alternatively, both of these structures may be arranged one above the other.

[0175] In the case where the charge generation layer 115 contains a composite material of an organic compound and an acceptor substance, the composite material that can be used for the hole injection layer 111 described in Embodiment 1 can be used for the composite material. As the organic compound, any of various compounds such as an aromatic amine compound, a carbazole compound, an aromatic hydrocarbon, and a high-molecular compound (such as an oligomer, a dendrimer, or a polymer) can be used. A substance with a hole mobility of 1 × 10 -6 cm 2 / Vs or higher is preferably used as the organic compound. Note that any other material can be used as long as it has a property of transporting more holes than electrons. Since the composite material of an organic compound and an acceptor substance has excellent charge injection and charge transport properties, low-voltage operation or low-current operation can be achieved. Note that when a surface of a light-emitting unit on the anode side is in contact with the charge generation layer 115, as in the light-emitting unit 108, the charge generation layer 115 can also serve as a hole injection layer or a hole transport layer of the light-emitting unit; therefore, a hole injection layer or a hole transport layer may not necessarily be included in the light-emitting unit.

[0176] The charge generation layer 115 may have a multilayer structure composed of a layer containing the composite material of an organic compound and an acceptor substance and a layer containing another material. For example, the charge generation layer 115 may be formed by combining a layer containing the composite material of an organic compound and an acceptor substance with a layer containing a compound selected from materials having an electron-donating property and a compound having a high electron-transporting property. Furthermore, the charge generation layer 115 may be formed by combining a layer containing the composite material of an organic compound and an acceptor substance with a layer containing a transparent conductive material.

[0177] The charge generation layer 115 provided between the light-emitting unit 106 and the light-emitting unit 108 may have any structure as long as electrons can be injected into the light-emitting unit on one side and holes can be injected into the light-emitting unit on the other side when a voltage is applied between the electrode 101 and the electrode 102. For example, Fig. 4 the charge generation layer 115 electrons into the light-emitting unit 106 and holes into the light-emitting unit 108 when a voltage is applied such that the potential of the electrode 101 is higher than that of the electrode 102.

[0178] Note that, in terms of light extraction efficiency, the charge generation layer 115 preferably has a visible light transmittance (specifically, it has a visible light transmittance higher than or equal to 40%). The charge generation layer 115 operates even if it has a lower conductivity than the pair of electrodes (the electrodes 101 and 102). In the case where the conductivity of the charge generation layer 115 is the same as that of the pair of electrodes, charge carriers generated in the charge generation layer 115 flow toward the film surface, so that light is emitted in some cases in a region where the electrode 101 and the electrode 102 do not overlap with each other.To suppress such a defect, the charge generation layer 115 is preferably formed using a material whose conductivity is lower than that of the pair of electrodes.

[0179] Note that forming the charge generation layer 115 using any of the above materials can suppress an increase in the driving voltage caused by the stacking of the light-emitting layers.

[0180] The light-emitting element, which comprises two light-emitting units, was designed using Fig. 4; however, a similar structure can also be applied to a light-emitting element in which three or more light-emitting units are stacked. By placing a plurality of light-emitting units separated by the charge generation layer between a pair of electrodes, just as in the light-emitting element 250, a light-emitting element capable of emitting light with high luminance while keeping the current density low and having a long lifetime can be provided. A light-emitting element with low power consumption can be provided.

[0181] If the structure of the EL layer 100 shown in Fig. 1 is used for at least one of the plurality of units, a light-emitting element with high luminous efficiency can be provided.

[0182] Preferably, the light-emitting layer 130 of the light-emitting unit 106 has the structure described in Embodiment 1, in which case the light-emitting element 250 has a high luminous efficiency.

[0183] It should be noted that the guest materials used in the light-emitting unit 106 and the light-emitting unit 108 may be the same or different from each other. In the case where the same guest material is used for the light-emitting unit 106 and the light-emitting unit 108, the light-emitting element 250 can have high emission luminance at a small current value, which is preferable. In the case where different guest materials are used for the light-emitting unit 106 and the light-emitting unit 108, the light-emitting element 250 can have multicolor light emission, which is preferable. In particular, the guest materials are preferably selected such that white light emission with high color rendering property or light emission of at least red, green, and blue can be obtained.

[0184] Note that the light-emitting units 106 and 108 and the charge generation layer 115 can be formed by an evaporation method (including a vacuum evaporation method), an inkjet method, a coating method, gravure printing, or the like.

[0185] It should be noted that the structure described in this embodiment may be appropriately combined with any of the structures described in the other embodiments. (Embodiment 3)

[0186] In this embodiment, examples of the light-emitting elements having structures different from those described in Embodiments 1 and 2 will be described below with reference to Fig. 5 and Fig. 6A and Fig. 6B. <Strukturbeispiel 1 eines Licht emittierenden Elements>

[0187] Fig. 5 is a cross-sectional view illustrating a light-emitting element of an embodiment of the present invention. In Fig. 5, in some cases, a section with a similar function to that in Fig. 1 by the same hatching pattern as in Fig. 1 and are not specifically identified by a reference symbol. In addition, the same reference symbols are used for sections with similar functions, and a detailed description of the sections is omitted in some cases.

[0188] A light-emitting element 260 in Fig. 5 may have a bottom-emission structure in which light is extracted via a substrate 200, or may have a top-emission structure in which light is extracted in the direction opposite to the substrate 200. However, an embodiment of the present invention is not limited to this structure, and a light-emitting element having a dual-emission structure in which light emitted from the light-emitting element is extracted in both the top and bottom directions of the substrate 200 may be employed.

[0189] In the case where the light-emitting element 260 has a bottom-emission structure, the electrode 101 preferably has a function of transmitting light, and the electrode 102 preferably has a function of reflecting light. Alternatively, in the case where the light-emitting element 260 has a top-emission structure, the electrode 101 preferably has a function of reflecting light, and the electrode 102 preferably has a function of transmitting light.

[0190] The light-emitting element 260 includes the electrode 101 and the electrode 102 above the substrate 200. Between the electrodes 101 and 102, a light-emitting layer 123B, a light-emitting layer 123G, and a light-emitting layer 123R are provided. The hole-injection layer 111, the hole-transport layer 112, the electron-transport layer 118, and the electron-injection layer 119 are also provided.

[0191] The electrode 101 can be formed using a plurality of conductive layers. In this case, a conductive layer with a function of reflecting light and a conductive layer with a function of transmitting light are preferably stacked.

[0192] For the electrode 101, a structure and materials similar to those of the electrode 101 or the electrode 102 described in Embodiment 1 can be used.

[0193] In Fig. 5, a partition wall 145 is provided between a region 221B, a region 221G, and a region 221R, which are arranged between the electrode 101 and the electrode 102. The partition wall 145 has an insulating property. The partition wall 145 covers end portions of the electrode 101 and has openings that overlap with the electrode. The partition wall 145 allows the electrode 101, which is provided above the substrate 200 in the regions, to be divided into island shapes.

[0194] Note that the light-emitting layer 123B and the light-emitting layer 123G may overlap each other in a region where they overlap with the partition wall 145. The light-emitting layer 123G and the light-emitting layer 123R may overlap each other in a region where they overlap with the partition wall 145. The light-emitting layer 123R and the light-emitting layer 123B may overlap each other in a region where they overlap with the partition wall 145.

[0195] The partition wall 145 has an insulating property and is formed using an inorganic or organic material. Examples of the inorganic material include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, and aluminum nitride. Examples of the organic material include photosensitive resin materials such as acrylic resin and polyimide resin.

[0196] Light-emitting layers 123R, 123G, and 123B preferably contain light-emitting materials with functions for emitting light of different colors. For example, when light-emitting layer 123R contains a light-emitting material with a function for emitting red light, region 221R emits red light. When light-emitting layer 123G contains a light-emitting material with a function for emitting green light, region 221G emits green light. When light-emitting layer 123B contains a light-emitting material with a function for emitting blue light, region 221B emits blue light. By using the light-emitting element 260 with such a structure in a pixel of a display device, a full-color display device can be manufactured. The thicknesses of the light-emitting layers may be the same or different from each other.

[0197] One or more of the light-emitting layer 123B, the light-emitting layer 123G, and the light-emitting layer 123R preferably has a structure similar to that of the light-emitting layer 130 described in Embodiment 1. In this case, a light-emitting element with high luminous efficiency can be manufactured.

[0198] One or more of the light-emitting layers 123B, 123G and 123R may comprise two or more layers arranged one above the other.

[0199] When at least one light-emitting layer includes the light-emitting layer described in Embodiment 1, and the light-emitting element 260 including the light-emitting layer is used in pixels of a display device, a display device with high luminous efficiency can be manufactured. The display device including the light-emitting element 260 can thus have reduced power consumption.

[0200] By providing a color filter over the electrode through which light is extracted, the color purity of the light-emitting element 260 can be improved. Consequently, the color purity of a display device including the light-emitting element 260 can be improved.

[0201] The reflection of external light from the light-emitting element 260 can be reduced by providing a polarizing plate over the electrode through which light is extracted. Consequently, the contrast ratio of a display device including the light-emitting element 260 can be improved.

[0202] For the other components of the light-emitting element 260, reference may be made to the components of the light-emitting element of Embodiment 1. <Strukturbeispiel 2 eines Licht emittierenden Elements>

[0203] Next, structural examples that differ from the light-emitting element used in Fig. 5 is shown, in the following using Fig. 6A and Fig. 6B.

[0204] Fig. 6A and Fig. 6B are cross-sectional views of a light-emitting element of an embodiment of the present invention. In Fig. 6A and Fig. 6B will in some cases be a section with a similar function to that in Fig. 5 by the same hatching pattern as in Fig. 5 and are not specifically designated with a reference symbol. In addition, the same reference symbols are used for sections with similar functions, and a detailed description of such sections is omitted in some cases.

[0205] Fig. 6A and Fig. 6B illustrate structural examples of a light-emitting element including the light-emitting layer between a pair of electrodes. A light-emitting element 262a shown in Fig. 6A has a top emission structure in which light is taken out in a direction opposite to the substrate 200, and a light-emitting element 262b arranged in Fig. 6B has a bottom-emission structure in which light is extracted to the side of the substrate 200. However, an embodiment of the present invention is not limited to these structures, and may have a dual-emission structure in which light extracted from the light-emitting element is extracted in both the top and bottom directions with respect to the substrate 200 over which the light-emitting element is formed.

[0206] The light-emitting elements 262a and 262b each include the electrode 101, the electrode 102, an electrode 103, and an electrode 104 above the substrate 200. At least one light-emitting layer 130 and a charge generation layer 115 are provided between the electrode 101 and the electrode 102, between the electrode 102 and the electrode 103, and between the electrode 102 and the electrode 104. The hole-injection layer 111, the hole-transport layer 112, the light-emitting layer 140, the electron-transport layer 113, the electron-injection layer 114, the hole-injection layer 116, the hole-transport layer 117, the electron-transport layer 118, and the electron-injection layer 119 are further provided.

[0207] The electrode 101 comprises a conductive layer 101a and a conductive layer 101b over and in contact with the conductive layer 101a. The electrode 103 comprises a conductive layer 103a and a conductive layer 103b over and in contact with the conductive layer 103a. The electrode 104 comprises a conductive layer 104a and a conductive layer 104b over and in contact with the conductive layer 104a.

[0208] The light-emitting element 262a, which is in Fig. 6A, and the light-emitting element 262b shown in Fig. 6B, each includes the partition wall 145 between a region 222B disposed between the electrode 101 and the electrode 102, a region 222G disposed between the electrode 102 and the electrode 103, and a region 222R disposed between the electrode 102 and the electrode 104. The partition wall 145 has an insulating property. The partition wall 145 covers end portions of the electrodes 101, 103, and 104 and has openings that overlap with the electrodes. By the partition wall 145, the electrodes provided above the substrate 200 in the regions can be divided into island shapes.

[0209] The light-emitting elements 262a and 262b each include a substrate 220 provided with an optical element 224B, an optical element 224G, and an optical element 224R in the direction in which light emitted from the region 222B, the light emitted from the region 222G, and the light emitted from the region 222R are taken out. The light emitted from each region is emitted to the outside of the light-emitting element via each optical element. In other words, the light from the region 222B, the light from the region 222G, and the light from the region 222R are emitted via the optical element 224B, the optical element 224G, and the optical element 224R, respectively.

[0210] Optical elements 224B, 224G, and 224R each have a function of selectively transmitting light of a specific color of the incident light. For example, the light emitted from region 222B via optical element 224B is blue light, the light emitted from region 222G via optical element 224G is green light, and the light emitted from region 222R via optical element 224R is red light.

[0211] For example, a color layer (also called a color filter), a bandpass filter, a multilayer filter, or the like can be used for the optical elements 224R, 224G, and 224B. Alternatively, color conversion elements can be used as the optical elements. A color conversion element is an optical element that converts incident light into light with a longer wavelength than the incident light. Quantum dot elements can be advantageously used as the color conversion elements. The use of quantum dots can increase the color reproducibility of the display device.

[0212] A plurality of optical elements may also be arranged over each of the optical elements 224R, 224G, and 224B. As another optical element, for example, a circularly polarizing plate, an anti-reflection film, or the like may be provided. A circularly polarizing plate provided on the side where light emitted from the light-emitting element of the display device is taken out can prevent a phenomenon in which light incident from the outside of the display device is reflected inside the display device and redirected to the outside. An anti-reflection film can attenuate external light reflected from a surface of the display device. This leads to clear observation of light emitted from the display device.

[0213] It should be noted that in Fig. 6A and Fig. 6B blue light (B), green light (G) and red light (R) emitted from the areas via the optical elements are schematically represented by arrows made of dashed lines.

[0214] An opaque layer 223 is provided between the optical elements. The opaque layer 223 has a function of blocking light emitted from the adjacent regions. Note that a structure without the opaque layer 223 can also be used.

[0215] The opaque layer 223 has a function of reducing the reflection of external light. The opaque layer 223 has a function of preventing mixing of light emitted from an adjacent light-emitting element. A metal, a resin containing a black pigment, carbon black, a metal oxide, a composite oxide containing a solid solution of a plurality of metal oxides, or the like can be used as the opaque layer 223.

[0216] For the substrate 200 and the substrate 220 provided with the optical elements, reference may be made to the substrate of Embodiment 1.

[0217] Furthermore, the light-emitting elements 262a and 262b have a microcavity structure. <<Mikrokavitätsstruktur> >

[0218] Light emitted from the light-emitting layer 130 and the light-emitting layer 140 oscillates between a pair of electrodes (e.g., the electrode 101 and the electrode 102). The light-emitting layer 130 and the light-emitting layer 140 are formed at a location such that they amplify the light of a desired wavelength among light to be emitted. For example, by adjusting the optical length from a reflecting portion of the electrode 101 to a light-emitting portion of the light-emitting layer 130 and the optical length from a reflecting portion of the electrode 102 to the light-emitting portion of the light-emitting layer 130, the light of a desired wavelength among light emitted from the light-emitting layer 130 can be amplified.By adjusting the optical length from the reflective region of the electrode 101 to the light-emitting region of the light-emitting layer 140 and the optical length from the reflective region of the electrode 102 to the light-emitting region of the light-emitting layer 140, light of a desired wavelength can also be amplified among light emitted from the light-emitting layer 140. In the case of a light-emitting element in which a plurality of light-emitting layers (here, the light-emitting layers 130 and 140) are stacked, the optical lengths of the light-emitting layers 130 and 140 are preferably optimized.

[0219] In each of the light-emitting elements 262a and 262b, the light of a desired wavelength can be amplified among the light emitted from the light-emitting layers 130 and 140 by adjusting the thicknesses of the conductive layers (the conductive layer 101b, the conductive layer 103b, and the conductive layer 104b) in each region. Note that the thickness of at least one of the hole-injection layer 111 and the hole-transport layer 112 may differ between regions to amplify the light emitted from the light-emitting layers 130 and 140.

[0220] For example, in the case where the refractive index of the conductive material having a function of reflecting light in the electrodes 101 to 104 is lower than the refractive index of the light-emitting layer 130 or 140, the thickness of the conductive layer 101b of the electrode 101 is adjusted such that the optical length between the electrode 101 and the electrode 102 becomes m B λ B / 2 becomes (m B is a natural number and λ B is the wavelength of the light amplified in the region 222B). The thickness of the conductive layer 103b of the electrode 103 is similarly adjusted such that the optical length between the electrode 103 and the electrode 102 becomes m G λ G / 2 becomes (m G is a natural number and λ G is the wavelength of the light that is amplified in the region 222G). Furthermore, the thickness of the conductive layer 104b of the electrode 104 is adjusted such that the optical length between the electrode 104 and the electrode 102 is m R λ R / 2 becomes (m R is a natural number and λ R is the wavelength of light that is amplified in the 222R range).

[0221] In the above manner, the microcavity structure in which the optical length between the pair of electrodes is adjusted in the respective regions can suppress light scattering and absorption in the vicinity of the electrodes, resulting in high light extraction efficiency. In the above structure, the conductive layers 101b, 103b, and 104b preferably have a light transmission function. The materials for the conductive layers 101b, 103b, and 104b may be the same as or different from each other. Each of the conductive layers 101b, 103b, and 104b may have a multilayer structure composed of two or more layers.

[0222] Since the light-emitting element 262a, which is Fig. 6A, has a top-emission structure, the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a preferably have a function of reflecting light. Furthermore, the electrode 102 preferably has functions of transmitting and reflecting light.

[0223] Since the light-emitting element 262b, which is Fig. 6B, has a bottom-emission structure, the conductive layer 101a, the conductive layer 103a, and the conductive layer 104a preferably have light-transmitting and light-reflecting functions. Furthermore, the electrode 102 preferably has a light-reflecting function.

[0224] In each of the light-emitting elements 262a and 262b, the conductive layers 101a, 103a, and 104a can be formed from different materials or the same material. If the conductive layers 101a, 103a, and 104a are formed from the same material, the manufacturing cost of the light-emitting elements 262a and 262b can be reduced. Note that each of the conductive layers 101a, 103a, and 104a can have a multilayer structure composed of two or more layers.

[0225] The light-emitting layer 130 in the light-emitting elements 262a and 262b preferably has the structure described in Embodiment 1, in which case, light-emitting elements with high luminous efficiency can be manufactured.

[0226] One or both of the light-emitting layers 130 and 140, such as a light-emitting layer 140a and a light-emitting layer 140b, may have a multilayer structure composed of two layers. The two light-emitting layers, which include two types of light-emitting materials (a first light-emitting material and a second light-emitting material) for emitting light of different colors, enable light emission of a variety of colors. Preferably, the light-emitting materials of the light-emitting layers are specifically selected such that white light can be obtained by combining light emissions from the light-emitting layers 130 and 140.

[0227] One or both of the light-emitting layers 130 and 140 may have a multilayer structure of three or more layers, which may include a layer that does not contain light-emitting material.

[0228] By using the light-emitting element 262a or 262b including the light-emitting layer having the structure described in Embodiment 1 in pixels of a display device as described above, a display device with high luminous efficiency can be manufactured. The display device including the light-emitting element 262a or 262b can thus have low power consumption.

[0229] For the other components of the light-emitting elements 262a and 262b, reference may be made to the components of the light-emitting element 260 or the light-emitting element of Embodiment 1 or 2.

[0230] It should be noted that the structure described in this embodiment may be appropriately combined with any of the structures described in the other embodiments. (Embodiment 4)

[0231] In this embodiment, a display device including a light-emitting element of one embodiment of the present invention is described with reference to Fig. 7A and Fig. 7B, Fig. 8A and Fig. 8B and Fig. 9A and Fig. 9B. <Strukturbeispiel 1 einer Anzeigevorrichtung>

[0232] Fig. Fig. 7A is a plan view showing a display device 600, and Fig. 7B is a cross-sectional view taken along the dashed line AB and the dashed line CD in Fig. 7A. The display device 600 includes driver circuit sections (a signal line driver circuit section 601 and a scan line driver circuit section 603) and a pixel section 602. Note that the signal line driver circuit section 601, the scan line driver circuit section 603, and the pixel section 602 have a function of controlling light emission from a light-emitting element.

[0233] The display device 600 also includes an element substrate 610, a sealing substrate 604, a sealant 605, a region 607 enclosed by the sealant 605, a lead wire 608, and an FPC 609.

[0234] Note that the connecting line 608 is a line for transmitting signals input to the signal line driver circuit section 601 and the scanning line driver circuit section 603, and for receiving a video signal, a clock signal, a start signal, a reset signal, and the like from the FPC 609, which serves as an external input terminal. Although only the FPC 609 is illustrated here, the FPC 609 may be provided with a printed wiring board (PWB).

[0235] As the signal line driver circuit section 601, a CMOS circuit combining an n-channel transistor 623 and a p-channel transistor 624 is formed. Various types of circuits, such as a CMOS circuit, a PMOS circuit, or an NMOS circuit, can be used as the signal line driver circuit section 601 or the scan line driver circuit section 603. Although a driver in which a driver circuit section is formed and a pixel are formed over the same surface of a substrate in the display device of this embodiment, the driver circuit section is not necessarily formed over the substrate and may be formed outside the substrate.

[0236] The pixel section 602 includes a switching transistor 611, a current control transistor 612, and a lower electrode 613 electrically connected to a drain of the current control transistor 612. Note that a partition wall 614 is formed to cover end portions of the lower electrode 613. A positive photosensitive acrylic resin film, for example, can be used as the partition wall 614.

[0237] To achieve favorable coverage, the partition wall 614 is formed to have a curved surface with a curvature at its upper or lower end portion. For example, in the case where a positive photosensitive acrylic is used as the material of the partition wall 614, preferably only the upper end portion of the partition wall 614 has a curved surface with a curvature (where the radius of curvature is 0.2 μm to 3 μm). Either a negative photosensitive resin or a positive photosensitive resin can be used as the partition wall 614.

[0238] Note that there is no particular limitation on the structure of the transistors (transistors 611, 612, 623, and 624). For example, a staggered transistor may be used. Furthermore, there is no particular limitation on the polarity of these transistors. N-channel and p-channel transistors may be used for these transistors, or, for example, either n-channel transistors or p-channel transistors may be used. Furthermore, there is no particular limitation on the crystallinity of a semiconductor film used for the transistor. For example, an amorphous semiconductor film or a crystalline semiconductor film may be used. Examples of a semiconductor material include Group 14 semiconductors (e.g., a semiconductor including silicon), compound semiconductors (including oxide semiconductors), organic semiconductors, and the like.For example, an oxide semiconductor having an energy gap of 2 eV or more, preferably 2.5 eV or more, more preferably 3 eV or more, is preferably used for the transistors so that the off-state current of the transistors can be reduced. Examples of the oxide semiconductor include an In-Ga oxide, an In-M-Zn oxide (M is aluminum (Al), gallium (Ga), yttrium (Y), zirconium (Zr), lanthanum (La), cerium (Ce), tin (Sn), hafnium (Hf), or neodymium (Nd)), and the like.

[0239] An EL layer 616 and an upper electrode 617 are formed over the lower electrode 613. Here, the lower electrode 613 serves as an anode, and the upper electrode 617 serves as a cathode.

[0240] In addition, the EL layer 616 is formed by any of various methods, such as an evaporation method (including a vacuum evaporation method) using an evaporation mask, a droplet ejection method (also referred to as an inkjet method), a coating method such as a spin coating method, and a gravure printing method. As another material contained in the EL layer 616, a low-molecular compound or a high-molecular compound (including an oligomer or a dendrimer) can be used.

[0241] Note that a light-emitting element 618 is formed including the lower electrode 613, the EL layer 616, and the upper electrode 617. The light-emitting element 618 preferably has any of the structures described in Embodiments 1 to 3. In the case where the pixel portion includes a plurality of light-emitting elements, the pixel portion may include either one of the light-emitting elements described in Embodiments 1 to 3 or a light-emitting element having a different structure.

[0242] When the sealing substrate 604 and the element substrate 610 are bonded together with the sealant 605, the light-emitting element 618 is provided in the region 607 enclosed by the element substrate 610, the sealing substrate 604, and the sealant 605. The region 607 is filled with a filler material. In some cases, the region 607 is filled with an inert gas (nitrogen, argon, or the like) or filled with a UV-curing resin or a thermosetting resin that can be used for the sealant 605. For example, a polyvinyl chloride (PVC)-based resin, an acrylic-based resin, a polyimide-based resin, an epoxy-based resin, a silicone-based resin, a polyvinyl butyral (PVB)-based resin, or an ethylene-vinyl acetate (EVA)-based resin can be used.Preferably, the sealing substrate is provided with a recessed part and a desiccant is arranged in the recessed part, in which case deterioration due to the influence of moisture can be prevented.

[0243] An optical element 621 is provided under the sealing substrate 604 to overlap with the light-emitting element 618. An opaque layer 622 is provided under the sealing substrate 604. The structures of the optical element 621 and the opaque layer 622 may be the same as those of the optical element and the opaque layer of Embodiment 3, respectively.

[0244] An epoxy-based resin or a glass frit is preferably used for the sealant 605. Preferably, such a material allows as little moisture or oxygen permeation as possible. A glass substrate, a quartz substrate, or a plastic substrate formed from fiber-reinforced plastic (FRP), polyvinyl fluoride (PVF), polyester, acrylic, or the like can be used as the sealant substrate 604.

[0245] In the above-described manner, the display device comprising any of the light-emitting elements and the optical elements described in Embodiments 1 to 3 can be obtained. <Strukturbeispiel 2 einer Anzeigevorrichtung>

[0246] Next, another example of the display device is shown using Fig. 8A and Fig. 8B. It should be noted that Fig. 8A and Fig. 8B are each a cross-sectional view of a display device of an embodiment of the present invention.

[0247] In Fig. 8A, a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, and 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral portion 1042, a pixel portion 1040, a driving circuit portion 1041, lower electrodes 1024R, 1024G, and 1024B of the light-emitting elements, a partition wall 1025, an EL layer 1028, an upper electrode 1026 of the light-emitting elements, a sealing layer 1029, a sealing substrate 1031, a sealant 1032, and the like are illustrated.

[0248] In Fig. 8A, examples of the optical elements, i.e., color layers (a red color layer 1034R, a green color layer 1034G, and a blue color layer 1034B), are provided on a transparent base material 1033. An opaque layer 1035 may be further provided. The transparent base material 1033, which is provided with the color layers and the opaque layer, is located on and fixed to the substrate 1001. Note that the color layers and the opaque layer are covered with a covering layer 1036. In the structure in Fig. 8A, red light, green light, and blue light are transmitted through the color layers, and thus an image can be displayed using the pixels of three colors.

[0249] Fig. 8B illustrates an example in which the color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) as examples of the optical elements are provided between the gate insulating film 1003 and the first interlayer insulating film 1020. As in this structure, the color layers may be arranged between the substrate 1001 and the sealing substrate 1031.

[0250] The color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) are provided as examples of the optical elements between the first interlayer insulating film 1020 and the second interlayer insulating film 1021.

[0251] The display device described above has a structure in which light is taken out from the side of the substrate 1001 on which the transistors are formed (a bottom-emission structure), but it may have a structure in which light is taken out from the side of the sealing substrate 1031 (a top-emission structure). <Strukturbeispiel 3 einer Anzeigevorrichtung>

[0252] Fig. 9A and Fig. 9B are each an example of a cross-sectional view of a display device having a top-emission structure. It should be noted that Fig. 9A and Fig. 9B are each a cross-sectional view illustrating the display device of an embodiment of the present invention, and the driving circuit section 1041, the peripheral section 1042 and the like shown in Fig. 8A and Fig. 8B are not shown in these.

[0253] In this case, a substrate that does not transmit light can be used as the substrate 1001. The process up to the step of forming a connection electrode that connects the transistor and the anode of the light-emitting element is performed in a manner similar to that of the display device having a bottom emission structure. Next, a third interlayer insulating film 1037 is formed to cover an electrode 1022. This insulating film may have a planarization function. The third interlayer insulating film 1037 may be formed using a material similar to that of the second interlayer insulating film, or may be formed using one of different materials.

[0254] The lower electrodes 1024R, 1024G and 1024B of the light-emitting elements each serve as anode, but they can also serve as cathode. In the case of a Fig. 9A and Fig. In the display device having a top-emission structure shown in FIG. 9B, the lower electrodes 1024R, 1024G, and 1024B preferably further have a function of reflecting light. The upper electrode 1026 is provided above the EL layer 1028. Preferably, the upper electrode 1026 has a function of reflecting light and a function of transmitting light, and a microcavity structure may be used between the upper electrode 1026 and the lower electrodes 1024R, 1024G, and 1024B, in which case the intensity of light having a specific wavelength is increased.

[0255] In case of a Fig. In the top-emission structure shown in Figure 9, sealing can be performed with the sealing substrate 1031 on which the color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) are provided. The sealing substrate 1031 can be provided with the opaque layer 1035 positioned between pixels. Note that a transparent substrate is advantageously used as the sealing substrate 1031.

[0256] Fig. 9A exemplifies the structure provided with the light-emitting elements and the color layers for the light-emitting elements; however, the structure is not limited thereto. For example, as shown in Fig. 9B, a structure including the red color layer 1034R and the blue color layer 1034B, but no green color layer, can be used to obtain a full-color display with the three colors of red, green, and blue. The structure in which, as shown in Fig. 9A, the light-emitting elements are provided with the color layers, is effective in suppressing the reflection of external light. In contrast, the Fig. 9B, in which the light-emitting elements are provided with the red color layer and the blue color layer but without the green color layer, is effective for reducing power consumption due to a small energy loss of the light emitted from the green light-emitting element.

[0257] Although a display device including subpixels of three colors (red, green, and blue) was described above, the number of colors of subpixels may be four (red, green, blue, and yellow, or red, green, blue, and white). In this case, a color layer having a yellow light transmitting function or a function of transmitting light of a plurality of colors selected from blue, green, yellow, and red may be used. If the color layer can transmit light of a plurality of colors selected from blue, green, yellow, and red, the light transmitted by the color layer may be white light. Since the light-emitting element that emits yellow or white light has high emission efficiency, the display device with such a structure can have low power consumption.

[0258] Furthermore, in the display device 600, which is shown in Fig. 7A and Fig. 7B, a sealing layer may be formed in the region 607 enclosed by the element substrate 610, the sealing substrate 604, and the sealant 605. For the sealing layer, a resin such as a polyvinyl chloride (PVC)-based resin, an acrylic-based resin, a polyimide-based resin, an epoxy-based resin, a silicone-based resin, a polyvinyl butyral (PVB)-based resin, or an ethylene-vinyl acetate (EVA)-based resin may be used. Alternatively, an inorganic material such as silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, or aluminum nitride may be used. Forming the sealing layer in the region 607 can prevent the light-emitting element 618 from deteriorating due to contaminants such as water, which is preferable.It should be noted that in the case where the sealing layer is formed, the sealant 605 is not necessarily provided.

[0259] When the sealing layer has a multi-layer structure, contaminants such as water can be effectively prevented from penetrating from the outside of the display device 600 into the light-emitting element 618 located inside the display device. In the case where the sealing layer has a multi-layer structure, a resin and an inorganic material are preferably stacked.

[0260] The structures described in this embodiment may be appropriately combined with any of the other structures of this embodiment and the other embodiments. (Embodiment 5)

[0261] In this embodiment, a display module, electronic devices, a light-emitting device, and lighting devices each including the light-emitting element of one embodiment of the present invention are described with reference to Fig. 10, Fig. 11A to Fig. 11G, Fig. 12A to Fig. 12C and Fig. 13 described. <anzeigemodul>

[0262] With a display module 8000 in Fig. 10, a touch sensor 8004 connected to an FPC 8003, a display device 8006 connected to an FPC 8005, a frame 8009, a printed circuit board 8010, and a battery 8011 are arranged between an upper cover 8001 and a lower cover 8002.

[0263] The light-emitting element of one embodiment of the present invention can be used, for example, for the display device 8006.

[0264] The shapes and sizes of the upper cover 8001 and the lower cover 8002 can be changed as needed according to the sizes of the touch sensor 8004 and the display device 8006.

[0265] The touch sensor 8004 may be a resistive touch sensor or a capacitive touch sensor and may be configured to overlap with the display device 8006. A counter substrate (sealing substrate) of the display device 8006 may have a touch sensor function. A photosensor may be provided in each pixel of the display device 8006, thereby obtaining an optical touch sensor.

[0266] The frame 8009 protects the display device 8006 and also serves as an electromagnetic shield to block electromagnetic waves generated by the operation of the printed circuit board 8010. The frame 8009 can serve as a radiator plate.

[0267] The printed circuit board 8010 includes a power supply circuit and a signal processing circuit for outputting a video signal and a clock signal. An external AC power source or the separately provided battery 8011 can be used as the power source for supplying power to the power supply circuit. The battery 8011 can be omitted if an AC power source is used.

[0268] The display module 8000 can be additionally equipped with a part such as a polarizing plate, a retardation plate or a prism film. <Elektronisches Gerät>

[0269] Fig. 11A to Fig. 11G show electronic devices. These electronic devices may each include a housing 9000, a display section 9001, a speaker 9003, operation buttons 9005 (including a power button or an operation switch), a connection terminal 9006, a sensor 9007 (a sensor having a function for measuring force, displacement, position, speed, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, electric power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared ray), a microphone 9008, and the like. Furthermore, the sensor 9007 may have a function for measuring biological information, just like a pulse sensor and a fingerprint sensor.

[0270] The Fig. 11A to Fig. The electronic devices shown in Figure 11G may have various functions, such as a function for displaying various data (a still image, a moving image, a text image, and the like) on the display section, a touch sensor function, a function for displaying a calendar, the date, the time, and the like, a function for controlling processing with various types of software (programs), a wireless communication function, a function for connecting to various computer networks using a wireless communication function, a function for transmitting and receiving various data using a wireless communication function, a function for reading a program or data stored in a storage medium and displaying the program or data on the display section, and the like. It should be noted that the electronic devices shown in Fig. 11A to Fig. 11G, without limitation to the above functions, may have a variety of functions. Although in Fig. 11A to Fig. 11G, the electronic devices may include a plurality of display sections. The electronic devices may each include a camera or the like and have a function for capturing a still image, a function for capturing a moving image, a function for storing the captured image in a storage medium (an external storage medium or a storage medium built into the camera), a function for displaying the captured image on the display section, and the like.

[0271] The electronic devices in Fig. 11A to Fig. 11G are described in detail below.

[0272] Fig. 11A is a perspective view of a portable information terminal 9100. The display section 9001 of the portable information terminal 9100 is flexible. Therefore, the display section 9001 can be installed along a curved surface of a curved housing 9000. The display section 9001 further includes a touch sensor, and an operation can be performed by touching the screen with a finger, a stylus, or the like. For example, an application can be launched by touching an icon displayed on the display section 9001.

[0273] Fig. 11B is a perspective view illustrating a portable information terminal 9101. The portable information terminal 9101 serves, for example, as one or more of a telephone, a notebook, and an information search system. In particular, the portable information terminal 9101 can be used as a smartphone. Note that the speaker 9003, the connection terminal 9006, the sensor 9007, and the like shown in Fig. 11A, in the portable information terminal 9101, as in the portable information terminal 9100 shown in Fig. 11A. The portable information terminal 9101 can display characters and image information on its plurality of surfaces. For example, three operation buttons 9050 (also referred to as operation icons, or simply as icons) may be displayed on one surface of the display section 9001. In addition, information 9051 represented by dashed rectangles may be displayed on another surface of the display section 9001. Examples of the information 9051 include an indication indicating the arrival of an incoming email, a message from a social networking service (SNS), a call, and the like, the subject and sender of an email and an SNS message, the date, time, remaining battery capacity, and an indication indicating the strength of a received signal such as a radio wave.Instead of the information 9051, the operation buttons 9050 or the like may be displayed in the positions where the information 9051 is displayed.

[0274] As the material for the case 9000, for example, an alloy, a plastic, or ceramic can be used. A reinforced plastic can also be used as the plastic. A carbon fiber reinforced plastic (CFRP), which is a type of reinforced plastic, is advantageous in that it is lightweight and corrosion-free. Other examples of the reinforced plastic include one containing a glass fiber and one containing an aramid fiber. As the alloy, an aluminum alloy and a magnesium alloy can be cited. An amorphous alloy (also called metallic glass) containing zirconium, copper, nickel, and titanium, in particular, has very high elastic strength.This amorphous alloy has a glass transition region at room temperature, is also called a bulk-solidified amorphous alloy, and essentially has an amorphous atomic structure. An alloy material is modeled in a mold of at least a portion of the housing and solidified by a solidification-casting process, thereby forming the portion of the housing with the bulk-solidified amorphous alloy. The amorphous alloy may contain beryllium, silicon, niobium, boron, gallium, molybdenum, tungsten, manganese, iron, cobalt, yttrium, vanadium, phosphorus, carbon, or the like, in addition to zirconium, copper, nickel, and titanium. The amorphous alloy may be formed by a vacuum evaporation process, a sputtering process, an electroplating process, an electroless plating process, or the like instead of the solidification-casting process.The amorphous alloy may contain a microcrystal or a nanocrystal, as long as a state of no long-range order (a periodic structure) is maintained as a whole. Note that the term alloy includes both a complete solid-solution alloy with a single solid-phase structure and a partial solution with two or more phases. The casing 9000 using the amorphous alloy can exhibit high elastic strength. Even if the portable information terminal 9101 is dropped and the impact causes temporary deformation, the use of the amorphous alloy in the casing 9000 enables it to return to its original shape; accordingly, the shock resistance of the portable information terminal 9101 can be improved.

[0275] Fig. 11C is a perspective view illustrating a portable information terminal 9102. The portable information terminal 9102 has a function of displaying information on three or more surfaces of the display section 9001. Here, information 9052, information 9053, and information 9054 are displayed on different surfaces. For example, a user of the portable information terminal 9102 can view the display (here, information 9053) with the portable information terminal 9102 placed in a breast pocket of their shirt. Specifically, the telephone number, name, or the like of a caller can be displayed in a position visible from above the portable information terminal 9102. Therefore, the user can view the display without taking the portable information terminal 9102 out of the pocket and decide whether to answer the call.

[0276] Fig. 11D is a perspective view of a portable information terminal 9200 in the form of a wristwatch. The portable information terminal 9200 can perform various applications, such as mobile phone calls, sending and receiving emails, displaying and editing text, playing music, Internet communication, and computer games. The display surface of the display section 9001 is curved, and images can be displayed on the curved display surface. The portable information terminal 9200 can use short-range communication, which is a communication method according to an existing communication standard. In this case, for example, mutual communication can be performed between the portable information terminal 9200 and a headset capable of wireless communication, thus enabling hands-free calling.The portable information terminal 9200 includes the connection port 9006, and data can be sent and received directly to / from another information terminal via a connector. Charging with power through the connection port 9006 is possible. Note that charging can be performed without the connection port 9006 by wireless power supply.

[0277] Fig. 11E, Fig. 11F and Fig. 11G are perspective views of a foldable portable information terminal 9201. Fig. 11E is a perspective view illustrating the portable information terminal 9201 being opened. Fig. 11F is a perspective view illustrating the portable information terminal 9201 being changed from the opened state to the folded state or from the folded state to the opened state. Fig. 11G is a perspective view illustrating the portable information terminal 9201 being folded. The portable information terminal 9201 is highly portable when folded. When the portable information terminal 9201 is opened, a seamless large display area offers high browseability. The display section 9001 of the portable information terminal 9201 is supported by three housings 9000 connected to each other by hinges 9055. By folding the portable information terminal 9201 at a junction between two housings 9000 with the hinges 9055, the shape of the portable information terminal 9201 can be reversibly changed from the opened state to the folded state. For example, the portable information terminal 9201 can be bent with a radius of curvature greater than or equal to 1 mm and less than or equal to 150 mm.

[0278] Examples of electronic devices include a television set (also called a TV or TV receiver), a monitor for a computer or the like, a digital camera, a digital video camera, a digital photo frame, a mobile phone (also called a cellular phone or portable telephone device), video glasses (a head-mounted display), a portable game console, a portable information terminal, an audio playback device, and a large gaming machine such as a pachinko machine.

[0279] Furthermore, the electronic device of one embodiment of the present invention may comprise a secondary battery. Preferably, the secondary battery can be charged by contactless energy transfer.

[0280] Examples of the secondary battery include a lithium-ion secondary battery such as a lithium polymer battery (lithium-ion polymer battery) using a gel electrolyte, a lithium-ion battery, a nickel-hydride battery, a nickel-cadmium battery, an organic radical battery, a lead-acid battery, an air secondary battery, a nickel-zinc battery, and a silver-zinc battery.

[0281] The electronic device of one embodiment of the present invention may include an antenna. When a signal is received from the antenna, the electronic device can display an image, data, or the like on a display section. If the electronic device includes a secondary battery, the antenna can be used for contactless power transmission.

[0282] The electronic device or lighting device of one embodiment of the present invention exhibits flexibility and can therefore be integrated along a curved interior / exterior wall surface of a house or building, or along a curved interior / exterior surface of a car. For example, the electronic device or lighting device can be used for lighting a dashboard, windshield, vehicle ceiling, and the like. <Licht emittierende Vorrichtung>

[0283] Fig. 12A is a perspective view of a light-emitting device 3000 shown in this embodiment, and Fig. 12B is a cross-sectional view taken along the dashed line EF in Fig. 12A. It should be noted that in Fig. 12A some components are represented by dashed lines to avoid complicating the drawing.

[0284] The light emitting device 3000, which in Fig. 12A and Fig. 12B includes a substrate 3001, a light-emitting element 3005 over the substrate 3001, a first sealing region 3007 provided around the light-emitting element 3005, and a second sealing region 3009 provided around the first sealing region 3007.

[0285] Light is emitted from the light-emitting element 3005 via the substrate 3001 and / or a substrate 3003. In Fig. 12A and Fig. 12B, a structure in which light is emitted from the light-emitting element 3005 toward the lower side (the substrate 3001 side) is illustrated.

[0286] As in Fig. 12A and Fig. As shown in Figure 12B, the light-emitting device 3000 has a double sealing structure in which the light-emitting element 3005 is enclosed by the first sealing region 3007 and the second sealing region 3009. With the double sealing structure, the entry of impurities (e.g., water, oxygen, and the like) from the outside into the light-emitting element 3005 can be advantageously suppressed. Note that it is unnecessary to provide both the first sealing region 3007 and the second sealing region 3009. For example, only the first sealing region 3007 may be provided.

[0287] It should be noted that in Fig. 12B, the first sealing region 3007 and the second sealing region 3009 are provided in contact with the substrate 3001 and the substrate 3003, respectively. However, without being limited to such a structure, for example, the first sealing region 3007 and / or the second sealing region 3009 may be provided in contact with an insulating film or a conductive film provided on the substrate 3001. Alternatively, the first sealing region 3007 and / or the second sealing region 3009 may be provided in contact with an insulating film or a conductive film provided on the substrate 3003.

[0288] Substrate 3001 and substrate 3003 may have structures similar to those of substrate 200 and substrate 220 described in the above embodiment, respectively. Light-emitting element 3005 may have a structure similar to that of any of the light-emitting elements described in the above embodiments.

[0289] For the first sealing portion 3007, a material containing glass (e.g., a glass frit, a glass ribbon, and the like) can be used. For the second sealing portion 3009, a material containing a resin can be used. By using the material containing glass for the first sealing portion 3007, productivity and sealing performance can be improved. Furthermore, by using the material containing a resin for the second sealing portion 3009, impact resistance and heat resistance can be improved. However, the materials used for the first sealing portion 3007 and the second sealing portion 3009 are not limited to these, and the first sealing portion 3007 can be formed using the material containing a resin, and the second sealing portion 3009 can be formed using the material containing glass.

[0290] The glass frit may contain, for example, magnesium oxide, calcium oxide, strontium oxide, barium oxide, cesium oxide, sodium oxide, potassium oxide, boron oxide, vanadium oxide, zinc oxide, tellurium oxide, aluminum oxide, silicon dioxide, lead oxide, tin oxide, phosphorus oxide, ruthenium oxide, rhodium oxide, iron oxide, copper oxide, manganese dioxide, molybdenum oxide, niobium oxide, titanium oxide, tungsten oxide, bismuth oxide, zirconium oxide, lithium oxide, antimony oxide, lead borate glass, tin phosphate glass, vanadate glass, or borosilicate glass. The glass frit preferably contains at least one type of transition metal to absorb infrared light.

[0291] For the above glass frits, for example, a frit paste is applied to a substrate and subjected to heat treatment, laser light irradiation, or the like. The frit paste contains the glass frit and a resin (also called a binder) diluted with an organic solvent. Note that an absorber that absorbs light with the wavelength of the laser light may be added to the glass frit. For example, an Nd:YAG laser or a semiconductor laser is preferably used as the laser. The shape of the laser light can be circular or square.

[0292] For the above resin-containing material, for example, polyester, polyolefin, polyamide (e.g., nylon, aramid), polyimide, polycarbonate, or an acrylic resin, polyurethane, or epoxy resin can be used. Alternatively, a material containing a resin with a siloxane bond, such as silicone, can be used.

[0293] Note that in the case where the material containing glass is used for the first sealing portion 3007 and / or the second sealing portion 3009, the material containing glass preferably has a thermal expansion coefficient close to that of the substrate 3001. With the above structure, the formation of a crack in the material containing glass or the substrate 3001 due to thermal stress can be suppressed.

[0294] For example, the following advantageous effect can be obtained in the case where the material containing glass is used for the first sealing portion 3007, and the material containing a resin is used for the second sealing portion 3009.

[0295] The second sealing portion 3009 is provided closer to an outer portion of the light-emitting device 3000 than the first sealing portion 3007. In the light-emitting device 3000, deformation due to external force or the like increases toward the outer portion. Accordingly, the outer portion of the light-emitting device 3000, which is more deformed, that is, the second sealing portion 3009, is sealed using the material containing a resin, and the first sealing portion 3007, provided on an inner side of the second sealing portion 3009, is sealed using the material containing glass, whereby the light-emitting device 3000 is less likely to be damaged even if deformation due to external force or the like occurs.

[0296] Furthermore, as in Fig. 12B, a first region 3011 corresponds to the region enclosed by the substrate 3001, the substrate 3003, the first sealing region 3007, and the second sealing region 3009. A second region 3013 corresponds to the region enclosed by the substrate 3001, the substrate 3003, the light-emitting element 3005, and the first sealing region 3007.

[0297] The first region 3011 and the second region 3013 are preferably filled with, for example, an inert gas such as a rare gas or a nitrogen gas. Alternatively, the first region 3011 and the second region 3013 are preferably filled with a resin such as an acrylic resin or an epoxy resin. Note that for the first region 3011 and the second region 3013, a reduced pressure state is preferable to an atmospheric pressure state.

[0298] Fig. Figure 12C shows a modification example of the structure in Fig. 12B. Fig. 12C is a cross-sectional view illustrating the modification example of the light-emitting device 3000.

[0299] Fig. Fig. 12C illustrates a structure in which a desiccant 3018 is provided in a recessed portion provided in a part of the substrate 3003. The other components are the same as those of the structure shown in Fig. 12B.

[0300] As the desiccant 3018, a substance that adsorbs moisture and the like by chemical adsorption or a substance that adsorbs moisture and the like by physical adsorption can be used. Examples of the substance that can be used as the desiccant 3018 include alkali metal oxides, alkaline earth metal oxides (such as calcium oxide, barium oxide, and the like), sulfate, metal halides, perchlorate, zeolite, silica gel, and the like. <beleuchtungsvorrichtung>

[0301] Fig. 13 illustrates an example in which the light-emitting element is used for an indoor lighting device 8501. Since the light-emitting element can have a larger area, a lighting device with a large area can also be formed. In addition, a lighting device 8502 in which a light-emitting region has a curved surface can also be formed using a housing with a curved surface. The light-emitting element described in this embodiment is in the form of a thin film, which makes it possible to design the housing more freely. Consequently, the lighting device can be artistically constructed in various ways. Furthermore, a wall of the room can be provided with a large lighting device 8503.Touch sensors may be arranged in the lighting devices 8501, 8502 and 8503 to control the switching on or off of the lighting devices.

[0302] Furthermore, when the light-emitting element is used for the surface side of a table, a lighting device 8504 having a function as a table can be obtained. When the light-emitting element is used as part of another piece of furniture, a lighting device having a function as the relevant piece of furniture can be obtained.

[0303] As described above, display modules, light-emitting devices, electronic devices, and lighting devices can be obtained using the light-emitting element of one embodiment of the present invention. Note that the light-emitting element can be used for electronic devices in various fields, without being limited to the lighting devices and electronic devices described in this embodiment.

[0304] The structure described in this embodiment can be appropriately combined with any of the structures described in the other embodiments. [Example 1]

[0305] In this example, examples of the fabrication of the light-emitting element of one embodiment of the present invention and comparative light-emitting elements are shown. The structure of each of the light-emitting elements fabricated in this example is the same as that shown in Fig. 1. Table 1 shows details of the elemental structures. Structures and abbreviations of the compounds used here are also listed below. [Table 1] Schicht Bezugszeichen Filmdicke (nm) Material Gewichtsverhältnis Licht emittierendes Element 1 Elektrode 102 200 Al - Elektroneninjektionsschicht 119 1 LiF - Elektronentransportschicht 118(2) 10 BPhen - 118(1) 20 4,6mCzP2Pm - Licht emittierende Schicht 130 40 4,6mCzP2Pm : Ir(dmpimpt-Me)3 : TBRb 1:0,1:0,05 Lochtransportschicht 112 20 mCzFLP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting reference element 1 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 BPhen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 4.6mCzP2Pm : TBRb 1:0,005 Hole transport layer 112 20 mCzFLP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting reference element 2 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 BPhen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 4.6mCzP2Pm : Ir(dmpimpt-Me)3 1:0,1 Hole transport layer 112 20 mCzFLP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting reference element 3 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 15 BPhen - 118(1) 10 mDBTBIm-II : Ir(dmpimpt-Me)3 1:0,08 Light-emitting layer 130 30 mCP : Ir(dmpimpt-Me)3 1:0,08 Hole transport layer 112 20 mCP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 110 ITSO - <Herstellung der Licht emittierenden Elemente>

[0306] Methods for manufacturing the light-emitting elements of this example are described below. <<Herstellung des Licht emittierenden Elements 1> >

[0307] As electrode 101, an ITSO film with a thickness of 70 nm was formed over a glass substrate. The electrode area of electrode 101 was 4 mm 2 (2 mm × 2 mm).

[0308] As hole injection layer 111, DBT3P-II and molybdenum oxide (MoO3) were deposited by co-evaporation in a weight ratio of 1:0.5 (DBT3P-II:MoO3) in a thickness of 60 nm over the electrode 101.

[0309] As hole transport layer 112, 9-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-9H-carbazole (abbreviation: mCzFLP) was deposited by evaporation in a thickness of 20 nm over the hole injection layer 111.

[0310] As the light-emitting layer 130, 4.6mCzP2Pm, Ir(dmpimpt-Me)3, and TBRb were co-evaporated over the hole-transport layer 112 in a weight ratio of 1:0.1:0.05 (4.6mCzP2Pm:Ir(dmpimpt-Me)3:TBRb) to a thickness of 40 nm. In the light-emitting layer 130, Ir(dmpimpt-Me)3 is a phosphorescent compound corresponding to the first organic compound, 4.6mCzP2Pm corresponds to the second organic compound, and TBRb is a fluorescent compound corresponding to the third organic compound.

[0311] As the electron-transport layer 118, 4.6mCzP2Pm and Bphen were successively deposited by evaporation to a thickness of 20 nm and 10 nm, respectively, over the light-emitting layer 130. As the electron-injection layer 119, LiF was then deposited by evaporation to a thickness of 1 nm over the electron-transport layer 118.

[0312] As electrode 102, aluminum (Al) was formed in a thickness of 200 nm over the electron injection layer 119.

[0313] Next, the electrodes and the EL layer were sealed in a glove box containing a nitrogen atmosphere by attaching a glass substrate for sealing to the glass substrate on which the organic materials were deposited using a sealant for an organic EL device. Specifically, after the sealant was applied to enclose the organic materials deposited on the glass substrate and the glass substrate was attached to the glass substrate for sealing, irradiation with UV light with a wavelength of 365 nm at 6 J / cm 2 and a heat treatment at 80 °C for one hour. This process resulted in the light-emitting element 1. <<Herstellung der Licht emittierenden Vergleichselemente 1 und 2> >

[0314] The comparative light-emitting elements 1 and 2 were manufactured through the same steps as those of the above-described light-emitting element 1, except for the step of forming the light-emitting layer 130.

[0315] As the light-emitting layer 130 of the comparative light-emitting element 1, 4,6mCzP2Pm and TBRb were deposited by co-evaporation in a weight ratio of 1:0.005 (4,6mCzP2Pm:TBRb) to a thickness of 40 nm. In the light-emitting layer 130, the first organic compound is not included, 4,6mCzP2Pm corresponds to the second organic compound, and TBRb is a fluorescent compound corresponding to the third organic compound.

[0316] As the light-emitting layer 130 of the comparative light-emitting element 2, 4,6mCzP2Pm and Ir(dmpimpt-Me)3 were co-evaporated in a weight ratio of 1:0.1 (4,6mCzP2Pm:Ir(dmpimpt-Me)3) to a thickness of 40 nm. In the light-emitting layer 130, Ir(dmpimpt-Me)3 is a phosphorescent compound corresponding to the first organic compound, 4,6mCzP2Pm corresponds to the second organic compound, and a fluorescent compound corresponding to the third organic compound is not included. <<Herstellung des Licht emittierenden Vergleichselements 3> >

[0317] As electrode 101, an ITSO film with a thickness of 110 nm was formed over a glass substrate. The electrode area of electrode 101 was 4 mm 2 (2 mm × 2 mm).

[0318] As hole injection layer 111, DBT3P-II and molybdenum oxide (MoO3) were deposited by co-evaporation in a weight ratio of 1:0.5 (DBT3P-II:MoO3) in a thickness of 60 nm over the electrode 101.

[0319] As hole transport layer 112, mCP was deposited by evaporation to a thickness of 20 nm over the hole injection layer 111.

[0320] As the light-emitting layer 130, mCP and Ir(dmpimpt-Me)3 were deposited by co-evaporation in a weight ratio of 1:0.08 (mCP:Ir(dmpimpt-Me)3) to a thickness of 30 nm. In the light-emitting layer 130, Ir(dmpimpt-Me)3 is a phosphorescent compound corresponding to the guest material, and mCP corresponds to the host material.

[0321] As the electron-transport layer 118, mDBTBIm-II and Ir(dmpimpt-Me)3 were co-evaporated in a weight ratio of 1:0.08 (mDBTBIm-II:Ir(dmpimpt-Me)3) to a thickness of 10 nm over the light-emitting layer 130, and then BPhen was deposited by evaporation to a thickness of 15 nm. As the electron-injection layer 119, LiF was then deposited by evaporation to a thickness of 1 nm over the electron-transport layer 118.

[0322] As electrode 102, aluminum (Al) was formed in a thickness of 200 nm over the electron injection layer 119.

[0323] Next, the electrodes and the EL layer were sealed in a nitrogen-filled glove box by attaching a glass substrate for sealing to the glass substrate over which the organic materials were deposited using a sealant for an organic EL device. For the detailed procedure, refer to the description of light-emitting element 1. Through this process, comparative light-emitting element 3 was obtained. <Eigenschaften der Licht emittierenden Elemente>

[0324] Next, the characteristics of the fabricated light-emitting element 1 and the fabricated comparison light-emitting elements 1 to 3 were measured. Luminances and CIE chromaticities were measured with a luminance colorimeter (BM-5A manufactured by TOPCON TECHNOHOUSE CORPORATION), and electroluminescence spectra were measured with a multi-channel spectrometer (PMA-11 manufactured by Hamamatsu Photonics KK).

[0325] Fig. 14 shows luminance-current density characteristics of the light-emitting element 1 and the comparative light-emitting elements 1 to 3. Fig. 15 shows the luminance-voltage characteristics of these. Fig. 16 shows the power efficiency-luminance characteristics of these. Fig. 17 shows the power efficiency-luminance characteristics of these. Fig. 18 shows the external quantum efficiency-luminance characteristics of these. Fig. Figure 19 shows the electroluminescence spectra of the light-emitting element 1 and the light-emitting elements 1 to 3, to which a current with a current density of 2.5 mA / cm 2 The measurements of the light-emitting elements were performed at room temperature (in an atmosphere maintained at 23 °C).

[0326] Table 2 shows the element properties of the light-emitting element 1 and the comparative light-emitting elements 1 to 3 at about 1000 cd / m 2 . [Table 2] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x, y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) external quantum efficiency (%) Light-emitting element 1 3,60 2,67 (0,528, 0,468) 1060 39,6 34,5 14,2 Light-emitting reference element 1 3,80 4,91 (0,482, 0,497) 1010 20,7 17,1 6,5 Light-emitting reference element 2 3,70 2,80 (0,411, 0,550) 1000 35,9 30,5 11,2 Light-emitting reference element 3 6,60 8,46 (0,165, 0,236) 1510 17,9 8,5 10,9

[0327] As in Fig. As shown in Figure 19, the electroluminescence spectra of the light-emitting element 1 and the comparative light-emitting element 1 exhibit peaks at wavelengths of 572 nm and 565 nm, respectively. This indicates that the light-emitting element 1 and the comparative light-emitting element 1 emit yellow light originating from TBRb, which is the fluorescent compound.

[0328] Furthermore, the electroluminescence spectrum of comparative light-emitting element 3 exhibits a peak at a wavelength of 460 nm. This indicates that comparative light-emitting element 3 emits blue light originating from Ir(dmpimpt-Me)3, which is the phosphorescent compound. The electroluminescence spectrum of comparative light-emitting element 2 exhibits a peak at a wavelength of 545 nm. This indicates that comparative light-emitting element 2 emits yellow light. In light-emitting element 1, comparative light-emitting element 1, comparative light-emitting element 2, and comparative light-emitting element 3, the half-widths of the electroluminescence spectra are 83 nm, 78 nm, 105 nm, and 52 nm, respectively.The electroluminescence spectrum of comparative light-emitting element 2 exhibits a broader spectrum shape than those of the other light-emitting elements (light-emitting element 1, comparative light-emitting element 1, and comparative light-emitting element 3). As described later, the light emission from comparative light-emitting element 2, which exhibits a broad spectrum shape, originates from an exciplex formed by 4,6mCzP2Pm and Ir(dmpimpt-Me)3.

[0329] As in Fig. 14, Fig. 15, Fig. 16, Fig. 17, Fig. As shown in Figure 18 and Table 2, the light-emitting element 1 exhibits a higher luminous efficiency (current efficiency, power efficiency, and external quantum efficiency) than the comparative light-emitting element 1, which also emits light originating from TBRb. Since the maximum generation probability of singlet excitons by recombination of carriers (holes and electrons) injected from the pair of electrodes is 25%, the maximum external quantum efficiency is 7.5% in the case where the external light extraction efficiency is 30%. The light-emitting element 1 exhibits an external quantum efficiency of more than 7.5%.This is because, in addition to light from singlet excitons generated by the recombination of charge carriers (holes and electrons) injected from the pair of electrodes, the light-emitting element 1 emits light from the energy transition of triplet excitons, or light from the fluorescent compound generated by singlet excitons generated by reverse intersystem crossing of triplet excitons in the exciplex. In other words, the light-emitting element 1 is the light-emitting element of one embodiment of the present invention that utilizes ExEF.

[0330] Furthermore, the drop (also called roll-off) of the luminous efficiency on the high luminance side of the light-emitting element 1 is smaller than that of the comparative light-emitting element 2. The luminous efficiency (the current efficiency, the power efficiency, and the external quantum efficiency) in a high luminance region is higher than that of the comparative light-emitting element 2. That is, a feature of the light-emitting element of one embodiment of the present invention is that roll-off is less likely to occur than in the light-emitting element that emits light originating from the exciplex.

[0331] In addition, the light-emitting element 1 is operated at a higher luminous efficiency (current efficiency, power efficiency, and external quantum efficiency) and at a lower driving voltage than the comparative light-emitting element 3. Thus, the light-emitting element 1 of an embodiment of the present invention has a high luminous efficiency, a low driving voltage, and a low power consumption. <Ergebnisse der CV-Messung>

[0332] The electrochemical properties (oxidation reaction properties and reduction reaction properties) of the above compounds were measured by cyclic voltammetry (CV). Note that an electrochemical analyzer (ALS Model 600A or 600C, manufactured by BAS Inc.) was used for the measurement, and the measurement was performed on a solution obtained by dissolving each compound in N,N-dimethylformamide (abbreviation: DMF). During the measurement, the potential of a working electrode with respect to the reference electrode was changed within an appropriate range to obtain the oxidation peak potential and the reduction peak potential. Furthermore, the HOMO and LUMO levels of each compound were calculated from the assumed redox potential of the reference electrode of -4.94 eV and the obtained peak potentials.

[0333] According to the CV measurement results, the oxidation potential and reduction potential of 4.6mCzP2Pm were 0.95 V and -2.06 V, respectively. Furthermore, the HOMO and LUMO levels of 4.6mCzP2Pm, calculated from the CV measurement, were -5.89 eV and -2.88 eV, respectively. Thus, it was found that 4.6mCzP2Pm has a low LUMO level. The oxidation potential and reduction potential of Ir(dmpimpt-Me)3 were 0.24 V and -2.67 V, respectively. Furthermore, the HOMO and LUMO levels of Ir(dmpimpt-Me)3, calculated from the CV measurement results, were -5.18 eV and -2.27 eV, respectively. Thus, it was found that Ir(dmpimpt-Me)3 has a high HOMO level.

[0334] As described above, the LUMO level of 4,6mCzP2Pm is lower than that of Ir(dmpimpt-Me)3, and the HOMO level of Ir(dmpimpt-Me)3 is higher than that of 4,6mCzP2Pm. Thus, in the case where the compounds are used in a light-emitting layer, as in the light-emitting element 1 and the comparative light-emitting element 2, electrons and holes serving as charge carriers are efficiently injected from a pair of electrodes into 4,6mCzP2Pm and Ir(dmpimpt-Me)3, respectively, so that 4,6mCzP2Pm and Ir(dmpimpt-Me)3 can form an exciplex.

[0335] The exciplex formed by 4,6mCzP2Pm and Ir(dmpimpt-Me)3 has the LUMO level in 4,6mCzP2Pm and the HOMO level in Ir(dmpimpt-Me)3. The energy difference between the LUMO level of 4,6mCzP2Pm and the HOMO level of Ir(dmpimpt-Me)3 is 2.30 eV. This value is essentially the same as the light emission energy determined from the peak wavelength of the electroluminescence spectrum of the reference light-emitting element 2 in Fig. 19 (2.28 eV). This result implies that the electroluminescence spectrum of the reference light-emitting element 2 corresponds to the light emission from the exciplex formed by 4,6mCzP2Pm and Ir(dmpimpt-Me)3. In the exciplex, the difference between the S1 level and the T1 level is small; thus, the light emission energy can be considered as the energy of the S1 level and the T1 level (2.28 eV).

[0336] Fig. Figure 29 shows the measurement results of an absorption spectrum of TBRb in a toluene solution. 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).

[0337] As in Fig. As shown in Figure 29, the absorption spectrum of TBRb exhibits an absorption band with a high molar absorption coefficient at approximately 450 nm to 550 nm. This absorption band has a region overlapping with the electroluminescence spectrum of the exciplex of comparative light-emitting element 2 (the exciplex formed by 4,6mCzP2Pm and Ir(dmpimpt-Me)3). Thus, the excitation energy can be efficiently transferred from the exciplex formed by 4,6mCzP2Pm and Ir(dmpimpt-Me)3 to TBRb, which is the fluorescent compound.

[0338] Furthermore, the light emission energy of TBRb of light-emitting element 1 is lower than that of the exciplex of the comparative light-emitting element 2 (the exciplex formed by 4,6mCzP2Pm and Ir(dmpimpt-Me)3). This also indicates that in light-emitting element 1, the excitation energy can be efficiently transferred from the exciplex formed by 4,6mCzP2Pm and Ir(dmpimpt-Me)3 to TBRb, which is the fluorescent compound. As a result, light-emitting element 1 can achieve high-efficiency light emission from TBRb.

[0339] In both light-emitting element 1 and reference light-emitting element 2, 4,6mCzP2Pm and Ir(dmpimpt-Me)3 form an exciplex; thus, the exciplex can be formed with an energy corresponding to the difference between the LUMO level of 4,6mCzP2Pm and the HOMO level of Ir(dmpimpt-Me)3 (2.30 eV). In contrast, in reference light-emitting element 3, Ir(dmpimpt-Me)3 is excited to emit light; thus, at least an energy corresponding to the difference between the LUMO level and the HOMO level of Ir(dmpimpt-Me)3 (2.91 eV) is required for excitation. Accordingly, the light-emitting element 1 and the comparison light-emitting element 2 can emit light at a lower driving voltage than the comparison light-emitting element 3. <Messung des T1-Niveaus>

[0340] Next, in order to obtain the T1 level of the compound used in the light-emitting layer 130, a thin film of 4.6mCzP2Pm was formed over a quartz substrate by a vacuum evaporation method, and then the emission spectrum of this thin film was measured at a low temperature (10 K).

[0341] The measurement was performed using a PLD microscope, LabRAM HR-PLD, manufactured by HORIBA, Ltd., a He-Cd laser with a wavelength of 325 nm as excitation light and a CCD detector at a measurement temperature of 10 K.

[0342] In the emission spectrum measurement method, in addition to the normal emission spectrum measurement, a time-resolved emission spectrum measurement focusing on long-lifetime light emission was also performed. Since the measurement temperature was set to a low temperature (10 K) in this emission spectrum measurement method, phosphorescence was observed in addition to fluorescence, which is the main emission component, in the normal emission spectrum measurement. Furthermore, phosphorescence was mainly observed in the time-resolved emission spectrum measurement focusing on long-lifetime light emission. Fig. Figure 20 shows the time-resolved emission spectrum of 4.6mCzP2Pm measured at a low temperature.

[0343] As shown in the emission spectrum measurement results, the emission spectrum of 4.6mCzP2Pm exhibits a peak (including a shoulder) of the phosphorescent component on the shortest wavelength side at 459 nm.

[0344] Thus, the T1 level of 4.6mCzP2Pm was calculated to be 2.70 eV from the peak wavelength. <Absorptionsspektrum und Emissionsspektrum der Verbindung>

[0345] Next, Fig. 21 the measurement results of the absorption and emission spectra of Ir(dmpimpt-Me)3.

[0346] For the measurement of the absorption spectrum and the emission spectrum, a dichloromethane solution (1 × 10 -4 M) in which Ir(dmpimpt-Me)3 was dissolved, and a quartz cell was used. The absorption spectrum was measured using a UV-VIS spectrophotometer (V-550, manufactured by JASCO Corporation). The absorption spectra of the quartz cell and the solvent were subtracted from the measured spectrum of the solution. Note that the emission spectrum of the solution was measured using a PLD-EL meter (manufactured by Hamamatsu Photonics KK). The measurement was performed at room temperature (in an atmosphere maintained at 23 °C).

[0347] As in Fig. As shown in Figure 21, an absorption edge on the lowest energy side (the longest wavelength side) of the absorption spectrum of Ir(dmpimpt-Me)3 is located at approximately 450 nm. The absorption edge was obtained from absorption spectrum data, and the transition energy was estimated assuming a direct transition. The transition energy of Ir(dmpimpt-Me)3 was found to be 2.71 eV. Since Ir(dmpimpt-Me)3 is a phosphorescent compound, the absorption band on the lowest energy side is based on the transition from the triplet excited state. Thus, the T1 level of Ir(dmpimpt-Me)3 was calculated to be 2.71 eV.

[0348] According to the measurement results described above, it was found that the T1 level of 4,6mCzP2Pm is equal to the T1 level of Ir(dmpimpt-Me)3, and the T1 level of Ir(dmpimpt-Me)3 is higher than the T1 level (2.28 eV) of the exciplex formed by 4,6mCzP2Pm and Ir(dmpimpt-Me)3. Thus, the triplet excitation energy of the exciplex formed by 4,6mCzP2Pm and Ir(dmpimpt-Me)3 is not deactivated by 4,6mCzP2Pm or Ir(dmpimpt-Me)3. Thus, the triplet excitation energy of the exciplex can be converted into light, it can be converted into singlet excitation energy by reverse intersystem crossing, or it can be transferred to the fluorescent compound. (Luminescence quantum yield of the compound>

[0349] Next, the luminescence quantum yield of Ir(dmpimpt-Me)3 was measured. The luminescence quantum yield was determined using a toluene solution (1 × 10 -5 M) in which Ir(dmpimpt-Me)3 was dissolved, and an absolute quantum yield measurement system C9920-02 manufactured by Hamamatsu Photonics Corporation. The excitation wavelength ranged from 350 nm to 550 nm.

[0350] The measurement results show that the luminescence quantum yield of Ir(dmpimpt-Me)3 was 7%. Thus, it was found that Ir(dmpimpt-Me)3 is a light-emitting material with low luminescence quantum yield.

[0351] In contrast, the reference light-emitting element 2 emits light originating from the exciplex formed by 4,6mCzP2Pm and Ir(dmpimpt-Me)3, and it exhibits a higher luminous efficiency than the reference light-emitting element 3, which emits light originating from Ir(dmpimpt-Me)3. This is because the reference light-emitting element 2 emits light originating from triplet excitons, in addition to light originating from singlet excitons generated by recombination of carriers (holes and electrons) injected from the pair of electrodes, or light originating from singlet excitons generated by reverse intersystem crossing of triplet excitons in the exciplex. This means that even if a compound with a low luminescence quantum yield is used, a light-emitting element with high luminous efficiency can be obtained.

[0352] Furthermore, in the light-emitting element 1 of one embodiment of the present invention, energy of the singlet excitons and triplet excitons generated in the exciplex is supplied to TBRb, which is the fluorescent compound, and light emission is obtained from TBRb. Excitation energy of the exciplex is supplied to the fluorescent compound, and light is emitted from the fluorescent compound, whereby highly efficient light emission can be obtained with an emission spectrum with a narrow width and little efficiency reduction in a high luminance range.

[0353] One embodiment of the present invention can provide a light-emitting element with high emission efficiency. One embodiment of the present invention can also provide a light-emitting element with low drive voltage and reduced power consumption. [Example 2]

[0354] In this example, examples of the fabrication of the light-emitting element of one embodiment of the present invention and a comparative light-emitting element are shown. The structure of each of the light-emitting elements fabricated in this example is the same as that shown in Fig. 1. Table 3 shows details of the elemental structures. A structure and abbreviation of a compound used herein are also listed below. Please note that for the structures and abbreviations of the other compounds, please refer to Example 1. [Table 3] layer Reference symbol Film thickness (nm) material Weight ratio Light-emitting element 2 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 BPhen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 4.6mCzP2Pm : Ir(ppz)3 : TBRb 1:0,2:0,005 Hole transport layer 112 20 mCzFLP - Hole injection layer 111 60 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) 10 BPhen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 4.6mCzP2Pm : Ir(ppz)3 1:0,2 Hole transport layer 112 20 mCzFLP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 70 ITSO - <Herstellung der Licht emittierenden Elemente>

[0355] Methods for manufacturing the light-emitting elements of this example are described below. Light-emitting element 2 and comparative light-emitting element 4 were manufactured through the same steps as those of the above-described light-emitting element 1, except for the step of forming the light-emitting layer 130.

[0356] As the light-emitting layer 130 of the light-emitting element 2, 4,6mCzP2Pm, Tris[2-(1H-pyrazol-1-yl-κN 2 )phenyl-κC]iridium(III) (abbreviation: Ir(ppz)3) and TBRb were deposited by co-evaporation in a weight ratio of 1:0.2:0.005 (4.6mCzP2Pm:Ir(ppz)3:TBRb) to a thickness of 40 nm. In the light-emitting layer 130, Ir(ppz)3 corresponds to the first organic compound, 4.6mCzP2Pm corresponds to the second organic compound, and TBRb is a fluorescent compound corresponding to the third organic compound.

[0357] As the light-emitting layer 130 of the comparative light-emitting element 4, 4.6mCzP2Pm and Ir(ppz)3 were co-evaporated in a weight ratio of 1:0.2 (4.6mCzP2Pm:Ir(ppz)3) to a thickness of 40 nm. In the light-emitting layer 130, Ir(ppz)3 corresponds to the first organic compound, 4.6mCzP2Pm corresponds to the second organic compound, and the fluorescent compound corresponding to the third organic compound is not included. <Eigenschaften der Licht emittierenden Elemente>

[0358] Next, the characteristics of the fabricated light-emitting element 2 and the fabricated comparative light-emitting element 4 were measured. Note that the measurement method is similar to that used in Example 1.

[0359] Fig. Figure 22 shows the luminance-current density characteristics of the light-emitting element 2 and the comparative light-emitting element 4. Fig. 23 shows the luminance-voltage characteristics of these. Fig. 24 shows the power efficiency-luminance characteristics of these. Fig. 25 shows the power efficiency-luminance characteristics of these. Fig. Figure 26 shows the external quantum efficiency-luminance characteristics of these. Fig. Figure 27 shows the electroluminescence spectra of the light-emitting element 2 and the comparative light-emitting element 4, to which a current with a current density of 2.5 mA / cm 2 The measurements of the light-emitting elements were performed at room temperature (in an atmosphere maintained at 23 °C).

[0360] Table 4 shows the element properties of the light-emitting element 2 and the comparative light-emitting element 4 at about 1000 cd / m 2 . [Table 4] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x, y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) external quantum efficiency (%) Light-emitting element 2 3,60 1,31 (0,440, 0,536) 1000 76,2 66,5 22,9 Light-emitting reference element 4 3,60 1,42 (0,348, 0,585) 930 65,6 57,2 19,4

[0361] As in Fig. As shown in Figure 27, the electroluminescence spectrum of the light-emitting element 2 has a peak at a wavelength of 560 nm and a half-width at 80 nm. This indicates that the light-emitting element 2 emits yellow light. The light-emitting element 2 emits light originating from TBRb, which is the fluorescent compound. Note that Ir(ppz)3 used in the light-emitting element 2 is known to be a compound that emits blue light at a low temperature; however, light originating from Ir(ppz)3 was not observed.

[0362] The electroluminescence spectrum of the comparative light-emitting element 4 has a peak at a wavelength of 537 nm and a broad spectrum shape with a half-width of 94 nm. As described above, light emission from the comparative light-emitting element 4 originates from the exciplex formed by 4.6mCzP2Pm and Ir(ppz)3.

[0363] As in Fig. 22, Fig. 23, Fig. 24, Fig. 25, Fig. As shown in Figure 26 and Table 4, in the light-emitting element 2, the luminous efficiency (the current efficiency, the power efficiency, and the external quantum efficiency) is higher than that of the comparative light-emitting element 4. The light-emitting element 2 and the comparative light-emitting element 4 each have an external quantum efficiency of more than 7.5%. This is because the light-emitting element 2 and the comparative light-emitting element 4 each emit light originating from the triplet excitons or light originating from singlet excitons generated by reverse intersystem crossing of triplet excitons in the exciplex, in addition to light originating from singlet excitons generated by recombination of carriers (holes and electrons) injected from the pair of electrodes.In other words, the comparative light-emitting element 4 emits light originating from the exciplex, and the light-emitting element 2 is the light-emitting element of an embodiment of the present invention that utilizes ExEF.

[0364] Furthermore, the luminous efficiency drop (also referred to as roll-off) on the high luminance side of the light-emitting element 2 is smaller than that of the comparative light-emitting element 4. The luminous efficiency (current efficiency, power efficiency, and external quantum efficiency) is high even in a high luminance range. That is, a feature of the light-emitting element of one embodiment of the present invention is that roll-off is less likely to occur than in the light-emitting element that emits light originating from the exciplex. <Ergebnisse der CV-Messung>

[0365] The electrochemical properties (oxidation reaction properties and reduction reaction properties) of the above compound were measured by cyclic voltammetry (CV). Note that the measurement method is similar to that used in Example 1. Furthermore, for the measurement results of 4.6mCzP2Pm, reference can be made to Example 1.

[0366] According to the CV measurement results, the oxidation potential and reduction potential of Ir(ppz)3 were 0.45 V and -3.17 V, respectively. Furthermore, the HOMO and LUMO levels of Ir(ppz)3, calculated from the CV measurement results, were -5.39 eV and -1.77 eV, respectively. Thus, it was found that Ir(ppz)3 has a high HOMO level.

[0367] As described above, the LUMO level of 4,6mCzP2Pm is lower than that of Ir(ppz)3, and the HOMO level of Ir(ppz)3 is higher than that of 4,6mCzP2Pm. Thus, in the case where the compounds are used in a light-emitting layer, as in the light-emitting element 2, electrons and holes serving as charge carriers are efficiently injected from a pair of electrodes into 4,6mCzP2Pm and Ir(ppz)3, respectively, so that 4,6mCzP2Pm and Ir(ppz)3 can form an exciplex.

[0368] The exciplex formed by 4,6mCzP2Pm and Ir(ppz)3 has the LUMO level in 4,6mCzP2Pm and the HOMO level in Ir(ppz)3. The energy difference between the LUMO level of 4,6mCzP2Pm and the HOMO level of Ir(ppz)3 is 2.51 eV. This value is essentially the same as the light emission energy (2.31 eV) obtained from the peak wavelength of the electroluminescence spectrum of the reference light-emitting element 4 in Fig. 27. This result implies that the electroluminescence spectrum of the reference light-emitting element 4 corresponds to the light emission from the exciplex formed by 4.6mCzP2Pm and Ir(ppz)3. In the exciplex, the difference between the S1 level and the T1 level is small, thus the light emission energy can be considered as the energy of the S1 level and the T1 level (2.31 eV).

[0369] As in Fig. As shown in Figure 29, the absorption spectrum of TBRb exhibits an absorption band with a high molar absorption coefficient at approximately 450 nm to 550 nm. This absorption band has a region overlapping with the electroluminescence spectrum of the exciplex of comparative light-emitting element 4 (the exciplex formed by 4,6mCzP2Pm and Ir(ppz)3). Thus, the excitation energy can be efficiently transferred from the exciplex formed by 4,6mCzP2Pm and Ir(ppz)3 to TBRb, which is the fluorescent compound.

[0370] Furthermore, the light emission energy of TBRb of the light-emitting element 2 is lower than that of the exciplex of the comparative light-emitting element 4 (the exciplex formed by 4,6mCzP2Pm and Ir(ppz)3). Therefore, it can be concluded that in the light-emitting element 2, the excitation energy can be efficiently transferred from the exciplex formed by 4,6mCzP2Pm and Ir(ppz)3 to TBRb, which is the fluorescent compound. As a result, the light-emitting element 2 can achieve high-efficiency light emission from TBRb.

[0371] The excitation energy level of the exciplex formed by 4.6mCzP2Pm and Ir(ppz)3 is lower than the energy difference between the LUMO and HOMO levels of 4.6mCzP2Pm (3.01 eV). Therefore, when the exciplex is formed, a low-voltage light-emitting device can be obtained. <Absorptionsspektrum der Verbindung>

[0372] Fig. Figure 28 shows the measurement results of the absorption spectrum of Ir(ppz)3.

[0373] For the measurement of the absorption spectrum, a dichloromethane solution (1 × 10 -4 M) in which Ir(ppz)3 was dissolved, and a quartz cell was used. The absorption spectrum was measured using a UV-VIS spectrophotometer (V-550, manufactured by JASCO Corporation). The absorption spectra of the quartz cell and the solvent were subtracted from the measured spectrum of the solution. The measurement was carried out at room temperature (in an atmosphere maintained at 23 °C).

[0374] As in Fig. As shown in Figure 28, an absorption edge on the lowest energy side (the longest wavelength side) of the absorption spectrum of Ir(ppz)3 is located at approximately 370 nm. The absorption edge was obtained from absorption spectrum data, and the transition energy was estimated assuming a direct transition. The transition energy of Ir(ppz)3 was found to be 3.27 eV. Since Ir(ppz)3 is a phosphorescent compound, the absorption band on the lowest energy side is based on the transition from the triplet excited state. Thus, the T1 level of Ir(ppz)3 was calculated from the absorption edge to be 3.27 eV.

[0375] According to the measurement results described above, it was found that the T1 level of 4,6mCzP2Pm is lower than the T1 level of Ir(ppz)3, and the T1 level of 4,6mCzP2Pm is higher than the T1 level of the exciplex (2.28 eV) formed by 4,6mCzP2Pm and Ir(ppz)3. Thus, the triplet excitation energy of the exciplex formed by 4,6mCzP2Pm and Ir(ppz)3 is not deactivated by 4,6mCzP2Pm or Ir(ppz)3. Thus, the triplet excitation energy of the exciplex can be converted into light, can be converted into singlet excitation energy by reverse intersystem crossing, or can be transferred to the fluorescent compound.

[0376] Furthermore, when measuring the emission spectrum of Ir(ppz)3 at room temperature, no light emitted by Ir(ppz)3 was observed. Non-Patent Document 1 discloses that the luminescence quantum yield of Ir(ppz)3 at room temperature is lower than 1%. This suggests that Ir(ppz)3 is a material that does not emit light at room temperature.

[0377] In contrast, the comparative light-emitting element 4, which emits light originating from the exciplex formed by 4.6mCzP2Pm and Ir(ppz)3, exhibits a high external quantum efficiency that is 20% higher. This is because the comparative light-emitting element 4 emits light originating from triplet excitons, in addition to light originating from singlet excitons generated by recombination of carriers (holes and electrons) injected from the pair of electrodes, or light originating from singlet excitons generated by reverse intersystem crossing of triplet excitons in the exciplex. This means that even when a compound with a low luminescence quantum yield, i.e., a luminescence quantum yield of less than 1%, is used, a light-emitting element with high luminescence efficiency can be obtained.

[0378] Furthermore, in the light-emitting element 2 of one embodiment of the present invention, energy of the singlet excitons generated in the exciplex is supplied to TBRb, which is the fluorescent compound, and light emission is obtained from TBRb. Excitation energy of the exciplex is supplied to the fluorescent compound, and light is emitted from the fluorescent compound, whereby highly efficient light emission can be obtained with an emission spectrum with a narrow width and little efficiency reduction in the high luminance region.

[0379] One embodiment of the present invention can provide a light-emitting element with high emission efficiency. One embodiment of the present invention can also provide a light-emitting element with low drive voltage and reduced power consumption. [Example 3]

[0380] This example shows examples of the fabrication of the light-emitting element of one embodiment of the present invention and a comparative light-emitting element. Table 5 shows details of the element structures. Structures and abbreviations of the compounds used herein are also listed below. Note that for the structures and abbreviations of the other compounds, reference is made to Examples 1 and 2. [Table 5] layer Reference symbol Film thickness (nm) material Weight ratio Light-emitting element 3 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 10 BPhen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 4.6mCzP2Pm : Ir(ppz)3:TBRb 1:0,1:0,005 Hole transport layer 112 20 mCzFLP - Hole injection layer 111 60 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) 10 BPhen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 4.6mCzP2Pm : Ir(ppz)3 1:0,1 Hole transport layer 112 20 mCzFLP - Hole injection layer 111 60 DBT3P-II : MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting reference element 6 electrode 102 200 Al - Electron injection layer 119 1 LiF - Electron transport layer 118(2) 15 NBPhen - 118(1) 20 4.6mCzP2Pm - Light-emitting layer 130 40 4.6mCzP2Pm : PCBiF 0,8:0,2 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 40 DBT3P-II : MoO3 1:0,5 electrode 101 70 ITSO - <Herstellung der Licht emittierenden Elemente>

[0381] Methods for manufacturing the light-emitting elements of this example are described below. Light-emitting element 3 and comparative light-emitting element 5 were manufactured through the same steps as those of the above-described light-emitting element 1, except for the step of forming the light-emitting layer 130.

[0382] As the light-emitting layer 130 of the light-emitting element 3, 4.6mCzP2Pm, Ir(ppz)3, and TBRb were co-evaporated in a weight ratio of 1:0.1:0.005 (4.6mCzP2Pm:Ir(ppz)3:TBRb) to a thickness of 40 nm. In the light-emitting layer 130, Ir(ppz)3 corresponds to the first organic compound, 4.6mCzP2Pm corresponds to the second organic compound, and TBRb is a fluorescent compound corresponding to the third organic compound.

[0383] As the light-emitting layer 130 of the comparative light-emitting element 5, 4.6mCzP2Pm and Ir(ppz)3 were co-evaporated in a weight ratio of 1:0.1 (4.6mCzP2Pm:Ir(ppz)3) to a thickness of 40 nm. In the light-emitting layer 130, Ir(ppz)3 corresponds to the first organic compound, 4.6mCzP2Pm corresponds to the second organic compound, and a fluorescent compound corresponding to the third organic compound is not included. <Herstellung des Licht emittierenden Vergleichselements 6>

[0384] As electrode 101, an ITSO film with a thickness of 70 nm was formed over a glass substrate. The electrode area of electrode 101 was 4 mm 2 (2 mm × 2 mm).

[0385] As hole injection layer 111, DBT3P-II and molybdenum oxide (MoO3) were deposited by co-evaporation in a weight ratio of 1:0.5 (DBT3P-II: MoO3) in a thickness of 40 nm over the electrode 101.

[0386] As hole transport layer 112, 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP) was deposited by evaporation in a thickness of 20 nm over the hole injection layer 111.

[0387] As the light-emitting layer 130, 4,6mCzP2Pm and N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine (abbreviation: PCBiF) were deposited by co-evaporation over the hole transport layer 112 in a weight ratio of 0.8:0.2 (4,6mCzP2Pm:PCBiF) to a thickness of 40 nm.

[0388] As the electron-transport layer 118, 4.6mCzP2Pm and Bphen were successively deposited by evaporation to a thickness of 20 nm and 15 nm, respectively, over the light-emitting layer 130. As the electron-injection layer 119, LiF was then deposited by evaporation to a thickness of 1 nm over the electron-transport layer 118.

[0389] As electrode 102, aluminum (Al) was formed in a thickness of 200 nm over the electron injection layer 119.

[0390] Next, the electrodes and the EL layer were sealed in a nitrogen-filled glove box by attaching a glass substrate for sealing to the glass substrate on which the organic materials were deposited using a sealant for an organic EL device. Specifically, after the sealant was applied to enclose the organic materials deposited on the glass substrate and the glass substrate was attached to the glass substrate for sealing, irradiation with UV light with a wavelength of 365 nm at 6 J / cm 2 and a heat treatment at 80 °C for one hour. This process yielded the light-emitting reference element 6. <Eigenschaften der Licht emittierenden Elemente>

[0391] Next, the characteristics of the fabricated light-emitting element 3 and the fabricated comparative light-emitting elements 5 and 6 were measured. Note that the measurement method is similar to that used in Example 1.

[0392] Fig. 30 shows the external quantum efficiency-luminance characteristics of the light-emitting element 3 and the comparative light-emitting elements 5 and 6. Fig. Figure 31 shows the electroluminescence spectra of the light-emitting element 3 and the comparative light-emitting elements 5 and 6, to which a current with a current density of 2.5 mA / cm 2 The measurements of the light-emitting elements were performed at room temperature (in an atmosphere maintained at 23 °C).

[0393] Table 6 shows the element properties of the light-emitting element 3 and the comparative light-emitting elements 5 and 6 at about 1000 cd / m 2 . [Table 6] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x, y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) external quantum efficiency (%) Light-emitting element 3 3,60 1,45 (0,426, 0,538) 905 62,3 54,4 18,9 Light-emitting reference element 5 3,60 1,57 (0,327, 0,580) 970 61,3 53,2 18,6 Light-emitting reference element 6 3,60 2,05 (0,402, 0,570) 910 44,5 38,8 13,2

[0394] As in Fig. As shown in Figure 31, the electroluminescence spectra of comparative light-emitting elements 5 and 6 have peaks at wavelengths of 526 nm and 548 nm, respectively, and broad spectrum shapes with half-widths of 95 nm and 91 nm, respectively. This indicates that comparative light-emitting elements 5 and 6 emit yellow light. As described above, the light emission obtained from comparative light-emitting element 5 is light emission from the exciplex formed by 4,6mCzP2Pm and Ir(ppz)3. Further, the electroluminescence spectrum of light-emitting element 3 has a peak at a wavelength of 558 nm and a half-width of 84 nm. This indicates that light-emitting element 3 emits yellow light. The light-emitting element 3 emits light originating from TBRb, which is the fluorescent compound.It should be noted that Ir(ppz)3 is known to be a compound that emits blue light at a low temperature; however, light originating from Ir(ppz)3 has not been observed.

[0395] The light emission energy calculated from the peak wavelength of the light emission obtained from the comparative light-emitting element 6 is 2.26 eV. This value is substantially equal to the energy difference (2.38 eV) between the LUMO level of 4.6mCzP2Pm (-2.88 eV) and the HOMO level of PCBiF (-5.26 eV) calculated by the CV measurement described in Example 1. Therefore, it can be stated that the light emission obtained from the comparative light-emitting element 6 is the light emission originating from the exciplex formed by 4.6mCzP2Pm and PCBiF in the light-emitting layer.

[0396] As in Fig. 31, the external quantum efficiency of the comparative light-emitting element 5 is higher than that of the comparative light-emitting element 6. Furthermore, the external quantum efficiency of the comparative light-emitting element 5 is substantially the same as that of the light-emitting element 3. The light-emitting element 3 has a structure of the comparative light-emitting element 5 in which the light-emitting layer further contains TBRb, which is the fluorescent compound. Thus, it is highly likely that the comparative light-emitting element 5, which has a high efficiency, contributes to the high efficiency of the light-emitting element 3. This indicates that the excitation energy can be efficiently transferred from the exciplex in the comparative light-emitting element 5 to TBRb, which is the fluorescent compound. <Transiente EL-Messung der Dünnfilme>

[0397] Next, light-emitting element 3 and light-emitting elements 5 and 6 were subjected to transient EL measurement. A picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics KK) was used for the measurement. To measure the fluorescence lifetime of the light-emitting elements, a pulse voltage with a square wave was applied to the light-emitting elements, and a time-resolved measurement of light attenuated by the voltage drop was performed using a streak camera. The pulse voltage was applied at a frequency of 10 Hz. By integrating data obtained through repeated measurements, data with a high S / N ratio were obtained.The measurement was conducted at room temperature (300 K) under the conditions of a pulse voltage of approximately 3 V, a pulse time width of 100 µs, a negative bias of -5 V, and a measurement time of 20 µs for the light-emitting element 3 and the comparison light-emitting element 5, and 50 µs for the comparison light-emitting element 6. Fig. 32 shows the results.

[0398] As in Fig. As shown in Figure 32, the comparative light-emitting element 6 contains a large proportion of delayed fluorescent components, and the emission lifetime is very long. In contrast, the proportion of delayed fluorescent components contained in the comparative light-emitting element 5 is not large; however, as shown in Fig. 30, the external quantum efficiency of the comparative light-emitting element 5 is higher than that of the comparative light-emitting element 6. Furthermore, as shown in Fig. As shown in Figure 32, the emission lifetime of the reference light-emitting element 5 is very short. This indicates that the excited state is deactivated to the ground state in a short time. Such a light-emitting element with a short emission lifetime is very reliable, which is preferable. It is very likely that since the reference light-emitting element 5 contains Ir, which is a heavy atom, in the material used for the exciplex, the behavior of the exciplex in the reference light-emitting element 5 is different from those of the exciplex formed using normal host materials and the TADF material.

[0399] The light-emitting element 3 of an embodiment of the present invention, in which the comparative light-emitting element 5 is used as a medium for energy transmission, has, as shown in Fig. 32, exhibits a shorter emission lifetime than that of the comparative light-emitting element 5. This also indicates that the excitation energy is efficiently transferred from the exciplex in the comparative light-emitting element 5 to TBRb, which is the fluorescent compound. Thus, it is very likely that as the emission lifetime becomes shorter, reliability will be improved.

[0400] One embodiment of the present invention can provide a light-emitting element with high emission efficiency. One embodiment of the present invention can also provide a highly reliable light-emitting element. Reference symbol

[0401] 100: EL layer, 101: Electrode, 101a: Conductive layer, 101b: Conductive layer, 102: Electrode, 103: Electrode, 103a: Conductive layer, 103b: Conductive layer, 104: Electrode, 104a: Conductive layer, 104b: Conductive layer, 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, 123B: Light-emitting layer, 123G: Light-emitting layer, 123R: Light-emitting Layer, 130: Light-emitting layer, 131: Junction, 132: Junction, 133: Junction, 134: Junction, 140: Light-emitting layer, 140a: Light-emitting layer, 140b: Light-emitting layer, 145: Partition, 150: Light-emitting element, 200: Substrate, 220: Substrate, 221B: Region, 221G: Region, 221R: Region,222B: region, 222G: region, 222R: region, 223: light-proof layer, 224B: optical element, 224G: optical element, 224R: optical element, 250: light-emitting element, 260: light-emitting element, 262a: light-emitting element, 262b: light-emitting element, 600: display device, 601: signal line driver circuit section, 602: pixel section, 603: scanning line driver circuit section, 604: sealing substrate, 605: sealing agent, 607: region, 608: line, 609: FPC, 610: element substrate, 611: transistor, 612: transistor, 613: lower electrode, 614: partition wall, 616: EL layer, 617: upper electrode, 618: light-emitting element, 621: optical element, 622: opaque layer, 623: transistor, 624: transistor, 1001: substrate, 1002: base insulating film, 1003: gate insulating film, 1006: gate electrode, 1007: gate electrode, 1008: gate electrode, 1020: interlayer insulating film, 1021: interlayer insulating film, 1022: electrode,1024B: lower electrode, 1024G: lower electrode, 1024R: lower electrode, 1025: partition wall, 1026: upper electrode, 1028: EL layer, 1029: sealing layer, 1031: sealing substrate, 1032: sealant, 1033: base material, 1034B: color layer, 1034G: color layer, 1034R: color layer, 1035: light-blocking layer, 1036: cap layer, 1037: interlayer insulating film, 1040: pixel portion, 1041: driving circuit portion, 1042: peripheral portion, 3000: light-emitting device, 3001: substrate, 3003: substrate, 3005: light-emitting Element, 3007: Sealing area, 3009: Sealing area, 3011: Area, 3013: Area, 3018: Desiccant, 8000: Display module, 8001: Top cover, 8002: Bottom cover, 8003: FPC, 8004: Touch sensor, 8005: FPC, 8006: Display device, 8009: Frame, 8010: Printed circuit board, 8011: Battery, 8501: Lighting device, 8502: Lighting device, 8503: Lighting device, 8504: Lighting device,9000: Housing, 9001: Display section, 9003: Speaker, 9005: Operation button, 9006: Connection terminal, 9007: Sensor, 9008: Microphone, 9050: Operation button, 9051: Information, 9052: Information, 9053: Information, 9054: Information, 9055: Joint, 9100: Portable information terminal, 9101: Portable information terminal, 9102: Portable information terminal, 9200: Portable information terminal, 9201: Portable information terminal.,< / beleuchtungsvorrichtung> < / anzeigemodul> < / substrat> < / elektroneninjektionsschicht> < / elektronentransportschicht> < / lochtransportschicht> < / lochinjektionsschicht> < / material>

Claims

[1] Light-emitting element comprising: a light-emitting layer, wherein the light-emitting layer comprises a first organic compound, a second organic compound and a third organic compound, wherein a LUMO level of one of the first organic compound and the second organic compound is higher than a LUMO level of the other of the first organic compound and the second organic compound, wherein a HOMO level of one of the first organic compound and the second organic compound is higher than a HOMO level of the other of the first organic compound and the second organic compound, wherein the first organic compound and the second organic compound in combination may form an exciplex, wherein the first organic compound can convert triplet excitation energy into light emission at room temperature, wherein the third organic compound can convert singlet excitation energy into light emission, and wherein light emitted by the light-emitting layer comprises light emitted by the third organic compound. [2] Light-emitting element comprising: a light-emitting layer, wherein the light-emitting layer comprises a first organic compound, a second organic compound and a third organic compound, wherein a LUMO level of one of the first organic compound and the second organic compound is higher than a LUMO level of the other of the first organic compound and the second organic compound, wherein a HOMO level of one of the first organic compound and the second organic compound is higher than a HOMO level of the other of the first organic compound and the second organic compound, wherein the first organic compound and the second organic compound in combination may form an exciplex, wherein the first organic compound cannot emit fluorescent light at room temperature, but can emit phosphorescent light, wherein the third organic compound can emit fluorescent light, and wherein light emitted by the light-emitting layer comprises light emitted by the third organic compound. [3] Light-emitting element comprising: a light-emitting layer, wherein the light-emitting layer comprises a first organic compound, a second organic compound and a third organic compound, wherein a LUMO level of the first organic compound is higher than a LUMO level of the second organic compound, wherein a HOMO level of the first organic compound is higher than a HOMO level of the second organic compound, wherein the first organic compound and the second organic compound in combination may form an exciplex, wherein the first organic compound comprises Ru, Rh, Pd, Os, Ir or Pt, and wherein light emitted by the light-emitting layer comprises light emitted by the third organic compound. [4] The light-emitting element according to any one of claims 1 to 3, wherein a lowest triplet excitation energy level of the first organic compound is higher than or equal to a lowest triplet excitation energy level of the second organic compound. [5] The light-emitting element according to any one of claims 1 to 3, wherein the exciplex can supply excitation energy to the third organic compound. [6] The light-emitting element according to claim 5, wherein an emission spectrum of the exciplex includes a region overlapping with an absorption band on the longest wavelength side in an absorption spectrum of the third organic compound. [7] The light-emitting element according to any one of claims 1 to 3, wherein the first organic compound comprises iridium. [8] Light-emitting element according to claim 7, wherein the first organic compound comprises a ligand coordinated to iridium, and wherein the ligand comprises a five-membered nitrogen-containing heterocyclic framework. [9] The light-emitting element according to any one of claims 1 to 3, wherein the second organic compound comprises a π-electron-deficient heteroaromatic framework. [10] The light-emitting element according to any one of claims 1 to 3, wherein the first organic compound has a luminescence quantum efficiency of higher than or equal to 0% and lower than or equal to 40% at room temperature. [11] The light-emitting element according to any one of claims 1 to 3, wherein the luminous efficiency of the light emitted from the exciplex is higher than the luminous efficiency of the light emitted from the first organic compound. [12] Display device comprising: the light-emitting element according to any one of claims 1 to 3; and at least one of a color filter and a transistor.

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