Light-emitting device

Abstract

To provide a light-emitting element which has low driving voltage and high emission efficiency.SOLUTION: A light-emitting element includes, between a pair of electrodes, a hole-transport layer and a light-emitting layer formed over the hole-transport layer. The light-emitting layer contains a first organic compound having an electron-transport property, a second organic compound having a hole-transport property, and a light-emitting third organic compound converting triplet excitation energy into light emission. A combination of the first organic compound and the second organic compound forms an exciplex. The hole-transport layer contains at least a fourth organic compound whose HOMO level is lower than or equal to that of the second organic compound and a fifth organic compound whose HOMO level is higher than that of the second organic compound.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] One aspect of the present invention relates to a light-emitting element in which an organic compound that emits light when an electric field is applied is sandwiched between a pair of electrodes, a light-emitting device having such a light-emitting element, an electronic device, and a lighting device. And a lighting device.

Background Art

[0002] A light-emitting element using an organic compound having characteristics such as thinness, light weight, high-speed responsiveness, and driving at a low DC voltage as a light-emitting body is expected to be applied to next-generation flat panel displays. In particular, a display device in which light-emitting elements are arranged in a matrix is considered to have an advantage in that it has a wider viewing angle and better visibility compared to a conventional liquid crystal display device.

[0003] The light-emitting mechanism of the light-emitting element is as follows: when a voltage is applied across a light-emitting layer containing a light-emitting body between a pair of electrodes, electrons injected from the cathode and holes injected from the anode recombine at the light-emitting center of the light-emitting layer to form molecular excitons, and when the molecular excitons relax to the ground state, they emit energy and emit light. It is known that there are a singlet excited state and a triplet excited state in the excited state, and it is considered that light emission can occur through either excited state. Light emission from the singlet excited state (S ) is called fluorescence, and light emission from the triplet excited state (T ) is called phosphorescence. * ) is called fluorescence, and light emission from the triplet excited state (T * ) is called phosphorescence.

[0004] Regarding such a light-emitting element, in order to improve its element characteristics, improvements in the element structure and material development are actively carried out (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] As reported in Patent Document 1, although improvements such as in the element structure have progressed, there is still room for improvement in terms of luminous efficiency, reliability, and emission characteristics, and the development of a more excellent light-emitting element is desired.

[0007] Therefore, one aspect of the present invention aims to provide a light-emitting element with a low driving voltage and high luminous efficiency.

Means for Solving the Problems

[0008] One aspect of the present invention has a hole transport layer between a pair of electrodes and a light-emitting layer formed on the hole transport layer, and the light-emitting layer has a first organic compound having electron-transporting properties, a second organic compound having hole-transporting properties, and a third light-emitting organic compound that converts triplet excitation energy into light emission, and the first organic compound and the second organic compound are a combination that forms an exciplex, and the hole transport layer has a fourth organic compound at least below the HOMO level of the second organic compound and a fifth organic compound having a higher HOMO level than the second organic compound, and is characterized by being a light-emitting element.

[0009] Further, another aspect of the present invention has a hole injection layer between a pair of electrodes, a hole transport layer formed on the hole injection layer, a light-emitting layer formed on the hole transport layer, an electron transport layer formed on the light-emitting layer, and an electron injection layer formed on the electron transport layer, and the light-emitting layer has a first having electron-transporting properties​ An organic compound of 1, a second organic compound having hole-transporting properties, and a third organic compound having luminescence properties that converts triplet excitation energy into light, and the first organic compound and the second organic compound are a combination that forms an exciplex, and the hole-transporting layer contains at least a fourth organic compound having a HOMO level equal to or lower than that of the second organic compound and a fifth organic compound having a higher HOMO level than that of the second organic compound A light-emitting device characterized by having. In each of the above configurations, it is preferable to use the first organic compound as a host material, the second organic compound as an assist material, and the third organic compound as a guest material. That is, it is preferable that the mass fraction (or volume fraction) of the third organic compound in the light-emitting layer is smaller than that of the first organic compound and the second organic compound.

[0010] In addition, in each of the above configurations, the emission wavelength of the exciplex formed by the first organic compound (host material) and the second organic compound (assist material) is longer than the emission wavelengths (fluorescence wavelengths) of the first organic compound (host material) and the second organic compound (assist material) respectively. Therefore, the fluorescence spectrum of the first organic compound (host material) and the fluorescence spectrum of the second organic compound (assist material) can be converted into an emission spectrum located on the longer wavelength side. Therefore, the light-emitting device according to one aspect of the present invention forms an exciplex in the light-emitting layer, whereby the emission spectrum of the exciplex existing on the longer wavelength side than the emission wavelengths (fluorescence wavelengths) of the first organic compound (host material) and the second organic compound (assist material) respectively, and the third

[0011] Also, in each of the above configurations, the emission wavelength of the exciplex formed by the first organic compound (host material) and the second organic compound (assist material) is on the longer wavelength side compared to the emission wavelengths (fluorescence wavelengths) of the first organic compound (host material) and the second organic compound (assist material) respectively. Therefore, the fluorescence spectrum of the first organic compound (host material) and the fluorescence spectrum of the second organic compound (assist material) can be converted into an emission spectrum located on the longer wavelength side.

[0012] Thus, the light-emitting device according to one aspect of the present invention forms an exciplex in the light-emitting layer, whereby the emission spectrum of the exciplex existing on the longer wavelength side than the emission wavelengths (fluorescence wavelengths) of the first organic compound (host material) and the second organic compound (assist material) respectively, and the third Energy transfer can be carried out by utilizing the overlap with the absorption spectrum of the organic compound (guest material), and a light-emitting device with high energy transfer efficiency and high luminous efficiency can be realized. It is possible.

[0013] Further, in the hole transport layer, the hole transport layer has at least a fourth organic compound below the HOMO level of the second organic compound (assist material) and a fifth organic compound having a higher HOMO level than the second organic compound (assist material). When holes are injected from the fourth organic compound in the hole transport layer into the second organic compound (assist material) in the light-emitting layer, the holes can easily enter the inside of the light-emitting layer, and the luminous efficiency can be increased. In addition, since the fifth organic compound in the hole transport layer has a higher HOMO level than the second organic compound (assist material), the driving voltage (also simply referred to as voltage) of the light-emitting layer, particularly the driving start voltage, can be lowered. This effect is an effect obtained only when the hole transport layer has two or more of the above organic compounds and in the relationship of the above HOMO levels.

[0014] Further, in each of the above configurations, it is preferable that the fourth organic compound has a higher lowest triplet excitation energy level (T level) than the first organic compound and the second organic compound. By adopting such a configuration, the diffusion of the triplet excitation energy of the light-emitting layer to the hole transport layer can be suppressed, so that the luminous efficiency of the device can be increased. In order to prevent the triplet excitation energy of the light-emitting layer from diffusing to the hole transport layer, the mass fraction (or volume fraction) of the fourth organic compound in the hole transport layer is preferably 20% or more (less than 100%). 1

[0015] ​​​​​​​​​​​​​In addition, in each of the above configurations, it is preferable that the first organic compound (host material) is a π-deficient heteroaromatic compound, the second organic compound (assist material) is a π-excessive heteroaromatic compound or an aromatic amine compound, and the third organic compound (guest material) is a phosphorescent compound. The present invention also includes, within its scope, a light-emitting device having a light-emitting element, an electronic device having the light-emitting device, and a lighting device. Therefore, the light-emitting device as used herein refers to an image display device or a light source (including a lighting device). Further, the light-emitting device includes all modules having a connector, such as an FPC (Flexible Printed Circuit), a TAB (Tape Automated Bonding) tape, or a TCP (Tape Carrier Package) attached thereto, modules having a printed wiring board provided at the tip of a TAB tape or a TCP, or modules having an IC (integrated circuit) directly mounted on a light-emitting element by a COG (Chip On Glass) method.

Advantages of the Invention

[0016] One aspect of the light-emitting element of the present invention can perform energy transfer by utilizing the overlap between the emission spectrum of an exciplex existing on the longer wavelength side than the emission wavelength (fluorescence wavelength) of each of the first organic compound (host material) and the second organic compound (assist material) and the absorption spectrum of the third organic compound (guest material) in the light-emitting layer. Therefore, a light-emitting element with high energy transfer efficiency and high luminous efficiency can be realized.

[0017] ​​​​​​​​​​​​​​​​

Brief Description of the Drawings

[0018]

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Mode for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and its form and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention is not interpreted as being limited to the content of the embodiments shown below.

[0020] Note that the position, size, range, etc. of each component shown in the drawings, etc. may not represent the actual position, size, range, etc. for the sake of easy understanding. For this reason, the disclosed invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings, etc.

[0021] Note that ordinal numbers such as "first", "second", "third", etc. in this specification, etc. are added to avoid confusion of components, and it is noted that they are not numerically limiting.

[0022] (Embodiment 1) In this embodiment, the concept of constructing a light-emitting element, which is one aspect of the present invention, and the configuration of a specific light-emitting element will be described. First, the element structure of the light-emitting element, which is one aspect of the present invention, will be described with reference to FIG. 1.

[0023] ​​​The device structure shown in FIG. 1 has a hole between a pair of electrodes (the first electrode 101 and the second electrode 103). It has a hole transport layer 112 and a light-emitting layer 113 formed on the hole transport layer 112. The light-emitting layer 11 3 has a first organic compound 120 having electron-transporting properties, a second organic compound 122 having hole-transporting properties, and a third organic compound 124 having light-emitting properties that converts triplet excitation energy into light. The first organic compound 120 and the second organic compound 122 are a combination that forms an exciplex. The hole transport layer 112 has at least a fourth organic compound 126 below the HOMO level of the second organic compound 122 and a fifth organic compound 128 having a higher HOMO level than the second organic compound 122. That is, they are a combination that forms an exciplex. The hole transport layer 112 has at least a fourth organic compound 126 below the HOMO level of the second organic compound 122 and a fifth organic compound 128 having a higher HOMO level than the second organic compound 122. In FIG. 1, in the region provided between the first electrode 101 and the hole transport layer 112, a hole injection layer or a hole transport layer can be formed as needed. Also, in FIG. 1, in the region provided between the second electrode 103 and the light-emitting layer 113, an electron injection layer or an electron transport layer can be formed as needed. In FIG. 1, in the region provided between the first electrode 101 and the hole transport layer 112, a hole injection layer or a hole transport layer can be formed as needed. Also, in FIG. 1, in the region provided between the second electrode 103 and the light-emitting layer 113, an electron injection layer or an electron transport layer can be formed as needed. It is preferable to use the first organic compound 120 as a host material, the second organic compound 122 as an assist material, and the third organic compound 124 as a guest material. That is, it is preferable that the mass fraction (or volume fraction) of the third organic compound in the light-emitting layer is less than that of the first organic compound and the second organic compound. In the following description, the first organic compound 120 may be referred to as a host material, the second organic compound 122 as an assist material, and the third organic compound 124 as a guest material.

[0024] In FIG. 1, in the region provided between the first electrode 101 and the hole transport layer 112, a hole injection layer or a hole transport layer can be formed as needed. Also, in FIG. 1, in the region provided between the second electrode 103 and the light-emitting layer 113, an electron injection layer or an electron transport layer can be formed as needed. In FIG. 1, in the region provided between the first electrode 101 and the hole transport layer 112, a hole injection layer or a hole transport layer can be formed as needed. Also, in FIG. 1, in the region provided between the second electrode 103 and the light-emitting layer 113, an electron injection layer or an electron transport layer can be formed as needed. In FIG. 1, in the region provided between the second electrode 103 and the light-emitting layer 113, an electron injection layer or an electron transport layer can be formed as needed. In FIG. 1, in the region provided between the second electrode 103 and the light-emitting layer 113, an electron injection layer or an electron transport layer can be formed as needed.

[0025] It is preferable to use the first organic compound 120 as a host material, the second organic compound 122 as an assist material, and the third organic compound 124 as a guest material. That is, it is preferable that the mass fraction (or volume fraction) of the third organic compound in the light-emitting layer is less than that of the first organic compound and the second organic compound. In the following description, the first organic compound 120 may be referred to as a host material, the second organic compound 122 as an assist material, and the third organic compound 124 as a guest material. That is, it is preferable that the mass fraction (or volume fraction) of the third organic compound in the light-emitting layer is less than that of the first organic compound and the second organic compound. In the following description, the first organic compound 120 may be referred to as a host material, the second organic compound 122 as an assist material, and the third organic compound 124 as a guest material. That is, it is preferable that the mass fraction (or volume fraction) of the third organic compound in the light-emitting layer is less than that of the first organic compound and the second organic compound. In the following description, the first organic compound 120 may be referred to as a host material, the second organic compound 122 as an assist material, and the third organic compound 124 as a guest material. That is, it is preferable that the mass fraction (or volume fraction) of the third organic compound in the light-emitting layer is less than that of the first organic compound and the second organic compound. In the following description, the first organic compound 120 may be referred to as a host material, the second organic compound 122 as an assist material, and the third organic compound 124 as a guest material. In the following description, the first organic compound 120 may be referred to as a host material, the second organic compound 122 as an assist material, and the third organic compound 124 as a guest material. In the following description, the first organic compound 120 may be referred to as a host material, the second organic compound 122 as an assist material, and the third organic compound 124 as a guest material.

[0026] The first organic compound 120 (host material) is, for example, 10-6 cm 2 An electron transporting material having an electron mobility of / Vs or more can be used. Further, the second organic compound 122 (assist material) is, for example, a hole transporting material having a hole mobility of 10 cm / Vs or more. -6 cm 2 A hole transporting material having a hole mobility of / Vs or more can be used.

[0027] In the above configuration, the lowest triplet excitation energy levels (T levels) of the first organic compound 120 (host material) and the second organic compound 122 (assist material) are 1 preferably higher than the T level of the third organic compound 124 (guest material). If the T 1 levels of the first organic compound 120 (host material) and the second organic compound 122 (assist material) are lower than the T level of the third organic compound 124 (guest material), the triplet excitation energy of the third organic compound 124 (guest material) contributing to light emission is quenched by the first organic compound 12 1 0 (host material) and the second organic compound 122 (assist material), resulting in a decrease in light emission efficiency. 1 0 (host material) and the second organic compound 122 (assist material), resulting in a decrease in light emission efficiency.

[0028] In addition, in order to increase the energy transfer efficiency from the host material to the guest material, considering the Förster mechanism (dipole-dipole interaction) and Dexter mechanism (electron exchange interaction) known as intermolecular transfer mechanisms, when discussing the energy transfer from the singlet excited state, the fluorescence spectrum of the host material is considered; when discussing the energy transfer from the triplet excited state, the phosphorescence spectrum of the host material is considered) and the absorption spectrum of the guest material (more specifically, ​​​​​​The overlap with the spectrum in the absorption band on the longest wavelength (lowest energy) side becomes large. This is preferable.

[0029] However, when a phosphorescent compound is used as the guest material, for example, it is difficult to overlap the fluorescence spectrum of the host material with the absorption spectrum in the absorption band on the longest wavelength (lowest energy) side of the guest material. This is because if this is done, the phosphorescence spectrum of the host material is located on the longer wavelength (lower energy) side than the fluorescence spectrum, so the T level of the host material is lower than the T level of the phosphorescent compound, and the quenching problem described above occurs. On the other hand, in order to avoid the quenching problem, if the T level of the host material is designed to be higher than the T level of the phosphorescent compound used as the guest material, then the fluorescence spectrum of the host material shifts to the shorter wavelength (higher energy) side, so its fluorescence spectrum does not overlap with the absorption spectrum in the absorption band on the longest wavelength (lowest energy) side of the guest material. Therefore, it is usually difficult to overlap the fluorescence spectrum of the host material with the absorption spectrum in the absorption band on the longest wavelength (lowest energy) side of the guest material and maximize the energy transfer from the singlet excited state of the host material. The fluorescence spectrum of the host material is overlapped with the absorption spectrum in the absorption band on the longest wavelength (lowest energy) side of the guest material. This is because if this is done, the phosphorescence spectrum of the host material is located on the longer wavelength (lower energy) side than the fluorescence spectrum, so the T level of the host material is lower than the T level of the phosphorescent compound, and the quenching problem described above occurs. The phosphorescence spectrum is located on the longer wavelength (lower energy) side than the fluorescence spectrum, so the T level of the host material is lower than the T level of the phosphorescent compound, and the quenching problem described above occurs. The T level of the host material 1 is lower than the T level of the phosphorescent compound 1 and the quenching problem described above occurs. On the other hand, in order to avoid the quenching problem, if the T level of the host material is designed to be higher than the T level of the phosphorescent compound used as the guest material, 1 the T level of the host material is higher than the T level of the phosphorescent compound used as the guest material. 1 This time, the fluorescence spectrum of the host material shifts to the shorter wavelength (higher energy) side, so its fluorescence spectrum does not overlap with the absorption spectrum in the absorption band on the longest wavelength (lowest energy) side of the guest material. Therefore, it is usually difficult to overlap the fluorescence spectrum of the host material with the absorption spectrum in the absorption band on the longest wavelength (lowest energy) side of the guest material and maximize the energy transfer from the singlet excited state of the host material. Therefore, it is usually difficult to overlap the fluorescence spectrum of the host material with the absorption spectrum in the absorption band on the longest wavelength (lowest energy) side of the guest material and maximize the energy transfer from the singlet excited state of the host material. (low energy) side and maximize the energy transfer from the singlet excited state of the host material. This is usually difficult.

[0030] Therefore, in the present invention, the first organic compound 120 and the second organic compound 122 are a combination that forms an exciplex (also referred to as an exciplex). The exciplex will be described below with reference to FIGS. 2(A) and 2(B). The exciplex will be described below with reference to FIGS. 2(A) and 2(B).

[0031] Figure 2(A) is a schematic diagram showing the concept of an exciplex, and shows the fluorescence spectrum of the first organic compound 120 (or the second organic compound 122), the phosphorescence spectrum of the first organic compound 120 (or the second organic compound 122), the absorption spectrum of the third organic compound 124, and the emission spectrum of the exciplex. For example, in the light-emitting layer 113, the fluorescence spectrum of the first organic compound 120 (host material) and the fluorescence spectrum of the second organic compound 122 (assist material) are converted into the emission spectrum of an exciplex located on the longer wavelength side. And, by selecting the first organic compound 120 (host material) and the second organic compound 122 (assist material) so that the overlap between the emission spectrum of the exciplex and the absorption spectrum of the third organic compound 124 (guest material) becomes large, energy transfer from the singlet excited state can be maximally enhanced (see Figure 2(A)). It is considered that energy transfer from the exciplex rather than the host material also occurs with respect to the triplet excited state. Therefore, since the emission wavelength of the formed exciplex exists on the longer wavelength side compared to the respective emission wavelengths (fluorescence wavelengths) of the first organic compound 120 (host material) and the second organic compound 122 (assist material), the fluorescence spectrum of the first organic compound 120 (host material) and the fluorescence spectrum of the second organic compound 122 (assist material) can be made into emission spectra located on the longer wavelength side.

[0032] Moreover, the exciplex has an extremely small difference between the singlet excitation energy and the triplet excitation energy.

[0033]

[0034]

[0035] ​​​​​​​​​​​​​​It is considered that, in other words, the emission spectrum from the singlet state of the exciplex and the emission spectrum from the triplet state will be extremely close. Therefore, as described above, when the emission spectrum of the exciplex (generally, the emission spectrum from the singlet state of the exciplex) is designed to overlap with the absorption band located on the longest wavelength side of the third organic compound 124 (guest material), the emission spectrum from the triplet state of the exciplex (which is not observed at room temperature and is often not observed even at low temperature) will also overlap with the absorption band located on the longest wavelength side of the third organic compound 124 (guest material). That is, not only the energy transfer from the singlet excited state but also the efficiency of the energy transfer from the triplet excited state is increased, and as a result, both singlet and triplet can be efficiently emitted. Thus, the emission spectrum of the exciplex formed in the light-emitting layer 113 and the absorption spectrum of the third organic compound 124 (guest material) are utilized to perform energy transfer, and the energy transfer efficiency is high. In addition, since the exciplex exists only in the excited state, there is no ground state that can absorb energy. Therefore, the phenomenon that the third organic compound 124 (guest material) is deactivated (i.e., the luminous efficiency is impaired) before emitting light due to the energy transfer from the singlet excited state and the triplet excited state of the third organic compound 124 (guest material) to the exciplex is considered not to occur in principle. Note that the above-mentioned exciplex is formed by the interaction between different molecules in the excited state.

[0036] As described above, the light-emitting element according to one aspect of the present invention has a high energy transfer efficiency in order to perform energy transfer by utilizing the overlap between the emission spectrum of the exciplex formed in the light-emitting layer 113 and the absorption spectrum of the third organic compound 124 (guest material).

[0037] Also, since the exciplex exists only in the excited state, there is no ground state that can absorb energy. Therefore, the phenomenon that the third organic compound 124 (guest material) is deactivated (i.e., the luminous efficiency is impaired) before emitting light due to the energy transfer from the singlet excited state and the triplet excited state of the third organic compound 124 (guest material) to the exciplex is considered not to occur in principle.

[0038] In addition, since the exciplex exists only in the excited state, there is no ground state that can absorb energy. Therefore, the phenomenon that the third organic compound 124 (guest material) is deactivated (i.e., the luminous efficiency is impaired) before emitting light due to the energy transfer from the singlet excited state and the triplet excited state of the third organic compound 124 (guest material) to the exciplex is considered not to occur in principle. ​​​​​​​​​​​It also tends to form easily between a material having a relatively low LUMO (LUMO: Lowest Unoccupied Molecular Orbital) level and a material having a high HOMO (HOMO: Highest Occupied Molecular Orbital) level, which is generally known.

[0039] Here, the concept of the energy levels of the first organic compound 120, the second organic compound 122, and the exciplex will be described with reference to FIG. 2(B). Note that FIG. 2(B) schematically shows the energy levels of the first organic compound 120, the second organic compound 122, and the exciplex.

[0040] The HOMO and LUMO levels of the first organic compound 120 (host material) and the second organic compound 122 (assist material) are different from each other. Specifically, the energy levels are different in the order of the HOMO level of the first organic compound 120 < the HOMO level of the second organic compound 122 < the LUMO level of the first organic compound 120 < the LUMO level of the second organic compound 122. When an exciplex is formed by these two organic compounds, the LUMO level of the exciplex is derived from the first organic compound 120 (host material), and the HOMO level is derived from the second organic compound 122 (assist material) (see FIG. 2(B)).

[0041] In addition, the emission wavelength of the exciplex depends on the energy difference between the HOMO and LUMO levels. As a general tendency, when the energy difference is large, the emission wavelength becomes short, and when the energy difference is small, the emission wavelength becomes long.

[0042] ​​​​​​​​​​​​​​ Therefore, the energy difference of the exciplex is smaller than the energy difference of the first organic compound 120 (host material) and the energy difference of the second organic compound 122 (assist material). That is, the emission wavelength of the exciplex becomes longer than the emission wavelengths of the first organic compound 120 and the second organic compound 122, respectively.

[0043] Here, regarding whether the exciplex actually has such characteristics, verification was performed using molecular orbital calculations. Generally, a combination of a heteroaromatic compound and an aromatic amine often forms an exciplex due to the influence of the LUMO level of the heteroaromatic compound (the property that electrons easily enter) being lower than the LUMO level of the aromatic amine and the HOMO level of the aromatic amine (the property that holes easily enter) being higher than the HOMO level of the heteroaromatic compound. Therefore, dibenzo[f,h]quinoxaline (abbreviation: DBq), which is a representative skeleton constituting the LUMO of a heteroaromatic compound, was used as a model of the first organic compound 120 in one aspect of the present invention, and triphenylamine (abbreviation: TPA), which is a representative skeleton constituting the HOMO of an aromatic amine, was used as a model of the second organic compound 122 in one aspect of the present invention, and calculations were performed by combining them.

[0044]

[0045]

[0044] First, the optimal molecular structure and excitation energy in the lowest excited singlet state (S 1 ) and the lowest excited triplet state (T ) of one molecule of DBq (abbreviation) and one molecule of TPA (abbreviation) were calculated using the time-dependent density functional theory (TD-DFT). Furthermore, the excitation energy of the dimer of DBq (abbreviation) and TPA (abbreviation) was also calculated. 1 ) were calculated using the time-dependent density functional theory (TD-DFT). Furthermore, the excitation energy of the dimer of DBq (abbreviation) and TPA (abbreviation) was also calculated. functional theory (TD-DFT). Furthermore, the excitation energy of the dimer of DBq (abbreviation) and TPA (abbreviation) was also calculated.

[0045] ​The total energy of DFT (density functional theory) is the sum of the potential energy, the electrostatic energy between electrons, the kinetic energy of electrons, and the exchange-correlation energy that includes all complex interactions between electrons. In DFT, since the exchange-correlation interaction is approximated by a functional of a one-electron potential expressed in terms of the electron density (the meaning of a function of a function), the calculation is fast and highly accurate. Here, the weights of the parameters related to the exchange and correlation energies were defined using the hybrid functional B3LYP. Moreover, as the basis functions, 6-311 (basis functions of the triple split valence basis system using three contracted functions for each valence orbital) were applied to all atoms. With the above-mentioned basis functions, for example, for a hydrogen atom, the 1s - 3s orbitals are considered, and for a carbon atom, the 1s - 4s, 2p - 4p orbitals are considered. Furthermore, to improve the calculation accuracy, as a polarized basis system, a p function was added to hydrogen atoms and a d function was added to atoms other than hydrogen atoms.

[0046] Note that Gaussian 09 was used as the quantum chemistry calculation program. The calculation was performed using a high-performance computer (Altix 4700 manufactured by SGI).

[0047] First, for one molecule of DBq (abbreviation), one molecule of TPA (abbreviation), and the dimer of DBq (abbreviation) and TPA (abbreviation), the HOMO level and the LUMO level were calculated. The HOMO level and the LUMO level are shown in Figure 3.

[0048]

[0049]

[0050] As shown in FIG. 3, the dimer of DBq (abbreviation) and TPA (abbreviation) has the L of TPA (abbreviation). The LUMO level (-1.99 eV) of DBq (abbreviation), which is lower than the LUMO level of TPA (abbreviation), and the HOMO level (-5.21 eV) of TPA (abbreviation), which is higher than the HOMO level of DBq (abbreviation). Due to the influence of, it is suggested that an exciplex of DBq (abbreviation) and TPA (abbreviation) is formed.

[0051] Next, the HOMO and LUMO distributions of one molecule of DBq (abbreviation), one molecule of TPA (abbreviation), and the dimer of DBq (abbreviation) and TPA (abbreviation) are shown in FIG. 4.

[0052] Note that FIG. 4(A) shows the LUMO distribution of one molecule of DBq (abbreviation), FIG. 4(B) shows the HOMO distribution of one molecule of DB q (abbreviation), FIG. 4(C) shows the LUM O distribution of one molecule of TPA (abbreviation), FIG. 4(D) shows the HOMO distribution of one molecule of TPA (abbreviation), and FIG. 4(E ) shows the LUMO distribution of the dimer of DBq (abbreviation) and TPA (abbreviation), and FIG. 4(F) shows the D The HOMO distribution of the dimer of Bq (abbreviation) and TPA (abbreviation) is shown respectively.

[0053] As shown in FIGS. 4(E) and 4(F), the LUMO of the dimer of DBq (abbreviation) and TPA (abbreviation) is distributed on the DBq (abbreviation) side, and the HOMO is distributed on the TPA (abbreviation) side, suggesting the results shown in FIG. 3.

[0054] In addition, in the process of forming an exciplex in one aspect of the present invention, the following two processes are considered

[0055] The first process of forming an exciplex is that the first organic compound 120 (host material) and the second organic Compound 122 (assist material) is in a state with carriers (cation or anion) ​​​​​This is the process of forming an exciplex.

[0056] In general, when electrons and holes recombine in a host material, they are released from the host material in an excited state. The excitation energy is transferred from the hologram to the guest material, and the guest material reaches an excited state and emits light. The host material itself emits light before the excitation energy is transferred from the host material to the guest material. Or, the excitation energy becomes thermal energy, and some of the excitation energy is deactivated. Wow.

[0057] However, in one embodiment of the present invention, a first organic compound 120 (host material) and a second The organic compound 122 (assist material) has a carrier (cation or anion) ) to form an exciplex, the singlet excitons of the first organic compound 120 (host material) are In other words, it is possible to suppress the formation of excitons directly without forming singlet excitons. There may be a process of forming a complex, which also suppresses the deactivation of the singlet excitation energy. Therefore, a light emitting element having a long life can be realized.

[0058] For example, the first organic compound 120 captures electrons (carriers) even in the electron transport material. It is a compound with electron trapping properties that has a low LUMO level and is easy to dissociate. The organic compound 122 has the property of easily capturing holes (carriers) among hole transporting materials. In the case where the first organic compound is a hole trapping compound (having a high HOMO level), A direct exciplex is formed from the anion of 120 and the cation of a second organic compound 122. The exciplex formed in this process is called an electroplex ( We will call this the "electroplex."

[0059] In this way, the generation of the singlet excited state of the first organic compound 120 (host material) is suppressed. Then, energy transfer from the electrocomplex to the third organic compound 124 (guest material) is performed, so that a light-emitting element with high luminous efficiency can be obtained. In this case, the generation of the triplet excited state of the first organic compound 120 (host material) is similarly suppressed, and since a direct exciplex is formed, it is considered that energy transfer occurs from the exciplex to the third organic compound 124 (guest material). The generation of the triplet excited state of the first organic compound 120 (host material) is similarly suppressed, and since a direct exciplex is formed, it is considered that energy transfer occurs from the exciplex to the third organic compound 124 (guest material). The formation process of the second exciplex is a elementary process in which after one of the first organic compound 120 (host material) and the second organic compound 122 (assist material) forms a singlet exciton, it interacts with the other in the ground state to form an exciplex. Different from the electrocomplex, in this case, once the singlet excited state of the first organic compound 120 (host material) or the second organic compound 122 (assist material) is generated, it is quickly converted into an exciplex, so that the deactivation of the singlet excitation energy can still be suppressed. Therefore, the loss of excitation energy of the first organic compound 120 or the second organic compound 122 can be suppressed. In this case, the triplet excited state of the first organic compound 120 (host material) is similarly quickly converted into an exciplex, and it is considered that energy transfer occurs from the exciplex to the third organic compound 124 (guest material). In this case, the triplet excited state of the first organic compound 120 (host material) is similarly quickly converted into an exciplex, and it is considered that energy transfer occurs from the exciplex to the third organic compound 124 (guest material).

[0060] Note that the first organic compound 120 (host material) is an electron trap compound, while the second organic compound 122 (assist material) is a hole trap compound. After one of the first organic compound 120 (host material) and the second organic compound 122 (assist material) forms a singlet exciton, it interacts with the other in the ground state to form an exciplex. Different from the electrocomplex, in this case, once the singlet excited state of the first organic compound 120 (host material) or the second organic compound 122 (assist material) is generated, it is quickly converted into an exciplex, so that the deactivation of the singlet excitation energy can still be suppressed. Therefore, the loss of excitation energy of the first organic compound 120 or the second organic compound 122 can be suppressed. In this case, the triplet excited state of the first organic compound 120 (host material) is similarly quickly converted into an exciplex, and it is considered that energy transfer occurs from the exciplex to the third organic compound 124 (guest material). In this case, the triplet excited state of the first organic compound 120 (host material) is similarly quickly converted into an exciplex, and it is considered that energy transfer occurs from the exciplex to the third organic compound 124 (guest material). Note that the first organic compound 120 (host material) is an electron trap compound, while the second organic compound 122 (assist material) is a hole trap compound. In this case, the triplet excited state of the first organic compound 120 (host material) is similarly quickly converted into an exciplex, and it is considered that energy transfer occurs from the exciplex to the third organic compound 124 (guest material). In this case, the triplet excited state of the first organic compound 120 (host material) is similarly quickly converted into an exciplex, and it is considered that energy transfer occurs from the exciplex to the third organic compound 124 (guest material). (guest material).

[0061] Note that the first organic compound 120 (host material) is an electron trap compound, while the second organic compound 122 (assist material) is a hole trap compound. On the other hand, the second organic compound 122 (assist material) is a hole trap compound. When the difference in the HOMO levels and the difference in the LUMO levels of the compounds are large (specifically, the difference is 0.3 eV or more), electrons selectively enter the first organic compound 120 (host material), and holes selectively enter the second organic compound 122 (assist material). In this case, the process of forming an electrocomplex is prioritized over the process of forming an exciplex through a singlet exciton. It is considered that.

[0062] Next, the calculation results of the excitation energy are shown. The S 1 excitation energy of one molecule of DBq (abbreviation) is 3.294 eV, and the fluorescence wavelength is 376.4 nm. Also, the T excitation energy of one molecule of DBq (abbreviation) is 2.460 eV, and the phosphorescence wavelength is 504.1 nm. On the other hand, the S 1 excitation energy of one molecule of TPA (abbreviation) is 3.508 eV and the fluorescence wavelength is 353.4 nm. Also, the T 1 excitation energy of one molecule of TPA (abbreviation) is 2.610 eV, and the phosphorescence wavelength is 474.7 nm. Here, the excitation energies obtained from the optimal molecular structures of the S 1 and T of the dimer of DBq (abbreviation) and TPA (abbreviation) are shown. The S

[0063] excitation energy of the dimer of DBq (abbreviation) and TPA (abbreviation) is 2.036 eV, and the fluorescence wavelength is 609.1 nm. Also 1 1 1

[0064] the excitation energy of the T 1 of the dimer of DBq (abbreviation) and TPA (abbreviation) is 2.030 eV and the phosphorescence wavelength is 610.0 nm.

[0064] From the above, the fluorescence wavelength of the dimer of DBq (abbreviation) and TPA (abbreviation) is It has been found that the fluorescence wavelengths of the single molecule of 1,2-dichlorophenyl phosphate (TPA) are longer than those of the single molecule of 1,2-dichlorophenyl phosphate (TPA). The difference between the fluorescence and phosphorescence wavelengths of the dimers of DBq (abbreviation) and TPA (abbreviation) is small. It can be seen that the wavelengths are almost the same, being only 0.9 nm.

[0065] From these results, it can be seen that the exciplex has almost the same excitation energy for singlet and triplet. Therefore, as mentioned above, the exciplex is Efficient energy transfer from both the singlet and triplet states of It was suggested that it could be moved.

[0066] This effect is a unique effect that results from using exciplexes as a medium for energy transfer. Generally, phosphorescence occurs from the singlet or triplet excited state of the host material. On the other hand, in one embodiment of the present invention, the energy transfer to the host material and the other compound is taken into consideration. First, an exciplex is formed with the material, and then energy transfer from the exciplex is used. This difference makes it possible to achieve unprecedentedly high luminous efficiency. There is.

[0067] Generally, when an exciplex is used in the light-emitting layer of a light-emitting device, it is possible to control the color of emitted light. Although they have utility, the luminescence efficiency is usually significantly reduced. The light-emitting element used here has been considered to be unsuitable for obtaining a highly efficient light-emitting element. However, as shown in one embodiment of the present invention, an exciplex can be used as a medium for energy transfer. However, the inventors have found that it is possible to increase the luminous efficiency to the maximum extent. This is a technological concept that contradicts conventional stereotypes.

[0068] The emission spectrum of the exciplex and the absorption spectrum of the third organic compound 124 (guest material) were In order to overlap the spectra sufficiently, the energy values ​​of the peaks in the emission spectrum and the absorption spectrum must be The difference between the energy value of the absorption band peak on the lowest energy side of the It is preferable that the difference is within 0.2 eV, more preferable that the difference is within 0.1 eV. Within.

[0069] In the light-emitting element of one embodiment of the present invention, the excitation energy of the exciplex is a third The energy transfer to the organic compound 124 (guest material) was sufficient, and the emission from the exciplex was substantial. Therefore, it is preferable that the third organic compound 124 is not observed through the exciplex. (guest material) to transfer energy, and the third organic compound 124 emits phosphorescence. The third organic compound 124 is preferably an organic compound that converts triplet excitation energy into light emission. Any luminescent material capable of emitting light capable of emitting light of this kind may be used, and phosphorescent compounds are particularly preferred.

[0070] Next, the concept of energy levels of the hole-transport layer 112 and the light-emitting layer 113 according to one embodiment of the present invention will be described. The following will be described with reference to Figs. 5(A), 5(B), and 5(C). 5A), 5B, and 5C show the hole transport layer 112 (hole transport layers 112a, 112 11 is a diagram showing the energy levels of the light-emitting layer 113 and the light-emitting layer 112b and 112c.

[0071] The light-emitting layer 113 shown in FIG. 5(A), FIG. 5(B), and FIG. 5(C) is the same as that described above. A combination of a first organic compound 120 and a second organic compound 122 that form an exciplex Yes.

[0072] Regarding the configuration in which the hole transport layer 112a shown in Fig. 5(A) is formed of one type of organic compound whose T level is higher than that of the second organic compound 122 ( assist material) and whose HOMO level is lower than that of the second organic compound 122 (assist material), an example is shown. 1 In the case of the configuration shown in Fig. 5(A), since the HOMO level of the hole transport layer 112a is lower than the HOMO level of the light-emitting layer 113 that forms an exciplex, holes can more easily enter from the hole transport layer 112a into the interior of the light-emitting layer 113, and the light-emitting efficiency of the light-emitting layer 113 can be increased. On the other hand, the driving start voltage is determined by the energy of E (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) shown in Fig. 5(A), and it cannot be made lower than the voltage corresponding to that energy. For example, if E

[0073] is 2 eV, the driving start voltage cannot be made lower than 2 V. In the case of the configuration shown in Fig. 5(A), this is because the energy of E is larger than the energy of E (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the hole transport layer 112a). , the driving start voltage cannot be made lower than the voltage corresponding to that energy. For example, if E 1 (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) shown in Fig. 5(A), and it cannot be made lower than the voltage corresponding to that energy. For example, if E is 2 eV, the driving start voltage cannot be made lower than 2 V. In the case of the configuration shown in Fig. 5(A), this is because the energy of E is larger than the energy of E 1 is 2 eV, the driving start voltage cannot be made lower than 2 V. In the case of the configuration shown in Fig. 5(A), this is because the energy of E is larger than the energy of E 1 is larger than the energy of E is larger than the energy of E 2a (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the hole transport layer 112a). is larger than the energy of E

[0074] Next, regarding the configuration in which the hole transport layer 112b shown in Fig. 5(B) is formed of one type of organic compound whose T level is higher than that of the second organic compound 1 22 (assist material) and whose HOMO level is higher than that of the second organic compound 122 (assist material), an example is shown. 1 In the case of the configuration shown in Fig. 5(B), since the HOMO level of the hole transport layer 112b is higher than the HOMO level of the light-emitting layer 113 that forms an exciplex, holes can more easily enter from the hole transport layer 112b into the interior of the light-emitting layer 113, and the light-emitting efficiency of the light-emitting layer 113 can be increased. On the other hand, the driving start voltage is determined by the energy of E (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) shown in Fig. 5(B), and it cannot be made lower than the voltage corresponding to that energy. For example, if E

[0075] In the case of the structure shown in FIG. 5(B), since the HOMO level of the hole transport layer 112b is higher than the HOMO level of the light-emitting layer 113 that forms an exciplex, the driving voltage (particularly, the turn-on voltage) is affected by the HOMO level of the hole transport layer 112b. Specifically, in the case of the structure shown in FIG. 5(B), the turn-on voltage is determined by the energy (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the hole transport layer 112b). Therefore, in the case of the structure shown in FIG. 5(B), since the energy of E (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) is smaller than the energy of E, the turn-on voltage can be lowered. However, holes hardly move from the hole transport layer 112b to the light-emitting layer 113, and the luminous efficiency decreases particularly in the high luminance (practical luminance) region. In the case of the structure shown in FIG. 5(B), since the HOMO level of the hole transport layer 112b is higher than the HOMO level of the light-emitting layer 113 that forms an exciplex, the driving voltage (particularly, the turn-on voltage) is affected by the HOMO level of the hole transport layer 112b. Specifically, in the case of the structure shown in FIG. 5(B), the turn-on voltage is determined by the energy (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the hole transport layer 112b). Therefore, in the case of the structure shown in FIG. 5(B), since the energy of E (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) is smaller than the energy of E, the turn-on voltage can be lowered. However, holes hardly move from the hole transport layer 112b to the light-emitting layer 113, and the luminous efficiency decreases particularly in the high luminance (practical luminance) region. In the case of the structure shown in FIG. 5(B), since the HOMO level of the hole transport layer 112b is higher than the HOMO level of the light-emitting layer 113 that forms an exciplex, the driving voltage (particularly, the turn-on voltage) is affected by the HOMO level of the hole transport layer 112b. Specifically, in the case of the structure shown in FIG. 5(B), the turn-on voltage is determined by the energy (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the hole transport layer 112b). Therefore, in the case of the structure shown in FIG. 5(B), since the energy of E (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) is smaller than the energy of E, the turn-on voltage can be lowered. However, holes hardly move from the hole transport layer 112b to the light-emitting layer 113, and the luminous efficiency decreases particularly in the high luminance (practical luminance) region. 2b ( In the case of the structure shown in FIG. 5(B), since the HOMO level of the hole transport layer 112b is higher than the HOMO level of the light-emitting layer 113 that forms an exciplex, the driving voltage (particularly, the turn-on voltage) is affected by the HOMO level of the hole transport layer 112b. Specifically, in the case of the structure shown in FIG. 5(B), the turn-on voltage is determined by the energy (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the hole transport layer 112b). Therefore, in the case of the structure shown in FIG. 5(B), since the energy of E (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) is smaller than the energy of E, the turn-on voltage can be lowered. However, holes hardly move from the hole transport layer 112b to the light-emitting layer 113, and the luminous efficiency decreases particularly in the high luminance (practical luminance) region. In the case of the structure shown in FIG. 5(B), since the HOMO level of the hole transport layer 112b is higher than the HOMO level of the light-emitting layer 113 that forms an exciplex, the driving voltage (particularly, the turn-on voltage) is affected by the HOMO level of the hole transport layer 112b. Specifically, in the case of the structure shown in FIG. 5(B), the turn-on voltage is determined by the energy (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the hole transport layer 112b). Therefore, in the case of the structure shown in FIG. 5(B), since the energy of E (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) is smaller than the energy of E, the turn-on voltage can be lowered. However, holes hardly move from the hole transport layer 112b to the light-emitting layer 113, and the luminous efficiency decreases particularly in the high luminance (practical luminance) region. (B), in the case of the structure shown in FIG. 5 1 (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the hole transport layer 112b), the turn-on voltage is determined by the energy. Therefore, in the case of the structure shown in FIG. 5(B), since the energy of E (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) is smaller than the energy of E, the turn-on voltage can be lowered. However, holes hardly move from the hole transport layer 112b to the light-emitting layer 113, and the luminous efficiency decreases particularly in the high luminance (practical luminance) region. In the case of the structure shown in FIG. 5(B), since the HOMO level of the hole transport layer 112b is higher than the HOMO level of the light-emitting layer 113 that forms an exciplex, the driving voltage (particularly, the turn-on voltage) is affected by the HOMO level of the hole transport layer 112b. Specifically, in the case of the structure shown in FIG. 5(B), the turn-on voltage is determined by the energy (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the hole transport layer 112b). Therefore, in the case of the structure shown in FIG. 5(B), since the energy of E (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) is smaller than the energy of E, the turn-on voltage can be lowered. However, holes hardly move from the hole transport layer 112b to the light-emitting layer 113, and the luminous efficiency decreases particularly in the high luminance (practical luminance) region. 2b In the case of the structure shown in FIG. 5(B), since the HOMO level of the hole transport layer 112b is higher than the HOMO level of the light-emitting layer 113 that forms an exciplex, the driving voltage (particularly, the turn-on voltage) is affected by the HOMO level of the hole transport layer 112b. Specifically, in the case of the structure shown in FIG. 5(B), the turn-on voltage is determined by the energy (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the hole transport layer 112b). Therefore, in the case of the structure shown in FIG. 5(B), since the energy of E (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) is smaller than the energy of E, the turn-on voltage can be lowered. However, holes hardly move from the hole transport layer 112b to the light-emitting layer 113, and the luminous efficiency decreases particularly in the high luminance (practical luminance) region. In the case of the structure shown in FIG. 5(B), since the HOMO level of the hole transport layer 112b is higher than the HOMO level of the light-emitting layer 113 that forms an exciplex, the driving voltage (particularly, the turn-on voltage) is affected by the HOMO level of the hole transport layer 112b. Specifically, in the case of the structure shown in FIG. 5(B), the turn-on voltage is determined by the energy (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the hole transport layer 112b). Therefore, in the case of the structure shown in FIG. 5(B), since the energy of E (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) is smaller than the energy of E, the turn-on voltage can be lowered. However, holes hardly move from the hole transport layer 112b to the light-emitting layer 113, and the luminous efficiency decreases particularly in the high luminance (practical luminance) region. In the case of the structure shown in FIG. 5(B), since the HOMO level of the hole transport layer 112b is higher than the HOMO level of the light-emitting layer 113 that forms an exciplex, the driving voltage (particularly, the turn-on voltage) is affected by the HOMO level of the hole transport layer 112b. Specifically, in the case of the structure shown in FIG. 5(B), the turn-on voltage is determined by the energy (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the hole transport layer 112b). Therefore, in the case of the structure shown in FIG. 5(B), since the energy of E (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 113 that forms an exciplex) is smaller than the energy of E, the turn-on voltage can be lowered. However, holes hardly move from the hole transport layer 112b to the light-emitting layer 113, and the luminous efficiency decreases particularly in the high luminance (practical luminance) region.

[0076] Next, the energy level of the hole transport layer 112c shown in FIG. 5(C) represents an idea of one embodiment of the present invention, and an example is given of a configuration in which a hole transport layer 112c having a fourth organic compound 126 below at least the HOMO level of the second organic compound 122 (assist material) and a fifth organic compound 128 having a higher HOMO level than the second organic compound 122 (assist material) is formed. Next, the energy level of the hole transport layer 112c shown in FIG. 5(C) represents an idea of one embodiment of the present invention, and an example is given of a configuration in which a hole transport layer 112c having a fourth organic compound 126 below at least the HOMO level of the second organic compound 122 (assist material) and a fifth organic compound 128 having a higher HOMO level than the second organic compound 122 (assist material) is formed. Next, the energy level of the hole transport layer 112c shown in FIG. 5(C) represents an idea of one embodiment of the present invention, and an example is given of a configuration in which a hole transport layer 112c having a fourth organic compound 126 below at least the HOMO level of the second organic compound 122 (assist material) and a fifth organic compound 128 having a higher HOMO level than the second organic compound 122 (assist material) is formed. Next, the energy level of the hole transport layer 112c shown in FIG. 5(C) represents an idea of one embodiment of the present invention, and an example is given of a configuration in which a hole transport layer 112c having a fourth organic compound 126 below at least the HOMO level of the second organic compound 122 (assist material) and a fifth organic compound 128 having a higher HOMO level than the second organic compound 122 (assist material) is formed. Next, the energy level of the hole transport layer 112c shown in FIG. 5(C) represents an idea of one embodiment of the present invention, and an example is given of a configuration in which a hole transport layer 112c having a fourth organic compound 126 below at least the HOMO level of the second organic compound 122 (assist material) and a fifth organic compound 128 having a higher HOMO level than the second organic compound 122 (assist material) is formed.

[0077] In the case of the structure shown in FIG. 5(C), the HOMO level of the hole transport layer 112c can be made below the HOMO level of the second organic compound 122 (assist material) due to the influence of the fourth organic compound 126. Therefore, holes can move more deeply from the hole transport layer 112c into the light-emitting layer 113. In the case of the structure shown in FIG. 5(C), the HOMO level of the hole transport layer 112c can be made below the HOMO level of the second organic compound 122 (assist material) due to the influence of the fourth organic compound 126. Therefore, holes can move more deeply from the hole transport layer 112c into the light-emitting layer 113. In the case of the structure shown in FIG. 5(C), the HOMO level of the hole transport layer 112c can be made below the HOMO level of the second organic compound 122 (assist material) due to the influence of the fourth organic compound 126. Therefore, holes can move more deeply from the hole transport layer 112c into the light-emitting layer 113. It becomes easier to enter, and the luminous efficiency of the light-emitting layer 113 can be increased. Also, the driving voltage (especially the driving start voltage) is affected by the HOMO level of the hole transport layer 112c. The hole transport layer 1 112c has its HOMO level determined by the influence of the fifth organic compound 128. Also, the hole transport layer 112c has its LUMO level determined by the influence of the fourth organic compound 126. FIG. 5 (C) shows the E 2c (the energy difference between the LUMO level of the light-emitting layer 113 that forms an exciplex and the HOMO level of the fifth organic compound 128), and the driving start voltage is determined by this energy. Therefore, in the case of the configuration shown in FIG. 5(C), since the energy of E is smaller than the energy of E 1 (the energy difference between the LUMO level and the HOMO level of the light-emitting layer 1 13 that forms an exciplex), the driving start voltage can be lowered. 2c of energy Since the energy is small, the driving start voltage can be lowered.

[0078] By adopting the configuration shown in FIG. 5(C), it becomes possible to flow a recombination current with an electrical energy lower than the light-emitting energy of the light-emitting layer 113. Generally, the driving start voltage is considered to be a voltage corresponding to the light-emitting energy of the light-emitting layer 113, and it is considered that operation does not start at a voltage lower than that. However, since the driving start voltage in one aspect of the present invention is determined by the fifth organic compound 128 contained in the hole transport layer 11 2c, it can be made lower than the driving start voltage that was common knowledge in the past. Also, at the start of driving, since the fifth organic compound 128 contributes to the formation of excitation energy, the luminous efficiency is considered to be low, but since the luminance at the start of driving is almost invisible, there is no practical problem. In fact, in the practical luminance range (specifically 1 cd / m or more), the injection of holes from the fourth organic compound 126 into the light-emitting layer 113 is the main Since it is determined by the fifth organic compound 128 contained in 2c, it can be made lower than the driving start voltage that was common knowledge in the past. Also, at the start of driving, since the fifth organic compound 128 contributes to the formation of excitation energy, the luminous efficiency is considered to be low, but since the luminance at the start of driving is almost invisible, there is no practical problem. In fact, in the practical luminance range (specifically start voltage, it can be made lower. Also, at the start of driving, since the fifth organic compound 128 contributes to the formation of excitation energy, the luminous efficiency is considered to be low, but since the luminance at the start of driving is almost invisible, there is no practical problem. In fact, in the practical luminance range (specifically ), although it is considered that the luminous efficiency is low because the fifth organic compound 128 contributes to the formation of excitation energy at the start of driving, there is no practical problem because the luminance at the start of driving is almost invisible. Actually, in the practical luminance range (specifically ), since it is a luminance that is almost invisible at the start of driving, there is no practical problem. In fact, in the practical luminance range (specifically is 1 cd / m 2 or more), the injection of holes from the fourth organic compound 126 into the light-emitting layer 113 is the main As a result, the fifth organic compound 128 is less likely to be involved in hole injection into the light-emitting layer 113 and in the excited state Therefore, high luminous efficiency can be obtained.

[0079] As described above, in the light-emitting element according to this embodiment, in the hole transport layer 112c, the hole transport layer 112c has a fourth organic compound 126 at least below the HOMO level of the second organic compound 122 (assist material) and a fifth organic compound 128 having a higher HOMO level than the second organic compound 122 (assist material). From the fourth organic compound 1 26 in the hole transport layer 112c, holes are injected into the second organic compound 122 (assist material) in the light-emitting layer 113 As a result, the luminous efficiency can be improved. Further, since the fifth organic compound 128 in the hole transport layer 112c has a higher HOMO level than the second organic compound 122 (assist material), the driving voltage of the light-emitting layer, particularly the driving start voltage, can be lowered. This effect is obtained only when the hole transport layer has two or more types of the above organic compounds and in relation to the HOMO levels as described above.

[0080] Further, in the light-emitting element which is one aspect of the present invention, when a phosphorescent compound is used for the first organic compound 120 (host material ), the first organic compound 120 itself is likely to emit light, and it becomes difficult for energy to be transferred to the third organic compound 124 (guest material). In this case, if the first organic compound 120 emits light efficiently, the first organic compound 120 (host material) has a problem of concentration quenching, so it is difficult to achieve high luminous efficiency. Therefore, the first organic compound 120 (host material) and the second organic compound 122 (assist material) ​at least one of which is a fluorescent compound (i.e., a compound that easily undergoes luminescence or thermal deactivation from the singlet excited state) is effective. Therefore, it is preferable that at least one of the first organic compound 120 and the second organic compound 122 is a fluorescent compound.

[0081] As described above, the light-emitting device shown in this embodiment utilizes energy transfer using the overlap between the emission spectrum of the exciplex and the absorption spectrum of the third organic compound (guest material), so that the energy transfer efficiency can be increased, and a light-emitting device with high luminous efficiency can be realized.

[0082] In addition, the light-emitting device shown in this embodiment has a configuration in which a fourth organic compound having a hole-transporting property used in the light-emitting layer and having a HOMO level lower than that of the second organic compound, and a fifth organic compound having a HOMO level higher than that of the second organic compound are provided in the hole-transporting layer. With such a configuration, the current efficiency of the light-emitting device can be increased, and the voltage of the light-emitting device, particularly the driving start voltage, can be decreased.

[0083] Note that the configuration shown in this embodiment can be used in appropriate combination with the configuration shown in other embodiments.

[0084] (Embodiment 2) In this embodiment, a modified example of the light-emitting device shown in Embodiment 1 will be described with reference to FIG. 6. Note that parts having the same functions as those of the light-emitting device shown in Embodiment 1 are denoted by the same reference numerals, and redundant description thereof will be omitted.

[0085] As shown in FIG. 6, the light-emitting device shown in this embodiment includes a pair of electrodes (the first electrode 101, Between the second electrode 103), a hole injection layer 111, a hole transport layer 112 formed on the hole injection layer 111, a light-emitting layer 113 formed on the hole transport layer 112, an electron transport layer 114 formed on the light-emitting layer 113, and an electron injection layer 115 formed on the electron transport layer 114 are provided. The light-emitting layer 113 includes a first organic compound 120 having electron-transporting properties, a second organic compound 122 having hole-transporting properties, and a light-emitting third organic compound 124 that converts triplet excitation energy into light emission. The first organic compound 120 and the second organic compound 122 form an exciplex. The hole transport layer 112 includes a fourth organic compound 126 having a HOMO level equal to or lower than that of at least the second organic compound 122, and a fifth organic compound 128 having a HOMO level higher than that of the second organic compound 122. Between the second electrode 103), a hole injection layer 111, a hole transport layer 112 formed on the hole injection layer 111, a light-emitting layer 113 formed on the hole transport layer 112, an electron transport layer 114 formed on the light-emitting layer 113, and an electron injection layer 115 formed on the electron transport layer 114 are provided. The light-emitting layer 113 includes a first organic compound 120 having electron-transporting properties, a second organic compound 122 having hole-transporting properties, and a light-emitting third organic compound 124 that converts triplet excitation energy into light emission. The first organic compound 120 and the second organic compound 122 form an exciplex. The hole transport layer 112 includes a fourth organic compound 126 having a HOMO level equal to or lower than that of at least the second organic compound 122, and a fifth organic compound 128 having a HOMO level higher than that of the second organic compound 122. Between the second electrode 103), a hole injection layer 111, a hole transport layer 112 formed on the hole injection layer 111, a light-emitting layer 113 formed on the hole transport layer 112, an electron transport layer 114 formed on the light-emitting layer 113, and an electron injection layer 115 formed on the electron transport layer 114 are provided. The light-emitting layer 113 includes a first organic compound 120 having electron-transporting properties, a second organic compound 122 having hole-transporting properties, and a light-emitting third organic compound 124 that converts triplet excitation energy into light emission. The first organic compound 120 and the second organic compound 122 form an exciplex. The hole transport layer 112 includes a fourth organic compound 126 having a HOMO level equal to or lower than that of at least the second organic compound 122, and a fifth organic compound 128 having a HOMO level higher than that of the second organic compound 122. Between the second electrode 103), a hole injection layer 111, a hole transport layer 112 formed on the hole injection layer 111, a light-emitting layer 113 formed on the hole transport layer 112, an electron transport layer 114 formed on the light-emitting layer 113, and an electron injection layer 115 formed on the electron transport layer 114 are provided. The light-emitting layer 113 includes a first organic compound 120 having electron-transporting properties, a second organic compound 122 having hole-transporting properties, and a light-emitting third organic compound 124 that converts triplet excitation energy into light emission. The first organic compound 120 and the second organic compound 122 form an exciplex. The hole transport layer 112 includes a fourth organic compound 126 having a HOMO level equal to or lower than that of at least the second organic compound 122, and a fifth organic compound 128 having a HOMO level higher than that of the second organic compound 122. Between the second electrode 103), a hole injection layer 111, a hole transport layer 112 formed on the hole injection layer 111, a light-emitting layer 113 formed on the hole transport layer 112, an electron transport layer 114 formed on the light-emitting layer 113, and an electron injection layer 115 formed on the electron transport layer 114 are provided. The light-emitting layer 113 includes a first organic compound 120 having electron-transporting properties, a second organic compound 122 having hole-transporting properties, and a light-emitting third organic compound 124 that converts triplet excitation energy into light emission. The first organic compound 120 and the second organic compound 122 form an exciplex. The hole transport layer 112 includes a fourth organic compound 126 having a HOMO level equal to or lower than that of at least the second organic compound 122, and a fifth organic compound 128 having a HOMO level higher than that of the second organic compound 122. Between the second electrode 103), a hole injection layer 111, a hole transport layer 112 formed on the hole injection layer 111, a light-emitting layer 113 formed on the hole transport layer 112, an electron transport layer 114 formed on the light-emitting layer 113, and an electron injection layer 115 formed on the electron transport layer 114 are provided. The light-emitting layer 113 includes a first organic compound 120 having electron-transporting properties, a second organic compound 122 having hole-transporting properties, and a light-emitting third organic compound 124 that converts triplet excitation energy into light emission. The first organic compound 120 and the second organic compound 122 form an exciplex. The hole transport layer 112 includes a fourth organic compound 126 having a HOMO level equal to or lower than that of at least the second organic compound 122, and a fifth organic compound 128 having a HOMO level higher than that of the second organic compound 122. Between the second electrode 103), a hole injection layer 111, a hole transport layer 112 formed on the hole injection layer 111, a light-emitting layer 113 formed on the hole transport layer 112, an electron transport layer 114 formed on the light-emitting layer 113, and an electron injection layer 115 formed on the electron transport layer 114 are provided. The light-emitting layer 113 includes a first organic compound 120 having electron-transporting properties, a second organic compound 122 having hole-transporting properties, and a light-emitting third organic compound 124 that converts triplet excitation energy into light emission. The first organic compound 120 and the second organic compound 122 form an exciplex. The hole transport layer 112 includes a fourth organic compound 126 having a HOMO level equal to or lower than that of at least the second organic compound 122, and a fifth organic compound 128 having a HOMO level higher than that of the second organic compound 122. Between the second electrode 103), a hole injection layer 111, a hole transport layer 112 formed on the hole injection layer 111, a light-emitting layer 113 formed on the hole transport layer 112, an electron transport layer 114 formed on the light-emitting layer 113, and an electron injection layer 115 formed on the electron transport layer 114 are provided. The light-emitting layer 113 includes a first organic compound 120 having electron-transporting properties, a second organic compound 122 having hole-transporting properties, and a light-emitting third organic compound 124 that converts triplet excitation energy into light emission. The first organic compound 120 and the second organic compound 122 form an exciplex. The hole transport layer 112 includes a fourth organic compound 126 having a HOMO level equal to or lower than that of at least the second organic compound 122, and a fifth organic compound 128 having a HOMO level higher than that of the second organic compound 122. Between the second electrode 103), a hole injection layer 111, a hole transport layer 112 formed on the hole injection layer 111, a light-emitting layer 113 formed on the hole transport layer 112, an electron transport layer 114 formed on the light-emitting layer 113, and an electron injection layer 115 formed on the electron transport layer 114 are provided. The light-emitting layer 113 includes a first organic compound 120 having electron-transporting properties, a second organic compound 122 having hole-transporting properties, and a light-emitting third organic compound 124 that converts triplet excitation energy into light emission. The first organic compound 120 and the second organic compound 122 form an exciplex. The hole transport layer 112 includes a fourth organic compound 126 having a HOMO level equal to or lower than that of at least the second organic compound 122, and a fifth organic compound 128 having a HOMO level higher than that of the second organic compound 122.

[0086] In the light-emitting layer 113, by dispersing the third organic compound 124 (guest material) in the first organic compound 120 (host material) and the second organic compound 122 (assist material), concentration quenching due to a high concentration of the light-emitting layer 113 can be suppressed, and the light emission efficiency of the light-emitting element can be increased. In the light-emitting layer 113, by dispersing the third organic compound 124 (guest material) in the first organic compound 120 (host material) and the second organic compound 122 (assist material), concentration quenching due to a high concentration of the light-emitting layer 113 can be suppressed, and the light emission efficiency of the light-emitting element can be increased. In the light-emitting layer 113, by dispersing the third organic compound 124 (guest material) in the first organic compound 120 (host material) and the second organic compound 122 (assist material), concentration quenching due to a high concentration of the light-emitting layer 113 can be suppressed, and the light emission efficiency of the light-emitting element can be increased. In the light-emitting layer 113, by dispersing the third organic compound 124 (guest material) in the first organic compound 120 (host material) and the second organic compound 122 (assist material), concentration quenching due to a high concentration of the light-emitting layer 113 can be suppressed, and the light emission efficiency of the light-emitting element can be increased.

[0087] The first organic compound 120 (host material) and the second organic compound 122 (assist material) form an exciplex. The first organic compound 120 (host material) and the second organic compound 122 (assist material) form an exciplex.

[0088] Specific examples for manufacturing the light-emitting element according to the present embodiment will be described below.

[0089] The substrate 100 is used as a support for the light-emitting element. As the substrate 100, for example, glass, quartz, or plastic can be used. A flexible substrate may also be used. The substrate 100 is used as a support for the light-emitting element. As the substrate 100, for example, glass, quartz, or plastic can be used. A flexible substrate may also be used. A flexible substrate is a substrate that can be bent (flexible). For example, a plastic substrate made of polycarbonate, polyarylate, or polyethersulfone, etc. can be cited. Also, a film (made of polypropylene, polyester, polyvinyl fluoride, poly vinyl chloride, etc.), an inorganic vapor deposition film, etc. can also be used. Note that, as long as it functions as a support in the manufacturing process of the light-emitting element, other materials may be used.

[0090] For the first electrode 101 and the second electrode 103, metals, alloys, electrically conductive compounds, and mixtures thereof, etc. can be used. Specifically, indium tin oxide (I TO: Indium Tin Oxide), indium tin oxide containing silicon or silicon oxide, indium oxide-zinc oxide, tungsten oxide, indium oxide containing zinc oxide, gold (Au), platinum (Pt), nickel (Ni), tungsten (W) , chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), , palladium (Pd), titanium (Ti), in addition to elements belonging to Group 1 or Group 2 of the periodic table, that is, alkali metals such as lithium (Li) and cesium (Cs), and alkaline earth metals such as magnesium (Mg), calcium (Ca), strontium (Sr), etc., and alloys containing these (MgAg, AlLi), rare earth metals such as europium (Eu), ytterbium ( Yb), and alloys containing these, and other materials such as graphene can be used. Note that the first electrode 101 and the second electrode 103 can be formed by, for example, sputtering or vapor deposition (including vacuum vapor deposition) etc. In this embodiment, The first electrode 101 is used as an anode, and the second electrode 103 is used as a cathode.

[0091] Examples of substances with high hole-transporting properties used in the hole injection layer 111 and the hole transport layer 112 include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl- [1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4',4 ''-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), 4, 4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDA TA), 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino triphenylamine (abbreviation: MTDATA), 4,4'-bis[N-(spiro-9,9 '-bifluorene-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), etc. Any aromatic amine compound, 3-[N-(9-phenylcarbazol-3-yl)-N-f enylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarb azole (abbreviation: PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phen ylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN 1), etc. can be mentioned. In addition, 4,4'-di(N-carbazolyl)biphenyl (abbreviation: C BP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: T CPB), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carb Carbazole derivatives such as bazole (abbreviation: CzPA) can be used. Also, the hole-transporting materials described later can also be used. The substances described here mainly have a hole mobility of 10 -6 cm 2 / Vs or more. However, as long as the substance has higher hole transportability than electrons, other substances may be used.

[0092] Furthermore, as the hole injection layer 111 and the hole transport layer 112, 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), poly[N,N ’-bis(4-butylphenyl)-N,N’-bis(phenyl)benzidine] (abbreviation: P oly-TPD), and other polymer compounds can also be used.

[0093] In addition, acceptor substances that can be used for the hole injection layer 111 include transition metal oxides and oxides of metals belonging to Groups 4 to 8 in the periodic table of elements. Specifically, molybdenum oxide is particularly preferred.

[0094] Also, for the hole transport layer 112, from among the substances described above, the fourth organic compound 126 below the HOMO level of the second organic compound 122 (assist material) and the fifth organic compound 128 with a HOMO level higher than that of the second organic compound 122 (assist material) can be selected. Note that the substances used for the fourth organic compound 126 and the fifth organic compound 128 are not limited to the substances described above. Depending on the substance used for the second organic compound 122 (assist material), ​​​ can be appropriately selected by the implementer.

[0095] In addition, the light-emitting layer 113 includes a first organic compound 120 (host material), a second organic compound 1 22 (assist material), and a third organic compound 124 (guest material).

[0096] As the first organic compound 120 (host material), it is preferable to use an electron-transporting material. In addition, as the second organic compound 122 (assist material), it is preferable to use a hole-transporting material. In addition, as the third organic compound 124 (guest material), a light-emitting material that converts triplet excitation energy into light is preferable.

[0097] As the above-mentioned electron-transporting material, a π-deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound is preferable. For example, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 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), 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), etc., heteroaromatic compounds having a polyazole skeleton (oxadiazole derivatives, Imidazole derivatives, triazole derivatives, etc.) and 2-[3-(dibenzothiophen-4 -yl)phenyl]dibenzof,h]quinoxaline (abbreviation: 2mDBTPDBq-II ), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenz f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-ca rbazole-9-yl)biphenyl-3-yl]dibenz[f,h]quinoxaline (abbreviation : 2mCzBPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl] pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothien yl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), etc. of diazine skeleton Heterocyclic compounds having (pyrazine derivatives, pyrimidine derivatives, pyridazine derivatives, quinox aline derivatives, dibenzoquinoxaline derivatives, etc.) and 3,5-bis[(3-9H-carb azole-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri [3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), etc. of pyridine skeleton Heterocyclic compounds having (pyridine derivatives, quinoline derivatives, dibenzoquinoline derivatives, etc) are mentioned. Among the above, heterocyclic compounds having a diazine skeleton and those having a pyridine skeleton are preferable because of their good reliability. In particular, heterocyclic compounds having a diazine (pyrimidine or pyra dine) skeleton have high electron transport properties and contribute to reducing the driving voltage.

[0098] Further, as the above hole transporting material, π-excessive heteroaromatic compounds (for example, carbazole derivatives and indole derivatives) and aromatic amine compounds are preferable. For example, 4,4'-bis [N-(1-Naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N’ -bis(3-methylphenyl)-N,N’-diphenyl-[1,1’-biphenyl]-4 ,4’-diamine (abbreviation: TPD), 4,4’-bis[N-(spiro-9,9’-biflu oren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-pheny l-4’-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAF LP), 4-phenyl-3’-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4’-(9-phenyl-9H-carbazo l-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-naph thyl)-4’’-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl -9H-carbazol-3-yl)phenyl]-fluorene-2-amine (abbreviation: PCB AF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro -9,9’-bifluorene-2-amine (abbreviation: PCBASF), etc. compounds having an aromatic amine skeleton, 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4’-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis (3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3 , 3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP) and other compounds having a carbazole skeleton, 4,4',4''-(benzene-1,3,5-triyl)tri (dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4 -(9-phenyl-9H-fluorene-9-yl)phenyl]dibenzothiophene (abbreviation : DBTFLP-III), 4-[4-(9-phenyl-9H-fluorene-9-yl) phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV) and other compounds having a thio phen skeleton, 4,4',4''-(benzene-1,3,5-triyl) tri(dibenzofuran) (abbreviation: DBF3P-II), 4-{3-[3-(9-phenyl -9H-fluorene-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDB FFLBi-II) and other compounds having a furan skeleton can be mentioned. Among the above, compounds having an aromatic amine skeleton or a carbazole skeleton have good reliability and also have high hole transportability and contribute to reducing the driving voltage, so they are preferable.

[0099] In addition, these electron transport materials and hole transport materials preferably do not have an absorption spectrum in the blue region. Specifically, it is preferable that the absorption edge of the absorption spectrum is 440 nm or less.

[0100] On the other hand, as the light-emitting material that converts triplet excitation energy into light emission, for example, phosphorescent materials and thermally activated delayed fluorescence (TADF) materials showing thermally activated delayed fluorescence can be mentioned.

[0101] As the phosphorescent material, for example, a phosphorescent material having a light emission peak at 440 nm to 520 nm such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl )-4H-1,2,4-triazol-3-yl-κN 2 phenyl-κC}iridium (III) (abbreviation: Ir(mpptz-dmp) 3 ), tris(5-methyl-3,4- diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir( Mptz) 3 ), tris[4-(3-biphenyl)-5-isopropyl-3-phenyl -4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPrptz -3b) 3 ) and other organometallic iridium complexes having a 4H-triazole skeleton, or tris [3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-tri azolato]iridium(III) (abbreviation: [Ir(Mptz1-mp) 3 ), tris( 1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium (III) (abbreviation: Ir(Prptz1-Me) 3 ) and other organometallic iridium complexes having a 1H-triazole skeleton , fac-tris[1-(2,6-diisopropylphenyl )-2-phenyl-1H-imidazole]iridium(III) (abbreviation: Ir(i Prpmi) 3 ), tris[3-(2,6-dimethylphenyl)-7-methylimidazo [1,2-f]phenanthridinato]iridium(III) (abbreviation: Ir(dmpimpt -Me) 3 ) and other organometallic iridium complexes having an imidazole skeleton, or bis[2- (4’,6’-difluorophenyl)pyridinato-N,C 2’ iridium(III) te Tris(1-pyrazolyl)borate (abbreviation: FIr6), bis[2-(4’,6’-di fluorophenyl)pyridinato-N,C 2’ iridium(III) picolinate (abbreviation : FIrpic), bis{2-[3’,5’-bis(trifluoromethyl)phenyl]pyr idinato-N,C 2’}iridium(III) picolinate (abbreviation: Ir(CF 3 ppy ) 2 (pic)), bis[2-(4’,6’-difluorophenyl)pyridinato-N,C 2’ iridium(III) acetylacetonate (abbreviation: FIr(acac)) such that organometallic iridium complexes having phenylpyridine derivatives with electron-withdrawing groups as ligands are mentioned. Among the above, organometallic iridium complexes having a 4H-triazole skeleton are particularly preferred because of their excellent reliability and luminescence efficiency.

[0102] Also, for example, as phosphorescent materials having a peak of luminescence at 520 nm to 600 nm, tris (4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(mp pm) 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)), ((acetylac Cetionato)bis[4-(2-norbornyl)-6-phenylpyrimidinato]iridium( III)(endo-, exo-mixture)(abbreviation: Ir(nbppm) 2 (acac)) , (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenyl pyrimidinato]iridium(III)(abbreviation: Ir(mpmppm) 2 (acac)) , (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III )(abbreviation: Ir(dppm) 2 (acac)) and other organometallic iridium complexes having a pyrimidine skeleton, such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyra dinato)iridium(III)(abbreviation: Ir(mppr-Me) (acac)), (a 2 cetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)i ridium(III)(abbreviation: Ir(mppr-iPr) (acac)) and other organometallic iridium complexes having a pyra 2 zine skeleton, such as tris(2-phenylpyridinato-N,C 2 ’ )iridium(III)(abbreviation: Ir(ppy) 3 ) and bis(2-phenylpyridinato)iridium(III) acetylacetonate(abbreviation: Ir(ppy) -N,C 2’ )iridium(III) acetylacetonate(abbreviation: Ir(ppy) 2 a cac), bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation: Ir(bzq) 2 (acac)), tris(benzo[h]quinolinato)iridi um(III)(abbreviation: Ir(bzq) 3 ), tris(2-phenylquinolinato-N,C 2 ’ ) Iridium(III) (abbreviation: Ir(pq) 3 ), bis(2-phenylquinolinato- N,C 2’ ) iridium(III) acetylacetonate (abbreviation: Ir(pq) 2 (ac ac)), in addition to organometallic iridium complexes having a pyridine skeleton such as tris(acetyl acetonato)(monophenanthroline)terbium(III) (abbreviation: Tb(acac) 3 (Phen)) and the like. Among those described above, organometallic iridium complexes having a pyrimidine skeleton are particularly preferred because of their outstanding reliability and luminescence efficiency.

[0103] Also, for example, as a phosphorescent material having a luminescence peak at 600 nm to 700 nm, bis [4,6-bis(3-methylphenyl)pyrimidinato](diisobutyrylmethanato)iri dium(III) (abbreviation: Ir(5mdppm) 2 (dibm)), bis[4,6-bis (3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(5mdppm) 2 (dpm)), bis[4,6-di(naphthalen-1-yl l)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(d1 npm) 2 (dpm)) and other organometallic iridium complexes having a pyrimidine skeleton, or ( acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III )(abbreviation: Ir(tppr) 2 (acac)), bis(2,3,5-triphenylpyra zinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr) 2 (d pm)), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinox alinato]iridium(III) (abbreviation: Ir(Fdpq) 2 (acac)) and other organometallic iridium complexes having a pyridine skeleton, such as tris(1-phenylisoquinolinato- N,C 2’ )iridium(III) (abbreviation: Ir(piq) 3 ), bis(1-phenyliso quinolinato-N,C 2’ )iridium(III) acetylacetonate (abbreviation: Ir( piq) 2 acac), in addition to organometallic iridium complexes having a pyridine skeleton, 2, 3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum (II) (abbreviation: PtOEP) and other platinum complexes, and tris(1,3-diphenyl-1 ,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: E u(DBM) 3 (Phen)), tris[1-(2-thenoyl)-3,3,3-triflu oroacetonato](monophenanthroline)europium(III) (abbreviation: Eu(TT A) 3 (Phen)) and other rare earth metal complexes. Among the above, organometallic iridium complexes having a pyrimidine skeleton are particularly preferable because they are remarkably excellent in reliability and luminescence efficiency. In addition, organometallic iridium complexes having a pyrazine skeleton can obtain red luminescence with good chromaticity.

[0104] Note that the delayed fluorescence in TADF materials refers to luminescence that has the same spectrum as ordinary fluorescence but has a significantly long lifetime. The lifetime is 10 seconds or more, preferably 10 -6 seconds -3 or more. The above are examples. As TADF materials, specifically, fullerenes and their derivatives, acridine derivatives such as proflavine and eosin can be mentioned. Also, metal-containing porphyrins containing magnesium (Mg), zinc ( Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) can be mentioned. Examples of the metal-containing porph yrin include, for example, protoporphyrin-tin fluoride complex (SnF 2 (Proto IX)), mesoporphyrin-tin fluoride complex (SnF 2 (Meso IX)), hema toporphyrin-tin fluoride complex (SnF 2 (Hemato IX)), coproporph yrin tetramethyl ester-tin fluoride complex (SnF 2 (Copro III-4Me) ), octaethylporphyrin-tin fluoride complex (SnF 2 (OEP)), etioporph yrin-tin fluoride complex (SnF 2 (Etio I)), octaethylporphyrin-platinum chloride complex (PtCl (OEP)), etc. Furthermore, heteroaromatic compounds having a π-excessive heteroaromatic ring and a π-deficient heteroaromatic ring such as 2-biphenyl-4,6 2 (OEP)) can also be used. Note that a substance in which a π-excessive heteroaromatic ring and a π-deficient heteroaromatic ring are directly bonded has both the donor property of the π-excessive heteroaromatic ring and the acceptor property of the π-deficient heteroaromatic ring enhanced, and the energy difference between S and T becomes small, so it is particularly preferable. In addition, heteroaromatic compounds having a π-excessive heteroaromatic ring and a π-deficient heteroaromatic ring can also be used. Note that a substance in which a π-excessive heteroaromatic ring and a π-deficient heteroaromatic ring are directly bonded has both the donor property of the π-excessive heteroaromatic ring and the acceptor property of the π-deficient heteroaromatic ring enhanced, and the energy difference between S and T becomes small, so it is particularly preferable. 1 and T 1 The energy difference becomes small, so it is particularly preferable. That's all.

[0105] However, the materials that can be used for the above-described first organic compound 120 (host material), second organic compound 122 ( assist material), and third organic compound 124 (guest material) are not limited to these, and are combinations that can form an exciplex. As long as the emission spectrum of the exciplex overlaps with the absorption spectrum of the third organic compound 124 (guest material), and the peak of the emission spectrum of the exciplex is at a longer wavelength than the peak of the absorption spectrum of the third organic compound 124 (guest material).

[0106] In addition, when an electron transporting material is used for the first organic compound 120 (host material) and a hole transporting material is used for the second organic compound 122 (assist material), the carrier balance can be controlled by the mixing ratio. Specifically, it is preferable that the ratio of the first organic compound 120: second organic compound 122 is in the range of 1:9 to 9:1.

[0107] The electron transport layer 114 is a layer containing a material with high electron transport properties. In addition to the above-described electron transporting materials, tris(8-quinolinolato)aluminum (abbreviation: Alq 3 ), tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq 3 ), bis -(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq 2 ), Balq , Zn(BOX) 2 , bis[2-(2-hydroxyphenyl)benzothiazolato]lead (abbreviation: Zn(BTZ) ), etc. metal complexes can be used. Also, 2-(4- 2 biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole ​​​​​​​​R (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3, 4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 3-(4-tert -butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triaz -ole (abbreviation: TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphen yl)-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: p-EtTAZ ), bathophenanthroline (abbreviation: BPhen), bathocuproin (abbreviation: BCP), 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzO s) and other heteroaromatic compounds can also be used. Also, poly(2,5-pyridine-di yl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)- co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), poly[(9,9-dioct ylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl )] (abbreviation: PF-BPy) and other polymer compounds can also be used. The substances described here are mainly substances having an electron mobility of 10 -6 cm 2 / Vs or more. Note that, as long as the substance has higher electron transportability than holes, substances other than the above may be used as the electron transport layer 114.

[0108] Also, the electron transport layer 114 may be not only a single layer but also a layer formed by laminating two or more layers of the above substances.

[0109] The electron injection layer 115 is a layer containing a substance with high electron injection properties. In the electron injection layer 115, lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2 ) , compounds of alkali metals or alkaline earth metals such as lithium oxide (LiO x ) can be used. Also, rare earth metal compounds such as erbium fluoride (ErF ) can be used. Further, the substances constituting the above-described electron transport layer 114 can also be 3 used. Alternatively, a composite material formed by mixing an organic compound and an electron donor in the electron injection layer 115 may be used. Such a composite material has excellent electron injection properties and electron transport properties because electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material excellent in transporting the generated electrons. Specifically, for example, the substances constituting the above-described electron transport layer 114 (such as metal complexes and heteroaromatic compounds) can be

[0110] used. As the electron donor, any substance that exhibits electron-donating properties to the organic compound may be used. Specifically, alkali metals, alkaline earth metals, and rare earth metals are preferable, and examples include lithium, cesium, magnesium, calcium, erbium, ytterbium, etc. Also, alkali metal oxides and alkaline earth metal oxides are preferable, and examples include lithium oxide, calcium oxide, barium oxide, etc. Further, Lewis bases such as magnesium oxide can be used. Also, organic compounds such as tetrathiafulvalene (abbreviation: TTF) can be used. Note that the above-described hole injection layer 111, hole transport layer 112, light-emitting layer 113, electron transport layer 11 4, and electron injection layer 115 can each be formed by a vapor deposition method (including a vacuum vapor deposition method), an inkjet method, respectively.

[0111] ​​​​​​It can be formed by a method such as a coating method.

[0112] In addition, the light emitted from the light-emitting layer 113 of the above-described light-emitting element is taken out to the outside through either one or both of the first electrode 101 and the second electrode 103. Therefore, either one or both of the first electrode 101 and the second electrode 103 in the present embodiment are electrodes having translucency.

[0113] As described above, the light-emitting element shown in the present embodiment utilizes energy transfer using the overlap between the emission spectrum of the exciplex and the absorption spectrum of the third organic compound (guest material), so that the energy transfer efficiency can be increased, and thus a light-emitting element with high luminous efficiency can be realized.

[0114] In addition, the light-emitting element shown in the present embodiment has a configuration in which a fourth organic compound having a hole-transporting property used in the light-emitting layer and having a HOMO level lower than that of the second organic compound, and a fifth organic compound having a HOMO level higher than that of the second organic compound are provided in the hole-transporting layer. With such a configuration, the current efficiency of the light-emitting element can be increased, and the voltage of the light-emitting element, particularly the driving start voltage, can be lowered.

[0115] In addition, the light-emitting element shown in the present embodiment is an aspect of the present invention, and particularly has features in the configurations of the hole-transporting layer and the light-emitting layer. Therefore, by applying the configuration shown in the present embodiment, a passive matrix type light-emitting device, an active matrix type light-emitting device, etc. can be manufactured, and these are all included in the present invention.

[0116] Note that in the case of an active matrix type light-emitting device, the structure of the TFT is not particularly limited It is not. For example, staggered or inverse staggered TFTs can be appropriately used. Also, for the driving circuit formed on the TFT substrate, those composed of N-type and P-type TFTs are acceptable, or those composed of only one of N-type TFTs or P-type TFTs may also be acceptable. Furthermore, the crystallinity of the semiconductor film used for the TFT is not particularly limited. For example , an amorphous semiconductor film, a crystalline semiconductor film, or other oxide semiconductor films can be used.

[0117] Note that the configuration shown in this embodiment can be appropriately combined with the configuration shown in other embodiments and used .

[0118] (Embodiment 3) In this embodiment, as one aspect of the present invention, a light-emitting element having a plurality of light-emitting layers sandwiching a charge generation layer (hereinafter referred to as a tandem light-emitting element) will be described.

[0119] The light-emitting element shown in this embodiment is, as shown in FIG. 7(A), a tandem light-emitting element having a plurality of light-emitting layers (a first light-emitting layer 311 and a second light-emitting layer 31 2) between a pair of electrodes (a first electrode 30 1 and a second electrode 303).

[0120] In this embodiment, the first electrode 301 is an electrode that functions as an anode, and the second electrode 303 is an electrode that functions as a cathode. Note that the first electrode 301 and the second electrode 3 03 can use the same configuration as in Embodiment 2. Also, the plurality of light-emitting layers (the first light-emitting layer 311 and the second light-emitting layer 312) may have the same configuration as the light-emitting layers shown in Embodiment 1 or Embodiment 2, or either one may have the same configuration. That is, the first The first light-emitting layer 311 and the second light-emitting layer 312 may have the same structure or different structures. In addition, the configuration may be the same as that of the first or second embodiment. However, either or both of the first light-emitting layer 311 and the second light-emitting layer 312 are This has a configuration including the hole transport layer described in the first or second embodiment.

[0121] In addition, between the plurality of light-emitting layers (the first light-emitting layer 311 and the second light-emitting layer 312), a charge generation The charge generating layer 313 is disposed between the first electrode 301 and the second electrode 303. When a voltage is applied to the two layers, electrons are injected into one light-emitting layer and holes are injected into the other light-emitting layer. In the present embodiment, the first electrode 301 is electrically charged more than the second electrode 303. When a voltage is applied so that the potential becomes high, electrons are transferred from the charge generating layer 313 to the first light emitting layer 311. is injected into the second light-emitting layer 312, and holes are injected into the second light-emitting layer 312.

[0122] From the viewpoint of light extraction efficiency, the charge generating layer 313 is transparent to visible light. (Specifically, the transmittance of visible light through the charge generating layer 313 is preferably 40% or more.) In addition, the charge generating layer 313 has a lower conductivity than the first electrode 301 and the second electrode 303. It also works as a percentage.

[0123] The charge generation layer 313 is made of an organic compound having a high hole transporting property to which an electron acceptor is added. Even in the case of a structure in which an electron donor is added, the electron donor is added to an organic compound with high electron transport properties. Alternatively, both of these configurations may be laminated.

[0124] In the case where an electron acceptor is added to an organic compound having a high hole transporting property, As highly transportable organic compounds, for example, NPB, TPD, TDATA, MTDATA , aromatic amine compounds such as 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenyl amino]biphenyl (abbreviation: BSPB) can be used . The substances described here mainly have a hole mobility of 10 -6 cm 2 / Vs or more. However, as long as it is an organic compound with higher hole transportability than electrons, substances other than the above can be used .

[0125] In addition, as electron acceptors, 7,7,8,8-tetracyano-2,3,5,6-tetra fluorobenzoquinodimethane (abbreviation: F 4 -TCNQ), chloranil, etc. can be mentioned . In addition, transition metal oxides can be mentioned. Also, oxides of metals belonging to Groups 4 to 8 in the periodic table of elements can be mentioned. Specifically, vanadium oxide, niobium oxide , tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, oxide rhenium are preferable because of their high electron accepting properties. Among them, molybdenum oxide is particularly preferable because it is stable even in the atmosphere , has low hygroscopicity, and is easy to handle

[0126] On the other hand, in the case of a configuration in which an electron donor is added to an organic compound with high electron transportability , as the organic compound with high electron transportability, for example, Alq, Almq 3 , BeBq 2 , B Alq, etc., metal complexes having a quinoline skeleton or a benzoquinoline skeleton can be used . In addition, in addition, Zn(BOX) 2 , Zn(BTZ) 2 such as oxazole-based, thi ​A metal complex having an azole ligand or the like can also be used. Further, in addition to the metal complex PBD, OXD-7, TAZ, BPhen, BCP, etc. can also be used. Here The substances described have an electron mobility of 10 -6 cm 2 / Vs or more. Note As long as it is an organic compound with higher electron transportability than holes, substances other than the above can be used .

[0127] In addition, as the electron donor, an alkali metal, an alkaline earth metal, a rare earth metal, or a metal belonging to Group 13 of the periodic table and its oxide and carbonate can be used . Specifically, it is preferable to use lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide, cesium carbonate, etc. Also, an organic compound such as tetrathianaphthacene can be used as the electron donor . .

[0128] Note that by forming the charge generation layer 313 using the above-described materials, an increase in the driving voltage when the light-emitting layer is laminated can be suppressed .

[0129] In addition, in FIG. 7(A), a light-emitting element having two light-emitting layers was described. However, as shown in FIG. 7 (B), the same applies to a light-emitting element in which n (where n is 3 or more) light-emitting layers are laminated. Like the light-emitting element according to the present embodiment, when there are a plurality of light-emitting layers between a pair of electrodes, by disposing the charge generation layer 313 between the light-emitting layers, it is possible to emit light in a high-luminance region while keeping the current density low . ​​In order to maintain it, a long-life element can be realized. Also, in the case of applying it to lighting, since the voltage drop due to the resistance of the electrode material can be reduced, uniform light emission over a large area becomes possible. Also, a light-emitting device that can be driven at low voltage and has low power consumption can be realized.

[0130] Also, by making the emission colors of the respective light-emitting layers different, the entire light-emitting element can emit light of a desired color. For example, in a light-emitting element having two light-emitting layers, by making the emission color of the first light-emitting layer and the emission color of the second light-emitting layer be in a complementary color relationship, it is possible to obtain a light-emitting element that emits white light as a whole. Note that complementary colors refer to the relationship between colors that become achromatic when mixed. That is, when light obtained from substances that emit colors in a complementary color relationship is mixed, white light can be obtained.

[0131] The same applies to a light-emitting element having three light-emitting layers. For example, when the emission color of the first light-emitting layer is red, the emission color of the second light-emitting layer is green, and the emission color of the third light-emitting layer is blue, white light can be obtained as a whole for the light-emitting element.

[0132] Note that the configuration shown in this embodiment can be appropriately combined with the configurations shown in other embodiments and used.

[0133] (Embodiment 4) In this embodiment, a light-emitting device which is one aspect of the present invention will be described.

[0134] The light-emitting device shown in this embodiment has a microcavity structure that utilizes the resonance effect of light between a pair of electrodes, and as shown in FIG. 8, a pair of electrodes (reflective electrode 4 ​​​​​​​​A light-emitting element having at least an EL layer 455 between a reflective electrode 451 and a semi-transmissive / semi-reflective electrode 452, is provided in plural. The EL layer 455 has at least a hole transport layer (not shown) and a light-emitting layer 454 (454R, 454G, 454B), and may further include a hole injection layer, an electron transport layer, an electron injection layer, a charge generation layer, etc.

[0135] The first light-emitting element 450R has a structure in which a first transparent conductive layer 453a, an EL layer 45 5 including a first light-emitting layer 454B, a second light-emitting layer 454G, and a third light-emitting layer 454R in part, and a semi-transmissive / semi-reflective electrode 452 are sequentially stacked on a reflective electrode 451. The second light-emitting element 450G has a structure in which a second transparent conductive layer 453b, an EL layer 455, and a semi-transmissive / semi-reflective electrode 452 are sequentially stacked on a reflective electrode 451. The third light-emitting element 450B has a structure in which an EL layer 455 and a semi-transmissive / semi-reflective electrode 452 are sequentially stacked on a reflective electrode 451.

[0136] In the above light-emitting elements (the first light-emitting element 450R, the second light-emitting element 450G, and the third light-emitting element 450B), the reflective electrode 451, the EL layer 455, and the semi-transmissive / semi-reflective electrode 452 are common. In the first light-emitting layer 454B, light (λ ) having a peak in a wavelength range of 420 nm or more and 480 nm or less is emitted. In the second light-emitting layer 454G, light (λ ) having a peak in a wavelength range of 500 nm or more and 550 nm or less is emitted. In the third light-emitting layer 454R, light (λ B ) ) having a peak in a wavelength range of 600 nm or more and 760 nm or less is emitted. G ) ) R ) As a result, any of the light-emitting elements (the first light-emitting element 450R, the second light-emitting element 450G, and the ​​​​​Even in the light-emitting element 450B of 3, the light emission from the first light-emitting layer 454B, the second light-emitting layer 454G, and the third light-emitting layer 454R is superimposed, that is, broad light covering the visible light region can be emitted. From the above, the wavelength length is λ B < λ G < λ R in the relationship as described.

[0137] Each light-emitting element shown in this embodiment has a structure in which an EL layer 455 is sandwiched between a reflective electrode 451 and a semi-transmissive / semi-reflective electrode 45 2, and the light emitted in all directions from each light-emitting layer included in the EL layer 455 is resonated by the reflective electrode 451 and the semi-transmissive / semi-reflective electrode 452 having a function as a microcavity. The reflective electrode 451 is formed of a conductive material having reflectivity, and the reflectivity of visible light with respect to the film is 40% to 100%, preferably 70% to 100%, and its resistivity is 1 × 10 -2 Ωcm or less. Also, the semi-transmissive / semi-reflective electrode 452 is formed of a conductive material having reflectivity and a conductive material having light transmissivity, and the reflectivity of visible light with respect to the film is 20% to 80%, preferably 40% to 70%, and its resistivity is 1 × 10 - 2 Ωcm or less.

[0138] Also, in this embodiment, in each light-emitting element, by changing the thicknesses of the transparent conductive layers (the first transparent conductive layer 453a and the second transparent conductive layer 453b) provided in the first light-emitting element 450R and the second light-emitting element 4 50G respectively, for each light-emitting element, between the reflective electrode 451 and the semi-transmissive / semi-reflective electrode The optical distance between the electrodes 452 is changed. That is, the broadband light emitted from each light-emitting layer of each light-emitting element resonates between the reflective electrode 451 and the semi-transmissive / semi-reflective electrode 452, enhancing the light with a resonant wavelength and attenuating the light with a non-resonant wavelength. Therefore, by changing the optical distance between the reflective electrode 451 and the semi-transmissive / semi-reflective electrode 452 for each element, light of different wavelengths can be extracted. The broadband light emitted from each light-emitting layer of each light-emitting element can enhance the light with a resonant wavelength and attenuate the light with a non-resonant wavelength between the reflective electrode 451 and the semi-transmissive / semi-reflective electrode 452. Therefore, by changing the optical distance between the reflective electrode 451 and the semi-transmissive / semi-reflective electrode 452 for each element, light of different wavelengths can be extracted. The optical distance between the reflective electrode 451 and the semi-transmissive / semi-reflective electrode 452 is changed for each element, enabling the extraction of light of different wavelengths. Light of different wavelengths can be extracted.

[0139] Note that the optical distance (also referred to as the optical path length) is the actual distance multiplied by the refractive index, and in this embodiment, it represents the product of the actual film thickness and n (refractive index). That is, "Optical distance = actual film thickness × n". In this embodiment, it represents the product of the actual film thickness and n (refractive index). That is, "Optical distance = actual film thickness × n". Optical distance = actual film thickness × n.

[0140] Also, in the first light-emitting element 450R, the optical distance from the reflective electrode 451 to the semi-transmissive / semi-reflective electrode 452 is mλ / 2 (where m is a natural number of 1 or more). In the second light-emitting element 450G, the optical distance from the reflective electrode 451 to the semi-transmissive / semi-reflective electrode 452 is mλ / 2 (where m is a natural number of 1 or more). In the third light-emitting element 450B, the optical distance from the reflective electrode 451 to the semi-transmissive / semi-reflective electrode 452 is mλ / 2 (where m is a natural number of 1 or more). The optical distance from the reflective electrode 451 to the semi-transmissive / semi-reflective electrode 452 is mλ / 2 (where m is a natural number of 1 or more). R In the second light-emitting element 450G, the optical distance from the reflective electrode 451 to the semi-transmissive / semi-reflective electrode 452 is mλ / 2 (where m is a natural number of 1 or more). G where m is a natural number of 1 or more. In the third light-emitting element 450B, the optical distance from the reflective electrode 451 to the semi-transmissive / semi-reflective electrode 452 is mλ / 2 (where m is a natural number of 1 or more). The optical distance from the reflective electrode 451 to the semi-transmissive / semi-reflective electrode 452 is mλ / 2 (where m is a natural number of 1 or more). B where m is a natural number of 1 or more. is set.

[0141] From the above, from the first light-emitting element 450R, the light (λ) emitted mainly from the third light-emitting layer 454R included in the EL layer 455 is extracted. From the second light-emitting element 450G, the light (λ) emitted mainly from the second light-emitting layer 454G included in the EL layer 455 is extracted. From the third light-emitting element 450B, the light emitted mainly from the first light-emitting layer 454B included in the EL layer 455 is extracted. The light (λ) emitted from the third light-emitting layer 454R included in the EL layer 455 is extracted. R is extracted. From the second light-emitting element 450G, the light (λ) emitted mainly from the second light-emitting layer 454G included in the EL layer 455 is extracted. The light (λ) emitted from the second light-emitting layer 454G included in the EL layer 455 is extracted. G is extracted. From the third light-emitting element 450B, the light emitted mainly from the first light-emitting layer 454B included in the EL layer 455 is extracted. The light emitted (λ B ) is extracted. Note that the light extracted from each light-emitting element is emitted from the semi-transmissive ·semi-reflective electrode 452 side, respectively.

[0142] Also, in the above configuration, the optical distance from the reflective electrode 451 to the semi-transmissive·semi-reflective electrode 452 is strictly the distance from the reflection region in the reflective electrode 451 to the reflection region in the semi-transmissive·semi-reflective electrode 452. However, since it is difficult to accurately determine the position of the reflection region in the reflective electrode 451 or the semi-transmissive·semi-reflective electrode 452, it is assumed that an arbitrary position of the reflective electrode 451 and the semi-transmissive· semi-reflective electrode 452 is the reflection region, and it is assumed that the above-described effects can be sufficiently obtained.

[0143] Next, in the first light-emitting element 450R, among the light emitted from the third light-emitting layer 454R, the light (first reflected light) reflected by the reflective electrode 451 and returned causes interference with the light (first incident light) directly incident from the third light-emitting layer 454 R to the semi-transmissive·semi-reflective electrode 452. Therefore, the optical distance between the reflective electrode 451 and the third light-emitting layer 454R is adjusted to (2n -1)λ / 4 (where R n R is a natural number of 1 or more). By adjusting the optical distance, the phases of the first reflected light and the first incident light are matched, and the light emitted from the third light-emitting layer 454R can be amplified. R

[0144] Note that the optical distance between the reflective electrode 451 and the third light-emitting layer 454R is strictly the optical distance between the reflection region in the reflective electrode 451 and the light-emitting region in the third light-emitting layer 454R. However, since it is difficult to determine the reflection region in the reflective electrode 451 or the third light-emitting layer 454R accurately, Since it is difficult to precisely determine the position of the light-emitting region, it is assumed that arbitrary positions of the reflective electrode 451 and the third light-emitting layer 454R are the reflection region and the light-emitting region, respectively, so that the above-described effects can be sufficiently obtained. Next, in the second light-emitting element 450G, among the light emitted from the second light-emitting layer 454G, the light reflected by the reflective electrode 451 and returned (the second reflected light) causes interference with the light directly incident on the semi-transmissive / semi-reflective electrode 452 from the second light-emitting layer 454G (the second incident light). Therefore, the optical distance between the reflective electrode 451 and the second light-emitting layer 454G is adjusted to (2n - 1)λ / 4 (where n is a natural number of 1 or more). By adjusting the optical distance, the phases of the second reflected light and the second incident light are matched, and the light emitted from the second light-emitting layer 454G can be amplified. Note that the optical distance between the reflective electrode 451 and the second light-emitting layer 454G is strictly the optical distance between the reflection region in the reflective electrode 451 and the light-emitting region in the second light-emitting layer 454G. However, since it is difficult to precisely determine the positions of the reflection region in the reflective electrode 451 and the light-emitting region in the second light-emitting layer 454G, it is assumed that arbitrary positions of the reflective electrode 451 and the second light-emitting layer 454G are the reflection region and the light-emitting region, respectively, so that the above-described effects can be sufficiently obtained.

[0145] Next, in the third light-emitting element 450B, among the light emitted from the first light-emitting layer 454B, the light reflected by the reflective electrode 451 and returned (the third reflected light) is G G G

[0146] Note that the optical distance between the reflective electrode 451 and the second light-emitting layer 454G is strictly the optical distance between the reflection region in the reflective electrode 451 and the light-emitting region in the second light-emitting layer 454G. However, since it is difficult to precisely determine the positions of the reflection region in the reflective electrode 451 and the light-emitting region in the second light-emitting layer 454G, it is assumed that arbitrary positions of the reflective electrode 451 and the second light-emitting layer 454G are the reflection region and the light-emitting region, respectively, so that the above-described effects can be sufficiently obtained. Since it is difficult to precisely determine the position of the reflection region in the reflective electrode 451 and the position of the light-emitting region in the second light-emitting layer 454G, it is assumed that arbitrary positions of the reflective electrode 451 and the second light-emitting layer 454G are the reflection region and the light-emitting region, respectively, so that the above-described effects can be sufficiently obtained.

[0147] Next, in the third light-emitting element 450B, among the light emitted from the first light-emitting layer 454B, the light reflected by the reflective electrode 451 and returned (the third reflected light) ​​​​​​​​​​​​​​To cause interference with the light (third incident light) that is directly incident on the semi-transmissive / semi-reflective electrode 452 from B , the optical distance between the reflective electrode 451 and the first light-emitting layer 454B is adjusted to (2n B -1)λ B / 4 (where n B is a natural number of 1 or more). By adjusting the optical distance, the phases of the third reflected light and the third incident light are matched, and the light emission from the first light-emitting layer 454B can be amplified .

[0148] Note that the optical distance between the reflective electrode 451 and the first light-emitting layer 454B is strictly the optical distance between the reflection region in the reflective electrode 451 and the light-emitting region in the first light-emitting layer 454B . However, since it is difficult to precisely determine the positions of the reflection region in the reflective electrode 451 and the light-emitting region in the first light-emitting layer 454B, assuming arbitrary positions of the reflective electrode 451 and the first light-emitting layer 454B as the reflection region and the light-emitting region, respectively, it is assumed that the above-described effects can be sufficiently obtained .

[0149] Note that in the above configuration, each light-emitting element has a structure in which the EL layer has a plurality of light-emitting layers, but the present invention is not limited thereto. For example, in combination with the configuration of the tandem type (laminated type) light-emitting element described in Embodiment 3, a configuration in which a plurality of light-emitting layers are formed with a charge generation layer sandwiched between them in one light-emitting element may be used .

[0150] The light-emitting device shown in the present embodiment has a microcavity structure, and even if it has an EL layer with the same configuration , light of different wavelengths can be extracted for each light-emitting element, so that RGB painting is not required. Therefore, for reasons such as being easily able to achieve high definition ​​​It is advantageous for realizing full-colorization. Also, since it is possible to enhance the forward emission intensity of a specific wavelength, power consumption can be reduced. This configuration is particularly useful when applied to a color display (image display device) using three or more colors of pixels, but it may also be used for applications such as illumination. Moreover, since this becomes possible, power consumption can be reduced. This configuration is particularly useful when applied to a color display (image display device) using three or more colors of pixels, but it may also be used for applications such as illumination.

[0151] Note that the configuration shown in this embodiment can be used in appropriate combination with the configurations shown in other embodiments.

[0152] (Embodiment 5) In this embodiment, a light-emitting device having a light-emitting element which is one aspect of the present invention will be described.

[0153] Also, the above-described light-emitting device may be a passive matrix type light-emitting device or an active matrix type light-emitting device. Note that the light-emitting elements described in other embodiments can be applied to the light-emitting device shown in this embodiment.

[0154] In this embodiment, an active matrix type light-emitting device will be described with reference to FIG. 9.

[0155] Note that FIG. 9(A) is a top view showing the light-emitting device, and FIG. 9(B) is a cross-sectional view taken along the chain line A-B in FIG. 9(A). The active matrix type light-emitting device according to this embodiment includes a pixel portion 502 provided on an element substrate 501, a drive circuit portion (source line drive circuit) 503, and a drive circuit portion (gate line drive circuit) 504 (504a and 504b). The pixel portion 502, the drive circuit portion 503, and the drive circuit portion 504 are sealed between the element substrate 501 and a sealing substrate 506 by a sealing material 505.

[0156] ​​​​​​​​​​​ In addition, on the element substrate 501, a driving circuit section 503 and a driving circuit section 504 are provided. Signals (e.g., video signals, clock signals, start signals, reset signals, etc.) and potentials A wiring 507 is provided for connecting an external input terminal for transmitting the signal. An example of providing an FPC (flexible printed circuit) 508 as an external input terminal is shown below. Although only the FPC is shown here, the FPC also has a printed wiring board. The light emitting device in this specification may include a light emitting device itself. This includes not only the body but also the state in which an FPC or PWB is attached to it.

[0157] Next, the cross-sectional structure will be described with reference to FIG. A driver circuit portion 503 which is a source line driver circuit is formed in the pixel portion. 5, a pixel portion 502 is shown.

[0158] The driving circuit section 503 is a combination of an n-channel TFT 509 and a p-channel TFT 510. The circuit forming the driver circuit section is shown in FIG. It may be formed of various CMOS circuits, PMOS circuits, or NMOS circuits. In the embodiment, a driver integrated type in which a driving circuit is formed on a substrate is shown, but this is not necessarily required. In addition, the driving circuit can be formed externally instead of on the substrate.

[0159] The pixel section 502 includes a switching TFT 511, a current control TFT 512, and a current A first TFT 512 electrically connected to the wiring (source electrode or drain electrode) of the control TFT 512 The pixel electrode 513 is formed of a plurality of pixels including the first electrode 513. An insulating material 514 is formed. Here, a positive photosensitive acrylic resin is used for formation. In this embodiment, the first electrode 513 is used as an anode. .

[0160] Further, in order to make the coating property of the film laminated on the upper layer good, it is preferable to form a curved surface having a curvature at the upper end portion or the lower end portion of the insulating material 514. For example, when a positive photosensitive acrylic resin is used as the material of the insulating material 514, it is preferable to provide a curved surface having a radius of curvature (0.2 μm to 3 μm) at the upper end portion of the insulating material 514. Also, as the insulating material 514, either a negative photosensitive resin or a positive photosensitive resin can be used, and not only organic compounds but also inorganic compounds such as silicon oxide and silicon oxynitride can be used in both cases.

[0161]

[0162] On the first electrode 513, an EL layer 515 and a second electrode 516 are laminated and formed. The EL layer 515 is provided with at least a hole transport layer and a light emitting layer. The hole transport layer and the light emitting layer can apply the configurations shown in Embodiment 1 or Embodiment 2. In this embodiment, the second electrode 516 is used as a cathode.

[0162]

[0163] As the materials used for the first electrode 513, the EL layer 515, and the second electrode 516, the materials shown in Embodiment 2 can be used. Also, although not shown here, the second electrode 516 is electrically connected to an FPC 508 which is an external input terminal. .

[0163] In addition, in the cross-sectional view shown in FIG. 9(B), only one light-emitting element 517 is illustrated, but in the pixel portion 502, it is assumed that a plurality of light-emitting elements are arranged in a matrix. In the pixel portion 5 02, light-emitting elements capable of obtaining three types of light emission (R, G, B) are selectively formed respectively, and a light-emitting device capable of full-color display can be formed. Further, it may be a light-emitting device capable of full-color display by combining with a color filter.

[0164] Furthermore, by bonding the sealing substrate 506 to the element substrate 501 with the sealing material 505, a structure is formed in which the light-emitting element 517 is provided in a space 518 surrounded by the element substrate 501, the sealing substrate 506, and the sealing material 505. Note that the space 518 includes not only the case where it is filled with an inert gas (such as nitrogen or argon), but also a configuration filled with the sealing material 505.

[0165] Note that it is preferable to use an epoxy-based resin for the sealing material 505. Also, these materials are desirably materials that do not permeate moisture and oxygen as much as possible. In addition to a glass substrate or a quartz substrate, as a material used for the sealing substrate 506, FRP (Fiberglass-Reinforced Plastics), PVF (polyvinyl fluoride), polyester or a plastic substrate made of acrylic or the like can be used.

[0166] As described above, an active matrix type light-emitting device can be obtained.

[0167] Note that the configuration shown in this embodiment can be used by appropriately combining the configurations shown in other embodiments.

[0168] ​​​​​(Embodiment 6) In this embodiment, an electronic device including a part of the light-emitting device according to one aspect of the present invention shown in the above embodiment will be described. Examples of the electronic device include cameras such as video cameras and digital cameras, goggle-type displays, navigation systems, audio playback devices (such as car audio, audio components, etc.), computers, game devices, portable information terminals (mobile computers, mobile phones, smartphones, portable game machines, e-books, or tablet-type terminals etc.), and image playback devices equipped with a recording medium (specifically, a device equipped with a display device capable of playing back a recording medium such as a Digital Versatile Disc (DVD) and displaying the image). Specific examples of these electronic devices will be described with reference to FIGS. 10 and 11.

[0169] FIG. 10(A) shows a television device according to one aspect of the present invention, including a housing 611, a support base 612, a display unit 613, a speaker unit 614, a video input terminal 615, etc. In this television device, a light-emitting device according to one aspect of the present invention can be applied to the display unit 613. Since the light-emitting device according to one aspect of the present invention has a low driving voltage and high current efficiency, by applying the light-emitting device according to one aspect of the present invention, a television device with reduced power consumption can be obtained.

[0170] FIG. 10(B) shows a computer according to one aspect of the present invention, including a main body 621, a housing 622, a display unit 623, a keyboard 624, an external connection port 625, a pointing device 6 26, etc. In this computer, a light-emitting device according to one aspect of the present invention can be applied to the display unit 623. The light-emitting device according to one aspect of the present invention has a low driving voltage and high current efficiency. Therefore, by applying the light-emitting device according to one aspect of the present invention, a computer with reduced power consumption can be obtained.

[0171] FIG. 10(C) shows a mobile phone according to one aspect of the present invention, which includes a main body 631, a housing 632, a display unit 633, a voice input unit 634, a voice output unit 635, operation keys 636, an external connection port 6 37, an antenna 638, etc. In this mobile phone, the display unit 633 can apply the light-emitting device according to one aspect of the present invention. The light-emitting device according to one aspect of the present invention has a low driving voltage and high current efficiency. Therefore, by applying the light-emitting device according to one aspect of the present invention, a mobile phone with reduced power consumption can be obtained.

[0172] FIG. 10(D) shows a camera according to one aspect of the present invention, which includes a main body 641, a display unit 642, a housing 643, an external connection port 644, a remote control receiving unit 645, an imaging unit 646, a battery 6 47, a voice input unit 648, operation keys 649, an eyepiece 650, etc. In this camera

[0173] FIG. 11 shows an example of a portable terminal according to one aspect of the present invention. FIGS. 11(A), 11(B ), and FIG. 11(C) show the portable terminal 5000, and FIG. 11(D) shows the portable terminal 60 00.

[0174] In the portable terminal 5000 shown in FIGS. 11(A), 11(B), and FIG. 11(C), ​FIG. 11(A) shows a front view, FIG. 11(B) shows a side view, and FIG. 11(C) shows a rear view, respectively. In addition, in the portable terminal 6000 shown in FIG. 11(D), a front view is shown.

[0175] The portable terminal 5000 includes a housing 5001, a display unit 5003, a power button 5005, a front camera 5007, a rear camera 5009, a first external connection terminal 5011, and a second external connection terminal 5013, etc.

[0176] In addition, the display unit 5003 is incorporated in the housing 5001 and can also be used as a touch panel. For example, icons 5015, etc. can be displayed on the display unit 5003 to perform operations such as email and schedule management. Also, in the housing 5001, a front camera 5007 is incorporated on the front side, and the user's image can be captured. Also, in the housing 5001, a rear camera 5009 is incorporated on the rear side, and the image on the opposite side of the user can be captured. Also, the housing 5001 is provided with a first external connection terminal 5011 and a second external connection terminal 5013. For example, the first external connection terminal 5011 can output audio to earphones, etc., and the second external connection terminal 5013 can transfer data, etc.

[0177] Next, the portable terminal 6000 shown in FIG. 11(D) includes a first housing 6001, a second housing 6 003, a hinge portion 6005, a first display unit 6007, a second display unit 6009, a power button 6011, a first camera 6013, a second camera 6015, etc.

[0178] ​Also, the first display unit 6007 is incorporated in the first housing 6001, and the second display unit 6009 is incorporated in the second housing 6003. The first display unit 6007 and the second display unit 6009, for example, use the first display unit 6007 as a display panel and the second display unit 6009 as a touch panel. By checking the text icon 6017 displayed on the first display unit 6007 and using the icon 6019 or also the keyboard 6021 (keyboard image displayed on the second display unit 6009) displayed on the second display unit 6009, image selection, character input, etc. can be performed. Of course, the first display unit 6007 may be a touch panel, the second display unit 6009 may be a display panel, or both the first display unit 6007 and the second display unit 6009 may be touch panels.

[0179] Also, the first housing 6001 and the second housing 6003 are connected by a hinge portion 6005 and can be opened and closed between the first housing 6001 and the second housing 6003. With such a configuration, when carrying the portable terminal 6000, by combining the first display unit 6007 incorporated in the housing 6001 and the second display unit 6009 incorporated in the second housing 6003, the surfaces (for example, plastic substrates, etc.) of the first display unit 6007 and the second display unit 6009 can be protected, which is

[0180] preferable. Also, the first housing 6001 and the second housing 6003 may be configured to be separable by the hinge portion 6005 (so-called convertible type). With such a configuration, for example, the first housing 6001 can be placed vertically and the second housing 6003 Since the usage range is wide, it is suitable.

[0181] Also, the first camera 6013 and the second camera 6015 can be used to capture 3D images. It is also possible.

[0182] Also, the portable terminal 5000 and the portable terminal 6000 may be configured to be able to wirelessly transmit and receive information. For example, it is also possible to configure them to connect to the Internet or the like wirelessly and purchase and download desired information. For example, it is also possible to configure them to connect to the Internet or the like wirelessly and purchase and download desired information. It is also possible to configure them to connect to the Internet or the like wirelessly and purchase and download desired information.

[0183] Also, the portable terminal 5000 and the portable terminal 6000 can have functions such as displaying various information (still images, moving images, text images, etc.), displaying a calendar, date, or time on the display unit, a touch input function for touch input operation or editing of the information displayed on the display unit, a function of controlling processing by various software (programs), etc. Further, a light sensor that can optimize the display brightness according to the amount of external light, a gyroscope, a sensor that detects the inclination of an acceleration sensor, and other detection devices may be incorporated. For example, it is also possible to configure them to connect to the Internet or the like wirelessly and purchase and download desired information. For example, it is also possible to configure them to connect to the Internet or the like wirelessly and purchase and download desired information. For example, it is also possible to configure them to connect to the Internet or the like wirelessly and purchase and download desired information. For example, it is also possible to configure them to connect to the Internet or the like wirelessly and purchase and download desired information. For example, it is also possible to configure them to connect to the Internet or the like wirelessly and purchase and download desired information.

[0184] In the display unit 5003 of the portable terminal 5000, and in the first display unit 6007, and / or the second display unit 6009 of the portable terminal 6000, the light-emitting device according to one aspect of the present invention can be applied. Since the light-emitting device according to one aspect of the present invention has a low driving voltage and high current efficiency, by applying the light-emitting device according to one aspect of the present invention, a portable terminal with reduced power consumption can be obtained. In the display unit 5003 of the portable terminal 5000, and in the first display unit 6007, and / or the second display unit 6009 of the portable terminal 6000, the light-emitting device according to one aspect of the present invention can be applied. Since the light-emitting device according to one aspect of the present invention has a low driving voltage and high current efficiency, by applying the light-emitting device according to one aspect of the present invention, a portable terminal with reduced power consumption can be obtained. In the display unit 5003 of the portable terminal 5000, and in the first display unit 6007, and / or the second display unit 6009 of the portable terminal 6000, the light-emitting device according to one aspect of the present invention can be applied. Since the light-emitting device according to one aspect of the present invention has a low driving voltage and high current efficiency, by applying the light-emitting device according to one aspect of the present invention, a portable terminal with reduced power consumption can be obtained. In the display unit 5003 of the portable terminal 5000, and in the first display unit 6007, and / or the second display unit 6009 of the portable terminal 6000, the light-emitting device according to one aspect of the present invention can be applied. Since the light-emitting device according to one aspect of the present invention has a low driving voltage and high current efficiency, by applying the light-emitting device according to one aspect of the present invention, a portable terminal with reduced power consumption can be obtained. In the display unit 5003 of the portable terminal 5000, and in the first display unit 6007, and / or the second display unit 6009 of the portable terminal 6000, the light-emitting device according to one aspect of the present invention can be applied. Since the light-emitting device according to one aspect of the present invention has a low driving voltage and high current efficiency, by applying the light-emitting device according to one aspect of the present invention, a portable terminal with reduced power consumption can be obtained.

[0185] As described above, the application range of the light-emitting device according to one aspect of the present invention is extremely wide, and by applying this light-emitting device, It can be applied to electronic devices in all fields. By using the light-emitting device according to one aspect of the present invention it is possible to obtain an electronic device with reduced power consumption.

[0186] In addition, the light-emitting device according to one aspect of the present invention can also be used as a lighting device. A specific example of the lighting device will be described with reference to FIG. 12.

[0187] FIG. 12(A) shows an example of a liquid crystal display device using the light-emitting device according to one aspect of the present invention as a backlight. The liquid crystal display device shown in FIG. 12(A) includes a housing 701, a liquid crystal panel 702, a backlight 703, and a housing 704. The liquid crystal panel 702 is connected to a driver IC 705. The backlight 703 uses the light-emitting device according to one aspect of the present invention, and current is supplied through a terminal 706. By using the light-emitting device according to one aspect of the present invention as the backlight of the liquid crystal display device in this way, a backlight with low power consumption can be obtained. In addition, the light-emitting device according to one aspect of the present invention is a surface-emitting lighting device and can be enlarged in area, so the area of the backlight can also be enlarged. Therefore, a liquid crystal display device with low power consumption and a large area can be obtained.

[0188] FIG. 12(B) shows an example of using the light-emitting device according to one aspect of the present invention as an electric stand which is a lighting device. The electric stand shown in FIG. 12(B) includes a housing 801 and a light source 802. The light-emitting device according to one aspect of the present invention is used as the light source 802. Since a high current efficiency can be obtained at a low driving voltage, by applying the light-emitting device according to one aspect of the present invention, it is possible to obtain an electric stand with low power consumption.

[0189] ​​​​​FIG. 12(C) shows an example in which the light-emitting device according to one embodiment of the present invention is used as an indoor lighting device 901 Since the light-emitting device according to one embodiment of the present invention can be made larger in area, it can be used as a large-area lighting device In addition, since the light-emitting device according to one embodiment of the present invention has a low driving voltage and high current efficiency, by applying the light-emitting device according to one embodiment of the present invention, a lighting device with low power consumption can be obtained. Thus, in a room where the light-emitting device according to one embodiment of the present invention is used as the indoor lighting device 9 01, a television device 9 02 according to one embodiment of the present invention as described in FIG. 10(A) can be installed to view public broadcasts and movies .

[0190] Note that this embodiment can be appropriately combined with other embodiments

Example

[0191] In this example, a light-emitting element (light-emitting element 1) according to one embodiment of the present invention and a comparative light-emitting element (comparative light-emitting element 2) will be described with reference to FIG. 13. In addition, the chemical formulas of the materials used in this example are shown below .

[0192]

Chemical formula

[0193]

Chemical formula

[0194] The manufacturing methods of the light-emitting element 1 and the comparative light-emitting element 2 of this example are shown below

[0195] (Light-emitting element 1) First, on the substrate 1100, indium tin oxide containing silicon or silicon oxide compound (ITO-SiO 2 ​, which is abbreviated as ITSO hereinafter, was formed by sputtering , the first electrode 1101 was formed. The composition of the target used was In 2 O 3 :Sn O 2 :SiO 2 = 85:10:5 [wt%]. The film thickness of the first electrode 1101 was , 110 nm, and the electrode area was 2 mm × 2 mm. Here, the first electrode 1101 is an electrode that functions as the anode of the light-emitting element.

[0196] Next, as a pretreatment for forming a light-emitting element on the substrate 1100, the substrate surface was washed with water and baked at 200 °C for 1 hour, and then UV ozone treatment was performed for 370 seconds.

[0197] Then, the substrate was introduced into a vacuum evaporation apparatus whose inside was evacuated to about 10 -4 Pa, and in the heating chamber of the vacuum evaporation apparatus, vacuum baking was performed at 170 °C for 30 minutes, and then the substrate 1100 was allowed to cool for about 30 minutes.

[0198] Next, with the surface on which the first electrode 1101 is formed facing downward, the substrate 1100 on which the first electrode 1101 is formed was fixed to the substrate holder provided in the vacuum evaporation apparatus, and after evacuating to about 10 -4 Pa, on the first electrode 1101, by a vapor deposition method using resistance heating, 4 ,4’,4’’-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation : DBT3P-II) and molybdenum oxide were co-evaporated to form the hole injection layer 1111 . The film thickness was 40 nm, and the ratio of DBT3P-II (abbreviation) to molybdenum oxide was adjusted to 4:2 (= DBT3P-II: molybdenum oxide) by weight ratio.

[0199] ​Next, on the hole injection layer 1111, 4-phenyl-4'-(9-phenylfluoren-9 -yl)triphenylamine (abbreviation: BPAFLP) and 3-[N-(9-phenylcarb azol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PC zPCA1) were co-evaporated to form the hole transport layer 1112. The film thickness was 2 0 nm, and the ratio of BPAFLP (abbreviation) to PCzPCA1 (abbreviation) was adjusted to 0.5 :0.5 (=BPAFLP:PCzPCA1) by weight.

[0200] In the hole transport layer 1112, BPAFLP (abbreviation) is the fourth organic compound and PCzPCA1 (abbreviation) is the fifth organic compound.

[0201] Next, on the hole transport layer 1112, 2mDBTPDBq-II (abbreviation), 4-phenyl -4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), and (acetylacetonato)bis(6-tert-butyl-4-phenyl pyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm) 2 (acac) ) were co-evaporated to form the first light-emitting layer 1113a. Here, the weight ratio of 2mDBTPDBq -II (abbreviation), PCBA1BP (abbreviation), and [Ir(tBuppm) 2 (acac) (abbreviation) was adjusted to 0.8:0.2:0.06 (=2mDBTPDBq-II:PC BA1BP:[Ir(tBuppm) 2 (acac)]). Also, the film thickness of the first light-emitting layer 1113a was 20 nm.

[0202] In the first light-emitting layer 1113a, 2mDBTPDBq-II (abbreviation) is the first organic compound (host material), and PCBA1BP (abbreviation) is the second organic compound (a hole transport material), and [Ir(tBuppm) 2 (acac)] (abbreviation) is the third organic compound (guest material).

[0203] Next, 2mDBTPDBq-II (abbreviation), PCBA 1BP (abbreviation), and [Ir(tBuppm) 2 (acac)] (abbreviation) were co-evaporated on the first light-emitting layer 1113a to form the second light-emitting layer 1113b. Here, the weight ratio of 2mDBTPDBq-II (abbreviation), PC BA1BP (abbreviation), and [Ir(tBuppm) 2 (acac)] (abbreviation) was adjusted to 0.8:0.2:0.05 (= 2mDBTPDBq-II:PCBA1BP:[Ir( tBuppm) 2 (acac)]). Also, the film thickness of the second light-emitting layer 1113 b was set to 20 nm.

[0204] In the second light-emitting layer 1113b, 2mDBTPDBq-II (abbreviation) is the first organic compound (host material), and PCBA1BP (abbreviation) is the second organic compound (a hole transport material), and [Ir(tBuppm) 2 (acac)] (abbreviation) is the third organic compound (guest material).

[0205] Next, 2mDBTPDBq-II (abbreviation) was formed into a film with a thickness of 10 nm on the second light-emitting layer 1113b to form the first electron transport layer 1114a.

[0206] Next, bathophenanthroline (abbreviation: BPhen) was deposited on the first electron transport layer 1114a to form a film with a thickness of 20 nm, thereby forming the second electron transport layer 1114b.

[0207] Next, lithium fluoride (LiF) was deposited on the second electron transport layer 1114b with a film thickness of 1 nm to form the electron injection layer 1115.

[0208] Finally, as the second electrode 1103 that functions as a cathode, aluminum (Al) was deposited to a film thickness of 20 0 nm to fabricate the light-emitting device 1 of this example.

[0209] In the deposition process described above, all depositions used the resistance heating method.

[0210] (Comparative light-emitting device 2) The structure of the hole transport layer of the comparative light-emitting device 2 is different from that of the light-emitting device 1, and the other structures are the same. Only the different structures are described below.

[0211] The hole transport layer 111 2 was formed by depositing BPAFLP (abbreviation) on the hole injection layer 1111. The film thickness was 20 nm.

[0212] The device structures of the light-emitting device 1 and the comparative light-emitting device 2 obtained as described above are shown in Table 1.

[0213]

Table 1

[0214] Next, the hole transport layer used in the light-emitting device 1 and the comparative light-emitting device 2 of this example, the first light-emitting layer and the electrochemical properties (HOMO level and LUMO level) of each thin film of BPAFLP (abbreviation), PCzPCA1 (abbreviation), and PCBA1BP (abbreviation) used in the second light-emitting layer were measured A1BP (abbreviation) were measured fixed (measurement instrument: manufactured by Riken Keiki Co., Ltd., AC-2). The measurement of the electrochemical properties of each thin film was performed as follows.

[0215] The value of the HOMO level was obtained by converting the value of the ionization potential measured by ultraviolet photoelectron spectroscopy in air (manufactured by Riken Keiki Co., Ltd., AC-2) to a negative value. Also, the value of the LUMO level was obtained by measuring the absorption spectrum data of each thin film and determining the absorption edge from a Tauc plot assuming direct transition using the absorption spectrum data, and adding the absorption edge as the optical energy gap to the value of the HOMO level. The measurement results of the electrochemical properties of each thin film are shown in Table 2.

[0216]

[0217] [Table 2]

[0218] From Table 2, the HOMO level of BPAFLP (abbreviation) was -5.63 eV, the LUMO level was - 2.29 eV, and the band gap (Bg) was 3.34 eV. Also, the HOMO level of PCzPCA1 (abbreviation) was -5.17 eV, the LUMO level was -2.26 eV, and the band gap (Bg) was 2.91 eV. Also, the HOMO level of PCBA1BP (abbreviation) was -5.42 eV, the LUMO level was -2.21 eV, and the band gap (Bg) was 3.21 eV.

[0219] Also, from Tables 1 and 2, the hole transport layers of the light-emitting element 1 of this example and the comparative light-emitting element 2, the materials and HOMO levels of the light-emitting layer (second organic compound) are shown in Table 3.

[0220] [Table 3]​​​​

[0221] As shown in Table 3, the hole transport layer of the light-emitting element 1 of this example is the fourth organic compound below the HOMO level of the second organic compound (assist material) PCBA1BP (abbreviation), which is B PAFLP (abbreviation) is used, and PCzPCA1 (abbreviation) is used as the fifth organic compound with a higher HOMO level than the second organic compound (assist material) PCBA1BP ( abbreviation). abbreviation). On the other hand, the comparative light-emitting element 2 is composed of one type of organic compound (BPAFLP (abbreviation )) with a lower HOMO level than the second organic compound (assist material) PC BA1BP (abbreviation).

[0222] Next, the light-emitting element 1 and the comparative light-emitting element 2 were sealed with a glass substrate in a glove box under a nitrogen atmosphere so that each light-emitting element was not exposed to the atmosphere (applying a sealing material around the element and performing heat treatment at 80 °C for 1 hour during sealing). Then, the operating characteristics of these light-emitting elements were measured. The measurement was performed at room temperature (atmosphere maintained at 25 °C).

[0223] The current density-luminance characteristics of the light-emitting element 1 and the comparative light-emitting element 2 are shown in FIG. 14. In FIG. 14, the horizontal axis represents the current density (mA / cm ), and the vertical axis represents the luminance (cd / m 2 ). Also, the voltage-luminance characteristics of the light-emitting 2 element 1 and the comparative light-emitting element 2 are shown in FIG. 15. In FIG. 15, the horizontal axis represents the voltage (V), and the vertical axis represents the luminance (cd / m ). Also, the luminance-current efficiency characteristics of the light-emitting element 1 and the comparative light-emitting element 2 2 are shown in FIG. 16. In FIG. 16, the horizontal axis represents the luminance (cd / m ), and the vertical axis represents the luminance (cd / m 2 ).​​ The vertical axis represents the current efficiency (cd / A). Also, the voltage-current characteristics of the light-emitting element 1 and the comparative light-emitting element 2 are shown in Fig. 17. In Fig. 17, the horizontal axis represents the voltage (V), and the vertical axis represents the current (mA). Also, the emission spectra of the light-emitting element 1 and the comparative light-emitting element 2 are shown in Fig. 18. In Fig. 18, the horizontal axis represents the wavelength (nm), and the vertical axis represents the emission intensity (arbitrary unit). Note that in Fig. 18, the data of each light-emitting element are shown approximately overlapping. Also, the luminance-power efficiency characteristics (lm / W) of the light-emitting element 1 and the comparative light-emitting element 2 are shown in Fig. 19. As shown in Fig. 19, the power efficiency near 1000 cd / m² of the light-emitting element 1 is 105 (lm / W), and the power efficiency near 1000 cd / m² of the comparative light-emitting element 2 is 93 (lm / W). Thus, it was confirmed that the light-emitting element according to one aspect of the present invention is an element that is 12 (lm / W) higher than the comparative light-emitting element 2. Also, the voltage (V), current density

[0224] (mA / cm²), CIE chromaticity coordinates (x, y), current efficiency (cd / A), and external quantum efficiency 2 (%) near a luminance of 1000 cd / m² for each light-emitting element are shown in Table 4. As shown in Table 4, the CIE chromaticity coordinates of the light-emitting element 1 with a luminance of 1112 cd / m² were (x, y 2 ) = (0.43, 0.56). Also, the comparative light-emitting element 2 with a luminance of 1037 cd / m² W). Thus, it was confirmed that the light-emitting element according to one aspect of the present invention is an element that is 12 (lm / W) higher than the comparative light-emitting element 2. (lm / W) high was confirmed.

[0225] Also, when the luminance of each light-emitting element is near 1000 cd / m², the voltage (V), current density 2 (mA / cm²), CIE chromaticity coordinates (x, y), current efficiency (cd / A), and external quantum efficiency (mA / cm²), CIE chromaticity coordinates (x, y), current efficiency (cd / A), external quantum efficiency 2 %) are shown in Table 4. %) are shown in Table 4.

[0226]

Table 4

[0227] As shown in Table 4, the CIE chromaticity coordinates of the light-emitting element 1 with a luminance of 1112 cd / m² were (x, y 2 ) = (0.43, 0.56). Also, the CIE chromaticity coordinates of the comparative light-emitting element 2 with a luminance of 1037 cd / m² ) = (0.43, 0.56). Also, the CIE chromaticity coordinates of the comparative light-emitting element 2 with a luminance of 1037 cd / m² 2 were (x, y The CIE chromaticity coordinates were (x, y) = (0.43, 0.56).

[0228] Also, the voltage of the light-emitting element 1 with a luminance of 1112 cd / m 2 was 2.6 V, and the current efficiency was 87 cd / A. Also, the voltage of the comparative light-emitting element 2 with a luminance of 1037 cd / m 2 was 2.9 V and the current efficiency was 85 cd / A.

[0229] Therefore, it was confirmed that the light-emitting element 1, which is one aspect of the present invention, can lower the voltage by 0.3 V compared with the comparative light-emitting element 2, and the current efficiency is equal to or higher. Also, as shown in FIG. 17, it was confirmed that the light-emitting element 1 can lower the driving start voltage compared with the comparative light-emitting element 2.

[0230] As described above, the light-emitting element, which is one aspect of the present invention, has a fourth organic compound below the HOMO level of the second organic compound having hole-transporting properties used in the light-emitting layer, and a fifth organic compound having a higher HOMO level than the second organic compound, and is configured to have them in the hole-transporting layer. By adopting such a configuration, the driving voltage of the light-emitting element can be lowered and the current efficiency can be increased.

[0231] Note that the PL peak wavelength of the thin film of the first organic compound (2mDBTPDB q-II) used in the light-emitting layer of this example (light-emitting element 1) is 426 nm, and the PL peak wavelength of the second organic compound (PCBA1BP) is 416 nm, but the PL peak wavelength of the mixed film of these is 519 nm and it was found that there is a long-wavelength shift. Therefore, these two types of organic compounds are a combination that forms an exciplex.

[0232] Thus, in the light-emitting element 1, the fifth organic compound (PCzPC A1) having a higher HOMO level than the second organic compound (PCBA1BP) that contributes to the formation of the exciplex in the light-emitting layer is added to the hole transport layer, so that the driving start voltage can be made lower than that of the comparative light-emitting element 2 to which it is not added.

[0233] In addition, when PCzPCA1 is added to the light-emitting layer instead of PCBA1BP as the second organic compound, the driving start voltage can be made as low as that of the light-emitting element 1. However, since PCzPCA1 has a higher HOMO level than PCBA1BP, the emission wavelength of the exciplex formed by the first organic compound (2m DBTPDBq-II) and PCzPCA1 is 571n m, which is a long-wavelength shift compared to the case of PCBA1BP (519 nm). Therefore, when a green phosphorescent material is used in the light-emitting layer as in this example, it becomes difficult to excite the green phosphorescent material, and the luminous efficiency (external quantum efficiency) decreases. On the other hand, in the present invention (light-emitting element 1), there is no such problem. That is, the configuration of one aspect of the present invention is an effective means particularly for reducing the voltage without impairing the luminous efficiency in green and blue light-emitting elements having a large energy gap (that is, a high driving start voltage in principle).

[0234] (Reference Example 1) A synthesis example of (acetylacetonato)bis(6-tert-butyl-4-phenyl pyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm) 2 (acac) ) used in the above example will be specifically illustrated. The structure of [Ir(tBuppm) 2 (acac)] is shown below.

[0235] [Chemical formula]

[0236] <Step 1; Synthesis method of 4-tert-butyl-6-phenylpyrimidine (abbreviation: HtBuppm ) First, 22.5 g of 4,4-dimethyl-1-phenylpentane-1,3-dione and 50 g of form amide were placed in a round-bottom flask equipped with a reflux condenser, and the inside was purged with nitrogen. By heating this reaction vessel, the reaction solution was refluxed for 5 hours. Then, this solution was poured into an aqueous sodium hydroxide solution, and the organic layer was extracted with dichloromethane. The obtained organic layer was washed with water and saturated saline solution, and dried over magnesium sulfate. The dried solution was filtered. After distilling off the solvent of this solution , the obtained residue was purified by silica gel column chromatography using hexane:ethyl acetate = 10:1 (volume ratio) as the developing solvent to obtain the pyrimidine derivative HtBup pm (colorless oil, yield 14%). The synthesis scheme of Step 1 is shown in the following (a-1). Shown

[0237] [Chemical formula]

[0238] <Step 2; Synthesis of di-μ-chloro-bis[bis(6-tert-butyl-4-phenylpyr midinato)iridium(III)] (abbreviation: [Ir(tBuppm) 2 Cl] 2 ) Method Next, 15 mL of 2-ethoxyethanol, 5 mL of water, 1.49 g of HtBup pm obtained in the above Step 1, and 1.04 g of iridium chloride hydrate (IrCl 3 ·H 2 O) were placed in a reflux condenser It was placed in a attached eggplant flask, and the inside of the flask was replaced with argon. Then, microwave (2. 45 GHz 100 W) was irradiated for 1 hour to cause a reaction. After distilling off the solvent, the obtained residue was suction filtered and washed with ethanol to obtain a dinuclear complex [Ir(tBuppm) 2 Cl] 2 ( yellowish green powder, yield 73%). The synthesis scheme of Step 2 is shown in (a-2) below.

[0239]

Chemical formula

[0240] <Step 3; Synthesis method of bis(6-tert-butyl-4-phenylpyrimidinato)(acetylacetonato)iridium(III) (abbreviation: [Ir(tBuppm) (acac)]] 2 > Furthermore, 40 mL of 2-ethoxyethanol, 1.61 g of the dinuclear complex [Ir(t Buppm) 2 Cl] 2 obtained in Step 2 above, 0.36 g of acetylacetone, and 1 .27 g of sodium carbonate were placed in an eggplant flask equipped with a reflux tube, and the inside of the flask was replaced with argon. Then microwave (2.45 GHz 100 W) was irradiated for 60 minutes to cause a reaction. After distilling off the solvent, the obtained residue was suction filtered with ethanol and washed with water and ethanol. This solid was dissolved in dichloromethane and filtered through a filter aid laminated in the order of celite (Wako Pure Chemical Industries, Ltd., catalog number: 531- 16855), alumina, and celite. The solid obtained by distilling off the solvent was recrystallized with a mixed solvent of dichloromethane and hexane to obtain the target product as a yellow powder (yield 68%). The synthesis scheme of Step 3 is shown in (a- below. as shown in 3).

[0241] [Chemical formula]

[0242] In addition, the compound obtained by the above synthesis method was measured by nuclear magnetic resonance spectroscopy ( 1 1H-NMR). From the measurement results, [Ir(tBuppm) 2 (acac)] (abbreviation) was obtained . It was found that

[0243] The 1H-NMR data of the obtained substance are shown below. 1 1H-NMR.δ(CDCl 1 ): 1.50 (s, 18H), 1.79 (s, 6H), 3 5.26 (s, 1H), 6.33 (d, 2H), 6.77 (t, 2H), 6.85 (t, 2H), 7.70 (d, 2H), 7.76 (s, 2H), 9.02 (s, 2H).

[0244] (Reference Example 2) The T levels of 2mDBTPDBq-II (abbreviation), PCBA1BP (abbreviation), and BPAFLP (abbreviation) used in the light-emitting element in the above-described example were measured. 1 The measurement of the T 1 level was performed by measuring the phosphorescence of each substance and converting the phosphorescence emission wavelength into electron volts . As the measurement conditions, each substance was irradiated with excitation light of 325 nm, and the measurement was performed at a measurement temperature of 10 K. The measurement of the energy level is more accurate when calculated from the absorption wavelength than from the emission wavelength. However, since the absorption of the T level is extremely weak and difficult to measure 1 , here, the peak wavelength located on the shortest wavelength side of the phosphorescence spectrum is measured to obtain the T level.1 The level was determined. Therefore, it is assumed that the measured value contains some errors.

[0245] The measured phosphorescence of 2mDBTPDBq-II (abbreviation) is shown in Fig. 20, the measured phosphorescence of PCBA1BP ( abbreviation) is shown in Fig. 21, and the measured phosphorescence of BPAFLP (abbreviation) is shown in Fig. 22 respectively. Also, the measurement results are summarized in Table 5. As can be seen from these results, 2mDBTPDBq-II (abbreviation) used as the first organic compound and in the above-described example, compared with PCBA1BP (abbreviation) used as the second organic compound, BPAFLP (abbreviation) corresponding to the fourth organic compound used in the hole transport layer has a higher T level. 1 It can be seen that the level is high.

[0246]

Table 5

Explanation of Reference Signs

[0247] 100 Substrate 101 First electrode 103 Second electrode 111 Hole injection layer 112 Hole transport layer 112a Hole transport layer 112b Hole transport layer 112c Hole transport layer 113 Light-emitting layer 114 Electron transport layer 115 Electron injection layer 120 First organic compound 122 Second organic compound 124 Third organic compound 126 Fourth organic compound 128 Fifth organic compound 301 First electrode 303 Second electrode 311 First light-emitting layer 312 Second light-emitting layer 313 Charge generation layer 450R First light-emitting element 450G Second light-emitting element 450B Third light-emitting element 451 Reflective electrode 452 Semi-transmissive / semi-reflective electrode 453a First transparent conductive layer 453b Second transparent conductive layer 454 Light-emitting layer 454B First light-emitting layer 454G Second light-emitting layer 454R Third light-emitting layer 455 EL layer 501 Element substrate 502 Pixel portion 503 Driving circuit portion 504 Driving circuit portion 505 Sealing material 506 Sealing substrate 507 Wiring 508 FPC 509 n-channel type TFT 510 p-channel type TFT 511 Switching TFT 512 Current control TFT 513 First electrode 514 Insulator 515 EL layer 516 Second electrode 517 Light-emitting element 518 Space 611 Housing 612 Support stand 613 Display portion 614 Speaker portion 615 Video input terminal 621 Main body 622 Housing 623 Display portion 624 Keyboard 625 External connection port 626 Pointing device 631 Main body 632 Housing 633 Display unit 634 Voice input unit 635 Voice output unit 636 Operation key 637 External connection port 638 Antenna 641 Main body 642 Display unit 643 Housing 644 External connection port 645 Remote control receiver 646 Image receiving unit 647 Battery 648 Voice input unit 649 Operation key 650 Eyepiece 701 Housing 702 Liquid crystal panel 703 Backlight 704 Housing 705 Driver IC 706 Terminal 801 Housing 802 Light source 901 Lighting device 902 Television device 1100 Substrate 1101 First electrode 1103 Second electrode 1111 Hole injection layer 1112 Hole transport layer 1113a First light emitting layer 1113b Second light emitting layer 1114a First electron transport layer 1114b Second electron transport layer 1115 Electron injection layer 5000 Portable terminal 5001 Housing 5003 Display unit 5005 Power button 5007 Front camera 5009 Rear camera 5011 External connection terminal 5013 External connection terminal 5015 Icon 6000 Portable terminal 6001 Housing 6003 Housing 6005 Hinge part 6007 Display part 6009 Display part 6011 Power button 6013 Camera 6015 Camera 6017 Text icon 6019 Icon 6021 Keyboard

Claims

1. A hole transport layer and a light emitting layer are disposed between a pair of electrodes, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that converts triplet excitation energy into light emission; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the T1 level of the fourth organic compound is higher than the T1 level of the second organic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

2. A hole transport layer and a light emitting layer are disposed between a pair of electrodes, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that converts triplet excitation energy into light emission; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the T1 level of the fourth organic compound is higher than the T1 level of the second organic compound; the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

3. A hole transport layer and a light emitting layer are disposed between a pair of electrodes, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that converts triplet excitation energy into light emission; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; the T1 level of the fourth organic compound is higher than the T1 level of the second organic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

4. A hole transport layer and a light emitting layer are disposed between a pair of electrodes, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that converts triplet excitation energy into light emission; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; the T1 level of the fourth organic compound is higher than the T1 level of the second organic compound; the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

5. A hole transport layer and a light emitting layer are disposed between a pair of electrodes, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is a phosphorescent compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the T1 level of the fourth organic compound is higher than the T1 level of the second organic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

6. A hole transport layer and a light emitting layer are disposed between a pair of electrodes, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is a phosphorescent compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the T1 level of the fourth organic compound is higher than the T1 level of the second organic compound; the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

7. A hole transport layer and a light emitting layer are disposed between a pair of electrodes, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is a phosphorescent compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; the T1 level of the fourth organic compound is higher than the T1 level of the second organic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

8. A hole transport layer and a light emitting layer are disposed between a pair of electrodes, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is a phosphorescent compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; the T1 level of the fourth organic compound is higher than the T1 level of the second organic compound; the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

9. A hole transport layer and a light emitting layer are disposed between a pair of electrodes, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is an iridium complex; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the T1 level of the fourth organic compound is higher than the T1 level of the second organic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

10. A hole transport layer and a light emitting layer are disposed between a pair of electrodes, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is an iridium complex; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the T1 level of the fourth organic compound is higher than the T1 level of the second organic compound; the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

11. A hole transport layer and a light emitting layer are disposed between a pair of electrodes, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is an iridium complex; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; the T1 level of the fourth organic compound is higher than the T1 level of the second organic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

12. A hole transport layer and a light emitting layer are disposed between a pair of electrodes, the hole transport layer is in contact with the light emitting layer, the light-emitting layer includes a first organic compound, a second organic compound, and a third organic compound that is an iridium complex; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound; the hole transport layer comprises a fourth organic compound having a HOMO level higher than a HOMO level of the second organic compound; the fourth organic compound is at least one of a π-excessive heteroaromatic compound and an aromatic amine compound; the T1 level of the fourth organic compound is higher than the T1 level of the second organic compound; the T1 level of the first organic compound is higher than the T1 level of the third organic compound; the T1 level of the second organic compound is higher than the T1 level of the third organic compound; A light-emitting device, wherein the difference between the energy value of the peak of the emission spectrum of the exciplex and the energy value of the peak of the absorption band located on the lowest energy side of the absorption spectrum of the third organic compound is within 0.2 eV.

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