Light-emitting element, light-emitting device, electronic equipment and illuminating device

Abstract

To provide a light-emitting element with a high external quantum efficiency, and to provide a light-emitting element with a long lifetime.SOLUTION: A light-emitting element has a light-emitting layer between a pair of electrodes. The light-emitting layer at least has a phosphorescent compound, a first organic compound (a host material) with an electron transport property, and a second organic compound (an assist material) with a hole-transport property. The light-emitting layer has a lamination structure of a first light-emitting layer and a second light-emitting layer. The first light-emitting layer contains the second organic compound more than the second light-emitting layer. In addition, in the light-emitting layer (the first light-emitting layer and the second light-emitting layer), the first organic compound and the second organic compound make a combination forming an excited complex.SELECTED DRAWING: None

Description

[Technical field]

[0001] One embodiment of the present invention is a semiconductor device comprising: a semiconductor device including a pair of electrodes and an organic compound that emits light when an electric field is applied thereto; A light-emitting device having such a light-emitting element, an electronic device, and a lighting device are also provided. Regarding the lighting device. [Background technology]

[0002] The organic compound used as the light emitter has characteristics such as being thin and lightweight, having high-speed response, and being driven by low DC voltage. The light-emitting element used is expected to be applied to next-generation flat panel displays. In addition, a display device in which light-emitting elements are arranged in a matrix has a higher viewing angle than a conventional liquid crystal display device. It is believed that its advantages lie in its wide viewing angle and excellent visibility.

[0003] The light-emitting mechanism of a light-emitting element is to sandwich an EL layer containing a light-emitting body between a pair of electrodes and apply a voltage. As a result, electrons injected from the cathode and holes injected from the anode are emitted at the EL layer's light-emitting center. recombines to form molecular excitons, which then lose energy as they relax to the ground state. It is said that the excited state is singlet excited and triplet excited, and the emission occurs when is believed to be possible via either excited state.

[0004] Regarding such light-emitting devices, in order to improve the device characteristics, improvements in the device structure and materials have been made. Development and the like is being actively carried out (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-182699 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the light extraction efficiency of current light-emitting devices is said to be around 20% to 30%. Even when the absorption of light by the reflective electrode and transparent electrode is taken into consideration, the light-emitting element using the phosphorescent compound The limit of the external quantum efficiency of electrons is thought to be around 25%.

[0007] In view of this, one embodiment of the present invention provides a light-emitting element with high external quantum efficiency. One aspect of the present invention provides a light-emitting element with a long lifetime. [Means for solving the problem]

[0008] One embodiment of the present invention has a light-emitting layer between a pair of electrodes. The light-emitting layer contains a phosphorescent compound, an electron transport A first organic compound (host material) having a hole transporting property and a second organic compound having a hole transporting property. The light-emitting layer has at least one of a first light-emitting layer and a second light-emitting layer. It has a laminated structure, and the first light-emitting layer contains a larger amount of the second organic compound than the second light-emitting layer. The light-emitting element is characterized in that the light-emitting layer (the first light-emitting layer and the second light-emitting layer) The first organic compound and the second organic compound are combined to form an exciplex. It is characterized in that:

[0009] Another embodiment of the present invention is a semiconductor device having a light-emitting layer between an anode and a cathode, The light-emitting layer has a hole transport layer between the cathode and the light-emitting layer, and an electron transport layer between the cathode and the light-emitting layer. a first organic compound having an electron transporting property, and a second organic compound having a hole transporting property. A first light-emitting layer including at least one of a phosphorescent compound and an electrode, the first light-emitting layer being formed in contact with the hole transport layer, A first organic compound having electron transport properties and a second organic compound having hole transport properties are mixed at least once. and a second light-emitting layer formed in contact with the electron transport layer, The organic compound and the second organic compound form an exciplex, and the first light-emitting layer is provided with a light-emitting layer having a larger number of exciplexes than the second light-emitting layer. The light-emitting element is characterized in that it contains a large amount of the second organic compound.

[0010] In each of the above structures, the first organic compound (host material) and the second organic compound (a The emission wavelength of the exciplex formed by the first organic compound (host material) is and the second organic compound (assist material) have a longer wavelength than the emission wavelength (fluorescence wavelength) of the first organic compound (assist material). Since the first organic compound (host material) is present on the long side, it forms an exciplex and The fluorescence spectrum of the first organic compound (assist material) and the fluorescence spectrum of the second organic compound (assist material) are The emission spectrum can be converted to a wavelength region.

[0011] Therefore, the light-emitting element according to one embodiment of the present invention can form an exciplex in the light-emitting layer. Therefore, the wavelength is longer than the emission wavelength (fluorescence wavelength) of each of the first organic compound and the second organic compound. The emission spectrum of the exciplex on the long side and the absorption spectrum of the phosphorescent compound (guest material) Energy transfer can be achieved by utilizing the overlap with the torus, and the energy transfer efficiency is high. As a result, a light-emitting device with high external quantum efficiency can be realized.

[0012] In the above structure, the phosphorescent compound contained in the light-emitting layer is the compound contained in the first light-emitting layer. The material contained in the first light-emitting layer may be the same as or different from the material contained in the second light-emitting layer. In this case, the light emitted from the first light-emitting layer is different from the light emitted from the second light-emitting layer. It is characterized by light having a shorter wavelength than

[0013] In the above-mentioned configuration, the anion of the first organic compound and the cationic group of the second organic compound are It is characterized by the formation of an exciplex from an on.

[0014] In the above-mentioned structure, the phosphorescent compound is an organometallic complex, and the first organic compound is , mainly 10 -6 cm 2 Electron transporting materials having an electron mobility of .beta. / Vs or more, specifically The second organic compound is a π-electron deficient heteroaromatic compound, and the second organic compound is mainly 10 -6 cm 2 / Hole transport materials with hole mobility of Vs or higher, specifically, π-electron-rich heteroaromatic compounds The compound is characterized in that it is an aromatic amine compound.

[0015] Another embodiment of the present invention is not only a light-emitting device having a light-emitting element, but also an electric device having a light-emitting device. The term "light-emitting device" as used herein includes a child device and a lighting device. refers to an image display device, a light-emitting device, or a light source (including a lighting device). A connector, such as FPC (Flexible Printed Circuit) it) or TCP (Tape Carrier Package) is attached A module with a printed wiring board at the end of the TCP, or a light-emitting element with C Module with IC (Integrated Circuit) directly mounted using OG (Chip On Glass) method All modules are considered to be included in the light-emitting device. Effect of the Invention

[0016] Note that the light-emitting element according to one embodiment of the present invention can emit a light emitting diode by forming an exciplex in the light-emitting layer. The wavelength is longer than the emission wavelength (fluorescence wavelength) of each of the first organic compound and the second organic compound. The emission spectrum of the exciplex existing next to the phosphorescent compound (guest material) and the absorption spectrum Since energy transfer can be achieved by utilizing the overlap with the nucleus, the efficiency of energy transfer is improved. Therefore, a light emitting device with high external quantum efficiency can be realized.

[0017] Furthermore, the light-emitting layer in one embodiment of the present invention has a stacked structure of a first light-emitting layer and a second light-emitting layer. The first light-emitting layer and the second light-emitting layer each contain a first organic compound having an electron transport property. a first organic compound (host material) and a second organic compound (assist material) having a hole transporting property, The first light-emitting layer contains a larger amount of the second organic compound (assist material) than the second light-emitting layer. By using this composition, the balance of carriers (both holes and electrons) in the light-emitting layer is improved. In this way, excitons formed in the light-emitting layer can be distributed at the interface between the first light-emitting layer and the second light-emitting layer. This prevents the light-emitting layer from deteriorating due to a local high density of excitons. It is possible. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 illustrates a concept of one embodiment of the present invention. [Diagram 2] FIG. 13 shows calculation results according to one embodiment of the present invention. [Diagram 3] FIG. 13 shows calculation results according to one embodiment of the present invention. [Figure 4] 1A and 1B are diagrams illustrating energy levels of an exciplex applied to one embodiment of the present invention. [Diagram 5] 1A to 1C are diagrams illustrating a structure of a light-emitting element. [Figure 6] 1A to 1C are diagrams illustrating a structure of a light-emitting element. [Figure 7] 1A and 1B are diagrams illustrating a light-emitting device. [Figure 8] 1A and 1B are diagrams illustrating a light-emitting device. [Figure 9] 1A to 1C are diagrams illustrating electronic devices. [Figure 10] 1A to 1C are diagrams illustrating electronic devices. [Figure 11] FIG. [Figure 12] 1A to 1C are diagrams illustrating a structure of a light-emitting element 1. [Figure 13] FIG. 13 shows current density-luminance characteristics of the light-emitting element 1. [Figure 14] FIG. 13 shows voltage-luminance characteristics of the light-emitting element 1. [Figure 15] FIG. 13 shows luminance vs. current efficiency characteristics of the light-emitting element 1. [Figure 16] FIG. 2 shows voltage-current characteristics of the light-emitting element 1. [Figure 17] FIG. 2 shows an emission spectrum of the light-emitting element 1. [Figure 18] FIG. 13 shows the reliability of the light-emitting element 1. [Figure 19] FIG. 13 shows current density-luminance characteristics of the light-emitting element 2. [Figure 20] FIG. 13 shows voltage-luminance characteristics of the light-emitting element 2. [Figure 21] FIG. 13 shows luminance vs. current efficiency characteristics of Light-emitting Element 2. [Figure 22] FIG. 13 shows voltage-current characteristics of the light-emitting element 2. [Diagram 23] FIG. 2 shows an emission spectrum of the light-emitting element 2. [Figure 24] 3A to 3C are diagrams illustrating a structure of a light-emitting element 3. [Diagram 25] FIG. 13 shows current density-luminance characteristics of the light-emitting element 3. [Figure 26] FIG. 13 shows voltage-luminance characteristics of the light-emitting element 3. [Figure 27] FIG. 13 shows luminance vs. current efficiency characteristics of the light-emitting element 3. [Figure 28] FIG. 13 shows voltage-current characteristics of the light-emitting element 3. [Figure 29] FIG. 2 shows an emission spectrum of the light-emitting element 3. [Diagram 30]FIG. 13 shows current density-luminance characteristics of the light-emitting element 4. [Diagram 31] FIG. 13 shows voltage-luminance characteristics of the light-emitting element 4. [Diagram 32] FIG. 13 shows luminance vs. current efficiency characteristics of the light-emitting element 4. [Diagram 33] FIG. 13 shows voltage-current characteristics of the light-emitting element 4. [Diagram 34] FIG. 13 shows an emission spectrum of the light-emitting element 4. [Diagram 35] FIG. 13 shows the reliability of the light-emitting element 4. [Diagram 36] FIG. 13 shows current density-luminance characteristics of the light-emitting element 5. [Figure 37] FIG. 13 shows voltage-luminance characteristics of the light-emitting element 5. [Figure 38] FIG. 13 shows luminance vs. current efficiency characteristics of the light-emitting element 5. [Figure 39] FIG. 13 shows voltage-current characteristics of the light-emitting element 5. [Diagram 40] FIG. 4 shows an emission spectrum of the light-emitting element 5. [Diagram 41] FIG. 13 shows the reliability of the light-emitting element 5. [Diagram 42] FIG. 13 is a graph showing current density-luminance characteristics of the light-emitting element 6. [Diagram 43] FIG. 13 is a graph showing voltage-luminance characteristics of the light-emitting element 6. [Diagram 44] FIG. 13 shows luminance vs. current efficiency characteristics of the light-emitting element 6. [Diagram 45] FIG. 13 is a graph showing voltage-current characteristics of the light-emitting element 6. [Figure 46] FIG. 2 shows an emission spectrum of the light-emitting element 6. [Figure 47] FIG. 13 shows the reliability of the light-emitting element 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the above description, and the embodiments and details thereof are not limited to those described above without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the embodiments described below. It is not to be construed as being limited to the content.

[0020] (The elementary process of light emission in light-emitting elements) First, the general elementary process of light emission in a light-emitting device that uses a phosphorescent compound as a guest material Here, the molecule that provides the excitation energy is the host molecule, and the The molecule that receives the photoinduced energy is called the guest molecule.

[0021] (1) Electrons and holes recombine in the guest molecule, and the guest molecule enters an excited state. (direct recombination process).

[0022] (1-1) When the excited state of the guest molecule is a triplet excited state The guest molecules emit phosphorescence.

[0023] (1-2) When the excited state of the guest molecule is a singlet excited state The guest molecule in the singlet excited state undergoes intersystem crossing to the triplet excited state, emitting phosphorescence.

[0024] In other words, in the direct recombination process (1) above, the intersystem crossing efficiency of the guest molecule and the phosphorus If the photon yield is high, high luminescence efficiency can be obtained. The level is preferably higher than the T1 level of the guest molecule.

[0025] (2) The electrons and holes recombine in the host molecule, and the host molecule enters an excited state. (energy transfer process).

[0026] (2-1) When the excited state of the host molecule is a triplet excited state If the T1 level of the host molecule is higher than that of the guest molecule, the host molecule The excitation energy is transferred to the guest molecule, and the guest molecule enters a triplet excited state. The guest molecule emits phosphorescence. Note that the T1 level of the host molecule is converted to the singlet state of the guest molecule. Energy transfer to the excited energy level (S1 level) causes the host molecule to not emit phosphorescence. Since this is forbidden as long as the electron transport mechanism is active, and is unlikely to be the main energy transfer process, it will be omitted here. As shown in the following formula (2-1), the triplet excited state (3H*) of the host molecule is converted to the triplet excited state (3H*) of the guest molecule. The energy transfer to the triplet excited state (3G*) is important (where 1G is the singlet ground state, 1H represents the singlet ground state of the host molecule).

[0027] 3H*+1G → 1H+3G* (2-1)

[0028] (2-2) When the excited state of the host molecule is a singlet excited state If the S1 level of the host molecule is higher than the S1 and T1 levels of the guest molecule, the host The excitation energy is transferred from the molecule to the guest molecule, and the guest molecule enters the singlet excited state or the triplet excited state. The guest molecule in the triplet excited state emits phosphorescence. The guest molecule in this state undergoes intersystem crossing to a triplet excited state and emits phosphorescence.

[0029] In other words, as shown in the following formula (2-2A), the host molecule is converted from the singlet excited state (1H*) to the guest molecule. Energy is transferred to the singlet excited state (1G*) of the guest molecule, and then intersystem crossing occurs. The process of generating the triplet excited state (3G*) of the molecule and the host as shown in the following formula (2-2B) Direct energy transfer from the singlet excited state (1H*) of a molecule to the triplet excited state (3G*) of a guest molecule. One possible process is the energy transfer.

[0030] 1H*+1G → 1H+1G* →(intersystem crossing) → 1H+3G* (2-2A ) 1H*+1G → 1H+3G* (2-2B)

[0031] If all the energy transfer processes described above in (2) occur efficiently, the triple Both the first and singlet excitation energies are efficiently converted to triplet excited states of guest molecules. Conversely, the host molecule is converted to the guest molecule (3G*), enabling highly efficient emission. Before the excitation energy is transferred to the host molecule, the host molecule itself absorbs the excitation energy through light or a photoelectron. If the energy is released as heat and deactivated, the luminous efficiency decreases.

[0032] Next, we consider the governing factors of the energy transfer process between the host and guest molecules mentioned above. The following two mechanisms have been proposed for the mechanism of intermolecular energy transfer: is.

[0033] The first mechanism, the Förster mechanism (dipole-dipole interaction), is -Transfer does not require direct contact between the molecules, but is driven by dipole vibration between the host and guest molecules. This is the mechanism by which energy transfer occurs through the resonance phenomenon of dipole vibration. The host molecule transfers energy to the guest molecule, the host molecule returns to the ground state, and the guest The molecule becomes excited. Note that the rate constant of the Förster mechanism is k h*→g is shown in formula (1). vinegar.

[0034]

number

[0035] In formula (1), ν represents the frequency, and f' h(ν) is the normalized The emission spectrum (or the fluorescence spectrum when discussing energy transfer from a singlet excited state) , and phosphorescence spectrum when discussing energy transfer from triplet excited states), and ε g ( ν) represents the molar extinction coefficient of the guest molecule, N represents Avogadro's number, and n represents the refractive index of the medium. represents the refractive index, R represents the intermolecular distance between the host molecule and the guest molecule, and τ represents the excitation represents the lifetime of the state (fluorescence lifetime or phosphorescence lifetime), c represents the speed of light, and φ represents the luminescence quantum yield ( When discussing energy transfer from a singlet excited state, the fluorescence quantum yield is used. When discussing energy transfer from a triplet excited state, the fluorescence quantum yield is used. When discussing energy transfer, it stands for phosphorescence quantum yield, and K 2 is the host molecule and the guest molecule is a coefficient (0 to 4) that represents the orientation of the transition dipole moment of the is K 2 =2 / 3.

[0036] Next, in the second mechanism, the Dexter mechanism (electron exchange interaction), the host molecule and the gate When the host molecule approaches the effective contact distance where orbital overlap occurs, it interacts with the electron of the excited host molecule. Energy transfer occurs through the exchange of electrons in the ground state of the guest molecule. The rate constant of the mechanism, k h*→g is shown in formula (2).

[0037]

number

[0038] In formula (2), h is the Planck constant, and K' is a constant with the dimension of energy. where ν is the frequency and f' is the h (ν) is the normalized emission spectrum of the host molecule Toll (fluorescence spectrum when discussing energy transfer from singlet excited states, triplet excited When discussing energy transfer from the ε' state, it represents the phosphorescence spectrum. g (ν) is a represents the normalized absorption spectrum of the host molecule, L represents the effective molecular radius, and R represents the This represents the intermolecular distance between the host molecule and the guest molecule.

[0039] Here, the efficiency of energy transfer from the host molecule to the guest molecule Φ ET is expressed as formula (3). It is believed that r is the emission process of the host molecule (energy from the singlet excited state). (fluorescence when discussing energy transfer from triplet excited states, phosphorescence when discussing energy transfer from triplet excited states) represents the rate constant, k n represents the rate constant of non-radiative processes (thermal deactivation and intersystem crossing) of the host molecule. and τ represents the measured lifetime of the excited state of the host molecule.

[0040]

number

[0041] From equation (3), the energy transfer efficiency Φ ET To increase the rate of energy transfer, Degree constant k h*→g By increasing the other competing rate constants k r +k n (=1 / τ) is relatively It turns out that the smaller it is, the better.

[0042] (Energy transfer efficiency of (2-1)) First, let us consider the energy transfer process in (2-1). In this case, Förster Since the Dexter type (formula (1)) is prohibited, only the Dexter type (formula (2)) should be considered. According to 2), the rate constant k h*→gTo increase the emission spectrum of the host molecule (triple Since we are discussing energy transfer from the first excited state, the phosphorescence spectrum and the absorption of guest molecules are Spectrum overlap (absorption corresponding to direct transition from singlet ground state to triplet excited state) It can be seen that a larger ratio is better.

[0043] In one embodiment of the present invention, a phosphorescent compound is used as a guest material. In the spectrum, absorption corresponds to a direct transition from the singlet ground state to the triplet excited state. In some cases, the absorption band that appears at the longest wavelengths is observed. In the case of zinc complexes, the longest wavelength absorption band is a broad absorption band around 500 to 600 nm. (Of course, depending on the emission wavelength, it may appear on the shorter or longer wavelength side.) This absorption band is mainly due to triplet MLCT (Metal to Lithium Transition). However, there are three absorption bands in this band. The absorption due to the doublet π-π* transition and the singlet MLCT transition is also included. It is considered that a broad absorption band is formed on the longest wavelength side of the absorption spectrum. If this is the case, the difference between the lowest singlet excited state and the lowest triplet excited state is small, and the absorption due to these It is thought that these overlap to form a broad absorption band at the longest wavelength side of the absorption spectrum. Therefore, when using an organometallic complex (especially an iridium complex) as a guest material, The broad absorption band on the longest wavelength side and the phosphorescence spectrum of the host material The rate constant k h*→g This increases the energy transfer efficiency. It can be done.

[0044] In addition, since fluorescent compounds are usually used as host materials, the phosphorescence lifetime (τ) is usually on the order of milliseconds or less. Above and very long (k r +k n This is because the triplet excited state is converted to the ground state (singlet ) is a forbidden transition. From equation (3), this means that the energy transfer efficiency Φ ET It works to your advantage.

[0045] Considering the above, the triplet excited state of the host material is converted to the triplet excited state of the guest material. The energy transfer from the phosphorescence state to the phosphorescence state, i.e., the process of formula (2-1), is consistent with the phosphorescence spectrum of the host material. , the absorption spectrum corresponding to the direct transition from the singlet ground state to the triplet excited state of the guest material. Generally speaking, this tends to occur easily if you simply overlap the

[0046] (Energy transfer efficiency of (2-2)) Next, let us consider the energy transfer process in (2-2). The process in equation (2-2A) is Therefore, in order to maximize the luminescence efficiency, In this case, the process of formula (2-2B) is considered to be important. ) is forbidden, so only the Förster type (equation (1)) needs to be considered.

[0047] Eliminating τ from equations (1) and (3) gives the energy transfer efficiency Φ ET is the quantum yield φ( Since we are discussing energy transfer from a singlet excited state, it is better to have a higher fluorescence quantum yield. However, in reality, a more important factor is the emission spectrum of the host molecule. (Fluorescence spectrum, as we are discussing energy transfer from the singlet excited state) and guest molecule The absorption spectrum of (absorption corresponding to the direct transition from the singlet ground state to the triplet excited state) It is also necessary that the overlap of the guest molecules is large (it is also preferable that the molar extinction coefficient of the guest molecule is high). This means that the fluorescence spectrum of the host material and the phosphorescent compound, which is the guest material, are optimally matched. This means that the absorption band that appears on the longer wavelength side overlaps with the absorption band that appears on the longer wavelength side.

[0048] However, it has been very difficult to achieve this in the past because: In order to efficiently carry out both the above-mentioned steps (2-1) and (2-2), From the discussion, it is clear that the phosphorescence spectrum of the host material as well as the fluorescence spectrum of the guest material are the optimal This is because the absorption band must be designed to overlap with the absorption band on the long wavelength side. The host material is selected so that the fluorescence spectrum of the host material is similar to the phosphorescence spectrum. This means that we have to design the following:

[0049] However, in general, the S1 level and the T1 level are significantly different (S1 level > T1 level), so The emission wavelengths of fluorescence and phosphorescence are also significantly different (fluorescence emission wavelength < phosphorescence emission wavelength). For example, in light-emitting devices using phosphorescent compounds, 4, 4'-Di(N-carbazolyl)biphenyl (abbreviation: CBP) has a phosphorescent spectrum around 500 nm. On the other hand, the fluorescence spectrum is around 400 nm, with a gap of 100 nm. Considering this example, the fluorescent spectrum of the host material may differ from the phosphorescent spectrum. It is extremely difficult to design a host material to occupy a similar position. Therefore, the efficiency of energy transfer from the singlet excited state of the host material to the guest material is improved. However, this is important.

[0050] Therefore, one aspect of the present invention is to provide a method for producing a guest material from the singlet excited state of such a host material. This provides a useful method to overcome problems related to the efficiency of energy transfer to The specific aspects of this will be described below.

[0051] (Embodiment 1) In this embodiment, a concept and specific examples of forming a light-emitting element according to one embodiment of the present invention will be described. The structure of a light-emitting element according to one embodiment of the present invention will be described. The EL layer, which includes a light-emitting layer, is sandwiched between the electrodes. The light-emitting layer is a phosphorescent compound called a GUESS. The conductive layer is formed including a conductive material, a first organic compound, and a second organic compound.

[0052] First, the structure of a light-emitting element, which is an example of the present invention, will be described with reference to FIG.

[0053] The device structure shown in FIG. 1A includes a light-emitting layer 10 between a pair of electrodes (anode 101 and cathode 102). The EL layer 103 including the anode 101 is sandwiched between the anode 101 and the EL layer 103. ) injection layer 104, hole transport layer 105, light emitting layer 106 (106a, 106b), It has a structure in which an electron transport layer 107, an electron injection layer 108, and the like are laminated in this order.

[0054] In addition, the light-emitting layer 106 according to one embodiment of the present invention is formed of a guest material as shown in FIG. The organic compound includes a phosphorescent compound 109, a first organic compound 110, and a second organic compound 111. The first organic compound 110 is mainly composed of 10 -6 cm 2 / Vs or higher The second organic compound 111 is mainly composed of an electron transporting material having a high molecular weight. 0 -6 cm 2Use of a hole transport material having a hole mobility of / Vs or more. In this specification, the first organic compound 110 is referred to as a host material, and the second organic Compound 111 is referred to as the assist material.

[0055] In the above structure, the first organic compound (host material) 110 and the second organic compound The triplet excitation energy level (T1 level) of each of the assist materials 111 is phosphorus. It is preferable that the T1 level is higher than that of the photoactive compound (guest material) 109. The T1 level of the phosphorescent compound 109 is higher than the T1 level of the phosphorescent compound 109. The triplet excitation energy of the phosphorescent compound 109, which contributes to the emission, is lower than that of the first organic compound. The compound 110 (or the second organic compound 111) is quenched, and the luminous efficiency is reduced. This is because it will lead to a decline.

[0056] In addition, the light-emitting layer 106 in one embodiment of the present invention includes a second organic The structure is characterized by a laminated structure of light-emitting layers with different ratios of compound (assist material) 111. Specifically, as shown in FIG. 1A, the light-emitting layer 106 is a first light-emitting layer 106a. The first light-emitting layer 106a has a laminated structure with the second light-emitting layer 106b. The ratio of the compound (assist material) 111 contained in the second light-emitting layer 106b is It is characterized in that the proportion of the organic compound (assist material) 111 contained is higher than that of the organic compound (assist material) 111 contained.

[0057] Furthermore, the first light-emitting layer 106a and the second light-emitting layer 106b constituting the light-emitting layer 106 For each, a first organic compound (host material) 110 and a second organic compound (a Regarding the proportion of cyst material (111), either may be more, and in the present invention, This case will also be included.

[0058] In the first light-emitting layer 106a having the above structure, the first If the ratio of the organic compound (assist material) 111 in the second light-emitting layer 10 is low, the light-emitting region becomes smaller than that of the first light-emitting layer 10. On the other hand, the first light-emitting layer 106a is biased toward the anode side (the hole transport layer 105 side) of the first light-emitting layer 106a. The amount of the second organic compound (assist material) 111 in both the second light-emitting layers 106b increases. If the thickness is too small, carriers (both holes and electrons) will easily pass through the light-emitting layer 106. However, the recombination efficiency is reduced in accordance with the structure of one embodiment of the present invention described with reference to FIG. By this, the hole transport property of the first light emitting layer 106a is improved to that of the second light emitting layer 106b. The electron transport property is relatively high compared to the first light-emitting layer 10, and the electron transport property is the opposite. The light emitting layer 106 is not biased toward the interface between the first light emitting layer 106a and the second light emitting layer 106b, and is not deflected from the inside of the light emitting layer 106. As a result, the excitons in the light-emitting layer 106 are distributed without being desorbed. This can prevent deterioration of the light-emitting layer 106 due to an increase in the density of excitons. In addition, since the penetration of carriers from the light emitting layer 106 can be prevented, the light emitting efficiency can be improved. can be kept high.

[0059] Here, in both the first light-emitting layer 106a and the second light-emitting layer 106b, The first organic compound (host material) 110 and the second organic compound (assist material) 111 are This is a combination that forms an excited complex (also called an exciplex). The emission wavelength of the formed exciplex is the same as that of the first organic compound (phosphazene). The emission wavelengths (fluorescence) of the first organic compound (assist material) 110 and the second organic compound (assist material) 111 are Since the first organic compound (host material) 110 exists on the longer wavelength side compared to the first organic compound (host material) 110 The fluorescence spectrum of the second organic compound (assist material) 111 is It is possible to convert the emission spectrum to one located on the long wavelength side.

[0060] This is because, as shown in FIG. 1B, the first organic compound 110 (or the second organic compound 111) is in the longest wavelength region of the phosphorescent compound (guest material) 109. The absorption band of the phosphorescent compound (guest material) 109 is located on the shorter wavelength side compared to that of the Even if there is no overlap with the absorption band located on the long wavelength side, by forming an exciplex, This means that the overlap can be increased. The efficiency of energy transfer can be improved.

[0061] Furthermore, the difference between the singlet and triplet excitation energies of exciplexes is extremely small. In other words, the emission spectrum from the singlet state of the exciplex and that from the triplet state are The emission spectra of these are very close to each other. The emission spectrum of a compound (generally the emission spectrum from the singlet state of an exciplex) is called phosphorescence. When designed to overlap the absorption band located at the longest wavelength side of the compound, the triplet state of the exciplex The emission spectrum from the ionized state (which is not observed at room temperature, and is often not observed at low temperatures) is also This overlaps with the absorption band located at the longest wavelength side of the phosphorescent compound. In other words, singlet excitation Not only the energy transfer from the triplet excited state ((2-2)), but also the energy transfer from the triplet excited state The efficiency of the transfer ((2-1)) is also increased, resulting in efficient emission of both singlet and triplet states. can be converted.

[0062] Therefore, in the following, we will discuss whether exciplexes actually have such properties. The molecular orbital calculation was used to verify this. In general, the combination of heteroaromatic compounds and aromatic amines is the lowest unoccupied molecular orbital (LUMO) of aromatic amines. The LUMO levels of heteroaromatic compounds are deeper than the Molecular Orbital levels. Position (ease of electron transfer) and the highest occupied molecular orbital (HOMO) of heteroaromatic compounds The aromatic level is shallower than the est occupied molecular orbital level. Due to the influence of the HOMO level of aromatic amines (the tendency for holes to enter), an exciplex is formed. Therefore, a complex compound is used as a model of the first organic compound 110 in one embodiment of the present invention. Dibenzo[f,h]quinoxaline (abbreviation), a typical skeleton that constitutes the LUMO of aromatic compounds The aromatic compound 111 was modeled after the second organic compound 111 in one embodiment of the present invention. Triphenylamine (TPA), a typical skeleton that constitutes the HOMO of aromatic amines, These were used and combined for calculation.

[0063] First, the lowest excited singlet state (S1) of one DBq (abbreviation) molecule and one TPA (abbreviation) molecule The optimal molecular structure and excitation energy in the lowest excited triplet state (T1) are calculated using the time-dependent density The calculations were performed using the TD-DFT functional method. In addition, DBq (abbreviation) and TPA (abbreviation) The excitation energies of the dimer of

[0064] The total energy of DFT (density functional theory) is the potential energy, the interelectronic electrostatic energy, energy, the kinetic energy of the electrons, and the exchange-correlation energy, which includes all the complex interactions between electrons. In DFT, the exchange-correlation interaction is expressed as a one-electron potential represented by the electron density. The calculation is fast and highly accurate because it is approximated by a functional of a function. Here, we use the mixed functional B3LYP to estimate the parameters related to the exchange and correlation energies. The weight of the meter was specified.

[0065] In addition, the basis functions are 6-311 (three contraction functions are used for each valence orbital). The triple split valence basis set was applied to all atoms. .

[0066] With the above-mentioned basis functions, for example, in the case of a hydrogen atom, the orbitals 1s to 3s are taken into account, In addition, in the case of a carbon atom, the orbitals 1s to 4s and 2p to 4p are taken into consideration. In order to improve the accuracy of the calculation, the polarization basis set is p function for hydrogen atoms and d function for other atoms. Added function.

[0067] The quantum chemical calculation program used was Gaussian 09. The experiment was carried out using a high-performance computer (SGI, Altix 4700). .

[0068] First, one molecule of DBq (abbreviation), one molecule of TPA (abbreviation), and the combination of DBq (abbreviation) and TPA ( The HOMO and LUMO levels of the dimer of The UMO levels are shown in FIG. 2, and the HOMO and LUMO distributions are shown in FIG.

[0069] Figure 3(A1) shows the LUMO distribution of one molecule of DBq (abbreviation), and Figure 3(A2) shows the LUMO distribution of D The distribution of the HOMO of one molecule of Bq (abbreviation) is shown in Figure 3 (B1), and that of one molecule of TPA (abbreviation) is shown in Figure 3 (B2). Figure 3(B2) shows the distribution of the LUMO of one molecule of TPA (abbreviation). ,Figure 3(C1) shows the LUMO distribution of the dimers of DBq (abbreviation) and TPA (abbreviation). FIG. 3(C2) shows the distribution of HOMOs of the dimers of DBq (abbreviation) and TPA (abbreviation).

[0070] As shown in Figure 2, the dimer of DBq (abbreviation) and TPA (abbreviation) is The LUMO level of DBq (abbreviation) is deeper (lower) than the UMO level (-1.99 eV), The HOMO level of TPA (abbreviation) is shallower (higher) than that of DBq (-5.21 It is suggested that the influence of the ion beam (eV) causes the formation of an exciplex of DBq (abbreviation) and TPA (abbreviation). As can be seen in Figure 3, the LUM of the dimer of DBq (abbreviation) and TPA (abbreviation) O is distributed on the DBq (abbreviation) side, and HOMO is distributed on the TPA (abbreviation) side.

[0071] Next, the optimal molecular structure of DBq (abbreviation) at the S1 and T1 levels was obtained. Here, the excitation energies of the S1 and T1 levels are expressed as DBq (abbreviation ) corresponds to the wavelength of fluorescence and phosphorescence emitted by a single molecule. DBq (abbreviation) corresponds to the S1 standard of a single molecule. The excitation energy was 3.294 eV and the fluorescence wavelength was 376.4 nm. In addition, the excitation energy of the T1 level of one DBq molecule is 2.460 eV, The light wavelength was 504.1 nm.

[0072] In addition, the optimal molecular structure of one TPA molecule at the S1 and T1 levels was obtained. The excitation energies of the S1 and T1 levels are shown in the table below. ) corresponds to the fluorescence and phosphorescence wavelengths emitted by a single molecule of TPA (abbreviation) The excitation energy was 3.508 eV and the fluorescence wavelength was 353.4 nm. The excitation energy of the T1 level of one TPA molecule is 2.610 eV, and that of phosphorus is The light wavelength was 474.7 nm.

[0073] Furthermore, the optimal S1 and T1 levels of the dimers of DBq (abbreviation) and TPA (abbreviation) were The excitation energies obtained from the molecular structure are shown below. The excitation energies of the S1 and T1 levels are as follows: These correspond to the fluorescence and phosphorescence wavelengths emitted by DBq (abbreviation) and TPA (abbreviation) dimers, respectively. The excitation energy of the S1 level of the dimer of DBq (abbreviation) and TPA (abbreviation) is 2.036 The fluorescence wavelength was 609.1 nm. The excitation energy of the T1 level of the dimer (nominal) is 2.030 eV, and the phosphorescence wavelength is 61 The result was 0.0 nm.

[0074] From the above, in both DBq (abbreviation) single molecule and TPA (abbreviation) single molecule, It can be seen that the phosphorescence wavelength is shifted to the long wavelength by nearly 100 nm. This is because This shows a similar trend to (abbreviation) (actual measured value), and supports the validity of the calculation.

[0075] On the other hand, the fluorescence wavelength of the dimer of DBq (abbreviation) and TPA (abbreviation) is the same as that of one DBq (abbreviation) molecule. It can be seen that the fluorescence wavelength is on the longer wavelength side compared to the fluorescence wavelength of a single molecule of DB The difference between the fluorescence and phosphorescence wavelengths of the dimers of q (abbreviation) and TPA (abbreviation) is only 0.9 nm. It can be seen that the wavelengths are almost the same.

[0076] 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.

[0077] In this manner, the light-emitting element of one embodiment of the present invention has an exciplex formed in the light-emitting layer. By utilizing the overlap between the emission spectrum and the absorption spectrum of the phosphorescent compound (guest material), Since the energy transfer occurs, the energy transfer efficiency is high. Therefore, the external quantum efficiency is high. Therefore, a light emitting element with a high light emitting property can be realized.

[0078] In addition, since exciplexes exist only in excited states, there is no ground state that can absorb energy. Therefore, the singlet and triplet excited states of the phosphorescent compound (guest material) are The phosphorescent compound (guest material) 109 emits light by energy transfer from the 109 state to the exciplex. In principle, the phenomenon of the luminescence efficiency being reduced before the photoactivation is completed is not considered to occur. This is also one of the reasons why the external quantum efficiency can be increased.

[0079] The above-mentioned exciplexes are formed by interactions between different molecules in an excited state. In addition, exciplexes are classified into materials with relatively deep LUMO levels and materials with shallow HOMO levels. It is generally known that it is easy to form between materials.

[0080] The emission wavelength of an exciplex depends on the energy difference between the HOMO and LUMO levels. Generally speaking, the larger the energy difference, the shorter the emission wavelength becomes, and the smaller the energy difference, the shorter the emission wavelength becomes. The emission wavelength becomes longer.

[0081] Therefore, the first organic compound (host material) 110 and the second organic compound The HOMO level and the LUMO level of the compound (assist material) 111 are different from each other. In other words, the HOMO level of the first organic compound 110 is smaller than the HOMO level of the second organic compound 111. level < LUMO level of the first organic compound 110 < LUMO level of the second organic compound 111 The energy levels differ in this order (see Figure 4).

[0082] When these two organic compounds form an exciplex, the LUMO of the exciplex is The HOMO level is due to the first organic compound (host material) 110, and the HOMO level is due to the second organic This is due to the compound (assist material) 111 (see Figure 4). The energy difference is the energy difference between the first organic compound (host material) 110 and the second organic compound (host material) 111. The energy difference between the first organic compound and the second organic compound (assist material) 111 is smaller than that between the first organic compound and the second organic compound (assist material) 111. The emission wavelengths of the (host material) 110 and the second organic compound (assist material) 111 The emission wavelength of the exciplex is longer than that of the

[0083] In one embodiment of the present invention, the formation process of an exciplex can be considered to be the following two processes. do.

[0084] The first formation process is a process in which a first organic compound (host material) and a second organic compound (assist The material (catalyst material) changes from a state with carriers (cation or anion) to a state in which an exciplex is formed. It is a process of development.

[0085] In general, when an electron and a hole recombine in a host material, an excited state of the host material is formed. The excitation energy is transferred from the host material to the guest material, and the guest material reaches an excited state and emits light. However, before the excitation energy is transferred from the host material to the guest material, the host material itself emits light. By emitting light or converting the excitation energy into thermal energy, a part of the excitation energy is deactivated. In particular, when the host material is in a singlet excited state, as described in (2-2), Such deactivation of excitation energy is a factor in shortening the life of light-emitting elements. This is one of the factors leading to the decline.

[0086] However, in one aspect of the present invention, a first organic compound (host material) and a second organic The compound (assist material) changes from a carrier-containing state (cation or anion) to an excited complex. In order to form a structure, the formation of singlet excitons in the first organic compound (host material) is suppressed. In other words, the process of directly forming an exciplex can be achieved without forming a singlet exciton. This can also suppress the deactivation of the singlet excitation energy. Therefore, a light emitting element with a long life can be realized.

[0087] For example, the first organic compound 110 captures electrons (carriers) even in the electron transporting material. It is a compound with electron trapping properties (deep LUMO level) that is easy to trap electrons. Among hole-transporting materials, the organic compound 111 has the property of easily capturing holes (carriers). In the case of a hole-trapping compound having a shallow HOMO level, the first organic conversion The anion of the compound and the cation of the second organic compound directly form an exciplex. The exciplex formed in this process is called an electroplex. In this way, the first organic compound (host material) Suppresses the generation of singlet excited states and converts the electroplex into a phosphorescent compound (guest material) By performing energy transfer to the light emitting element, 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 (host material) is also suppressed, and the direct excitation is suppressed. Since an exciplex is formed, energy is transferred from the exciplex to the phosphorescent compound (guest material). It is thought that this is the case.

[0088] The second formation process is a process in which a first organic compound (host material) and a second organic compound (assist After one of the materials (the photocatalyst material) forms a singlet exciton, it interacts with the other material in the ground state to form an exciplex. Unlike electroplexing, in this case, the first organic A singlet excited state is generated in the compound (host material) or the second organic compound (assist material). However, this is quickly converted to an exciplex, so the singlet excitation energy is still Therefore, the deactivation of the first organic compound (host material) or the second organic compound (host material) can be suppressed. It is possible to suppress the organic compound (assist material) from losing excitation energy. In this case, the triplet excited state of the host material is also rapidly converted to an exciplex. It is believed that energy is transferred from the exciplex to the phosphorescent compound (guest material).

[0089] The first organic compound (host material) is an electron trapping compound, while the second The organic compounds (assist materials) in the above list are hole-trapping compounds, and the HO When the difference between the MO levels and the LUMO levels is large (specifically, the difference is 0.3 eV or more), The electrons selectively enter the first organic compound (host material), and the holes selectively enter the second organic compound (host material). In this case, the process in which an exciplex is formed via a singlet exciton is called the assist material. It is believed that the process of electroplex formation takes precedence over the process of cytoplasmic ionization.

[0090] In addition, the emission spectrum of the exciplex and the absorption spectrum of the phosphorescent compound (guest material) were thoroughly In order to overlap the emission spectrum with the absorption spectrum, the energy of the peak must be It is preferable that the difference between the energy value of the absorption band peak on the low energy side is within 0.3 eV. It is more preferable that the difference is within 0.2 eV, and most preferable that the difference is within 0.1 eV. .

[0091] In the light-emitting element according to one embodiment of the present invention, the excitation energy of the exciplex is converted into phosphorescence. The energy transfer to the guest compound was sufficient, and practically no emission from the exciplex was observed. Therefore, it is preferable to transfer energy to the phosphorescent compound (guest material) via the exciplex. It is preferable that the energy is transferred to the phosphorescent compound (guest material) so that the phosphorescent compound emits phosphorescence. The phosphorescent compound (guest material) is preferably an organometallic complex.

[0092] In the light-emitting element according to one embodiment of the present invention, the first organic compound (host material) contains phosphorus. When a photoactive compound is used, the first organic compound (host material) itself becomes more likely to emit light, resulting in phosphorescence. In this case, the energy is hardly transferred to the first organic compound (guest material). It would be good if the material could emit light efficiently, but the host material has a problem of concentration quenching, so It is difficult to achieve high efficiency. Therefore, At least one of the organic compounds (assist materials) is a fluorescent compound (i.e., a compound in the singlet excited state). Therefore, it is effective when the compound is a compound that is prone to luminescence or thermal deactivation from the first state. At least one of the first organic compound (host material) and the second organic compound (assist material) is preferably a fluorescent compound.

[0093] Therefore, the first organic compound (host material) is a fluorescent compound and has an exciplex. It is preferable that the body be used as a medium for energy transfer.

[0094] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. It is possible to do so.

[0095] (Embodiment 2) In this embodiment, an example of a light-emitting element which is one embodiment of the present invention will be described with reference to FIG. do.

[0096] The light-emitting element shown in this embodiment has a pair of electrodes (first electrode (anode) 2) as shown in FIG. An EL layer 203 including a light-emitting layer 206 is sandwiched between a first electrode (cathode) 201 and a second electrode (cathode) 202. The EL layer 203 has a laminated structure of a first light-emitting layer 206a and a second light-emitting layer 206b. In addition to the light-emitting layer 206, a hole injection layer 204, a hole transport layer 205, and a hole transport layer 206 are formed. The electron transport layer 205, the electron transport layer 207, the electron injection layer 208, and the like are included.

[0097] In addition, the light-emitting layer 206 (the first light-emitting layer 206a and the second light-emitting layer 2 06b) contains a phosphorescent compound 209 as a guest material and a first organic compound 208 as a host material. The first organic compound 210 and the second organic compound 211, which is an assist material, are included in the photoresist. In this embodiment, the first organic compound 210 is more likely to be a fluorine-containing compound than the second organic compound 211. is contained in a large proportion in the light emitting layer 206 (in both 206a and 206b).

[0098] The light-emitting layer 206 shown in this embodiment is made up of a first light-emitting layer 206a and a second light-emitting layer 206b. 6b, but the first light-emitting layer 206a contains a second organic compound (acid The proportion of the second organic compound (aluminum material) 211 contained in the second light-emitting layer 206b is The proportion of cyst material (211) is higher than that of the control.

[0099] In the light-emitting layer 206 (the first light-emitting layer 206a and the second light-emitting layer 206b), The phosphorescent compound 209 is mixed with a first organic compound (host material) 210 and a second organic compound (a By dispersing the crystalline silicon in the crystalline silicon material 211, crystallization of the light-emitting layer 206 is suppressed. In addition, concentration quenching caused by a high concentration of the phosphorescent compound 209 can be suppressed. The light emitting efficiency of the light emitting element can be increased.

[0100] In addition, the triplet excited energies of the first organic compound 210 and the second organic compound 211 are The energy level (T1 level) of the phosphorescent compound 209 is preferably higher than the T1 level of the phosphorescent compound 209. The T1 level of the first organic compound 210 (or the second organic compound 211) is a phosphorescent compound. If the T1 level of the guest material is lower than that of the guest material 209, the phosphorescent compound (guest material) that contributes to light emission The triplet excitation energy of the first organic compound 210 (or the second organic compound 211) is converted to 11) will be quenched, resulting in a decrease in luminous efficiency.

[0101] In the light-emitting layer 206 of the present embodiment, carriers (electrons) injected from both electrodes and holes) from the first organic compound 210 and the second organic compound 211. As a result, the first exciplex in the light-emitting layer 206 Fluorescence spectrum of the first organic compound 210 and the second organic compound 211. can be converted to the emission spectrum of the exciplex located at longer wavelengths. Therefore, In order to maximize the energy transfer from the singlet excited state, the emission spectrum of the exciplex is The overlap between the absorption spectrum of the phosphorescent compound (guest material) 209 and that of the fluorophore 209 is large. , a first organic compound 210 and a second organic compound 211 are selected, respectively. In this case, the triplet excited state is also determined by the energy from the exciplex rather than the host material. - It is assumed that movement will occur.

[0102] The phosphorescent compound 209 is preferably an organometallic complex. As the host material 210, an electron transporting material is preferably used. The organic compound (assist material) 211 is a hole transport material. is preferred.

[0103] As the organometallic complex, for example, bis[2-(4',6'-difluorophenyl) Nyl)pyridinato-N,C 2’ ]Iridium(III) tetrakis(1-pyrazolyl)boron FIr6, bis[2-(4',6'-difluorophenyl)pyridinate] -N,C 2’ ]iridium(III) picolinate (abbreviation: FIrpic), bis[2- (3',5'-bistrifluoromethylphenyl)pyridinato-N,C2’ ]iridium (III) Picolinate (abbreviation: Ir(CF3ppy)2(pic)), bis[2-(4 ',6'-Difluorophenyl)pyridinato-N,C 2’ ]Iridium(III) acetyl FIracac, tris(2-phenylpyridinato)iridium Ir(III) (abbreviation: Ir(ppy)3), bis(2-phenylpyridinato)iridium (III) Acetylacetonate (abbreviation: Ir(ppy)2(acac)), bis(benzoyl) Ir(bzq) )2(acac)), bis(2,4-diphenyl-1,3-oxazolato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: Ir(dpo)2(acac)), Bis{2-[4'-(perfluorophenyl)phenyl]pyridinato-N,C 2’}Ili Ir(p-PF-ph)2(acac) ), Bis(2-phenylbenzothiazolato-N,C 2’ ) Iridium(III) acetyl Acetonate (abbreviation: Ir(bt)2(acac)), bis[2-(2'-benzo[4, 5-α]thienyl)pyridinato-N,C 3’ ]Iridium(III) acetylacetoner Ir(btp)2(acac)), bis(1-phenylisoquinolinato-N, C 2’ ) Iridium(III) acetylacetonate (abbreviation: Ir(piq)2(aca c)), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxa [Fdpq]iridium(III) (abbreviation: Ir(Fdpq)2(acac)), (acetyl Acetonato)bis(2,3,5-triphenylpyrazinate)iridium(III)(abbreviation :Ir(tppr)2(acac)), 2,3,7,8,12,13,17,18-octyl Triethyl-21H,23H-porphyrin platinum(II) (abbreviation: PtOEP), tris( Acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: Tb(a cac)3(Phen)), Tris(1,3-diphenyl-1,3-propanedionato) (Monophenanthroline) europium(III) (abbreviation: Eu(DBM)3(Phen )), tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monof (phenanthroline) europium(III) (abbreviation: Eu(TTA)3(Phen)), etc. Examples include:

[0104] In addition, the electron transport material may be a π-deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound. Aromatic compounds are preferred, for example, 2-[3-(dibenzothiophen-4-yl)phenyl ]Dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'- (Dibenzothiophene-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxa Phosphorus (abbreviation: 2mDBTBPDBq-II), 2-[4-(3,6-diphenyl-9H- Carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzP DBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[ f,h]quinoxaline (abbreviation: 7mDBTPDBq-II) and 6-[3-(dibenzo 6mDibenzo[f,h]quinoxaline (abbreviation: 6mDB quinoxaline or dibenzoquinoxaline derivatives such as TPDBq-II .

[0105] In addition, the hole transport material may be a π-excess heteroaromatic compound (e.g., cation). Preferred are 4-phenylenediamine compounds, such as 4-phenylenediamine compounds, ... Phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-di(1-naphthyl)-4''-(9-phenyl- 9H-Carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 3-[N -(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenyl Nylcarbazole (abbreviation: PCzPCN1), 4,4',4''-tris[N-(1-naphthalene 1'-TNATA), 2, 7-Bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9 ,9'-Bifluorene (abbreviation: DPA2SF), N,N'-bis(9-phenylcarbazo PCA2 B), N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl) Diphenylamine (abbreviation: DPNF), N,N',N''-triphenyl-N,N',N ''-Tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine PCA3B, 2-[N-(9-phenylcarbazol-3-yl)-N-phenylcarbazol-3-yl]- phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), 2-[N-(4 -diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPASF), N,N'-bis[4-(carbazol-9-yl)phenyl]- N,N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA 2F), 4,4'-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (abbreviation: TPD), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenyl] phenylamino]biphenyl (abbreviation: DPAB), N-(9,9-dimethyl-9H-fluoro N-(9,9-phenyl-2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(9,9- Dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenyl Nylamine (abbreviation: DFLADFL), 3-[N-(9-phenylcarbazole-3-yl) PCzPCA1, 3 -[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbamoyl PCzDPA1, 3,6-bis[N-(4-diphenylaminophenyl PCzDPA2, 4 ,4'-Bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino] phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), 3,6-bis[N- (4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbamoyl PCzTPN2, 3,6-bis[N-(9-phenylcarbazole- 3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2 ) are mentioned.

[0106] However, the phosphorescent compound 209, the first organic compound (host material) 210, and The materials that can be used for the second organic compound (assist material) 211 are as follows: The combination is not limited to the above, but can form an exciplex. The peak of the emission spectrum of the exciplex overlaps with the absorption spectrum of the phosphorescent compound 209. The peak of the absorption spectrum of the phosphorescent compound 209 may be longer than the wavelength of the peak of the absorption spectrum of the phosphorescent compound 209. .

[0107] In addition, the first organic compound 210 is made of an electron transporting material, and the second organic compound 211 is made of a positive When using hole transport materials, the carrier balance is controlled by the mixture ratio. Specifically, the first organic compound 210:the second organic compound 211=1:9 A range of up to 9:1 is preferred.

[0108] A specific example of manufacturing the light-emitting element described in this embodiment mode will be described below.

[0109] The first electrode (anode) 201 and the second electrode (cathode) 202 are made of a metal, an alloy, an electrically conductive material, or Conductive compounds and mixtures thereof can be used. Indium-tin oxide (ITO), silicon or silicon oxide Indium oxide-tin oxide and indium oxide-zinc oxide (Indium Zi nc Oxide), indium oxide containing tungsten oxide and zinc oxide, gold (A u), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo) Mo, Fe, Co, Cu, Pd, Ti In addition to Ti, elements in the first or second group of the periodic table, namely lithium (L i) and cesium (Cs), as well as magnesium (Mg), calcium ( Alkaline earth metals such as Ca, Strontium (Sr), and alloys containing these metals (Mg Rare earth metals such as Ag, AlLi), europium (Eu), ytterbium (Yb) and The first electrode (anode) may be a cathode material, an alloy containing the above-mentioned, or graphene. The first electrode (cathode) 201 and the second electrode (cathode) 202 are formed by, for example, sputtering or deposition (vacuum The thin film can be formed by a method such as vapor deposition.

[0110] The hole-injection layer 204 and the hole-transport layer 205 may be formed of a material having a high hole-transporting property, for example. For example, 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation :NPB or α-NPD) and N,N'-bis(3-methylphenyl)-N,N'-diphenyl Phenyl-[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: TD ATA), 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamine N-(spiro-9, 9'-Bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB) Aromatic amine compounds such as 3-[N-(9-phenylcarbazol-3-yl)-N- Phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis [N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenyl Carbazole (abbreviation: PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenyl PCzPC Other examples include 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-ca Carbazole derivatives such as carbazole (abbreviation: CzPA) can be used. The substances mentioned in are mainly -6 cm 2 A material that has a hole mobility of at least / Vs. Any other substance may be used as long as it has a higher hole transporting property than an electron transporting property.

[0111] In addition, poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriflate) phenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenyl phenyl-N'-phenylamino}phenyl)methacrylamide (abbreviation: PTPDMA), poly[N,N'-bis(4-butylphenyl)-N,N'-bi Poly(phenyl)benzidine (abbreviation: Poly-TPD) and other polymer compounds are used. It is also possible.

[0112] In addition, examples of acceptor substances that can be used in the hole injection layer 204 include transition metals, Examples of the oxides include oxides of metals belonging to groups 4 to 8 of the periodic table. Specifically, molybdenum oxide is particularly preferred.

[0113] The light-emitting layer 206 (206a, 206b) is as described above, and contains a phosphorescent compound 209, A first organic compound (host material) 210 and a second organic compound (assist material) 21 It is formed including 1.

[0114] The electron transport layer 207 is a layer containing a substance with a high electron transporting property. Alq3, tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq3) , Bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq2), BAlq, Zn(BOX)2, bis[2-(2-hydroxyphenyl)benzothiazol ] zinc (abbreviation: Zn(BTZ)2) and other metal complexes can be used. 4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazide PBD, 1,3-bis[5-(p-tert-butylphenyl)-1, 3,4-Oxadiazol-2-yl]benzene (abbreviation: OXD-7), 3-(4-te rt-Butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triphenyl Azole (abbreviation: TAZ), 3-(4-tert-butylphenyl)-4-(4-ethyl Phenyl)-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: p-EtT AZ), Bathophenanthroline (abbreviation: BPhen), Bathocuproine (abbreviation: BCP ), 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: B Heteroaromatic compounds such as poly(2,5-pyridine) can also be used. -diyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl )-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), poly[(9,9-di Octylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-di Polymer compounds such as PF-BPy (abbreviation: PF-BPy) can also be used. The solid material is mainly 10 -6 cm 2 / Vs or higher. Any other material may be used as the electron transport layer 207 as long as it has a higher electron transporting property than the hole transporting property. It's fine.

[0115] In addition, the electron transport layer 207 may be a single layer or may be a laminate of two or more layers of the above-mentioned materials. It may also be layered.

[0116] The electron injection layer 208 is a layer containing a substance with high electron injection properties. Lithium fluoride (LiF), Cesium fluoride (CsF), Calcium fluoride (CaF2) , lithium oxide (LiOx), etc., alkaline metals, alkaline earth metals, or the like Also, rare earth compounds such as erbium fluoride (ErF3) can be used. Metal compounds can be used. In addition, the above-mentioned material constituting the electron transport layer 207 can be used. You can also be there.

[0117] Alternatively, the electron injection layer 208 may be formed by mixing an organic compound and an electron donor. Composite materials may also be used. Such composite materials are made by adding electrons to organic compounds by electron donors. Since the organic compound is a fluorine-containing compound, the electron injection and transport properties are excellent. In the case of the electrode, it is preferable that the electrode be made of a material having excellent transport properties of the generated electrons. The material constituting the electron transport layer 207 (metal complex, heteroaromatic compound, etc.) can be used. The electron donor may be any substance that exhibits electron donating properties to organic compounds. Specifically, alkali metals, alkaline earth metals and rare earth metals are preferred, and lithium, cesium, etc. Examples of the elements include aluminum, magnesium, calcium, erbium, and ytterbium. Alkali metal oxides and alkaline earth metal oxides are preferred, and lithium oxide, calcium oxide, Examples of the cations include barium oxide and barium phosphate. In addition, Lewis bases such as magnesium oxide are used. It is also possible to use organic compounds such as tetrathiafulvalene (TTF). It is also possible.

[0118] The hole injection layer 204, the hole transport layer 205, and the light emitting layer 206 (206a, 20 6b), the electron transport layer 207, and the electron injection layer 208 are formed by deposition (including vacuum deposition). ), an ink jet method, a coating method, or the like.

[0119] The light emitted from the light emitting layer 206 of the above-mentioned light emitting device is generated by the first electrode 201 and the second electrode 202. The electric current is taken out through one or both of the electrodes 202. Either or both of the first electrode 201 and the second electrode 202 in the The electrode has the following structure.

[0120] The light-emitting element described in this embodiment has an emission spectrum of an exciplex and an absorption spectrum of a phosphorescent compound. Energy transfer efficiency is improved by utilizing spectral overlap. Therefore, a light emitting device with high external quantum efficiency can be realized.

[0121] Note that the light-emitting element described in this embodiment is one embodiment of the present invention, and in particular, Therefore, by applying the configuration shown in this embodiment, It is possible to manufacture a light-emitting device of a switch type or an active matrix type. are all intended to be included in the present invention.

[0122] In the case of an active matrix type light emitting device, the structure of the TFT is not particularly limited. For example, a staggered or inverted staggered TFT can be used as appropriate. The driver circuit formed on the FT substrate may consist of N-type and P-type TFTs. Alternatively, it may be composed of only one of N-type TFTs or P-type TFTs. Furthermore, there is no particular limitation on the crystallinity of the semiconductor film used in the TFT. An amorphous semiconductor film, a crystalline semiconductor film, an oxide semiconductor film, or the like can be used.

[0123] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. It is possible to do so.

[0124] (Embodiment 3) In this embodiment, as one embodiment of the present invention, a structure having a plurality of EL layers sandwiching a charge generating layer is described. A light emitting device having this structure (hereinafter referred to as a tandem type light emitting device) will be described.

[0125] The light-emitting element shown in this embodiment has a pair of electrodes (first electrode 30) as shown in FIG. A plurality of EL layers (first EL layer 302(1), second EL layer 302(2), and second EL layer 304) are disposed between the first and second electrodes 302(3), 302(4), 302(5), 302(6), 302(7), 302(8), 302(9), 302(10), 302(11), 302(12), 302(13 This is a tandem type light emitting device having an L layer 302(2).

[0126] In this embodiment, the first electrode 301 is an electrode that functions as an anode, and the second The electrode 304 functions as a cathode. The structure of the EL layer 304 may be the same as that of the first embodiment. The first EL layer 302(1) and the second EL layer 302(2) are the same as those in the first embodiment or the second embodiment. The EL layer may have a similar structure to that shown in 2, but either one may have a similar structure. That is, the first EL layer 302(1) and the second EL layer 302(2) have the same structure. The configuration may be the same as that of the first or second embodiment. can be applied.

[0127] In addition, between the multiple EL layers (the first EL layer 302(1) and the second EL layer 302(2)), The charge generating layer (I) 305 is provided on the first electrode. When a voltage is applied between the first electrode 301 and the second electrode 304, electrons are injected into one EL layer and the other In this embodiment, the first electrode 301 has a function of injecting holes into the EL layer. When a voltage is applied so that the potential becomes higher than that of the second electrode 304, the charge generating layer (I) 30 Electrons are injected from the first EL layer 302(1) to the second EL layer 302(2) and holes are injected from the second EL layer 302(3) to the first EL layer 302(1). It is injected.

[0128] From the viewpoint of light extraction efficiency, the charge generating layer (I) 305 is transparent to visible light. Specifically, the transmittance of visible light through the charge generating layer (I) 305 is 40% or more. ) is preferable. In addition, the charge generating layer (I) 305 is preferably a first electrode 301 or a second electrode 302. It works even with conductivities lower than 04.

[0129] The charge generation layer (I) 305 is formed by adding an electron acceptor (acceptor) to an organic compound having high hole transport properties. ) is added, the electron donor (donor) is added to the organic compound with high electron transport properties. Alternatively, both of these structures may be laminated.

[0130] In the case where an electron acceptor is added to an organic compound having a high hole transporting property, Examples of organic compounds with high transportability include NPB, TPD, TDATA, and MTDATA. , 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenyl Aromatic amine compounds such as bisaminobiphenyl (abbreviation: BSPB) can be used. The substances mentioned here are mainly -6 cm 2 / Vs or more. However, if an organic compound has a higher hole transporting property than an electron transporting property, a substance other than the above may be used. That's fine.

[0131] In addition, 7,7,8,8-tetracyano-2,3,5,6-tetracyanophenylacetate can be used as an electron acceptor. Examples include fluoroquinodimethane (abbreviation: F4-TCNQ) and chloranil. Further, transition metal oxides can be used. Specifically, vanadium oxide, niobium oxide, etc. , Tantalum oxide, Chromium oxide, Molybdenum oxide, Tungsten oxide, Manganese oxide, Oxide Rhenium is preferred because of its high electron-accepting property. In particular, molybdenum oxide is stable even in the atmosphere. It is preferable because it is stable, has low hygroscopicity, and is easy to handle.

[0132] On the other hand, in the case where an electron donor is added to an organic compound having high electron transport properties, Examples of organic compounds with high electron transport properties include Alq, Almq3, BeBq2, and B Metal complexes having a quinoline or benzoquinoline skeleton, such as Alq, can be used. In addition, oxazole-based compounds such as Zn(BOX)2 and Zn(BTZ)2, Metal complexes having azole-based ligands can also be used. However, PBD, OXD-7, TAZ, BPhen, BCP, etc. can also be used. The substances mentioned in are mainly -6 cm 2 / Vs or higher. Any organic compound having a higher electron transporting property than a hole transporting property may be used. stomach.

[0133] The electron donor may be an alkali metal, an alkaline earth metal, a rare earth metal, or or metals belonging to Group 13 of the periodic table and their oxides and carbonates. Specifically, lithium (Li), cesium (Cs), magnesium (Mg), Calcium (Ca), Ytterbium (Yb), Indium (In), Lithium oxide, Carbonate It is preferable to use cesium, etc. Also, organic compounds such as tetrathianaphthacene may be used as the electron donor.

[0134] In addition, by forming the charge generating layer (I) 305 using the above-mentioned material, an EL layer is formed. When the layers are stacked, the increase in driving voltage can be suppressed.

[0135] In this embodiment mode, a light-emitting element having two EL layers has been described. As shown in the figure, n (n is 3 or more) EL layers (302(1), 302(2) to 302(3)) are arranged. The same can be applied to a light emitting device in which layers (302(n-1), 302(n)) are stacked. As in the light-emitting element according to the present embodiment, a light-emitting element having a plurality of EL layers between a pair of electrodes In this case, a charge generating layer (I) (305(1), 305(2) to 305(3)) is provided between the EL layers. By arranging the 305(n-2), 305(n-1)), high brightness can be achieved while keeping the current density low. It is possible to emit light in the low current density range. This allows the realization of a long-life element. In the case of lighting applications, the voltage drop due to the resistance of the electrode material can be reduced, allowing a large surface area This enables uniform light emission over a wide area. It also enables low-voltage operation and low-power light-emitting devices. It is possible.

[0136] In addition, by making the emission color of each EL layer different, the light-emitting element as a whole can be For example, in a light-emitting device having two EL layers, the first By making the emission color of the first EL layer and the emission color of the second EL layer complementary to each other, It is also possible to obtain a light-emitting element that emits white light as a whole. In other words, the color that becomes achromatic when it is combined with the color that is complementary is called the color of the substance that emits the color. When the resulting light is mixed, white light can be obtained.

[0137] The same applies to a light-emitting element having three EL layers. For example, The emission color of the first EL layer is red, the emission color of the second EL layer is green, and the emission color of the third EL layer is blue. In this case, the light emitting element as a whole can emit white light.

[0138] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. There can be.

[0139] (Embodiment 4) In this embodiment, a light-emitting device which is one embodiment of the present invention will be described.

[0140] The light-emitting device described in this embodiment mode is a micro-optical resonance device that utilizes the optical resonance effect between a pair of electrodes. As shown in Figure 7, the reflector has a microcavity structure and a pair of electrodes (reflection electrodes 4 The light emitting device has a structure having at least an EL layer 405 between the light emitting device 401 and the semi-transmissive / semi-reflective electrode 402. The EL layer 405 includes at least the light-emitting layer 4 which is a light-emitting region. 04 (404R, 404G, 404B), and other layers include a hole injection layer, a hole transport layer, an electron A transport layer, an electron injection layer, a charge generation layer (E), etc. may be included.

[0141] In this embodiment, a light emitting element having a different structure (first light emitting element (R) 4) is used as shown in FIG. 10R, a second light-emitting element (G) 410G, and a third light-emitting element (B) 410B. A light emitting device to be used will be described.

[0142] The first light-emitting element (R) 410R includes a first transparent conductive layer 403a on a reflective electrode 401, The first light-emitting layer (B) 404B, the second light-emitting layer (G) 404G, and the third light-emitting layer (R) 404 The EL layer 405 partially containing R and the semi-transmissive / semi-reflective electrode 402 are laminated in this order. In addition, the second light emitting element (G) 410G has a second transparent conductive layer 4 on the reflective electrode 401. 03b, an EL layer 405, and a semi-transmissive / semi-reflective electrode 402 are laminated in this order. The third light emitting element (B) 410B has an EL layer 405 on a reflective electrode 401 and a semi-transmissive A semi-reflective electrode 402 is laminated in this order.

[0143] In addition, the light emitting elements (first light emitting element (R) 410R, second light emitting element (G) 410G In the third light-emitting element (B) 410B), a reflective electrode 401, an EL layer 405, a semi-transmissive layer The semi-reflective electrode 402 is shared. In the first light-emitting layer (B) 404B, Light with a peak in the wavelength region below 480 nm (λ B ) emits light, and the second light-emitting layer (G) In 404G, light with a peak in the wavelength range of 500 nm to 550 nm (λ G ) is issued The third light-emitting layer (R) 404R emits light in the wavelength range of 600 nm to 760 nm. Peak light (λ R ) emits light. This causes any of the light-emitting elements (the first light-emitting element (R) 410R, the second light-emitting element (G) 410G, and the third light-emitting element (B) 410B) , the first light-emitting layer (B) 404B, the second light-emitting layer (G) 404G, and the third light-emitting layer (R ) The light emitted from 404R is superimposed, that is, it emits broad light across the visible light range. From the above, the wavelength is λ B <λ G <λ R It is a relationship Let us assume that.

[0144] Each of the light-emitting elements shown in this embodiment has a reflective electrode 401 and a semi-transmissive / semi-reflective electrode 40 2 and an EL layer 405 is sandwiched between the EL layer 405 and the The light emitted from the layer in all directions functions as a micro-optical resonator (microcavity) The reflection electrode 401 and the semi-transmissive and semi-reflective electrode 402 are resonated. The electrode 401 is made of a conductive material having reflectivity, and the reflectance of visible light to the film is The rate is 40% to 100%, preferably 70% to 100%, and the resistivity is 1×10 -2 The semi-transmissive / semi-reflective electrode 402 has a reflectivity of Ωcm or less. The film is made of a conductive material and a conductive material having optical transparency, and the reflection of visible light on the film is The emissivity is 20% to 80%, preferably 40% to 70%, and the resistivity is 1×10 - 2 It is assumed that the film has a resistance of less than Ωcm.

[0145] In the present embodiment, each light emitting element is divided into a first light emitting element (R) 410R and a second light emitting element (R). The transparent conductive layers (first transparent conductive layer 403a, second transparent conductive layer 403b) provided on the element (G) 410G are By changing the thickness of the transparent conductive layer 403b), the reflective electrode 401 and the semi-transparent The optical distance between the over- and semi-reflective electrodes 402 is changed. The emitted broad light is distributed between the reflective electrode 401 and the semi-transmissive and semi-reflective electrode 402 as follows: Since it is possible to strengthen the light of resonating wavelengths and attenuate the light of non-resonating wavelengths, By changing the optical distance between the reflective electrode 401 and the semi-transmissive / semi-reflective electrode 402, different It is possible to extract light of a certain wavelength.

[0146] The optical distance (also called the optical path length) is the actual distance multiplied by the refractive index. In the embodiment, it is expressed by multiplying the actual film thickness by n (refractive index). Optical distance = actual film thickness x n.

[0147] In the first light emitting element (R) 410R, the reflective electrode 401 is connected to the semi-transmissive and semi-reflective electrode 402. Total thickness up to 02 mλ R / 2 (where m is a natural number), the second light-emitting element (G) 410G The total thickness from the reflective electrode 401 to the semi-transmissive and semi-reflective electrode 402 is mλ G / 2 (where m In the third light emitting element (B) 410B, a semi-transmissive / semi-reflective electrode is formed from the reflective electrode 401. Total thickness up to pole 402 mλ B / 2 (where m is a natural number).

[0148] From the above, the first light-emitting element (R) 410R is mainly composed of the first The light (λ R ) is taken out, and the second light-emitting element (G) 4 From 10G, light was emitted mainly from the second light-emitting layer (G) 404G included in the EL layer 405. Light (λ G ) is extracted, and from the third light-emitting element (B) 410B, mainly the EL layer 405 The light (λ ) emitted from the first light emitting layer (B) 404B included in B ) is extracted. Light extracted from the light emitting element is emitted from the semi-transmissive and semi-reflective electrode 402 side.

[0149] In the above configuration, the total thickness from the reflective electrode 401 to the semi-transmissive and semi-reflective electrode 402 is Strictly speaking, the reflection region of the reflective electrode 401 is reflected by the reflection region of the semi-transmissive and semi-reflective electrode 402. However, the reflective electrode 401 and the semi-transmissive / semi-reflective electrode 40 Since it is difficult to precisely determine the position of the reflective region in the semiconductor device 2, the reflective electrode 401 and the semiconductor device 301 are The above-mentioned effect can be obtained sufficiently by assuming that any position of the transmissive / semi-reflective electrode 402 is a reflective region. It is possible to do so.

[0150] Next, in the first light-emitting element (R) 410R, the reflective electrode 401 is connected to the third light-emitting layer (R )404R, the optical distance is set to the desired film thickness ((2m'+1)λ R / 4 (where m' is a natural number )) to amplify the light emission from the third light-emitting layer (R) 404R. The light emitted from the third light-emitting layer (R) 404R is reflected by the reflective electrode 401. The light that is reflected back (first reflected light) is semi-transmitted and semi-reflected by the third light-emitting layer (R) 404R. Since interference occurs with the light (first incident light) directly incident on the electrode 402, the reflective electrode 401 The optical distance to the third light-emitting layer (R) 404R is set to a desired value ((2m'+1)λ R / 4 (where , m' is a natural number), the phase difference between the first reflected light and the first incident light is In combination, the light emitted from the third light-emitting layer (R) 404R can be amplified.

[0151] Strictly speaking, the optical distance between the reflective electrode 401 and the third light-emitting layer (R) 404R is The optical distance between the reflection area of ​​the electrode 401 and the light-emitting area of ​​the third light-emitting layer (R) 404R is However, the reflection region of the reflective electrode 401 and the third light-emitting layer (R) Since it is difficult to precisely determine the position of the light-emitting region in the reflective electrode 40 Assume that an arbitrary position of the third light-emitting layer (R) 404R is the reflective region and an arbitrary position of the third light-emitting layer (R) 404R is the light-emitting region. This will enable the above-mentioned effects to be obtained sufficiently.

[0152] Next, in the second light-emitting element (G) 410G, the second light-emitting layer (G )404G optical distance to the desired film thickness ((2m''+1)λ G / 4 (where m'' is the By adjusting the temperature (T) of the second light-emitting layer (G) 404G to a value equal to the temperature (T), the light emission from the second light-emitting layer (G) 404G can be amplified. The light emitted from the second light-emitting layer (G) 404G is reflected by the reflective electrode 401. The reflected light (second reflected light) is reflected by the second light emitting layer (G) 404G as a semi-transparent or semi-transparent light. Since the light (second incident light) directly incident on the reflective electrode 402 interferes with the reflective electrode 401, to the second light-emitting layer (G) 404G to a desired value ((2m''+1)λ G / 4( However, m'' is a natural number, so that the second reflected light and the second incident light By adjusting the phase with the second light-emitting layer (G) 404G, the light emitted from the second light-emitting layer (G) 404G can be amplified.

[0153] Strictly speaking, the optical distance between the reflective electrode 401 and the second light-emitting layer (G) 404G is The optical distance between the reflection area of ​​the electrode 401 and the light-emitting area of ​​the second light-emitting layer (G) 404G is However, the reflection region of the reflective electrode 401 and the second light-emitting layer (G) Since it is difficult to precisely determine the position of the light emitting region in the reflective electrode 40 Assume that an arbitrary position of the second light-emitting layer (G) 404G is the reflective region and an arbitrary position of the second light-emitting layer (G) 404G is the light-emitting region. This will enable the above-mentioned effects to be obtained sufficiently.

[0154] Next, in the third light-emitting element (B) 410B, the first light-emitting layer (B ) Set the optical distance to 404B at the desired thickness ((2m''+1)λ B / 4 (where m'' is a natural number), the light emission from the first light-emitting layer (B) 404B is amplified. The light emitted from the first light-emitting layer (B) 404B is reflected by the reflective electrode 401. The light reflected back by the first light-emitting layer (B) 404B is semi-transmitted. The light (third incident light) directly incident on the semi-reflective electrode 402 interferes with the light (third incident light) incident on the reflective electrode 4 The optical distance from the first light-emitting layer (B) 404B to the desired value ((2m'''+1)λ B / 4 (where m''' is a natural number), the third reflected light and the third The phase of the incident light can be adjusted to amplify the light emitted from the first light-emitting layer (B) 404B. can.

[0155] In the third light emitting element, the light between the reflective electrode 401 and the first light emitting layer (B) 404B is Strictly speaking, the optical distance is the distance between the reflective area of ​​the reflective electrode 401 and the first light-emitting layer (B) 404B. However, the reflectance of the reflective electrode 401 is different from that of the light emitting region. It is difficult to precisely determine the position of the light emitting region in the first light emitting layer (B) 404B. Therefore, any position of the reflective electrode 401 can be set as a reflective region, and any position of the first light-emitting layer (B) 404B can be set as a reflective region. It is assumed that the above-mentioned effect can be sufficiently obtained by assuming any desired position as the light emitting region.

[0156] In the above configuration, each of the light-emitting elements has a structure in which the EL layer has a plurality of light-emitting layers. However, the present invention is not limited to this. For example, the tank described in the third embodiment may be used. In combination with the structure of a DEM type light emitting device, a single light emitting device is sandwiched between charge generating layers to form multiple EL A single or multiple light-emitting layers may be formed in each EL layer.

[0157] The light-emitting device shown in this embodiment has a microcavity structure, and the same EL Even if the device has multiple layers, it is possible to extract light of different wavelengths from each light-emitting element, so RGB coating is possible. Therefore, it is easy to realize high resolution, and for this reason, This is advantageous in realizing color. In addition, it is possible to enhance the emission intensity of a specific wavelength in the front direction. This configuration allows for low power consumption by using pixels of three or more colors. This is particularly useful when applied to color displays (image display devices) using the same technology, but it is also useful in lighting and other applications. It may be used for any purpose.

[0158] (Embodiment 5) In this embodiment, a light-emitting device including a light-emitting element which is one embodiment of the present invention will be described. .

[0159] The light emitting device may be a passive matrix light emitting device or an active matrix light emitting device. The light-emitting device shown in this embodiment may be the same as that described in the other embodiments. A light emitting element can be applied.

[0160] In this embodiment mode, an active matrix light emitting device will be described with reference to FIG. .

[0161] 8A is a top view showing a light emitting device, and FIG. 8B is a top view showing FIG. 8A along a dashed line A- 1 is a cross-sectional view taken along line A' of an active matrix light-emitting device according to the present embodiment. A pixel section 502 and a driving circuit section (source line driving circuit) 50 are provided on an element substrate 501. 3 and a driver circuit section (gate line driver circuit) 504 (504a and 504b). The pixel portion 502, the driver circuit portion 503, and the driver circuit portion 504 are sealed by a sealant 505. It is sealed between the element substrate 501 and a sealing substrate 506 .

[0162] 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.

[0163] 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.

[0164] 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. It is not necessary to form the driving circuit on the substrate, but it is also possible to form the driving circuit externally.

[0165] 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 first electrode (anode) 513 is formed of a plurality of pixels. An insulator 514 is formed covering the end of the substrate 13. Here, a positive photosensitive acrylic is used. It is formed by using a resin.

[0166] In order to improve the coverage of the film to be laminated on the upper layer, the upper end of the insulator 514 It is preferable that a curved surface having a curvature is formed at the upper or lower end. When a positive photosensitive acrylic resin is used as the material of the insulating material 514, the upper end of the insulating material 514 It is preferable that the insulating layer has a curved surface with a radius of curvature (0.2 μm to 3 μm). Either a negative photosensitive resin or a positive photosensitive resin can be used as the material 514. It is possible to use not only organic compounds but also inorganic compounds such as silicon oxide and silicon oxynitride. Both of these can be used.

[0167] An EL layer 515 and a second electrode (cathode) 516 are laminated on a first electrode (anode) 513. The EL layer 515 is provided with at least a light-emitting layer. The EL layer 515 has a laminated structure as shown in the embodiment 1. A hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, a charge generation layer, etc. can be appropriately provided. Cut.

[0168] The total thickness of the first electrode (anode) 513, the EL layer 515, and the second electrode (cathode) 516 is The light-emitting element 517 is formed with a layer structure. The first electrode (anode) 513, the EL layer 515 The material used for the second electrode (cathode) 516 is the material shown in Embodiment 1. Although not shown here, the second electrode (cathode) 516 can be connected to an external input terminal The FPC 508 is electrically connected to the FPC 508.

[0169] In addition, although only one light-emitting element 517 is shown in the cross-sectional view shown in FIG. In the pixel section 502, a plurality of light emitting elements are arranged in a matrix. 02, selectively forming light-emitting elements that can emit three types of light (R, G, B), It is possible to form a light-emitting device capable of full color display. By combining these, a light emitting device capable of full color display may be obtained.

[0170] Furthermore, a sealing substrate 506 is bonded to the element substrate 501 with a sealant 505. The light is emitted into a space 518 surrounded by the element substrate 501, the sealing substrate 506, and the sealant 505. The structure is provided with an element 517. The space 518 is filled with an inert gas (such as nitrogen, etc.). In addition to the case where the cavity is filled with a gas such as argon, the cavity may also be filled with a sealing material 505. .

[0171] It is preferable to use epoxy resin or low-melting glass for the sealing material 505. It is desirable that these materials are as impermeable to moisture and oxygen as possible. Materials used for the sealing substrate 506 include glass substrates, quartz substrates, and FRP (Fibreglass). Ass-Reinforced Plastics), PVF (Polyvinyl fluoride) For example, a plastic substrate made of polyester, acrylic or the like can be used.

[0172] In this manner, an active matrix light emitting device can be obtained.

[0173] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiment modes. There can be.

[0174] (Embodiment 6) In this embodiment, a light-emitting device manufactured using a light-emitting element according to one embodiment of the present invention is used. Examples of various electronic devices completed using this method will be described with reference to FIGS. 9 and 10.

[0175] As an example of an electronic device to which a light-emitting device is applied, a television set (a television, (also called TV receivers), computer monitors, digital cameras, digital video digital cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), Examples include portable game machines, personal digital assistants, audio playback devices, and large game machines such as pachinko machines. Specific examples of these electronic devices are shown in Figure 9.

[0176] FIG. 9A shows an example of a television device. The television device 7100 includes: A display unit 7103 is built into the housing 7101. The display unit 7103 displays images. It is possible to use a light-emitting device in the display portion 7103. 7 shows a configuration in which a housing 7101 is supported by a stand 7105.

[0177] The television device 7100 can be operated using an operation switch provided on the housing 7101 or a separate remote control. This can be done by using the remote control operation device 7110. The channel and volume can be controlled by the 7109, and the display 7103 shows In addition, the remote control unit 7110 can be used to control the video. A display unit 7107 for displaying information output from the device 7110 may be provided.

[0178] The television device 7100 includes a receiver, a modem, and the like. It is possible to receive general television broadcasts, and furthermore to receive them by wired or wireless connection via a modem. By connecting to a communication network, it is possible to communicate in one direction (from sender to receiver) or two directions ( It is also possible to communicate information between a sender and a receiver, or between receivers themselves.

[0179] FIG. 9B shows a computer, which includes a main body 7201, a housing 7202, a display unit 7203, and a keyboard. keyboard 7204, external connection port 7205, pointing device 7206, etc. Note that the computer is manufactured by using a light-emitting device for the display portion 7203. .

[0180] FIG. 9C shows a portable game machine that is composed of two housings, a housing 7301 and a housing 7302. The housing 7301 is connected to the display unit 7302 by a connecting portion 7303 so as to be openable and closable. A display unit 7305 is incorporated in the housing 7302. The portable gaming machine shown in FIG. 9(C) also includes a speaker unit 7306 and a recording medium insertion unit 7307. , LED lamp 7308, input means (operation keys 7309, connection terminal 7310, sensor 73 11 (force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical Chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration , odor or infrared measuring function), microphone 7312) etc. Of course, the configuration of the portable gaming machine is not limited to the above, and at least the display unit 73 04 and the display portion 7305, or either one of them may use a light-emitting device. The portable gaming machine shown in FIG. The function of reading out the programs or data recorded on the media and displaying them on the display unit, and other It has a function to share information with the portable game machine by wireless communication. The functions of the portable gaming machine are not limited to these, and the portable gaming machine may have a variety of functions.

[0181] FIG. 9D shows an example of a mobile phone. A mobile phone 7400 includes a housing 7401. In addition to the display unit 7402, operation buttons 7403, an external connection port 7404, The mobile phone 7400 is equipped with a speaker 7405, a microphone 7406, and the like. The device is used for the display portion 7402 .

[0182] In a mobile phone 7400 shown in FIG. 9D, information is displayed by touching a display portion 7402 with a finger or the like. You can also make calls, write emails, and perform other operations. This can be done by touching the display portion 7402 with a finger or the like.

[0183] The screen of the display unit 7402 has three main modes. The first is a mode that mainly displays images. The first mode is a display mode, the second is an input mode for inputting information such as characters, and the third mode is a display mode. This is a display + input mode that combines the display mode and the input mode.

[0184] For example, when making a call or composing an e-mail, the display unit 7402 is used for inputting characters. The main input mode is the character input mode, and the input operation of the characters displayed on the screen can be performed. In this case, it is preferable to display a keyboard or number buttons on most of the screen of the display portion 7402. I wish.

[0185] In addition, a sensor for detecting tilt, such as a gyro or an acceleration sensor, is installed inside the mobile phone 7400. By providing a detection device having the above, the orientation of the mobile phone 7400 (portrait or landscape) can be determined, The screen display on the display portion 7402 can be automatically switched.

[0186] The screen mode can be changed by touching the display portion 7402 or by operating the housing 7401. The type of image displayed on the display unit 7402 can be selected by operating the operation button 7403. For example, the image signal to be displayed on the display unit may be changed by If the data is text data, the mode switches to input mode.

[0187] In the input mode, the optical sensor of the display unit 7402 detects a signal and displays the If there is no input by touch operation on the display unit 7402 for a certain period of time, the screen mode is changed to the input mode. Alternatively, the display mode may be switched from the display mode to the display mode.

[0188] The display unit 7402 can also function as an image sensor. By touching 402 with a palm or a finger and capturing an image of a palm print, fingerprint, or the like, personal authentication can be performed. In addition, a backlight that emits near-infrared light to the display unit or a sensing light that emits near-infrared light By using a source, it is also possible to image finger veins, palm veins, etc.

[0189] FIG. 10(A) and FIG. 10(B) show a tablet-type terminal that can be folded in two. FIG. 9631a, the tablet terminal is in an open state. 9631b, a display mode changeover switch 9034, a power switch 9035, a power saving mode The device has a mode changeover switch 9036, a fastener 9033, and an operation switch 9038. The tablet terminal has a light emitting device in one of the display portions 9631a and 9631b. It is made by using both.

[0190] A part of the display unit 9631a can be used as a touch panel area 9632a. By touching the operation keys 9637 displayed on the display unit 96, data can be input. In 31a, as an example, half of the area has a display function only, and the other half The display unit 96 has a touch panel function, but is not limited to this. The entire area of ​​the display unit 931a may have a touch panel function. The entire surface of 631a is made to display keyboard buttons to serve as a touch panel, and the display section 9631b is made to display It can be used as a display screen.

[0191] In addition, in the display unit 9631b, as in the display unit 9631a, The part of the touch panel can be the area 9632b of the touch panel. Touch the area where the mode display switch button 9639 is displayed with your finger or a stylus. A keyboard button can be displayed on the display portion 9631b.

[0192] In addition, the touch panel area 9632a and the touch panel area 9632b are simultaneously You can also use touch input.

[0193] A display mode changeover switch 9034 is used to change the display orientation, such as portrait or landscape. You can switch between black and white and color display. The switch 9036 is a switch that turns on and off when the tablet terminal is in use and is detected by a light sensor built into the tablet terminal. The brightness of the display can be optimized according to the amount of light. In addition to sensors, other detection devices such as gyros, acceleration sensors, etc. that detect tilt may be incorporated.

[0194] FIG. 10A shows an example in which the display area of ​​the display portion 9631b is the same as that of the display portion 9631a. However, there is no particular limitation, and one size may be different from the other size. The quality of the display may also be different. For example, one display panel may provide a higher resolution display than the other. It may also be used as a rule.

[0195] FIG. 10B shows the tablet terminal in a closed state. The tablet terminal includes a housing 9630 and a solar cell 9 633, a charge / discharge control circuit 9634, a battery 9635, and a DCDC converter 9636 In addition, in FIG. 10B, a battery 963 is used as an example of the charge and discharge control circuit 9634. 5. A configuration having a DC-DC converter 9636 is shown.

[0196] In addition, since the tablet device can be folded in half, the case 9630 can be folded when not in use. Therefore, the display portions 9631a and 9631b can be protected. This makes it possible to provide a tablet device that is highly durable and reliable even when used for a long period of time.

[0197] In addition, the tablet terminals shown in Figs. 10(A) and 10(B) can be used in various Functions that display information (still images, videos, text images, etc.), calendars, dates, or times A function to display information on the display unit, and a function to input or edit information displayed on the display unit. It has input functions, functions to control processing by various software (programs), etc. It is possible.

[0198] The solar cell 9633 attached to the surface of the tablet device supplies power to the touch panel. The solar cell 9633 can supply the light to a display unit, a video signal processor, or the like. The battery 9635 can be efficiently charged by providing a light-emitting diode (LED) on one or both sides of the housing 9630. The battery 9635 may be a lithium ion battery. The use of the above has the advantage of enabling miniaturization.

[0199] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. A block diagram is shown in FIG. 10(C) and will be explained. FIG. 10(C) shows a solar cell 9633, a battery 9 635, DC-DC converter 9636, converter 9638, switches SW1 to SW3 , a display unit 9631, a battery 9635, a DC-DC converter 963 6. The converter 9638 and the switches SW1 to SW3 are configured to control charging and discharging as shown in FIG. 10(B). This corresponds to the circuit 9634 .

[0200] First, an example of operation in which power is generated by the solar cell 9633 using external light will be described. The power generated by the solar cell 9633 becomes the voltage for charging the battery 9635. The voltage is increased or decreased by the DC-DC converter 9636. When power is used from the Solar Cell 9633, switch SW1 is turned on and the The inverter 9638 increases or decreases the voltage to the voltage required for the display unit 9631. When the display unit 9631 is not to be displayed, the switch SW1 is turned off and the switch S The configuration can be such that W2 is turned on and the battery 9635 is charged.

[0201] The solar cell 9633 is shown as an example of a power generating means, but is not limited thereto. Other power generation methods such as piezoelectric elements and thermoelectric conversion elements (Peltier elements) For example, the battery 9635 may be charged. A non-contact power transmission module that receives and charges, or a structure that combines other charging methods It may also be composed of.

[0202] In addition, if the display unit described in the above embodiment is provided, the electronic device shown in FIG. Needless to say, there is no particular limitation.

[0203] In the above manner, an electronic device can be obtained by using the light-emitting device which is one embodiment of the present invention. The range of applications for light-emitting devices is extremely wide, and they can be used in electronic devices in a wide range of fields. It is.

[0204] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. There can be.

[0205] (Embodiment 7) In this embodiment, a lighting device including a light-emitting device which is one embodiment of the present invention is used. An example of this will be described with reference to FIG.

[0206] FIG. 11 shows an example in which the light emitting device is used as an indoor lighting device 8001. Since the surface area can be increased, a large-area lighting device can be formed. By using a housing having such a shape, a lighting device 8002 having a curved light-emitting area can be formed. The light-emitting element included in the light-emitting device shown in this embodiment mode is a thin film, and the design of the housing This allows for a high degree of freedom in designing lighting devices with a wide variety of elaborate designs. Furthermore, a large lighting device 8003 may be provided on the wall of the room.

[0207] In addition, by using a light-emitting device on the surface of a table, a lighting device that also functions as a table can be provided. The lighting device 8004 can be used as a lighting device. This makes it possible to provide a lighting device that also functions as furniture.

[0208] As described above, various lighting devices using the light-emitting device can be obtained. The device is considered to be included in one aspect of the present invention.

[0209] The structure described in this embodiment may be used in appropriate combination with structures described in other embodiments. There can be. EXAMPLES

[0210] In this example, a light-emitting element 1 which is one embodiment of the present invention will be described with reference to FIG. The chemical formulas of the materials used in this embodiment are shown below.

[0211] [ka]

[0212] <Fabrication of light-emitting element 1> First, indium tin oxide containing silicon oxide (ITSO) is deposited on a glass substrate 1100. A film was formed by sputtering to form a first electrode 1101 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm x 2 mm.

[0213] Next, as a pretreatment for forming the light emitting element 1 on the substrate 1100, the substrate surface is washed with water. After cleaning, it was baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0214] Then, 10 -4 The substrate is introduced into a vacuum deposition apparatus whose inside has been reduced in pressure to about Pa. After vacuum baking at 170° C. for 30 minutes in a heating chamber in the deposition apparatus, the substrate 1100 is It was left to cool for about 30 minutes.

[0215] Next, the substrate 1100 is vacuum-steamed so that the surface on which the first electrode 1101 is formed faces downward. In this embodiment, the EL layer 1 was formed by vacuum deposition. 002, a hole injection layer 1111, a hole transport layer 1112, a light emitting layer 1113, and an electron transport A case where the layer 1114 and the electron injection layer 1115 are formed in this order will be described.

[0216] 10 minutes inside the vacuum chamber -4 After depressurizing to 100 Pa, 1,3,5-tri(dibenzothiophene-4 -yl)-benzene (abbreviation: DBT3P-II) and molybdenum(VI) oxide were 3P-II (abbreviation): molybdenum oxide = 4:2 (mass ratio) Thus, a hole injection layer 1111 was formed on the first electrode 1101. The film thickness was set to 40 nm. Co-evaporation is a method of simultaneously evaporating multiple different substances from different evaporation sources. It is law.

[0217] Next, 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine A hole transport layer 1112 is formed by depositing 20 nm of BPAFLP. Ta.

[0218] Next, the light-emitting layer 1113 was formed on the hole-transporting layer 1112. [4-phenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 4,4'-di(1-naphthyl)-4''-(9-phenyl PCBNBB, (Aryl-9H-carbazol-3-yl)triphenylamine Cetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium (III) (abbreviation: [Ir(tBuppm)2(acac)]) Bq-II (abbreviation): PCBNBB (abbreviation): [Ir(tBuppm)2(acac)] (abbreviation) = 0.7:0.3:0.05 (mass ratio) to form a first light-emitting layer 11 After forming 13a with a thickness of 15 nm, 2mDBTBPDBq-II (abbreviation): PCBN BB(abbreviation):[Ir(tBuppm)2(acac)](abbreviation)=0.8:0.2:0 The second light-emitting layer 1113b was formed to a thickness of 25 nm by co-evaporation so that the ratio of the first layer and the second layer was 0.05 (mass ratio). By forming the layers, a light emitting layer 1113 having a laminated structure was formed.

[0219] Next, 2mDBTBPDBq-II (abbreviation) was evaporated to a thickness of 10 nm on the light-emitting layer 1113. Electron transport was achieved by depositing 20 nm of bathophenanthroline (abbreviation: Bphen). A layer 1114 was formed. Furthermore, lithium fluoride was evaporated to a thickness of 1 nm on the electron transport layer 1114. In this way, an electron injection layer 1115 was formed.

[0220] Finally, aluminum was evaporated onto the electron injection layer 1115 to a thickness of 200 nm. Then, a second electrode 1103 serving as a cathode was formed, and a light-emitting element 1 was obtained. In all depositions, a resistance heating method was used.

[0221] The element structure of the thus obtained Light-emitting Element 1 is shown in Table 1.

[0222] [Table 1]

[0223] The fabricated light-emitting element 1 was placed in a glove box with a nitrogen atmosphere to prevent it from being exposed to the air. (Sealing material was applied around the element, and heat treatment was performed at 80°C for 1 hour during sealing.) ).

[0224] <Operation characteristics of light-emitting element 1> The operating characteristics of the fabricated light-emitting element 1 were measured. The measurements were performed at room temperature (25° C.). The atmosphere was very friendly.

[0225] First, the current density-luminance characteristics of the light-emitting element 1 are shown in FIG. is the luminance (cd / m 2 ), the horizontal axis is the current density (mA / cm 2 ) is shown. The voltage-luminance characteristics are shown in FIG. 14. In FIG. 14, the vertical axis represents luminance (cd / m 2 ), The horizontal axis represents voltage (V). The luminance vs. current efficiency characteristics of the light-emitting element 1 are shown in FIG. In FIG. 15, the vertical axis represents current efficiency (cd / A) and the horizontal axis represents luminance (cd / m 2 ) FIG. 16 shows the voltage-current characteristics of the light-emitting element 1. In FIG. , current (mA), and the horizontal axis indicates voltage (V).

[0226] FIG. 14 shows that the light-emitting element 1 of one embodiment of the present invention is a highly efficient element. Also, 1000cd / m 2 The main initial characteristic values ​​of the light-emitting element 1 in the vicinity are shown in Table 2 below. vinegar.

[0227] [Table 2]

[0228] From the above results, the light-emitting device 1 fabricated in this example exhibits high external quantum efficiency. It can be seen that the device shows high luminous efficiency. Furthermore, in terms of color purity, it emits yellow-green light with good purity. It can be seen that

[0229] In addition, the light-emitting element 1 is supplied with 25 mA / cm 2 The emission spectrum when a current is applied at a current density of 17. As shown in FIG. 17, the emission spectrum of the light-emitting element 1 has a peak at about 550 nm. The phosphorescent organometallic iridium complex [Ir(tBuppm)2(acac It is suggested that this is due to the emission of

[0230] The results of the reliability test on the light-emitting element 1 are shown in FIG. indicates the normalized luminance (%) when the initial luminance is 100%, and the horizontal axis indicates the driving time of the element (h). For comparison, the light-emitting layer was 2mDBTBPDBq-II (abbreviation: PCBNB B(abbreviation):[Ir(tBuppm)2(acac)](abbreviation)=0.8:0.2:0. 05 (mass ratio), and a film thickness of 40 nm was formed. The other structures were light-emitting elements. A comparative light-emitting device was prepared in the same manner as in Example 1, and a reliability test was performed in the same manner. , initial brightness 5000cd / m 2 The current density was set to constant and the light-emitting element 1 and comparison The light-emitting element was driven. As a result, the luminance of the comparative light-emitting element after 500 hours was 1 / 100 of the initial luminance. The luminance of the light-emitting element 1 after 500 hours was 85% of the initial luminance, whereas the luminance of the light-emitting element 2 after 500 hours was 85% of the initial luminance. It maintained about 90% of its value.

[0231] Therefore, it was found that the light-emitting element 1 is a highly reliable light-emitting element with a long life. Ta.

[0232] In addition, 2mDBTBPDBq-II (abbreviation), PCBNBB (abbreviation), and 2mDBT A mixed film of BPDBq-II (abbreviation) and PCBNBB (abbreviation) was prepared, and each film was Photoluminescence (PL) was measured. As a result, 2mDBTBPDBq-II (abbreviation The photoluminescence (PL) peak wavelength of the evaporated film of PCBNB is 428 nm. The PL peak wavelength of the evaporated film of B (abbreviation) is 428 nm, while the co-evaporated The PL peak wavelength of the mixed film was 501 nm, which was significantly shifted to longer wavelengths. 2mDBTBPDBq-II (abbreviation) and PCBNBB (abbreviation) are compounds that form exciplexes. It turned out to be a combination. EXAMPLES

[0233] In this example, a light-emitting element 2 which is one embodiment of the present invention will be described. The light emitting element 2 will be described with reference to FIG. 12 used for the description of the light emitting element 1 in the first embodiment. The chemical formulas of the materials used in this embodiment are shown below.

[0234] [ka]

[0235] <Fabrication of light-emitting element 2> First, indium tin oxide containing silicon oxide (ITSO) is deposited on a glass substrate 1100. A film was formed by sputtering to form a first electrode 1101 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm x 2 mm.

[0236] Next, as a pretreatment for forming the light emitting element 2 on the substrate 1100, the substrate surface is washed with water. After cleaning, it was baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0237] Then, 10 -4 The substrate is introduced into a vacuum deposition apparatus whose inside has been reduced in pressure to about Pa. After vacuum baking at 170° C. for 30 minutes in a heating chamber in the deposition apparatus, the substrate 1100 is It was left to cool for about 30 minutes.

[0238] Next, the substrate 1100 is vacuum-steamed so that the surface on which the first electrode 1101 is formed faces downward. In this embodiment, the EL layer 1 was formed by vacuum deposition. 002, a hole injection layer 1111, a hole transport layer 1112, a light emitting layer 1113, and an electron transport A case where the layer 1114 and the electron injection layer 1115 are formed in this order will be described.

[0239] 10 minutes inside the vacuum chamber -4 After reducing the pressure to 100 Pa, 4-phenyl-4'-(9-phenylfluoro (9-phenyl-1,2-diphenyl-2,4-di ... and co-evaporated to a mass ratio of BPAFLP (abbreviation):molybdenum oxide = 1:0.5. The hole injection layer 1111 was formed on the first electrode 1101 by deposition. The co-evaporation method is to simultaneously evaporate different substances from different evaporation sources. This is a deposition method that causes light to be emitted.

[0240] Next, BPAFLP (abbreviation) is evaporated to a thickness of 20 nm to form a hole transport layer 1112. Successful.

[0241] Next, the light-emitting layer 1113 was formed on the hole-transporting layer 1112. 2mDBTPD Bq-II), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl) Triphenylamine (abbreviation: PCBA1BP), (acetylacetonato)bis(6-methyl Ir(mppm)2( acac)]) was added to 2mDBTPDBq-II (abbreviation): PCBA1BP (abbreviation): [I r(mppm)2(acac)] (abbreviation) = 0.7:0.3:0.06 (mass ratio) The first light-emitting layer 1113a was formed to a thickness of 20 nm by co-evaporation, and then 2mDBTPD Bq-II (abbreviation), PCBA1BP (abbreviation), Bis(2,3,5-triphenylpyridine) Nato)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr)2( dpm)]) was added to 2mDBTPDBq-II (abbreviation): PCBA1BP (abbreviation): [Ir (tppr)2(dpm)] (abbreviation) = 0.8:0.2:0.03 (mass ratio) The second light-emitting layer 1113b is formed to a thickness of 20 nm by co-evaporation on the first light-emitting layer 1113a. A light emitting layer 1113 was formed.

[0242] Next, 2mDBTPDBq-II (abbreviation) was evaporated to a thickness of 15 nm on the light-emitting layer 1113, and then An electron transport layer was created by depositing 15 nm of bathophenanthroline (abbreviation: Bphen). Further, lithium fluoride was evaporated to a thickness of 1 nm on the electron transport layer 1114. In this way, an electron injection layer 1115 was formed.

[0243] Finally, aluminum was evaporated onto the electron injection layer 1115 to a thickness of 200 nm. Then, a second electrode 1103 serving as a cathode was formed, and a light-emitting element 2 was obtained. In all the depositions, a resistance heating method was used.

[0244] The element structure of the thus obtained Light-emitting Element 2 is shown in Table 3.

[0245] [Table 3]

[0246] The fabricated light-emitting element 2 was placed in a glove box with a nitrogen atmosphere to prevent it from being exposed to the air. (Sealing material was applied around the element, and heat treatment was performed at 80°C for 1 hour during sealing.) ).

[0247] <Operation characteristics of light-emitting element 2> The operating characteristics of the fabricated light-emitting element 2 were measured. The measurements were performed at room temperature (25° C.). The atmosphere was very friendly.

[0248] First, the current density-luminance characteristics of the light-emitting element 2 are shown in FIG. is the luminance (cd / m 2 ), the horizontal axis is the current density (mA / cm 2 ) is shown. Also, the light-emitting element 2 The voltage-luminance characteristics are shown in FIG. 20. In FIG. 20, the vertical axis indicates luminance (cd / m 2 ), The horizontal axis represents voltage (V). The luminance vs. current efficiency characteristics of the light-emitting element 2 are shown in FIG. In FIG. 21, the vertical axis represents current efficiency (cd / A) and the horizontal axis represents luminance (cd / m 2 ) FIG. 22 shows the voltage-current characteristics of the light-emitting element 2. In FIG. , current (mA), and the horizontal axis indicates voltage (V).

[0249] FIG. 21 shows that the light-emitting element 2 of one embodiment of the present invention is a highly efficient element. Also, 1000cd / m 2 The main initial characteristic values ​​of the light-emitting element 2 in the vicinity are shown in Table 4 below. vinegar.

[0250] [Table 4]

[0251] From the above results, the light-emitting device 2 fabricated in this example exhibits high external quantum efficiency. , and shows high luminous efficiency.

[0252] In addition, the light-emitting element 2 is rated at 25 mA / cm 2 The emission spectrum when a current is applied at a current density of 23. As shown in FIG. 23, the emission spectrum of the light-emitting element 2 is 550 nm, 620 nm, The phosphorescent organometallic iridium complexes [Ir(mpp m)2(acac)] (abbreviation), [Ir(tppr)2(dpm)] (abbreviation) This suggests that

[0253] In addition, 2mDBTPDBq-II (abbreviation), PCBA1BP (abbreviation), and 2mDBT A mixed film of PDBq-II (abbreviation) and PCBA1BP (abbreviation) was prepared, and each Photoluminescence (PL) was measured. As a result, 2mDBTPDBq-II (abbreviation) The photoluminescence (PL) peak wavelength of the evaporated film is 426 nm. The PL peak wavelength of the evaporated film of P (abbreviation) is 416 nm, while the co-evaporated The PL peak wavelength of the mixed film was 519 nm, which was significantly shifted to longer wavelengths. 2mDBTPDBq-II (abbreviation) and PCBA1BP (abbreviation) are compounds that form exciplexes. It turned out to be a combination. EXAMPLES

[0254] In this example, a light-emitting element 3 shown in FIG. 24 was fabricated, and its operating characteristics and reliability were measured. The light-emitting element 3 fabricated in this example had a charge generating layer as described in the third embodiment. This is a light-emitting element having a structure in which multiple EL layers are sandwiched (hereinafter referred to as a tandem-type light-emitting element). The chemical formulas of the materials used in this embodiment are shown below.

[0255] [ka]

[0256] [ka]

[0257] <Fabrication of light-emitting element 3> First, indium tin oxide containing silicon oxide (ITSO) is deposited on a glass substrate 3000. A film was formed by sputtering to form a first electrode 3001 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm x 2 mm.

[0258] Next, as a pretreatment for forming the light emitting element 3 on the substrate 3000, the substrate surface is washed with water. After cleaning, it was baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0259] Then, 10 -4 The substrate is introduced into a vacuum deposition apparatus whose inside has been reduced in pressure to about Pa. After vacuum baking at 170° C. for 30 minutes in the heating chamber of the deposition apparatus, the substrate 3000 It was allowed to cool for about 30 minutes.

[0260] Next, the substrate 3000 is vacuum-steamed so that the surface on which the first electrode 3001 is formed faces downward. The first electrode was fixed to a holder provided in the deposition apparatus. The L layer 3002a includes a first hole injection layer 3011a and a first hole transport layer 3012a. The light-emitting layer (A) 3013a, the first electron transport layer 3014a, and the first electron injection layer 3015a After the sequential formation, the charge generating layer 3004 is formed, and then the second EL layer 3002b is formed. A second hole injection layer 3011b, a second hole transport layer 3012b, a light emitting layer (B) 3013b, The case where the second electron transport layer 3014b and the second electron injection layer 3015b are formed will be described. do.

[0261] 10 minutes inside the vacuum chamber -4 After reducing the pressure to 100 Pa, 9-[4-(9-phenylcarbazole-3 -yl)]phenyl-10-phenylanthracene (abbreviation: PCzPA) and molybdenum oxide The ratio of PCzPA (abbreviation):molybdenum oxide was 1:0.5 (mass ratio). The first hole injection layer 3011a is formed on the first electrode 3001 by co-evaporation as shown in FIG. The film thickness was 90 nm. Co-evaporation is a process in which different materials are evaporated in different layers. This is a deposition method in which the material is evaporated simultaneously from the source.

[0262] Next, PCzPA (abbreviation) is evaporated to a thickness of 30 nm to form a first hole transport layer 3012. a was formed.

[0263] Next, the light-emitting layer (A) 3013a was formed on the first hole transport layer 3012a. -(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: C zPA), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl 1,6-diaminopyrene-1,6-diamine (abbreviation: 1, 6mMemFLPAPrn), CzPA (abbreviation): 1,6mMemFLPAPrn (abbreviation The light-emitting layer (A) 3013a is formed by co-evaporating the material so that the mass ratio of the material (A) is 1:0.05. The film thickness was 30 nm.

[0264] Next, CzPA (abbreviation) was deposited to a thickness of 5 nm on the light-emitting layer (A) 3013a, and then The first electron transport layer was formed by depositing 15 nm of isophenanthroline (abbreviation: Bphen). Further, lithium oxide (LiO 2 ) was formed on the first electron transport layer 3014a. A 0.1 nm thick layer of i2O was deposited to form a first electron injection layer 3015a.

[0265] Next, copper phthalocyanine (abbreviation: CuPc) was deposited to a thickness on the first electron injection layer 3015a. A charge generating layer 3004 was formed by vapor deposition at 2 nm.

[0266] Next, 4-phenyl-4'-(9-phenylfluorene-9 -yl)triphenylamine (abbreviation: BPAFLP) and molybdenum(VI) oxide, The mixture was co-evaporated so that the ratio of PAFLP (abbreviation) to molybdenum oxide was 1:0.5 (by mass). Thus, the second hole injection layer 3011b was formed. The film thickness was set to 60 nm.

[0267] Next, BPAFLP (abbreviation) is evaporated to a thickness of 20 nm to form a second hole transport layer 301 2b was formed.

[0268] Next, the light-emitting layer (B) 3013b was formed on the second hole transport layer 3012b. -(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation : 2mDBTPDBq-II), 4-phenyl-4'-(9-phenyl-9H-carbazo (acetylacetonate) )Bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir (mppm)2(acac)]) was used as a template for 2mDBTPDBq-II (abbreviation): PCBA1B P(abbreviation):[Ir(mppm)2(acac)](abbreviation)=0.6:0.4:0.06 (mass ratio), and the first light-emitting layer (first light-emitting layer) 3013 (b1) was co-evaporated at 1 After forming the film with a thickness of 0 nm, 2mDBTPDBq-II (abbreviation), PCBA1BP (abbreviation ), (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(II I) (abbreviation: [Ir(dppm)2(acac)]) Name): PCBA1BP (abbreviation): [Ir(dppm)2(acac)] (abbreviation) = 0.8 : 0.2:0.06 (mass ratio) to form the second light-emitting layer (second light-emitting layer). 3013(b2) is formed to a thickness of 30 nm to form a light-emitting layer (B) 30 having a laminated structure. 13b was formed.

[0269] Next, 2mDBTPDBq-II (abbreviation) is evaporated to a thickness of 15 nm on the light-emitting layer (B) 3013b. Then, Bphen (abbreviation) is evaporated to a thickness of 15 nm to form a second electron transport layer 3014. Further, lithium fluoride (LiF) was deposited on the second electron transport layer 3014b. The second electron injection layer 3015b was formed by evaporation to a thickness of 1 nm.

[0270] Finally, aluminum was deposited on the second electron injection layer 3015b to a thickness of 200 nm. Then, a second electrode 3003 serving as a cathode was formed by vapor deposition on the substrate, and a light-emitting element 3 was obtained. In the deposition process, the deposition was all performed using a resistance heating method.

[0271] The element structure of the thus obtained Light-emitting Element 3 is shown in Table 5.

[0272] [Table 5]

[0273] The fabricated light-emitting element 3 was placed in a glove box with a nitrogen atmosphere to prevent it from being exposed to the air. (Sealing material was applied around the element, and heat treatment was performed at 80°C for 1 hour during sealing.) ).

[0274] <Operation characteristics of light-emitting element 3> The operating characteristics of the fabricated light-emitting element 3 were measured. The measurements were performed at room temperature (25° C.). The atmosphere was very friendly.

[0275] First, the current density-luminance characteristics of the light-emitting element 3 are shown in FIG. is the luminance (cd / m 2 ), the horizontal axis is the current density (mA / cm 2 ) is shown. Also, the light-emitting element 3 The voltage-luminance characteristics are shown in FIG. 26. In FIG. 26, the vertical axis represents luminance (cd / m 2 ), The horizontal axis represents voltage (V). The luminance vs. current efficiency characteristics of the light-emitting element 3 are shown in FIG. In FIG. 27, the vertical axis represents current efficiency (cd / A) and the horizontal axis represents luminance (cd / m 2 ) FIG. 28 shows the voltage-current characteristics of the light-emitting element 3. In FIG. 28, the vertical axis , current (mA), and the horizontal axis indicates voltage (V).

[0276] FIG. 27 shows that the light-emitting element 3 of one embodiment of the present invention is a highly efficient element. Also, 1000cd / m 2 The main initial characteristic values ​​of the light-emitting element 3 in the vicinity are shown in Table 6 below. vinegar.

[0277] [Table 6]

[0278] From the above results, the light-emitting device 3 fabricated in this example exhibits high external quantum efficiency. , and shows high luminous efficiency.

[0279] In addition, the light-emitting element 3 is supplied with 25 mA / cm 2 The emission spectrum when a current is applied at a current density of 29. As shown in FIG. 29, the emission spectrum of the light-emitting element 3 is 467 nm, 587 nm, The phosphorescent organometallic iridium complexes contained in each light-emitting layer have peaks at 1 nm. This suggests that this is due to the emission of

[0280] As shown in Example 2, 2mDBTPDBq-II (abbreviation) and PCBA1 BP (abbreviation) is a combination that forms an exciplex. EXAMPLES

[0281] In this example, a light-emitting element 4 which is one embodiment of the present invention will be described with reference to FIG. The chemical formulas of the materials used in this embodiment are shown below.

[0282] [ka]

[0283] <Fabrication of light-emitting element 4> First, indium tin oxide containing silicon oxide (ITSO) is deposited on a glass substrate 1100. A film was formed by sputtering to form a first electrode 1101 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm x 2 mm.

[0284] Next, as a pretreatment for forming the light emitting element 4 on the substrate 1100, the substrate surface is washed with water. After cleaning, it was baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0285] Then, 10 -4 The substrate is introduced into a vacuum deposition apparatus whose inside has been reduced in pressure to about Pa. After vacuum baking at 170° C. for 30 minutes in a heating chamber in the deposition apparatus, the substrate 1100 is It was left to cool for about 30 minutes.

[0286] Next, the substrate 1100 is vacuum-steamed so that the surface on which the first electrode 1101 is formed faces downward. In this embodiment, the EL layer 1 was formed by vacuum deposition. 102 comprises a hole injection layer 1111, a hole transport layer 1112, a light emitting layer 1113, and an electron transport A case where the layer 1114 and the electron injection layer 1115 are formed in this order will be described.

[0287] 10 minutes inside the vacuum chamber -4 After depressurizing to 100 Pa, 1,3,5-tri(dibenzothiophene-4 -yl)-benzene (abbreviation: DBT3P-II) and molybdenum(VI) oxide were 3P-II (abbreviation): molybdenum oxide = 4:2 (mass ratio) Thus, a hole injection layer 1111 was formed on the first electrode 1101. The film thickness was set to 20 nm. Co-evaporation is a method of simultaneously evaporating multiple different substances from different evaporation sources. It is law.

[0288] Next, 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine A hole transport layer 1112 is formed by depositing 20 nm of BPAFLP. Ta.

[0289] Next, the light-emitting layer 1113 was formed on the hole-transporting layer 1112. [4-phenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 4,4'-di(1-naphthyl)-4''-(9-phenyl PCBNBB, (Aryl-9H-carbazol-3-yl)triphenylamine Cetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) Name: [Ir(dppm)2(acac)]) and 2mDBTBPDBq-II (abbreviation): PCBNBB (abbreviation): [Ir(dppm)2(acac)] (abbreviation) = 0.7:0.3 0.05 (mass ratio), and the first light-emitting layer 1113a was formed to a thickness of 20 nm. After formation, 2mDBTBPDBq-II (abbreviation): PCBNBB (abbreviation): [Ir(d ppm)2(acac)] (abbreviation) = 0.8:0.2:0.05 (mass ratio) The second light-emitting layer 1113b is formed to a thickness of 20 nm by co-evaporation to form a laminated structure. A light-emitting layer 1113 was formed.

[0290] Next, 2mDBTBPDBq-II (abbreviation) was evaporated onto the light-emitting layer 1113 to a thickness of 20 nm. Electron transport was achieved by depositing 20 nm of bathophenanthroline (abbreviation: Bphen). A layer 1114 was formed. Furthermore, lithium fluoride was evaporated to a thickness of 1 nm on the electron transport layer 1114. In this way, an electron injection layer 1115 was formed.

[0291] Finally, aluminum was evaporated onto the electron injection layer 1115 to a thickness of 200 nm. Then, a second electrode 1103 serving as a cathode was formed, and a light-emitting element 4 was obtained. In all the depositions, a resistance heating method was used.

[0292] The element structure of the thus obtained Light-emitting Element 4 is shown in Table 7.

[0293] [Table 7]

[0294] The fabricated light-emitting element 4 was placed in a glove box with a nitrogen atmosphere to prevent it from being exposed to the air. (Sealing material was applied around the element, and heat treatment was performed at 80°C for 1 hour during sealing.) ).

[0295] <Operation characteristics of light-emitting element 4> The operating characteristics of the fabricated light-emitting element 4 were measured. The measurements were performed at room temperature (25° C.). The atmosphere was very friendly.

[0296] First, the current density-luminance characteristics of the light-emitting element 4 are shown in FIG. is the luminance (cd / m 2 ), the horizontal axis is the current density (mA / cm 2 ) is shown. The voltage-luminance characteristics are shown in FIG. 31. In FIG. 31, the vertical axis indicates luminance (cd / m 2 ), The horizontal axis represents voltage (V). FIG. 32 shows the luminance vs. current efficiency characteristics of the light-emitting element 4. In FIG. 32, the vertical axis represents current efficiency (cd / A) and the horizontal axis represents luminance (cd / m 2 ) FIG. 33 shows the voltage-current characteristics of the light-emitting element 4. In FIG. , current (mA), and the horizontal axis indicates voltage (V).

[0297] As shown in FIG. 32, the light-emitting element 4 of one embodiment of the present invention is a highly efficient element. Also, 1000cd / m 2 The main initial characteristic values ​​of the light-emitting element 4 in the vicinity are shown in Table 8 below. vinegar.

[0298] [Table 8]

[0299] From the above results, the light-emitting device 4 fabricated in this example exhibits high external quantum efficiency. It can be seen that the luminous efficiency is high. Furthermore, in terms of color purity, it emits orange light with good purity. It is clear that this is the case.

[0300] In addition, the light-emitting element 4 is supplied with 25 mA / cm 2 The emission spectrum when a current is applied at a current density of As shown in FIG. 34, the emission spectrum of the light-emitting element 4 has a peak at about 586 nm. The phosphorescent organometallic iridium complex [Ir(dppm)2(acac)] This suggests that this is due to the emission of

[0301] The results of the reliability test on the light-emitting element 4 are shown in FIG. indicates the normalized luminance (%) when the initial luminance is 100%, and the horizontal axis indicates the driving time of the element (h). The reliability test was performed with an initial brightness of 5000cd / m 2 and the current density is constant. As a result, the luminance of the light-emitting element 4 after 1610 hours was It retained about 94% of its brightness.

[0302] Therefore, it was found that the light-emitting element 4 is a highly reliable light-emitting element with a long life. Ta.

[0303] As shown in Example 1, 2mDBTBPDBq-II (abbreviation) and PCBN BB (abbreviation) is a combination that forms an exciplex. EXAMPLES

[0304] In this example, a light-emitting element 5 which is one embodiment of the present invention will be described with reference to FIG. The chemical formulas of the materials used in this embodiment are shown below.

[0305] [ka]

[0306] <Fabrication of Light-Emitting Element 5> First, indium tin oxide containing silicon oxide (ITSO) is deposited on a glass substrate 1100. A film was formed by sputtering to form a first electrode 1101 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm x 2 mm.

[0307] Next, as a pretreatment for forming the light emitting element 5 on the substrate 1100, the substrate surface is washed with water. After cleaning, it was baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0308] Then, 10 -4 The substrate is introduced into a vacuum deposition apparatus whose inside has been reduced in pressure to about Pa. After vacuum baking at 170° C. for 30 minutes in a heating chamber in the deposition apparatus, the substrate 1100 is It was left to cool for about 30 minutes.

[0309] Next, the substrate 1100 is vacuum-steamed so that the surface on which the first electrode 1101 is formed faces downward. In this embodiment, the EL layer 1 was formed by vacuum deposition. 102 comprises a hole injection layer 1111, a hole transport layer 1112, a light emitting layer 1113, and an electron transport A case where the layer 1114 and the electron injection layer 1115 are formed in this order will be described.

[0310] 10 minutes inside the vacuum chamber -4 After depressurizing to 100 Pa, 1,3,5-tri(dibenzothiophene-4 -yl)-benzene (abbreviation: DBT3P-II) and molybdenum(VI) oxide were 3P-II (abbreviation): molybdenum oxide = 4:2 (mass ratio) Thus, a hole injection layer 1111 was formed on the first electrode 1101. The film thickness was set to 20 nm. Co-evaporation is a method of simultaneously evaporating multiple different substances from different evaporation sources. It is law.

[0311] Next, 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine A hole transport layer 1112 is formed by depositing 20 nm of BPAFLP. Ta.

[0312] Next, the light-emitting layer 1113 was formed on the hole-transporting layer 1112. [4-phenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), N-(1,1'-biphenyl-4-yl)-N-[4- (9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H -Fluoren-2-amine (abbreviation: PCBBiF), (acetylacetonato)bis(4, 6-Diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm)2(a cac)]) was added to 2mDBTBPDBq-II (abbreviation): PCBBiF (abbreviation): [Ir (dppm)2(acac)] (abbreviation) = 0.7:0.3:0.05 (mass ratio) The first light-emitting layer 1113a was formed to a thickness of 20 nm by co-evaporation, and then 2mDBTBPD Bq-II (abbreviation): PCBBiF (abbreviation): [Ir(dppm)2(acac)] (abbreviation) The second light-emitting layer 111 was formed by co-evaporation so that the mass ratio of the first light-emitting layer 111 was 0.8:0.2:0.05. By forming the layer 3b to a thickness of 20 nm, a light emitting layer 1113 having a laminated structure was formed.

[0313] Next, 2mDBTBPDBq-II (abbreviation) was evaporated onto the light-emitting layer 1113 to a thickness of 20 nm. Electron transport was achieved by depositing 20 nm of bathophenanthroline (abbreviation: Bphen). A layer 1114 was formed. Furthermore, lithium fluoride was evaporated to a thickness of 1 nm on the electron transport layer 1114. In this way, an electron injection layer 1115 was formed.

[0314] Finally, aluminum was evaporated onto the electron injection layer 1115 to a thickness of 200 nm. Then, a second electrode 1103 serving as a cathode was formed, and a light-emitting element 5 was obtained. In all the depositions, a resistance heating method was used.

[0315] The element structure of the thus obtained Light-emitting element 5 is shown in Table 9.

[0316] [Table 9]

[0317] The fabricated light-emitting element 5 was placed in a glove box with a nitrogen atmosphere to prevent it from being exposed to the air. (Sealing material was applied around the element, and heat treatment was performed at 80°C for 1 hour during sealing.) ).

[0318] <Operation characteristics of light-emitting element 5> The operating characteristics of the fabricated light-emitting element 5 were measured. The measurements were performed at room temperature (25° C.). The atmosphere was very friendly.

[0319] First, current density-luminance characteristics of the light-emitting element 5 are shown in FIG. is the luminance (cd / m 2 ), the horizontal axis is the current density (mA / cm 2 ) is shown. Also, the light-emitting element 5 Voltage-luminance characteristics are shown in FIG. 37. In FIG. 37, the vertical axis represents luminance (cd / m 2 ), The horizontal axis represents voltage (V). FIG. 38 shows the luminance vs. current efficiency characteristics of the light-emitting element 5. In FIG. 38, the vertical axis is current efficiency (cd / A) and the horizontal axis is luminance (cd / m 2 ) FIG. 39 shows the voltage-current characteristics of the light-emitting element 5. In FIG. 39, the vertical axis , current (mA), and the horizontal axis indicates voltage (V).

[0320] FIG. 38 shows that the light-emitting element 5 of one embodiment of the present invention is a highly efficient element. Also, 1000cd / m 2 The main initial characteristics of the light-emitting element 5 in the vicinity are shown in Table 10 below. show.

[0321] [Table 10]

[0322] From the above results, the light-emitting device 5 produced in this example exhibits high external quantum efficiency. It can be seen that the luminous efficiency is high. Furthermore, in terms of color purity, it emits orange light with good purity. It is clear that this is the case.

[0323] In addition, the light emitting element 5 is supplied with 25 mA / cm 2 The emission spectrum when a current is applied at a current density of 40. As shown in FIG. 40, the emission spectrum of the light-emitting element 5 has a peak at about 583 nm. The phosphorescent organometallic iridium complex [Ir(dppm)2(acac)] This suggests that this is due to the emission of

[0324] The results of the reliability test on the light-emitting element 5 are shown in FIG. indicates the normalized luminance (%) when the initial luminance is 100%, and the horizontal axis indicates the driving time of the element (h). The reliability test was performed with an initial brightness of 5000cd / m 2 and the current density is constant. As a result, the luminance of the light-emitting element 5 after 1980 hours was It retained about 92% of its brightness.

[0325] Therefore, the light-emitting element 5 is found to be a highly reliable and long-life light-emitting element. Ta.

[0326] In addition, 2mDBTBPDBq-II (abbreviation), PCBBiF (abbreviation), and 2mDBT A mixed film of BPDBq-II (abbreviation) and PCBBiF (abbreviation) was prepared, and each film Photoluminescence (PL) was measured. As a result, 2mDBTBPDBq-II (abbreviation The photoluminescence (PL) peak wavelength of the evaporated film of PCBBi is 428 nm. The PL peak wavelengths of the evaporated films of F (abbreviation) are 415 nm and 436 nm, whereas The PL peak wavelength of the co-deposited mixed film was 512 nm, which was a large shift to longer wavelengths. Therefore, 2mDBTBPDBq-II (abbreviation) and PCBBiF (abbreviation) are exciplexes. It was found that the combination formed EXAMPLES

[0327] In this example, a light-emitting element 6 which is one embodiment of the present invention will be described with reference to FIG. The chemical formulas of the materials used in this embodiment are shown below.

[0328] [ka]

[0329] <Fabrication of light-emitting element 6> First, indium tin oxide containing silicon oxide (ITSO) is deposited on a glass substrate 1100. A film was formed by sputtering to form a first electrode 1101 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm x 2 mm.

[0330] Next, as a pretreatment for forming the light emitting element 6 on the substrate 1100, the substrate surface is washed with water. After cleaning, it was baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0331] Then, 10 -4 The substrate is introduced into a vacuum deposition apparatus whose inside has been reduced in pressure to about Pa. After vacuum baking at 170° C. for 30 minutes in a heating chamber in the deposition apparatus, the substrate 1100 is It was left to cool for about 30 minutes.

[0332] Next, the substrate 1100 is vacuum-steamed so that the surface on which the first electrode 1101 is formed faces downward. In this embodiment, the EL layer 1 was formed by vacuum deposition. 102 comprises a hole injection layer 1111, a hole transport layer 1112, a light emitting layer 1113, and an electron transport A case where the layer 1114 and the electron injection layer 1115 are formed in this order will be described.

[0333] 10 minutes inside the vacuum chamber -4 After depressurizing to 100 Pa, 1,3,5-tri(dibenzothiophene-4 -yl)-benzene (abbreviation: DBT3P-II) and molybdenum(VI) oxide were 3P-II (abbreviation): molybdenum oxide = 4:2 (mass ratio) Thus, a hole injection layer 1111 was formed on the first electrode 1101. The film thickness was set to 20 nm. Co-evaporation is a method of simultaneously evaporating multiple different substances from different evaporation sources. It is law.

[0334] Next, 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine A hole transport layer 1112 is formed by depositing 20 nm of BPAFLP. Ta.

[0335] Next, the light-emitting layer 1113 was formed on the hole-transporting layer 1112. (phenyldibenzothiophene-4-yl)phenyl]phenyl}dibenzo[f,h]kinoki Sarin (abbreviation: 2mDBTBPDBq-IV), N-(1,1'-biphenyl-4-yl) )-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9- Dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), (acetylacetonate Bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(d ppm)2(acac)]) was added to 2mDBTBPDBq-IV (abbreviation): PCBBiF ( Abbreviation): [Ir(dppm)2(acac)] (Abbreviation) = 0.7:0.3:0.05 (quality The first light-emitting layer 1113a is formed to a thickness of 20 nm, and then the second mDBTBPDBq-IV (abbreviation): PCBBiF (abbreviation): [Ir(dppm)2(a cac)] (abbreviation) = 0.8:0.2:0.05 (mass ratio), and the second The light emitting layer 1113b is formed to a thickness of 20 nm to form a light emitting layer 1113 having a laminated structure. was formed.

[0336] Next, 2mDBTBPDBq-IV (abbreviation) was evaporated to a thickness of 20 nm on the light-emitting layer 1113. Electron transport was achieved by depositing 20 nm of bathophenanthroline (abbreviation: Bphen). A layer 1114 was formed. Furthermore, lithium fluoride was evaporated to a thickness of 1 nm on the electron transport layer 1114. In this way, an electron injection layer 1115 was formed.

[0337] Finally, aluminum was evaporated onto the electron injection layer 1115 to a thickness of 200 nm. Then, a second electrode 1103 serving as a cathode was formed, and a light-emitting element 6 was obtained. In all the depositions, a resistance heating method was used.

[0338] The element structure of the thus obtained Light-emitting Element 6 is shown in Table 11.

[0339] [Table 11]

[0340] The fabricated light-emitting device 6 was placed in a glove box with a nitrogen atmosphere to prevent exposure to the atmosphere. (Sealing material was applied around the element, and heat treatment was performed at 80°C for 1 hour during sealing.) ).

[0341] <Operation characteristics of light-emitting element 6> The operating characteristics of the fabricated light-emitting element 1 were measured. The measurements were performed at room temperature (25° C.). The atmosphere was very friendly.

[0342] First, the current density-luminance characteristics of the light-emitting element 6 are shown in FIG. is the luminance (cd / m 2 ), the horizontal axis is the current density (mA / cm 2 ) is shown. Also, the light-emitting element 6 The voltage-luminance characteristics are shown in FIG. 43. In FIG. 43, the vertical axis represents luminance (cd / m 2 ), The horizontal axis represents voltage (V). The luminance vs. current efficiency characteristics of the light-emitting element 6 are shown in FIG. In FIG. 44, the vertical axis is current efficiency (cd / A) and the horizontal axis is luminance (cd / m 2 ) FIG. 45 shows the voltage-current characteristics of the light-emitting element 6. In FIG. 45, the vertical axis , current (mA), and the horizontal axis indicates voltage (V).

[0343] As shown in FIG. 44, the light-emitting element 6 of one embodiment of the present invention is a highly efficient element. Also, 1000cd / m 2 The main initial characteristics of the light-emitting element 6 in the vicinity are shown in Table 12 below. show.

[0344] [Table 12]

[0345] From the above results, the light-emitting device 6 fabricated in this example exhibits high external quantum efficiency. It can be seen that the luminous efficiency is high. Furthermore, in terms of color purity, it emits orange light with good purity. It is clear that this is the case.

[0346] In addition, the light emitting element 6 is supplied with 25 mA / cm 2 The emission spectrum when a current is applied at a current density of As shown in FIG. 46, the emission spectrum of the light-emitting element 6 has a peak at about 587 nm. The phosphorescent organometallic iridium complex [Ir(dppm)2(acac)] This suggests that this is due to the emission of

[0347] The results of the reliability test on the light-emitting element 6 are shown in FIG. indicates the normalized luminance (%) when the initial luminance is 100%, and the horizontal axis indicates the driving time of the element (h). The reliability test was performed with an initial brightness of 5000cd / m 2 and the current density is constant. As a result, the luminance of the light-emitting element 6 after 833 hours was It maintained about 91% of its original viscosity.

[0348] Therefore, it was found that the light-emitting element 6 is a highly reliable light-emitting element with a long life. Ta. [Explanation of symbols]

[0349] 101 Anode 102 Cathode 103 EL layer 104 Hole injection layer 105 Hole transport layer 106 Light-emitting layer 106a First light-emitting layer 106b Second light-emitting layer 107 Electron transport layer 108 Electron injection layer 109 Phosphorescent compounds 110 The first organic compound 111 Second organic compound 201 First electrode (anode) 202 Second electrode (cathode) 203 EL layer 204 Hole injection layer 205 Hole transport layer 206 Light-emitting layer 206a First light-emitting layer 206b Second light-emitting layer 207 Electron transport layer 208 Electron injection layer 301 First electrode 302(1) First EL layer 302(2) Second EL layer 304 Second electrode 305 Charge generation layer (I) 305(1) First charge generating layer (I) 305(2) Second charge generating layer (I) 401 Reflecting electrode 402 Semi-transparent / semi-reflective electrode 403a First transparent conductive layer 403b Second transparent conductive layer 404B First light-emitting layer (B) 404G Second light-emitting layer (G) 404R Third light-emitting layer (R) 405 EL layer 410R First light emitting element (R) 410G Second light-emitting element (G) 410B Third light-emitting element (B) 501 Element substrate 502 Pixel section 503 Driver circuit section (source line driver circuit) 504a, 504b Drive circuit section (gate line drive circuit) 505 Sealing material 506 Sealing substrate 507 Wiring 508 FPC (Flexible Printed Circuit) 509 n-channel TFT 510 p-channel TFT 511 Switching TFT 512 Current control TFT 513 First electrode (anode) 514 Insulation 515 EL layer 516 Second electrode (cathode) 517 Light emitting element 518 Space 1100 Substrate 1101 First electrode 1102 EL layer 1103 Second electrode 1111 Hole injection layer 1112 Hole transport layer 1113 Light-emitting layer 1114 Electron transport layer 1115 Electron injection layer 3000 boards 3001 First electrode 3002a first EL layer, 3002b second EL layer, 3011a first hole injection layer, 3011b second hole injection layer 3012a first hole transport layer, 3012b second hole transport layer 3013a light-emitting layer (A), 3013b light-emitting layer (B) 3014a first electron transport layer, 3014b second electron transport layer 3015a first electron injection layer, 3015b second electron injection layer 3003 Second electrode 3004 Charge generating layer 7100 Television equipment 7101 Case 7103 Display section 7105 Stand 7107 Display section 7109 Operation key 7110 Remote control device 7201 Main unit 7202 Case 7203 Display section 7204 Keyboard 7205 External connection port 7206 Pointing Device 7301 Case 7302 Case 7303 Connection section 7304 Display section 7305 Display section 7306 Speaker section 7307 Recording medium insertion section 7308 LED Lamp 7309 Operation key 7310 Connection terminal 7311 Sensor 7312 Microphone 7400 Mobile Phone 7401 Case 7402 Display section 7403 Operation button 7404 External connection port 7405 Speaker 7406 Mike 8001 Lighting equipment 8002 Lighting equipment 8003 Lighting equipment 8004 Lighting equipment 9033 Fastener 9034 Display mode change switch 9035 Power Switch 9036 Power saving mode switch 9038 Operation switch 9630 Case 9631 Display section 9631a Display section 9631b Display section 9632a Touch Panel Area 9632b Touch Panel Area 9633 Solar Cells 9634 Charge / discharge control circuit 9635 Battery 9636 DC-DC Converter 9637 Operation key 9638 Converter 9639 Button

Claims

1. A pair of electrodes; A light-emitting layer and a hole transport layer are provided between the pair of electrodes, the light-emitting layer has a laminated structure of a first light-emitting layer and a second light-emitting layer, the first light-emitting layer includes a first iridium complex, a first organic compound, and a second organic compound; the second light-emitting layer includes a second iridium complex, the first organic compound, and the second organic compound; the hole transport layer comprises an aromatic amine compound or a carbazole derivative, the first organic compound is a nitrogen-containing heteroaromatic compound; the second organic compound is a π-excess heteroaromatic compound or an aromatic amine compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the peak of the emission spectrum of the first iridium complex is at a shorter wavelength than the peak of the emission spectrum of the second iridium complex; a difference between the energy value of a peak in the emission spectrum of the exciplex and the energy value of a peak in an absorption band located on the longest wavelength side in the absorption spectrum of the first iridium complex is within 0.2 eV.

2. A pair of electrodes; A light-emitting layer and a hole transport layer are provided between the pair of electrodes, the light-emitting layer has a laminated structure of a first light-emitting layer and a second light-emitting layer, the first light-emitting layer includes a first iridium complex, a first organic compound, and a second organic compound; the second light-emitting layer includes a second iridium complex, the first organic compound, and the second organic compound; the hole transport layer comprises an aromatic amine compound or a carbazole derivative, the first organic compound is a nitrogen-containing heteroaromatic compound; the second organic compound is a π-excess heteroaromatic compound or an aromatic amine compound; a peak of an emission spectrum of a mixed film of the first organic compound and the second organic compound has a longer wavelength than a peak of an emission spectrum of a film of the first organic compound; a peak of an emission spectrum of the mixed film is at a longer wavelength than a peak of an emission spectrum of the film of the second organic compound, the peak of the emission spectrum of the first iridium complex is at a shorter wavelength than the peak of the emission spectrum of the second iridium complex; a difference between the energy value of the peak of the emission spectrum of the mixed film and the energy value of the peak of the absorption band located on the longest wavelength side of the absorption spectrum of the first iridium complex is within 0.2 eV.

3. In claim 1 or 2, the T1 level of the first organic compound is higher than the T1 level of the first iridium complex; A light-emitting element, wherein the T1 level of the second organic compound is higher than the T1 level of the first iridium complex.

4. In any one of claims 1 to 3, A third light-emitting layer is further provided between the pair of electrodes, The third light-emitting layer comprises a light-emitting material that emits blue light.

5. A light emitting device comprising the light emitting element according to claim 1 .

6. An electronic device comprising the light emitting device according to claim 5.

7. A lighting device comprising the light-emitting device according to claim 5.

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