Light emitting element

Abstract

To provide a light-emitting device having high external quantum efficiency and long service life.SOLUTION: A light-emitting device includes a light-emitting layer 106 provided between a positive electrode and a negative electrode. The light-emitting layer is made by stacking a first light-emitting layer 106b that at least contains a first luminescent substance 109a converting triplet excitation energy into light emission, a first organic compound 110 having an electron transport property, and a second organic compound 111 having a hole transport property and provided on the positive electrode side, and a second light-emitting layer that at least contains a second light-emitting substance 109b converting triplet excitation energy int light emission, a first organic compound 110, and a third organic compound 112 having a hole transport property. The second organic compound has a lower HOMO level than the third organic compound. The first light-emitting substance exhibits light emission of a shorter wavelength than the second luminescent substance. A combination of the first organic compound and the second organic compound and a combination of the first organic compound and the third organic compound each form an excited complex.SELECTED DRAWING: Figure 1

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 (anode and cathode), and the light-emitting layer is a triple layer. A first light-emitting substance (guest material) that converts excitation energy into light emission and has electron transport properties A first organic compound (host material) and a second organic compound (assist material) having hole transport properties are A first light-emitting layer including at least a triplet excitation material and formed on the anode side; The second luminescent material (guest material) that converts the energy into light emission, the first organic compound with electron transport properties and a third organic compound (assist material) having hole transport properties. The first light-emitting layer has a laminated structure with at least one second light-emitting layer formed thereon, and the first light-emitting layer has a first The organic compound (host material) and the second organic compound (assist material) form an exciplex. The second emitting layer is a combination of a first organic compound (host material) and a third organic compound. and an assist material that forms an exciplex. It is an element.

[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 light-emitting substance that converts energy into light emission, a first organic compound having an electron transport property, and and a second organic compound having hole transport properties, and is in contact with the hole transport layer. The first light-emitting layer is made of a material having a triplet excitation energy, and the second light-emitting material converts the triplet excitation energy into light emission. A first organic compound having a hole transport property and a third organic compound having a hole transport property are mixed at least and a second light-emitting layer formed in contact with the electron transport layer. In the optical layer, the first organic compound (host material) and the second organic compound (assist material) are The combination forms an exciplex, and the second light-emitting layer is a first organic compound (host material The first organic compound (assist material) and the third organic compound (assist material) are a combination that forms an exciplex. The light-emitting device is characterized by the above.

[0010] In each of the above structures, the first organic compound (host material) of the first light-emitting layer and the second The emission wavelength of the exciplex formed by the organic compound (assist material) is The emission wavelengths (fluorescence wavelengths) of the first organic compound (host material) and the second organic compound (assist material) Since it exists on the longer wavelength side compared to The fluorescence spectrum of the first organic compound (host material) and the fluorescence spectrum of the second organic compound (assist material) The second tor can be converted to a longer wavelength emission spectrum. The light-emitting layer is made up of the first organic compound (host material) and the third organic compound (assist material). The emission wavelength of the formed exciplex is determined by the composition of the first organic compound (host material) and the third organic compound ( The wavelengths are longer than the emission wavelengths (fluorescence wavelengths) of the assist materials. By forming an exciplex from the first organic compound (host material), The fluorescence spectrum of the third organic compound (assist material) is It can be converted into a spectrum.

[0011] In each of the above structures, the first light-emitting layer contains an anion of the first organic compound and an anion of the second organic compound. In the second emitting layer, an exciplex is formed from the cation of the organic compound of The anion and the cation of the third organic compound form an exciplex. .

[0012] In the above-mentioned configuration, the first light-emitting layer and the second light-emitting layer are each made of the same first organic compound. The first light-emitting layer includes a second organic compound (host material) and an assist material (assist material). The third organic compound (assist material) contained in the second light-emitting layer has a higher highest occupied molecular orbital (HOM) than the third organic compound (assist material) contained in the second light-emitting layer. It is characterized by its low HOMO level.

[0013] In the above structure, the first light-emitting substance contained in the first light-emitting layer is a second light-emitting substance. The layer is characterized in that it is a substance that emits light having a shorter wavelength than the second light-emitting substance contained in the layer.

[0014] In the above-mentioned configuration, the first light-emitting substance and the second light-emitting substance are triplet excited energies. These are luminescent substances that convert energy into light. They include phosphorescent compounds such as organometallic complexes and thermally activated Materials that exhibit thermally delayed fluorescence, i.e., thermally activated delayed fluorescence (TADF), The material can be used as a photo-induced delayed fluorescence (PDF). The first organic compound is mainly composed of 10 -6 cm 2 / Vs or higher electron mobility The electron transporting material is, specifically, a π-deficient heteroaromatic compound, and the second organic compound and and the third organic compound is mainly 10 -6 cm 2 Holes with hole mobility of / Vs or more A transport material, specifically a π-excess heteroaromatic compound or an aromatic amine compound. It is characterized by:

[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 Module, a module with a printed wiring board at the end of 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 includes a first light-emitting layer and a second light-emitting layer. Since exciplexes can be formed in each layer, the energy transfer efficiency is high. As a result, a light-emitting device with high external quantum efficiency can be realized.

[0017] In addition, in the light-emitting element which is one embodiment of the present invention, the above-described element structure can be used. The exciplex formed in the first emitting layer has a higher excitation current than the exciplex formed in the second emitting layer. Since the first light-emitting layer has a triplet excitation energy, the triplet excitation energy contained in the first light-emitting layer is emitted. The triplet exciton in the second emitting layer acts as the first luminescent material (guest material) that converts light into A material that emits light with a shorter wavelength than the second luminescent material (guest material) that converts energy into light By using a material such as a fluorine-containing compound, it is possible to obtain light emission from the first light-emitting layer and the second light-emitting layer at the same time. Furthermore, the excitation energy of the exciplex formed in the first light-emitting layer is converted into light-emitting energy. A part of the energy that could not be contributed to the first emission layer is converted to triplet excitation energy in the second emission layer. This can be used as excitation energy for a second luminescent material (guest material) that converts the light into light. Therefore, the light emitting efficiency of the light emitting element can be further improved. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 illustrates a concept of one embodiment of the present invention. [Diagram 2] FIG. 1 illustrates a concept of one embodiment of the present invention. [Diagram 3] FIG. 13 shows calculation results according to one embodiment of the present invention. [Figure 4] FIG. 13 shows calculation results according 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] 1A and 1B are diagrams illustrating a lighting device. [Figure 12] 1A to 1C are diagrams illustrating light-emitting elements. [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. 1 shows an emission spectrum of a substance used in the light-emitting element 1. [Figure 19] FIG. 1 shows an emission spectrum of a substance used in the light-emitting element 1. 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, a luminescent material (such as a phosphorescent compound or a thermally activated delayed General light emission from light-emitting devices using TADF (including fluorescent (TADF) materials) as guest materials Here, the molecule that provides the excitation energy is called the host. The molecule that receives the excitation energy is referred to as 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 reaction is carried out, 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 2is 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 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, kn 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)) needs to be considered. According to equation (2), the rate constant k h*→g To increase the emission spectrum of the host molecule, (Since we are discussing energy transfer from triplet excited states, phosphorescence spectra) and guest molecules The absorption spectrum of (absorption corresponding to the direct transition from the singlet ground state to the triplet excited state) It can be seen that a larger overlap is better.

[0043] In one embodiment of the present invention, a light-emitting substance (phosphorescent compound) that converts triplet excitation energy into light emission is and thermally activated delayed fluorescence (TADF) materials) as guest materials, while phosphorescent compounds In the absorption spectrum of a substance, this corresponds to a direct transition from the singlet ground state to the triplet excited state. In some cases, absorption due to the emission of light is observed, which is the absorption band that appears on the longest wavelength side. In the case of iridium complexes with cations, the absorption band at the longest wavelength is broad around 500 to 600 nm. In many cases, these appear as absorption bands (of course, depending on the emission wavelength, they may appear on the shorter or longer wavelength side). This absorption band is mainly due to the triplet MLCT (Metal t o Ligand Charge Transfer (LCT) transition. The band also contains some absorption due to triplet π-π* transitions and singlet MLCT transitions. It is thought that these two overlap to form a broad absorption band on the longest wavelength side of the absorption spectrum. In other words, the difference between the lowest singlet excited state and the lowest triplet excited state is small, and the The absorption of these two substances overlap, forming a broad absorption band at the longest wavelength side of the absorption spectrum. Therefore, we used organometallic complexes (especially iridium complexes) as guest materials. When the phosphorescence of the host material is The large overlap of the spectra leads to a rate constant k h*→g Increase the energy transfer Efficiency can be improved.

[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. In this case, the Dexter type (formula ( 2) is prohibited, 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 The higher the φ (fluorescence quantum yield, since we are discussing energy transfer from the singlet excited state), the better. However, in reality, a more important factor is the emission spectrum of the host molecule. Toll (fluorescence spectrum since we are discussing energy transfer from singlet excited states) and guest Absorption spectrum of a molecule (absorption corresponding to a direct transition from the singlet ground state to the triplet excited state) ) and the molar absorption coefficient of the guest molecule should be high. This is because the fluorescence spectrum of the host material and the phosphorescent compound This means that the absorption band appearing on the longest wavelength side of

[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 including the light-emitting layer is sandwiched between the electrodes (anode and cathode). The first light-emitting substance (guest material) converts excitation energy into light emission, and the second light-emitting substance (guest material) has electron transport properties. The organic compound (host material) of 1 and the organic compound (assist material) having hole transport properties are A first light-emitting layer including at least a triplet excitation energy material and formed on the anode side; The second luminescent material (guest material) converts the photo-induced light into light, and the first organic compound has electron transport properties. A small amount of a third organic compound (assist material) having hole transport properties is added to the first organic compound (host material). The second light-emitting layer has a laminated structure including at least one of the first light-emitting layer and the second light-emitting layer.

[0052] The second organic compound (assist material) contained in the first light-emitting layer is The HOMO level is lower than that of the third organic compound (assist material). The excitation energy (E A ) as the second emitting layer The excitation energy (E B ) It is possible.

[0053] The first light-emitting material contained in the first light-emitting layer is a second light-emitting material contained in the second light-emitting layer. It is assumed that the substance exhibits light emission at a shorter wavelength than the optically active substance.

[0054] First, the structure of a light-emitting element, which is an example of the present invention, will be described with reference to FIG.

[0055] 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.

[0056] In addition, the light-emitting layer 106 according to one embodiment of the present invention has a triplet excited electron as shown in FIG. A first light-emitting substance (guest material) 109a that converts energy into light emission, A first organic compound (host material) 110 and a second organic compound ( A first light-emitting layer 106a including at least an assist material 111 and formed on the anode side. and a second luminescent material (guest material) 109b that converts triplet excitation energy into luminescence. A first organic compound (host material) 110 having electron transport properties and a second organic compound (host material) 111 having hole transport properties. The second light-emitting layer 10 is formed by containing at least the organic compound (assist material) 112 of the third embodiment. The first organic compound 110 is mainly composed of 10 -6 cm 2 The second organic compound 111 and the electron transporting material having an electron mobility of 111 or more are used. The third organic compound 112 is mainly 10 -6 cm 2 / Vs or more hole mobility In this specification, a hole transporting material having the first property is used. The organic compound 110 is called a host material, and the second organic compound 111 and the third organic compound 112 are called a host material. 12 is called the assist material.

[0057] In addition, the first organic compound (host material) 110 and the second organic compound (host material) in the first light-emitting layer 106a The combination of the organic compound (assist material) 111 results in an exciplex (exciplex). The combination is characterized by forming a cyclohexyl ether (also called a cyclohexyl ether plex). The first organic compound (host material) 110 and the second organic compound (assist material) 111 The emission wavelength of the formed exciplex is determined by the wavelength of the first organic compound (host material) 110 and the wavelength of the second organic compound (host material) 111. The emission wavelength (fluorescence wavelength) of the compound (assist material) 111 is longer than that of the compound (assist material) 111. Since the first organic compound (host material) 110 and the second organic compound (host material) 120 are present, The fluorescence spectrum of the organic compound (assist material) 111 is on the longer wavelength side. can be converted to torr.

[0058] The same applies to the second light-emitting layer 106b. In 6b, the first organic compound (host material) 110 and the third organic compound (assist material The combination with 112 is called an exciplex. ) is formed. Furthermore, the first organic compound (host material Luminescence from an exciplex formed by an organic compound (assist material) 110 and a third organic compound (assist material) 112 The wavelength is the wavelength of the first organic compound (host material) 110 and the third organic compound (assist material) 1 Since it is on the longer wavelength side compared to the emission wavelength (fluorescence wavelength) of each of 12, the first The fluorescence spectrum of the organic compound (host material) 110 and the third organic compound (assist material) ) The fluorescence spectrum of 112 can be converted to a longer wavelength emission spectrum. can.

[0059] 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 T1 level of the first luminescent material (guest material) 109a that converts the doublet excitation energy into luminescence It is preferable that the first organic compound 110 (or the second organic compound 111) has a higher If the T1 level is lower than the T1 level of the first light-emitting substance (guest material) 109a, the light emission is The triplet excitation energy of the first light-emitting substance (guest material) 109a is converted to a 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.

[0060] Similarly, the first organic compound (host material) 110 and the third organic compound (assist The triplet excitation energy levels (T1 levels) of each of the materials 112 are The T1 level of the second luminescent material (guest material) 109b, which converts energy into light, is higher than the T1 level of the second luminescent material (guest material) 109b. It is preferable that the T1 level of the first organic compound 110 (or the third organic compound 112) is If the T1 level of the second light-emitting material (guest material) 109b is lower than the T1 level of the second light-emitting material (guest material) 109b, the second The triplet excitation energy of the light-emitting substance (guest material) 109b is converted into a triplet excitation energy of the first organic compound 110 ( Or the third organic compound 112) causes quenching, resulting in a decrease in luminous efficiency. This is the case.

[0061] In the first light-emitting layer 106a constituting the light-emitting layer 106, the first organic compound ( the ratio of the first organic compound (assist material) 110 and the second organic compound (assist material) 111; In the second light-emitting layer 106b constituting the light-emitting layer 106, the first organic compound (host material What is the ratio of the third organic compound (assist material) 110 and the third organic compound (assist material) 112? Either case may be more common, and the present invention includes both cases.

[0062] The light-emitting layer 106 (first light-emitting layer 106a and second light-emitting layer 106b) having the above structure In the above, the first organic compound (host material) 110 and the second organic compound (assist material) 111 and the third organic compound (assist material) 112. is shown in Figure 1(B).

[0063] As shown in FIG. 1B, in the first light-emitting layer 106a, a first organic compound (host material The excitation of the exciplex formed by the first organic compound (assist material) 110 and the second organic compound (assist material) 111 is Electromotive energy (E A ) is the HOMO level of the second organic compound (assist material) 111, It is determined by the LUMO level of the first organic compound (host material) 110. In the optical layer 106b, a first organic compound (host material) 110 and a third organic compound (a The excitation energy (E B ) is the third The HOMO level of the first organic compound (assist material) 112 and the HOMO level of the second organic compound (host material) 1 The LUMO level of the second organic compound contained in the first light-emitting layer 106a is determined by the LUMO level of the second organic compound. The compound (assist material) 111 is a third organic compound ( Since the HOMO level of the first light-emitting layer 106a is lower than that of the assist material 112, The excitation energy (E A ) is formed in the second light-emitting layer 106b. The excitation energy (E B ) can be designed to be larger than .

[0064] In addition, by using the above-mentioned device structure, an exciplex is formed in the first light-emitting layer 106a. has a higher excitation energy than the exciplex formed in the second light-emitting layer 106b. Therefore, the first light-emitting layer 106a converts the triplet excitation energy into light emission. The light-emitting material (guest material) 109a is a triplet excited lanthanide (TEN) contained in the second light-emitting layer 106b. The second luminescent material (guest material) 109b converts photoinduced energy into luminescence. By using a material that shows light, the first light-emitting layer 106a and the second light-emitting layer 10 Furthermore, light emission from the first light-emitting layer 106a can be obtained. A part of the excitation energy of the exciplex that could not contribute to the emission is converted into a second emission energy. A second luminescent material (guest material) that converts triplet excitation energy in the optical layer 106b into luminescence. Since the photocatalyst 109b can be used as excitation energy for the photocatalyst 109b, the photocatalyst 109b can be used as excitation energy for the photocatalyst 109b. The light efficiency can be further improved.

[0065] The light-emitting element described in this embodiment has a light-emitting layer 106 (a first light-emitting layer 106a, a second light-emitting layer 106b, a In the photoluminescence layer 106b), each of the organic compounds forms an exciplex. The fluorescence spectrum of the (host material) 110 and the fluorescence spectrum of the second organic compound (assist material) 111 The light spectrum or the fluorescence spectrum of the third organic compound (assist material) 112 is The fact that the emission spectrum can be converted to a longer wavelength region is shown in Figure 2. Thus, the first organic compound 110, the second organic compound 111, or the third organic compound 11 Even if the fluorescence spectrum of 2 is similar to that of the luminescent material 109 ( The first light-emitting material (guest material) 109a and the second light-emitting material (guest material) 10 9b), which is located on the shorter wavelength side compared to the absorption band located on the longest wavelength side, and triplet excitation energy a light-emitting material 109 (a first light-emitting material (guest material) 109a) that converts the light into light; Overlap with the absorption band located on the longest wavelength side of the second light-emitting substance (guest material) 109b) This means that even if there is no exciplex, the overlap can be increased by forming an exciplex. This makes it possible to improve the energy transfer efficiency in the above formula (2-2B). Cut.

[0066] 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 the complex (generally the emission spectrum from the singlet state of the exciplex) is The absorption band of the luminescent material 109, which converts excitation energy into luminescence, is located at the longest wavelength side. When the device is designed to be heated, the emission spectrum from the triplet state of the exciplex (which is not observed at room temperature) The luminescence that converts triplet excitation energy into light emission (usually not observed even at low temperatures) This overlaps with the absorption band located at the longest wavelength side of the substance 109. Not only the energy transfer from the excited triplet state ((2-2)), but also the energy transfer from the excited triplet state The efficiency of the photoelectron transfer ((2-1)) is also increased, resulting in the transfer of energy from both the singlet and triplet excited states. It can efficiently convert energy into light.

[0067] 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, a representative skeleton that constitutes the LUMO levels of aromatic compounds (abbreviation: DBq) was used to prepare the second organic compound 111 (or the As a model of the organic compound 312), we have a representative structure that constitutes the HOMO level of aromatic amines. The calculation was performed by combining the skeleton triphenylamine (abbreviation: TPA) and .

[0068] 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

[0069] 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.

[0070] 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. .

[0071] With the above-mentioned basis functions, for example, in the case of a hydrogen atom, the 1s to 3s orbitals 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.

[0072] The quantum chemical calculation program used was Gaussian 09. The experiment was carried out using a high-performance computer (SGI, Altix 4700). .

[0073] 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. 3, and the distributions of the HOMO levels and LUMO levels are shown in FIG.

[0074] Figure 4(A1) shows the distribution of the LUMO levels of one molecule of DBq (abbreviation), and Figure 4(A2) shows the , DBq (abbreviation) single molecule distribution, and TPA (abbreviation) The distribution of the LUMO levels of one molecule of TPA (abbreviation) is shown in Figure 4 (B2). The distribution of HOMO levels is shown in Figure 4(C1), which shows the distribution of HOMO levels for the dimers DBq (abbreviation) and TPA (abbreviation). The distribution of the LUMO levels of the dimers DBq (abbreviation) and TPA (abbreviation) is shown in Figure 4(C2). The distribution of HOMO levels of the molecule is shown.

[0075] As shown in Figure 3, 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 (abbreviation) (- 5.21 eV) to form an exciplex of DBq (abbreviation) and TPA (abbreviation). As can be seen in Figure 4, the dimer of DBq (abbreviation) and TPA (abbreviation) The LUMO level of is distributed on the DBq (abbreviation) side, and the HOMO level of is distributed on the TPA (abbreviation) side. .

[0076] 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.

[0077] 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.

[0078] 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 wavelengths of fluorescence and phosphorescence emitted by the dimers at the DBq and TPA levels, respectively. The excitation energy of the S1 level of the dimer of (abbreviation) and TPA (abbreviation) is 2.036 eV. The fluorescence wavelength was 609.1 nm. The excitation energy of the T1 level of the mer is 2.030 eV, and the phosphorescence wavelength is 610.0 nm. It was m.

[0079] 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.

[0080] 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 TPA (abbreviation). The difference between the fluorescence and phosphorescence wavelengths of the dimers of DBq (abbreviation) and TPA (abbreviation) is only 0.9n m, and it can be seen that they are almost the same wavelength.

[0081] From this result, the singlet excitation energy and triplet excitation energy of the exciplex are almost the same. Therefore, as mentioned above, an exciplex has a singlet state, and triplet states, converting triplet excitation energy into light emission (see above). The guest material includes a first luminescent material and a second luminescent material. It was suggested that it could be moved.

[0082] In this manner, the light-emitting element of one embodiment of the present invention has an exciplex formed in the light-emitting layer. The emission spectrum and the luminescent material that converts triplet excitation energy into luminescence (the first luminescence The absorption spectrum of the first light-emitting material is overlapped with that of the second light-emitting material (guest material including the first light-emitting material and the second light-emitting 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.

[0083] In addition, since exciplexes exist only in excited states, there is no ground state that can absorb energy. Therefore, a luminescent material (guest material) that converts triplet excitation energy into luminescence is required. The triplet excited state is generated by energy transfer from the singlet excited state and triplet excited state of The luminescent material (guest material) that converts energy into light is deactivated before emitting light (i.e. This phenomenon, which reduces the luminous efficiency, is not considered to occur in principle. This is one of the factors that can increase child efficiency.

[0084] 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.

[0085] 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.

[0086] Therefore, in this embodiment, the first organic compound (host material) 110 and the second organic compound The HOMO levels of the first organic compound (assist material) 111 and the second organic compound (assist material) 112 The LUMO levels of the first and second fluorine atoms are different from each other as shown in FIG. The HOMO level of the organic compound 110 is less than the HOMO level of the second organic compound 111 and the HOMO level of the third organic compound 112. HOMO level of organic compound 112 < LUMO level of first organic compound 110 < LUMO level of second organic compound The LUMO levels of the organic compound 111 and the third organic compound 112 are then The energy levels are different.

[0087] In each light-emitting layer, two organic compounds (the first light-emitting layer 106a and the second light-emitting layer 106b) are used. In the first organic compound 110 and the second organic compound 111, the second light-emitting layer 106b When an exciplex is formed by the first organic compound 110 and the third organic compound 112), The LUMO levels of the exciplexes in the first light-emitting layer 106a and the second light-emitting layer 106b are The first light-emitting layer 106a is formed of an exciplex derived from the organic compound (host material) 110. The HOMO level of the second organic compound (assist material) 111 is derived from the second light-emitting layer 1 The HOMO level of the exciplex in 06b is the same as that of the third organic compound (assist material) 112. Therefore, the excited electrons of the exciplex in the first light-emitting layer 106a Energy (E A ) is the excitation energy (E B ) That is, the triplet excitation energy contained in the first light-emitting layer is converted into light emission. The first light-emitting substance 109a that can absorb triplet excitation energy contained in the second light-emitting layer is By using a substance that emits light with a shorter wavelength than the second light-emitting substance 109b that converts the light into light, It is possible to form a light-emitting element with high light efficiency. It can emit light efficiently at times.

[0088] In one embodiment of the present invention, the formation process of an exciplex can be considered to be the following two processes. do.

[0089] The first formation process is the reaction of a second organic compound (assist material) and a third organic compound (assist The electrons in the electron-excitation complex form an excited complex from a state in which the electrons in the electron-excitation complex have carriers (specifically, cations). It is a process of development.

[0090] 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.

[0091] However, in one aspect of the present invention, a first organic compound (host material) and a second organic The compound (or the third organic compound) (assist material) has a carrier (cation or anion) to form an exciplex, In other words, it is possible to suppress the formation of singlet excitons without forming singlet excitons. There may be a process of forming a junction exciplex, which results in the quenching of the singlet excitation energy. Therefore, a light emitting element having a long life can be realized.

[0092] For example, the first organic compound is an electron transporting material that easily captures electrons (carriers). It is an electron trapping compound with a deep LUMO level and a high electron trapping property. A material (or a third organic compound) that captures holes (carriers) in a hole-transporting material In the case of a hole-trapping compound that has a tendency to easily , the anion of the first organic compound and the cation of the second organic compound (or the third organic compound) The exciplex formed in this process is This is specifically called electroplex. In this way, the generation of a singlet excited state of the first organic compound (host material) is suppressed, and the electron The triplet excitation energy is converted into light-emitting material (guest material) that emits light. By performing the energy transfer, a light emitting device with high light emitting efficiency can be obtained. The occurrence of triplet excited states in the organic compound (host material) is also suppressed, and direct exciplexes are formed. The triplet excitation energy is converted from the exciplex into light-emitting material (guest It is believed that energy is transferred to the material.

[0093] The second formation process involves the reaction of a first organic compound (host material) with a second organic compound (assist Either the first organic compound (the first material) or the third organic compound (the assist material) forms singlet excitons. Then, the electron in the ground state interacts with another electron in the ground state to form an exciplex. Unlike the conventional photocatalytic ... (assist material), or a third organic compound (assist material) generates a singlet excited state. However, this is quickly converted to an exciplex, so the singlet excitation energy is still Therefore, the first organic compound (host material) and the second organic compound (host material) can be effectively used. The organic compound (assist material) or the third organic compound (assist material) generates the excitation energy In this case, the triplet excited state of the host material can be prevented from being deactivated. Similarly, the triplet excitation energy is rapidly converted to an exciplex, and the triplet excitation energy is converted to light emission from the exciplex. It is believed that the energy is transferred to a luminescent substance (guest material) that can emit light.

[0094] The first organic compound (host material) is an electron trapping compound, while the second The organic compound (or the third organic compound) (assist material) is a hole trapping compound. In the case where the difference between the HOMO level and the LUMO level of these compounds is large (specifically The difference between the first and second organic compounds is 0.3 eV or more, and the electrons selectively enter the first organic compound (host material) and The hole selectively enters the second organic compound (or the third organic compound) (assist material). In this case, the formation of an exciplex occurs via an electroplex rather than via a singlet exciton. It is thought that the process of formation of

[0095] In addition, the emission spectrum of the exciplex and the luminescent material ( In order to overlap the absorption spectrum of the guest material sufficiently, the energy of the emission spectrum peak must be The energy value of the absorption band on the lowest energy side of the absorption spectrum The difference is preferably within 0.3 eV, more preferably within 0.2 eV, and most preferably within 0.5 eV. A value within 0.1 eV is preferable.

[0096] In the light-emitting element of one embodiment of the present invention, the excitation energy of the exciplex is a triplet excitation. The energy is transferred sufficiently to the luminescent material (guest material) that converts the photoinduced energy into light, resulting in excitation. It is preferable that substantially no light emission from the complex is observed. The triplet excited energy is transferred to a luminescent material that converts the triplet excited energy into light. It is preferable that the luminescent material that converts energy into light emits light. Phosphorescent compounds (organic metal complexes, etc.) and thermally activated Preferably, the material is a TADF material or the like.

[0097] In the first light-emitting layer 106a of the light-emitting element according to one embodiment of the present invention, When a light-emitting substance that converts triplet excitation energy into light emission is used as the compound (host material), The organic compound (host material) itself becomes more luminous, converting triplet excitation energy into light emission. In this case, the energy is hardly transferred to the light-emitting material (guest material) that is adjacent to the first organic layer. Although it would be fine if the compound could emit light efficiently, the host material has a problem of concentration quenching, so It is difficult to achieve high luminous efficiency. Therefore, At least one of the second organic compound (or the third organic compound) (assist material) is fluorescent. In the case of a compound that is easily deactivated by heat or luminescence from a singlet excited state, Therefore, the first organic compound (host material) and the second organic compound At least one of the (third organic compound) (assist material) is a fluorescent compound. Preferably, the exciplex is used as a medium for energy transfer.

[0098] 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.

[0099] (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.

[0100] 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.

[0101] The light-emitting layer 206 shown in this embodiment is composed of a first light-emitting layer 206a and a second light-emitting layer 206b. The first light-emitting layer 206a of the light-emitting layer 206 has a laminated structure with the triplet The first light-emitting material (guest material) 209a converts excitation energy into light emission, A first organic compound (host material) 210 having a hole transporting property and a second organic compound (host material) having a hole transporting property. The second light-emitting layer 206b contains a compound (assist material) 211, and the second light-emitting layer 206b contains a triplet excited electron A second light-emitting material (guest material) 209b that converts energy into light emission, which has electron transport properties A first organic compound (host material) 210 and a third organic compound ( Assist material) 212 is included.

[0102] The second organic compound (assist material) contained in the first light-emitting layer is The HOMO level is lower than that of the third organic compound (assist material). The excitation energy (E A ) as the second emitting layer The excitation energy (E B ) It is possible.

[0103] In the light-emitting layer 206 (the first light-emitting layer 206a and the second light-emitting layer 206b), In the case of the first light-emitting layer 206a, a first light-emitting material that converts triplet excitation energy into light emission is The substrate 209a is a first organic compound (host material) 210 and a second organic compound (assist material) In the case of the second light-emitting layer 206b, the triplet excitation energy is emitted. The second light-emitting material 209b that converts light into light is mixed with the first organic compound (host material) 210 and By dispersing the luminescent layer 20 in the organic compound (assist material) 212, 6 (the first light-emitting layer 206a and the second light-emitting layer 206b) can be suppressed. In addition, the concentration quenching due to the high concentration of the luminescent material 209 (209a, 209b) is prevented. This can suppress the emission of light and increase the luminous efficiency of the light-emitting element.

[0104] In addition, the first organic compound 210, the second organic compound 211, and the third organic compound 2 The triplet excitation energy levels (T1 levels) of each of the 12 It is preferable that the T1 level is higher than the T1 level of the luminescent material 209 (209a, 209b) that emits light. The first organic compound 210, the second organic compound 211, and the third organic compound 21 The T1 level of 2 converts triplet excitation energy into light emission. If the T1 level is lower than that of 9b), the triplet excitation energy that contributes to emission is converted into emission. The triplet excitation energy of the photoactive substance 209 (209a, 209b) is converted into the first organic compound 21 0 (or the second organic compound 211 or the third organic compound 212) is quenched (quenched) This is because the light will be smeared and the light emission efficiency will decrease.

[0105] In the present embodiment, in the light-emitting layer 206, the first light-emitting layer 206a is connected to both electrodes. Upon recombination of the injected carriers (electrons and holes), the first organic compound 210 and the second organic compound 211 form an exciplex, and a second emission In the layer 206b, an exciplex is formed from the first organic compound 210 and the third organic compound 212. As a result, the fluorescent spectrum of the first organic compound 210 in the first light-emitting layer 206a The fluorescence spectrum of the second organic compound 211 is similar to that of the first organic compound 212, but has a longer wavelength excitation. The emission spectrum of the first emissive complex in the second emissive layer 206b can be converted to the emission spectrum of the first emissive complex in the second emissive layer 206b. The fluorescence spectrum of the organic compound 210 and the fluorescence spectrum of the third organic compound 212 are The emission spectrum of the exciplex can be converted to a longer wavelength side. To maximize the energy transfer from the excited doublet state, the emission spectrum of the exciplex is Absorption spectrum of 209 luminescent materials (guest materials) that convert triplet excitation energy into luminescence In the first light-emitting layer 206a, the first organic compound 210 and the In the second light-emitting layer 206b, the first organic compound 210 and the third organic compound 211 are mixed. In this case, the triplet excited state is selected as the organic compound 212. Regarding the above, it is believed that energy transfer occurs from the exciplex rather than from the host material.

[0106] The light-emitting material 209 (first light-emitting material 20 The second luminescent material 209b) may be a phosphorescent compound (organic metal complex, etc.) or a thermally activated It is preferable that the first organic compound (phosphine oxide) is a thiol-activated delayed fluorescence (TADF) material. It is preferable to use an electron transporting material as the second organic compound (210). The third organic compound (assist material) 211 and the third organic compound (assist material) 212 are It is preferable to use a hole transporting material.

[0107] 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,C 2’ ]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:

[0108] 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 .

[0109] 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.

[0110] However, the above-mentioned luminescent material (guest material) 209 that converts the triplet excitation energy into luminescence is (first light-emitting material 209a, second light-emitting material 209b), a first organic compound (host material) 210, a second organic compound (assist material) 211, and a third organic compound (assist material) 212. The materials that can be used for the cyst material 212 are not limited to the following: The combination is capable of forming an exciplex, and the emission spectrum of the exciplex is a triplet excited energy. A luminescent material (guest material) 209 (first luminescent material 209a) that converts energy into luminescence or the second luminescent substance 209b), and the emission spectrum of the exciplex overlaps with the absorption spectrum of the second luminescent substance 209b). The peak of the triplet excitation energy is converted into light emission by the luminescent material (guest material) 209 ( The absorption spectrum of the first luminescent material 209a or the second luminescent material 209b is higher than the peak of the absorption spectrum of the first luminescent material 209a or the second luminescent material 209b. Any wavelength longer than that of the light source may be used.

[0111] 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.

[0112] A specific example of manufacturing the light-emitting element described in this embodiment mode will be described below.

[0113] The first electrode (anode) 201 and the second electrode (cathode) 202 are made of a metal, an alloy, an electrically conductive material, or the like. 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] The light-emitting layers 206 (206a, 206b) are as described above. The first light-emitting layer 206a The first light-emitting material 209a, the first organic compound (host material) 210, and the second The second light-emitting layer 206b includes at least an organic compound (assist material) 211. The light-emitting material 209b, the first organic compound (host material) 210, and the third organic compound It is formed having at least the (assist material) 212 .

[0118] 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 2,2'-bipyridine-6,6'-diyl)-co-(2,2'-bipyridine-6,6'-diyl) Polymer compounds such as PF-BPy can also be used. The substances that were found were mainly 10 -6 cm2 / Vs or higher. As long as the substance has a higher electron transporting property than the above, the electron transporting layer 207 can be formed using any substance other than the above. This is also fine.

[0119] 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.

[0120] 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.

[0121] 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. In this case, the organic compound is In particular, the material is preferably one that is excellent in transporting 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.

[0122] 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.

[0123] 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 electrode has the following structure.

[0124] The light-emitting element described in this embodiment has an emission spectrum of an exciplex and triplet excitation energy The energy conversion of the photons into light is achieved by utilizing the overlap of the absorption spectrum with that of the luminescent material (guest material). Energy transfer can increase the efficiency of energy transfer, resulting in emission with high external quantum efficiency. Optical elements can be realized.

[0125] 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 included in the present invention.

[0126] 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.

[0127] 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.

[0128] (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.

[0129] 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).

[0130] 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.

[0131] 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.

[0132] 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. 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] In this embodiment mode, a light-emitting element having two EL layers has been described. As described above, the same can be said for a light-emitting device having n (n is 3 or more) stacked EL layers. As in the light-emitting device according to the present embodiment, a compound semiconductor device is provided between a pair of electrodes. When the device has multiple EL layers, a charge generating layer (I) is disposed between the EL layers, It is possible to emit light in a high brightness range while keeping the current density low. In addition, when applied to lighting, the resistance of the electrode material can be reduced. The voltage drop can be reduced, enabling uniform light emission over a large area. It is possible to realize a light emitting device with high performance and low power consumption.

[0140] 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.

[0141] 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.

[0142] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. There can be.

[0143] (Embodiment 4) In this embodiment, a light-emitting device which is one embodiment of the present invention will be described.

[0144] 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 The light-emitting layer 404 may include a transport layer, an electron injection layer, a charge generation layer (E), etc. (404R, 404G, 404B) are the components of the present invention as described in the first and second embodiments. The light-emitting layer may have the following configuration.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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 m 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).

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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)λG / 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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 for realizing colorization. It can also be combined with a colored layer (color filter). In addition, it is possible to enhance the emission intensity of a specific wavelength in the front direction, resulting in low consumption. This configuration is suitable for color displays using pixels of three or more colors. It is particularly useful when applied to (image display devices), but it may also be used for lighting, etc. .

[0162] (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. .

[0163] 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 light emitting device described in the other embodiment. A light emitting element can be applied.

[0164] In this embodiment mode, an active matrix light emitting device will be described with reference to FIG. .

[0165] 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 .

[0166] 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.

[0167] 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.

[0168] 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, and the driving circuit can be formed externally instead of on the substrate.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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 for the second electrode (cathode) 516 is the same as that shown in Embodiment 2. 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.

[0173] 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. A light emitting device capable of full color display may be formed by combining the light emitting device with a light emitting diode (LED) or the like.

[0174] Furthermore, a sealing substrate 506 is bonded to the element substrate 501 with a sealing material 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. .

[0175] It is preferable to use epoxy resin, low melting point glass, or the like for the sealing material 505. In addition, it is desirable that these materials are as impermeable to moisture and oxygen as possible. The material used for the sealing substrate 506 may be a glass substrate, a quartz substrate, or FRP (Fibre Reinforced Plastics). Glass-Reinforced Plastics), PVF (Polyvinyl fluoride ), a plastic substrate made of polyester, acrylic or the like can be used.

[0176] In this manner, an active matrix light emitting device can be obtained.

[0177] 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.

[0178] (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.

[0179] 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.

[0180] 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.

[0181] 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.

[0182] 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.

[0183] 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. .

[0184] 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.

[0185] 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 .

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] 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.

[0196] In addition, the touch panel area 9632a and the touch panel area 9632b are simultaneously You can also use touch input.

[0197] 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.

[0198] 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.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] 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. , which can be provided on one or both sides of the housing 9630, and can efficiently charge the battery 9635. The battery 9635 may be a lithium-ion battery. The use of a pond has the advantage of making it possible to reduce the size.

[0203] 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 .

[0204] 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 may be such that W2 is turned on to charge the battery 9635.

[0205] 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.

[0206] In addition, if the display unit described in the above embodiment is provided, the electronic device shown in FIG. It goes without saying that there is no particular limitation.

[0207] 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.

[0208] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. There can be.

[0209] (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.

[0210] 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.

[0211] 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.

[0212] 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.

[0213] The structure described in this embodiment may be used in appropriate combination with structures described in other embodiments. There can be. EXAMPLES

[0214] 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.

[0215] [ka]

[0216] <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.

[0217] 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.

[0218] 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.

[0219] 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.

[0220] 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 P-II (abbreviation): molybdenum oxide = 4:2 (mass ratio) Thus, a hole injection layer 1111 was formed on the first electrode 1101. The thickness of the layer was set to 20 nm. Co-evaporation is a method of vapor deposition in which different substances are vaporized simultaneously from different sources. It is.

[0221] Next, 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine A hole transport layer 1112 is formed by depositing 20 nm of BPAFLP. Ta.

[0222] 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 -Fluorene-2-amine (abbreviation: PCBBiF), (acetylacetonato)bis(6- tert-Butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir( tBuppm)2(acac)]) was used as a template for 2mDBTBPDBq-II (abbreviation: PCBB iF(abbreviation):[Ir(tBuppm)2(acac)](abbreviation)=0.7:0.3:0 The first light-emitting layer 1113a was formed to a thickness of 20 nm by co-evaporation so that the ratio of the layers was 0.05 (mass ratio). After that, 2mDBTBPDBq-II (abbreviation), N,N'-bis(9,9-dimethylfulv) N,N'-di(biphenyl-4-yl)-1,4-phenylenediamine 2,6-dimethyl-2-[5-(2,6-dimethylphenyl)-2,4-dimethylphenyl] phenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC }(2,8-dimethyl-4,6-nonanedionato-κ 2 O,O') Iridium(III) (Abbreviation: [Ir(dmdppr-dmp)2(divm)]) -II(abbreviation):FBi2P(abbreviation):[Ir(dmdppr-dmp)2(divm) ] (abbreviation) = 0.8:0.2:0.05 (mass ratio) to form a second light-emitting layer. 1113b is formed to a thickness of 20 nm to form a light emitting layer 1113 having a laminated structure. Ta.

[0223] Next, 2mDBTBPDBq-II (abbreviation) was evaporated to a thickness of 15 nm on the light-emitting layer 1113. Electron transport 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.

[0224] 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 the depositions, a resistance heating method was used.

[0225] The element structure of the thus obtained Light-emitting Element 1 is shown in Table 1.

[0226] [Table 1]

[0227] 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.) ).

[0228] <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.

[0229] 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).

[0230] FIG. 15 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.

[0231] [Table 2]

[0232] From the above results, the light-emitting device 1 fabricated in this example exhibits high external quantum efficiency. , and shows high luminous efficiency.

[0233] 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 is 546 nm and 615 nm. There are two peaks at around nm, which are phosphorescent organometallic iridium complexes [Ir( tBuppm)2(acac)] and [Ir(dmdppr-dmp)2(divm)] This suggests that it is due to luminescence.

[0234] In addition, cyclic voltammetry measurements revealed that the second organic compound with hole transport properties The HOMO level of PCBBiF is -5.36 eV, and the third functional group has hole transport properties. The HOMO level of the organic compound FBi2P was estimated to be -5.13 eV. The second organic compound has a lower HOMO level than the third organic compound. do.

[0235] FIG. 18 shows a first organic compound having an electron transport property, 2mDBTBPDBq The emission spectrum of the thin film of PCBBi-II, the second organic compound with hole transport properties. The emission spectra of the thin film of F and the mixed film of 2mDBTBPDBq-II and PCBBiF ( The emission spectrum of the first organic compound having electron transport properties is shown in FIG. The emission spectrum of the thin film of the compound 2mDBTBPDBq-II, The emission spectra of the thin films of the organic compound FBi2P and 2mDBTBPDBq- The emission spectrum of the mixed film (co-evaporated film) of II and FBi2P is shown.

[0236] From Figures 18 and 19, the emission wavelength of the mixed film is longer than that of the single film of each material. Since the first organic compound (2mDBTBPDBq-II) and the second organic compound The first organic compound (2mDBTBPDBq-II) and the third It can be seen that the organic compound (FBi2P) forms an exciplex. The first organic compound (2mDBTBPDBq-II) and the second organic compound (PCBBiF) The emission wavelength of the exciplex formed is 511 nm, whereas the emission wavelength of the first organic compound (2mD Luminescence from the exciplex formed by BTBPDBq-II) and a third organic compound (FBi2P) Since the wavelength is 553 nm, it can be seen that the former has greater energy. [Explanation of symbols]

[0237] 101 First electrode 102 Second electrode 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 Luminous materials 109a The first luminescent material that converts triplet excitation energy into luminescence 109b A second luminescent material that converts triplet excitation energy into luminescence 110 The first organic compound 111 Second organic compound 112 The third 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 209 Luminous materials 209a The first luminescent material that converts triplet excitation energy into luminescence 209b A second luminescent material that converts triplet excitation energy into luminescence 210 The first organic compound 211 Second organic compound 212 The third organic compound 301 First electrode 302(1) First EL layer 302(2) Second EL layer 302(n-1) EL layer (n-1) 302(n) EL layer (n) 304 Second electrode 305 Charge generation layer (I) 305(1) First charge generating layer (I) 305(2) Second charge generating layer (I) 305(n-2) (n-2)th charge generating layer (I) 305(n-1) th (n-1) 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 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 first light-emitting layer and a second light-emitting layer in contact with the first light-emitting layer between a pair of electrodes; the first light-emitting layer includes a first light-emitting substance and two kinds of organic compounds that form a first exciplex; the second light-emitting layer includes a second light-emitting substance and two kinds of organic compounds that form a second exciplex; a difference between a peak energy value of an emission spectrum of the first exciplex and a peak energy value of an absorption band on the lowest energy side of an absorption spectrum of the first luminescent material is within 0.2 eV; the excitation energy of the first exciplex is greater than the excitation energy of the second exciplex; The first light-emitting substance emits light having a shorter wavelength than the second light-emitting substance.

2. a first light-emitting layer and a second light-emitting layer in contact with the first light-emitting layer between a pair of electrodes; the first light-emitting layer includes a first light-emitting substance and two kinds of organic compounds that form a first exciplex; the second light-emitting layer includes a second light-emitting substance and two kinds of organic compounds that form a second exciplex; a difference between an energy value of a peak in an emission spectrum of the second exciplex and an energy value of a peak in an absorption band on the lowest energy side in an absorption spectrum of the second luminescent material is within 0.2 eV; the excitation energy of the first exciplex is greater than the excitation energy of the second exciplex; The first light-emitting substance emits light having a shorter wavelength than the second light-emitting substance.

3. a first light-emitting layer and a second light-emitting layer in contact with the first light-emitting layer between a pair of electrodes; the first light-emitting layer includes a first light-emitting substance and two kinds of organic compounds that form a first exciplex; the second light-emitting layer includes a second light-emitting substance and two kinds of organic compounds that form a second exciplex; a difference between a peak energy value of an emission spectrum of the first exciplex and a peak energy value of an absorption band on the lowest energy side of an absorption spectrum of the first luminescent material is within 0.2 eV; a difference between an energy value of a peak in an emission spectrum of the second exciplex and an energy value of a peak in an absorption band on the lowest energy side in an absorption spectrum of the second luminescent material is within 0.2 eV; the excitation energy of the first exciplex is greater than the excitation energy of the second exciplex; The first light-emitting substance emits light having a shorter wavelength than the second light-emitting substance.

4. a first light-emitting layer and a second light-emitting layer in contact with the first light-emitting layer between a pair of electrodes; the first light-emitting layer includes a first organometallic complex and two kinds of organic compounds that form a first exciplex; the second light-emitting layer includes a second organometallic complex and two kinds of organic compounds that form a second exciplex; a difference between a peak energy value of an emission spectrum of the first exciplex and a peak energy value of an absorption band on the lowest energy side of an absorption spectrum of the first organometallic complex is within 0.2 eV; the excitation energy of the first exciplex is greater than the excitation energy of the second exciplex; The first organometallic complex emits light having a shorter wavelength than the second organometallic complex.

5. a first light-emitting layer and a second light-emitting layer in contact with the first light-emitting layer between a pair of electrodes; the first light-emitting layer includes a first organometallic complex and two kinds of organic compounds that form a first exciplex; the second light-emitting layer includes a second organometallic complex and two kinds of organic compounds that form a second exciplex; a difference between a peak energy value of an emission spectrum of the second exciplex and a peak energy value of an absorption band on the lowest energy side of an absorption spectrum of the second organometallic complex is within 0.2 eV; the excitation energy of the first exciplex is greater than the excitation energy of the second exciplex; The first organometallic complex emits light having a shorter wavelength than the second organometallic complex.

6. a first light-emitting layer and a second light-emitting layer in contact with the first light-emitting layer between a pair of electrodes; the first light-emitting layer includes a first organometallic complex and two kinds of organic compounds that form a first exciplex; the second light-emitting layer includes a second organometallic complex and two kinds of organic compounds that form a second exciplex; a difference between a peak energy value of an emission spectrum of the first exciplex and a peak energy value of an absorption band on the lowest energy side of an absorption spectrum of the first organometallic complex is within 0.2 eV; a difference between a peak energy value of an emission spectrum of the second exciplex and a peak energy value of an absorption band on the lowest energy side of an absorption spectrum of the second organometallic complex is within 0.2 eV; the excitation energy of the first exciplex is greater than the excitation energy of the second exciplex; The first organometallic complex emits light having a shorter wavelength than the second organometallic complex.

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