Energy donor material and host material

Abstract

An object of one embodiment of the present invention is to provide a light-emitting element which includes a substance exhibiting thermally activated delayed fluorescence as a light-emitting substance and has higher emission efficiency.SOLUTION: A light-emitting element in which an exciplex is used as an energy donor capable of efficiently transferring energy to a substance exhibiting thermally activated delayed fluorescence is provided. Since the exciplex is formed from two kinds of substances and the singlet excited state and the triplet excited state thereof are close to each other, light emitted from the exciplex is made to overlap with an absorption band on the longest wavelength side, which is absorption in the singlet excited state of the substance exhibiting thermally activated delayed fluorescence serving as an energy acceptor; To achieve more efficient energy transfer from a singlet excited state of an exciplex to a singlet excited state of a substance exhibiting thermally activated delayed fluorescence, and to achieve more efficient energy transfer from a triplet excited state of the exciplex to a triplet excited state of the substance exhibiting thermally activated delayed fluorescence.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a light-emitting element, a display device, a light-emitting device, and an electronic device using an organic compound as a light-emitting substance. and lighting devices. [Background technology]

[0002] In recent years, electroluminescence (EL) Research and development of light-emitting devices using this material is currently underway. The basic structure of these light-emitting devices is as follows: A layer containing a light-emitting substance (EL layer) is sandwiched between a pair of electrodes. When a voltage is applied to this element, By doing so, light can be emitted from the luminescent substance.

[0003] These light-emitting elements are self-luminous, so the pixels are more visible than LCD displays. It has the advantage of not requiring a backlight, making it suitable for use as a flat panel display element. Furthermore, displays using such light-emitting elements can be manufactured to be thin and lightweight. Both of these are major advantages. Another feature is its extremely fast response time.

[0004] These light emitting elements can form the light emitting layer in a film form, so that light can be emitted in a planar form. Therefore, a large-area light source can be easily formed. This is a feature that is difficult to obtain with point light sources such as bulbs and LEDs, or linear light sources such as fluorescent lamps. Therefore, it is highly useful as a surface light source that can be applied to lighting, etc.

[0005] In the case of an organic EL element in which an organic compound is used as a light-emitting substance and the EL layer is provided between a pair of electrodes, By applying a voltage between a pair of electrodes, electrons are emitted from the cathode and holes are emitted from the anode. The electrons and holes are injected into the EL layer, causing a current to flow. The recombination causes the luminescent organic compound to enter an excited state, and the excited luminescent organic The compound can emit light.

[0006] The types of excited states that organic compounds form are singlet excited states and triplet excited states. , singlet excited state (S * ) is emitted from the triplet excited state (T * ) is emitted from phosphorus The statistical generation rate of this light in the light-emitting element is S * :T * = It is believed that the ratio is 1:3. Therefore, it is possible to convert the triplet excited state into luminescence. 2. Description of the Related Art In recent years, there has been active development of light-emitting devices using phosphorescent compounds.

[0007] However, most of the phosphorescent compounds currently in use contain rare elements such as iridium. It is a complex with a metal as the central metal, and there are concerns about its cost and supply stability. Delayed fluorescence is a material that can convert triplet excited states into luminescence without using rare metals. Research is also being conducted into light-emitting materials.

[0008] In Patent Documents 1 and 2, thermally activated delayed fluorescence (Th ermally activated delayed fluorescence;T A material that emits TADF (Also referred to as TADF material) has been disclosed. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-241374 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-024830 Summary of the Invention [Problem to be solved by the invention]

[0010] The layer that emits light from the light-emitting element (light-emitting layer) has the following features: prevention of concentration quenching, control of the light-emitting position, and the light-emitting material However, due to the poor film quality of the host molecules, luminescent materials are dispersed as guest molecules in the host molecules. The so-called host-guest structure is often used. In this case, the recombination of holes and electrons occurs. Although this phenomenon occurs in emitting materials, it mostly occurs in host materials, and in order to improve luminous efficiency, It is necessary to consider the energy transfer from the host molecule to the guest molecule.

[0011] However, the TADF technology described in Patent Documents 1 and 2, etc., in which TADF occurs with high efficiency, In the material, the singlet excited state and the triplet excited state are close to each other, so the positions between the excited states are The positional relationship is different from that of ordinary luminescent materials and host molecules. However, efficient energy transfer is difficult.

[0012] In view of this, in one embodiment of the present invention, in a light-emitting element using a TADF material as a light-emitting substance, Another object of the present invention is to provide a light-emitting element having high emission efficiency. By using the light-emitting element described above, a light-emitting device, a display device, and an electronic device with reduced power consumption are provided. and a lighting device.

[0013] The present invention is intended to solve any one of the above problems. [Means for solving the problem]

[0014] In the present invention, an energy molecule capable of efficiently transferring energy to a substance exhibiting thermally activated delayed fluorescence is A light-emitting element using an exciplex as a donor is provided. is formed from two kinds of substances, and its singlet excited state and triplet excited state are close to each other. Therefore, it exhibits thermally activated delayed fluorescence, which is an energy acceptor. The emission of the exciplex is superimposed on the absorption band at the longest wavelength, which is the absorption of the singlet excited state of the substance. By this, the singlet excited state of the exciplex can be converted into the singlet excited state of a material that exhibits thermally activated delayed fluorescence. This allows for more efficient energy transfer from the triplet excited state of the exciplex while also allowing for more efficient energy transfer from the triplet excited state of the exciplex. The energy transfer from the excited state to the triplet excited state of a material exhibiting thermally activated delayed fluorescence was also improved. This is possible.

[0015] That is, one embodiment of the present invention is a light-emitting device having a pair of electrodes and an EL layer sandwiched between the pair of electrodes, The L layer has at least a light-emitting layer, and the light-emitting layer contains a first organic compound, a second organic compound, and a light-emitting and a photoluminescent substance, and the first organic compound and the second organic compound form an exciplex. The light-emitting element is a combination of the above, and the light-emitting substance is a substance that exhibits thermally activated delayed fluorescence.

[0016] Another aspect of the present invention is a device having a pair of electrodes and an EL layer sandwiched between the pair of electrodes. The layer has at least an emissive layer, and the emissive layer comprises a first organic compound, a second organic compound, and an emissive and a substance, wherein the first organic compound and the second organic compound form an exciplex. The luminescent material is a material that exhibits thermally activated delayed fluorescence, A light-emitting element in which the lowest energy absorption band of the substance and the emission spectrum of the exciplex overlap. is.

[0017] In addition, another aspect of the present invention is the above-mentioned aspect, wherein the lowest energy of the substance exhibiting thermally activated delayed fluorescence is The energy equivalent of the peak wavelength of the absorption band on the high-energy side and the peak wavelength of the emission of the exciplex The difference between the two is 0.2 eV or less.

[0018] In addition, another aspect of the present invention is the above-mentioned aspect, wherein the fluorescent peak of the substance exhibiting thermally activated delayed fluorescence is The difference in energy equivalent between the peak wavelength and the phosphorescence peak wavelength is 0.2 eV or less. It is an element.

[0019] In addition, another aspect of the present invention is a method for manufacturing a compound semiconductor device according to the above aspect, wherein the peak wavelength of the fluorescence of the exciplex and the peak wavelength of the phosphorescence of the exciplex are The difference in energy equivalent value between the peak wavelength of the light emitting element and the peak wavelength of the light emitting element is 0.2 eV or less.

[0020] In addition, another aspect of the present invention is the above-mentioned aspect, wherein the substance exhibiting thermally activated delayed fluorescence has π electrons. The light-emitting device is a heterocyclic compound having a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring. do.

[0021] In addition, another aspect of the present invention is the above-mentioned aspect, wherein the substance exhibiting thermally activated delayed fluorescence has π electrons. A light-emitting element that is a heterocyclic compound in which an excess type heteroaromatic ring and a π-electron deficient type heteroaromatic ring are directly bonded. He is a child.

[0022] Another embodiment of the present invention is a light-emitting device, a display device, or a display device including a light-emitting element having the above structure. Electronic devices and lighting devices.

[0023] In this specification, the term "light-emitting device" includes an image display device using a light-emitting element. In addition, a connector, such as anisotropic conductive film or TCP (Tape C), is attached to the light emitting element. A module with a printed wiring board (Package) attached, and a TCP Module with wiring board or COG (Chip On Glass) type light emitting element According to the formula, all modules in which ICs (integrated circuits) are directly mounted are also included in the light-emitting device. Furthermore, it also includes light-emitting devices used in lighting fixtures, etc. [Effects of the Invention]

[0024] One embodiment of the present invention can provide a light-emitting element with high emission efficiency. Light-emitting device, display device, electronic device, and lighting device with reduced power consumption by using the device The device can be provided. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a conceptual diagram of a light-emitting element. [Figure 2] FIG. 1 is a diagram showing energy transfer in a light-emitting layer. [Figure 3] 1 is a conceptual diagram of an active matrix light-emitting device. [Figure 4] FIG. 1 is a conceptual diagram of a passive matrix light-emitting device. [Figure 5] 1 is a conceptual diagram of an active matrix light-emitting device. [Figure 6] 1 is a conceptual diagram of an active matrix light-emitting device. [Figure 7] Conceptual diagram of a lighting device. [Figure 8] 1 is a diagram showing an electronic device. [Figure 9] 1 is a diagram showing an electronic device. [Figure 10] FIG. [Figure 11] FIG. [Figure 12] FIG. 2 is a diagram illustrating an in-vehicle display device and an illumination device. [Figure 13] 1 is a diagram showing an electronic device. [Figure 14] FIG. 1 is a diagram for explaining the emission wavelength of an exciplex. [Figure 15] 1 shows current density-luminance characteristics of the light-emitting element 1 and the comparative light-emitting element 1. [Figure 16] Voltage-luminance characteristics of the light-emitting element 1 and the comparative light-emitting element 1. [Figure 17] 1 shows luminance-current efficiency characteristics of the light-emitting element 1 and the comparative light-emitting element 1. [Figure 18] 1 shows luminance-power efficiency characteristics of the light-emitting element 1 and the comparative light-emitting element 1. [Figure 19] 1 shows the luminance-external quantum efficiency characteristics of the light-emitting element 1 and the comparative light-emitting element 1. [Figure 20] 1 shows emission spectra of the light-emitting element 1 and the comparative light-emitting element 1. [Figure 21] 10 shows current density-luminance characteristics of the light-emitting element 2 and the comparative light-emitting element 2. [Figure 22] Voltage-luminance characteristics of the light-emitting element 2 and the comparative light-emitting element 2. [Figure 23] 10 shows luminance-current efficiency characteristics of the light-emitting element 2 and the comparative light-emitting element 2. [Figure 24] 10 shows luminance-power efficiency characteristics of the light-emitting element 2 and the comparative light-emitting element 2. [Figure 25] 1 shows the luminance-external quantum efficiency characteristics of the light-emitting element 2 and the comparative light-emitting element 2. [Figure 26] 1 shows emission spectra of the light-emitting element 2 and the comparative light-emitting element 2. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments 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 form and details thereof may be changed without departing from the spirit and scope of the present invention. It will be readily apparent to those skilled in the art that various modifications may be made to the present invention. It should not be construed as being limited to the description of the embodiments.

[0027] (Embodiment 1)

[0028] In a light-emitting device using a material that exhibits thermally activated delayed fluorescence (TADF) as a light-emitting material, The light emission occurs through the energy process shown below. The molecule that receives the TADF (energy donor) is the host molecule, and the substance that exhibits the TADF (energy accessor) is the The guest molecule is referred to as the α-substrate.

[0029] (1) Electrons and holes recombine in the guest molecule, and the guest molecule enters an excited state. (direct recombination process).

[0030] (1-1) When the excited state of the guest molecule is a singlet excited state: Fluorescence is emitted. (1-2) When the excited state of the guest molecule is a triplet excited state: Energy (mainly heat) is released. Upon absorption, it undergoes reverse intersystem crossing to a singlet excited state, emitting fluorescence.

[0031] In the direct recombination process (1) above, the reverse intersystem crossing efficiency of the guest molecule and the fluorescence quantum If the yield is high, high luminous efficiency can be obtained. The S1 and T1 levels of the host molecule are Singlet excitation energy level (S1 level) and triplet excitation energy level of guest molecules It is preferable that the T level is higher than the T level. The above patent documents and various publications have been published regarding the substance (guest molecule).

[0032] (2) The electrons and holes recombine in the host molecule, and the host molecule enters an excited state. (energy transfer process).

[0033] (2-1) When the excited state of the host molecule is a singlet excited state When the S1 level of the host molecule is higher than the S1 level of the guest molecule, the host molecule The excitation energy is transferred to the guest molecule, and the guest molecule enters a singlet excited state. The guest molecule in this state emits fluorescence. Energy transfer to the T1 level occurs from the singlet ground state to the triplet excited state in the guest molecule. Since direct transition to is forbidden, it is unlikely to be the main energy transfer process. In other words, as shown in the following formula (2-1), the singlet excited state ( 1 H * ) to the singlet excited state of the guest molecule ( 1 G * ) is important (in the formula , 1 G is the singlet ground state of the guest molecule, 1 H represents the singlet ground state of the host molecule).

[0034] 1 H * + 1 G → 1 H+ 1 G * (2-1)

[0035] (2-2) When the excited state of the host molecule is a triplet excited state If the T1 level of the host molecule is higher than the S1 and T1 levels of the guest molecule, The excitation energy is transferred from the T1 level of the molecule to the T1 level of the guest molecule, and the guest molecule becomes triplet-like. The guest molecule in the triplet excited state absorbs thermal energy. This causes reverse intersystem crossing and the emission of fluorescence.

[0036] That is, as shown in the following formula (2-2), the triplet excited state of the host ( 3 H * ) to the guest molecule The triplet excited state of ( 3 G * ), and then reverse intersystem crossing occurs to the guest molecule The singlet excited state ( 1 G * ) is generated.

[0037] 3 H * + 1 G → 1 H+ 3 G * →(thermal energy)→(reverse intersystem crossing)→ 1 H+ 1 G * (2-2)

[0038] If all the energy transfer processes described above in (2) occur efficiently, the triple bond of the host molecule will be Both the first and singlet excitation energies are efficiently converted to the singlet excited states of the guest molecules. state( 1 G * ), which allows for highly efficient light emission. Before the excitation energy is transferred to the host molecule, the host molecule itself absorbs the excitation energy with light or If the energy is released as heat and deactivated, the luminous efficiency will decrease.

[0039] Next, we consider the factors that govern the energy transfer process between the host and guest molecules mentioned above. There are two types of intermolecular energy transfer mechanisms: the Förster mechanism and the Dexter mechanism. Two mechanisms have been proposed:

[0040] First, the first mechanism, the Förster mechanism (dipole-dipole interaction), is -Transfer does not require direct contact between molecules, but is achieved by dipole vibration between 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, and the host molecule returns to the ground state, and the guest The molecule enters an excited state. The rate constant of the Förster mechanism is k h*→g is shown in equation (1). vinegar.

[0041]

number

[0042] 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 the 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 represents the refractive index, R represents the intermolecular distance between the host molecule and the guest molecule, and τ represents the measured excitation represents the lifetime of the excited state (fluorescence lifetime or phosphorescence lifetime), c represents the speed of light, and φ represents the luminescence quantum yield. (When discussing energy transfer from the singlet excited state, the fluorescence quantum yield is When discussing energy transfer from 2 The host molecule and guest molecule The coefficient (0 to 4) represents the orientation of the transition dipole moment of the molecule. In the case of K 2 =2 / 3.

[0043] Next, in the second mechanism, the Dexter mechanism (electron exchange interaction), the host molecule and the gate The host molecule approaches the effective contact distance where orbital overlap occurs, and the electrons of the excited host molecule Energy transfer occurs through the exchange of electrons in the ground state guest molecule. rate constant k of the mechanism h*→g is shown in equation (2).

[0044]

number

[0045] In equation (2), h is Planck's constant, and K' is a constant with the dimension of energy. where ν represents the frequency and f' represents the h (ν) is the normalized emission spectrum of the host molecule (Fluorescence spectrum when discussing energy transfer from singlet excited states, triplet excited states) When discussing energy transfer from the ε' state, it represents the phosphorescence spectrum. g (ν) is represents the normalized absorption spectrum of the guest molecule, L represents the effective molecular radius, and R represents the represents the intermolecular distance between the host molecule and the guest molecule.

[0046] Here, the energy transfer efficiency from the host molecule to the guest molecule Φ ET is expressed as formula (3). It is thought that this will be the case. r is the emission process of the host molecule (energy from the singlet excited state). (Fluorescence is used when discussing energy transfer from triplet excited states, and phosphorescence is used when discussing energy transfer from triplet excited states.) represents the rate constant of n is the rate constant of the non-radiative process (thermal deactivation and intersystem crossing) of the host molecule. and τ represents the measured lifetime of the excited state of the host molecule.

[0047]

number

[0048] From equation (3), the energy transfer efficiency Φ ET To increase the energy transfer rate, Degree constant k h*→g By increasing the rate constant k r +k n (=1 / τ) is relatively You know the smaller the better.

[0049] (Regarding the energy transfer efficiency of (2-1)) Consider the energy transfer process of (2-1). The process of equation (2-1) is the Förster mechanism. Energy transfer by both the Dexter mechanism (Equation (1)) and the Dexter mechanism (Equation (2)) is considered. can be done.

[0050] First, consider the energy transfer by the Förster mechanism. From equations (1) and (3), τ is Eliminating this, the energy transfer efficiency Φ ET is the quantum yield φ (energy from the singlet excited state) Since we are discussing the transfer of light, it can be said that a higher fluorescence quantum yield is better. The emission spectrum of the host molecule (energy from the singlet excited state) is an important factor for Since we are discussing energy transfer, we will examine the fluorescence spectrum and the absorption spectrum (singlet basis) of the guest molecule. It is also necessary to have a large overlap with the absorption corresponding to the transition from the excited state to the singlet state. (Note that it is also preferable that the molar absorption coefficient of the guest molecule is high.) This means that the fluorescence of the host material The optical spectrum and the absorption band that appears on the longest wavelength side of the TADF guest material. This means that they overlap.

[0051] Next, consider the energy transfer via the Dexter mechanism. According to equation (2), the rate constant k h*→g To increase the emission spectrum (energy from the singlet excited state) of the host molecule, Since we are discussing the transfer of the guest molecule, we will examine the fluorescence spectrum and the absorption spectrum of the guest molecule (singlet ground state). It was found that the larger the overlap with the absorption corresponding to the transition from the excited state to the singlet state, the better. do.

[0052] From the above, the optimization of the energy transfer efficiency in (2-1) is based on the fluorescence spectrum of the host molecule. The absorption band of the guest material, which exhibits TADF, is overlapped with the absorption band that appears on the longest wavelength side. This is achieved by:

[0053] (Regarding the energy transfer efficiency of (2-2)) Consider the energy transfer process of (2-2). The process of equation (2-1) is based on the Dexter mechanism (equation (2)) Energy transfer by the Förster mechanism is considered. In this case, the explanation is omitted because it is forbidden. As mentioned above, the rate constant k h*→g In order to increase the emission spectrum of the host molecule (three Since we are discussing energy transfer from the singlet excited state, we will consider the phosphorescence spectrum and the guest molecule. Absorption spectrum (absorption corresponding to the direct transition from the singlet ground state to the triplet excited state) In this configuration, the guest material is a fluorescent compound, and the host material is also a Since these compounds are usually fluorescent, their spectra are difficult to observe at room temperature. In such cases, the phosphorescence spectrum and absorption spectrum estimated by molecular orbital calculations are used. In particular, regarding phosphorescence spectra, It can sometimes be observed in a body with a helium atmosphere.

[0054] In addition, since the host molecule is usually a fluorescent compound, the phosphorescence lifetime (τ) is expected to be more than a millisecond. Very long (k r +k n This is because the triplet excited state is converted to the ground state (singlet). This is because the transition of is forbidden. From equation (3), this means that the energy transfer efficiency Φ ET It works to your advantage.

[0055] Considering the above, the energy transfer from the host molecule to the guest molecule, i.e., the formula The process of (2-1) and (2-2) is based on the fluorescence spectrum of the host molecule and one of the guest molecules. The absorption spectrum corresponding to the transition from the ground state to the singlet excited state is superimposed on the absorption spectrum corresponding to the transition from the ground state to the singlet excited state. The (assumed) phosphorescence spectrum of the host material and the (assumed) singlet ground state of the guest material The total absorption spectrum is obtained by simply superimposing the absorption spectrum corresponding to the direct transition from the excited state to the triplet excited state. This tends to occur more easily.

[0056] However, there are many materials that exhibit thermally activated delayed fluorescence, especially those that exhibit thermally activated delayed fluorescence with high efficiency at relatively low temperatures. In materials that exhibit extended fluorescence (TADF materials), the S1 level and the T1 level are close to each other. The absorption spectrum corresponding to the transition from the singlet ground state to the singlet excited state of the guest molecule. Absorption spectrum corresponding to the (assumed) direct transition from the singlet ground state to the triplet excited state Therefore, the fluorescence and phosphorescence spectra of the host molecule are also The host molecule must be designed to be in a similar position.

[0057] 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 peak at around 500 nm. It has a phosphorescence spectrum, while its fluorescence spectrum is around 400 nm, and Even in this example, the fluorescence spectrum of the host molecule is different from the phosphorescence spectrum. It is extremely difficult to design a host molecule that is positioned similarly to the spectrum. .

[0058] Therefore, one aspect of the present invention is to provide a substance that exhibits thermally activated delayed fluorescence, particularly a substance that exhibits high thermally activated delayed fluorescence at relatively low temperatures. When a substance that exhibits thermally activated delayed fluorescence with high efficiency is used as the light-emitting substance, the triple This is useful because it can overcome the problem of the efficiency of energy transfer from the first excited state to the guest molecule. The present invention provides a method for achieving this. Specific aspects of the method will be described below.

[0059] In this embodiment, an energy source capable of efficiently transferring energy to a substance exhibiting thermally activated delayed fluorescence is used. The present invention provides a light-emitting device using an exciplex as an energy donor. A complex is formed from two substances, and its singlet excited state and triplet excited state are close to each other. Therefore, the thermally activated delayed fluorescent The absorption band at the longest wavelength (from the singlet ground state to the singlet excited state) of a substance that emits light The excitation is achieved by superimposing the fluorescence of the exciplex on the absorption corresponding to the transition to the singlet excited state. The energy from the singlet excited state of a catalytic complex to the singlet excited state of a material exhibiting thermally activated delayed fluorescence While increasing the transfer efficiency, we also aim to reduce the (assumed) phosphorescence from the triplet excited state of the exciplex. Spectral and triplet excitations from the (possible) singlet ground state of materials exhibiting thermally activated delayed fluorescence. Absorption corresponding to a direct transition to the state can be superimposed.

[0060] This allows the singlet excited state of the exciplex to be converted into the singlet excited state of a substance that exhibits thermally activated delayed fluorescence. It also increases the efficiency of energy transfer to the triplet excited state of the exciplex, and delays the thermal activation It is also possible to increase the efficiency of energy transfer to the triplet excited state of substances that exhibit extended fluorescence. .

[0061] In addition, the positions of the S1 and T1 levels usually differ for each substance, and the fluorescent substance is When used as a host and guest material, the fluorescence spectrum of the host molecule and the singlet state of the guest molecule are Even if it were possible to superimpose absorption corresponding to the transition from the ground state to the singlet excited state, The (assumed) phosphorescence spectrum of the host molecule and the (assumed) singlet of the guest molecule The absorptions corresponding to the energy transfer from the triplet ground state to the triplet excited state do not necessarily overlap. Moreover, the phosphorescence spectrum of fluorescent materials and the transition from the singlet ground state to the triplet excited state Absorption corresponding to energy transfer is often difficult or impossible to observe. It is also difficult to confirm whether the two overlap.

[0062] On the other hand, as mentioned above, both the material that exhibits thermally activated delayed fluorescence and the exciplex have S1 and T1 levels. Because the positions are close to each other, the singlet ground state of the material exhibiting thermally activated delayed fluorescence can be converted to the singlet excited state. By superimposing the absorption corresponding to the transition to the exciplex and the fluorescence spectrum of the exciplex, , the (assumed) singlet ground state of a material that naturally exhibits thermally activated delayed fluorescence to triplet excited state The absorption corresponding to the direct transition to the exciplex and the (assumed) phosphorescence spectrum of the exciplex are superimposed. It becomes possible to match.

[0063] In the light-emitting element having the above-described structure, efficient energy transfer occurs as shown in FIG. FIG. 2 shows a state in which a light-emitting layer 113 is provided between an electrode 10 and an electrode 11. An optional layer may be present between each electrode and the light-emitting layer 113. The singlet excited state Se of 13Ec is transferred to the singlet excited state Sa of the luminescent material 113D. The triplet excited state Te of the exciplex is converted to the triplet excited state of the luminescent material 113D. Energy transfer occurs to the state Ta. Then, the triplet excited state of the luminescent material 113D emits light. Reverse intersystem crossing occurs in the singlet excited state of the substance, and light is emitted from the singlet excited state Sa of the luminescent substance 113D. In the light-emitting element of this embodiment, these energy transfers occur smoothly. By performing this, a light-emitting element with high luminous efficiency can be provided.

[0064] A conceptual diagram of the light-emitting element in this embodiment is shown in Fig. 1. Fig. 1(a) is a diagram of the light-emitting element. , (b) is an enlarged view of only the light-emitting layer.

[0065] The light-emitting element includes an EL layer 10 sandwiched between a pair of electrodes, a first electrode 101 and a second electrode 102. 3, and the EL layer 103 contains an organic compound as a light-emitting material. The light-emitting layer 113 includes a light-emitting material. Regarding the other layers, there is no limitation, and any other layers may be used. The typical laminated structure includes a hole injection layer 111, a hole transport layer 112, a light emitting layer 113, and an electron transport layer. layer 114, an electron injection layer 115, etc. In addition, a carrier block layer, etc. may be provided. Alternatively, a plurality of light-emitting layers may be provided.

[0066] As shown in FIG. 1(b), the light-emitting layer 113 contains a first organic compound 113H and a second organic compound 113H. The light-emitting element of this embodiment includes a compound 113A and a light-emitting material 113D. The first organic compound 113H and the second organic compound 113A are used as a host material. In the light-emitting element of this embodiment, the light-emitting layer 113 is formed of other It does not exclude the presence of any substance.

[0067] The first organic compound 113H and the second organic compound 113A are combined to form an exciplex. The exciplex is in a state where its S1 level and T1 level are close to each other, but especially the S A compound that forms an exciplex with an energy difference between the T1 level and the T1 level of 0 eV or more and 0.2 eV or less. A combination is preferred.

[0068] The luminescent substance 113D is a substance that exhibits thermally activated delayed fluorescence, and preferably exhibits a thermally activated delayed fluorescence at a relatively low temperature. It is a substance that efficiently exhibits thermally activated delayed fluorescence at temperatures (for example, below 100°C). A substance in which the energy difference between the S1 level and the T1 level is 0 eV or more and 0.2 eV or less is preferred. Delayed fluorescence is a type of fluorescence that has the same spectrum as normal fluorescence in a certain substance but has a longer lifespan. It is a very long-lived luminescence. Its life span is 10 -6 seconds or more, preferably 10 -3 in more than a second be.

[0069] Furthermore, the exciplex and the substance exhibiting thermally activated delayed fluorescence are compounds having the above-mentioned relationship. That is, the fluorescence spectrum of the exciplex and the thermally activated delayed fluorescence are combined. This is a combination in which the absorption bands at the longest wavelengths of the substances overlap. The energy is efficiently converted from the singlet excited state of the material that exhibits thermally activated delayed fluorescence to the singlet excited state of the material. The movement of the character is performed.

[0070] In addition, in both exciplexes and materials that exhibit thermally activated delayed fluorescence, the S1 level and T1 level are close to each other. Therefore, by increasing the efficiency of energy transfer between singlet excited states as described above, Therefore, it is possible to improve the efficiency of energy transfer between triplet excited states.

[0071] Examples of the substance exhibiting thermally activated delayed fluorescence include fullerene and its derivatives, Examples of such compounds include acridine derivatives such as vin, and eosin.

[0072] In addition, substances that exhibit thermally activated delayed fluorescence include magnesium (Mg), zinc (Zn), and Cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium Examples of such metal-containing porphyrins include metal-containing porphyrins containing palladium (Pd) and the like. For example, protoporphyrin-tin fluoride complex (SnF2) shown in the following structural formula can be used. (Proto IX)), mesoporphyrin-tin fluoride complex (SnF2(Meso I) X), hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), Proporphyrin tetramethyl ester-tin fluoride complex (SnF2(Copro II) I-4Me), octaethylporphyrin-tin fluoride complex (SnF2(OEP)), Ethioporphyrin-tin fluoride complex (SnF2(Etio I)), octaethylporphyrin Phyrin-platinum chloride complex (PtCl2OEP) and the like are also included.

[0073] [ka]

[0074] Furthermore, as a substance that exhibits thermally activated delayed fluorescence, 2-biphenyl- 4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1 π-electron rich heteroaromatic rings and π-electron deficient heteroaromatic rings such as 3,5-triazine (PIC-TRZ) Heterocyclic compounds having a heteroaromatic ring can also be used. The heterocyclic compounds have an excess of π electrons. It has a π-type heteroaromatic ring and a π-electron-deficient heteroaromatic ring, which provides high electron transport and hole transport properties. In addition, a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring are directly bonded to each other. The materials exhibit the donor properties of π-electron rich heteroaromatic rings and the acceptor properties of π-electron deficient heteroaromatic rings. This is particularly favorable because the energy difference between the S1 and T1 levels becomes smaller. .

[0075] [ka]

[0076] The first organic compound 113H and the second organic compound 113A are compounds capable of forming an exciplex. Any combination of known carrier transport materials can be used, but In order to form an exciplex, the first organic compound and the second organic compound are Compounds that are easy to receive (electron trapping compounds) and compounds that are easy to receive holes (positive It is preferable to combine it with a hole-trapping compound.

[0077] Compounds that readily accept electrons include π-electron-deficient heteroaromatic compounds and metal complexes. Specifically, bis(10-hydroxybenzo[h]quinolinato)beryllium Bis(2-methyl-8-quinolinolato)(4-phenyl) Bis(8-quinolinolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato) Zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato] zinc Lead(II) (abbreviation: ZnPBO), bis[2-(2-benzothiazolyl)phenolato] zinc Metal complexes such as lead(II) (abbreviation: ZnBTZ) and 2-(4-biphenylyl)-5-( 4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3 -(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1, 2,4-Triazole (abbreviation: TAZ), 1,3-bis[5-(p-tert-butylphenyl) (phenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9 H-Carbazole (abbreviation: CO11), 2,2',2''-(1,3,5-benzenetriazole) yl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[ 3-(Dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimida Heterocyclic compounds with polyazole skeletons such as azole (abbreviation: mDBTBIm-II) , 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxa Phosphorus (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzothiophene-4-yl) 2mDBTBPD Bq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl] Dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 4,6-bis[3-( (phenanthrene-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4 ,6-Bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDB Heterocyclic compounds with diazine skeletons such as TP2Pm-II) and 3,5-bis[3-( 9H-carbazol-9-yl)phenyl] Pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl] Examples of heterocyclic compounds having a pyridine skeleton include benzophenone (TmPyPB) and benzophenone (TmPyPB). Among the above, heterocyclic compounds having a diazine skeleton and heterocyclic compounds having a pyridine skeleton are preferred. Ring compounds are preferred because of their high reliability. In particular, diazine (pyrimidine or pyrazine) ring compounds are preferred. Heterocyclic compounds having a ring structure have high electron transport properties and also contribute to reducing the driving voltage.

[0078] Compounds that readily accept holes include π-electron-rich heteroaromatic or aromatic amines. Specifically, 4,4'-bis[N-(1-naphthyl)-N -phenylamino]biphenyl (abbreviation: NPB), N,N'-bis(3-methylphenyl )-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: T PD), 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-fluorene phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylphenyl) Fluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3' -(9-Phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP) , 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenyl Amine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9 H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-( 1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenyl Amine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl (9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9, 9-Dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl] N-phenyl-N-[4 -(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-biphenyl Compounds with an aromatic amine skeleton, such as fluorene-2-amine (abbreviated as PCBASF), , 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)benzene Rubazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl) )-9-phenylcarbazole (abbreviation: CzTP), 3,3'-bis(9-phenyl-9 H-carbazole (PCCP) and other compounds with a carbazole skeleton, such as 4, 4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation :DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoro (9-phenyl)dibenzothiophene (abbreviation: DBTFLP-III), 4- [4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzyl Compounds with a thiophene skeleton, such as dithiophene (abbreviated as DBTFLP-IV), and 4 ,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 4-{3-[3-(9-phenyl-9H-fluoren-9-yl) phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II) and other furans Among the above, compounds having an aromatic amine skeleton and Compounds having a carbazole skeleton have good reliability and high hole transport properties. This is preferable because it also contributes to reducing the dynamic voltage.

[0079] The first organic compound and the second organic compound are not limited to those which transport a carrier. and the combination of the two can form an exciplex, and the luminescence of the exciplex is The absorption band at the longest wavelength in the absorption spectrum of the luminescent material (from the singlet ground state to the singlet It is sufficient that the absorption corresponding to the transition to the excited state is overlapped with the absorption corresponding to the transition to the excited state, and other known materials may be used. stomach.

[0080] The first organic compound is a compound that readily accepts electrons and a compound that readily accepts holes. When the first organic compound and the second organic compound are configured, the carrier balance is controlled by the mixing ratio thereof. Specifically, the ratio of the first organic compound to the second organic compound is in the range of 1:9 to 9:1. The surrounding area is preferred.

[0081] Here, each compound forming an exciplex (first organic compound 113H and second organic compound 113A) and exciplexes will be explained in more detail below.

[0082] Figure 14(A) and (B) show the emission spectrum of the substance itself and the emission spectrum of the exciplex. In the figure, Compound 1 is 2-[4-(dibenzothiophen-4-yl)phenyl] -1-phenyl-1H-benzimidazole (abbreviation: DBTBIm-II), compound 2 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxalate Compound 3 was 4,4',4''-tris[N-( 1-Naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1'-TNATA) Compound 4 is 2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino] The compound is 9,9'-spiro-9,9'-bifluorene (abbreviation: DPA2SF), and exciplex 1 is a compound Compound 1 and compound 3 are exciplexes, exciplex 2 is an exciplex of compound 2 and compound 3, and exciplex 3 is an exciplex of compound 3. Compound 2 and 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl The spectrum of the exciplex of compound 2 and compound 4 is It is Tor.

[0083] The structural formulas of each compound are shown below.

[0084] [ka]

[0085] FIG. 14(A) shows the emission spectra of compounds 1 to 3 in addition to exciplex 1 and exciplex 2. The spectrum represented by exciplex 1 is based on compound 1, and compound 3 is slightly The results of measuring the emission of the material doped with the compound The results of measuring the luminescence of a material with compound 2 as the base and a small amount of compound 3 added are shown below. In other words, in the sample in which exciplex 1 was measured, either compound 1 or compound 3 One corresponds to the first organic compound 113H, and the other corresponds to the second organic compound 113A. In the sample in which exciplex 2 was measured, either compound 2 or compound 3 was the first The first organic compound corresponds to the first organic compound 113H, and the other corresponds to the second organic compound 113A.

[0086] As can be seen from Figure 14(A), even if the minor component, compound 3, is the same, exciplex 1 The difference in the emission wavelength between exciplex 1 and exciplex 2 is more than 100 nm. This makes it possible to easily adjust the emission wavelength of the exciplex.

[0087] Since the maximum emission wavelength of exciplex 1 is about 520 nm, compound 1 and compound 3 are The host material containing the compound is suitable as a host material for a material that exhibits blue-green to orange thermally activated delayed fluorescence. It can be used for.

[0088] In addition, the maximum emission wavelength of exciplex 2 is about 610 nm, so compound 2 and compound 3 The host material containing the compound is suitably used as a host material for a material that exhibits red thermally activated delayed fluorescence. It is possible.

[0089] In Figure 14(B), the emission spectra of exciplexes 3 and 4 as well as compounds 2 and 4 are shown. The spectrum represented by exciplex 3 is based on compound 2 and contains a small amount of NPB. The results of measuring the emission of the material doped with a small amount of compound 2 were shown in the spectrum represented by exciplex 4. The results of measuring the luminescence of the material with a small amount of compound 4 added as the base are shown below. In the sample where exciplex 3 was measured, either compound 2 or NPB was the first The first organic compound corresponds to the organic compound 113H, and the other corresponds to the second organic compound 113A. In the sample where the measurement of the catalytic complex 4 was performed, either compound 2 or compound 4 was the first active ingredient. One corresponds to the first organic compound 113H, and the other corresponds to the second organic compound 113A.

[0090] As can be seen from Figure 14(B), even though the base material is the same, exciplex 3 and exciplex The difference in the emission of 4 is close to 100 nm. That is, by changing the minor component, It is also possible to easily adjust the emission wavelength of the exciplex by

[0091] The maximum emission wavelength of exciplex 3 is approximately 520 nm, so it is possible to obtain a compound containing compound 2 and NPB. The host material containing the compound is suitable as a host material for a material that exhibits blue-green to orange thermally activated delayed fluorescence. It can be used.

[0092] In addition, the maximum emission wavelength of exciplex 4 is about 580 nm, so compound 2 and compound 4 The host material containing the compound is suitable as a host material for a material that exhibits orange to red thermally activated delayed fluorescence. In order to achieve good energy transfer, a thermal activation delay The peak wavelength of the lowest energy absorption band of a fluorescent substance and the emission peak of an exciplex The difference in energy equivalent value from the wavelength is preferably 0.2 eV or less.

[0093] The light-emitting element having the above-described configuration is capable of transferring energy to a substance exhibiting thermally activated delayed fluorescence. This is a light-emitting element with high efficiency and good luminous efficiency.

[0094] (Embodiment 2) In this embodiment mode, an example of a detailed structure of the light-emitting element described in Embodiment Mode 1 will be described with reference to FIG. The following explains this.

[0095] The light-emitting element in this embodiment mode has an EL layer made up of a plurality of layers between a pair of electrodes. In this embodiment, the light-emitting element includes a first electrode 101, a second electrode 102, and a first It is composed of an electrode 101, a second electrode 102 and an EL layer 103 provided between them. In this embodiment, the first electrode 101 functions as an anode, and the second electrode 102 functions as a cathode. In other words, the first electrode 101 is closer to the second electrode 10 A voltage was applied to the first electrode 101 and the second electrode 102 so that the potential was higher than that of the first electrode 101. In some cases, light emission is obtained.

[0096] The first electrode 101 functions as an anode, so it is made of a material having a large work function (specifically, 4.0 e V or higher) metals, alloys, conductive compounds, and mixtures thereof. Specifically, for example, indium oxide-tin oxide (ITO) is preferable. in Oxide), indium oxide-tin oxide containing silicon or silicon oxide, Indium oxide - zinc oxide, tungsten oxide and zinc oxide containing indium oxide ( These conductive metal oxide films are usually formed by sputtering. However, it may also be prepared by applying the sol-gel method. Indium oxide-zinc oxide is made by adding 1 to 20 wt% of zinc oxide to indium oxide. There are also methods for forming the film by sputtering using a target containing an oxide film. Indium oxide containing tungsten and zinc oxide (IWZO) has the following properties compared to indium oxide: The target contains 0.5 to 5 wt% of tungsten oxide and 0.1 to 1 wt% of zinc oxide. It can also be formed by sputtering using gold (Au), platinum ( Pt), Nickel (Ni), Tungsten (W), Chromium (Cr), Molybdenum (Mo) , iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or metallic materials Nitrides (for example, titanium nitride) and the like can be used. Graphene can also be used. By using a composite material described later for the layer in contact with the first electrode 101 in the EL layer 103, This allows electrode materials to be selected regardless of their work functions.

[0097] Regarding the laminated structure of the EL layer 103, the light-emitting layer 113 has the same structure as that shown in the first embodiment. As long as the above-described structure is satisfied, other layers are not particularly limited. For example, a hole injection layer, a hole transport layer, a light emitting layer, an electron It can be configured by appropriately combining a transport layer, an electron injection layer, a carrier blocking layer, an intermediate layer, etc. In this embodiment, the EL layer 103 is a hole transport layer formed by stacking the first electrode 101 in order. injection layer 111, hole transport layer 112, light emitting layer 113, electron transport layer 114, electron injection layer 115 The materials constituting each layer are specifically shown below.

[0098] The hole injection layer 111 is a layer containing a substance with high hole injection properties. Use of zinc oxide, ruthenium oxide, tungsten oxide, manganese oxide, etc. In addition, phthalocyanine (abbreviated as H2Pc) and copper phthalocyanine (abbreviated as Cu Pc), phthalocyanine compounds such as 4,4'-bis[N-(4-diphenylamino) N,N'-bis(4-phenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), [bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1' -biphenyl)-4,4'-diamine (abbreviation: DNTPD), or or poly(ethylenedioxythiophene) / poly(styrenesulfonic acid) (abbreviation: PED The hole injection layer 111 can also be formed from a polymer such as OT / PSS.

[0099] In addition, the hole injection layer 111 is formed by adding an acceptor substance to a hole transporting substance. A composite material can be used. Note that the hole transporting material may contain an acceptor material. By using a material that has the same work function as the electrode, it is possible to select the material for forming the electrode regardless of the work function of the electrode. That is, the first electrode 101 can be made of not only a material with a large work function but also a material with a low work function. Small materials can also be used. ,8-Tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TC NQ), chloranil, etc. Also included are transition metal oxides. Further examples include oxides of metals belonging to groups 4 to 8 in the periodic table. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molyb oxide Tungsten oxide, manganese oxide, and rhenium oxide are preferred due to their high electron-accepting properties. Among them, molybdenum oxide is particularly stable in the air, has low hygroscopicity, and is easy to handle. preferable.

[0100] As hole transporting substances used in composite materials, aromatic amine compounds, carbazole derivatives, Species such as organic compounds, aromatic hydrocarbons, and polymeric compounds (oligomers, dendrimers, polymers, etc.) Various organic compounds can be used. It is preferable that the organic compound has high hole transport properties. -6 cm 2 / Vs or later In the following, the hole transport in the composite material is Specific examples of organic compounds that can be used as transport materials are listed below.

[0101] For example, the aromatic amine compound is N,N'-di(p-tolyl)-N,N'-diphenyl Phenyl-p-phenylenediamine (DTDPPA), 4,4'-bis[N-(4- Diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N ,N'-Bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl Phenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD), 1,3 ,5-Tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B), etc.

[0102] Specific examples of carbazole derivatives that can be used in composite materials include 3-[N- (9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazol 3,6-bis[N-(9-phenylcarbazole-3 -yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2) , 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino] -9-phenylcarbazole (abbreviation: PCzPCN1), etc.

[0103] Other carbazole derivatives that can be used in composite materials 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-carbazole (abbreviation: CzPA), 1,4-biphenyl bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene, etc. can be used.

[0104] In addition, examples of aromatic hydrocarbons that can be used in the composite material include 2-tert -butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 2- tert-Butyl-9,10-di(1-naphthyl)anthracene, 9,10-bis(3, 5-diphenylphenyl)anthracene (abbreviation: DPPA), 2-tert-butyl-9 ,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA), 9,1 0-Di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene 2-tert-butylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene (abbreviation: t-BuAn th), 9,10-bis(4-methyl-1-naphthyl)anthracene (abbreviation: DMNA) , 2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene 9,10-bis[2-(1-naphthyl)phenyl]anthracene, 2,3,6,7- Tetramethyl-9,10-di(1-naphthyl)anthracene, 2,3,6,7-tetramethyl 9,10-di(2-naphthyl)anthracene, 9,9'-bianthryl, 10,1 0'-Diphenyl-9,9'-bianthryl, 10,10'-bis(2-phenylphenyl) 10,10'-bis[(2,3,4,5,6-pentafluorophenyl)-9,9'-bianthryl, (phenyl)phenyl]-9,9'-bianthryl, anthracene, tetracene, rubrene, perylene, 2,5,8,11-tetra(tert-butyl)perylene, etc. In addition, pentacene, coronene, etc. can also be used. -6 cm 2 / Vs or more and aromatic hydrocarbons with carbon numbers of 14 to 42 are used. It is more preferable that

[0105] The aromatic hydrocarbons that can be used in the composite material may have a vinyl skeleton. Examples of aromatic hydrocarbons having a vinyl group include 4,4'-bis(2,2- Diphenylvinyl)biphenyl (abbreviation: DPVBi), 9,10-bis[4-(2,2- diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA), and the like.

[0106] In addition, poly(N-vinylcarbazole) (abbreviation: PVK) and poly(4-vinyltriphenyl ether) Nylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenyl amino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide]( abbreviation: PTPDMA), poly[N,N'-bis(4-butylphenyl)-N,N'-bis Polymer compounds such as [(phenyl)benzidine] (abbreviation: Poly-TPD) can also be used. can.

[0107] By forming a hole injection layer, the hole injection property is improved, and a light emitting device with a low driving voltage can be obtained. It is possible to obtain an optical element.

[0108] The hole transport layer 112 is a layer containing a substance with a hole transport property. For example, 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1, 1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4',4''-tris (N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4',4 ''-Tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), 4,4'-bis[N-(spiro-9,9'-bifluorene-2 -yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'- (9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), etc. The aromatic amine compounds described here have high hole transport properties and can be used. , mainly 10 -6 cm 2 The composite material has a hole mobility of 1 / Vs or more. The organic compounds listed as hole transporting materials in the material can also be used for the hole transport layer 112. In addition, poly(N-vinylcarbazole) (abbreviated as PVK) and poly(4-vinyl carbazole) Polymer compounds such as phenyltriphenylamine (PVTPA) can also be used. The layer containing the hole transporting substance may be a single layer or may be two or more layers containing the above substance. It may also be a laminate.

[0109] The light-emitting layer 113 is a layer containing a light-emitting substance, a first organic compound, and a second organic compound. The light-emitting layer 113 has the structure described in the first embodiment. The light emitting element can be a light emitting element with very good luminous efficiency. For the configuration, please refer to the description in the first embodiment.

[0110] The light-emitting layer 113 having the above-described structure can be formed by co-evaporation using a vacuum evaporation method or by forming a mixed solution. Fabricated by forming a film using inkjet, spin coating, dip coating, etc. It is possible.

[0111] The electron transport layer 114 is a layer containing a substance with electron transport properties. For example, tris(8-quinolinol) Tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum Almq3, bis(10-hydroxybenzo[h]quinolinato)beri Sodium (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenyl) quinoline or benzoquinoline skeletons, such as aluminum benzoate (abbreviation: BAlq) The layer is made of a metal complex having a structure. bis[2-(2-hydroxybenzoyl)benzoxazolato]zinc (abbreviation: Zn(BOX)2), Oxazoles such as [(oxyphenyl)benzothiazolato]zinc (abbreviation: Zn(BTZ)2) Metal complexes having thiazole-based or thiazole-based ligands can also be used. In addition, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3 ,4-oxadiazole (abbreviated as PBD) and 1,3-bis[5-(p-tert-butyl phenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7 ), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl) -1,2,4-triazole (abbreviation: TAZ), bathophenanthroline (abbreviation: BPhe n), bathocuproine (abbreviated as BCP), etc. can also be used. has high electron transport properties and is mainly -6 cm 2 / Vs or higher electron mobility The electron-transporting host material described above may be used for the electron-transporting layer 114.

[0112] The electron transport layer 114 may be not only a single layer, but also a layer of two or more layers made of the above-mentioned materials. It may also be layered.

[0113] Furthermore, a layer for controlling the movement of electron carriers may be provided between the electron transport layer and the light emitting layer. This is achieved by adding a small amount of a substance with high electron trapping properties to a material with high electron transport properties as described above. It is a layer that adjusts the carrier balance by suppressing the movement of electron carriers. This type of structure prevents electrons from penetrating the light-emitting layer. This is highly effective in suppressing problems that arise (for example, a reduction in the device life).

[0114] In addition, an electron injection layer 115 may be provided in contact with the second electrode 102. Examples include lithium fluoride (LiF), cesium fluoride (CsF), and calcium fluoride ( Alkali metals or alkaline earth metals such as CaF2 or their compounds can be used. For example, an alkali metal or alkali metal compound can be added to a layer made of a substance having an electron transporting property. The electron injection layer may contain earth metals or compounds thereof. As 115, an alkali metal or alkaline earth metal is contained in a layer made of a substance having an electron transport property. By using a material containing a metal, electron injection from the second electrode 102 can be performed efficiently. This is preferable because it can be

[0115] The material forming the second electrode 102 is selected from those having a small work function (specifically, 3.8 eV Metals, alloys, electrically conductive compounds, and mixtures thereof can be used. Specific examples of such cathode materials include lithium (Li) and cesium (Cs). Potash metal, as well as magnesium (Mg), calcium (Ca), and strontium (Sr) Elements belonging to Group 1 or 2 of the periodic table, such as Mg, Ag, rare earth metals such as AlLi), europium (Eu), ytterbium (Yb) and However, the second electrode 102 and the electron transport layer may be formed of a material other than the material itself. By providing an electron injection layer, it is possible to use Al, Ag, ITO, and ketone regardless of the magnitude of the work function. Various conductive materials such as indium oxide-tin oxide containing silicon or silicon oxide are used as the second These conductive materials can be used as the electrode 102. The film can be formed by a jet method, a spin coating method, or the like.

[0116] The EL layer 103 can be formed by various methods, including dry and wet methods. For example, a vacuum deposition method, an ink jet method, a spin coating method, or the like can be used. Also, each electrode or each layer may be formed using a different film formation method. .

[0117] The electrodes may also be formed by a wet method using the sol-gel method, or by a paste of a metal material. Alternatively, the film may be formed by a dry method such as sputtering or vacuum deposition. It may be formed using

[0118] The light-emitting element having the above-described structure has a first electrode 101 and a second electrode 102. A current flows due to the applied potential difference, and holes are generated in the light-emitting layer 113, which is a layer containing a light-emitting substance. The electrons and the atoms recombine to emit light. It is structured as follows.

[0119] The light is emitted through either the first electrode 101 or the second electrode 102, or both. Therefore, either the first electrode 101 or the second electrode 102 Alternatively, both electrodes may be made of a light-transmitting electrode. Only the first electrode 101 may be made of a light-transmitting electrode. When the second electrode 102 is When only the first electrode 102 is light-transmitting, emitted light is extracted through the second electrode 102. When the first electrode 101 and the second electrode 102 are both light-transmitting electrodes, the light-emitting is taken out from both the first electrode 101 and the second electrode 102.

[0120] The structure of the layers provided between the first electrode 101 and the second electrode 102 is the same as that described above. However, it is not limited to the above. The first electrode 101 and the second electrode 102 are arranged so as to suppress quenching caused by contact. A preferred configuration is one in which a light-emitting region where holes and electrons recombine is provided at a location away from 102 .

[0121] In addition, the hole transport layer and the electron transport layer in contact with the light emitting layer 113, particularly the light emitting layer 113 The carrier transport layer, which is adjacent to the region closer to the active layer, is responsible for the energy transfer from the excitons generated in the light-emitting layer. In order to suppress this, the band gap is determined by the luminescent material that constitutes the luminescent layer or the material contained in the luminescent layer. The material has a band gap larger than that of the luminescent center material. It is preferable to form

[0122] The light emitting element in this embodiment is mounted on a substrate made of glass, plastic, metal, or the like. The substrate through which the light from the light emitting element passes has high transparency in the visible light region. The order of fabrication on the substrate is stacked in order from the first electrode 101 side. Alternatively, the layers may be stacked in order from the second electrode 102 side. It is also possible to form a plurality of light emitting elements on one substrate. By manufacturing multiple light-emitting elements, it is possible to create lighting devices with separate elements and passive matrix light-emitting devices. In addition, a device can be fabricated on a substrate made of glass, plastic, etc. For example, a thin film transistor (TFT) is formed, and a light emitting element is formed on an electrode electrically connected to the TFT. This allows for the active matrix transistor to control the driving of the light emitting element by the TFT. A trix type light emitting device can be manufactured. The structure of the TFT is not particularly limited. The TFT may be a staggered type or an inverted staggered type. The material is not particularly limited, and either an amorphous semiconductor or a crystalline semiconductor may be used. In addition, the driving circuit formed on the TFT substrate can be divided into N-type and P-type TFTs. Alternatively, it may be made up of either an N-type TFT or a P-type TFT. It may be that all of these things are possible.

[0123] Note that this embodiment mode can be combined with other embodiment modes as appropriate.

[0124] (Embodiment 3) In this embodiment, a light-emitting device using the light-emitting element described in Embodiment 1 or 2 This article explains:

[0125] In this embodiment, a light-emitting element manufactured using the light-emitting element described in Embodiment 1 or 2 is The light-emitting device will be described with reference to FIG. 3. FIG. 3(A) is a top view showing the light-emitting device. 3(B) is a cross-sectional view taken along lines AB and CD in FIG. 3(A). The light emitting element 618 is controlled by a driving circuit (source line) shown by a dotted line. A driver circuit (gate line driver circuit) 601, a pixel portion 602, and a driver circuit portion (gate line driver circuit) 603 are included. Also, 604 is a sealing substrate, 625 is a drying material, and 605 is a sealing material. The inside of the box is space 607.

[0126] The lead wiring 608 is connected to the source line driver circuit 601 and the gate line driver circuit 603. The wiring is for transmitting the input signal, and the FPC (flexible printed circuit board) is the external input terminal. Video signal, clock signal, start signal, reset signal from Lint Circuit 609 Although only the FPC is shown here, this FPC has a printed circuit board. A printed wiring board (PWB) may be attached. This includes not only the device itself but also the state in which an FPC or PWB is attached to it. do.

[0127] A driving circuit portion and a pixel portion are formed on the element substrate 610. The source line driver circuit 601, which is a driving circuit section, and one pixel in the pixel section 602 are shown. .

[0128] The source line driver circuit 601 includes an n-channel TFT 623 and a p-channel TFT 62 4 is combined to form a CMOS circuit. In addition, the drive circuit is a CMOS circuit Alternatively, the substrate may be formed of a PMOS circuit or an NMOS circuit. Although the driver integrated type with the drive circuit formed on the top is shown, this is not necessarily required. It may also be formed externally rather than on the substrate.

[0129] The pixel section 602 includes a switching TFT 611, a current control TFT 612, and The pixel is formed by a plurality of pixels including a first electrode 613 electrically connected to the drain. An insulator 614 is formed to cover the end of the first electrode 613. It is formed by using a photosensitive acrylic resin film of a mold.

[0130] In order to improve the covering property, the upper end or the lower end of the insulator 614 is provided with a curvature. For example, the material of the insulator 614 is a positive photosensitive adhesive. When using krill, the radius of curvature (0.2 μm to 3 μm) is provided only at the upper end of the insulator 614. It is preferable to provide a curved surface. Alternatively, a positive photosensitive resin can be used.

[0131] An EL layer 616 and a second electrode 617 are formed on the first electrode 613. Here, the material used for the first electrode 613 functioning as an anode is a material having a work function It is desirable to use a material with a large resistance. For example, an ITO film or an insulator containing silicon indium tin oxide film, indium oxide film containing 2 to 20 wt% zinc oxide, titanium nitride film, In addition to single layer films such as chromium film, tungsten film, Zn film, and Pt film, titanium nitride and aluminum film are also available. a titanium nitride film and an aluminum-based film; A three-layer structure with a silicon film can be used. The resistance is low, good ohmic contact can be achieved, and the electrode can also function as an anode. .

[0132] The EL layer 616 can be formed by a deposition method using a deposition mask, an inkjet method, or a spin coating method. The EL layer 616 is formed by various methods such as the method of forming the EL layer 616 in accordance with the first embodiment or the second embodiment. The EL layer 616 includes other materials such as low molecular weight The compound may be a compound or a polymer compound (including an oligomer or a dendrimer).

[0133] Furthermore, a material used for the second electrode 617 formed on the EL layer 616 and functioning as a cathode is The materials used are those with a low work function (Al, Mg, Li, Ca, or their alloys or compounds). It is preferable to use a material such as an alloy of MgAg, MgIn, or AlLi. When the light generated in 6 is transmitted through the second electrode 617, the second electrode 617 is Thin metal films and transparent conductive films (ITO, indium tin oxide containing 2-20 wt% zinc oxide) It uses lamination of indium tin oxide containing indium and silicon, zinc oxide (ZnO, etc.) It's good to do that.

[0134] The first electrode 613, the EL layer 616, and the second electrode 617 form a light-emitting element 618. The light emitting element has the structure of the second embodiment. The element 602 is formed with a plurality of light emitting elements. The light-emitting element described in Embodiment 1 or 2 and the light-emitting element having other structures are Both elements may be included.

[0135] Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with a sealing material 605, A space 607 surrounded by an element substrate 610, a sealing substrate 604, and a sealing material 605 contains a light-emitting element. The space 607 is filled with a filler. In addition to being filled with an inert gas (nitrogen, argon, etc.), it is also possible to fill it with a sealing material 605. If a recess is formed in the sealing substrate and a desiccant 625 is provided there, the sealing substrate can be protected from the influence of moisture. This is a preferable configuration because it can suppress deterioration due to the temperature change.

[0136] It is preferable to use epoxy resin or glass frit for the sealing material 605. In addition, it is desirable that these materials be as impermeable to moisture and oxygen as possible. The sealing substrate 604 may be made of a glass substrate, a quartz substrate, or a FRP (Fibre Reinforced Plastic) substrate. Glass-Reinforced Plastics), PVF (Polyvinyl Fluoride ), a plastic substrate made of polyester, acrylic, or the like can be used.

[0137] As described above, a light-emitting element manufactured using the light-emitting element described in Embodiment 1 or 2 A light emitting device having such a structure can be obtained.

[0138] The light-emitting device in this embodiment includes the light-emitting element described in Embodiment 1 or 2. Since the organic EL element is used, a light emitting device having good characteristics can be obtained. The light-emitting element described in Embodiment 1 or 2 is a light-emitting element with high luminous efficiency and low power consumption. Furthermore, the light-emitting element can emit light with a low driving voltage. It is possible to obtain a light emitting device with a low driving voltage.

[0139] As described above, this embodiment mode will explain an active matrix light emitting device. However, a passive matrix type light emitting device may also be used. 4A shows a passive matrix light-emitting device manufactured by 4(B) is a cross-sectional view taken along the XY line in FIG. 4(A). On a substrate 951, an EL layer 955 is provided between an electrode 952 and an electrode 956. The end of the electrode 952 is covered with an insulating layer 953. A partition wall layer 954 is formed on the insulating layer 953. The sidewall of the partition layer 954 is provided with a thickness of 54. The partition layer 954 has a slope such that the distance between the first and second side walls becomes narrower. The cross section in the side direction is trapezoidal, and the bottom side (the side in contact with the insulating layer 953) is closer to the top side (the side in contact with the insulating layer 953). In this way, by providing the partition wall layer 954, the cross section It is possible to prevent defects in the light-emitting element due to defects such as cracks. In the optical device, the light-emitting element according to the first or second embodiment that operates at a low driving voltage may also be used. By having the element, it can be driven with low power consumption. By including the light-emitting element described in Embodiment 2, the display device can be driven with low power consumption. Cut.

[0140] In order to achieve full color display, a light emitting element must have a certain thickness so that light can be emitted to the outside of the light emitting device. A colored layer or a color conversion layer may be provided on the optical path. An example of a light-emitting device is shown in FIGS. 5(A) and 5(B). In FIG. 5(A), a substrate 1001, Undercoat insulating film 1002, gate insulating film 1003, gate electrodes 1006, 1007, 1008 , a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral portion 1042, a pixel portion 10 40, drive circuit unit 1041, first electrodes 1024W, 1024R, 1024G of light-emitting elements , 1024B, a partition wall 1025, an EL layer 1028, a second electrode 1029 of the light-emitting element, a sealing group The plate 1031, the sealing material 1032, etc. are shown. The green colored layer 1034R, the green colored layer 1034G, and the blue colored layer 1034B are provided on a transparent substrate 1033. A black layer (black matrix) 1035 may also be provided. The transparent base material 1033 on which the colored layer and the black layer are provided is fixed to the substrate 1001. The black layer is covered with an overcoat layer 1036. The light is emitted from the light-emitting layer without passing through the colored layers, and the light is emitted from the light-emitting layer without passing through the colored layers. The light that does not pass through the colored layer is white, and the light that passes through the colored layer is red, blue, and green. This means that images can be displayed in full color using four color pixels.

[0141] In the light emitting device described above, light is taken in from the substrate 1001 side on which the TFT is formed. The light emitting device has a bottom emission structure, but the light is emitted from the sealing substrate 1031 side. It may also be a light emitting device with a structure where light is extracted (top emission type). A cross-sectional view of the light-emitting device is shown in FIG. 6. In this case, a substrate 1001 that does not transmit light is used. Unlike the structure shown in FIG. 5(A), the third interlayer insulating film 1037 is formed on the electrode 1. The insulating film is formed to cover the 022. This insulating film may also serve as a flattening film.

[0142] The first electrodes 1024W, 1024R, 1024G, and 1024B of the light-emitting element are positive electrodes. The first electrode is a reflective electrode. The EL layer 1028 is By using the configuration described in the first or second embodiment, white light can be emitted.

[0143] The colored layer is provided on the optical path through which light from the light emitting element reaches the outside. In the case of a Tom emission type light emitting device, a transparent substrate 1033 is provided with colored layers 1034R and 1034R. 4G, 1034B and fixed to the substrate 1001. 5B, the colored layer is formed between the gate insulating film 1003 and the first interlayer insulating film 1020. In the case of a top emission structure as shown in FIG. A red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B) were provided. Sealing can also be performed with a sealing substrate 1031. The sealing substrate 1031 has a A black layer 1036 may be provided so as to be positioned at the center of the colored layer (red colored layer 1034R, green colored layer 1034R). The colored layer 1034G, the blue colored layer 1034B, and the black layer 1036 are overcoat layers. Therefore, the sealing substrate 1031 may be covered. Note that a light-transmitting substrate is used as the sealing substrate 1031.

[0144] When a voltage is applied between the pair of electrodes of the organic light-emitting device thus obtained, a white light-emitting region 10 In addition, by combining it with a colored layer, a red light emitting region 1044R and A blue light-emitting region 1044B and a green light-emitting region 1044G are obtained. Since the light-emitting device uses the light-emitting element described in Embodiment 1 or 2, the consumption It is possible to realize a light emitting device with low power consumption.

[0145] Although an example of full-color display using four colors, red, green, blue, and white, is shown here, the present invention is not particularly limited to this. Instead, a full color display using three colors, red, green, and blue, may be used.

[0146] This embodiment mode can be freely combined with other embodiment modes.

[0147] (Fourth embodiment) In this embodiment, the light-emitting element described in Embodiment 1 or 2 is used as a lighting device. An example of use will be described with reference to Fig. 7. Fig. 7(B) is a top view of the lighting device, and Fig. 7(A) is a This is a cross-sectional view taken along line ef in FIG. 7(B).

[0148] The lighting device of this embodiment is a first light-transmitting substrate 400 that serves as a support. The first electrode 401 is formed on the substrate 401. This corresponds to the first electrode 101 in the figure.

[0149] An auxiliary electrode 402 is provided on the first electrode 401. In this embodiment, Since an example in which light is extracted from the electrode 401 side has been shown, the first electrode 401 is made of a light-transmitting material. The auxiliary electrode 402 is designed to compensate for the low conductivity of the light-transmitting material. The high resistance of the first electrode 401 causes a voltage drop in the light-emitting surface. The auxiliary electrode 402 has a function of suppressing uneven brightness. The electrode is formed using a material having a higher conductivity than the electrode, and preferably a material having a higher conductivity such as aluminum. It is preferable to form the auxiliary electrode 402 using a material having a high resistance. It is preferable that the surface other than the part to be removed is covered with an insulating layer. This is to suppress light emission from the upper part of the auxiliary electrode 402, which cannot be detected, and to reduce reactive current and improve power efficiency. This is to prevent a decrease in the efficiency. A pad 412 may be formed to supply a voltage to the

[0150] An EL layer 403 is formed on the first electrode 401 and the auxiliary electrode 402. 3 has the configuration described in the first or second embodiment. The EL layer 403 is located closer to the first electrode 401 in plan view than the first electrode 401. By forming the electrode 401 a little larger, it is possible to prevent a short circuit between the first electrode 401 and the second electrode 404. This is a preferable configuration because it can also play the role of an insulating layer.

[0151] The second electrode 404 is formed to cover the EL layer 403. Alternatively, it corresponds to the second electrode 102 in the second embodiment and has a similar configuration. In this state, light is emitted from the first electrode 401 side, so the second electrode 404 is It is preferable that the second electrode is made of a material with a high refractive index. 404 is connected to pad 412 to supply voltage.

[0152] As described above, the first electrode 401, the EL layer 403, and the second electrode 404 (and the auxiliary electrode 402) The lighting device described in this embodiment mode has a light-emitting element having a light-emitting efficiency. Since the light emitting element has a high efficiency, the lighting device in this embodiment is a lighting device with low power consumption. In addition, since the light-emitting element is a highly reliable light-emitting element, The lighting device according to the embodiment can be a highly reliable lighting device.

[0153] The light emitting element having the above structure is fixed to a sealing substrate 407 using sealing materials 405 and 406. The lighting device is completed by bonding and sealing the sealing materials 405 and 406. Also, a desiccant can be mixed into the inner sealing material 406, This allows the material to adsorb moisture, leading to improved reliability.

[0154] The pad 412, the first electrode 401, and a part of the auxiliary electrode 402 are covered with a sealing material 405. By extending it outside 406, it can be used as an external input terminal. An IC chip 420 equipped with a converter or the like may be provided on the board.

[0155] As described above, the lighting device according to the present embodiment uses the EL element according to the first or second embodiment. Since the light-emitting element is included, the lighting device can consume less power. This allows the lighting device to be driven at a low voltage. can be done.

[0156] (Embodiment 5) In this embodiment, a light-emitting element including the light-emitting element described in Embodiment 1 or 2 is Examples of electronic devices will be described. The light-emitting element described in Embodiment 1 or 2 This light-emitting element has high efficiency and reduced power consumption. The electronic device may be an electronic device having a light-emitting section with reduced power consumption. In addition, the light-emitting element described in Embodiment 1 or 2 is a light-emitting element with low driving voltage. Therefore, it is possible to make electronic devices with a low driving voltage.

[0157] As an electronic device to which the light-emitting element is applied, for example, a television set (television or television) (also called revision receivers), monitors for computers, digital cameras, digital Video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices) ), portable game machines, personal digital assistants, audio playback devices, large game machines such as pachinko machines, etc. Specific examples of these electronic devices are listed below.

[0158] 8A shows an example of a television device. The television device includes a housing 710 A display unit 7103 is built into the housing 1. In this case, a stand 7105 is used to hold the housing The display unit 7103 can display images. The display portion 7103 includes the light-emitting element described in Embodiment 1 or 2. The light emitting elements are arranged in a box shape. The light emitting elements are light emitting elements with good light emitting efficiency. Furthermore, it is possible to provide a light emitting element with a low driving voltage. Therefore, the display unit 7 made up of the light emitting element can be The television device having the 103 can be a television device with reduced power consumption. It is also possible to provide a television device with a low driving voltage. This makes it possible to provide a highly user-friendly television device.

[0159] The television device can be operated using the operation switches on the housing 7101 or a separate remote control. This can be done by the remote control device 7110. This allows you to control the channel and volume, and the image displayed on the display unit 7103 In addition, the remote control operation device 7110 can be operated. A display portion 7107 for displaying information output from the

[0160] The television device is assumed to be equipped with a receiver, modem, etc. It can receive television broadcasts and can also communicate by wire or wireless via a modem. By connecting to a network, you can send and receive data in one direction (sender to receiver) or two directions (sender to receiver). It is also possible to communicate information between the recipient and the receiver, or between receivers themselves.

[0161] FIG. 8(B1) 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. This computer uses the light emitting element described in the first or second embodiment as a base. The display portion 7203 is fabricated by arranging the pixels in a pixel-like manner. The computer may have a form as shown in FIG. 8(B2). The computer in FIG. 8(B2) , a keyboard 7204, and a pointing device 7206 are replaced with a second display unit 721. The second display portion 7210 is a touch panel type. Input is performed by operating the input display displayed on the input unit 7210 with a finger or a special pen. The second display portion 7210 can display not only input images but also other images. The display unit 7203 may also be a touch panel. The screen is connected by a hinge, which can cause scratches or breakage when storing or transporting the device. The light emitting element has good luminous efficiency and can prevent troubles such as damage. Therefore, the display portion 7203 including the light-emitting element can be used as a light-emitting element. A computer having the above may be a reduced power computer.

[0162] FIG. 8C shows a portable gaming machine, which is composed of two housings, a housing 7301 and a housing 7302. The housing 7301 is connected by a connecting portion 7303 so as to be openable and closable. A display unit manufactured by arranging the light-emitting elements described in embodiment 1 or embodiment 2 in a matrix. A display unit 7305 is incorporated in the housing 7302. The portable gaming machine shown in FIG. 8(C) also includes a speaker unit 7306, 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 , including the function of measuring or detecting odor or infrared rays), microphone 7312) Of course, the configuration of the portable gaming machine is not limited to the above, and the display unit 73 The display portion 7304 and / or the display portion 7305 may be It is sufficient to use a display unit made by arranging light-emitting elements in a matrix, and other accessories The portable gaming machine shown in FIG. 8(C) can be configured with a recording medium. It has the function of reading out the programs or data stored in the device and displaying them on the display, and it also has the function of reading out the programs or data stored in the device and displaying them on the display, It has the function of sharing information with the mobile gaming machine by wireless communication. The functions of the belt-type gaming machine are not limited to these, and the machine may have a variety of functions. A portable game machine having such a display portion 7304 has a light-emitting element used in the display portion 7304. Since the device has good luminous efficiency, it is a portable gaming machine with reduced power consumption. In addition, the light-emitting element used in the display portion 7304 can be driven at a low driving voltage. Therefore, it is possible to make a portable gaming machine with a low driving voltage. Since the light emitting element used in the portion 7304 is a light emitting element with a long life, it is highly reliable. It can be a portable gaming machine.

[0163] FIG. 8D shows an example of a mobile phone. The mobile phone is built in a housing 7401. In addition to the display unit 7402, operation buttons 7403, an external connection port 7404, a speaker 74 05, a microphone 7406, etc. The mobile phone is The display portion 7402 includes the light-emitting elements described in Embodiment 2 arranged in a matrix. The light-emitting element can be a light-emitting element with high luminous efficiency. It is possible to provide a light-emitting element with a small capacitance. Therefore, a mobile phone having a display portion 7402 formed of the light-emitting element It is possible to make a mobile phone with reduced power consumption. Also, it is possible to make a mobile phone with a low driving voltage. It is also possible to provide a highly reliable mobile phone.

[0164] The mobile phone shown in FIG. 8D allows a user to input information by touching the display portion 7402 with a finger or the like. In this case, the user can make a call or create an email. Such operations can be performed by touching the display portion 7402 with a finger or the like.

[0165] The screen of the display unit 7402 has three main modes. The first is a display mode that mainly displays images. The first mode is a display mode, and the second mode is an input mode that mainly inputs information such as characters. This is a display + input mode that combines two modes: display mode and input mode.

[0166] For example, when making a call or creating an email, the display unit 7402 is set to a character input mode. In this case, the screen of the display portion 7402 may be provided with a keyboard or keyboard. It is preferable to display number buttons.

[0167] In addition, the mobile phone may have a sensor inside that detects tilt, such as a gyro or acceleration sensor. By providing a device that detects the orientation of the mobile phone (portrait or landscape), the display orientation can be automatically adjusted. You can make it so that it switches.

[0168] The screen mode can be switched by touching the display unit 7402 or by using the operation button 7403 The operation is performed by switching depending on the type of image displayed on the display portion 7402. For example, if the image signal to be displayed on the display unit is video data, Switch to display mode, or switch to input mode if it is text data.

[0169] In addition, in the input mode, if there is no input by touch operation on the display unit 7402 for a certain period of time, Alternatively, the screen mode may be controlled to switch from input mode to display mode. A touch operation may be detected by an optical sensor in the display portion 7402.

[0170] The display portion 7402 can also function as an image sensor. By touching the device with your palm or fingers and capturing an image of your palm print or fingerprint, you can authenticate your identity. 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.

[0171] Note that the structure described in this embodiment mode may be obtained by appropriately combining the structures described in any of Embodiment Modes 1 to 4. They can be used in combination.

[0172] As described above, the scope of application of the light emitting device including the light emitting element according to the first embodiment or the second embodiment is as follows: The range of applications is extremely wide, and this light emitting device can be applied to electronic devices in all fields. By using the light-emitting element described in Embodiment 1 or 2, power consumption can be reduced. Therefore, electronic devices can be obtained.

[0173] FIG. 9 shows a liquid crystal display device in which the light-emitting element according to the first or second embodiment is applied to a backlight. The liquid crystal display device shown in FIG. 9 includes a housing 901, a liquid crystal layer 902, a battery 903, and a display panel 904. The LCD panel 902 includes a backlight unit 903 and a housing 904, and the LCD panel 902 includes a driver IC 905 and a In addition, a current is supplied to the backlight unit 903 through a terminal 906. are being provided.

[0174] The light-emitting element described in Embodiment 1 or 2 is applied to a backlight of a liquid crystal display device. By doing so, it is possible to obtain a backlight with reduced power consumption. This allows the creation of a surface-emitting lighting device, and also makes it possible to increase the area. It is possible to increase the area of ​​the backlight, and it is also possible to increase the area of ​​the liquid crystal display device. Since the thickness of the light-emitting device can be reduced compared to conventional devices, it is possible to make the display device thinner.

[0175] FIG. 10 shows a configuration in which the light-emitting element described in Embodiment 1 or 2 is used in an electric switch that is a lighting device. The desk lamp shown in FIG. 10 is an example of a desk lamp that is used for a lamp. The desk lamp shown in FIG. 10 is composed of a housing 2001 and a light source 2002. The light emitting device described in the fourth embodiment is used as the light source 2002 .

[0176] FIG. 11 shows an indoor lighting device 300 using the light-emitting element described in Embodiment 1 or 2. 1 and a display device 3002. Since the light-emitting element is a light-emitting element with reduced power consumption, a lighting device with reduced power consumption can be In addition, the light-emitting element described in Embodiment 1 or 2 can be formed into a large-area light-emitting element. Since this is possible, it can be used as a large-area lighting device. The light-emitting element described in Embodiment 2 is thin and can be used as a thin lighting device. This becomes possible.

[0177] The light emitting element according to the first or second embodiment is used for a windshield or a dashboard of an automobile. The invention described in the first or second embodiment can also be mounted on a display board. This shows an example of using the optical element in a windshield or dashboard of an automobile. The display 5005 is provided using the light-emitting element described in Embodiment 1 or 2. This is the display.

[0178] The display 5000 and the display 5001 are the same as those in the first embodiment or the first embodiment, which are provided on the windshield of the automobile. A display device incorporating the light-emitting device according to the second embodiment. The light-emitting element described in 2 is manufactured by using a first electrode and a second electrode that are light-transmitting. Therefore, it is possible to provide a so-called see-through display device, which allows the opposite side to be seen through. If the display is see-through, even if it is installed on the windshield of a car, it will not be visible. It can be installed without obstructing the operation. In this case, organic transistors made of organic semiconductor materials or transistors made of oxide semiconductors are used. A light-transmitting transistor such as a transistor having a light-transmitting property may be used.

[0179] The display 5002 is a light-emitting element according to the first or second embodiment provided in the pillar portion. The display 5002 displays an image captured by an imaging means provided on the vehicle body. By projecting the image, it is possible to compensate for the visibility obstructed by the pillar. The display 5003 provided on the dashboard allows the driver to see through the view obstructed by the vehicle body. By projecting images from an imaging device installed outside the vehicle, blind spots are compensated for and safety is ensured. By projecting images that complement the invisible parts, it becomes more natural. This allows for a seamless safety check.

[0180] Display 5004 and display 5005 show navigation information, speed, engine RPM, driving It can provide various information such as distance traveled, fuel level, gear status, and air conditioning settings. The display items and layout can be changed as needed to suit the user's preferences. This information can also be provided in displays 5000 to 5003. The displays 5000 to 5005 can also be used as lighting devices.

[0181] The light-emitting element described in Embodiment 1 or 2 is a light-emitting element with high emission efficiency. In addition, it is possible to make a light emitting element with low power consumption. Even if you install many large screens such as 5000 to 5005, it will not put a strain on the battery. Since the above-mentioned embodiment is less likely to cause trouble and can be used comfortably, it is preferred to use the above-mentioned embodiment 1 or 2. The light-emitting device or lighting device using the light-emitting element described above can be used as an in-vehicle light-emitting device or lighting device. It can be suitably used.

[0182] Figures 13(A) and 13(B) show an example of a foldable tablet terminal. 3(A) shows the tablet terminal in an open state, and the tablet terminal includes a housing 9630, a display unit 9631a, and a , display unit 9631b, display mode changeover switch 9034, power switch 9035, A power mode changeover switch 9036, a fastener 9033, and an operation switch 9038 are included. The tablet terminal includes the light-emitting element described in Embodiment 1 or 2. By using a light-emitting device having such a display portion 9631a and / or a light-emitting device having such a display portion 9631b, It is made by

[0183] A part of the display unit 9631a can be used as a touch panel area 9632a. By touching the operation keys 9637, data can be input. In 1a, for example, half of the area has a display function only, and the other half The display unit 963 has a touch panel function, but is not limited to this. The entire area of ​​the display unit 96 may have a touch panel function. The entire surface of 31a is displayed as a keyboard button to serve as a touch panel, and the display part 9631b is displayed. It can be used as a screen.

[0184] In addition, in the display unit 9631b, as in the display unit 9631a, The part can be used as a touch panel area 9632b. By touching the area where the display switch button 9639 is displayed with your finger or a stylus, Keyboard buttons can be displayed on the display portion 9631b.

[0185] In addition, when touching the touch panel area 9632a and the touch panel area 9632b at the same time, You can also input the character.

[0186] 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 an external switch that is detected by a light sensor built into the tablet terminal. The display brightness can be optimized according to the amount of light. In addition to sensors, other detection devices such as gyros and acceleration sensors that detect tilt may be incorporated.

[0187] FIG. 13A 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 display quality may also differ. For example, one display panel may be able to display a higher resolution image than the other. It may also be used as a rule.

[0188] FIG. 13(B) shows the tablet terminal in the closed state. Body 9630, solar cell 9633, charge / discharge control circuit 9634, battery 9635, DCD An example including a C converter 9636 is shown.

[0189] In addition, since the tablet device can be folded in half, when not in use, the case 9630 is closed. 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 for long-term use.

[0190] In addition, the tablet terminals shown in Figs. 13(A) and 13(B) can be used in various Functions that display information (still images, videos, text images, etc.), calendars, dates, or times The function to display information on the display unit, and the function to input or edit the information displayed on the display unit. It has input functions, functions to control processing using various software (programs), etc. It is possible.

[0191] The solar cell 9633 attached to the surface of the tablet terminal supplies power to the touch panel. The solar cell 9633 can be supplied 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. This can be done effectively.

[0192] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 13(B) are shown in FIG. A block diagram is shown in Fig. 13(C) and will be explained. 635, DC-DC converter 9636, converter 9638, switches SW1 to SW3 , the display unit 9631, the battery 9635, the DC-DC converter 963 6. The converter 9638 and the switches SW1 to SW3 are configured to perform the charge / discharge control shown in FIG. 13(B). This corresponds to the circuit 9634.

[0193] First, an example of operation when power is generated by the solar cell 9633 using external light will be described. The power generated by the solar cell is converted to DC voltage to charge the battery 9635. The voltage is increased or decreased by the DC converter 9636. When the power charged by the solar cell 9633 is used, 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 not displaying on the display unit 9631, turn SW1 off and SW2 on. The configuration may be such that the battery 9635 is charged.

[0194] Although the solar cell 9633 is shown as an example of a power generating means, the power generating means is not particularly Other power generating devices such as, but not limited to, piezoelectric elements (piezo elements) and thermoelectric conversion elements (Peltier elements) may also be used. The battery 9635 may be charged by wireless (contactless) means. It can be combined with a non-contact power transmission module that transmits and receives power to charge, or other charging methods. The power generating means may be omitted.

[0195] Furthermore, if the display unit 9631 is provided, a tablet terminal having the shape shown in FIG. Not limited to. [Example]

[0196] In this example, platinum (II) octaethylporphyrin was used as a substance that exhibits thermally activated delayed fluorescence. A light-emitting element according to one embodiment of the present invention using phosphorus (abbreviation: PtOEP) will be described. The substances used in this example are listed below.

[0197] [ka]

[0198] The methods for fabricating the light-emitting element 1 and the comparative light-emitting element 1 are described below.

[0199] (Method for fabricating light-emitting element 1) First, indium tin oxide containing silicon oxide (ITSO) was sputtered onto a glass substrate. The first electrode 101 was formed by a film deposition method. The area was set to 2 mm x 2 mm. Here, the first electrode 101 functions as an anode of the light-emitting element. It is an electrode that

[0200] Next, as a pretreatment for forming a light emitting element on the substrate, the substrate surface was washed with water and After baking at ℃ for 1 hour, UV ozone treatment was performed for 370 seconds.

[0201] Then, 10 -4 The substrate is placed in a vacuum deposition apparatus whose inside pressure has been reduced to about 100 Pa. After vacuum baking at 170°C for 30 minutes in the heating chamber of the device, the substrate is left for about 30 minutes. Allow to cool.

[0202] Next, the first electrode 101 is formed so that the surface on which the first electrode 101 is formed faces downward. The substrate was fixed to a substrate holder installed in a vacuum deposition apparatus, and -4 Reduced to about Pa After pressing, a film represented by the above structural formula (i) was deposited on the first electrode 101 by a vapor deposition method using resistance heating. 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) By co-evaporating DBT3P-II and molybdenum(VI) oxide, hole injection The interlayer 111 was formed with a thickness of 20 nm and consisted of DBT3P-II and molybdenum oxide. The weight ratio was adjusted to 4:2 (=DBT3P-II:molybdenum oxide). The co-evaporation method is a method of simultaneously evaporating from multiple evaporation sources in one processing chamber. is.

[0203] Next, 4-phenyl-4'-(9-phenyl-4'-phenyl- ... -phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP) The hole transport layer 112 was formed by depositing the film so as to have a thickness of 100 mm.

[0204] Furthermore, on the hole transport layer 112, 2-[3'-(dibenzoyl)-2-(3-methyl-2-phenyl)-1,3-dimethyl-2-(2-phenyl-2-phenyl)-1,3-dimethyl-2-phenyl ... [4-( ... Name: 2mDBTBPDBq-II) and 3-[N-(9- (Phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1) and platinum(II) octaethylpoly(2-methyl-2-phenylpropanol) represented by the above structural formula (v). PtOEP was mixed with 2mDBT in a weight ratio of 0.8:0.2:0.05 (=2mDBT) BPDBq-II:PCzPCA1:PtOEP) was co-evaporated to 40 nm, and light was emitted. A layer 113 was formed.

[0205] Thereafter, 2mDBTBPDBq-II was formed on the light-emitting layer 113 to a thickness of 20 nm. Furthermore, bathophenanthroline (abbreviation: BPhen) represented by the above structural formula (vi) The electron transport layer 114 was formed by depositing the compound to a thickness of 15 nm.

[0206] After the electron transport layer 114 is formed, lithium fluoride (LiF) is deposited to a thickness of 1 nm. Then, an electron injection layer 115 is formed, and finally, a second electrode 116 is formed to function as a cathode. 02, aluminum was evaporated to a film thickness of 200 nm. Light-emitting device 1 was fabricated.

[0207] In the above-described deposition process, the deposition was all carried out by resistance heating.

[0208] (Method for producing comparative light-emitting element 1) The comparative light-emitting element 1 was fabricated by replacing the light-emitting layer 113 in the light-emitting element 1 with 2mDBTBPDBq-II. , PtOEP and PtOEP were mixed at a weight ratio of 0.8:0.05 (= 2mDBTBPDBq-II:PtOEP The other materials and components were all luminescent. Same as element 1.

[0209] The light-emitting element 1 and the comparative light-emitting element 1 were placed in a glove box with a nitrogen atmosphere. The process of sealing the element with a glass substrate to prevent it from being exposed to the atmosphere (sealing material is applied around the element). After the sealing process, the initial characteristics of these light-emitting devices were The measurements were carried out at room temperature (an atmosphere maintained at 25°C).

[0210] FIG. 15 shows the current density-luminance characteristics of the light-emitting element 1 and the comparative light-emitting element 1, and FIG. 16 shows the voltage-luminance characteristics of the light-emitting element 1 and the comparative light-emitting element 1. 16, the luminance vs. current efficiency characteristics are shown in Fig. 17, the luminance vs. power efficiency characteristics are shown in Fig. 18, and the luminance vs. external The quantum efficiency characteristics are shown in FIG. 19, and the emission spectrum is shown in FIG.

[0211] As can be seen from the figure, light-emitting element 1, which utilizes energy transfer from exciplexes, exhibits a significantly higher energy transfer efficiency than the comparative light-emitting element, which does not utilize energy transfer. It was found that the device exhibited better characteristics than Photonic Device 1. Specifically, the external quantum efficiency was improved, and the As a result of the reduction in voltage, the power efficiency and current efficiency are significantly increased. The superiority of the light-emitting element 1, which is one embodiment of the present invention, was confirmed. [Example]

[0212] In this example, zinc (II) octaethylporphyrin was used as a substance exhibiting thermally activated delayed fluorescence. A light-emitting element according to one embodiment of the present invention using phosphorus (abbreviation: ZnOEP) will be described. The substances used in this example are listed below. [ka]

[0213] The methods for fabricating the light-emitting element 2 and the comparative light-emitting element 2 are described below.

[0214] (Method for manufacturing light-emitting element 2) First, indium tin oxide containing silicon oxide (ITSO) was sputtered onto a glass substrate. The first electrode 101 was formed by a film deposition method. The area was set to 2 mm x 2 mm. Here, the first electrode 101 functions as an anode of the light-emitting element. It is an electrode that

[0215] Next, as a pretreatment for forming a light emitting element on the substrate, the substrate surface was washed with water and After baking at ℃ for 1 hour, UV ozone treatment was performed for 370 seconds.

[0216] Then, 10 -4 The substrate is placed in a vacuum deposition apparatus whose inside pressure has been reduced to about 100 Pa. After vacuum baking at 170°C for 30 minutes in the heating chamber of the device, the substrate is left for about 30 minutes. Allow to cool.

[0217] Next, the first electrode 101 is formed so that the surface on which the first electrode 101 is formed faces downward. The substrate was fixed to a substrate holder installed in a vacuum deposition apparatus, and -4 Reduced to about Pa After pressing, a film represented by the above structural formula (i) was deposited on the first electrode 101 by a vapor deposition method using resistance heating. 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) By co-evaporating DBT3P-II and molybdenum(VI) oxide, hole injection The interlayer 111 was formed with a thickness of 20 nm and consisted of DBT3P-II and molybdenum oxide. The weight ratio was adjusted to 4:2 (=DBT3P-II:molybdenum oxide). The co-evaporation method is a method of simultaneously evaporating from multiple evaporation sources in one processing chamber. is.

[0218] Next, 4-phenyl-4'-(9-phenyl-4'-phenyl- ... -phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP) The hole transport layer 112 was formed by depositing the film so as to have a thickness of 100 mm.

[0219] Furthermore, on the hole transport layer 112, 2-[3'-(dibenzoyl)-2-(3-methyl-2-phenyl)-1,3-dimethyl-2-(2-phenyl-2-phenyl)-1,3-dimethyl-2-phenyl ... [4-( ... (designation: 2mDBTBPDBq-II) and N,N'-bis(2-methyl-2-propanol) represented by the above structural formula (vii). (9-phenyl-9H-carbazol-3-yl)-N,N'-diphenyl-spiro-9 ,9'-bifluorene-2,7-diamine (abbreviation: PCA2SF) and the above structural formula (vi ii) and zinc (II) octaethylporphyrin (abbreviation: ZnOEP) represented by Amount ratio 0.8:0.2:0.01(=2mDBTBPDBq-II:PCA2SF:ZnO The light-emitting layer 113 was formed by co-evaporation to a thickness of 40 nm so as to form a layer of EP.

[0220] Thereafter, 2mDBTBPDBq-II was formed on the light-emitting layer 113 to a thickness of 20 nm. Furthermore, bathophenanthroline (abbreviation: BPhen) represented by the above structural formula (vi) The electron transport layer 114 was formed by depositing the compound to a thickness of 10 nm.

[0221] After the electron transport layer 114 is formed, lithium fluoride (LiF) is deposited to a thickness of 1 nm. Then, an electron injection layer 115 is formed, and finally, a second electrode 116 is formed to function as a cathode. 02, aluminum was evaporated to a film thickness of 200 nm. Light-emitting device 2 was fabricated.

[0222] In the above-described deposition process, the deposition was all carried out by resistance heating.

[0223] (Method for producing comparative light-emitting element 2) The comparative light-emitting element 2 was fabricated by replacing the light-emitting layer 113 in the light-emitting element 2 with 2mDBTBPDBq-II. , ZnOEP, and a weight ratio of 1:0.01 (=2mDBTBPDBq-II:ZnOEP) The other materials and configurations are all light-emitting elements. Same as 2.

[0224] The light-emitting element 2 and the comparative light-emitting element 2 were placed in a glove box with a nitrogen atmosphere. The process of sealing the element with a glass substrate to prevent it from being exposed to the atmosphere (sealing material is applied around the element). After the sealing process, the initial characteristics of these light-emitting devices were The measurements were carried out at room temperature (an atmosphere maintained at 25°C).

[0225] FIG. 21 shows the current density-luminance characteristics of the light-emitting element 2 and the comparative light-emitting element 2, and FIG. 22 shows the voltage-luminance characteristics of the light-emitting element 2 and the comparative light-emitting element 2. 22, the luminance vs. current efficiency characteristics are shown in Fig. 23, the luminance vs. power efficiency characteristics are shown in Fig. 24, and the luminance vs. external The quantum efficiency characteristics are shown in FIG. 25, and the emission spectrum is shown in FIG.

[0226] As can be seen from the figure, light-emitting element 2, which utilizes energy transfer from exciplexes, exhibits a significantly higher energy transfer efficiency than the comparative light-emitting element, which does not utilize energy transfer. It was found that the device exhibited better characteristics than Photonic Device 2. Specifically, the external quantum efficiency was improved, and the As a result of the reduction in voltage, the power efficiency and current efficiency are significantly increased. The superiority of the light-emitting element 2, which is one embodiment of the light-emitting element 1, was confirmed. [Explanation of symbols]

[0227] 10 electrodes 11 electrodes 101 first electrode 102 second electrode 103 EL layer 111 Hole injection layer 112 Hole transport layer 113 Light-emitting layer 113Ec exciplex 114 Electron transport layer 115 Electron injection layer 400 boards 401 First electrode 402 Auxiliary electrode 403 EL layer 404 Second electrode 405 Sealing material 406 Sealing material 407 Sealing substrate 412 Pad 420 IC chip 601 Driver circuit section (source line driver circuit) 602 Pixel section 603 Drive circuit section (gate line drive circuit) 604 Sealing substrate 605 Sealing material 607 Space 608 Wiring 609 FPC (Flexible Printed Circuit) 610 Element substrate 611 Switching TFT 612 Current Control TFT 613 First electrode 614 Insulators 616 EL layer 617 Second electrode 618 Light-emitting element 623 n-channel TFT 624 p-channel TFT 625 Dry material 901 Case 902 Liquid crystal layer 903 Backlight Unit 904 Case 905 Driver IC 906 terminal 951 PCB 952 Electrode 953 Insulation Layer 954 Partition layer 955 EL layer 956 Electrode 1001 board 1002 Undercoat insulating film 1003 Gate insulating film 1006 Gate electrode 1007 Gate electrode 1008 gate electrode 1020 First interlayer insulating film 1021 Second interlayer insulating film 1022 Electrode First electrode of 1024W light emitting element 1024R First electrode of light-emitting element 1024G First electrode of light-emitting element 1024B First electrode of light-emitting element 1025 Bulkhead 1028 EL layer 1029 Second electrode of light-emitting element 1031 Sealing substrate 1032 Sealing material 1033 Transparent substrate 1034R Red color layer 1034G Green color layer 1034B Blue color layer 1035 Black layer (black matrix) 1036 Overcoat layer 1037 Third interlayer insulating film 1040 pixel section 1041 Drive circuit section 1042 Periphery 1044W white light emission area 1044R Red light area 1044B Blue light emitting area 1044G Green light emitting area 2001 Case 2002 light source 3001 Lighting equipment 5000 display 5001 display 5002 display 5003 display 5004 display 5005 display 7101 Housing 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 7210 Second display unit 7301 Housing 7302 Housing 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 7401 Housing 7402 Display section 7403 Operation button 7404 External connection port 7405 Speaker 7406 Microphone 7400 mobile phone 9033 Fasteners 9034 Switch 9035 Power Switch 9036 Switch 9038 Operation switch 9630 chassis 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. An energy donor material used together with a substance that exhibits thermally activated delayed fluorescence, comprising: a first organic compound and a second organic compound that forms an exciplex with the first organic compound; the first organic compound is a π-electron-deficient heteroaromatic compound or a metal complex, the second organic compound is a π-electron-rich heteroaromatic compound or a compound having an aromatic amine skeleton, an energy donor material, wherein the difference between the energy equivalent value of the peak wavelength of the longest wavelength absorption band of the substance exhibiting thermally activated delayed fluorescence and the energy equivalent value of the peak wavelength of emission from the exciplex is 0.2 eV or less.

2. An energy donor material used together with a substance that exhibits thermally activated delayed fluorescence, comprising: a first organic compound and a second organic compound that forms an exciplex with the first organic compound; the first organic compound is a π-electron-deficient heteroaromatic compound or a metal complex, the second organic compound is a π-electron-rich heteroaromatic compound or a compound having an aromatic amine skeleton, an energy donor material in which the longest wavelength absorption band of the substance exhibiting thermally activated delayed fluorescence overlaps with the emission of the exciplex;

3. An energy donor material capable of transferring energy to a substance exhibiting thermally activated delayed fluorescence, a first organic compound and a second organic compound that forms an exciplex with the first organic compound; the first organic compound is a π-electron-deficient heteroaromatic compound or a metal complex, the second organic compound is a π-electron-rich heteroaromatic compound or a compound having an aromatic amine skeleton, an energy donor material, wherein the difference between the energy equivalent value of the peak wavelength of the longest wavelength absorption band of the substance exhibiting thermally activated delayed fluorescence and the energy equivalent value of the peak wavelength of emission from the exciplex is 0.2 eV or less.

4. An energy donor material capable of transferring energy to a substance exhibiting thermally activated delayed fluorescence, a first organic compound and a second organic compound that forms an exciplex with the first organic compound; the first organic compound is a π-electron-deficient heteroaromatic compound or a metal complex, the second organic compound is a π-electron-rich heteroaromatic compound or a compound having an aromatic amine skeleton, an energy donor material in which the longest wavelength absorption band of the substance exhibiting thermally activated delayed fluorescence overlaps with the emission of the exciplex;

5. A host material used together with a substance that exhibits thermally activated delayed fluorescence, a first organic compound and a second organic compound that forms an exciplex with the first organic compound; the first organic compound is a π-electron-deficient heteroaromatic compound or a metal complex, the second organic compound is a π-electron-rich heteroaromatic compound or a compound having an aromatic amine skeleton, a host material, wherein the difference between the energy equivalent value of the peak wavelength of the longest wavelength absorption band of the substance exhibiting thermally activated delayed fluorescence and the energy equivalent value of the peak wavelength of emission from the exciplex is 0.2 eV or less.

6. A host material used together with a substance that exhibits thermally activated delayed fluorescence, a first organic compound and a second organic compound that forms an exciplex with the first organic compound; the first organic compound is a π-electron-deficient heteroaromatic compound or a metal complex, the second organic compound is a π-electron-rich heteroaromatic compound or a compound having an aromatic amine skeleton, a host material in which the longest wavelength absorption band of the substance exhibiting thermally activated delayed fluorescence overlaps with the emission of the exciplex;

7. A host material capable of transferring energy to a substance exhibiting thermally activated delayed fluorescence, a first organic compound and a second organic compound that forms an exciplex with the first organic compound; the first organic compound is a π-electron-deficient heteroaromatic compound or a metal complex, the second organic compound is a π-electron-rich heteroaromatic compound or a compound having an aromatic amine skeleton, a host material, wherein the difference between the energy equivalent value of the peak wavelength of the longest wavelength absorption band of the substance exhibiting thermally activated delayed fluorescence and the energy equivalent value of the peak wavelength of emission from the exciplex is 0.2 eV or less.

8. A host material capable of transferring energy to a substance exhibiting thermally activated delayed fluorescence, a first organic compound and a second organic compound that forms an exciplex with the first organic compound; the first organic compound is a π-electron-deficient heteroaromatic compound or a metal complex, the second organic compound is a π-electron-rich heteroaromatic compound or a compound having an aromatic amine skeleton, a host material in which the longest wavelength absorption band of the substance exhibiting thermally activated delayed fluorescence overlaps with the emission of the exciplex;

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