Light-emitting element

Abstract

To provide a light-emitting device with high external quantum efficiency and long life. . The light-emitting device has a light-emitting layer containing a guest material and a host material between a pair of electrodes, The emission spectrum of the host material overlaps with the absorption spectrum of the guest material, and the excitation energy of the host material The present invention provides a light-emitting device in which the host emits phosphorescence when the excitation energy of the guest material is converted into the excitation energy of the host. The overlap of the emission spectrum of the material and the absorption spectrum of the guest material is utilized to Since energy transfer from the organic compound to the guest material is smooth, the light-emitting device has high energy transfer efficiency. Therefore, a light-emitting device with high external quantum efficiency can be realized.

Description

[Technical Field]

[0001] Organic electroluminescence (EL) phenomenon This relates to light-emitting elements (hereinafter also referred to as organic EL elements) that utilize [a specific technology / technology]. [Background technology]

[0002] Research and development of organic EL elements is actively underway. The basic structure of an organic EL element is a pair This device has a layer containing a luminescent organic compound (hereinafter also referred to as the luminescent layer) sandwiched between electrodes, and is thin. Features include lightweight design, high-speed response to input signals, and the ability to operate at low DC voltage. Therefore, it is attracting attention as a next-generation flat panel display element. Displays using light-emitting elements offer superior contrast and image quality, as well as a wide viewing angle. It also has the characteristic of being a surface light source. Furthermore, because organic EL elements are surface light sources, the back of a liquid crystal display Applications as a light source for lights and illuminations are also being considered.

[0003] The light-emitting mechanism of organic EL elements is carrier-injection type. That is, a light-emitting layer is sandwiched between electrodes. By applying a voltage, electrons and holes injected from the electrodes recombine. When a light-emitting substance enters an excited state, it emits light when it returns to its ground state. In terms of state types, there are singlet excited states (S * ) and triplet excited state (T * ) is possible. Furthermore, the statistical generation ratio in the light-emitting element is S * :T * It can be considered that the ratio is 1:3. It is.

[0004] Luminescent organic compounds typically have a singlet ground state. Therefore, the singlet excited state... (S * The light emitted from ) is called fluorescence because it is an electronic transition between the same spin multiplicity. , triplet excited state (T * The emission from ) is due to an electronic transition between different spin multiplicities, therefore phosphorus This is called light. Here, a fluorescent compound (hereinafter referred to as a fluorescent compound) is at room temperature. Therefore, phosphorescence is usually not observed, and only fluorescence is observed. The internal quantum efficiency (the ratio of photons generated to injected carriers) in a light-emitting device The theoretical limit is S * :T * The figure of 25% is based on the fact that the ratio is 1:3.

[0005] On the other hand, if a phosphorescent compound (hereinafter referred to as a phosphorescent compound) is used, the internal quantum efficiency is 1 Theoretically, it is possible to achieve up to 00%. In other words, it is possible to obtain a higher luminescence efficiency compared to fluorescent compounds. This becomes possible. For this reason, in order to realize a highly efficient light-emitting element, phosphorescent compounds In recent years, there has been a great deal of activity in developing light-emitting devices using materials. In particular, phosphorescent compounds are... Due to their high phosphorescence quantum yield, organometallic complexes with iridium and other metals as the central metal have attracted attention. For example, Patent Document 1 describes an organometallic complex with iridium as the central metal as a phosphorescent material. It has been disclosed.

[0006] When forming the light-emitting layer of a light-emitting device using the phosphorescent compound described above, the concentration of the phosphorescent compound changes. To suppress quenching by light or triplet-triplet annihilation, in a matrix composed of other compounds... It is often formed such that the phosphorescent compound is dispersed in it. At this time, the matrix Compounds are host materials, while compounds dispersed in the matrix, such as phosphorescent compounds, are guest materials. It is called a ryo. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 00 / 70655 Pamphlet [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, generally speaking, the light extraction efficiency of organic EL elements is said to be around 20% to 30%. Therefore, considering the absorption of light by reflective electrodes and transparent electrodes, phosphorescent compounds are used. The limit of the external quantum efficiency of this light-emitting device is thought to be around 25%.

[0009] Therefore, one aspect of the present invention aims to provide a light-emitting element with high external quantum efficiency. Furthermore, one aspect of the present invention aims to provide a light-emitting element with a long lifespan. [Means for solving the problem]

[0010] One aspect of the present invention has a light-emitting layer between a pair of electrodes, comprising a guest material and a host material. The emission spectrum of the host material and the absorption spectrum of the guest material overlap, causing excitation of the host material. The energy is converted into excitation energy for the guest material, which in turn causes the light-emitting element to emit phosphorescence. be.

[0011] Furthermore, one aspect of the present invention includes a light-emitting layer between a pair of electrodes, comprising a guest material and a host material. Furthermore, the longest wavelength in the emission spectrum of the host material and the absorption spectrum of the guest material ( The absorption band on the low-energy side overlaps with the excitation energy of the host material, and the excitation energy of the guest material It is a light-emitting element that emits phosphorescence when converted into energy.

[0012] In the above light-emitting element, it is preferable that the absorption band on the longest wavelength side includes absorption derived from triplet MLCT (Metal to Ligand Charge Transfer) transition.

[0013] In the above light-emitting element, as the emission spectrum of the host material, a fluorescence spectrum is preferable.

[0014] In the above light-emitting element, the guest material is preferably an organometallic complex, and particularly preferably an iridium complex.

[0015] In the above light-emitting element, it is preferable that the difference between the energy value of the peak of the emission spectrum and the energy value of the peak of the absorption band on the lowest energy side of the absorption spectrum is within 0.3 eV.

[0016] In the above light-emitting element, it is preferable that the molar absorption coefficient of the absorption band on the longest wavelength side of the absorption spectrum is 50 00 M -1 ·cm -1 or more.

Advantages of the Invention

[0017] In one aspect of the present invention, a light-emitting element with a high external quantum efficiency can be provided. Also, in one aspect of the present invention, a light-emitting element with a long lifespan can be provided.

Brief Description of the Drawings

[0018] [Figure 1] A diagram showing the absorption spectrum and emission spectrum according to Example 1. [Figure 2] A diagram showing the configuration of the light-emitting element of the example. [Figure 3] A diagram showing the current density-luminance characteristics of the light-emitting element of Example 2. [Figure 4] A figure showing the voltage-luminance characteristics of the light-emitting element of Example 2. [Figure 5] This figure shows the brightness-current efficiency characteristics of the light-emitting element of Example 2. [Figure 6] This figure shows the luminance-external quantum efficiency characteristics of the light-emitting element of Example 2. [Figure 7] A figure showing the emission spectrum of the light-emitting element of Example 2. [Figure 8] This figure shows the results of the reliability test of the light-emitting element in Example 2. [Figure 9] This figure shows the current density-luminance characteristics of the light-emitting element of Example 3. [Figure 10] This figure shows the voltage-luminance characteristics of the light-emitting element of Example 3. [Figure 11] This figure shows the brightness-current efficiency characteristics of the light-emitting element of Example 3. [Figure 12] A figure showing the luminance-external quantum efficiency characteristics of the light-emitting element of Example 3. [Figure 13] A figure showing the emission spectrum of the light-emitting element of Example 3. [Figure 14] This figure shows the results of the reliability test of the light-emitting element of Example 3. [Figure 15] A diagram showing a light-emitting element according to one embodiment of the present invention. [Figure 16] A figure showing the absorption spectrum and emission spectrum related to Example 1. [Figure 17] A figure showing the absorption spectrum and emission spectrum related to Example 4. [Figure 18] This figure shows the current density-luminance characteristics of the light-emitting element of Example 5. [Figure 19] A diagram showing the voltage-luminance characteristics of the light-emitting element of Example 5. [Figure 20] A figure showing the brightness-current efficiency characteristics of the light-emitting element of Example 5. [Figure 21] A figure showing the luminance-external quantum efficiency characteristics of the light-emitting element of Example 5. [Figure 22] A figure showing the emission spectrum of the light-emitting element of Example 5. [Figure 23] A figure showing the absorption spectrum and emission spectrum related to Example 6. [Figure 24] This figure shows the current density-luminance characteristics of the light-emitting element of Example 7. [Figure 25] A diagram showing the voltage-luminance characteristics of the light-emitting element of Example 7. [Figure 26] A figure showing the brightness-current efficiency characteristics of the light-emitting element of Example 7. [Figure 27] A figure showing the luminance-external quantum efficiency characteristics of the light-emitting element of Example 7. [Figure 28] A figure showing the emission spectrum of the light-emitting element of Example 7. [Figure 29] This figure shows the results of the reliability test of the light-emitting element of Example 7. [Figure 30] A figure showing the absorption spectrum and emission spectrum related to Example 8. [Figure 31] A figure showing the current density-luminance characteristics of the light-emitting element of Example 9. [Figure 32] A diagram showing the voltage-luminance characteristics of the light-emitting element of Example 9. [Figure 33] A figure showing the brightness-current efficiency characteristics of the light-emitting element of Example 9. [Figure 34] A figure showing the luminance-external quantum efficiency characteristics of the light-emitting element of Example 9. [Figure 35] A figure showing the emission spectrum of the light-emitting element of Example 9. [Figure 36] This figure shows the results of the reliability test of the light-emitting element of Example 9. [Figure 37] A figure showing the absorption spectrum and emission spectrum related to Example 10. [Figure 38] A figure showing the current density-luminance characteristics of the light-emitting element of Example 11. [Figure 39] A diagram showing the voltage-luminance characteristics of the light-emitting element of Example 11. [Figure 40] A figure showing the brightness-current efficiency characteristics of the light-emitting element of Example 11. [Figure 41] A figure showing the luminance-external quantum efficiency characteristics of the light-emitting element of Example 11. [Figure 42] A figure showing the emission spectrum of the light-emitting element of Example 11. [Figure 43]A figure showing the absorption spectrum and emission spectrum related to Example 12. [Figure 44] A figure showing the current density-luminance characteristics of the light-emitting element of Example 13. [Figure 45] A diagram showing the voltage-luminance characteristics of the light-emitting element of Example 13. [Figure 46] A figure showing the brightness-current efficiency characteristics of the light-emitting element of Example 13. [Figure 47] A figure showing the luminance-external quantum efficiency characteristics of the light-emitting element of Example 13. [Figure 48] A figure showing the emission spectrum of the light-emitting element of Example 13. [Figure 49] A figure showing the absorption spectrum and emission spectrum related to Example 14. [Figure 50] A figure showing the current density-luminance characteristics of the light-emitting element of Example 15. [Figure 51] A diagram showing the voltage-luminance characteristics of the light-emitting element of Example 15. [Figure 52] This figure shows the brightness-current efficiency characteristics of the light-emitting element of Example 15. [Figure 53] A figure showing the luminance-external quantum efficiency characteristics of the light-emitting element of Example 15. [Figure 54] A figure showing the emission spectrum of the light-emitting element of Example 15. [Modes for carrying out the invention]

[0019] Embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description. Without departing from the spirit and scope of the present invention, its form and details may be modified in various ways. It will be easily understood by those skilled in the art to obtain this. Therefore, the present invention is as shown in the embodiments below. The description is not to be interpreted as being limited to the stated content. The same reference numeral is used in common across different drawings for parts that are identical or have similar functions. I will omit the explanation of that repetition.

[0020] (Embodiment 1) This embodiment describes a light-emitting element according to one aspect of the present invention.

[0021] The light-emitting element of this embodiment comprises a guest material which is a light-emitting substance and a phosphorus which disperses the guest material. The host material and the light-emitting layer are used. A phosphorescent compound is used as the guest material. For this purpose, one or more organic compounds can be used.

[0022] By dispersing the guest material within the host material, crystallization of the light-emitting layer is suppressed. This is possible. In addition, it suppresses concentration quenching caused by high concentration of guest material, and the light-emitting element This allows for increased luminous efficiency.

[0023] In this embodiment, the triplet excitation energy of the organic compound used as the host material is The T1 level of the host material is preferably higher than the T1 level of the guest material. If the T1 level of the guest material is lower than the T1 level of the guest material, the triple excitation of the guest material contributes to the emission. This is because the host material quenches the electromotive force, leading to a decrease in luminescence efficiency. be.

[0024] <Elementary processes of light emission> First, let's consider the general elementary processes of light emission in light-emitting devices that use phosphorescent compounds as guest materials. explain.

[0025] (1) When electrons and holes recombine in the guest molecule, and the guest molecule enters an excited state. (direct recombination process). (1-1) When the excited state of the guest molecule is a triplet excited state The guest molecule emits phosphorescence. (1-2) When the excited state of the guest molecule is a singlet excited state Guest molecules in a singlet excited state cross over to a triplet excited state and emit phosphorescence.

[0026] In other words, in the direct recombination process described in (1) above, the intersystem crossing efficiency and phosphorescence of the guest molecule are important. If the yield is high enough, high luminescence efficiency can be obtained. As mentioned above, the host The T1 level of the molecule is preferably higher than the T1 level of the guest molecule.

[0027] (2) When electrons and holes recombine in the host molecule, and the host molecule enters an excited state. (Energy transfer process). (2-1) When the excited state of the host molecule is a triplet excited state If the T1 level of the host molecule is higher than the T1 level of the guest molecule, the host molecule will transfer energy to the guest molecule. Excitation energy is transferred to the molecule, and the guest molecule enters a triplet excited state. The resulting guest molecule emits phosphorescence. Note that the singlet excitation energy level of the guest molecule (S Energy transfer to the S1 level is also formally possible, but in most cases, it is to the S1 level of the guest molecule. It is located at a higher energy level than the T1 level of the host molecule, and the main energy transfer is Since it's difficult to explain in detail, I'll omit it here. (2-2) When the excited state of the host molecule is a singlet excited state If the S1 level of the host molecule is higher than the S1 and T1 levels of the guest molecule, the host Excitation energy is transferred from the molecule to the guest molecule, and the guest molecule enters a singlet or triplet excited state. It enters an excited state. The guest molecule in the triplet excited state emits phosphorescence. Also, singlet excited state. The guest molecule, once in this state, crosses over to the triplet excited state and emits phosphorescence.

[0028] In other words, in the energy transfer process described in (2) above, the triplet excitation energy of the host molecule The key is how efficiently both the singlet excitation energy and the singlet excitation energy can be transferred to the guest molecule. This is the result.

[0029] <Energy transfer process> The following section will provide a detailed explanation of the energy transfer processes between molecules.

[0030] First, the following two mechanisms have been proposed for the energy transfer between molecules. So, the molecule that provides the excitation energy is the host molecule, and the molecule that receives the excitation energy is the host molecule. This is referred to as the guest molecule.

[0031] ≪Förster mechanism (dipole-dipole interaction)≫ The Förster mechanism does not require direct contact between molecules for energy transfer. Energy transfer occurs through the resonance phenomenon of dipole vibrations between the child and guest molecules. Through dynamic resonance, the host molecule transfers energy to the guest molecule, and the host molecule then... The system enters a bottom state, and the guest molecule enters an excited state. The rate constant k of the Förster mechanism. h * →g of This is shown in formula (1).

[0032]

number

[0033] In equation (1), ν represents the frequency, and f' h (ν) is the normalized host molecule Emission spectrum (When discussing energy transfer from singlet excited states, use fluorescence spectrum) When discussing energy transfer from a triplet excited state, the phosphorescent spectrum is represented, and ε g (ν ) represents the molar extinction coefficient of the guest molecule, N represents Avogadro's number, and n is the refraction of the medium. R represents the rate, R represents the intermolecular distance between the host molecule and the guest molecule, and τ represents the experimentally measured excitation state. This represents the lifetime of the state (fluorescence lifetime or phosphorescence lifetime), c represents the speed of light, and φ represents the emission quantum yield (single-particle). When discussing energy transfer from triplet excited states, the fluorescence quantum yield and the energy transfer from triplet excited states are used. When discussing energy transfer, it represents the phosphorescence quantum yield, and K 2 This involves the host molecule and the guest molecule. This is a coefficient (0-4) that represents the orientation of the transition dipole moment. Note that in the case of random orientation... K 2 = 2 / 3

[0034] Dexter mechanism (electron exchange interaction) The Dexter mechanism occurs when a host molecule and a guest molecule approach the effective contact distance where their orbitals overlap. Energy is released through the exchange of electrons between the excited host molecule and the ground-state guest molecule. —Movement occurs. Dexter mechanism's velocity constant k h * →g This is shown in equation (2).

[0035]

number

[0036] In equation (2), h is Planck's constant and K is a constant with the dimensions of energy. Yes, ν represents frequency, and f' h (ν) represents the normalized emission spectrum of the host molecule. (When discussing energy transfer from singlet excited states, use fluorescence spectra and triplet excited states.) When discussing energy transfer from, we represent the phosphorescent spectrum and ε' g (ν) is a guest This represents the normalized absorption spectrum of the molecule, where L represents the effective molecular radius and R represents the host component. This represents the intermolecular distance between the child molecule and the guest molecule.

[0037] Here, the energy transfer efficiency Φ from the host molecule to the guest molecule is present. ET This is expressed by formula (3) It is thought that this is the case. r This is the luminescence process of the host molecule (energy transfer from the singlet excited state). When discussing motion, fluorescence is used; when discussing energy transfer from the triplet excited state, phosphorescence is used. Represents the degree constant, k n This represents the rate constant for non-luminescent processes of the host molecule (thermal deactivation and intersystem crossing). τ represents the measured lifetime of the excited state of the host molecule.

[0038]

number

[0039] First, from equation (3), the energy transfer efficiency Φ ET In order to increase energy transfer The velocity constant k h * →g other competing rate constants k r +k n (=1 / τ) is by far It should be made larger. And the rate constant k of that energy transfer. h * →g To make it bigger From equations (1) and (2), it can be determined that either the Förster mechanism or the Dexter mechanism is suitable. In this structure, the emission spectrum of the host molecule (discussing energy transfer from the singlet excited state) is also discussed. When discussing the fluorescence spectrum, use fluorescence spectroscopy; when discussing energy transfer from the triplet excited state, use phosphorescence spectroscopy. It can be seen that a greater overlap between the absorption spectra of the molecule and the guest molecule is desirable.

[0040] Herein, one aspect of the present invention provides a light-emitting layer containing a guest material and a host material between a pair of electrodes. The host material's emission spectrum and the guest material's absorption spectrum overlap, and the host material The excitation energy of the material is converted into the excitation energy of the guest material, causing it to emit phosphorescence. It is an optical element.

[0041] In one aspect of the present invention, the overlap of the emission spectrum of the host material and the absorption spectrum of the guest material By utilizing this, energy transfer from the host material to the guest material is facilitated, The energy transfer efficiency is high. Therefore, in one aspect of the present invention, a light-emitting element with high external quantum efficiency is used. It is possible to have children.

[0042] Furthermore, considering the energy transfer process described above, excitation energy is transferred from the host molecule to the guest molecule. Before the host molecule can move, it deactivates by releasing its excitation energy as light or heat. If this happens, the luminous efficiency and lifespan will decrease. However, in one aspect of the present invention Because energy transfer proceeds smoothly, the deactivation of excitation energy can be suppressed. Therefore, it is possible to realize light-emitting elements with a long lifespan.

[0043] Here, the inventors have found that the emission spectrum of the host molecule and the absorption spectrum of the guest molecule are When considering overlap, the longest wavelength (lowest energy) in the absorption spectrum of the guest molecule I thought the absorption band on the side was important.

[0044] In this embodiment, a phosphorescent compound is used as the guest material. The absorption spectrum of the phosphorescent compound In Toll, the absorption band that is thought to contribute most strongly to luminescence is from the singlet ground state. The absorption wavelength corresponding to a direct transition to a triplet excited state is the wavelength and its vicinity, and it is on the longest wavelength side. This is an absorption band that appears in the emission spectrum (fluorescence spectrum and The phosphorescent spectrum overlaps with the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound. This is considered preferable.

[0045] For example, in organometallic complexes, particularly luminescent iridium complexes, the absorption band on the longest wavelength side is It often appears as a broad absorption band around 500-600 nm (of course, the emission wavelength) (Depending on the source, it may appear on the shorter wavelength side or the longer wavelength side.) This absorption band is mainly Triplet MLCT (Metal to Ligand Charge Transfer) r) It originates from the transition. However, the absorption band contains triplet π-π * transition or singlet MLCT transition Some of the absorption originates from this source, and these overlap, resulting in a blown out to the longest wavelength side of the absorption spectrum. It is thought to form a specific absorption band. Therefore, the guest material is an organometallic complex (special When using iridium complexes, the broad absorption present at the longest wavelengths is as shown. A state in which the band and the emission spectrum of the host material largely overlap is preferable.

[0046] Therefore, one aspect of the present invention relates to a light-emitting device comprising a guest material and a host material between a pair of electrodes. It has a layer and is most effective in the emission spectrum of the host material and the absorption spectrum of the guest material. The absorption band on the wavelength side overlaps, and the excitation energy of the host material becomes the excitation energy of the guest material. It is a light-emitting element that emits phosphorescence when converted to [a specific type of light].

[0047] In the above-mentioned light-emitting device, it is preferable that the absorption band includes absorption originating from a triplet MLCT transition. It seems so. The triplet MLCT excited state is the lowest triplet excited state of the phosphorescent compound, which is the guest material. Because it is in this excited state, phosphorescent compounds emit phosphorescence from this excited state. In other words, triplet MLCT Excited states have fewer deactivation processes other than luminescence, and the goal is to maximize the abundance of these excited states. This is thought to lead to high luminescence efficiency. For this reason, the triplet MLCT transition By utilizing absorption derived from this process, energy can be directly transferred from the host material to the triplet MLCT excited state. It is preferable to have many dynamic energy transfer processes. Furthermore, in the above light-emitting element... The guest material is preferably an organometallic complex, particularly an iridium complex.

[0048] Furthermore, the present inventors have found that when the host molecule is in a singlet excited state (as described in (2-2) above), three Compared to the case of a doublet excited state (as described in (2-1) above), the phosphorescent compound guest molecule We found that energy transfer is difficult to occur, and the luminescence efficiency tends to decrease, which we identified as one of the challenges. That's what caught my attention.

[0049] Fluorescent compounds are typically used as host materials, but their fluorescence lifetime (τ) is in nanoseconds. Level and very short (k r +k n (Large). This is the transition from the singlet excited state to the ground state (one This is because the transition to the multiplet is an allowed transition. From equation (3), this is due to the energy transfer effect. Rate Φ ET This works unfavorably for the host material's singlet excited state. Energy transfer to guest materials is generally less likely to occur.

[0050] However, one aspect of the present invention relates to a guest material from a singlet excited state of such a host material. The problems related to the energy transfer efficiency to the material can be overcome. That is, one aspect of the present invention The optical element has a light-emitting layer between a pair of electrodes, which includes a guest material and a host material, and the host material The fluorescence spectrum of the guest material overlaps with the longest wavelength absorption band in the guest material's absorption spectrum. It has overlap, and by utilizing the overlap, the excitation energy of the host material becomes the excitation energy of the guest material It is preferable that the material emits phosphorescence when converted to [a specific type of material].

[0051] In other words, in a light-emitting device according to one aspect of the present invention, the fluorescence spectrum of the host material is that of the guest material In the absorption spectrum, it overlaps with the absorption band on the longest wavelength side, and by utilizing this overlap, The excitation energy of the host material is converted into the excitation energy of the guest material, resulting in phosphorescence. This configuration allows for the suppression of the deactivation of the singlet excitation energy. Therefore, the single layer of the host material is thought to affect not only the efficiency but also the lifespan of the element. The deactivation of the excitation energy can be suppressed by applying one aspect of the present invention. This makes it possible to realize light-emitting elements with a long lifespan. Furthermore, the excitation energy of the host material... Ghee transfers sufficient energy to the phosphorescent compound, and fluorescence emission from the singlet excited state is virtually nonexistent. It is preferable that it is not observed.

[0052] Furthermore, in order to sufficiently overlap the emission spectrum of the host material and the absorption spectrum of the guest material This refers to the energy value of the peak in the emission spectrum and the lowest energy side of the absorption spectrum. It is preferable that the difference from the energy value of the absorption band peak is within 0.3 eV. More preferably... The voltage is either within 0.2 eV or less, and particularly preferably within 0.1 eV.

[0053] Furthermore, the Förster mechanism is crucial for energy transfer from the singlet excited state of the host material. This is considered to be the case. Taking this into consideration, from equation (1), the longest wavelength side of the guest material is The molar extinction coefficient of the absorption band is 2000M. -1 ·cm -1 The above is preferable, 5000M -1 ·cm -1 The above is preferable.

[0054] This embodiment can be combined with other embodiments as appropriate.

[0055] (Embodiment 2) In this embodiment, a light-emitting element according to one aspect of the present invention will be described with reference to Figure 15.

[0056] Figure 15(A) shows an electrode having an EL layer 102 between the first electrode 103 and the second electrode 108. This is a diagram showing an optical element. In Figure 15(A), the light-emitting element is arranged sequentially on the first electrode 103. A hole injection layer 701, a hole transport layer 702, an emissive layer 703, an electron transport layer 704, and an electron transport layer are stacked on top of each other. It consists of a sub-injection layer 705 and a second electrode 108 provided on top of it.

[0057] The first electrode 103 is a metal or alloy with a large work function (specifically, 4.0 eV or more). It is preferable to use conductive compounds and mixtures thereof. Specifically, for example, Indium tin oxide (ITO), silicon or Indium oxide-tin oxide and indium oxide-zinc oxide containing silicon oxide (Indiu Indium oxide containing (m Zinc Oxide), tungsten oxide, and zinc oxide. Examples include (IWZO). These conductive metal oxide films are usually produced by sputtering. Although it is possible to form a film using this method, it may also be fabricated using methods such as the sol-gel method. The zinc oxide film is a target made by adding 1-20 wt% zinc oxide to indium oxide. It can be formed by sputtering using a tweezers. In addition, the IWZO film is oxidized. It contains 0.5-5 wt% tungsten oxide and 0.1-1 wt% zinc oxide relative to indium. It can be formed by sputtering using a target that has been prepared. Fen, gold, platinum, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, Examples include palladium or nitrides of metallic materials (e.g., titanium nitride).

[0058] However, of the EL layer 102, the layer formed in contact with the first electrode 103 is organically formed as described later. When formed using a composite material obtained by mixing a compound and an electron acceptor. The material used for the first electrode 103 can be various metals, alloys, regardless of the magnitude of the work function. Electrically conductive compounds and mixtures thereof can be used. For example, aluminum Alloys containing um, silver, and aluminum (for example, Al-Si) can also be used.

[0059] The first electrode 103 is shaped by, for example, sputtering or deposition (including vacuum deposition). It is possible.

[0060] The second electrode 108 is made of a metal, alloy, or electrical material with a small work function (preferably 3.8 eV or less). It is preferable to form them using conductive compounds and mixtures thereof. Specifically, Elements belonging to Group 1 or Group 2 of the periodic table, i.e., alkaline elements such as lithium and cesium. Alkaline metals, calcium, alkaline earth metals such as strontium, magnesium, and this Alloys containing these (e.g., Mg-Ag, Al-Li), europium, ytterbium, etc. In addition to rare earth metals and alloys containing them, aluminum and silver can also be used.

[0061] However, the layer of the EL layer 102 that is in contact with the second electrode 108 is organically formed as described later. When using a composite material made by mixing a compound and an electron donor, the work function is large. Regardless of the quantity, indium oxide containing Al, Ag, ITO, silicon, or silicon oxide - Various conductive materials such as tin oxide can be used.

[0062] Furthermore, when forming the second electrode 108, vacuum deposition or sputtering methods may be used. This can be done. Also, when using silver paste, coating methods and inkjet methods can be used. It can be used.

[0063] The EL layer 102 has at least an emissive layer 703. A known material is present in part of the EL layer 102. It is also possible to use either low molecular weight compounds or high molecular weight compounds. Furthermore, the material forming the EL layer 102 may consist not only of organic compounds, This shall include compositions that partially contain inorganic compounds.

[0064] The EL layer 102, in addition to the light-emitting layer 703, contains a material with high hole injection potential, as shown in Figure 15(A). A hole injection layer 701 containing a hole injection layer 701, a hole transport layer 702 containing a material with high hole transport properties, and an electric An electron transport layer 704 comprising a material with high electron transport properties, comprising a material with high electron injection properties It is formed by stacking electron injection layers 705 and other elements in appropriate combinations.

[0065] The hole injection layer 701 is a layer containing a material with high hole injection potential. For example, molybdenum oxide, titanium oxide, vanadium oxide, rhenium oxide, ruthenium Chromium oxide, zirconium oxide, hafnium oxide, tantalum oxide, silver Metal oxides such as oxides, tungsten oxide, and manganese oxide can be used. Also, phthalocyanine (abbreviation: H2Pc), copper(II) phthalocyanine (abbreviation: CuPc) Phthalocyanine compounds such as the above can be used.

[0066] Furthermore, the low molecular weight organic compound 4,4',4''-tris(N,N-diphenylamino ) Triphenylamine (abbreviation: TDATA), 4,4',4''-tris[N-(3-methylamine) [Tylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), 4 ,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphen Lu (abbreviation: DPAB), 4,4'-bis(N-{4-[N'-(3-methylphenyl)- N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTP) D) 1,3,5-Tris[N-(4-diphenylaminophenyl)-N-phenylamine [N]benzene (abbreviation: DPA3B), 3-[N-(9-phenylcarbazole-3-yl) )-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3, 6-Bis[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9- Phenylcarbazole (abbreviation: PCzPCA2), 3-[N-(1-naphthyl)-N-( 9-phenylcarbazole-3-yl)amino]-9-phenylcarbazole (abbreviation: P Aromatic amine compounds such as CzPCN1 can be used.

[0067] Furthermore, polymer compounds (oligomers, dendrimers, polymers, etc.) can also be used. For example, poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyl truffle) Phenylamine (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenyl [phenylamino]phenyl-N'-phenylamino}phenyl)methacrylamide] (Abbreviation: PTPDMA), poly[N,N'-bis(4-butylphenyl)-N,N'-bi Examples of high-molecular-weight compounds include poly(phenyl)benzidine (abbreviated as Poly-TPD). Also, poly(3,4-ethylenedioxythiophene) / poly(styrenesulfonic acid) (PEDOT / PSS), Polyaniline / Poly(styrene sulfonate) (PAni / PS Polymer compounds to which acids such as S) have been added can be used.

[0068] Furthermore, as the hole injection layer 701, an organic compound and an electron acceptor are mixed. A composite material may be used. Such a composite material can be used to transform an organic compound through electron acceptors. Because holes are generated, it exhibits excellent hole injection and hole transport properties. In this case, organic compounds Ideally, the material should be one that excels at transporting the generated holes (a substance with high hole transport properties). It's nice.

[0069] Organic compounds used in composite materials include aromatic amine compounds, carbazole derivatives, and fragrances. Various compounds such as hydrocarbons and polymers (oligomers, dendrimers, polymers, etc.) Materials can be used. Furthermore, as organic compounds used in composite materials, high hole transport properties are preferred. It is preferable that it be an organic compound. Specifically, 10 -6 cm 2 Hole movement of / Vs or greater It is preferable that the material has a degree of [unclear]. However, it is not necessarily a material that has higher hole transport than electron transport. However, other materials may also be used. Below, we will discuss organic compounds that can be used in composite materials. List the specific ingredients.

[0070] Examples of organic compounds that can be used in composite materials include TDATA and MTDATA. , DPAB, DNTPD, DPA3B, PCzPCA1, PCzPCA2, PCzPCN 1,4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl Nyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4-phenyl -4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFL) Aromatic amine compounds such as P), and 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), 9-[4-(N-carbazolyl)]phenyl-10-phenylanthracene (Abbreviation: CzPA), 9-phenyl-3-[4-(10-phenyl-9-antryl)f [enyl]-9H-carbazole (abbreviation: PCzPA), 1,4-bis[4-(N-carbazole) Carbazole derivatives such as zolyl)phenyl]-2,3,5,6-tetraphenylbenzene You can use it.

[0071] Also, 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-t ert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: tB) uDBA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10- Diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene ( Abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene (Abbreviation: DMNA), 9,10-bis[2-(1-naphthyl)phenyl]-2-tert -butylanthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene , 2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene, etc. Hydrocarbon compounds can be used.

[0072] Furthermore, 2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9'-biantryl,10,10'-diphenyl-9,9'-biantryl,10, 10'-Bis(2-phenylphenyl)-9,9'-biantryl, 10,10'-bis [(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-biantryl, an Tracene, Tetracene, Rubren, Perylene, 2,5,8,11-Tetra(tert-br Chil) Perylene, Pentacene, Coronene, 4,4'-Bis(2,2-Diphenylvinyl) Biphenyl (abbreviation: DPVBi), 9,10-bis[4-(2,2-diphenylvinyl) Aromatic hydrocarbon compounds such as phenyl]anthracene (abbreviated as DPVPA) can be used. can.

[0073] Furthermore, as an electron acceptor, 7,7,8,8-tetracyano-2,3,5,6-tetraph Organic compounds such as ruoloquinodimethane (abbreviation: F4-TCNQ) and chloranil, and transition metals Examples include oxides. Also, metals belonging to groups 4 through 8 of the periodic table. Examples of oxides include vanadium oxide, niobium oxide, and tantalum oxide. chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide are used in electricity. It is preferable because it has high receptivity. In particular, molybdenum oxide is stable even in the atmosphere and absorbs It is preferable because it has low humidity and is easy to handle.

[0074] Furthermore, the polymer compounds mentioned above, such as PVK, PVTPA, PTPDMA, and Poly-TPD... Alternatively, a composite material may be formed using the electron acceptors described above and used in the hole injection layer 701.

[0075] The hole transport layer 702 is a layer containing a substance with high hole transport properties. For example, NPB, TPD, BPAFLP, 4,4'-bis[N-(9,9-dimethylfluorinated [Len-2-yl)-N-phenylamino]biphenyl (abbreviation: DFLDPBi), 4,4 '-Bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino] Aromatic amine compounds such as biphenyl (abbreviated as BSPB) can be used. The substances mentioned are mainly 10 -6 cm 2 It is a substance having a hole mobility of / Vs or greater. However, Other materials may be used as long as they have higher hole transport capabilities than electron transport. Layers containing materials with high hole transport properties include not only single layers, but also layers consisting of two or more of the above-mentioned materials. It may also be a layered structure.

[0076] Furthermore, the hole transport layer 702 contains carbazole-derived substances such as CBP, CzPA, and PCzPA. You can also use anthracene derivatives such as the body, t-BuDNA, DNA, or DPAnth. stomach.

[0077] Furthermore, the hole transport layer 702 contains PVK, PVTPA, PTPDMA, Poly-TPD, and Any polymer compound can be used.

[0078] The light-emitting layer 703 is a layer containing a light-emitting material. In this embodiment, the light-emitting layer 703 is a guest material. and host material. Multiple types of host material can be used. Specifically, the form of implementation You can refer to state 1.

[0079] As the phosphorescent compound of the guest material, organometallic complexes are preferred, and iridium complexes are particularly preferred. It seems so. Furthermore, considering the energy transfer by the Förster mechanism mentioned above, phosphorescent compounds The molar extinction coefficient of the absorption band located at the longest wavelength end of an object is 2000M -1 ·cm -1 The above Preferably, 5000M -1 ·cm -1 The above is more preferable. Such a large molar absorbance Specifically, compounds that have this number include bis(3,5-dimethyl-2-phenylpyridine Iridium(III) (Dipivaloylmethanato) (Abbreviation: [Ir(mppr-Me )2(dpm)]) and (acetylacetonate)bis(4,6-diphenylpyrimidina) Iridium(III) (abbreviation: [Ir(dppm)2(acac)]), bis(2,3) ,5-triphenylpyrazinate)(dipivaloylmethanato) iridium(III) (abbreviation) :[Ir(tppr)2(dpm)]), (acetylacetonato)bis(6-methyl-4 -Phenylpyrimidina) Iridium(III) (Abbreviation: [Ir(mppm)2(aca c)]), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidium) Sodium iridium(III) (abbreviation: [Ir(tBuppm)2(acac)]), etc. For example, [Ir(dppm)2(acac)] has a molar extinction coefficient of 50. 00M -1 ·cm -1 When using a material that reaches the above, the external quantum efficiency reaches about 30%. A highly efficient light-emitting device can be obtained.

[0080] As a host material, a compound that easily receives electrons (typically, a heterocyclic compound) and a hole A compound that easily receives (typically, an aromatic amine compound or a carbazole compound) are It is preferable to use a mixed material. By adopting such a configuration, the effect of improving the luminous efficiency and lifespan by adjusting the carrier balance between hole transport and electron transport in the light-emitting layer can be obtained. Specific examples of the host material include, for example, 2-[3-(dibenzothieno phen-4-yl)phenyl]dibenz[f,h]quinoxaline (abbreviation: 2mDBTPD Bq-II) and 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl) triphenylamine (abbreviation: PCBA1BP) mixed material, 2mDBTPDBq- II and 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol- 3-yl)triphenylamine (abbreviation: PCBNBB) mixed material, or 2- 4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenz[f, h]quinoxaline (abbreviation: 2CzPDBq-III) and PCBNBB mixed material, 2 -[4-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzo midazole (abbreviation: DBTBIm-II) and 4,4',4''-tris[N-(1-naph thyl)-N-phenylamino]triphenylamine (abbreviation: 1'-TNATA) mixed materials, etc. can be mentioned. Also, 4,4'-bis[N-(1-naphthyl)-N-phenyl Amino biphenyl (abbreviation: NPB), 4-(1-naphthyl)-4'-phenyltriphenyl ylamine (abbreviation: αNBA1BP), 2,7-bis[N-(4-diphenylaminophen yl)-N-phenylamino]-spiro-9,9'-bifluorene (abbreviation: DPA2SF ), 9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carb azole (abbreviation: PCCP), or 1'-TNATA, when mixed with 2mDBTPDBq-II can also be used as a host material. However, it is not limited to these and other known host materials can be used.

[0081] Also, by providing a plurality of light-emitting layers and making the emission colors of each layer different, it is possible to obtain light emission of a desired color for the entire light-emitting device. For example, in a light-emitting device having two light-emitting layers, if the emission color of the first light-emitting layer and the emission color of the second light-emitting layer are made complementary, it is also possible to obtain a white-light-emitting device for the entire light-emitting device. Note that complementary colors refer to the relationship between colors that become achromatic when mixed. That is, when light obtained from substances that emit complementary colors is mixed, white light emission can be obtained. Also, the same applies to a light-emitting device having three or more light-emitting layers.

[0082] The electron transport layer 704 is a layer containing a substance with high electron transport properties. Examples of substances with high electron transport properties include Alq3, tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Alm q3), bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq 2), BAlq, Zn(BOX)2, bis[2-(2-hydroxyphenyl)benzothia zole Examples include metal complexes such as zolatozinc (abbreviation: Zn(BTZ)2). Also, 2-(4 (-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazo PBD (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3 ,4-Oxadiazole-2-yl]benzene (abbreviation: OXD-7), 3-(4-ter t-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-tria Zole (abbreviation: TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl) (Phenyl)-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: p-EtTA) Z), vasophenanthroline (abbreviation: BPhen), vasocuproin (abbreviation: BCP) , 4,4'-bis(5-methylbenzoxazole-2-yl)stilbene (abbreviation: Bz Hetero-aromatic compounds such as Os can also be used. In addition, poly(2,5-pyridine- Diyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl) -co-(pyridine-3,5-diyl) (abbreviation: PF-Py), poly[(9,9-geo) Ctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl) Polymer compounds such as (abbreviated as PF-BPy) can also be used. The substances were mainly 10 -6 cm 2 It is a substance with an electron mobility of / Vs or greater. Any material with higher electron transport capabilities than those mentioned above may be used as the electron transport layer. stomach.

[0083] Furthermore, electron transport layers are not limited to single layers, but also consist of two or more layers made of the above material stacked together. It would also be acceptable to do so.

[0084] The electron injection layer 705 is a layer containing a substance with high electron injection properties. In the electron injection layer 705, rubidium, cesium, calcium, lithium fluoride, cesium fluoride, calcium fluoride, alkali metals, alkaline earth metals, or their compounds such as lithium oxide can be used. In addition, rare earth metal compounds such as erbium fluoride can be used. In addition, the substances constituting the above-described electron transport layer 704 can also be used.

[0085] Alternatively, a composite material formed by mixing an organic compound and an electron donor (donor) may be used for the electron injection layer 705. Such a composite material generates electrons in the organic compound by the electron donor, and thus has excellent electron injection properties and electron transport properties. In this case, the organic compound is preferably a material excellent in transporting the generated electrons. Specifically, for example, the substances (metal complexes, heteroaromatic compounds, etc.) constituting the above-described electron transport layer 704 can be used. As the electron donor, any substance that exhibits electron donating properties with respect to the organic compound may be used. Specifically, alkali metals, alkaline earth metals, and rare earth metals are preferable, and examples include lithium, cesium, magnesium, calcium, erbium, ytterbium, etc. In addition, alkali metal oxides and alkaline earth metal oxides are preferable, and examples include lithium oxide, calcium oxide, barium oxide, etc. In addition, Lewis bases such as magnesium oxide can be used. In addition, organic compounds such as tetrathiafulvalene (abbreviation: TTF) can also be used. Moreover, the hole injection layer 701, hole transport layer 702, light emitting layer 703, electron transport layer 704 described above mentioned above, Specifically, lithium, cesium, magnesium, calcium, erbium, ytterbium, etc. are mentioned. Also, alkali metal oxides and alkaline earth metal oxides are preferred, such as lithium oxide, calcium oxide oxide, barium oxide, etc. are mentioned. Also, Lewis bases such as magnesium oxide can be used. oxide, barium oxide, etc. are mentioned. Also, Lewis bases such as magnesium oxide can be used. In addition, organic compounds such as tetrathiafulvalene (abbreviation: TTF) can also be used. In addition, organic compounds such as tetrathiafulvalene (abbreviation: TTF) can also be used.

[0086] Note that the hole injection layer 701, hole transport layer 702, light emitting layer 703, electron transport layer 704 The electron injection layer 705 is created by vapor deposition (including vacuum deposition), inkjet, and coating, respectively. It can be formed by methods such as weaving.

[0087] As shown in Figure 15(B), the EL layer is layered between the first electrode 103 and the second electrode 108. Multiple layers may be stacked. In this case, the stacked first EL layer 800 and the second EL layer 80 It is preferable to provide a charge generation layer 803 between 1 and 1. The charge generation layer 803 is a composite of the above It can be formed from composite materials. In addition, the charge generation layer 803 is made of a layer of composite material and other materials A laminated structure with layers made of materials is also acceptable. In this case, the layers made of other materials may be electron-donating layers. Layers containing a material with high electron transport properties, or layers consisting of a transparent conductive film, can be used. Yes, it is possible. Light-emitting elements with this configuration may experience problems such as energy transfer and quenching. This makes it difficult to create light-emitting elements that combine high luminous efficiency and long lifespan, and expands the range of material choices. It is easy to do so. Furthermore, it is also possible to obtain phosphorescence emission in one EL layer and fluorescence emission in the other. It is easy. This structure can be used in combination with the EL layer structure described above.

[0088] Furthermore, by making the light-emitting color of each EL layer different, the entire light-emitting element can be desired Light emission of the color can be obtained. For example, in a light-emitting element having two EL layers, the first By making the emission color of the first EL layer and the emission color of the second EL layer complementary, the light-emitting element It is also possible to obtain a light-emitting element that emits white light as a whole. Furthermore, by using three or more EL layers The same applies to light-emitting elements.

[0089] As shown in Figure 15(C), the EL layer 102 is formed between the first electrode 103 and the second electrode 108. Between them are a hole injection layer 701, a hole transport layer 702, a light-emitting layer 703, an electron transport layer 704, and an electron injection layer. Composite material layer in contact with the input buffer layer 706, the electron relay layer 707, and the second electrode 108 It is acceptable to have 708.

[0090] By providing a composite material layer 708 in contact with the second electrode 108, the sputtering method is particularly used. When forming the second electrode 108, the damage to the EL layer 102 is reduced. Therefore, it is preferable. The composite material layer 708 is made of the aforementioned organic compound with high hole transport properties. Composite materials containing receptor-like substances can be used.

[0091] Furthermore, by providing an electron injection buffer layer 706, the composite material layer 708 and the electron transport layer 7 Because the injection barrier between 04 and 04 can be relaxed, electrons generated in the composite material layer 708 can be injected It can be easily injected into the subtransport layer 704.

[0092] The electron injection buffer layer 706 contains alkali metals, alkaline earth metals, rare earth metals, and These compounds (alkali metal compounds (oxides such as lithium oxide, halides, carbon dioxide)) (including carbonates such as lithium and cesium carbonate), alkaline earth metal compounds (oxides, halogens) Compounds of rare earth metals (including oxides, halides, and carbonates) or rare earth metal compounds (oxides, halides, and carbonates) It is possible to use materials with high electron injection capabilities, such as (including)).

[0093] Furthermore, the electron injection buffer layer 706 contains a material with high electron transport properties and a donor material, forming If performed, the mass ratio to a material with high electron transport properties should be 0.001 or more and 0.1 or less. It is preferable to add the donor substance in the following ratio. The donor substance may be an alkaline substance. Alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds) Contains oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate. ), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metals In addition to compounds of the genus (including oxides, halides, and carbonates), tetrathianaphthalene (abbreviated) Organic compounds such as (name: TTN), nickerosene, and decamethylnickerosene can also be used. It is possible. Furthermore, as a material with high electron transport properties, it is the same as the material for the electron transport layer 704 explained earlier. It can be formed using various materials.

[0094] Furthermore, an electron relay layer 707 is placed between the electron injection buffer layer 706 and the composite material layer 708. It is preferable to form the electronic relay layer 707. The electronic relay layer 707 is not necessarily required, but it is preferable to form the electronic relay layer 707. By providing a highly transportable electron relay layer 707, electrons are delivered to the electron injection buffer layer 706. It will be possible to send it quickly.

[0095] An electron relay layer 707 is sandwiched between the composite material layer 708 and the electron injection buffer layer 706. The structure consists of an acceptor material contained in the composite material layer 708 and an electron injection buffer layer 70 The structure is such that it is less likely to interact with the donor substance contained in 6 and is less likely to inhibit each other's functions. Yes, it does. Therefore, it is possible to prevent an increase in the drive voltage.

[0096] The electron relay layer 707 contains a material with high electron transport properties, and the LUM of the material with high electron transport properties The O level is related to the LUMO level of the acceptor material contained in composite material layer 708, and electron transport. It is formed so as to be between the LUMO level of the highly electron-transporting material contained in layer 704. Furthermore, if the electronic relay layer 707 contains a donor substance, the donor material of the donor substance The positions are the LUMO levels of the acceptor material in the composite material layer 708 and the electron transport layer 704 To ensure that the energy level is between that of the LUMO level of the highly electron-transporting material contained within. The LU value is the LU of the electron-transporting material contained in the electron relay layer 707. The MO level should be -5.0eV or higher, preferably -5.0eV to -3.0eV. stomach.

[0097] The electron relay layer 707 contains materials with high electron transport properties, such as phthalocyanine-based materials. It is preferable to use a metal complex having a metal-oxygen bond and an aromatic ligand.

[0098] Specifically, the phthalocyanine-based materials included in the electron relay layer 707 are CuPc and S nPc (Phthalocyanine tin(II) complex), ZnPc (Phthalocyanine zinc complex), CoPc (Cobal t(II)phthalocyanine, β-form), FePc(Phthal ocyanine Iron) and PhO-VOPc(Vanadyl 2,9,16, (23-tetraphenoxy-29H,31H-phthalocyanine) It is preferable to use either one.

[0099] As for metal complexes containing metal-oxygen bonds and aromatic ligands in the electron relay layer 707, It is preferable to use a metal complex having a metal-oxygen double bond. Because it has acceptor properties (the property of readily accepting electrons), electron transfer (give and take) is efficient. This makes it easier. Furthermore, metal complexes containing a metal-oxygen double bond are considered stable. Therefore, by using a metal complex having a metal-oxygen double bond, the light-emitting element can be made lower This allows for more stable operation using voltage.

[0100] Phthalocyanine-based materials are preferred as metal complexes having a metal-oxygen bond and an aromatic ligand. Specifically, VOPc (Vanadyl phthalocyanine), SnO Pc(Phthalocyanine tin(IV) oxide complex) and TiOPc(Phthalocyanine titanium oxide co In either of the mplex groups, the metal-oxygen double bond acts on other molecules in terms of molecular structure. It is preferable because it is easy to implement and has high acceptability.

[0101] Furthermore, among the phthalocyanine-based materials mentioned above, those having a phenoxy group are preferred. Specifically, phthalocyanine derivatives containing a phenoxy group, such as PhO-VOPc, are preferred. It seems so. Phthalocyanine derivatives containing a phenoxy group are soluble in solvents. Therefore, It has the advantage of being easy to handle when forming light-emitting elements. Also, because it is soluble in solvents, It has the advantage of making maintenance of the equipment used for film deposition easier.

[0102] The electron relay layer 707 may further contain a donor substance. The donor substance may include: Alkali metals, alkaline earth metals, rare earth metals and their compounds (alkali metal compounds) (Oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate) (including), alkaline earth metal compounds (including oxides, halides, carbonates), or rare earth In addition to metal compounds (including oxides, halides, and carbonates), tetrathianaphthalene (Abbreviation: TTN), using organic compounds such as nickerosene and decamethylnickerosene. This can be achieved. By including these donor materials in the electron relay layer 707, the electrons This makes it easier to move the light-emitting elements and allows them to be driven at lower voltages.

[0103] When the electron relay layer 707 contains a donor substance, the above-mentioned substance is an example of a substance with high electron transport properties. In addition to the materials mentioned, the acceptor levels of the acceptor material contained in the composite material layer 708 are Materials with high LUMO levels can be used. Specifically, the energy levels are as follows: , LUMO standard in the range of -5.0eV or higher, preferably -5.0eV to -3.0eV. It is preferable to use a substance having a position. Examples of such substances include perylene derivatives. Examples include nitrates and nitrogen-containing condensed aromatic compounds. Note that nitrogen-containing condensed aromatic compounds are nitrates. Because it is fixed, it is a preferred material to be used for forming the electronic relay layer 707. ru.

[0104] A specific example of a perylene derivative is 3,4,9,10-perylenetetracarboxylic acid dianhydride. Substance (abbreviation: PTCDA), 3,4,9,10-perylenetetracarboxylic bisbene Zoimidazole (abbreviation: PTCBI), N,N'-dioctyl-3,4,9,10-peri lentetracarboxylate diimide (abbreviation: PTCDI-C8H), N,N'-dihexyl- Examples include 3,4,9,10-perylenetetracarboxylate diimide (abbreviated as Hex PTC). It can be done.

[0105] Furthermore, a specific example of a nitrogen-containing condensed aromatic compound is pyrazino[2,3-f][1,10]. Phenanthroline-2,3-dicarbonitride (abbreviation: PPDN), 2,3,6,7,1 0,11-Hexacyano-1,4,5,8,9,12-Hexazatriphenylene (abbreviation) :HAT(CN)6), 2,3-diphenylpyrido[2,3-b]pyrazine (abbreviation: 2P YPR), 2,3-bis(4-fluorophenyl)pyrido[2,3-b]pyrazine (abbreviation) Examples include :F2PYPR).

[0106] In addition, 7,7,8,8-tetracyanoquinodimethane (abbreviation: TCNQ), 1,4, 5,8-Naphthalenetetracarboxylic dianhydride (abbreviation: NTCDA), perfluoropene Tasen, copper hexadecafluorophthalocyanine (abbreviation: F 16 CuPc), N,N'-bi S(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-Pentadeca Fluorescent (Loctyl)-1,4,5,8-naphthalenetetracarboxylate diimide (abbreviation: NTCD) I-C8F), 3',4'-dibutyl-5,5''-bis(dicyanomethylene)-5,5 ''-Dihydro-2,2':5',2''-Terthiophene) (abbreviation: DCMT), meta Nofullerene (e.g., [6,6]-phenyl C 61 Using methyl butyrate, etc. It is possible.

[0107] Furthermore, when the electron relay layer 707 contains a donor substance, a substance with high electron transport properties and a donor The electron relay layer 707 can be formed by methods such as co-deposition with a neutronic material.

[0108] The hole injection layer 701, hole transport layer 702, light-emitting layer 703, and electron transport layer 704 are made of the aforementioned material. Each can be formed using the appropriate ingredients.

[0109] Based on the above, the EL layer 102 of this embodiment can be fabricated.

[0110] The above-described light-emitting element is generated by the potential difference between the first electrode 103 and the second electrode 108. When an electric current flows, light is emitted as holes and electrons recombine in the EL layer 102. This light emission is emitted from either the first electrode 103 or the second electrode 108, or both. It passes through and is extracted to the outside. Therefore, either the first electrode 103 or the second electrode 108 One or both electrodes are transparent to visible light.

[0111] The layer provided between the first electrode 103 and the second electrode 108 is as described above. It is not limited to the above. To prevent extinction caused by the proximity of the light-emitting area and the metal, A luminescent region where holes and electrons recombine occurs at a location away from the first electrode 103 and the second electrode 108. Other configurations are also acceptable as long as they include designated areas.

[0112] In other words, the layered structure is not particularly limited, and materials with high electron transport and hole transport properties are available. High-quality materials, materials with high electron injection capacity, materials with high hole injection capacity, bipolar materials (electron and A layer consisting of a material with high hole transport properties, or a hole-blocking material, etc., can be freely combined with the light-emitting layer. You can combine them to create the desired configuration.

[0113] Using the light-emitting element shown in this embodiment, a passive matrix type light-emitting device and a transient We will fabricate an active-matrix type light-emitting device in which the driving of the light-emitting elements is controlled by a stator. It is possible to do so. Furthermore, the light-emitting device can be applied to electronic equipment or lighting devices, etc.

[0114] As described above, a light-emitting element according to one embodiment of the present invention can be manufactured.

[0115] This embodiment can be combined with other embodiments as appropriate. [Examples]

[0116] In this embodiment, guest material and host material that can be used in a light-emitting element according to one aspect of the present invention The details of the materials will be explained using Figures 1 and 16.

[0117] The guest material used in this example is (acetylacetonato)bis(4,6-diphenylpyryl). Iridium(III) (abbreviation: [Ir(dppm)2(acac)]), Bis (3,5-dimethyl-2-phenylpyradinate)(dipivaloylmethanato)iridium III) (abbreviation: [Ir(mppr-Me)2(dpm)]), and (acetylacetonate) Bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [I There are three types: r(mppm)2(acac). Also, the host material used in this embodiment This is 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoki Sarin (abbreviation: 2mDBTPDBq-II) and 4-phenyl-4'-(9-phenyl- Mixture with 9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP) These are the materials. The chemical formulas of the materials used in this example are shown below.

[0118] [ka]

[0119] <Measurement results of the absorption spectrum of the guest material and the emission spectrum of the host material> <Absorption Spectrum> Figures 1(A) and 16 show the ultraviolet light of a dichloromethane solution of [Ir(dppm)2(acac)]. The visible absorption spectrum (hereinafter referred to as the absorption spectrum) is shown as absorption spectrum 1. As shown, the absorption spectrum 2 is the absorption spectrum of [Ir(mppr-Me)2(dpm)] Toll, as absorption spectrum 3, the absorption spectrum of [Ir(mppm)2(acac)] It indicates a letter.

[0120] For measuring each absorption spectrum, a UV-Vis spectrophotometer (V55, manufactured by JASCO Corporation) was used. Using a type O device, a dichloromethane solution was placed in a quartz cell and measured at room temperature.

[0121] <Emission spectrum> Furthermore, Figures 1(A) and 16 show the mixed material of 2mDBTPDBq-II and PCBA1BP. The emission spectrum of the thin film is shown. In Figure 1(A), the horizontal axis is wavelength. The vertical axis shows the molar extinction coefficient ε(M) -1 ·cm -1 ) and luminescence intensity (arbitrary unit) This is shown in Figure 16. In Figure 16, the horizontal axis represents energy (eV), and the vertical axis represents the molar extinction coefficient ε. (M -1 ·cm -1 ) and luminescence intensity (in arbitrary units) are shown.

[0122] From Figures 1(A) and 16, absorption spectra 1-3 overlap with emission spectra, respectively. It was found that it has. Therefore, one of the guest materials used in this embodiment and this The light-emitting element in which the host material of the example is used together with the light-emitting layer has an emission spectrum of the host material and Energy transfer is achieved by utilizing the overlap of the absorption spectra of the guest materials. This suggests high mobility efficiency.

[0123] Here, in Figures 1(A) and 16, the longest wavelength (lowest energy) side of the absorption spectrum. The peak of the absorption band (the absorption band that is thought to strongly contribute to emission) and the peak of the emission spectrum Focus on the peaks. Of the peaks in absorption spectra 1-3, the peaks in the emission spectrum are closest to the peaks in the emission spectrum. The peak of absorption spectrum 1 is located close by, and the peak of the emission spectrum is located at the furthest point. There is a peak in the absorption spectrum 3.

[0124] Specifically, in Figure 16, the relationship between the peak of absorption spectrum 1 and the peak of emission spectrum The difference is 0.02 eV, and the difference between the peak of absorption spectrum 2 and the peak of emission spectrum is The voltage is 0.12 eV, and the difference between the peak of absorption spectrum 3 and the peak of emission spectrum is 0. The reading was 23 eV.

[0125] Next, in Figure 1(A), the absorption band on the longest wavelength (lowest energy) side of the absorption spectrum We focus on the molar extinction coefficient at the peak. Of the absorption spectra 1 to 3, absorption spectrum 1 The molar extinction coefficient is the largest, while the molar extinction coefficient of absorption spectrum 2 is the smallest.

[0126] In other words, of absorption spectra 1 to 3, absorption spectrum 1 has the longest wavelength (lowest energy). In the absorption band on the ) side, the peak is closest to the peak of the emission spectrum, and the peak is It can be said that it has the largest absorption coefficient.

[0127] From the above, it can be seen that the absorption spectrum 1 and the emission spectrum overlap particularly greatly. So, a mixed material of 2mDBTPDBq-II and PCBA1BP is used as the host material, [Ir(d A light-emitting device using ppm)2(acac) as a guest material has an emission spectrum of the mixed material By utilizing the overlap between the absorption spectra of [Ir(dppm)2(acac)], the energy Because energy is transferred, it was suggested that the energy transfer efficiency is particularly high.

[0128] ≪Calculation results of the absorption spectrum of the guest material≫ Next, the [Ir(dppm)2(acac)] and [Ir(mppr- Absorption spectra of Me)2(dpm) (Absorption spectra 1 and 2 in Figure 1(A)) We attempted to reproduce this through calculation.

[0129] Absorption of [Ir(dppm)2(acac)] and [Ir(mppr-Me)2(dpm)] To determine the emission spectrum, we use the most stable structure in the ground state of each molecule. The excitation energy and oscillator strength were determined. Then, based on the calculated oscillator strength, the absorption... We obtained the vector. The specific calculation method is described below.

[0130] Using Density Functional Theory (DFT), [Ir(dppm)2(acac)] and [Ir(m The most stable structure in the ground state of ppr-Me)2(dpm) was calculated. Furthermore, time Using the Dependency Density Functional (TD-DFT), [Ir(dppm)2(acac)] and [ The excitation energy and oscillator strength of Ir(mppr-Me)2(dpm) were determined, and this result The absorption spectrum was calculated from this. The total energy of the DFT is the potential energy, the electricity Interelectron electrostatic energy, electron kinetic energy, and complex electron-electron interactions are all included in the interaction. It is expressed as the sum of exchange-correlation energies. In DFT, the exchange-correlation interaction is expressed in terms of electron density. Because it approximates with a functional (meaning a function of functions) of the one-electron potential, the calculation is highly accurate. Yes, there is. Here, using the mixed functional B3PW91, we examine the relationship between exchange and correlation energy. The weights of each parameter were defined. Furthermore, LanL2DZ was used as the basis function for Ir atoms. 6-311 (triple split using three shorting functions for each valence orbital) The basis functions of the valence basis system were applied to atoms other than Ir. For example, in the case of a hydrogen atom, the 1s to 3s orbitals are considered, and in the case of a carbon atom, The trajectories from 1s to 4s and 2p to 4p will be taken into consideration. Furthermore, in order to improve calculation accuracy, As a polarization base system, the p-function was added to the hydrogen atom, and the d-function was added to all other atoms.

[0131] The quantum chemistry calculation program used was Gaussian 09. The calculations were performed as follows: The experiment was conducted using a high-performance computer (SGI Altix4700).

[0132] Figure 1(B) shows the absorption spectrum obtained from the calculation. For comparison, see the previously shown figure. The absorption spectrum obtained from the measurement is shown. Specifically, [Ir(dppm)2(acac The absorption spectrum obtained from the measurement of ) is shown as absorption spectrum 1, and the calculation obtained The resulting absorption spectrum is shown as absorption spectrum 1'. Also, [Ir(mppr-Me) The absorption spectrum obtained from the measurement of 2(dpm) is shown as absorption spectrum 2, and the calculation The absorption spectrum obtained from the calculation is shown as absorption spectrum 2'. In Figure 1(B), The horizontal axis represents wavelength (nm), and the vertical axis represents the molar extinction coefficient ε(M). -1 ·cm -1 ) and strong luminescence Indicates degrees (or any unit).

[0133] As shown in Figure 1(B), the shapes of absorption spectra 1 and 2 obtained from measurements and the absorption obtained from calculations are shown. The shapes of spectra 1' and 2' were almost identical. In particular, the absorption spectra 1 and 2 were observed. The following two trends were also observed in absorption spectra 1' and 2'. Trend 1) The peak wavelength of absorption spectrum 1(1') is greater than the peak wavelength of absorption spectrum 2(2'). The peak wavelength is located closer to the peak wavelength of the emission spectrum. Trend 2) The molar extinction coefficient at the peak wavelength of the longest wavelength absorption band in the absorption spectrum is Spectrum 1(1') is larger than absorption spectrum 2(2'). [Examples]

[0134] In this embodiment, a light-emitting element according to one aspect of the present invention will be described with reference to Figure 2. The chemical formulas of the materials used are shown below. Note that the chemical formulas of the materials used in the previous example are omitted.

[0135] [ka]

[0136] The following describes the method for manufacturing the light-emitting elements 1 to 3 of this embodiment.

[0137] (light-emitting element 1) First, indium tin oxide (ITSO) containing silicon oxide is spat onto the glass substrate 1100. A first electrode 1101, which functions as an anode, was formed by depositing a film using the tarting method. The film thickness was set to 110 nm, and the electrode area was set to 2 mm × 2 mm.

[0138] Next, as a pretreatment for forming light-emitting elements on the substrate 1100, the substrate surface is washed with water. After baking at 200°C for 1 hour, UV ozone treatment was performed for 370 seconds.

[0139] Then, 10 -4 A substrate is introduced into a vacuum deposition apparatus where the internal pressure is reduced to approximately Pa, and then vacuum deposition is performed. After vacuum firing at 170°C for 30 minutes in the heating chamber of the apparatus, the substrate 1100 is subjected to 3 It was allowed to cool for about 0 minutes.

[0140] Next, the first electrode 1101 is shaped so that the surface on which the first electrode 1101 is formed faces downwards. The completed substrate 1100 is fixed to a substrate holder provided inside the vacuum deposition apparatus, 10 -4 P After reducing the pressure to approximately 'a', 4-phenyl-4'-(9-phenyl Fluoren-9-yl)triphenylamine (abbreviation: BPAFLP) and molybdenum oxide ( A hole injection layer 1111 was formed by co-depositing VI). The film thickness was set to 40 nm. The ratio of BPAFLP to molybdenum oxide is 4:2 by weight (=BPAFLP:molybdenum oxide). It was adjusted to be (butene).

[0141] Next, BPAFLP is deposited on the hole injection layer 1111 to a thickness of 20 nm, A pore transport layer 1112 was formed.

[0142] Furthermore, 2mDBTPDBq-II, PCBA1BP, and [Ir(dppm)2(ac A co-deposited ac) was used to form a light-emitting layer 1113 on the hole transport layer 1112. Here, 2m Weights of DBTPDBq-II, PCBA1BP, and [Ir(dppm)2(acac)] The ratio is 0.8:0.2:0.05 (=2mDBTPDBq-II:PCBA1BP:[I The ratio was adjusted to r(dppm)²(acac). Also, the film thickness of the light-emitting layer 1113 was adjusted. The nm was set to 40nm.

[0143] Next, 2mDBTPDBq-II is deposited on the light-emitting layer 1113 to a thickness of 10 nm. A first electron transport layer 1114a was formed.

[0144] Next, bathophenanthroline (abbreviated as BPhen) is placed on the first electron transport layer 1114a. A second electron transport layer 1114b was formed by depositing a film with a thickness of 20 nm.

[0145] Furthermore, lithium fluoride (LiF) is applied to the second electron transport layer 1114b with a film thickness of 1 nm. A deposition layer was used to form an electron injection layer 1115.

[0146] Finally, a 200 nm film of aluminum is used as the second electrode 1103, which functions as the cathode. The light-emitting element 1 of this embodiment was fabricated by depositing a material to a certain thickness.

[0147] (Light-emitting element 2) The light-emitting layer 1113 of the light-emitting element 2 is composed of 2mDBTPDBq-II, PCBA1BP, and [I It was formed by co-depositing r(mppr-Me)2(dpm). Here, 2mDBT Weights of PDBq-II, PCBA1BP, and [Ir(mppr-Me)2(dpm)] The ratio is 0.8:0.2:0.05 (=2mDBTPDBq-II:PCBA1BP:[I The value was adjusted to be r(mppr-Me)2(dpm)). Also, the light-emitting layer 1113 The film thickness was set to 40 nm. Except for the light-emitting layer 1113, the components were fabricated in the same manner as the light-emitting element 1.

[0148] (light-emitting element 3) The light-emitting layer 1113 of the light-emitting element 3 is composed of 2mDBTPDBq-II, PCBA1BP, and [I It was formed by co-depositing r(mppm)2(acac). Here, 2mDBTPD The weight ratio of Bq-II, PCBA1BP, and [Ir(mppm)2(acac)] is 0. 8:0.2:0.05(=2mDBTPDBq-II:PCBA1BP:[Ir(mpp The settings were adjusted so that m)²(acac))). The film thickness of the light-emitting layer 1113 was 40 nm. Except for the light-emitting layer 1113, the light-emitting element was fabricated in the same manner as the light-emitting element 1.

[0149] In the vapor deposition process described above, resistance heating was used for all deposition steps.

[0150] Table 1 shows the element structures of the light-emitting elements 1 to 3 obtained as described above.

[0151] [Table 1]

[0152] These light-emitting elements are placed in a glove box under a nitrogen atmosphere, and the light-emitting elements are exposed to the air. After sealing the device to prevent leakage, the operating characteristics of the light-emitting element were measured. The measurements were taken at room temperature (in an atmosphere maintained at 25°C).

[0153] Figure 3 shows the current density-luminance characteristics of light-emitting elements 1 to 3. In Figure 3, the horizontal axis represents the current density. Flow density (mA / cm 2 The vertical axis represents luminance (cd / m²). 2 ) represents. Also, the voltage-luminance characteristics This is shown in Figure 4. In Figure 4, the horizontal axis represents voltage (V), and the vertical axis represents luminance (cd / m²). 2 ) represents. Furthermore, the luminance-current efficiency characteristics are shown in Figure 5. In Figure 5, the horizontal axis represents luminance (cd / m²). 2 ) vertical The axis represents current efficiency (cd / A). The luminance-external quantum efficiency characteristics are shown in Figure 6. In this example, the horizontal axis represents luminance (cd / m²). 2 The vertical axis of the graph shows the external quantum efficiency (%).

[0154] Furthermore, the brightness of light-emitting elements 1 to 3 is 1000 cd / m². 2 Voltage (V) in the vicinity ), current density (mA / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), Table 2 shows the wah efficiency (lm / W) and external quantum efficiency (%).

[0155] [Table 2]

[0156] Furthermore, the emission spectra when a current of 0.1 mA is passed through light-emitting elements 1 to 3 are shown in Figure 1. This is shown in Figure 7. In Figure 7, the horizontal axis represents wavelength (nm), and the vertical axis represents emission intensity (arbitrary units). Furthermore, as shown in Table 2, 840 cd / m² 2 The CIE chromaticity coordinate of light-emitting element 1 at this brightness is (x ,y)=(0.56,0.44), and 1000 cd / m 2 Light-emitting element 2 at this brightness level The CIE chromaticity coordinates are (x,y)=(0.55,0.45), corresponding to 940 cd / m². 2 Brightness The CIE chromaticity coordinates of the light-emitting element 3 at that time were (x,y)=(0.44,0.55). From the results, the light-emitting element 1 produced light originating from [Ir(dppm)2(acac)]. Therefore, the light-emitting element 2 obtains light emission originating from [Ir(mppr-Me)2(dpm)]. It was found that the light-emitting element 3 produced light originating from [Ir(mppm)2(acac)]. It was.

[0157] As can be seen from Table 2 and Figures 3 to 6, the light-emitting elements 1 to 3 have current efficiency and power - Both efficiency and external quantum efficiency showed high values.

[0158] In the light-emitting element of this embodiment, the host material and guest material shown in Example 1 are used as the light-emitting layer. From Example 1, the absorption spectrum of each guest material used in light-emitting element 1 to light-emitting element 3 The torrent has overlap with the emission spectrum of the host material. The light-emitting element of this embodiment has overlap Because it uses energy transfer, it has high energy transfer efficiency and high external quantum efficiency. It is thought that...

[0159] Furthermore, light-emitting element 1 exhibited a higher external quantum efficiency compared to light-emitting elements 2 and 3. In the results of Example 1, the lowest energy absorption spectrum of the guest material used in the light-emitting element 1 was In the absorption band on the energy side, the peak is closest to the peak in the emission spectrum (the difference between the peaks is (0.02 eV), and the molar extinction coefficient at the peak wavelength was the largest (>5000 M) -1 ·cm -1 ). From these, it can be seen that the light-emitting element 1 has particularly high energy transfer efficiency, so external quantum This suggests that it showed a high efficiency value.

[0160] Furthermore, the light-emitting element 2 showed a higher external quantum efficiency compared to the light-emitting element 3. (Example 1) The results showed that the peak wavelength of absorption spectrum 2 was greater than the peak wavelength of absorption spectrum 3. It was located close to the peak wavelength of the light spectrum. As a result, light-emitting element 2 and light-emitting element 3 This suggests that there was a difference in the external quantum efficiency characteristics.

[0161] From the above results, it is possible to realize a device with high external quantum efficiency by applying one aspect of the present invention. This was shown to be the case.

[0162] Next, reliability tests were performed on light-emitting elements 1 through 3. The results of the reliability tests are shown in Figure 8. In Figure 8, the vertical axis represents the normalized luminance (%) when the initial luminance is set to 100%, and the horizontal axis represents This indicates the operating time (h) of the element.

[0163] Reliability testing was performed with an initial brightness of 5000 cd / m². 2 Set to the following condition and the current density is constant for the light-emitting element. Each of the light-emitting elements 1 through 3 was driven.

[0164] The brightness of light-emitting element 1 after 470 hours was 85% of its initial brightness. In 2, the brightness after 470 hours was 72% of the initial brightness. Also, in 2 The brightness after 80 hours was 72% of the initial brightness.

[0165] From the above results, it can be shown that by applying one aspect of the present invention, a device with a long lifespan can be realized. It was shown. [Examples]

[0166] In this embodiment, a light-emitting element according to one aspect of the present invention will be described with reference to Figure 2. Since the materials used are the same as those used in the previous example, the chemical formulas are omitted.

[0167] The method for fabricating the light-emitting element 4 of this embodiment is shown below.

[0168] (Hi-ray 4) First, ITSO is deposited on the glass substrate 1100 by sputtering, and the anode is used. A first electrode 1101 capable of performing the function was formed. Its film thickness was 110 nm, and the electrode area was 2 The dimensions were set to mm x 2 mm.

[0169] Next, as a pretreatment for forming light-emitting elements on the substrate 1100, the substrate surface is washed with water. After baking at 200°C for 1 hour, UV ozone treatment was performed for 370 seconds.

[0170] Then, 10 -4 A substrate is introduced into a vacuum deposition apparatus where the internal pressure is reduced to approximately Pa, and then vacuum deposition is performed. After vacuum firing at 170°C for 30 minutes in the heating chamber of the apparatus, the substrate 1100 is subjected to 3 It was allowed to cool for about 0 minutes.

[0171] Next, the first electrode 1101 is shaped so that the surface on which the first electrode 1101 is formed faces downwards. The completed substrate 1100 is fixed to a substrate holder provided inside the vacuum deposition apparatus, 10 -4 P After reducing the pressure to approximately a, BPAFLP and molybdenum oxide (VI) are placed on the first electrode 1101. A hole injection layer 1111 was formed by co-depositing ) and B. The film thickness was set to 40 nm. The ratio of PAFLP to molybdenum oxide is 4:2 by weight (=BPAFLP:molybdenum oxide It was adjusted to become (n).

[0172] Next, BPAFLP is deposited on the hole injection layer 1111 to a thickness of 20 nm, A pore transport layer 1112 was formed.

[0173] Furthermore, 2mDBTPDBq-II, PCBA1BP, and [Ir(dppm)2(ac A co-deposited ac) was used to form a light-emitting layer 1113 on the hole transport layer 1112. Here, 2m Weights of DBTPDBq-II, PCBA1BP, and [Ir(dppm)2(acac)] The ratio is 0.8:0.2:0.1 (=2mDBTPDBq-II:PCBA1BP:[Ir The film thickness of the light-emitting layer 1113 was adjusted to (dppm)²(acac). The nm size was set to 40nm.

[0174] Next, 2mDBTPDBq-II is deposited on the light-emitting layer 1113 to a thickness of 15 nm. A first electron transport layer 1114a was formed.

[0175] Next, BPhen is deposited on the first electron transport layer 1114a to a thickness of 15 nm. This formed a second electron transport layer 1114b.

[0176] Furthermore, LiF is deposited on the second electron transport layer 1114b to a thickness of 1 nm, forming an electron injection layer. Formed 1115.

[0177] Finally, a 200 nm film of aluminum is used as the second electrode 1103, which functions as the cathode. The light-emitting element 4 of this embodiment was fabricated by depositing a material to a certain thickness.

[0178] In the vapor deposition process described above, resistance heating was used for all deposition steps.

[0179] Table 3 shows the element structure of the light-emitting element 4 obtained as described above.

[0180] [Table 3]

[0181] The light-emitting element 4 is placed in a glove box under a nitrogen atmosphere, so that the light-emitting element is not exposed to the atmosphere. After sealing the device, the operating characteristics of the light-emitting element were measured. The experiment was conducted at room temperature (in an atmosphere maintained at 25°C).

[0182] Figure 9 shows the current density-luminance characteristics of the light-emitting element 4. In Figure 9, the horizontal axis represents the current density (mA / cm 2 The vertical axis represents luminance (cd / m²). 2 This represents the voltage-luminance characteristics. Figure 10 also shows the voltage-luminance characteristics. In Figure 10, the horizontal axis represents voltage (V), and the vertical axis represents luminance (cd / m²). 2 ) represents. Also, luminance- The current efficiency characteristics are shown in Figure 11. In Figure 11, the horizontal axis represents luminance (cd / m²).2 ) and the vertical axis is electricity This represents the flow efficiency (cd / A). Furthermore, the luminance-external quantum efficiency characteristics are shown in Figure 12. The horizontal axis represents luminance (cd / m²). 2 The vertical axis of the graph shows the external quantum efficiency (%).

[0183] Furthermore, the brightness of the light-emitting element 4 is 1100 cd / m². 2 Voltage (V) and current density (mA) at that time / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), power efficiency (lm / W) The external quantum efficiency (%) is shown in Table 4.

[0184] [Table 4]

[0185] Furthermore, Figure 13 shows the emission spectrum when a current of 0.1 mA is passed through the light-emitting element 4. In figure 13, the horizontal axis represents wavelength (nm), and the vertical axis represents emission intensity (in arbitrary units). Also, in Table 4... As shown, 1100 cd / m² 2 The CIE chromaticity coordinates of light-emitting element 4 at this brightness are (x,y) = (0.57, 0.43). From this result, the light-emitting element 4 is [Ir(dppm)2 It was found that orange luminescence originating from (acac) was obtained.

[0186] As can be seen from Table 4 and Figures 9 to 12, the light-emitting element 4 has current efficiency, power efficiency, and external Each showed high quantum efficiency values. In particular, 1100 cd / m² 2 External quantum effect at brightness The rate showed an extremely high value of 31%. As mentioned earlier, the limit of external quantum efficiency is approximately 25%. It is said to be a certain degree. However, the results this time exceed that.

[0187] In the light-emitting device of this embodiment, the host material and guest material shown in Example 1 were used in the light-emitting layer. . From Example 1, the absorption spectrum of the guest material used in the light-emitting device 4 overlaps with the emission spectrum of the host material. Since the light-emitting device of this embodiment utilizes this overlap for energy transfer to occur, it is considered to have high energy transfer efficiency and high external quantum efficiency.

[0188] Also, from the results of Example 1, in the absorption band on the longest wavelength side of the absorption spectrum of the guest material used in the light-emitting device 4, the peak wavelength is close to the peak wavelength of the emission spectrum (the difference in peaks is 0.02 eV), and the molar absorption coefficient at the peak wavelength is large (>5000 M ·c -1 · m -1 ). From these, since the light-emitting device 4 has particularly high energy transfer efficiency, it is considered that the external quantum efficiency showed a value higher than ever before.

[0189] From the above results, it was shown that by applying one aspect of the present invention, a device with high external quantum efficiency can be realized .

[0190] Next, a reliability test of the light-emitting device 4 was conducted. The results of the reliability test are shown in FIG. 14. In FIG. 14 , the vertical axis represents the normalized luminance (%) when the initial luminance is 100%, and the horizontal axis represents the driving time (h) of the device.

[0191] In the reliability test, the initial luminance was set to 5000 cd / m 2 , and the light-emitting device 4 was driven under the condition of constant current density.

[0192] Regarding the luminance after 170 hours, the light-emitting device 4 maintained 95% of the initial luminance.

[0193] From the above results, it is possible to realize a highly reliable element by applying one aspect of the present invention. This was shown. [Examples]

[0194] In this embodiment, a guest material and host that can be applied to a light-emitting element according to one aspect of the present invention. An example of materials will be explained using Figure 17.

[0195] The guest material used in this embodiment is [Ir(dppm)2(acac)]. The host material used in the example is 2mDBTPDBq-II and 4,4'-bis[N-(1 It is a mixed material with [-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB). The chemical formulas of the materials used in this example are shown below. The chemical formulas of the materials used in the previous example are: Omitted.

[0196] [ka]

[0197] <Absorption Spectrum> Figure 17(A)(B) shows the ultraviolet light of a dichloromethane solution of [Ir(dppm)2(acac)]. The visible absorption spectrum (absorption spectrum a) is shown. The absorption spectrum was measured using ultraviolet-visible light. Using a spectrophotometer (V550 model, manufactured by JASCO Corporation), the dichloromethane solution (0.093) was measured. The solution ( mmol / L) was placed in a quartz cell and measured at room temperature.

[0198] <Emission spectrum> Furthermore, Figures 17(A) and (B) show the development of a thin film of a mixed material of 2mDBTPDBq-II and NPB. The light spectrum (emission spectrum a) is shown. In Figure 17(A), the horizontal axis is wavelength (nm). The vertical axis shows the molar extinction coefficient ε(M -1 ·cm-1 ) and luminescence intensity (in arbitrary units) are shown. In Figure 17(B), the horizontal axis represents energy (eV), and the vertical axis represents the molar extinction coefficient. ε(M -1 ·cm -1 ) and luminescence intensity (in arbitrary units) are shown.

[0199] From the absorption spectrum a in Figure 17(A), [Ir(dppm)2(acac)] is 520 It can be seen that it has a broad absorption band around nm. This absorption band strongly contributes to luminescence. This is thought to be an absorption zone.

[0200] The peak in emission spectrum a is thought to strongly contribute to emission in absorption spectrum a. It was found that there was a large overlap with the absorption band in absorption spectrum a. Specifically, the absorption band in absorption spectrum a The difference between the banding peak (515 nm) and the emission spectrum a peak was 0.09 eV. Therefore, the light-emitting element in which both the guest material and the host material used in this embodiment are used as the light-emitting layer, By utilizing the overlap between the emission spectrum of the host material and the absorption spectrum of the guest material, energy Because energy is transferred, it was suggested that the energy transfer efficiency is high. Therefore, external This suggests that it is possible to obtain light-emitting devices with high quantum efficiency. [Examples]

[0201] In this embodiment, a light-emitting element according to one aspect of the present invention will be described with reference to Figure 2. The chemical formulas of the materials used are shown below. Note that the chemical formulas of the materials used in the previous example are omitted.

[0202] [ka]

[0203] The method for fabricating the light-emitting element 5 of this embodiment is shown below.

[0204] (Light-emitting element 5) First, ITSO was formed into a film on the glass substrate 1100 by sputtering, and the first electrode 1101 functioning as an anode was formed. The film thickness was 110 nm, and the electrode area was 2 mm × 2 mm.

[0205] Next, as a pretreatment for forming a light-emitting element on the substrate 1100, the substrate surface was washed with water, baked at 200 °C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0206] After that, the substrate was introduced into a vacuum evaporation apparatus whose interior was evacuated to about 10 -4 Pa, and in the heating chamber of the vacuum evaporation apparatus, vacuum baking was performed at 170 °C for 30 minutes. Then, the substrate 1100 was allowed to cool for about 3 0 minutes.

[0207] Next, with the surface on which the first electrode 1101 was formed facing downward, the substrate 1100 on which the first electrode 1101 was formed was fixed to a substrate holder provided in the vacuum evaporation apparatus, and after evacuating to about 10 Pa, a hole injection layer 1111 was formed by co-evaporating 4,4’,4’’-(1,3,5-benzenetriyl)tris(dibenzothiophene) (abbreviation: DBT3P-II) and molybdenum(VI) oxide on the first electrode 1101. The film thickness was 40 n -4 P m, and the ratio of DBT3P-II to molybdenum oxide was adjusted to be 4:2 (= DBT3P- II: molybdenum oxide) by weight. m, and the ratio of DBT3P-II to molybdenum oxide was adjusted to be 4:2 (= DBT3P- II: molybdenum oxide) by weight.

[0208] Next, BPAFLP was formed into a film on the hole injection layer 1111 to a film thickness of 20 nm, and a hole transport layer 1112 was formed.

[0209] ​​​​​Furthermore, 2mDBTPDBq-II, NPB, and [Ir(dppm)2(acac)] Co-deposited the material and formed a light-emitting layer 1113 on the hole transport layer 1112. Here, 2mDBTP The weight ratio of DBq-II, NPB, and [Ir(dppm)2(acac)] is 0.8:0 .2:0.05(=2mDBTPDBq-II:NPB:[Ir(dppm)2(aca The adjustments were made so that (c)))))). Also, the film thickness of the light-emitting layer 1113 was set to 40 nm.

[0210] Next, 2mDBTPDBq-II is deposited on the light-emitting layer 1113 to a thickness of 10 nm. A first electron transport layer 1114a was formed.

[0211] Next, BPhen is deposited on the first electron transport layer 1114a to a thickness of 20 nm. This formed a second electron transport layer 1114b.

[0212] Furthermore, LiF is deposited on the second electron transport layer 1114b to a thickness of 1 nm, forming an electron injection layer. Formed 1115.

[0213] Finally, a 200 nm film of aluminum is used as the second electrode 1103, which functions as the cathode. The light-emitting element 5 of this embodiment was fabricated by depositing a material to a certain thickness.

[0214] In the vapor deposition process described above, resistance heating was used for all deposition steps.

[0215] Table 5 shows the element structure of the light-emitting element 5 obtained as described above.

[0216] [Table 5]

[0217] The light-emitting element 5 is placed in a glove box under a nitrogen atmosphere, so that the light-emitting element is not exposed to the atmosphere. After sealing the device, the operating characteristics of the light-emitting element were measured. The experiment was conducted at room temperature (in an atmosphere maintained at 25°C).

[0218] Figure 18 shows the current density-luminance characteristics of the light-emitting element 5. In Figure 18, the horizontal axis represents the current density (m³). A / cm 2 The vertical axis represents luminance (cd / m²). 2 ) represents the voltage-luminance characteristics, which are shown in Figure 19. In Figure 19, the horizontal axis represents voltage (V), and the vertical axis represents luminance (cd / m²). 2 ) represents. Also, shine The luminance-current efficiency characteristics are shown in Figure 20. In Figure 20, the horizontal axis represents luminance (cd / m²). 2 ) on the vertical axis This represents the current efficiency (cd / A). The luminance-external quantum efficiency characteristics are shown in Figure 21. Figure 21 In this graph, the horizontal axis represents luminance (cd / m²). 2 The vertical axis of the graph shows the external quantum efficiency (%).

[0219] Furthermore, the brightness of the light-emitting element 5 is 1100 cd / m². 2 Voltage (V) and current density (mA) at that time / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), power efficiency (lm / W) The external quantum efficiency (%) is shown in Table 6.

[0220] [Table 6]

[0221] Furthermore, Figure 22 shows the emission spectrum when a current of 0.1 mA is passed through the light-emitting element 5. In figure 22, the horizontal axis represents wavelength (nm), and the vertical axis represents emission intensity (in arbitrary units). Also, in Table 6... As shown, 1100 cd / m² 2The CIE chromaticity coordinates of the light-emitting element 5 at this brightness are (x,y) = (0.57, 0.43). From this result, the light-emitting element 5 is [Ir(dppm)2 It was found that orange luminescence originating from (acac) was obtained.

[0222] As can be seen from Table 6 and Figures 18 to 21, the light-emitting element 5 has current efficiency, power efficiency, and external Each of the quantum efficiencies showed high values.

[0223] The light-emitting element 5 is 2mDBTPDBq-II, NPB and [Ir(dpp) as shown in Example 4. m)2(acac)] was used as the light-emitting layer. From Example 4, 2mDBTPDBq-II and N The emission spectrum of the PB mixture is the absorption spectrum of [Ir(dppm)2(acac)] In Tor, there is a large overlap with the absorption band which is thought to contribute strongly to luminescence. The light-emitting element 5 is Because energy transfer is performed by utilizing this overlap, the energy transfer efficiency is high, and external quantum It is considered highly efficient.

[0224] Furthermore, in the results of Example 4, the longest wavelength of the absorption spectrum of the guest material used in the light-emitting element 5 was observed. In the long-range absorption band, the peak is close to the peak of the emission spectrum of the host material, and The molar extinction coefficient of the oak was large (>5000M). -1 ·cm -1 ). From these, light-emitting element Child 5 exhibited exceptionally high energy transfer efficiency, resulting in an unprecedentedly high external quantum efficiency. It is thought that...

[0225] From the above results, it is possible to realize a device with high external quantum efficiency by applying one aspect of the present invention. This was shown to be the case. [Examples]

[0226] In this embodiment, a guest material and phosphorus can be applied to a light-emitting element according to one aspect of the present invention. An example of a material will be explained using Figure 23.

[0227] The guest material used in this embodiment is bis(2,3,5-triphenylpyrazinato)(dipiva iridium(III) (abbreviation: [Ir(tppr)2(dpm)]) Yes. Also, the host material used in this embodiment is a mixture of 2mDBTPDBq-II and NPB. It is a composite material. The chemical formulas of the materials used in this example are shown below. Note that the materials used in the previous example The chemical formulas of the materials are omitted.

[0228] [ka]

[0229] <Absorption Spectrum> Figure 23(A)(B) shows the UV light of a dichloromethane solution of [Ir(tppr)2(dpm)]. The apparent absorption spectrum (absorption spectrum b) is shown. The measurement of the absorption spectrum requires ultraviolet-visible light. Using a photophotometer (V550 model, manufactured by JASCO Corporation), a dichloromethane solution (0.094 ml) was measured. The mol / L solution was placed in a quartz cell and measured at room temperature.

[0230] <Emission spectrum> Furthermore, Figures 23(A) and (B) show the development of a thin film of a mixed material of 2mDBTPDBq-II and NPB. The light spectrum (emission spectrum b) is shown. In Figure 23(A), the horizontal axis is wavelength (nm). The vertical axis shows the molar extinction coefficient ε(M -1 ·cm -1 ) and luminescence intensity (in arbitrary units) are shown. In Figure 23(B), the horizontal axis represents energy (eV), and the vertical axis represents the molar extinction coefficient. ε(M -1 ·cm-1 ) and luminescence intensity (in arbitrary units) are shown.

[0231] From the absorption spectrum b in Figure 23(A), [Ir(tppr)2(dpm)] is found at 530n It can be seen that there is a broad absorption band around m. This absorption band strongly contributes to luminescence. It is thought to be a collection area.

[0232] The peak in emission spectrum b is thought to strongly contribute to emission in absorption spectrum b. It was found that there was a large overlap with the absorption band in absorption spectrum b. Specifically, the absorption band in absorption spectrum b The difference between the banding peak (shoulder peak around 530 nm) and the emission spectrum b peak is The value was 0.01 eV. Therefore, both the guest material and the host material used in this embodiment emitted light. The light-emitting element used in the layer combines the emission spectrum of the host material with the absorption spectrum of the guest material. Because it utilizes overlap to transfer energy, it is suggested that the energy transfer efficiency is high. Therefore, it was suggested that a light-emitting device with high external quantum efficiency can be obtained. [Examples]

[0233] In this embodiment, a light-emitting element according to one aspect of the present invention will be described with reference to Figure 2. Since the materials used are the same as those used in the previous example, the chemical formulas are omitted.

[0234] The method for fabricating the light-emitting element 6 of this embodiment is shown below.

[0235] (Light-emitting element 6) The light-emitting layer 1113 of the light-emitting element 6 is composed of 2mDBTPDBq-II, NPB and [Ir(tpp It was formed by co-depositing r)2(dpm)]. Here, 2mDBTPDBq-II, The weight ratio of NPB and [Ir(tppr)2(dpm)] is 0.8:0.2:0.05( =2mDBTPDBq-II:NPB:[Ir(tppr)2(dpm)]) The following adjustments were made. The film thickness of the light-emitting layer 1113 was set to 40 nm. Except for the light-emitting layer 1113, the actual It was manufactured in the same manner as the light-emitting element 5 shown in Example 5.

[0236] Table 7 shows the element structure of the light-emitting element 6 obtained as described above.

[0237] [Table 7]

[0238] The light-emitting element 6 is placed in a glove box under a nitrogen atmosphere, so that the light-emitting element is not exposed to the atmosphere. After sealing the device, the operating characteristics of the light-emitting element were measured. The experiment was conducted at room temperature (in an atmosphere maintained at 25°C).

[0239] Figure 24 shows the current density-luminance characteristics of the light-emitting element 6. In Figure 24, the horizontal axis represents the current density (m A / cm 2 The vertical axis represents luminance (cd / m²). 2 ) represents the voltage-luminance characteristics, which are shown in Figure 25. In Figure 25, the horizontal axis represents voltage (V), and the vertical axis represents luminance (cd / m²). 2 ) represents. Also, shine The luminance-current efficiency characteristics are shown in Figure 26. In Figure 26, the horizontal axis represents luminance (cd / m²). 2 ) on the vertical axis This represents the current efficiency (cd / A). The luminance-external quantum efficiency characteristics are shown in Figure 27. Figure 27 In this graph, the horizontal axis represents luminance (cd / m²). 2 The vertical axis of the graph shows the external quantum efficiency (%).

[0240] Furthermore, the brightness of the light-emitting element 6 is 1100 cd / m². 2 Voltage (V) and current density (mA) at that time / cm 2), CIE chromaticity coordinates (x, y), current efficiency (cd / A), power efficiency (lm / W) The external quantum efficiency (%) is shown in Table 8.

[0241] [Table 8]

[0242] Furthermore, Figure 28 shows the emission spectrum when a current of 0.1 mA is passed through the light-emitting element 6. In figure 28, the horizontal axis represents wavelength (nm), and the vertical axis represents emission intensity (in arbitrary units). Also, in Table 8... As shown, 1100 cd / m² 2 The CIE chromaticity coordinates of the light-emitting element 6 at this brightness are (x,y) = (0.66, 0.34). From this result, the light-emitting element 6 is [Ir(tppr)2 It was found that red light emission originating from (dpm) was obtained.

[0243] As can be seen from Table 8 and Figures 24 to 27, the light-emitting element 6 has current efficiency, power efficiency, and external Each of the quantum efficiencies showed high values.

[0244] In the light-emitting element 6, the 2mDBTPDBq-II, NPB and [Ir(tp pr)2(dpm)] was used as the light-emitting layer. From Example 6, 2mDBTPDBq-II and N The emission spectrum of the PB mixture is the absorption spectrum of [Ir(tppr)2(dpm)] In the light-emitting element 6, there is a large overlap with the absorption band which is thought to contribute strongly to light emission. Because energy transfer is performed by utilizing this overlap, the energy transfer efficiency is high, and external quantum effects The rate is considered high.

[0245] From the above results, it is possible to realize a device with high external quantum efficiency by applying one aspect of the present invention. This was shown to be the case.

[0246] Next, a reliability test was performed on the light-emitting element 6. The results of the reliability test are shown in Figure 29. The vertical axis represents the normalized brightness (%) when the initial brightness is set to 100%, and the horizontal axis represents the drive of the element. This indicates time (h).

[0247] Reliability testing was performed with an initial brightness of 5000 cd / m². 2 Set to the following condition and the current density is constant for the light-emitting element. I drove the 6.

[0248] The brightness of the light-emitting element 6 after 98 hours was 87% of its initial brightness. From this result, the light-emitting element It was found that component 6 has a long lifespan.

[0249] From the above results, it is possible to realize a highly reliable element by applying one aspect of the present invention. This was shown. [Examples]

[0250] In this embodiment, a guest material and phosphorus can be applied to a light-emitting element according to one aspect of the present invention. An example of a material will be explained using Figure 30.

[0251] The guest material used in this embodiment is [Ir(mppm)2(acac)]. The host material used in the example is a mixture of 2mDBTPDBq-II and PCBA1BP. and 2mDBTPDBq-II and 4-(1-naphthyl)-4'-phenyltriphenyl There are two types of mixed materials of MIN (abbreviation: αNBA1BP). The chemistry of the materials used in this example. The formula is shown below. Note that the chemical formulas of the materials used in the previous example are omitted.

[0252] [ka]

[0253] <Absorption Spectrum> Figure 30(A)(B) shows the ultraviolet light of a dichloromethane solution of [Ir(mppm)2(acac)]. The visible absorption spectrum (absorption spectrum c) is shown. The absorption spectrum was measured using ultraviolet-visible light. Using a spectrophotometer (JASCO Corporation, Model V550), a dichloromethane solution (0.10 ml) was measured. The mol / L solution was placed in a quartz cell and measured at room temperature.

[0254] <Emission spectrum> Furthermore, Figures 30(A)(B) show the mixed material of 2mDBTPDBq-II and PCBA1BP. Emission spectrum of the thin film (emission spectrum c-1), and 2mDBTPDBq-II and αN Figure 30 shows the emission spectrum (emission spectrum c-2) of a thin film of the BA1BP mixed material. In (A), the horizontal axis represents wavelength (nm), and the vertical axis represents the molar extinction coefficient ε(M). -1 ·cm -1 ) and luminescence intensity (in arbitrary units) are shown. In Figure 30(B), the horizontal axis is energy ( The vertical axis shows the molar extinction coefficient ε(M) -1 ·cm -1 ) and luminescence intensity (arbitrary unit) This indicates.

[0255] From the absorption spectrum c in Figure 30(A), [Ir(mppm)2(acac)] is 490 It can be seen that it has a broad absorption band around nm. This absorption band strongly contributes to luminescence. This is thought to be an absorption zone.

[0256] The peaks in emission spectra c-1 and c-2 correspond to the absorption spectrum c. It was found that there is a large overlap with the absorption band that is thought to contribute strongly to luminescence. A light-emitting device that uses both the guest material and either of the host materials in the light-emitting layer, as used in the example, is By utilizing the overlap between the emission spectrum of the main material and the absorption spectrum of the guest material, energy Because ghee transfer occurs, it was suggested that the energy transfer efficiency is high. Therefore, external quantity This suggests that a light-emitting element with high efficiency can be obtained.

[0257] Here, emission spectrum c-2 has a shorter wavelength (higher energy) than emission spectrum c-1. It has a peak on the side. And the peak of emission spectrum c-2 is the same as emission spectrum c-1 It is located closer to the absorption band compared to the peak. Specifically, in the absorption spectrum c The peak of the absorption band (shoulder peak around 490 nm) and the emission spectrum c-1 The peak difference is 0.15 eV, and the peak of the absorption band in absorption spectrum c is (490 The difference between the shoulder peak near nm and the peak of the emission spectrum c-2 is 0.01 eV. .

[0258] The difference between the peaks of emission spectra c-1 and c-2 is PCBA1BP and αNB. This is thought to be due to the difference in the HOMO levels of A1BP. Specifically, the H of PCBA1BP The OMO level is -5.43 eV, while the HOMO level of αNBA1BP is -5.5 The value was 2 eV (both values ​​were calculated by cyclic voltammetry (CV) measurement). Compared to PCBA1BP, αNBA1BP has a lower (deeper) HOMO level, so the emission is The peak of the vector c-2 is at a shorter wavelength (higher energy) than the emission spectrum c-1. It is thought that... [Examples]

[0259] In this embodiment, a light-emitting element according to one aspect of the present invention will be described with reference to Figure 2. Since the materials used are the same as those used in the previous example, the chemical formulas are omitted.

[0260] The following describes the method for manufacturing the light-emitting element 7 and the light-emitting element 8 of this embodiment.

[0261] (light-emitting element 7) First, ITSO is deposited on the glass substrate 1100 by sputtering, and the anode is used. A first electrode 1101 capable of performing the function was formed. Its film thickness was 110 nm, and the electrode area was 2 The dimensions were set to mm x 2 mm.

[0262] Next, as a pretreatment for forming light-emitting elements on the substrate 1100, the substrate surface is washed with water. After baking at 200°C for 1 hour, UV ozone treatment was performed for 370 seconds.

[0263] Then, 10 -4 A substrate is introduced into a vacuum deposition apparatus where the internal pressure is reduced to approximately Pa, and then vacuum deposition is performed. After vacuum firing at 170°C for 30 minutes in the heating chamber of the apparatus, the substrate 1100 is subjected to 3 It was allowed to cool for about 0 minutes.

[0264] Next, the first electrode 1101 is shaped so that the surface on which the first electrode 1101 is formed faces downwards. The completed substrate 1100 is fixed to a substrate holder provided inside the vacuum deposition apparatus, 10 -4 P After reducing the pressure to approximately a, BPAFLP and molybdenum oxide (VI) are placed on the first electrode 1101. A hole injection layer 1111 was formed by co-depositing ) and B. The film thickness was set to 40 nm. The ratio of PAFLP to molybdenum oxide is 4:2 by weight (=BPAFLP:molybdenum oxide It was adjusted to become (n).

[0265] Next, BPAFLP is deposited on the hole injection layer 1111 to a thickness of 20 nm, A pore transport layer 1112 was formed.

[0266] Furthermore, 2mDBTPDBq-II, PCBA1BP, and [Ir(mppm)2(ac A co-deposited ac) was used to form a light-emitting layer 1113 on the hole transport layer 1112. Here, 2m Weights of DBTPDBq-II, PCBA1BP, and [Ir(mppm)2(acac)] The ratio is 0.8:0.2:0.05 (=2mDBTPDBq-II:PCBA1BP:[I The value was adjusted to be r(mppm)2(acac). Also, the film thickness of the light-emitting layer 1113 The nm was set to 40nm.

[0267] Next, 2mDBTPDBq-II is deposited on the light-emitting layer 1113 to a thickness of 10 nm. A first electron transport layer 1114a was formed.

[0268] Next, BPhen is deposited on the first electron transport layer 1114a to a thickness of 20 nm. This formed a second electron transport layer 1114b.

[0269] Furthermore, LiF is deposited on the second electron transport layer 1114b to a thickness of 1 nm, forming an electron injection layer. Formed 1115.

[0270] Finally, a 200 nm film of aluminum is used as the second electrode 1103, which functions as the cathode. The light-emitting element 7 of this embodiment was fabricated by depositing a material to a certain thickness.

[0271] (light-emitting element 8) The light-emitting layer 1113 of the light-emitting element 8 is composed of 2mDBTPDBq-II, αNBA1BP and [Ir It was formed by co-depositing (mppm)2(acac). Here, 2mDBTPDB The weight ratio of q-II, αNBA1BP, and [Ir(mppm)2(acac)] is 0.8 :0.2:0.05(=2mDBTPDBq-II:αNBA1BP:[Ir(mppm The settings were adjusted to be )2(acac)]). Also, the film thickness of the light-emitting layer 1113 was 40 nm. Except for the light-emitting layer 1113, the components were fabricated in the same manner as the light-emitting element 7.

[0272] In the vapor deposition process described above, resistance heating was used for all deposition steps.

[0273] Table 9 shows the element structures of the light-emitting element 7 and light-emitting element 8 obtained as described above.

[0274] [Table 9]

[0275] These light-emitting elements are placed in a glove box under a nitrogen atmosphere, and the light-emitting elements are exposed to the air. After sealing the device to prevent leakage, the operating characteristics of the light-emitting element were measured. The measurements were taken at room temperature (in an atmosphere maintained at 25°C).

[0276] Figure 31 shows the current density-luminance characteristics of light-emitting elements 7 and 8. In Figure 31, the horizontal axis The current density is (mA / cm²). 2 The vertical axis represents luminance (cd / m²). 2 ) represents. Also, voltage-luminance characteristics The properties are shown in Figure 32. In Figure 32, the horizontal axis represents voltage (V), and the vertical axis represents luminance (cd / m²). 2 )of The luminance-current efficiency characteristics are shown in Figure 33. In Figure 33, the horizontal axis represents luminance (cd / m 2 The vertical axis represents current efficiency (cd / A). Figure 34 shows the luminance-external quantum efficiency characteristics. As shown in Figure 34, the horizontal axis represents luminance (cd / m²). 2 The vertical axis represents the external quantum efficiency (%). show.

[0277] Furthermore, the brightness of the light-emitting elements 7 and 8 is 1000 cd / m². 2 Voltage (V) in the vicinity ), current density (mA / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), Table 10 shows the wah efficiency (lm / W) and external quantum efficiency (%).

[0278] [Table 10]

[0279] Furthermore, the emission spectra when a current of 0.1 mA is passed through light-emitting elements 7 and 8 are shown in Figure 7. This is shown in Figure 35. In Figure 35, the horizontal axis represents wavelength (nm), and the vertical axis represents emission intensity (in arbitrary units). Also, as shown in Table 10, 1100 cd / m² 2 The CIE chromaticity of the light-emitting element 7 at the brightness of The standard is (x,y)=(0.43,0.56), and the temperature is 860 cd / m². 2 The light-emitting element at this brightness The CIE chromaticity coordinates of child 8 were (x,y)=(0.43,0.56). From this result, Light-emitting elements 7 and 8 emit yellowish-green light derived from [Ir(mppm)2(acac)]. It was confirmed that light was obtained.

[0280] As can be seen from Table 10 and Figures 31 to 34, the light-emitting element 7 and the light-emitting element 8 have current efficiency The power efficiency and external quantum efficiency both showed high values.

[0281] Light-emitting elements 7 and 8 are PCBA1BP or αNBA1BP as shown in Example 8, 2mDBTPDBq-II and [Ir(mppm)2(acac)] are used as the light-emitting layer. From Example 8, 2mDBTPDBq-II and PCBA1BP or αNBA1BP The emission spectrum of the mixed material is the absorption spectrum of [Ir(mppm)2(acac)]. In this case, there is a large overlap with the absorption band which is thought to contribute strongly to light emission. The light-emitting element 7 and The optical element 8 utilizes this overlap to transfer energy, thus having high energy transfer efficiency. Therefore, the external quantum efficiency is considered to be high.

[0282] From the above results, it is possible to realize a device with high external quantum efficiency by applying one aspect of the present invention. This was shown to be the case.

[0283] Next, reliability tests were performed on light-emitting elements 7 and 8. The results of the reliability tests are shown in Figure 36. In Figure 36, the vertical axis represents the normalized luminance (%) when the initial luminance is set to 100%, and the horizontal axis represents the normalized luminance (%). The axis indicates the operating time (h) of the element.

[0284] Reliability testing was performed with an initial brightness of 5000 cd / m². 2 Set to the following condition and the current density is constant for the light-emitting element. The 7 and the light-emitting element 8 were driven.

[0285] The brightness of light-emitting element 7 after 260 hours was 74% of its initial brightness. Also, light-emitting element 8 The brightness after 260 hours was 75% of the initial brightness. From this result, the light-emitting element 7 and It was found that optical element 8 is an element with a long lifespan.

[0286] From the above results, it is possible to realize a highly reliable element by applying one aspect of the present invention. This was shown. [Examples]

[0287] In this embodiment, a guest material and phosphorus can be applied to a light-emitting element according to one aspect of the present invention. An example of a material will be explained using Figure 37.

[0288] The guest material used in this example is (acetylacetonate)bis(6-tert-butyl- 4-Phenylpyrimidinato) Iridium(III) (Abbreviation: [Ir(tBuppm)2( acac)])). Also, the host material used in this embodiment is 2mDBTPDBq-I A mixed material of I and NPB, and 2mDBTPDBq-II and 2,7-bis[N-(4-di Phenylaminophenyl)-N-phenylamino]-spiro-9,9'-bifluorene( There are two types of mixed materials (abbreviated as DPA2SF). The chemical formulas of the materials used in this example are as follows: This is shown below. Note that the chemical formulas of the materials used in the previous example are omitted.

[0289] [ka]

[0290] <Absorption Spectrum> Figure 37(A)(B) shows the dichloromethane solution of [Ir(tBuppm)2(acac)] The ultraviolet-visible absorption spectrum (absorption spectrum d) is shown. To measure the absorption spectrum, ultraviolet light is required. Using a visible spectrophotometer (JASCO Corporation, Model V550), dichloromethane solution (0.0 A 93 mmol / L solution was placed in a quartz cell and measured at room temperature.

[0291] <Emission spectrum> Also, Figures 37(A) and (B) show a thin layer of the mixed material of 2mDBTPDBq-II and DPA2SF. Emission spectrum of the film (emission spectrum d-1), and 2mDBTPDBq-II and NPB Figure 37(A) shows the emission spectrum (emission spectrum d-2) of a thin film of the mixed material. On the horizontal axis, the wavelength (nm) is shown, and on the vertical axis, the molar extinction coefficient ε(M) is shown. -1 ·cm -1 ) and The luminescence intensity (in arbitrary units) is shown. In Figure 37(B), the horizontal axis represents energy (eV). The vertical axis represents the molar extinction coefficient ε(M -1 ·cm -1 ) and luminescence intensity (in arbitrary units) are shown.

[0292] From the absorption spectrum d in Figure 37(A), [Ir(tBuppm)2(acac)] is 4 It can be seen that it has a broad absorption band around 90 nm. This absorption band strongly contributes to luminescence. It is thought to be an absorption zone.

[0293] The peaks in emission spectra d-1 and d-2 correspond to the absorption spectrum d. It was found that there is a large overlap with the absorption band that is thought to contribute strongly to luminescence. A light-emitting device that uses both the guest material and either of the host materials in the light-emitting layer, as used in the example, is By utilizing the overlap between the emission spectrum of the main material and the absorption spectrum of the guest material, energy Because ghee transfer occurs, it was suggested that the energy transfer efficiency is high. Therefore, external quantity This suggests that a light-emitting element with high efficiency can be obtained.

[0294] Here, emission spectrum d-2 has a shorter wavelength (higher energy) than emission spectrum d-1. It has a peak on the side. And the peak of emission spectrum d-2 is on emission spectrum d-1 It is located closer to the absorption band compared to the peak. Therefore, in Figure 37, The emission spectrum that has the greatest overlap with the absorption band that strongly contributes to the emission in the absorption spectrum d is: It was found to be emission spectrum d-2. Specifically, in absorption spectrum d, The difference between the absorption band peak and the emission spectrum d-1 peak is 0.39 eV, and the absorption spectrum The difference between the peak of the absorption band at Torr d and the peak of the emission spectrum d-2 is 0.19 eV. there were.

[0295] The difference between the peaks of emission spectra d-1 and d-2 is due to DPA2SF and NPB. This is thought to be due to a difference in HOMO levels. Specifically, the HOMO level of DPA2SF is While the NPB's HOMO level was -5.09 eV, the NPB's HOMO level was -5.38 eV (izu (These values ​​were also calculated by CV measurement.) Compared to DPA2SF, NPB has a lower HOMO level. (Deep) Therefore, the peak of emission spectrum d-2 is at a shorter wavelength than emission spectrum d-1. It is thought that the energy level increased.

[0296] From the above, a mixed material of 2mDBTPDBq-II and NPB, and [Ir(tBup A light-emitting element that uses both pm)2(acac) in the light-emitting layer is 2mDBTPDBq-II A mixed material of DPA2SF and [Ir(tBuppm)2(acac)] emits light together. Compared to the light-emitting element used in the layer, the emission spectrum of the host material and the absorption spectrum of the guest material Because it utilizes a larger overlap with the element to transfer energy, the energy transfer efficiency is high. This suggests that the external quantum efficiency is higher. Therefore, it is possible to obtain a light-emitting element with a higher external quantum efficiency. This was suggested. [Examples]

[0297] In this embodiment, a light-emitting element according to one aspect of the present invention will be described with reference to Figure 2. Since the materials used are the same as those used in the previous example, the chemical formulas are omitted.

[0298] The following describes the method for manufacturing the light-emitting element 9 and light-emitting element 10 in this embodiment.

[0299] (light-emitting element 9) First, ITSO is deposited on the glass substrate 1100 by sputtering, and the anode is used. A first electrode 1101 capable of performing the function was formed. Its film thickness was 110 nm, and the electrode area was 2 The dimensions were set to mm x 2 mm.

[0300] Next, as a pretreatment for forming light-emitting elements on the substrate 1100, the substrate surface is washed with water. After baking at 200°C for 1 hour, UV ozone treatment was performed for 370 seconds.

[0301] Then, 10 -4 A substrate is introduced into a vacuum deposition apparatus where the internal pressure is reduced to approximately Pa, and then vacuum deposition is performed. After vacuum firing at 170°C for 30 minutes in the heating chamber of the apparatus, the substrate 1100 is subjected to 3 It was allowed to cool for about 0 minutes.

[0302] Next, the first electrode 1101 is shaped so that the surface on which the first electrode 1101 is formed faces downwards. The completed substrate 1100 is fixed to a substrate holder provided inside the vacuum deposition apparatus, 10 -4 P After reducing the pressure to approximately a, DBT3P-II and molybdenum oxide are placed on the first electrode 1101. A hole injection layer 1111 was formed by co-depositing VI). The film thickness was set to 40 nm. The ratio of DBT3P-II to molybdenum oxide is 4:2 by weight (=DBT3P-II: The formula was adjusted to be molybdenum oxide.

[0303] Next, BPAFLP is deposited on the hole injection layer 1111 to a thickness of 20 nm, A pore transport layer 1112 was formed.

[0304] Furthermore, 2mDBTPDBq-II, DPA2SF, and [Ir(tBuppm)2(a CAC) was co-deposited to form a light-emitting layer 1113 on the hole transport layer 1112. Here, 2 mDBTPDBq-II, DPA2SF and [Ir(tBuppm)2(acac)] The weight ratio is 0.8:0.2:0.05 (=2mDBTPDBq-II:DPA2SF:[ The settings were adjusted so that Ir(tBuppm)2(acac)). Also, the light-emitting layer 1113 The film thickness was set to 40 nm.

[0305] Next, 2mDBTPDBq-II is deposited on the light-emitting layer 1113 to a thickness of 10 nm. A first electron transport layer 1114a was formed.

[0306] Next, BPhen is deposited on the first electron transport layer 1114a to a thickness of 20 nm. This formed a second electron transport layer 1114b.

[0307] Furthermore, LiF is deposited on the second electron transport layer 1114b to a thickness of 1 nm, forming an electron injection layer. Formed 1115.

[0308] Finally, a 200 nm film of aluminum is used as the second electrode 1103, which functions as the cathode. The light-emitting element 9 of this embodiment was fabricated by depositing a material to a certain thickness.

[0309] (light-emitting element 10) The light-emitting layer 1113 of the light-emitting element 10 is composed of 2mDBTPDBq-II, NPB and [Ir(tB It was formed by co-depositing uppm)2(acac). Here, 2mDBTPDBq -II, NPB, and [Ir(tBuppm)2(acac)] have a weight ratio of 0.8:0. 2:0.05(=2mDBTPDBq-II:NPB:[Ir(tBuppm)2(ac The settings were adjusted to result in (ac)). The film thickness of the light-emitting layer 1113 was set to 40 nm. Except for layer 1113, the layers were fabricated in the same manner as the light-emitting element 9.

[0310] In the vapor deposition process described above, resistance heating was used for all deposition steps.

[0311] Table 11 shows the element structures of the light-emitting element 9 and light-emitting element 10 obtained as described above.

[0312] [Table 11]

[0313] These light-emitting elements are placed in a glove box under a nitrogen atmosphere, and the light-emitting elements are exposed to the air. After sealing the device to prevent leakage, the operating characteristics of the light-emitting element were measured. The measurements were taken at room temperature (in an atmosphere maintained at 25°C).

[0314] Figure 38 shows the current density-luminance characteristics of light-emitting elements 9 and 10. In Figure 38, horizontal The axis represents current density (mA / cm²). 2 The vertical axis represents luminance (cd / m²). 2 ) represents. Also, voltage-luminance. The characteristics are shown in Figure 39. In Figure 39, the horizontal axis represents voltage (V), and the vertical axis represents luminance (cd / m²). 2 ) This represents the luminance-current efficiency characteristics, which are shown in Figure 40. In Figure 40, the horizontal axis represents luminance (cd). / m 2 The vertical axis represents current efficiency (cd / A). Figure 4 shows the luminance-external quantum efficiency characteristics. As shown in 1. In Figure 41, the horizontal axis represents luminance (cd / m²). 2 The vertical axis represents the external quantum efficiency (%). This indicates.

[0315] Furthermore, the brightness of the light-emitting elements 9 and 10 is 1000 cd / m². 2 Voltage in the vicinity ( V), current density (mA / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), Table 12 shows the power efficiency (lm / W) and external quantum efficiency (%).

[0316] [Table 12]

[0317] Furthermore, the emission spectra when a current of 0.1 mA is passed through light-emitting elements 9 and 10 are as follows: This is shown in Figure 42. In Figure 42, the horizontal axis represents wavelength (nm), and the vertical axis represents emission intensity (arbitrary units). Furthermore, as shown in Table 12, 890 cd / m² 2 The CIE chromaticity of the light-emitting element 9 at this brightness level The standard is (x,y)=(0.43,0.56), and the temperature is 820 cd / m². 2 The light-emitting element at this brightness The CIE chromaticity coordinates of child 10 were (x,y)=(0.42,0.57). From this result, The light-emitting elements 9 and 10 are derived from [Ir(tBuppm)2(acac)]. It was found that yellow-green light emission was obtained.

[0318] As can be seen from Table 12 and Figures 38 to 41, the light-emitting element 9 and the light-emitting element 10 are current-powered The rate, power efficiency, and external quantum efficiency all showed high values.

[0319] Light-emitting elements 9 and 10 are DPA2SF or NPB as shown in Example 10, and 2mD BTPDBq-II and [Ir(tBuppm)2(acac)] were used as the light-emitting layer. From Example 10, a mixed material of 2mDBTPDBq-II and DPA2SF or NPB The emission spectrum is obtained from the absorption spectrum of [Ir(tBuppm)2(acac)]. There is a large overlap with the absorption band that is thought to contribute strongly to light emission. (Emitting element 9 and Emitting element) 10 utilizes this overlap to transfer energy, so the energy transfer efficiency is high, and The quantum efficiency is considered to be high, especially for mixed materials of 2mDBTPDBq-II and NPB. The emission spectrum is the emission spectrum of a mixed material of 2mDBTPDBq-II and DPA2SF. Compared to the light-emitting element, the overlap with the absorption band is large. Therefore, the light-emitting element 10 has a large overlap. Because it uses energy transfer, it has a higher energy transfer efficiency compared to the light-emitting element 9. Therefore, the external quantum efficiency is considered to be high. Also, by referring to the results of Example 10 together... In the light-emitting layer, the energy value of the peak in the emission spectrum of the host material and the guest material The difference between the energy value of the peak in the lowest energy absorption band of the absorption spectrum and the current energy value is 0. It is clear that a voltage of 3 eV or less is preferable.

[0320] From the above results, it is possible to realize a device with high external quantum efficiency by applying one aspect of the present invention. This was shown to be the case. [Examples]

[0321] In this embodiment, a guest material and phosphorus can be applied to a light-emitting element according to one aspect of the present invention. An example of a material will be explained using Figure 43.

[0322] The guest material used in this embodiment is [Ir(mppr-Me)2(dpm)]. The host material used in this embodiment is 2mDBTPDBq-II and 4,4',4''-tri S[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1'-T) A mixture of NATA and 2-[4-(dibenzothiophen-4-yl)phenyl] -1-phenyl-1H-benzimidazole (abbreviation: DBTBIm-II) and 1'-TN There are two types of mixed materials with ATA. The chemical formulas of the materials used in this example are shown below. The chemical formulas of the materials used in the previous example are omitted.

[0323] [ka]

[0324] <Absorption Spectrum> Figure 43(A)(B) shows the dichloromethane solution of [Ir(mppr-Me)2(dpm)] The ultraviolet-visible absorption spectrum (absorption spectrum e) is shown. To measure the absorption spectrum, ultraviolet light is required. Using a visible spectrophotometer (JASCO Corporation, Model V550), dichloromethane solution (0.0 A 93 mmol / L solution was placed in a quartz cell and measured at room temperature.

[0325] <Emission spectrum> Also, Figures 43(A)(B) show a mixed material of 2mDBTPDBq-II and 1'-TNATA. Emission spectrum of the thin film (emission spectrum e-1), and DBTBIm-II and 1'-T Figure 43 shows the emission spectrum (e-2 emission spectrum) of a thin film of NATA mixed material. In A), the horizontal axis represents wavelength (nm), and the vertical axis represents the molar extinction coefficient ε(M). -1 ·cm - 1 The horizontal axis shows the energy (e) and luminescence intensity (in arbitrary units). In Figure 43(B), the horizontal axis is the energy (e) The graph shows V), and the vertical axis represents the molar extinction coefficient ε(M -1 ·cm -1 ) and luminescence intensity (in arbitrary units) show.

[0326] From the absorption spectrum e in Figure 43(A), [Ir(mppr-Me)2(dpm)] is 5 It can be seen that it has a broad absorption band around 20 nm. This absorption band strongly contributes to luminescence. It is thought to be an absorption zone.

[0327] The peaks in emission spectra e-1 and e-2 correspond to the absorption spectrum e. It was found that there is a large overlap with the absorption band that is thought to contribute strongly to luminescence. A light-emitting device that uses both the guest material and either of the host materials in the light-emitting layer, as used in the example, is By utilizing the overlap between the emission spectrum of the main material and the absorption spectrum of the guest material, energy Because ghee transfer occurs, it was suggested that the energy transfer efficiency is high. Therefore, external quantity This suggests that a light-emitting element with high efficiency can be obtained.

[0328] Here, emission spectrum e-2 has a shorter wavelength (higher energy) than emission spectrum e-1. It has a peak on the side. And the peak of the emission spectrum e-2 is the same as the peak of the emission spectrum e-1 It is located closer to the absorption band compared to the peak. Therefore, in Figure 43, The emission spectrum that has the greatest overlap with the absorption band that strongly contributes to the emission in the absorption spectrum e is: It was found to be the emission spectrum e-2. Specifically, the absorption spectrum e The peak of the absorption band (shoulder peak around 520 nm) and the peak of the emission spectrum e-1. The difference is 0.35 eV, and the peak of the absorption band in the absorption spectrum e (at 520 nm) The difference between the near shoulder peak and the peak of the emission spectrum e-2 was 0.01 eV.

[0329] The difference between the peaks of emission spectrum e-1 and emission spectrum e-2 is 2mDBTPDBq-I This is thought to be due to the difference in LUMO levels between I and DBTBIm-II. Specifically, 2m The LUMO level of DBTPDBq-II is -2.95eV, whereas DBTBIm- The LUMO level of II was -2.52 eV (all values ​​were calculated by CV measurement). Compared to 2mDBTPDBq-II, DBTBIm-II has a higher (shallower) LUMO level. Therefore, even when mixed with 1'-TNATA, which has a high HOMO level, the emission spectrum of the mixed material is The peak did not become too long in wavelength (i.e., the emission spectrum e-2 was, (It is thought to have a peak on the shorter wavelength side compared to e-1.)

[0330] From the above, a mixed material of DBTBIm-II and 1'-TNATA, and [Ir(mp The light-emitting element using pr-Me)2(dpm)] is 2mDBTPDBq-II and 1'-T A light-emitting element using a NATA mixed material and [Ir(mppr-Me)2(dpm)] In comparison, the larger weight of the emission spectrum of the mixed material and the absorption spectrum of the phosphorescent compound Because it utilizes this structure for energy transfer, it is suggested that the energy transfer efficiency is higher. Therefore, it was suggested that a light-emitting device with a higher external quantum efficiency can be obtained. [Examples]

[0331] In this embodiment, a light-emitting element according to one aspect of the present invention will be described with reference to Figure 2. Since the materials used are the same as those used in the previous example, the chemical formulas are omitted.

[0332] The following describes the method for manufacturing the light-emitting element 11 and light-emitting element 12 in this embodiment.

[0333] (light-emitting element 11) First, ITSO is deposited on the glass substrate 1100 by sputtering, and the anode is used. A first electrode 1101 capable of performing the function was formed. Its film thickness was 110 nm, and the electrode area was 2 The dimensions were set to mm x 2 mm.

[0334] Next, as a pretreatment for forming light-emitting elements on the substrate 1100, the substrate surface is washed with water. After baking at 200°C for 1 hour, UV ozone treatment was performed for 370 seconds.

[0335] Then, 10 -4 A substrate is introduced into a vacuum deposition apparatus where the internal pressure is reduced to approximately Pa, and then vacuum deposition is performed. After vacuum firing at 170°C for 30 minutes in the heating chamber of the apparatus, the substrate 1100 is subjected to 3 It was allowed to cool for about 0 minutes.

[0336] Next, the first electrode 1101 is shaped so that the surface on which the first electrode 1101 is formed faces downwards. The completed substrate 1100 is fixed to a substrate holder provided inside the vacuum deposition apparatus, 10 -4 P After reducing the pressure to approximately a, BPAFLP and molybdenum oxide (VI) are placed on the first electrode 1101. A hole injection layer 1111 was formed by co-depositing ) and B. The film thickness was set to 40 nm. The ratio of PAFLP to molybdenum oxide is 4:2 by weight (=BPAFLP:molybdenum oxide It was adjusted to become (n).

[0337] Next, BPAFLP is deposited on the hole injection layer 1111 to a thickness of 20 nm, A pore transport layer 1112 was formed.

[0338] Furthermore, 2mDBTPDBq-II, 1'-TNATA, and [Ir(mppr-Me) 2(dpm) was co-deposited, and a light-emitting layer 1113 was formed on the hole transport layer 1112. ,2mDBTPDBq-II,1'-TNATA and [Ir(mppr-Me)2(dp The weight ratio of m) is 0.8:0.2:0.05 (=2mDBTPDBq-II:1'-T The NATA was adjusted to be [Ir(mppr-Me)2(dpm)]). The film thickness of the optical layer 1113 was set to 20 nm.

[0339] Next, 2mDBTPDBq-II is deposited on the light-emitting layer 1113 to a thickness of 30 nm. A first electron transport layer 1114a was formed.

[0340] Next, BPhen is deposited on the first electron transport layer 1114a to a thickness of 20 nm. This formed a second electron transport layer 1114b.

[0341] Furthermore, LiF is deposited on the second electron transport layer 1114b to a thickness of 1 nm, forming an electron injection layer. Formed 1115.

[0342] Finally, a 200 nm film of aluminum is used as the second electrode 1103, which functions as the cathode. The light-emitting element 11 of this embodiment was fabricated by depositing a material to a certain thickness.

[0343] (light-emitting element 12) The light-emitting layer 1113 of the light-emitting element 12 is composed of DBTBIm-II, 1'-TNATA and [Ir( It was formed by co-depositing mppr-Me)2(dpm). Here, DBTBIm- The weight ratio of II, 1'-TNATA, and [Ir(mppr-Me)2(dpm)] is 0. 8:0.2:0.05(=DBTBIm-II:1'-TNATA:[Ir(mppr- The settings were adjusted to Me)2(dpm). The film thickness of the light-emitting layer 1113 was 20 nm. That's what I decided.

[0344] The first electron transport layer 1114a of the light-emitting element 12 is made of DBTBIm-II with a film thickness of 30 nm. It was formed by depositing a film in the manner described above, except for the light-emitting layer 1113 and the first electron transport layer 1114a. It was fabricated in the same manner as the light-emitting element 11.

[0345] In the vapor deposition process described above, resistance heating was used for all deposition steps.

[0346] Table 13 shows the element structures of the light-emitting element 11 and light-emitting element 12 obtained as described above.

[0347] [Table 13]

[0348] These light-emitting elements are placed in a glove box under a nitrogen atmosphere, and the light-emitting elements are exposed to the air. After sealing the device to prevent leakage, the operating characteristics of the light-emitting element were measured. The measurements were taken at room temperature (in an atmosphere maintained at 25°C).

[0349] The current density-luminance characteristics of light-emitting elements 11 and 12 are shown in Figure 44. In Figure 44, The horizontal axis represents current density (mA / cm²). 2 The vertical axis represents luminance (cd / m²). 2 ) represents voltage-brightness. The characteristics are shown in Figure 45. In Figure 45, the horizontal axis represents voltage (V), and the vertical axis represents luminance (cd / m²). 2 Figure 46 shows the luminance-current efficiency characteristics. In Figure 46, the horizontal axis represents luminance (c d / m 2 The vertical axis represents current efficiency (cd / A), and the luminance-external quantum efficiency characteristics are also shown in the figure. This is shown in Figure 47. In Figure 47, the horizontal axis represents luminance (cd / m²). 2 The vertical axis represents the external quantum efficiency (%). ) indicates.

[0350] Furthermore, the brightness of the light-emitting element 11 and light-emitting element 12 is 860 cd / m². 2 Voltage (V) at that time , current density (mA / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), power Table 14 shows the efficiency (lm / W) and external quantum efficiency (%).

[0351] [Table 14]

[0352] Furthermore, the emission spectra when a current of 0.1 mA is passed through the light-emitting elements 11 and 12 are as follows: This is shown in Figure 48. In Figure 48, the horizontal axis is wavelength (nm), and the vertical axis is emission intensity (arbitrary unit). It is represented as follows. Also, as shown in Table 14, 860 cd / m² 2 The light-emitting element 11 and light-emitting element at the brightness of The CIE chromaticity coordinates of child 12 were (x,y)=(0.53,0.46). From this result, The light-emitting elements 11 and 12 are derived from [Ir(mppr-Me)2(dpm)]. It was found that an orange emission was obtained.

[0353] As can be seen from Table 14 and Figures 44 to 47, the light-emitting element 11 and the light-emitting element 12 are current High values ​​were observed for efficiency, power efficiency, and external quantum efficiency.

[0354] The light-emitting element 11 and the light-emitting element 12 are 2mDBTPDBq-II or D as shown in Example 12. BTBIm-II, 1'-TNATA, and [Ir(mppr-Me)2(dpm)] , was used as the light-emitting layer. From Example 12, 2mDBTPDBq-II or DBTBIm-I The emission spectrum of a mixed material of I and 1'-TNATA is [Ir(mppr-Me)2 Overlap with the absorption band in the absorption spectrum of (dpm) that is thought to strongly contribute to emission. The overlap is large. The light-emitting element 11 and the light-emitting element 12 utilize this overlap to transfer energy. Therefore, it is thought that the energy transfer efficiency is high and the external quantum efficiency is high. In particular, DBTB The emission spectrum of the Im-II and 1'-TNATA mixed material is 2mDBTPDBq-I Compared to the emission spectrum of a mixed material of I and 1'-TNATA, the overlap with the absorption band is large. Therefore, the light-emitting element 12 utilizes this large overlap to transfer energy. Compared to the light-emitting element 11, it is thought to have higher energy transfer efficiency and higher external quantum efficiency. Furthermore, by referring to the results of Example 12, the light emission of the host material in the light-emitting layer was observed. The energy value of the peak in the spectrum and the lowest energy in the absorption spectrum of the guest material. It has been found that the difference between the energy value of the peak of the absorption band on the side and the other side is preferably within 0.3 eV. Light.

[0355] From the above results, it is possible to realize a device with high external quantum efficiency by applying one aspect of the present invention. This was shown to be the case. [Examples]

[0356] In this embodiment, a guest material and phosphorus can be applied to a light-emitting element according to one aspect of the present invention. An example of a material will be explained using Figure 49.

[0357] The guest material used in this embodiment is [Ir(mppr-Me)2(dpm)]. The host material used in this embodiment is a mixture of 2mDBTPDBq-II and PCBNBB. The material, and 2mDBTPDBq-II and 9-phenyl-9H-3-(9-phenyl-9H- There are two types of mixed materials: one with carbazole-3-yl)carbazole (abbreviation: PCCP). The chemical formulas of the materials used in this example are shown below. (This part is omitted.)

[0358] [ka]

[0359] <Absorption Spectrum> Figure 49(A)(B) shows the dichloromethane solution of [Ir(mppr-Me)2(dpm)] The ultraviolet-visible absorption spectrum (absorption spectrum f) is shown. To measure the absorption spectrum, ultraviolet light is required. Using a visible spectrophotometer (JASCO Corporation, Model V550), dichloromethane solution (0.0 A 93 mmol / L solution was placed in a quartz cell and measured at room temperature.

[0360] <Emission spectrum> Furthermore, Figures 49(A) and (B) show a thin layer of the mixed material of 2mDBTPDBq-II and PCBNBB. Emission spectrum of the film (emission spectrum f-1), and 2mDBTPDBq-II and PCC Figure 49(A) shows the emission spectrum (emission spectrum f-2) of a thin film of a P mixed material. In this graph, the horizontal axis represents wavelength (nm), and the vertical axis represents the molar extinction coefficient ε(M). -1 ·cm -1 ) and The horizontal axis shows the luminescence intensity (in arbitrary units). In Figure 49(B), the horizontal axis represents energy (eV). The vertical axis represents the molar extinction coefficient ε(M -1 ·cm -1 ) and luminescence intensity (in arbitrary units) are shown.

[0361] From the absorption spectrum f in Figure 49(A), [Ir(mppr-Me)2(dpm)] is 5 It can be seen that it has a broad absorption band around 00 nm. This absorption band strongly contributes to luminescence. It is thought to be an absorption zone.

[0362] The peaks in emission spectra f-1 and f-2 correspond to the absorption spectrum f. It was found that there is a large overlap with the absorption band that is thought to contribute strongly to luminescence. A light-emitting device that uses both the guest material and either of the host materials in the light-emitting layer, as used in the example, is By utilizing the overlap between the emission spectrum of the main material and the absorption spectrum of the guest material, energy Because ghee transfer occurs, it was suggested that the energy transfer efficiency is high. Therefore, external quantity This suggests that a light-emitting element with high efficiency can be obtained.

[0363] Furthermore, in this embodiment, the host material is not limited to a mixed material containing aromatic amine compounds. It was also suggested that mixed materials containing carbazole compounds could be used instead. [Examples]

[0364] In this embodiment, a light-emitting element according to one aspect of the present invention will be described with reference to Figure 2. Since the materials used are the same as those used in the previous example, the chemical formulas are omitted.

[0365] The following describes the method for manufacturing the light-emitting element 13 and light-emitting element 14 in this embodiment.

[0366] (light-emitting element 13) First, ITSO is deposited on the glass substrate 1100 by sputtering, and the anode is used. A first electrode 1101 capable of performing the function was formed. Its film thickness was 110 nm, and the electrode area was 2 The dimensions were set to mm x 2 mm.

[0367] Next, as a pretreatment for forming light-emitting elements on the substrate 1100, the substrate surface is washed with water. After baking at 200°C for 1 hour, UV ozone treatment was performed for 370 seconds.

[0368] Then, 10 -4 A substrate is introduced into a vacuum deposition apparatus where the internal pressure is reduced to approximately Pa, and then vacuum deposition is performed. After vacuum firing at 170°C for 30 minutes in the heating chamber of the apparatus, the substrate 1100 is subjected to 3 It was allowed to cool for about 0 minutes.

[0369] Next, the first electrode 1101 is shaped so that the surface on which the first electrode 1101 is formed faces downwards. The completed substrate 1100 is fixed to a substrate holder provided inside the vacuum deposition apparatus, 10 -4 P After reducing the pressure to approximately a, BPAFLP and molybdenum oxide (VI) are placed on the first electrode 1101. A hole injection layer 1111 was formed by co-depositing ) and B. The film thickness was set to 40 nm. The ratio of PAFLP to molybdenum oxide is 4:2 by weight (=BPAFLP:molybdenum oxide It was adjusted to become (n).

[0370] Next, BPAFLP is deposited on the hole injection layer 1111 to a thickness of 20 nm, A pore transport layer 1112 was formed.

[0371] Furthermore, 2mDBTPDBq-II, PCBNBB, and [Ir(mppr-Me)2( A dpm) was co-deposited to form a light-emitting layer 1113 on the hole transport layer 1112. Here, 2 mDBTPDBq-II, PCBNBB and [Ir(mppr-Me)2(dpm)] The weight ratio is 0.8:0.2:0.05 (=2mDBTPDBq-II:PCBNBB:[ The settings were adjusted to Ir(mppr-Me)2(dpm)). Also, the light-emitting layer 1113 The film thickness was set to 20 nm.

[0372] Next, 2mDBTPDBq-II, PCBNBB, and [Ir(mp pr-Me)2(dpm)] is co-deposited, and a first electron transport layer 1114 is placed on the light-emitting layer 1113. a was formed. Here, 2mDBTPDBq-II, PCBNBB and [Ir(mppr The weight ratio of -Me)2(dpm) is 0.8:0.2:0.05 (=2mDBTPDBq -II:PCBNBB:[Ir(mppr-Me)2(dpm)]) Furthermore, the film thickness of the first electron transport layer 1114a was set to 40 nm.

[0373] Next, BPhen is deposited on the first electron transport layer 1114a to a thickness of 10 nm. This formed a second electron transport layer 1114b.

[0374] Furthermore, LiF is deposited on the second electron transport layer 1114b to a thickness of 1 nm, forming an electron injection layer. Formed 1115.

[0375] Finally, a 200 nm film of aluminum is used as the second electrode 1103, which functions as the cathode. The light-emitting element 13 of this embodiment was fabricated by depositing a material to a certain thickness.

[0376] (light-emitting element 14) The light-emitting layer 1113 of the light-emitting element 14 is 2mDBTPDBq-II, 9-phenyl-9H-3 -(9-phenyl-9H-carbazole-3-yl)carbazole (abbreviation: PCCP) and It was formed by co-depositing [Ir(mppr-Me)2(dpm)]. Here, 2m Weight ratio of DBTPDBq-II, PCCP, and [Ir(mppr-Me)2(dpm)] is 0.8:0.2:0.05(=2mDBTPDBq-II:PCCP:[Ir(mp The film thickness of the light-emitting layer 1113 was adjusted to pr-Me)2(dpm). The wavelength was set to 0 nm. Except for the light-emitting layer 1113, the light-emitting element 13 was fabricated in the same manner as the other elements.

[0377] In the vapor deposition process described above, resistance heating was used for all deposition steps.

[0378] Table 15 shows the element structures of the light-emitting element 13 and light-emitting element 14 obtained as described above.

[0379] [Table 15]

[0380] These light-emitting elements are placed in a glove box under a nitrogen atmosphere, and the light-emitting elements are exposed to the air. After sealing the device to prevent leakage, the operating characteristics of the light-emitting element were measured. The measurements were taken at room temperature (in an atmosphere maintained at 25°C).

[0381] Figure 50 shows the current density-luminance characteristics of the light-emitting element 13 and the light-emitting element 14. In Figure 50, The horizontal axis represents current density (mA / cm²). 2 The vertical axis represents luminance (cd / m²). 2 ) represents voltage-brightness. The characteristics are shown in Figure 51. In Figure 51, the horizontal axis represents voltage (V), and the vertical axis represents luminance (cd / m²). 2 Figure 52 shows the luminance-current efficiency characteristics. In Figure 52, the horizontal axis represents luminance (c d / m 2 The vertical axis represents current efficiency (cd / A), and the luminance-external quantum efficiency characteristics are also shown in the figure. This is shown in Figure 53. In Figure 53, the horizontal axis represents luminance (cd / m²). 2 The vertical axis represents the external quantum efficiency (%). ) indicates.

[0382] Furthermore, the brightness of the light-emitting elements 13 and 14 is 1200 cd / m². 2 The voltage at that time (V ), current density (mA / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), Table 16 shows the wah efficiency (lm / W) and external quantum efficiency (%).

[0383] [Table 16]

[0384] Furthermore, the emission spectrum when a current of 0.1 mA is passed through the light-emitting elements 13 and 14 is... This is shown in Figure 54. In Figure 54, the horizontal axis is wavelength (nm), and the vertical axis is emission intensity (arbitrary unit). It is represented as follows. Also, as shown in Table 16, 1200 cd / m² 2 CIE of light-emitting element 13 at this brightness The chromaticity coordinates are (x,y)=(0.54,0.45), and the color density is 1200 cd / m². 2 When the brightness is The CIE chromaticity coordinates of the light-emitting element 14 were (x,y)=(0.54,0.46). From the results, light-emitting elements 13 and 14 are [Ir(mppr-Me)2(dpm)] It was found that orange luminescence originating from [the source] was obtained.

[0385] As can be seen from Table 16 and Figures 50 to 53, the light-emitting element 13 and the light-emitting element 14 are current High values ​​were observed for efficiency, power efficiency, and external quantum efficiency.

[0386] Light-emitting element 13 and light-emitting element 14 are 2mDBTPDBq-II as shown in Example 14, and P Using CBNBB or PCCP and [Ir(mppr-Me)2(dpm)] in the light-emitting layer From Example 14, a mixture of 2mDBTPDBq-II and PCBNBB or PCCP was found. The emission spectrum of the composite material is the absorption spectrum of [Ir(mppr-Me)2(dpm)]. In this case, there is a large overlap with the absorption band which is thought to contribute strongly to light emission. (Emitting element 13 and Since the light-emitting element 14 uses this overlap to transfer energy, the energy transfer efficiency is It is considered to have a high external quantum efficiency.

[0387] Furthermore, in this embodiment, an aromatic amine compound (PCBNB) was used as the host material for the light-emitting layer. Even if a mixed material containing a carbazole compound (PCCP) is used instead of a mixed material containing B), It was found that a light-emitting device with high external quantum efficiency could be obtained.

[0388] From the above results, it is possible to realize a device with high external quantum efficiency by applying one aspect of the present invention. This was shown to be the case.

[0389] (Reference example 1) The organometallic complex used in the above examples, (acetylacetonato)bis(4,6-diphenylpy Iridium(III) (also known as bis[2-(6-phenyl-4-pyrimidin)) [2,4-Pentanedionato-κC](-κN3)phenyl-κC) 2 O,O') Iridium (III)) (abbreviation: [Ir(dppm)2(acac)]) is shown as an example of synthesis. Note that [ The structure of Ir(dppm)2(acac) is shown below.

[0390] [ka]

[0391] <Step 1: Synthesis of 4,6-diphenylpyrimidine (abbreviation: Hdppm)> First, 5.02g of 4,6-dichloropyrimidine, 8.29g of phenylboronic acid, and sodium carbonate. 7.19g of phosphate, bis(triphenylphosphine)palladium(II) dichloride (abbreviated) (Name: Pd(PPh3)2Cl2) 0.29g, water 20mL, acetonitrile 20mL, The mixture was placed in a round-bottom flask fitted with a reflux tubing, and the inside was purged with argon. Microwave was then added to this reaction vessel. The material was heated by irradiating it with a wave (2.45 GHz, 100 W) for 60 minutes. Then, further heating was performed. Luboronic acid 2.08g, sodium carbonate 1.79g, Pd(PPh3)2Cl 20.07 Place 0g of the substance, 5mL of water, and 5mL of acetonitrile into a flask and microwave again (2.45G). The solution was heated by irradiating it with a 100W (Hz) light for 60 minutes. Then water was added to this solution, and the solution was mixed. The organic layer was extracted with lolomethane. The resulting extract was washed with water and then treated with magnesium sulfate. The solution was dried. The dried solution was filtered. After removing the solvent from the solution, the resulting residue was... The product was purified by silica gel column chromatography using dichloromethane as the developing solvent, and then... Limidine derivative Hdppm was obtained (yellowish-white powder, yield 38%). Microwave irradiation was used. This was done using a microwave synthesizer (Discover, manufactured by CEM). Step 1 is described below. The synthesis scheme (a-1) is shown below.

[0392] [ka]

[0393] Step 2; di-μ-chloro-bis[bis(4,6-diphenylpyrimidinato)iridi Synthesis of um(III) (abbreviation: [Ir(dppm)2Cl]2) Next, 15 mL of 2-ethoxyethanol, 5 mL of water, and the Hdppm1 obtained in step 1 above. 0.10g of iridium chloride hydrate (IrCl3·H2O) and 0.69g of iridium chloride hydrate (IrCl3·H2O) were placed in a reflux tubing. The contents were placed in a round-bottom flask, and the flask was purged with argon. Then, microwave (2.4 The mixture was irradiated with 5GHz (100W) for 1 hour to allow the reaction to proceed. After removing the solvent by distillation, the resulting residue was collected. The solution was filtered with ethanol and then washed to obtain the dinuclear complex [Ir(dppm)2Cl]2 (red). Brown powder, yield 88%. The synthesis scheme for Step 2 (a-2) is shown below.

[0394] [ka]

[0395] Step 3; (Acetylacetonato)bis(4,6-diphenylpyrimidinato)iridi Synthesis of um(III) (abbreviation: [Ir(dppm)2(acac)]) > Furthermore, 40 mL of 2-ethoxyethanol and the [Ir(dppm)2 obtained in step 2 above are added. 21.44g of Cl, 0.30g of acetylacetone, and 1.07g of sodium carbonate are refluxed. The sample was placed in a round-bottom flask with a tube attached, and the inside of the round-bottom flask was purged with argon. Then, micro... The mixture was irradiated with a wave (2.45 GHz, 120 W) for 60 minutes to allow the reaction to proceed. The solvent was removed by distillation, and the result was obtained. The residue was dissolved in dichloromethane and filtered to remove insoluble matter. The resulting filtrate was then mixed with water, and then... The solution was washed with saturated saline solution and dried with magnesium sulfate. The dried solution was then filtered. After removing the solvent from this solution, the resulting residue was collected as dichloromethane:ethyl acetate = 50: The procedure was purified by silica gel column chromatography using a volume ratio of 1 as the developing solvent. By recrystallizing in a mixed solvent of dichloromethane and hexane, the target orange powder is obtained. The end was obtained (yield 32%). The synthesis scheme for step 3 (a-3) is shown below.

[0396] [ka]

[0397] Nuclear magnetic resonance spectroscopy of the orange powder obtained in step 3 above ( 1 Analysis results by 1H NMR The results are shown below. From these results, the organometallic complex [Ir(dppm)2(acac)] was obtained. It was discovered that...

[0398] 1 H NMR.δ(CDCl3):1.83(s,6H),5.29(s,1H),6 .48(d,2H),6.80(t,2H),6.90(t,2H),7.55-7.6 3(m,6H),7.77(d,2H),8.17(s,2H),8.24(d,4H) ,9.17(s,2H).

[0399] (Reference example 2) The organometallic complex used in the above examples, (acetylacetonato)bis(6-methyl-4-phenometallic complex) Iridium(III) (also known as bis[2-(6-methyl-4-pyrimidina)) [Dinyl-κN3)phenyl-κC](2,4-pentanedionato-κ 2 O,O') Iriji The following shows an example of the synthesis of um(III) (abbreviation: [Ir(mppm)2(acac)]). The structure of [Ir(mppm)2(acac)] is shown below.

[0400] [ka]

[0401] <Step 1: Synthesis of 4-methyl-6-phenylpyrimidine (abbreviation: Hmppm)> First, 4.90g of 4-chloro-6-methylpyrimidine, 4.80g of phenylboronic acid, charcoal 4.03g sodium phosphate, bis(triphenylphosphine)palladium(II) dichloride Pd(PPh3)2Cl2 (abbreviation) 0.16g, water 20mL, acetonitrile 10mL L was placed in a round-bottom flask fitted with a reflux tubing, and the inside was purged with argon. The material was heated by irradiating it with microwaves (2.45GHz, 100W) for 60 minutes. Phenylboronic acid 2.28g, sodium carbonate 2.02g, Pd(PPh3)2Cl2 Place 0.082g, 5mL of water, and 10mL of acetonitrile into a flask and microwave again ( The solution was heated by irradiating it with 2.45GHz (100W) for 60 minutes. Then, water was added to this solution. In addition, it was extracted with dichloromethane. The obtained extract was mixed with saturated sodium carbonate aqueous solution, water, Next, the solution was washed with saturated saline solution and dried with magnesium sulfate. The dried solution was then filtered. After removing the solvent from this solution by distillation, the resulting residue was divided into dichloromethane:ethyl acetate = 9 Purification is performed by silica gel column chromatography using a volume ratio of :1 as the developing solvent, and the desired result is obtained. The pyrimidine derivative Hmppm was obtained (orange oily substance, yield 46%). The radiation was performed using a microwave synthesizer (CEM Discover). Step 1 is described below. The synthesis scheme (b-1) is shown below.

[0402] [ka]

[0403] Step 2; di-μ-chloro-bis[bis(6-methyl-4-phenylpyrimidinato) Synthesis of Iridium(III) (abbreviation: [Ir(mppm)2Cl]2) Next, 15 mL of 2-ethoxyethanol, 5 mL of water, and Hmppm1 obtained in step 1 above. 0.51g of iridium chloride hydrate (IrCl3·H2O) and 1.26g of iridium chloride hydrate (IrCl3·H2O) were placed in a reflux tubing. The contents were placed in a round-bottom flask, and the flask was purged with argon. Then, microwave (2.4 The mixture was irradiated with 5GHz (100W) for 1 hour to allow the reaction to proceed. After removing the solvent by distillation, the resulting residue was collected. The dinuclear complex [Ir(mppm)2Cl]2 was obtained by washing with ethanol and filtering. (Dark green powder, 77% yield). The synthesis scheme for Step 2 (b-2) is shown below.

[0404] [ka]

[0405] Step 3; (Acetylacetonato)bis(6-methyl-4-phenylpyrimidinato) Synthesis of Iridium(III) (abbreviation: [Ir(mppm)2(acac)]) Furthermore, 40 mL of 2-ethoxyethanol and the dinuclear complex obtained in step 2 above [Ir(mp [pm)2Cl] 21.84g, Acetylacetone 0.48g, Sodium carbonate 1.73g The solution was placed in a round-bottom flask fitted with a reflux tubing, and the contents of the round-bottom flask were replaced with argon. Then, The reaction was carried out by irradiating with microwaves (2.45 GHz, 120 W) for 60 minutes. The solvent was removed by distillation. The resulting residue was dissolved in dichloromethane and filtered to remove insoluble matter. The resulting filtrate The solution was washed with water, then saturated saline solution, and dried with magnesium sulfate. The solution was filtered. After removing the solvent from this solution by distillation, the resulting residue was obtained from dichloromethane:ethyl acetate. The sample was purified by silica gel column chromatography using a 4:1 (volume ratio) solvent-developing solvent. Subsequently, the target product was recrystallized in a mixed solvent of dichloromethane and hexane, resulting in a yellow color. It was obtained as a powder (yield 22%). The synthesis scheme for step 3 (b-3) is shown below.

[0406] [ka]

[0407] Nuclear magnetic resonance spectroscopy of the yellow powder obtained in step 3 above ( 1 Analysis results by 1H NMR The results are shown below. From these results, the organometallic complex [Ir(mppm)2(acac)] was obtained. It was discovered that...

[0408] 1H NMR.δ(CDCl3):1.78(s,6H),2.81(s,6H),5 .24(s,1H),6.37(d,2H),6.77(t,2H),6.85(t,2 H),7.61-7.63(m,4H),8.97(s,2H).

[0409] (Reference example 3) The organometallic complex used in the above examples, (acetylacetonato)bis(6-tert-butyl -4-phenylpyrimidinato)iridium(III) (also known as: bis[2-(6-tert -butyl-4-pyrimidinyl-κN3)phenyl-κC](2,4-pentanedionato- κ 2 O,O') Iridium(III) (Abbreviation: [Ir(tBuppm)2(acac) An example of the synthesis of [Ir(tBuppm)2(acac)] is shown below. vinegar.

[0410] [ka]

[0411] Step 1; 4-tert-butyl-6-phenylpyrimidine (abbreviation: HtBuppm) ) synthesis > First, 22.5g of 4,4-dimethyl-1-phenylpentane-1,3-dione and formaldehyde 50g of Mido was placed in a round-bottom flask fitted with a reflux condenser, and the inside was purged with nitrogen. This reaction vessel The reaction solution was refluxed for 5 hours by heating. After that, this solution was treated with sodium hydroxide solution. The organic layer was poured into a solution and extracted with dichloromethane. The obtained organic layer was then mixed with water and saturated saline solution. The solution was washed and dried with magnesium sulfate. The dried solution was filtered. After removing the flux by distillation, the resulting residue is dissolved in hexane:ethyl acetate = 10:1 (volume ratio) The pyrimidine derivative HtBupp was purified using silica gel column chromatography as the substrate. m was obtained (colorless oil, yield 14%). The synthesis scheme for Step 1 is shown below (c-1). vinegar.

[0412] [ka]

[0413] Step 2; Di-μ-chloro-bis[bis(6-tert-butyl-4-phenylpyryl] Synthesis of midinato iridium(III) (abbreviation: [Ir(tBuppm)2Cl]2) > Next, add 15 mL of 2-ethoxyethanol and 5 mL of water, and the HtBupp obtained in step 1 above. m1.49g, iridium chloride hydrate (IrCl3·H2O) 1.04g, attached to a reflux tube. It was placed in a round-bottom flask, and the flask was purged with argon. Then, microwave (2.4 The mixture was irradiated with 5GHz (100W) for 1 hour to allow the reaction to proceed. After removing the solvent by distillation, the resulting residue was collected. The dinuclear complex [Ir(tBuppm)2Cl]2 was obtained by suction filtration and washing with ethanol (yellow). Green powder, yield 73%. The synthesis scheme for Step 2 is shown below (c-2).

[0414] [ka]

[0415] Step 3; (Acetylacetonato)bis(6-tert-butyl-4-phenylpyryl) Iridium(III) (abbreviation: [Ir(tBuppm)2(acac)]) > Furthermore, 40 mL of 2-ethoxyethanol and the dinuclear complex [Ir(tB) obtained in step 2 above are added. [uppm)2Cl] 21.61g, acetylacetone 0.36g, sodium carbonate 1. 27g was placed in a round-bottom flask fitted with a reflux tubing, and the flask was purged with argon. The mixture was then irradiated with microwaves (2.45 GHz, 120 W) for 60 minutes to allow the reaction to proceed. The solvent was then removed by distillation. The resulting residue was filtered by suction with ethanol and washed with water and ethanol. This solid was then processed. Dissolve in chloromethane and use Celite (Wako Pure Chemical Industries, Ltd., catalog number: 531-1) The solution was filtered through a filtration aid consisting of layers of 6855), alumina, and Celite. The resulting solid is then recrystallized in a mixed solvent of dichloromethane and hexane. The target product was obtained as a yellow powder (yield 68%). The synthesis scheme for Step 3 is shown below (c-3 ) is shown.

[0416] [ka]

[0417] Nuclear magnetic resonance spectroscopy of the yellow powder obtained in step 3 above ( 1 Analysis results by 1H NMR The results are shown below. From these results, the organometallic complex [Ir(tBuppm)2(acac)] We found out what we had gained.

[0418] 1 H NMR.δ(CDCl3):1.50(s,18H),1.79(s,6H), 5.26(s,1H),6.33(d,2H),6.77(t,2H),6.85(t, 2H),7.70(d,2H),7.76(s,2H),9.02(s,2H).

[0419] (Reference example 4) The 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[ used in the above example This document describes the synthesis method for f,h]quinoxaline (abbreviation: 2mDBTPDBq-II). .

[0420] [ka]

[0421] ≪2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxa Synthesis of phosphorus (abbreviation: 2mDBTPDBq-II) 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxali The synthesis scheme for n (abbreviated as 2mDBTPDBq-II) is shown in (d-1).

[0422] [ka]

[0423] 5.3 g (20 mmol) of 2-chlorodibenzo[f,h]quinoxaline in a 2L three-necked flask. ), 3-(dibenzothiophen-4-yl)phenylboronic acid 6.1g (20 mmol) Tetrakis(triphenylphosphine)palladium(0) 460 mg (0.4 mmol) Add 300 mL of toluene, 20 mL of ethanol, and 20 mL of 2 M potassium carbonate solution. The mixture was then degassed by stirring under reduced pressure, and the inside of the three-necked flask was purged with nitrogen. This mixture was stirred under a nitrogen stream at 100°C for 7.5 hours. After cooling to room temperature, the result was obtained. The mixture was filtered to obtain a white filtrate. The obtained filtrate was then washed with water and ethanol. The material was dried. The resulting solid was dissolved in approximately 600 mL of hot toluene, and then mixed with Celite and Fluoride. The filtrate was filtered by suction through a pipe to obtain a colorless, transparent liquid. The obtained filtrate was concentrated to approximately 700 mL. Purification was performed by silica gel column chromatography. Chromatography was performed using hot toluene. The process was carried out using [a specific solvent] as the developing solvent. The resulting solid was then treated with acetone and ethanol, followed by ultrasound. After irradiation, the resulting suspension was filtered and dried, yielding a white powder of 7.85 g. It was obtained with a yield of 80%.

[0424] The above-mentioned target substance was relatively soluble in hot toluene, but was a material that tended to precipitate when it cooled. Furthermore, it was poorly soluble in other organic solvents such as acetone and ethanol. By utilizing the difference in solvability, we were able to synthesize it in good yield using a simple method as described above. After the reaction is complete, the solid precipitated by returning to room temperature is filtered out, which easily removes most impurities. It was possible to remove it in the stool. Furthermore, column chromatography using thermal toluene as the developing solvent was performed. This allowed for the easy purification of target substances that tend to precipitate.

[0425] The obtained white powder (4.0 g) was purified by sublimation using the train sublimation method. The white powder was heated at 300°C under conditions of a pressure of 5.0 Pa and an argon flow rate of 5 mL / min. The process was carried out. After sublimation purification, the target substance was obtained as a white powder with a yield of 3.5 g and an 88% yield.

[0426] Nuclear magnetic resonance spectroscopy ( 1 By 1H NMR, this compound was identified as the target product 2-[3-(di [Benzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2m It was confirmed to be DBTPDBq-II.

[0427] The obtained substance 1 The 1H NMR data is shown below. 1 H NMR(CDCl3,300MHz):δ(ppm)=7.45-7.52(m ,2H), 7.59-7.65(m,2H), 7.71-7.91(m,7H), 8.2 0-8.25(m,2H), 8.41(d,J=7.8Hz,1H), 8.65(d,J =7.5Hz,2H), 8.77-8.78(m,1H), 9.23(dd,J=7.2 Hz,1.5Hz,1H), 9.42(dd,J=7.8Hz,1.5Hz,1H), 9 .48 (s, 1H). [Explanation of Symbols]

[0428] 102 EL layer 103 First electrode 108 Second electrode 701 Hole injection layer 702 Hole transport layer 703 Emitting layer 704 Electron transport layer 705 Electron injection layer 706 Electron injection buffer layer 707 Electron relay layer 708 Composite material layer 800 First EL layer 801 Second EL layer 803 Charge generation layer 1100 circuit board 1101 First electrode 1103 Second electrode 1111 Hole injection layer 1112 Hole transport layer 1113 Emitting layer 1114a First electron transport layer 1114b Second electron transport layer 1115 Electron injection layer

Claims

1. A device comprising a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound is a carbazole compound in which the 3-position of the carbazole ring is substituted, The second organic compound is a heterocyclic compound, A light-emitting element in which the difference between the energy value of the peak of the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak of the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.3 eV.

2. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound described above is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, The second organic compound is a heterocyclic compound, A light-emitting element in which the difference between the energy value of the peak of the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak of the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.3 eV.

3. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound is a carbazole compound in which the 3-position of the carbazole ring is substituted, The second organic compound is a heterocyclic compound, A light-emitting element in which the difference between the energy value of the peak of the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak of the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.2 eV.

4. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound described above is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, The second organic compound is a heterocyclic compound, A light-emitting element in which the difference between the energy value of the peak of the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak of the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.2 eV.

5. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound is a carbazole compound in which the 3-position of the carbazole ring is substituted, The second organic compound is a heterocyclic compound, A light-emitting element in which the difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.1 eV.

6. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound described above is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, The second organic compound is a heterocyclic compound, A light-emitting element in which the difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.1 eV.

7. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound is a carbazole compound in which the 3-position of the carbazole ring is substituted, The second organic compound is a heterocyclic compound, The difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.3 eV. A light-emitting element wherein the peak of the longest wavelength absorption band of the phosphorescent compound is in the wavelength range of 490 nm to 530 nm.

8. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound described above is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, The second organic compound is a heterocyclic compound, The difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.3 eV. A light-emitting element wherein the peak of the longest wavelength absorption band of the phosphorescent compound is in the wavelength range of 490 nm to 530 nm.

9. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound is a carbazole compound in which the 3-position of the carbazole ring is substituted, The second organic compound is a heterocyclic compound, The difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.2 eV. A light-emitting element wherein the peak of the longest wavelength absorption band of the phosphorescent compound is in the wavelength range of 490 nm to 530 nm.

10. A device comprising a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound described above is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, The second organic compound is a heterocyclic compound, The difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.2 eV. A light-emitting element wherein the peak of the longest wavelength absorption band of the phosphorescent compound is in the wavelength range of 490 nm to 530 nm.

11. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound is a carbazole compound in which the 3-position of the carbazole ring is substituted, The second organic compound is a heterocyclic compound, The difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.1 eV. A light-emitting element wherein the peak of the longest wavelength absorption band of the phosphorescent compound is in the wavelength range of 490 nm to 530 nm.

12. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound described above is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, The second organic compound is a heterocyclic compound, The difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.1 eV. A light-emitting element wherein the peak of the longest wavelength absorption band of the phosphorescent compound is in the wavelength range of 490 nm to 530 nm.

13. A device comprising a pair of electrodes and a light-emitting layer between the pair of electrodes using a host material and a guest material, The host material is a mixed material of a first organic compound, which is a carbazole compound in which the 3-position of the carbazole ring is substituted, and a second organic compound, which is a heterocyclic compound. The aforementioned guest material is a phosphorescent compound, A light-emitting element in which the difference between the energy value of the peak in the emission spectrum of the thin film of the host material and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.3 eV.

14. A pair of electrodes, and a light-emitting layer between the pair of electrodes using a host material and a guest material, The host material is a mixed material of a first organic compound, which is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, and a second organic compound, which is a heterocyclic compound. The aforementioned guest material is a phosphorescent compound, A light-emitting element in which the difference between the energy value of the peak in the emission spectrum of the thin film of the host material and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.3 eV.

15. A device comprising a pair of electrodes and a light-emitting layer between the pair of electrodes using a host material and a guest material, The host material is a mixed material of a first organic compound, which is a carbazole compound in which the 3-position of the carbazole ring is substituted, and a second organic compound, which is a heterocyclic compound. The aforementioned guest material is a phosphorescent compound, A light-emitting element in which the difference between the energy value of the peak in the emission spectrum of the thin film of the host material and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.2 eV.

16. A device comprising a pair of electrodes and a light-emitting layer between the pair of electrodes using a host material and a guest material, The host material is a mixed material of a first organic compound, which is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, and a second organic compound, which is a heterocyclic compound. The aforementioned guest material is a phosphorescent compound, A light-emitting element in which the difference between the energy value of the peak in the emission spectrum of the thin film of the host material and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.2 eV.

17. A pair of electrodes, and a light-emitting layer between the pair of electrodes using a host material and a guest material, The host material is a mixed material of a first organic compound, which is a carbazole compound in which the 3-position of the carbazole ring is substituted, and a second organic compound, which is a heterocyclic compound. The aforementioned guest material is a phosphorescent compound, A light-emitting element in which the difference between the energy value of the peak of the emission spectrum of the thin film of the host material and the energy value of the peak of the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.1 eV.

18. A device comprising a pair of electrodes and a light-emitting layer between the pair of electrodes using a host material and a guest material, The host material is a mixed material of a first organic compound, which is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, and a second organic compound, which is a heterocyclic compound. The aforementioned guest material is a phosphorescent compound, A light-emitting element in which the difference between the energy value of the peak of the emission spectrum of the thin film of the host material and the energy value of the peak of the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.1 eV.

19. A device comprising a pair of electrodes and a light-emitting layer between the pair of electrodes using a host material and a guest material, The host material is a mixed material of a first organic compound, which is a carbazole compound in which the 3-position of the carbazole ring is substituted, and a second organic compound, which is a heterocyclic compound. The aforementioned guest material is a phosphorescent compound, The difference between the energy value of the peak in the emission spectrum of the thin film of the host material and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.3 eV. A light-emitting element wherein the peak of the longest wavelength absorption band of the phosphorescent compound is in the wavelength range of 490 nm to 530 nm.

20. A device comprising a pair of electrodes and a light-emitting layer between the pair of electrodes using a host material and a guest material, The host material is a mixed material of a first organic compound, which is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, and a second organic compound, which is a heterocyclic compound. The aforementioned guest material is a phosphorescent compound, The difference between the energy value of the peak in the emission spectrum of the thin film of the host material and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.3 eV. A light-emitting element wherein the peak of the longest wavelength absorption band of the phosphorescent compound is in the wavelength range of 490 nm to 530 nm.

21. A device comprising a pair of electrodes and a light-emitting layer between the pair of electrodes using a host material and a guest material, The host material is a mixed material of a first organic compound, which is a carbazole compound in which the 3-position of the carbazole ring is substituted, and a second organic compound, which is a heterocyclic compound. The aforementioned guest material is a phosphorescent compound, The difference between the energy value of the peak in the emission spectrum of the thin film of the host material and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.2 eV. A light-emitting element wherein the peak of the longest wavelength absorption band of the phosphorescent compound is in the wavelength range of 490 nm to 530 nm.

22. A pair of electrodes, and a light-emitting layer between the pair of electrodes using a host material and a guest material, The host material is a mixed material of a first organic compound, which is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, and a second organic compound, which is a heterocyclic compound. The aforementioned guest material is a phosphorescent compound, The difference between the energy value of the peak in the emission spectrum of the thin film of the host material and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.2 eV. A light-emitting element wherein the peak of the longest wavelength absorption band of the phosphorescent compound is in the wavelength range of 490 nm to 530 nm.

23. A device comprising a pair of electrodes and a light-emitting layer between the pair of electrodes using a host material and a guest material, The host material is a mixed material of a first organic compound, which is a carbazole compound in which the 3-position of the carbazole ring is substituted, and a second organic compound, which is a heterocyclic compound. The aforementioned guest material is a phosphorescent compound, The difference between the energy value of the peak in the emission spectrum of the thin film of the host material and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.1 eV. A light-emitting element wherein the peak of the longest wavelength absorption band of the phosphorescent compound is in the wavelength range of 490 nm to 530 nm.

24. A device comprising a pair of electrodes and a light-emitting layer between the pair of electrodes using a host material and a guest material, The host material is a mixed material of a first organic compound, which is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, and a second organic compound, which is a heterocyclic compound. The aforementioned guest material is a phosphorescent compound, The difference between the energy value of the peak in the emission spectrum of the thin film of the host material and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.1 eV. A light-emitting element wherein the peak of the longest wavelength absorption band of the phosphorescent compound is in the wavelength range of 490 nm to 530 nm.

25. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound is a carbazole compound in which the 3-position of the carbazole ring is substituted, The second organic compound is a heterocyclic compound, The difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.3 eV. (However, this excludes cases where the light-emitting layer contains the following compound (1-1) or the following compound 3.) 【Chemistry 1】 Light-emitting element.

26. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound described above is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, The second organic compound is a heterocyclic compound, The difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.3 eV. (However, this excludes cases where the light-emitting layer contains the following compound (1-1) or the following compound 3.) 【Chemistry 2】 Light-emitting element.

27. ​​Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound is a carbazole compound in which the 3-position of the carbazole ring is substituted, The second organic compound is a heterocyclic compound, The difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.2 eV. (However, this excludes cases where the light-emitting layer contains the following compound (1-1) or the following compound 3.) 【Transformation 3】 Light-emitting element.

28. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound described above is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, The second organic compound is a heterocyclic compound, The difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.2 eV. (However, this excludes cases where the light-emitting layer contains the following compound (1-1) or the following compound 3.) 【Chemistry 4】 Light-emitting element.

29. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound is a carbazole compound in which the 3-position of the carbazole ring is substituted, The second organic compound is a heterocyclic compound, The difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.1 eV. (However, this excludes cases where the light-emitting layer contains the following compound (1-1) or the following compound 3.) 【Transformation 5】 Light-emitting element.

30. Having a pair of electrodes and a light-emitting layer between the pair of electrodes, The light-emitting layer comprises a first organic compound, a second organic compound, and a phosphorescent compound. The first organic compound described above is a carbazole compound in which two carbazole rings are bonded to each other at the 3-position, The second organic compound is a heterocyclic compound, The difference between the energy value of the peak in the emission spectrum of a thin film of a mixed material of the first organic compound and the second organic compound and the energy value of the peak in the longest wavelength absorption band of the absorption spectrum of the phosphorescent compound is within 0.1 eV. (However, this excludes cases where the light-emitting layer contains the following compound (1-1) or the following compound 3.) 【Transformation 6】 Light-emitting element.

31. In any one of claims 1 to 30, A light-emitting element, wherein the first organic compound is a carbazole compound that is not an aromatic amine compound.

32. In any one of claims 1 to 31, The first organic compound has hole transport properties, The second organic compound is an electron-transporting light-emitting element.

33. In any one of claims 1 to 32, The phosphorescent compound is an organometallic complex, which is a light-emitting element.

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