Light emitting device

Abstract

To provide a light-emitting element having high external quantum efficiency. A light-emitting element having a long lifetime is provided.SOLUTION: The light-emitting element has a light-emitting layer containing a guest material and a host material between a pair of electrodes, wherein an emission spectrum of the host material overlaps with an absorption spectrum of the guest material, and excitation energy of the host material is converted into excitation energy of the guest material to emit phosphorescence. Since energy is smoothly transferred from the host material to the guest material by utilizing the overlap between the emission spectrum of the host material and the absorption spectrum of the guest material, the light-emitting element has high energy transfer efficiency. Thus, a light-emitting element with high external quantum efficiency can be obtained.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Organic electroluminescence (EL) phenomenon The present invention relates to a light-emitting device (hereinafter also referred to as an organic EL device) utilizing the above. [Background technology]

[0002] Research and development of organic EL elements is actively underway. The basic structure of an organic EL element is a pair of A layer containing a light-emitting organic compound (hereinafter referred to as a light-emitting layer) is sandwiched between electrodes. Lightweight type, high-speed response to input signals, and low DC voltage drive are possible. Therefore, it is attracting attention as a next-generation flat panel display element. Displays using these light-emitting elements have the advantages of excellent contrast and image quality, as well as a wide viewing angle. Furthermore, since organic EL elements are surface light sources, they can be used as backlights for LCD displays. Applications as a light source for lights and illumination are also being considered.

[0003] The light-emitting mechanism of organic EL elements is a carrier injection type. In other words, the light-emitting layer is sandwiched between electrodes. By applying a voltage, electrons and holes injected from the electrode recombine and The luminescent material is excited and emits light when the excited state returns to the ground state. The types of states include the singlet excited state (S * ) and triplet excited states (T * ) is possible. The statistical generation rate of light-emitting elements is S * :T * =1:3 are.

[0004] The ground state of luminescent organic compounds is usually a singlet state. Therefore, the singlet excited state (S * ) is called fluorescence because it is an electron transition between atoms of the same spin multiplicity. , triplet excited state (T * ) is an electron transition between different spin multiplicities, Here, a compound that emits fluorescence (hereafter referred to as a fluorescent compound) emits light at room temperature. Therefore, phosphorescence is not observed and only fluorescence is observed. The internal quantum efficiency (the ratio of photons generated to injected carriers) of a light-emitting device The theoretical limit is S * :T * It is said to be 25% based on the ratio = 1:3.

[0005] On the other hand, if a compound that emits phosphorescence (hereinafter referred to as a phosphorescent compound) is used, the internal quantum efficiency can be increased to 1 In other words, it is possible to obtain a higher luminous efficiency than fluorescent compounds. For this reason, in order to realize a highly efficient light-emitting device, phosphorescent compounds are used. In recent years, the development of light-emitting devices using phosphorescent compounds has been actively pursued. Due to the high phosphorescence quantum yield of iridium, organometallic complexes with iridium as the central metal have attracted attention. For example, Patent Document 1 discloses that an organometallic complex having iridium as the central metal is a phosphorescent material. and is disclosed as such.

[0006] When the light-emitting layer of the light-emitting element is formed using the above-mentioned phosphorescent compound, the concentration quenching of the phosphorescent compound is To suppress quenching by light and triplet-triplet annihilation, the compound is placed in a matrix of other compounds. In most cases, the phosphorescent compound is dispersed in a matrix. The compound is the host material, and the compound dispersed in the matrix, such as a phosphorescent compound, is the guest material. It is called a fee. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 00 / 70655 Brochure Summary of the Invention [Problem to be solved by the invention]

[0008] However, the light extraction efficiency of organic EL elements is generally said to be around 20% to 30%. Therefore, when considering the absorption of light by the reflective electrode and transparent electrode, it is recommended to use a phosphorescent compound. The limit of external quantum efficiency of light-emitting devices is thought to be about 25%.

[0009] In view of the above, an object of one embodiment of the present invention is to provide a light-emitting element with high external quantum efficiency. Another object of one embodiment of the present invention is to provide a light-emitting element with a long lifetime. [Means for solving the problem]

[0010] One embodiment of the present invention is a light-emitting device having 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, This light-emitting element emits phosphorescence when energy is converted into excitation energy of the guest material. be.

[0011] Further, one embodiment of the present invention is a light-emitting device having a light-emitting layer including a guest material and a host material between a pair of electrodes. The longest wavelength ( The excitation energy of the host material overlaps with the absorption band of the guest material. It is a light-emitting element that emits phosphorescence when converted into energy.

[0012] In the above light-emitting device, the absorption band on the longest wavelength side is triplet MLCT (Metal to It is preferred to include absorption due to Ligand Charge Transfer (LCT) transitions. It's nice.

[0013] In the light-emitting device, the emission spectrum of the host material is preferably a fluorescent spectrum. stomach.

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

[0015] In the light-emitting element, the peak energy value of the emission spectrum and the peak energy value of the absorption spectrum are The difference between the energy value of the absorption band peak on the low energy side and the energy value of the absorption band peak on the high energy side is within 0.3 eV. preferable.

[0016] In the light-emitting device, the molar absorption coefficient of the absorption band on the longest wavelength side of the absorption spectrum is 50 00M -1 ·cm -1 It is preferable that this is equal to or greater than this. [Effects of the Invention]

[0017] According to one embodiment of the present invention, a light-emitting element with high external quantum efficiency can be provided. In one embodiment, a light-emitting element with a long lifetime can be provided. [Brief explanation of the drawings]

[0018] [Figure 1] 3A and 3B are diagrams showing absorption spectra and emission spectra according to Example 1. FIG. [Figure 2] 1A and 1B are diagrams showing the structure of a light-emitting element according to an embodiment; [Figure 3] FIG. 10 is a graph showing current density-luminance characteristics of the light-emitting element of Example 2. [Figure 4] FIG. 10 is a graph showing voltage-luminance characteristics of the light-emitting element of Example 2. [Figure 5] FIG. 10 shows luminance-current efficiency characteristics of the light-emitting element of Example 2. [Figure 6] FIG. 10 is a graph showing luminance-external quantum efficiency characteristics of the light-emitting element of Example 2. [Figure 7] FIG. 10 shows an emission spectrum of the light-emitting element of Example 2. [Figure 8] 10 shows the results of a reliability test of the light-emitting element of Example 2. FIG. [Figure 9] FIG. 10 is a graph showing current density-luminance characteristics of the light-emitting element of Example 3. [Figure 10] FIG. 10 is a graph showing voltage-luminance characteristics of the light-emitting element of Example 3. [Figure 11] FIG. 10 shows luminance-current efficiency characteristics of the light-emitting element of Example 3. [Figure 12] FIG. 10 is a graph showing luminance-external quantum efficiency characteristics of the light-emitting element of Example 3. [Figure 13] FIG. 10 shows an emission spectrum of the light-emitting element of Example 3. [Figure 14] FIG. 10 shows the results of a reliability test of the light-emitting element of Example 3. [Figure 15] 1A and 1B illustrate light-emitting elements of one embodiment of the present invention. [Figure 16] 3A and 3B are diagrams showing absorption spectra and emission spectra according to Example 1. FIG. [Figure 17] 10A and 10B are diagrams showing absorption spectra and emission spectra according to Example 4. [Figure 18] FIG. 10 is a graph showing current density-luminance characteristics of the light-emitting element of Example 5. [Figure 19] FIG. 10 shows voltage-luminance characteristics of the light-emitting element of Example 5. [Figure 20] FIG. 10 shows luminance-current efficiency characteristics of the light-emitting element of Example 5. [Figure 21] FIG. 10 is a graph showing luminance-external quantum efficiency characteristics of the light-emitting element of Example 5. [Figure 22] FIG. 10 shows an emission spectrum of the light-emitting element of Example 5. [Figure 23] 10 shows an absorption spectrum and an emission spectrum according to Example 6. FIG. [Figure 24] FIG. 11 is a graph showing current density-luminance characteristics of the light-emitting element of Example 7. [Figure 25] FIG. 11 shows voltage-luminance characteristics of the light-emitting element of Example 7. [Figure 26] FIG. 10 shows luminance-current efficiency characteristics of the light-emitting element of Example 7. [Figure 27] FIG. 10 is a graph showing the luminance-external quantum efficiency characteristics of the light-emitting element of Example 7. [Figure 28] FIG. 10 shows an emission spectrum of the light-emitting element of Example 7. [Figure 29] FIG. 10 shows the results of a reliability test of the light-emitting element of Example 7. [Figure 30] FIG. 10 shows the absorption spectrum and the emission spectrum according to Example 8. [Figure 31] FIG. 10 is a graph showing current density-luminance characteristics of the light-emitting element of Example 9. [Figure 32] FIG. 10 shows voltage-luminance characteristics of the light-emitting element of Example 9. [Figure 33] FIG. 10 shows luminance-current efficiency characteristics of the light-emitting element of Example 9. [Figure 34] FIG. 10 is a graph showing luminance-external quantum efficiency characteristics of the light-emitting element of Example 9. [Figure 35] FIG. 10 shows an emission spectrum of the light-emitting element of Example 9. [Figure 36] FIG. 10 shows the results of a reliability test of the light-emitting element of Example 9. [Figure 37] FIG. 10 shows absorption spectra and emission spectra according to Example 10. [Figure 38] FIG. 16 shows current density-luminance characteristics of the light-emitting element of Example 11. [Figure 39] FIG. 16 shows voltage-luminance characteristics of the light-emitting element of Example 11. [Figure 40] FIG. 16 shows luminance-current efficiency characteristics of the light-emitting element of Example 11. [Figure 41] FIG. 16 is a graph showing luminance-external quantum efficiency characteristics of the light-emitting element of Example 11. [Figure 42] FIG. 16 shows an emission spectrum of the light-emitting element of Example 11. [Figure 43]FIG. 16 shows the absorption spectrum and the emission spectrum according to Example 12. [Figure 44] FIG. 13 shows current density-luminance characteristics of the light-emitting element of Example 13. [Figure 45] FIG. 13 shows voltage-luminance characteristics of the light-emitting element of Example 13. [Figure 46] FIG. 13 shows luminance-current efficiency characteristics of the light-emitting element of Example 13. [Figure 47] FIG. 13 shows luminance-external quantum efficiency characteristics of the light-emitting element of Example 13. [Figure 48] FIG. 13 shows an emission spectrum of the light-emitting element of Example 13. [Figure 49] FIG. 16 shows the absorption spectrum and the emission spectrum according to Example 14. [Figure 50] FIG. 16 shows current density-luminance characteristics of the light-emitting element of Example 15. [Figure 51] FIG. 16 shows voltage-luminance characteristics of the light-emitting element of Example 15. [Figure 52] FIG. 16 shows luminance-current efficiency characteristics of the light-emitting element of Example 15. [Figure 53] FIG. 16 shows the luminance-external quantum efficiency characteristics of the light-emitting element of Example 15. [Figure 54] FIG. 16 shows an emission spectrum of the light-emitting element of Example 15. DETAILED DESCRIPTION OF THE INVENTION

[0019] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description. The present invention is not limited to the above embodiments, and various changes and modifications may be made in the form and details thereof without departing from the spirit and scope of the present invention. It will be readily understood by those skilled in the art that the present invention can be achieved by the following embodiments. It should not be construed as being limited to the contents of the description. The same reference numerals are used in different drawings to denote the same parts or parts having similar functions. A repeated explanation will be omitted.

[0020] (Embodiment 1) In this embodiment, a light-emitting element of one embodiment of the present invention will be described.

[0021] The light-emitting element of this embodiment mode comprises a guest material, which is a light-emitting substance, and a host material in which the guest material is dispersed. The light-emitting layer contains a host material and a guest material. As the binder, one or more organic compounds can be used.

[0022] By dispersing the guest material in the host material, crystallization of the light-emitting layer is suppressed. In addition, concentration quenching caused by a high concentration of the guest material can be suppressed, and the light-emitting element can be The luminous efficiency can be increased.

[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 triplet excitation of the guest material that contributes to the emission This is because the host material quenches the photoelectric energy, resulting in a decrease in luminous efficiency. be.

[0024] <Elemental process of luminescence> First, we will explain the general elementary process of light emission in a light-emitting device that uses a phosphorescent compound as a guest material. explain.

[0025] (1) When electrons and holes recombine in the guest molecule, 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 The guest molecule in the singlet excited state undergoes intersystem crossing to the triplet excited state, emitting phosphorescence.

[0026] In other words, in the direct recombination process (1) above, the intersystem crossing efficiency and phosphorescence intensity of the guest molecules If the molecular yield is high, high luminous efficiency can be obtained. 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, 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 The excitation energy is transferred to the guest molecule, and the guest molecule enters a triplet excited state. The guest molecule emits phosphorescence. Although energy transfer to the S1 level of the guest molecule is formally possible, in most cases the energy transfer is to the S1 level of the guest molecule. is located on the higher energy side than the T1 level of the host molecule, and is the main energy transfer pathway. Since it is difficult to achieve this level, we will not go into detail 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 excited state or a triplet excited state. The guest molecule in the triplet excited state emits phosphorescence. The guest molecule in this state undergoes intersystem crossing to a triplet excited state and emits phosphorescence.

[0028] In other words, in the energy transfer process (2) above, the triplet excitation energy of the host molecule It is important to transfer both the singlet and singlet excitation energy to the guest molecule efficiently. This becomes:

[0029] <Energy transfer process> The energy transfer process between molecules is explained in detail below.

[0030] First, the following two mechanisms have been proposed for intermolecular energy transfer: The molecule that provides the excitation energy is the host molecule, and the molecule that receives the excitation energy is the 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 vibration between the molecule and the guest molecule. The host molecule transfers energy to the guest molecule through the vibrational resonance phenomenon, and the host molecule The guest molecule enters the excited state. The rate constant of the Förster mechanism is k h * →g of This is shown in equation (1).

[0032]

number

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

[0034] Dexter mechanism (electron exchange interaction) The Dexter mechanism occurs when the host and guest molecules approach the effective contact distance where orbital overlap occurs. The energy is transferred through the exchange of electrons of the excited host molecule and the ground state guest molecule. -Transfer occurs. The rate constant of the Dexter mechanism is k h * →g is shown in equation (2).

[0035]

number

[0036] In equation (2), h is Planck's constant, and K is a constant with the dimension of energy. where ν represents the frequency and f' h (ν) is the normalized emission spectrum of the host molecule (When discussing energy transfer from the singlet excited state, the fluorescence spectrum, triplet excited state represents the phosphorescence spectrum when discussing energy transfer from g (ν) is a guest represents the normalized absorption spectrum of the molecule, L represents the effective molecular radius, and R represents the effective molecular radius of the host molecule. Represents the intermolecular distance between the child and guest molecules.

[0037] Here, the energy transfer efficiency from the host molecule to the guest molecule Φ ET is expressed by equation (3). It is thought that r The emission process of the host molecule (energy transfer from the singlet excited state) The rate of fluorescence is used when discussing the energy transfer from the triplet excited state, and the rate of phosphorescence is used when discussing the energy transfer from the triplet excited state. represents the coefficient constant, k n represents the rate constant of the non-radiative process (thermal deactivation and intersystem crossing) of the host molecule. , 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 To increase the The rate constant k h * →g , other competing rate constants k r +k n (=1 / τ) Then, the rate constant of the energy transfer, k h * →g To increase From equations (1) and (2), it is possible to determine whether the mechanism is a Forster mechanism or a Dexter mechanism. In the structure, the emission spectrum of the host molecule (energy transfer from the singlet excited state) When discussing energy transfer from triplet excited states, we use the fluorescence spectrum. It can be seen that it is better for the absorption spectrum of the guest molecule to overlap as much as possible.

[0040] Here, one embodiment of the present invention is a light-emitting device in which a light-emitting layer containing a guest material and a host material is disposed between a pair of electrodes. The emission spectrum of the host material overlaps with the absorption spectrum of the guest material, The excitation energy of the source is converted into the excitation energy of the guest material, resulting in a phosphorescent light-emitting device. It is an optical element.

[0041] In one embodiment of the present invention, the emission spectrum of the host material and the absorption spectrum of the guest material overlap. By utilizing this, energy transfer from the host material to the guest material is smooth, Therefore, in one embodiment of the present invention, a light-emitting element with high external quantum efficiency is The child can be realized.

[0042] In addition, considering the energy transfer process described above, the excitation energy is transferred from the host molecule to the guest molecule. Before the transfer of the electrons, the host molecule itself releases its excitation energy as light or heat and is deactivated. However, in one embodiment of the present invention, Since energy transfer is smooth, deactivation of excitation energy can be suppressed. Therefore, a light emitting element with a long life can be realized.

[0043] Here, the present inventors have investigated the relationship between the emission spectrum of the host molecule and the absorption spectrum of the guest molecule. When considering the overlap, the longest wavelength (lowest energy) in the absorption spectrum of the guest molecule The absorption bands on the side were considered to be important.

[0044] In this embodiment, a phosphorescent compound is used as the guest material. In the ion-excited atmosphere, the absorption band that is thought to contribute most strongly to the emission is the singlet ground state The absorption wavelength corresponding to the direct transition to the triplet excited state and its vicinity are the longest wavelengths. This is the absorption band that appears in the emission spectrum (fluorescence spectrum and The absorption band of the phosphorescent compound overlaps with the absorption band at the longest wavelength. It is considered preferable.

[0045] For example, in organometallic complexes, especially luminescent iridium complexes, the longest wavelength absorption band is , often appearing as a broad absorption band around 500-600 nm (of course, the emission wavelength (Depending on the wavelength, it may appear on the shorter or longer wavelength side.) This absorption band is mainly Triplet MLCT (Metal to Ligand Charge Transfer) r) transition. However, this absorption band contains triplet π-π * transition or singlet MLCT transition These overlap and are blown to the longest wavelength side of the absorption spectrum. Therefore, it is considered that the guest material is an organic metal complex (especially When using an iridium complex as the ion source, the broad absorption spectrum at the longest wavelength is It is preferable that the emission spectrum of the band largely overlaps with that of the host material.

[0046] Therefore, one aspect of the present invention is to provide a light-emitting device including a guest material and a host material between a pair of electrodes. The emission spectrum of the host material and the absorption spectrum of the guest material are the longest. The absorption band of the host material overlaps with the absorption band of the guest material. is a light-emitting element that emits phosphorescence when converted into

[0047] In the above light-emitting device, it is preferable that the absorption band includes absorption due to triplet MLCT transition. The triplet MLCT excited state is the lowest triplet excited state of the phosphorescent compound that is the guest material. Since this is the triplet MLCT state, phosphorescent compounds emit phosphorescence from this excited state. From the excited state, there are few deactivation processes other than luminescence, and the rate of existence of this excited state is maximized. For this reason, triplet MLCT transition is considered to be the most important factor in determining the luminescence efficiency. Direct energy transfer from the host material to the triplet MLCT excited state is utilized. It can be said that it is preferable that there are many energy transfer processes. 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 (above (2-2)), Compared to the case where the compound is in a singlet excited state (above (2-1)), the guest molecule is a phosphorescent compound. It was found that the energy transfer between the two materials is difficult to occur and the luminous efficiency is easily reduced. I noticed this.

[0049] Fluorescent compounds are usually used as host materials, and their fluorescence lifetime (τ) is in the nanosecond range. Level and very short (k r +k n This is because the electrons in the singlet excited state are converted to the ground state (singlet This is because the transition to the nucleon (doublet) is an allowed transition. From equation (3), this means that the energy transfer efficiency Rate Φ ET Taking this into consideration, the singlet excited state of the host material Energy transfer to the guest material generally tends to be difficult.

[0050] However, one aspect of the present invention is to convert such a host material into a guest material from the singlet excited state. This overcomes the problem of the efficiency of energy transfer to the material. The optical element has a light-emitting layer containing a guest material and a host material between a pair of electrodes, and the host material The fluorescence spectrum of the guest material overlaps with the longest wavelength absorption band in the absorption spectrum. By utilizing the overlap, the excitation energy of the host material is converted into the excitation energy of the guest material. It is preferable that the compound emits phosphorescence by being converted to a compound.

[0051] That is, in the light-emitting element of one embodiment of the present invention, the fluorescence spectrum of the host material is The absorption spectrum 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. By adopting such a configuration, it is possible to suppress the deactivation of singlet excitation energy. Therefore, the single layer structure of the host material, which is thought to affect not only the efficiency but also the lifetime of the device, By applying one embodiment of the present invention, deactivation of the excitation energy can be suppressed, It is possible to realize a light-emitting element having a long life. The energy transfer from the fluorescein to the phosphorescent compound is sufficient, and the fluorescence emission from the singlet excited state is substantial. It is preferable that the above-mentioned phenomenon is not observed.

[0052] In order to fully overlap the emission spectrum of the host material and the absorption spectrum of the guest material, is the energy value of the peak of the emission spectrum and the lowest energy side of the absorption spectrum. It is preferable that the difference between the energy value of the absorption band peak is within 0.3 eV. Preferably, it is within 0.2 eV, and particularly preferably within 0.1 eV.

[0053] Furthermore, the Förster mechanism is important for energy transfer from the singlet excited state of the host material. Considering this, it is considered that the longest wavelength of the guest material is The molar absorption coefficient of the absorption band is 2000M -1 ·cm -1 More than 5000M is preferable. -1 ·cm -1 The above is more preferable.

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

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

[0056] FIG. 15(A) shows a light-emitting device having an EL layer 102 between a first electrode 103 and a second electrode 108. 15(A) is a diagram showing an optical element. The light emitting element in FIG. 15(A) has a first electrode 103 and a second electrode 104. A hole injection layer 701, a hole transport layer 702, a light emitting layer 703, an electron transport layer 704, and an electron It is composed of a dopant injection layer 705 and a second electrode 108 provided thereon.

[0057] The first electrode 103 is made of a metal or alloy having a large work function (specifically, 4.0 eV or more). , conductive compounds, and mixtures thereof are preferably used. , indium tin oxide (ITO), silicon or Indium oxide-tin oxide and indium oxide-zinc oxide (Indium oxide) containing silicon oxide Indium oxide containing tungsten oxide and zinc oxide These conductive metal oxide films are usually formed by sputtering. However, it can also be produced by applying the sol-gel method. The indium-zinc oxide film is a target in which 1 to 20 wt% of zinc oxide is added to indium oxide. The IWZO film can be formed by sputtering using a SiO2 nozzle. Contains 0.5 to 5 wt% tungsten oxide and 0.1 to 1 wt% zinc oxide relative to indium It can be formed by sputtering using a target having a graphite layer. Phen, gold, platinum, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, Examples include palladium, nitrides of metal materials (for example, titanium nitride), and the like.

[0058] However, the layer of the EL layer 102 formed in contact with the first electrode 103 is an organic compound, which will be described later. When the electrode is formed using a composite material made by mixing a compound and an electron acceptor, The material used for the first electrode 103 may be any of various metals, alloys, and Electrically conductive compounds and mixtures thereof can be used. For example, aluminum It is also possible to use alloys containing aluminum, silver, and aluminum (for example, Al-Si).

[0059] The first electrode 103 is formed by, for example, sputtering or vapor deposition (including vacuum deposition). It can be achieved.

[0060] The second electrode 108 is made of a metal, alloy, or electrode having a small work function (preferably 3.8 eV or less). It is preferable to form the conductive layer using a conductive compound or a mixture thereof. Elements in Groups 1 and 2 of the periodic table, i.e., alkalis such as lithium and cesium Alkaline earth metals such as lithium metals, calcium, strontium, magnesium, and the like Alloys containing these elements (e.g., Mg-Ag, Al-Li), europium, ytterbium, etc. In addition to rare earth metals and alloys containing these, aluminum, silver, etc. can also be used.

[0061] However, the layer of the EL layer 102 formed in contact with the second electrode 108 is an organic compound, which will be described later. When a composite material is used in which a compound and an electron donor (donor) are mixed, the work function is large. Regardless of size, indium oxide containing Al, Ag, ITO, silicon or silicon oxide A variety of conductive materials can be used, such as tin oxide.

[0062] When forming the second electrode 108, a vacuum deposition method or a sputtering method may be used. In addition, when using silver paste, the coating method or inkjet method can be used. It can be used.

[0063] The EL layer 102 has at least a light-emitting layer 703. A known material is used in a part of the EL layer 102. It is also possible to use either a low molecular weight compound or a high molecular weight compound. The material forming the EL layer 102 is not limited to materials consisting of only organic compounds. This also includes a configuration that partially contains an inorganic compound.

[0064] The EL layer 102 includes a light-emitting layer 703 and a material having a high hole injection property as shown in FIG. a hole injection layer 701 containing a material with high hole transport properties; a hole transport layer 702 containing a material with high hole transport properties; an electron transport layer 704 containing a substance with high electron transport properties; It is formed by appropriately combining and laminating the electron injection layer 705 and the like.

[0065] The hole-injection layer 701 is a layer containing a substance with a high hole-injection property. The oxides are molybdenum oxide, titanium oxide, vanadium oxide, rhenium oxide, ruthenium oxide, Aluminum oxide, Chromium oxide, Zirconium oxide, Hafnium oxide, Tantalum oxide, Silver Metal oxides such as oxides of tungsten, manganese, etc. can be used. Phthalocyanine (abbreviation: HPc), copper(II) phthalocyanine (abbreviation: CuPc) Phthalocyanine compounds such as the above can be used.

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

[0067] Furthermore, polymeric compounds (oligomers, dendrimers, polymers, etc.) can also be used. For example, poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriflate) Phenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenyl (N'-phenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide (abbreviation: PTPDMA), poly[N,N'-bis(4-butylphenyl)-N,N'-bi Examples include polymer compounds such as [poly(phenyl)benzidine] (abbreviation: Poly-TPD). In addition, poly(3,4-ethylenedioxythiophene) / poly(styrenesulfonic acid) (PEDOT / PSS), polyaniline / poly(styrene sulfonate) (PAni / PS A polymer compound to which an acid such as methyl methyl stearate (S) is added can be used.

[0068] The hole injection layer 701 is formed by mixing an organic compound and an electron acceptor. Such composite materials may be used in which the electron acceptor is attached to the organic compound. Since holes are generated, the organic compound has excellent hole injection and hole transport properties. The material is preferably a material that is excellent in transporting generated holes (a material with high hole transport properties). It's nice.

[0069] The organic compounds used in the composite materials include aromatic amine compounds, carbazole derivatives, aromatic Various compounds such as aromatic hydrocarbons and polymer compounds (oligomers, dendrimers, polymers, etc.) As the organic compound used for the composite material, a compound having a high hole transporting property can be used. It is preferable that the organic compound is a low-molecular-weight organic compound. -6 cm 2 Hole transfer above / Vs However, it is preferable that the material has a higher hole transporting property than the electron transporting property. In the following, organic compounds that can be used in composite materials will be described. The compounds are specifically listed below.

[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 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-anthryl)phenyl] phenyl]-9H-carbazole (abbreviation: PCzPA), 1,4-bis[4-(N-carbazole) Carbazole derivatives such as [2,3,5,6-tetraphenyl]-2,3,5,6-zolylphenyl can be used.

[0071] In addition, 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, and other aromatic compounds Aromatic hydrocarbon compounds can be used.

[0072] Furthermore, 2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9'-bianthryl, 10,10'-diphenyl-9,9'-bianthryl, 10, 10'-bis(2-phenylphenyl)-9,9'-bianthryl, 10,10'-bis [(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bianthryl, Thracene, tetracene, rubrene, perylene, 2,5,8,11-tetra(tert-buthylene) (ethyl)perylene, pentacene, coronene, 4,4'-bis(2,2-diphenylvinyl) Biphenyl (abbreviation: DPVBi), 9,10-bis[4-(2,2-diphenylvinyl) Aromatic hydrocarbon compounds such as diphenylanthracene (abbreviation: DPVPA) can be used. can.

[0073] The electron acceptor is 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroethylene. Organic compounds such as fluoroquinodimethane (abbreviated as F4-TCNQ) and chloranil, and transition metals In addition, metal oxides belonging to groups 4 to 8 of the periodic table can be used. Specifically, vanadium oxide, niobium oxide, tantalum oxide, Chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide are electrically Among them, molybdenum oxide is particularly stable in the atmosphere and has a high molecular acceptability. It is preferred because it has low moisture content and is easy to handle.

[0074] In addition, the above-mentioned polymer compounds such as PVK, PVTPA, PTPDMA, and Poly-TPD A composite material may be formed using the above-described electron acceptor and used for the hole-injection layer 701.

[0075] The hole transport layer 702 is a layer containing a substance with a high hole transport property. NPB, TPD, BPAFLP, 4,4'-bis[N-(9,9-dimethylfluoromethyl] 4,4-Diphenyl-2-yl)-N-phenylamino]biphenyl (abbreviation: DFLDPBi), '-Bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino] Aromatic amine compounds such as biphenyl (abbreviation: BSPB) can be used. The substances mentioned are mainly 10 -6 cm 2 / Vs or more. Any substance other than these may be used as long as it has a higher hole transporting property than an electron transporting property. The layer containing a substance with a high hole transporting property may be a single layer or may be two or more layers containing the above substance. It may also be laminated on top.

[0076] The hole transport layer 702 may also contain carbazole derivatives such as CBP, CzPA, and PCzPA. Anthracene derivatives such as t-BuDNA, DNA, and DPAnth may also be used. stomach.

[0077] The hole transport layer 702 may be made of a material such as PVK, PVTPA, PTPDMA, or Poly-TPD. Any polymeric compound can be used.

[0078] The light-emitting layer 703 is a layer containing a light-emitting substance. The host material may be a material selected from a plurality of materials. See State 1.

[0079] As the phosphorescent compound of the guest material, an organometallic complex is preferable, and an iridium complex is particularly preferable. In addition, considering the energy transfer by the Förster mechanism described above, phosphorescent compounds The molar absorption coefficient of the absorption band located at the longest wavelength of the substance is 2000M -1 ·cm -1 The above Preferably 5000M -1 ·cm -1 More preferably, such a large molar absorptivity coefficient is Specific examples of compounds having the above number include bis(3,5-dimethyl-2-phenylpyrazine) Nato)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(mppr-Me )2(dpm)]) and (acetylacetonato)bis(4,6-diphenylpyrimidinato) ) Iridium(III) (abbreviation: [Ir(dppm)2(acac)]), bis(2,3 ,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation :[Ir(tppr)2(dpm)]), (acetylacetonato)bis(6-methyl-4 -phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)2(aca c)]), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidin Nat(II) iridium(III) (abbreviation: [Ir(tBuppm)2(acac)]) In particular, compounds with a molar absorption coefficient of 50, such as [Ir(dppm)2(acac)], are 00M -1 ·cm -1 If materials that achieve this or higher are used, the external quantum efficiency will reach approximately 30%. A highly efficient light emitting element can be obtained.

[0080] The host material is a compound that readily accepts electrons (typically a heterocyclic compound) and a hole and a compound that readily accepts hydroxybenzoates (typically, an aromatic amine compound or a carbazole compound). It is preferable to use a mixed material. By using such a structure, the hole The effect of improving the luminous efficiency and lifetime by balancing the carriers between the electron transport and the electron transport Specific examples of the host material include 2-[3-(dibenzothiophene)-2-(dibenzothiophene)]. phen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPD Bq-II) and 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl) Materials containing triphenylamine (abbreviated as PCBA1BP) and 2mDBTPDBq- II and 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazole- 3-yl)triphenylamine (abbreviation: PCBNBB), or 2-[ 4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f, h] A mixture of quinoxaline (abbreviated as 2CzPDBq-III) and PCBNBB, 2 -[4-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzoyl Midazole (abbreviation: DBTBIm-II) and 4,4',4''-tris[N-(1-naphthalene) (1'-TNATA) In addition, 4,4'-bis[N-(1-naphthyl)-N-phenyl [amino]biphenyl (abbreviation: NPB), 4-(1-naphthyl)-4'-phenyltriphenyl Nylamine (abbreviation: αNBA1BP), 2,7-bis[N-(4-diphenylaminophenyl) N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPA2SF ), 9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carba PCCP or 1'-TNATA was mixed with 2mDBTPDBq-II. However, the host material is not limited to these. Other known host materials can be used.

[0081] In addition, by providing multiple light-emitting layers and making each layer emit a different color, the entire light-emitting element can be As a result, light of a desired color can be obtained. For example, in a light-emitting device having two light-emitting layers, In this case, the luminescent color of the first luminescent layer and the luminescent color of the second luminescent layer are made to have a complementary color relationship. It is also possible to obtain a light emitting element that emits white light as a whole. refers to the relationship between colors that become achromatic when mixed. In other words, it is a color that emits colors that are complementary to each other. By mixing the light obtained from the materials, white light can be obtained. The same applies to the above light emitting elements.

[0082] The electron-transporting layer 704 is a layer containing a substance with a high electron-transporting property. The following is a list of aluminum compounds: Alq3, tris(4-methyl-8-quinolinolato)aluminum (abbreviated as Alm q3), bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq 2), BAlq, Zn(BOX)2, bis[2-(2-hydroxyphenyl)benzothiazolinone] Zn(BTZ)2 and other metal complexes. -biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazo PBD, 1,3-bis[5-(p-tert-butylphenyl)-1,3 ,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 3-(4-ter t-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triacontria TAZ (abbreviation: TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)- p-EtTA Z), bathophenanthroline (abbreviated as BPhen), bathocuproine (abbreviated as BCP) , 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: Bz Heteroaromatic compounds such as poly(2,5-pyridine-Os) can also be used. diyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl) -co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), poly[(9,9-di octylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl) Polymer compounds such as PF-BPy can also be used. The substances that were found were mainly 10 -6 cm 2 It is a substance with an electron mobility of 1 / Vs or more. Any substance other than those mentioned above may be used for the electron transport layer as long as it has a higher electron transporting property than the above-mentioned substances. stomach.

[0083] The electron transport layer may be a single layer or a laminate of two or more layers made of the above-mentioned materials. It may also be possible to

[0084] The electron injection layer 705 is a layer containing a substance with a high electron injection property. lithium, cesium, calcium, lithium fluoride, cesium fluoride, calcium fluoride, Alkali metals, alkaline earth metals, or compounds thereof, such as lithium oxide, are used. Also, rare earth metal compounds such as erbium fluoride can be used. In addition, the above-described materials for forming the electron transporting layer 704 can also be used.

[0085] Alternatively, the electron injection layer 705 may be formed of a compound material obtained by mixing an organic compound and an electron donor (donor). Such composite materials are formed by adding electrons to an organic compound via an electron donor. In this case, the organic compound It is preferable that the material is excellent in transporting the generated electrons. Specifically, for example, The material (metal complex, heteroaromatic compound, etc.) constituting the electron transport layer 704 can be used. The electron donor may be any substance that exhibits electron donating properties to organic compounds. In particular, alkali metals, alkaline earth metals and rare earth metals are preferred, and lithium, cesium , magnesium, calcium, erbium, ytterbium, etc. Potassium metal oxides and alkaline earth metal oxides are preferred, and lithium oxide and calcium oxide are also preferred. Examples include barium oxide and the like. Lewis bases such as magnesium oxide are also used. It is also possible to use organic compounds such as tetrathiafulvalene (TTF). It is also possible.

[0086] The hole injection layer 701, the hole transport layer 702, the light emitting layer 703, and the electron transport layer 704 The electron injection layer 705 is formed by a deposition method (including a vacuum deposition method), an ink jet method, a coating method, respectively. It can be formed by a method such as a fabric method.

[0087] As shown in FIG. 15(B), the EL layer is formed by multiple layers between the first electrode 103 and the second electrode 108. In this case, the first EL layer 800 and the second EL layer 80 It is preferable to provide a charge generating layer 803 between the above-mentioned layers. The charge generating layer 803 can be formed of a layer made of a composite material and another material. In this case, the layer made of the other material may be a layer made of an electron donor. A layer containing a conductive material and a material with high electron transport properties, a layer made of a transparent conductive film, or the like can be used. A light-emitting element having such a structure can cause problems such as energy transfer and quenching. This will allow for a wider range of material choices, resulting in light-emitting devices with both high luminous efficiency and long life. It is also easy to obtain phosphorescence in one EL layer and fluorescence in the other. This structure can be used in combination with the above-mentioned EL layer structure.

[0088] In addition, by making the luminescent color of each EL layer different, the desired luminescent color can be obtained as a whole. For example, in a light-emitting element having two EL layers, the first By making the luminescent color of the first EL layer and the luminescent color of the second EL layer complementary to each other, It is also possible to obtain a light-emitting device that emits white light as a whole. The same applies to the case of a light emitting element having a

[0089] As shown in FIG. 15(C), the EL layer 102 is formed by connecting the first electrode 103 and the second electrode 108. Between them, there 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 705. the input buffer layer 706, the electronic relay layer 707, and the composite layer in contact with the second electrode 108. 708.

[0090] By providing the composite material layer 708 in contact with the second electrode 108, it is possible to form a thin film by using a sputtering method in particular. Therefore, when the second electrode 108 is formed, damage to the EL layer 102 can be reduced. The composite material layer 708 is preferably formed using the above-described organic compound having a high hole transporting property. Composite materials containing acceptor 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 Since the injection barrier between the composite material layer 708 and the electrode 704 can be reduced, the electrons generated in the composite material layer 708 can be injected into the electrode 704. The electron transport layer 704 can be easily injected.

[0092] The electron injection buffer layer 706 contains an alkali metal, an alkaline earth metal, a rare earth metal, and and their compounds (alkali metal compounds (oxides such as lithium oxide, halides, carbonates) Alkaline earth metal compounds (including carbonates such as lithium and cesium carbonate), oxides, halides compounds of rare earth metals (including oxides, halides, carbonates) or rare earth metal compounds (including oxides, halides, carbonates) It is possible to use a substance with high electron injection properties, such as tetrahydrofuran (Tetrahydrofuran) and tetrahydrofuran (Tetrahydrofuran).

[0093] The electron-injecting buffer layer 706 is formed by containing a substance with high electron transporting properties and a donor substance. When the compound is formed, the mass ratio to the substance having high electron transport properties is 0.001 or more and 0.1 or less It is preferable to add the donor substance in the ratio of Alkali metals, alkaline earth metals, rare earth metals, and their compounds (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 group (including oxides, halides, and carbonates), tetrathianaphthacene (abbreviated Organic compounds such as TTN, nickelocene, and decamethylnickelocene can also be used. Note that the substance with a high electron transporting property can be the same as the material of the electron transporting layer 704 described above. The various materials can be used to form the substrate.

[0094] Furthermore, an electron relay layer 707 is formed between the electron injection buffer layer 706 and the composite material layer 708. The electron relay layer 707 is not necessarily provided, but it is preferable to form the electron relay layer 707. By providing the electron relay layer 707 with high transportability, electrons can be transferred 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 is composed of an acceptor material contained in a 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 to inhibit each other's functions. Therefore, an increase in the driving voltage can be prevented.

[0096] The electron relay layer 707 contains a substance with high electron transport properties, and the LUM of the substance with high electron transport properties The O level is determined by the LUMO level of the acceptor material contained in the composite material layer 708 and the electron transport The layer 704 is formed so as to have a LUMO level between that of the highly electron-transporting substance contained in the layer 704 . In addition, when the electron relay layer 707 contains a donor material, the donor phase of the donor material The LUMO level of the acceptor material in the composite material layer 708 and the LUMO level of the electron transport layer 704 The LUMO level of the material with high electron transport properties is set to be between the specific energy The energy level of the material with high electron transport properties contained in the electron relay layer 707 is The MO level is set to -5.0 eV or more, preferably -5.0 eV or more and -3.0 eV or less. stomach.

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

[0098] The phthalocyanine-based material contained in the electron relay layer 707 is specifically CuPc, 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] The metal complexes having a metal-oxygen bond and an aromatic ligand contained in the electron relay layer 707 include: It is preferable to use a metal complex having a metal-oxygen double bond. In this case, the molecule has acceptor properties (the ability to easily accept electrons), which facilitates electron transfer (donation and receipt). In addition, metal complexes with metal-oxygen double bonds are thought to be stable. Therefore, by using a metal complex having a metal-oxygen double bond, it is possible to obtain a light-emitting device with low This makes it possible to drive the device more stably with a voltage.

[0100] As a metal complex having a metal-oxygen bond and an aromatic ligand, a phthalocyanine-based material is preferred. Specifically, VOPc (vanadyl phthalocyanine), SnO Pc(Phthalocyanine tin(IV) oxide complex) and TiOPc (Phthalocyanine titanium oxide co complex) is a molecule in which the metal-oxygen double bond acts on other molecules. This is preferred because it is easy to do and has high acceptor properties.

[0101] The above-mentioned phthalocyanine-based material preferably has a phenoxy group. Specifically, a phthalocyanine derivative having a phenoxy group, such as PhO-VOPc, is preferred. The phthalocyanine derivative having a phenoxy group is soluble in a solvent. It has the advantage of being easy to handle when forming a light-emitting element. This has the advantage that maintenance of the device used for film formation becomes easier.

[0102] The electron relay layer 707 may further contain a donor material. Alkali metals, alkaline earth metals, rare earth metals and their compounds (alkali metal compounds) (Oxides such as lithium oxide, halides, carbonates such as lithium carbonate and cesium carbonate (including oxides, halides, and carbonates), or rare earth metal compounds Compounds of metals (including oxides, halides, and carbonates), as well as tetrathianaphthacene (abbreviation: TTN), nickelocene, decamethylnickelocene, and other organic compounds are used. By including these donor materials in the electron relay layer 707, This facilitates movement, and the light-emitting element can be driven at a lower voltage.

[0103] When the electron-relay layer 707 contains a donor substance, the above-mentioned In addition to the material, the acceptor level of the acceptor substance contained in the composite material layer 708 A substance with a high LUMO level can be used. Specific energy levels are: , and the LUMO level is in the range of -5.0 eV or more, preferably in the range of -5.0 eV or more and -3.0 eV or less. It is preferable to use a substance having a structure such as a perylene derivative. Nitrogen-containing condensed aromatic compounds are examples of such compounds. Therefore, it is a preferable material to be used for forming the electron relay layer 707. do.

[0104] Specific examples of perylene derivatives include 3,4,9,10-perylenetetracarboxylic dianhydride. (abbreviation: PTCDA), 3,4,9,10-perylenetetracarboxylic bisbenzyl Zoimidazole (abbreviation: PTCBI), N,N'-dioctyl-3,4,9,10-periodic Phenylenetetracarboxylic diimide (abbreviation: PTCDI-CH), N,N'-dihexyl- 3,4,9,10-perylenetetracarboxylic diimide (abbreviation: Hex PTC) It can be obtained.

[0105] Specific examples of nitrogen-containing condensed aromatic compounds include pyrazino[2,3-f][1,10] Phenanthroline-2,3-dicarbonitrile (PPDN), 2,3,6,7,1 0,11-Hexacyano-1,4,5,8,9,12-hexaazatriphenylene (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 :F2PYPR) etc.

[0106] Other examples include 7,7,8,8-tetracyanoquinodimethane (TCNQ), 1,4, 5,8-Naphthalenetetracarboxylic dianhydride (abbreviation: NTCDA), Perfluorinated phthalocyanine, 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-pentadecafluoro (N-octyl)-1,4,5,8-naphthalenetetracarboxylic acid diimide (abbreviation: NTCD I-C8F), 3',4'-dibutyl-5,5''-bis(dicyanomethylene)-5,5 ''-Dihydro-2,2':5',2''-terthiophene) (abbreviation: DCMT), meta fullerenes (e.g., [6,6]-phenyl C 61 Butyric acid methyl ester) This can be done.

[0107] When the electron-relay layer 707 contains a donor substance, the electron-relay layer 707 contains a substance with high electron transporting properties and a donor substance. The electron relay layer 707 may be formed by a method such as co-evaporation with an insulating material.

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

[0109] In this manner, the EL layer 102 of this embodiment can be manufactured.

[0110] The light-emitting element described above emits light due to a potential difference generated between the first electrode 103 and the second electrode 108. A current flows, and holes and electrons recombine in the EL layer 102, causing light to be emitted. This light emission is emitted by either the first electrode 103 or the second electrode 108 or both. Therefore, the current is taken out to the outside through either the first electrode 103 or the second electrode 108. One or both of the electrodes are transparent to visible light.

[0111] The structure of the layer provided between the first electrode 103 and the second electrode 108 is the same as that described above. In order to prevent quenching caused by the proximity of the light emitting region to the metal, A light-emitting region where holes and electrons recombine is formed at a location away from the first electrode 103 and the second electrode 108. Any other configuration may be used as long as it provides a region.

[0112] That is, the layer stack structure is not particularly limited, and a material having a high electron transporting property, a material having a high hole transporting property, High electron injection material, high hole injection material, bipolar material (electron and A layer made of a material with high hole transportability or a hole blocking material can be freely combined with the light-emitting layer. It can be configured by combining them.

[0113] A passive matrix light-emitting device or a transistor light-emitting device can be manufactured by using the light-emitting element described in this embodiment mode. An active matrix light-emitting device is manufactured in which the driving of the light-emitting element is controlled by a The light-emitting device can be applied to electronic devices, lighting devices, and the like.

[0114] In the above manner, a light-emitting element of one embodiment of the present invention can be manufactured.

[0115] This embodiment mode can be combined with other embodiment modes as appropriate. [Example]

[0116] In this example, guest materials and host materials that can be used in a light-emitting element of one embodiment of the present invention are The material will be explained using FIG. 1 and FIG.

[0117] The guest material used in this example is (acetylacetonato)bis(4,6-diphenylpyridine). Iridium(III) (abbreviation: [Ir(dppm)2(acac)]), bis(dithiocarbamate) (3,5-dimethyl-2-phenylpyrazinato)(dipivaloylmethanato)iridium( III) (abbreviation: [Ir(mppr-Me)2(dpm)]), and (acetylacetonate Iridium(III)bis(6-methyl-4-phenylpyrimidinato)iridium(III) The host materials used in this example are: is 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxazone Sarin (abbreviation: 2mDBTPDBq-II) and 4-phenyl-4'-(9-phenyl- Mixture of 9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP) 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> Figure 1(A) and Figure 16 show the ultraviolet spectra of [Ir(dppm)2(acac)] in dichloromethane solution. The visible absorption spectrum (hereinafter referred to as the absorption spectrum) is shown as absorption spectrum 1. Similarly, the absorption spectrum 2 is the absorption spectrum of [Ir(mppr-Me)2(dpm)]. The absorption spectrum of [Ir(mppm)2(acac)] is shown as absorption spectrum 3. Indicates the rule.

[0120] Each absorption spectrum was measured using a UV-visible spectrophotometer (JASCO V55) A dichloromethane solution was placed in a quartz cell and measurements were taken at room temperature.

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

[0122] From Figure 1(A) and Figure 16, absorption spectra 1 to 3 overlap with the emission spectrum. Therefore, it was found that any one of the guest materials used in this example and this The light-emitting device using the host material of the example in the light-emitting layer has an emission spectrum similar to that of the host material. Energy transfer occurs by utilizing the overlap of the absorption spectra of the guest material. This suggests that the transfer efficiency is high.

[0123] Here, in Fig. 1(A) and Fig. 16, the longest wavelength (lowest energy) side of the absorption spectrum The peak of the absorption band (which is thought to contribute strongly to the emission) and the peak of the emission spectrum Among the peaks in absorption spectrum 1 to 3, the peaks that are closest to the peaks in the emission spectrum are The absorption spectrum 1 peak is located close to the emission spectrum peak. There is a peak in the absorption spectrum 3.

[0124] Specifically, in FIG. 16, the peak of the absorption spectrum 1 and the peak of the 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 0.12 eV, and the difference between the peak of absorption spectrum 3 and the peak of emission spectrum is 0. It was 23 eV.

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

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

[0127] From the above, it can be seen that the overlap between the absorption spectrum 1 and the emission spectrum is particularly large. The mixed material of 2mDBTPDBq-II and PCBA1BP was used as the host material, [Ir(d The light-emitting device using the guest material [(ppm)2(acac)] has a luminescence spectrum of the mixed material. By utilizing the overlap of the absorption spectrum between [Ir(dppm)2(acac)] and [Ir(dppm)2(acac)], This suggests that the energy transfer efficiency is particularly high because of the energy transfer.

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

[0129] The absorption of [Ir(dppm)2(acac)] and [Ir(mppr-Me)2(dpm)] To obtain the absorption spectrum, the most stable structure of each molecule in its ground state is used. The excitation energy and oscillator strength were calculated. Then, based on the calculated oscillator strength, the absorption spectra were calculated. The specific calculation method is described below.

[0130] Using density functional theory (DFT), [Ir(dppm)2(acac)] and [Ir(m We calculated the most stable structure of the ground state of [(dpm-ppr-Me)2(dpm)]. Using the time-dependent density functional (TD-DFT), [Ir(dppm)2(acac)] and [ Ir(mppr-Me)2(dpm)], and the excitation energy and oscillator strength were calculated. The absorption spectrum was calculated from the total energy of the DFT. The interaction energy includes the interatomic electrostatic energy, the electron kinetic energy, and the complex electron-electron interactions. In DFT, the exchange-correlation interaction is expressed as the electron density. The calculation is highly accurate because it is approximated by a functional (a function of a function) of the single-electron potential. Here, we use the mixed functional B3PW91 to calculate the exchange and correlation energy. The weight of each parameter was specified. In addition, LanL2DZ was used as the basis function for the Ir atom, 6-311 (triple split using three contraction functions for each valence orbital) The basis functions of the valence basis set were applied to atoms other than Ir. For example, for a hydrogen atom, the 1s to 3s orbitals are considered, and for a carbon atom, The orbitals 1s to 4s and 2p to 4p are taken into account. Furthermore, to improve the accuracy of the calculation, As a polarization basis set, p-functions were added to hydrogen atoms and d-functions to atoms other than hydrogen atoms.

[0131] The quantum chemistry calculation program used was Gaussian 09. The analysis was carried out using a high-performance computer (SGI, Altix4700).

[0132] Figure 1(B) shows the absorption spectrum obtained by calculation. The absorption spectrum obtained from the measurement is shown below. Specifically, [Ir(dppm)2(acac The absorption spectrum obtained from the measurement of The absorption spectrum obtained is shown as Absorption Spectrum 1'. The absorption spectrum obtained from the measurement of [2(dpm)] is shown as absorption spectrum 2. The absorption spectrum obtained from the calculation is shown as absorption spectrum 2'. The horizontal axis indicates the wavelength (nm), and the vertical axis indicates the molar extinction coefficient ε (M -1 ·cm -1 ) and luminous intensity Indicates degrees (arbitrary unit).

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

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

[0135] [ka]

[0136] A method for fabricating the light-emitting elements 1 to 3 of this example will be described below.

[0137] (Light-emitting element 1) First, indium tin oxide containing silicon oxide (ITSO) is deposited on a glass substrate 1100. The first electrode 1101, which functions as an anode, was formed by a quartz crystal deposition method. The film thickness was set to 110 nm, and the electrode area was set to 2 mm x 2 mm.

[0138] Next, as a pretreatment for forming a light emitting element 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 The substrate is placed in a vacuum deposition apparatus whose inside pressure has been reduced to about 100 Pa. After vacuum baking at 170° C. for 30 minutes in the heating chamber of the device, the substrate 1100 was It was left to cool for about 0 minutes.

[0140] Next, the surface on which the first electrode 1101 is formed is placed downward. The substrate 1100 thus formed is fixed to a substrate holder provided in a vacuum deposition apparatus, and 10 -4 P After the pressure was reduced to about a, 4-phenyl-4'-(9-phenyl fluoren-9-yl)triphenylamine (abbreviation: BPAFLP) and molybdenum oxide ( VI) was co-evaporated to form a hole injection layer 1111. The thickness of the layer was set to 40 nm. The weight ratio of BPAFLP to molybdenum oxide was 4:2 (=BPAFLP:molybdenum oxide). The concentration was adjusted to be 100%.

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

[0142] Furthermore, 2mDBTPDBq-II, PCBA1BP, and [Ir(dppm)2(ac ac)] was co-evaporated to form a light-emitting layer 1113 on the hole transport layer 1112. Weight of DBTPDBq-II, PCBA1BP, and [Ir(dppm)2(acac)] The ratio was 0.8:0.2:0.05 (=2mDBTPDBq-II:PCBA1BP:[I r(dppm)2(acac)]). was set to 40 nm.

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

[0144] Next, bathophenanthroline (abbreviation: BPhen) was applied to the first electron transport layer 1114a. A film was formed to a thickness of 20 nm to form the second electron transport layer 1114b.

[0145] Furthermore, lithium fluoride (LiF) was deposited on the second electron transport layer 1114b to a thickness of 1 nm. An electron injection layer 1115 was formed by evaporation.

[0146] Finally, a 200 nm film of aluminum was deposited as the second electrode 1103, which served as the cathode. The light-emitting element 1 of this example was fabricated by vapor deposition so as to have a thickness of 1000 nm.

[0147] (Light-emitting element 2) The light-emitting layer 1113 of the light-emitting element 2 was made of 2mDBTPDBq-II, PCBA1BP, and [I The film was formed by co-evaporation of 2mDBT. Weights of PDBq-II, PCBA1BP, and [Ir(mppr-Me)2(dpm)] The ratio was 0.8:0.2:0.05 (=2mDBTPDBq-II:PCBA1BP:[I r(mppr-Me)2(dpm)]). The film thickness was 40 nm. Except for the light-emitting layer 1113, the light-emitting element was fabricated in the same manner as in the light-emitting element 1.

[0148] (Light-emitting element 3) The light-emitting layer 1113 of the light-emitting element 3 was made of 2mDBTPDBq-II, PCBA1BP, and [I r(mppm)2(acac)] was co-evaporated. The weight ratio of Bq-II, PCBA1BP, and [Ir(mppm)2(acac)] was 0. 8:0.2:0.05(=2mDBTPDBq-II:PCBA1BP:[Ir(mpp The thickness of the light-emitting layer 1113 was adjusted to 40 nm. The other components than the light-emitting layer 1113 were fabricated in the same manner as in the light-emitting element 1.

[0149] In the above-described deposition process, the deposition was all carried out by resistance heating.

[0150] The element structures of the thus obtained Light-Emitting Elements 1 to 3 are shown in Table 1.

[0151] [Table 1]

[0152] These light emitting devices were placed in a glove box with a nitrogen atmosphere, and the light emitting devices were exposed to the atmosphere. After sealing the device to prevent leakage, the operating characteristics of the light-emitting device were measured. The measurements were carried out at room temperature (atmosphere maintained at 25°C).

[0153] FIG. 3 shows the current density-luminance characteristics of Light-emitting Elements 1 to 3. In FIG. 3, the horizontal axis represents the current density. Flow density (mA / cm 2 ) and the vertical axis is luminance (cd / m 2 ) and the voltage-luminance characteristics are This is shown in Figure 4. In Figure 4, the horizontal axis represents voltage (V) and the vertical axis represents brightness (cd / m 2 ) is represented. The luminance-current efficiency characteristics are shown in Figure 5. In Figure 5, the horizontal axis represents luminance (cd / m 2 ) vertically The axis represents the current efficiency (cd / A). The luminance vs. external quantum efficiency characteristics are shown in Figure 6. In this case, the horizontal axis is luminance (cd / m 2 ) and the vertical axis indicates the external quantum efficiency (%).

[0154] Furthermore, the luminance of light-emitting element 1 to light-emitting element 3 was 1000 cd / m 2 Voltage when near ), current density (mA / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), power Table 2 shows the power efficiency (lm / W) and external quantum efficiency (%).

[0155] [Table 2]

[0156] Furthermore, the emission spectra when a current of 0.1 mA was applied to the light-emitting elements 1 to 3 are shown in FIG. 7. In FIG. 7, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit). As shown in Table 2, 2 The CIE chromaticity coordinates of light-emitting element 1 at a luminance of (x ,y)=(0.56,0.44), and 1000 cd / m 2 When the brightness of light-emitting element 2 is The CIE chromaticity coordinates are (x,y)=(0.55,0.45), which is 940 cd / m 2 Brightness of At this time, the CIE chromaticity coordinates of the light-emitting element 3 were (x, y) = (0.44, 0.55). From these results, it was found that the light-emitting element 1 emitted light originating from [Ir(dppm)2(acac)]. As a result, light emission from the light-emitting element 2 originated from [Ir(mppr-Me)2(dpm)]. It was found that light emission from the light-emitting element 3 originated from [Ir(mppm)2(acac)]. It was.

[0157] As can be seen from Table 2 and FIGS. 3 to 6, the light-emitting elements 1 to 3 have high current efficiency, high power consumption, and low power consumption. The photon efficiency and external quantum efficiency were both high.

[0158] In the light-emitting element of this example, the host material and guest material shown in Example 1 were used in the light-emitting layer. From Example 1, the absorption spectra of the guest materials used in the light-emitting elements 1 to 3 were The light-emitting element of this example has an overlapping emission spectrum with that of the host material. Since energy is transferred using this, the energy transfer efficiency is high and the external quantum efficiency is high. It is thought that this is the case.

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

[0160] Furthermore, the light-emitting element 2 exhibited a higher external quantum efficiency than the light-emitting element 3. The results show that the peak wavelength of absorption spectrum 2 is closer to the peak wavelength of absorption spectrum 3. This was close to the peak wavelength of the optical spectrum. This suggests that there is a difference in the external quantum efficiency characteristics.

[0161] From the above results, it can be seen that by applying one embodiment of the present invention, a device with high external quantum efficiency can be realized. It was shown that

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

[0163] Reliability test is performed with an initial brightness of 5000 cd / m 2 The light emitting element was set at a constant current density. Light-emitting elements 1 to 3 were driven.

[0164] The luminance of the light-emitting element 1 after 470 hours was 85% of the initial luminance. The luminance of light-emitting element 2 after 470 hours was 72% of the initial luminance. The luminance after 80 hours was 72% of the initial luminance.

[0165] From the above results, it can be seen that an element having a long lifetime can be realized by applying one embodiment of the present invention. was shown. [Example]

[0166] In this example, a light-emitting element of one embodiment of the present invention will be described with reference to FIG. The materials used are the same as those used in the previous examples, and therefore the chemical formulas are omitted.

[0167] The method for fabricating the light-emitting device 4 of this example will be described below.

[0168] (Light-emitting element 4) First, a film of ITSO was formed on a glass substrate 1100 by sputtering, and the film served as an anode. The first electrode 1101 was formed to a thickness of 110 nm and an area of ​​2 mm x 2 mm.

[0169] Next, as a pretreatment for forming a light emitting element 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 The substrate is placed in a vacuum deposition apparatus whose inside pressure has been reduced to about 100 Pa. After vacuum baking at 170° C. for 30 minutes in the heating chamber of the device, the substrate 1100 was It was left to cool for about 0 minutes.

[0171] Next, the surface on which the first electrode 1101 is formed is placed downward. The substrate 1100 thus formed is fixed to a substrate holder provided in a vacuum deposition apparatus, and 10 -4 P After the pressure was reduced to about 1000 kJ / cm, BPAFLP and molybdenum oxide (VI ) was co-evaporated to form a hole injection layer 1111. The thickness of the layer was set to 40 nm. The weight ratio of PAFLP to molybdenum oxide was 4:2 (=BPAFLP:molybdenum oxide). The value was adjusted to be 0.

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

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

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

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

[0176] Furthermore, LiF was evaporated onto the second electron transport layer 1114b to a thickness of 1 nm to form an electron injection layer. 1115 was formed.

[0177] Finally, a 200 nm film of aluminum was deposited as the second electrode 1103, which served as the cathode. The light-emitting element 4 of this example was fabricated by vapor deposition so as to have a thickness of 1000 nm.

[0178] In the above-described deposition process, the deposition was all carried out by resistance heating.

[0179] The element structure of the light-emitting element 4 obtained as described above is shown in Table 3.

[0180] [Table 3]

[0181] The light emitting element 4 is placed in a glove box with a nitrogen atmosphere so that the light emitting element is not exposed to the atmosphere. After the sealing work was performed as described above, the operating characteristics of the light-emitting element were measured. was carried out at room temperature (atmosphere maintained at 25°C).

[0182] FIG. 9 shows the current density-luminance characteristics of the light-emitting element 4. In FIG. 9, the horizontal axis represents the current density (mA / cm 2 ) and the vertical axis is luminance (cd / m 2 ) and the voltage-luminance characteristics are shown in Figure 10. In Figure 10, the horizontal axis represents voltage (V) and the vertical axis represents brightness (cd / m 2 ) and luminance - The current efficiency characteristics are shown in Figure 11. In Figure 11, the horizontal axis represents luminance (cd / m2 ) and the vertical axis is the voltage The luminance vs. external quantum efficiency characteristics are shown in Figure 12. The horizontal axis is luminance (cd / m 2 ) and the vertical axis indicates the external quantum efficiency (%).

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

[0184] [Table 4]

[0185] FIG. 13 shows the emission spectrum when a current of 0.1 mA is applied to the light-emitting element 4. In Table 13, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary units). As shown, 1100cd / m 2 The CIE chromaticity coordinates of light-emitting element 4 at a luminance of (x, y) = (0.57, 0.43). From this result, it can be seen that the light-emitting element 4 has an It was found that orange luminescence originating from (acac)] was obtained.

[0186] As can be seen from Table 4 and FIGS. 9 to 12, the light-emitting element 4 exhibited excellent current efficiency, power efficiency, and external The quantum efficiency was high, especially at 1100 cd / m 2 External quantum efficiency at a luminance of As mentioned above, the external quantum efficiency is limited to about 25%. However, the results of this study are even higher than that.

[0187] In the light-emitting element of this example, the host material and guest material shown in Example 1 were used in the light-emitting layer. From Example 1, it can be seen that the absorption spectrum of the guest material used in the light-emitting element 4 is larger than that of the host material. The light emitting element of this embodiment utilizes this overlap to transfer energy. This is thought to result in high energy transfer efficiency and high external quantum efficiency.

[0188] In addition, in the results of Example 1, the longest wavelength of the absorption spectrum of the guest material used in the light-emitting element 4 In the long absorption band, the peak wavelength is close to the peak wavelength of the emission spectrum (the difference between the peaks is 0.02 eV), and the molar extinction coefficient at the peak wavelength was large (>5000 M -1 ·c m -1 ) From these results, it can be seen that the energy transfer efficiency of the light-emitting element 4 is particularly high, and therefore the external quantum efficiency It is thought that this showed an unprecedentedly high value.

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

[0190] Next, a reliability test was conducted on the light-emitting element 4. The results of the reliability test are shown in FIG. The vertical axis shows the normalized brightness (%) when the initial brightness is 100%, and the horizontal axis shows the driving time of the element. Indicates time (h).

[0191] Reliability test is performed with an initial brightness of 5000 cd / m 2 The light emitting element was set at a constant current density. Driven 4.

[0192] After 170 hours, the luminance of the light-emitting element 4 remained at 95% of the initial luminance.

[0193] From the above results, it can be seen that a highly reliable element can be realized by applying one embodiment of the present invention. was shown. [Example]

[0194] In this example, guest materials and host materials that can be applied to a light-emitting element of one embodiment of the present invention were An example of the material will be described with reference to FIG.

[0195] The guest material used in this example is [Ir(dppm)2(acac)]. The host material used in the examples is 2mDBTPDBq-II and 4,4'-bis[N-(1 It is a mixed material with N-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 examples are Omitted.

[0196] [ka]

[0197] <Absorption spectrum> Figure 17(A)(B) shows the ultraviolet spectra of [Ir(dppm)2(acac)] in dichloromethane solution. The visible absorption spectrum (absorption spectrum a) is shown. Using a spectrophotometer (JASCO Corporation, V550 model), a dichloromethane solution (0.093 The HCl solution (mmol / L) was placed in a quartz cell and measurements were carried out at room temperature.

[0198] <Emission spectrum> In addition, Figure 17(A)(B) shows the development of a thin film of the mixed material of 2mDBTPDBq-II and NPB. The horizontal axis in FIG. 17(A) represents the wavelength (nm) of the light emitted from the sample. ), and the vertical axis represents the molar extinction coefficient ε (M -1 ·cm-1 ) and luminescence intensity (arbitrary unit) In Figure 17(B), the horizontal axis represents energy (eV) and the vertical axis represents the molar absorption coefficient. ε(M -1 ·cm -1 ) and luminescence intensity (arbitrary units).

[0199] From the absorption spectrum a in FIG. 17(A), [Ir(dppm)2(acac)] is It can be seen that the fluorine-containing compound has a broad absorption band around 100 nm. This absorption band strongly contributes to the emission of light. It is thought to be an absorption band.

[0200] The peak in the emission spectrum a is thought to strongly contribute to the emission in the absorption spectrum a. Specifically, the absorption band in the absorption spectrum a is The difference between the absorption peak (515 nm) and the peak of the emission spectrum a was 0.09 eV. Therefore, the light-emitting element in which both the guest material and the host material used in this example are used in the light-emitting layer is The overlap between the emission spectrum of the host material and the absorption spectrum of the guest material is utilized to generate This suggests that the energy transfer efficiency is high. It was suggested that a light-emitting device with high quantum efficiency could be obtained. [Example]

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

[0202] [ka]

[0203] A method for fabricating the light-emitting device 5 of this example will be described below.

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

[0205] Next, as a pretreatment for forming a light emitting element 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.

[0206] Then, 10 -4 The substrate is placed in a vacuum deposition apparatus whose inside pressure has been reduced to about 100 Pa. After vacuum baking at 170° C. for 30 minutes in the heating chamber of the device, the substrate 1100 was It was left to cool for about 0 minutes.

[0207] Next, the surface on which the first electrode 1101 is formed is placed downward. The substrate 1100 thus formed is fixed to a substrate holder provided in a vacuum deposition apparatus, and 10 -4 P After the pressure was reduced to about 1000 kJ / cm, 4,4',4''-(1,3,5-benzyl alcohol) was added to the first electrode 1101. DBT3P-II) and molybdenum oxide The hole injection layer 1111 was formed by co-evaporation of ZnO and Zn(VI). The weight ratio of DBT3P-II to molybdenum oxide was 4:2 (=DBT3P- II: molybdenum oxide).

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

[0209] Furthermore, 2mDBTPDBq-II, NPB, and [Ir(dppm)2(acac)] were co-evaporated to form a light-emitting layer 1113 on the hole transport layer 1112. The weight ratio of DBq-II, NPB, and [Ir(dppm)2(acac)] was 0.8:0 .2:0.05(=2mDBTPDBq-II:NPB:[Ir(dppm)2(aca The thickness of the light-emitting layer 1113 was adjusted to 40 nm.

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

[0211] Next, a film of BPhen was formed on the first electron transport layer 1114a to a thickness of 20 nm. Then, a second electron transport layer 1114b was formed.

[0212] Furthermore, LiF was evaporated onto the second electron transport layer 1114b to a thickness of 1 nm to form an electron injection layer. 1115 was formed.

[0213] Finally, a 200 nm film of aluminum was deposited as the second electrode 1103, which served as the cathode. The light-emitting element 5 of this example was fabricated by vapor deposition so as to have a thickness of 1000 nm.

[0214] In the above-described deposition process, the deposition was all carried out by resistance heating.

[0215] The element structure of the light-emitting element 5 obtained as described above is shown in Table 5.

[0216] [Table 5]

[0217] The light emitting element 5 is placed in a glove box with a nitrogen atmosphere so that the light emitting element is not exposed to the atmosphere. After the sealing work was performed as described above, the operating characteristics of the light-emitting element were measured. was carried out at room temperature (atmosphere maintained at 25°C).

[0218] The current density-luminance characteristics of the light-emitting element 5 are shown in FIG. 18. In FIG. 18, the horizontal axis represents the current density (m A / cm 2 ) and the vertical axis is luminance (cd / m 2 ) and the voltage-luminance characteristics are shown in Figure 19. In Figure 19, the horizontal axis represents voltage (V) and the vertical axis represents luminance (cd / m 2 ) and also represents The luminance-current efficiency characteristics are shown in Figure 20. In Figure 20, the horizontal axis represents luminance (cd / m 2 ) on the vertical axis represents the current efficiency (cd / A). The luminance vs. external quantum efficiency characteristics are shown in Figure 21. In this example, the horizontal axis represents luminance (cd / m 2 ) and the vertical axis indicates the external quantum efficiency (%).

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

[0220] [Table 6]

[0221] FIG. 22 shows the emission spectrum when a current of 0.1 mA is applied to the light-emitting element 5. In 22, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit). As shown, 1100cd / m 2The CIE chromaticity coordinates of light-emitting element 5 at a luminance of (x, y) = (0.57, 0.43). From this result, it can be seen that the light-emitting element 5 has an It was found that orange luminescence originating from (acac)] was obtained.

[0222] As can be seen from Table 6 and FIGS. 18 to 21, the light-emitting element 5 has excellent current efficiency, power efficiency, and external The partial quantum efficiency was high.

[0223] The light-emitting device 5 was fabricated using 2mDBTPDBq-II, NPB, and [Ir(dpp m)2(acac)] was used in the light-emitting layer. The emission spectrum of the PB mixture is similar to the absorption spectrum of [Ir(dppm)2(acac)]. The overlap with the absorption band that is thought to strongly contribute to light emission in the EL element is large. Since energy transfer is performed using this overlap, the energy transfer efficiency is high and the external quantum It is considered to be highly efficient.

[0224] In addition, in the results of Example 4, the longest wavelength of the absorption spectrum of the guest material used in the light-emitting element 5 In the absorption band on the long side, the peak is close to the peak of the emission spectrum of the host material, and The molar extinction coefficient of the compound was large (>5000 M -1 ·cm -1 ) From these, luminescent elements The energy transfer efficiency of molecule 5 is particularly high, and the external quantum efficiency is higher than ever before. It is thought that...

[0225] From the above results, it can be seen that by applying one embodiment of the present invention, a device with high external quantum efficiency can be realized. It was shown that [Example]

[0226] In this example, guest materials and host materials that can be used in a light-emitting element of one embodiment of the present invention are described. An example of the material will be described with reference to FIG.

[0227] The guest material used in this example is bis(2,3,5-triphenylpyrazinato)(dipivacaine). Iridium(III) (Ir(tppr)2(dpm)) The host material used in this example is a mixture of 2mDBTPDBq-II and NPB. The chemical formula of the material used in this example is shown below. The chemical formula of the material is omitted.

[0228] [ka]

[0229] <Absorption spectrum> Figure 23(A)(B) shows the ultraviolet spectra of a dichloromethane solution of [Ir(tppr)2(dpm)]. The visible absorption spectrum (absorption spectrum b) is shown. Using a spectrophotometer (JASCO Corporation, Model V550), a dichloromethane solution (0.094 m mol / L) was placed in a quartz cell and measurements were carried out at room temperature.

[0230] <Emission spectrum> In addition, Figure 23(A)(B) shows the development of a thin film of the mixed material of 2mDBTPDBq-II and NPB. The horizontal axis in FIG. 23(A) represents the wavelength (nm) of the light emitted from the sample. ), and the vertical axis represents the molar extinction coefficient ε (M -1 ·cm -1 ) and luminescence intensity (arbitrary unit) In Figure 23(B), the horizontal axis represents energy (eV) and the vertical axis represents the molar absorption coefficient. ε(M -1 ·cm-1 ) and luminescence intensity (arbitrary units).

[0231] From the absorption spectrum b of Figure 23(A), [Ir(tppr)2(dpm)] is It can be seen that there is a broad absorption band near m. This absorption band is the absorption band that strongly contributes to the emission. It is thought to be a convergence.

[0232] The peak in the emission spectrum b is thought to strongly contribute to the emission in the absorption spectrum b. Specifically, the absorption band in the absorption spectrum b overlaps with that in the absorption spectrum c. The difference between the absorption peak (shoulder peak around 530 nm) and the peak of the emission spectrum b is Therefore, both the guest material and the host material used in this example emit light. The light-emitting element used in the layer has a characteristic that the emission spectrum of the host material and the absorption spectrum of the guest material are different. It is suggested that the energy transfer efficiency is high because the energy transfer is carried out by utilizing the overlap. This suggests that a light-emitting device with high external quantum efficiency can be obtained. [Example]

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

[0234] The method for fabricating the light emitting device 6 of this example will be described below.

[0235] (Light emitting element 6) The light-emitting layer 1113 of the light-emitting element 6 is made of 2mDBTPDBq-II, NPB, and [Ir(tpp r)2(dpm)] was co-evaporated. The weight ratio of NPB and [Ir(tppr)2(dpm)] was 0.8:0.2:0.05 ( =2mDBTPDBq-II:NPB:[Ir(tppr)2(dpm)]) The thickness of the light-emitting layer 1113 was adjusted to 40 nm. The light-emitting device was fabricated in the same manner as in Example 5.

[0236] The element structure of the light-emitting element 6 obtained as described above is shown in Table 7.

[0237] [Table 7]

[0238] The light emitting element 6 is placed in a glove box with a nitrogen atmosphere so that the light emitting element is not exposed to the atmosphere. After the sealing work was performed as described above, the operating characteristics of the light-emitting element were measured. was carried out at room temperature (atmosphere maintained at 25°C).

[0239] The current density-luminance characteristics of the light-emitting element 6 are shown in FIG. 24. In FIG. 24, the horizontal axis represents the current density (m A / cm 2 ) and the vertical axis is luminance (cd / m 2 ) and the voltage-luminance characteristics are shown in Figure 25. In Figure 25, the horizontal axis represents voltage (V) and the vertical axis represents luminance (cd / m 2 ) and also represents The luminance-current efficiency characteristics are shown in Figure 26. In Figure 26, the horizontal axis represents luminance (cd / m 2 ) on the vertical axis represents the current efficiency (cd / A). The luminance vs. external quantum efficiency characteristics are shown in Figure 27. In this example, the horizontal axis represents luminance (cd / m 2 ) and the vertical axis indicates the external quantum efficiency (%).

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

[0241] [Table 8]

[0242] FIG. 28 shows the emission spectrum when a current of 0.1 mA is applied to the light-emitting element 6. In 28, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary units). As shown, 1100cd / m 2 The CIE chromaticity coordinates of light-emitting element 6 at a luminance of (x,y) = (0.66, 0.34). From this result, it can be seen that the light-emitting element 6 has an (dpm)] was obtained.

[0243] As can be seen from Table 8 and FIGS. 24 to 27, the light-emitting element 6 has excellent current efficiency, power efficiency, and external The partial quantum efficiency was high.

[0244] In the light-emitting device 6, 2mDBTPDBq-II, NPB, and [Ir(tp pr)2(dpm)] was used in the light-emitting layer. The emission spectrum of the PB mixture is similar to the absorption spectrum of [Ir(tppr)2(dpm)]. The light-emitting element 6 has a large overlap with the absorption band that is thought to strongly contribute to light emission in the device. Since energy transfer is performed using this overlap, the energy transfer efficiency is high and the external quantum efficiency is low. The rate is thought to be high.

[0245] From the above results, it can be seen that by applying one embodiment of the present invention, a device with high external quantum efficiency can be realized. It was shown that

[0246] Next, a reliability test was conducted on the light-emitting element 6. The results of the reliability test are shown in FIG. The vertical axis shows the normalized brightness (%) when the initial brightness is 100%, and the horizontal axis shows the driving time of the element. Indicates time (h).

[0247] Reliability test is performed with an initial brightness of 5000 cd / m 2 The light emitting element was set at a constant current density. Driven 6.

[0248] The luminance of the light-emitting element 6 after 98 hours was 87% of the initial luminance. Device 6 was found to be a long-life device.

[0249] From the above results, it can be seen that a highly reliable element can be realized by applying one embodiment of the present invention. was shown. [Example]

[0250] In this example, guest materials and host materials that can be used in a light-emitting element of one embodiment of the present invention are described. An example of the material will be described with reference to FIG.

[0251] The guest material used in this example is [Ir(mppm)2(acac)]. The host material used in the examples is a mixture of 2mDBTPDBq-II and PCBA1BP. and 2mDBTPDBq-II and 4-(1-naphthyl)-4'-phenyltriphenylamine The chemical composition of the materials used in this example is a mixture of αNBA1BP and αNBA1BP. The formula is shown below: Note that the chemical formulas of the materials used in the previous examples are omitted.

[0252] [ka]

[0253] <Absorption spectrum> Figure 30(A)(B) shows the ultraviolet spectra of [Ir(mppm)2(acac)] in dichloromethane solution. The visible absorption spectrum (absorption spectrum c) is shown. Using a spectrophotometer (Nihon Bunko Co., Ltd., Model V550), a dichloromethane solution (0.10 ml mol / L) was placed in a quartz cell and measurements were carried out at room temperature.

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

[0255] From the absorption spectrum c of Figure 30(A), [Ir(mppm)2(acac)] is It can be seen that the fluorine-containing compound has a broad absorption band around 100 nm. This absorption band strongly contributes to the emission of light. It is thought to be an absorption band.

[0256] The peaks of the emission spectrum c-1 and the emission spectrum c-2 are It was found that there is a large overlap with the absorption band that is thought to strongly contribute to the emission. The light-emitting device in which the guest material used in the examples and either of the host materials are used in the light-emitting layer is The overlap between the emission spectrum of the host material and the absorption spectrum of the guest material is utilized to Therefore, it is suggested that the energy transfer efficiency is high. It was suggested that a light-emitting device with high photon efficiency could be obtained.

[0257] Here, the emission spectrum c-2 has a shorter wavelength (higher energy) than the emission spectrum c-1. The peak of the emission spectrum c-2 is on the side of the emission spectrum c-1. Specifically, in the absorption spectrum c, The peak of the absorption band (shoulder peak around 490 nm) and the peak of the emission spectrum c-1 The peak difference is 0.15 eV, and the peak of the absorption band in the absorption spectrum c (490 The difference between the peak of the emission spectrum c-2 and the shoulder peak near 1000 nm is 0.01 eV. It was.

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

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

[0260] The method for fabricating the light-emitting elements 7 and 8 of this example will be described below.

[0261] (Light emitting element 7) First, a film of ITSO was formed on a glass substrate 1100 by sputtering, and the film served as an anode. The first electrode 1101 was formed to a thickness of 110 nm and an area of ​​2 mm x 2 mm.

[0262] Next, as a pretreatment for forming a light emitting element 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 The substrate is placed in a vacuum deposition apparatus whose inside pressure has been reduced to about 100 Pa. After vacuum baking at 170° C. for 30 minutes in the heating chamber of the device, the substrate 1100 was It was left to cool for about 0 minutes.

[0264] Next, the surface on which the first electrode 1101 is formed is placed downward. The substrate 1100 thus formed is fixed to a substrate holder provided in a vacuum deposition apparatus, and 10 -4 P After the pressure was reduced to about 1000 kJ / cm, BPAFLP and molybdenum oxide (VI ) was co-evaporated to form a hole injection layer 1111. The thickness of the layer was set to 40 nm. The weight ratio of PAFLP to molybdenum oxide was 4:2 (=BPAFLP:molybdenum oxide). The value was adjusted to be 0.

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

[0266] Furthermore, 2mDBTPDBq-II, PCBA1BP, and [Ir(mppm)2(ac ac)] was co-evaporated to form a light-emitting layer 1113 on the hole transport layer 1112. Weights of DBTPDBq-II, PCBA1BP, and [Ir(mppm)2(acac)] The ratio was 0.8:0.2:0.05 (=2mDBTPDBq-II:PCBA1BP:[I r(mppm)2(acac)]). was set to 40 nm.

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

[0268] Next, a film of BPhen was formed on the first electron transport layer 1114a to a thickness of 20 nm. Then, a second electron transport layer 1114b was formed.

[0269] Furthermore, LiF was evaporated onto the second electron transport layer 1114b to a thickness of 1 nm to form an electron injection layer. 1115 was formed.

[0270] Finally, a 200 nm film of aluminum was deposited as the second electrode 1103, which served as the cathode. The light-emitting element 7 of this example was fabricated by vapor deposition so as to have a thickness of 1000 nm.

[0271] (Light emitting element 8) The light-emitting layer 1113 of the light-emitting element 8 was made of 2mDBTPDBq-II, αNBA1BP, and [Ir (mppm)2(acac)] was co-evaporated. The weight ratio of q-II, αNBA1BP, and [Ir(mppm)2(acac)] was 0.8 :0.2:0.05(=2mDBTPDBq-II:αNBA1BP:[Ir(mppm The thickness of the light-emitting layer 1113 was adjusted to 40 nm. The fabrication was the same as for the light-emitting element 7 except for the light-emitting layer 1113 .

[0272] In the above-described deposition process, the deposition was all carried out by resistance heating.

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

[0274] [Table 9]

[0275] These light emitting devices were placed in a glove box with a nitrogen atmosphere, and the light emitting devices were exposed to the atmosphere. After sealing the device to prevent leakage, the operating characteristics of the light-emitting device were measured. The measurements were carried out at room temperature (atmosphere maintained at 25°C).

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

[0277] Furthermore, the luminance of the light-emitting element 7 and the light-emitting element 8 is 1000 cd / m 2 Voltage when near ), current density (mA / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), power The power efficiency (lm / W) and external quantum efficiency (%) are shown in Table 10.

[0278] [Table 10]

[0279] Furthermore, the emission spectra when a current of 0.1 mA is applied to the light-emitting elements 7 and 8 are shown in FIG. 35. In FIG. 35, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit). Also, as shown in Table 10, 1100 cd / m 2 CIE chromaticity coordinates of light-emitting element 7 at a luminance of The target is (x,y)=(0.43,0.56), and the brightness is 860cd / m 2 The luminous element at the brightness of The CIE chromaticity coordinates of the color 8 were (x,y) = (0.43,0.56). Light-emitting elements 7 and 8 emit yellow-green light derived from [Ir(mppm)2(acac)]. It turned out that light was obtained.

[0280] As can be seen from Table 10 and FIGS. 31 to 34, the light-emitting elements 7 and 8 had a current efficiency The power efficiency and external quantum efficiency were all high.

[0281] The light-emitting elements 7 and 8 were made of PCBA1BP or αNBA1BP shown in Example 8, 2mDBTPDBq-II and [Ir(mppm)2(acac)] were used for the light-emitting layer. From Example 8, 2mDBTPDBq-II and PCBA1BP or αNBA1BP The emission spectrum of the mixed material is similar to the absorption spectrum of [Ir(mppm)2(acac)]. The overlap with the absorption band that is thought to strongly contribute to the light emission in the light-emitting element 7 and the light-emitting element 8 is large. The optical element 8 transfers energy by utilizing the overlap, and therefore the energy transfer efficiency is high. , the external quantum efficiency is considered to be high.

[0282] From the above results, it can be seen that by applying one embodiment of the present invention, a device with high external quantum efficiency can be realized. It was shown that

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

[0284] Reliability test is performed with an initial brightness of 5000 cd / m 2 The light emitting element was set at a constant current density. The light-emitting element 7 and the light-emitting element 8 were driven.

[0285] The luminance of the light-emitting element 7 after 260 hours was 74% of the initial luminance. The luminance after 260 hours was 75% of the initial luminance. It was found that the optical element 8 was an element with a long life.

[0286] From the above results, it can be seen that a highly reliable element can be realized by applying one embodiment of the present invention. was shown. [Example]

[0287] In this example, guest materials and host materials that can be used in a light-emitting element of one embodiment of the present invention are described. An example of the material will be described with reference to FIG.

[0288] The guest material used in this example is (acetylacetonato)bis(6-tert-butyl- 4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)2( The host material used in this example is 2mDBTPDBq-I The mixture of I and NPB, and 2mDBTPDBq-II and 2,7-bis[N-(4-di phenylaminophenyl)-N-phenylamino]-spiro-9,9'-bifluorene( The chemical formulas of the materials used in this example are as follows: The chemical formulas of the materials used in the previous examples are omitted below.

[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. Using a visible spectrophotometer (JASCO Corporation, Model V550), a dichloromethane solution (0.0 93 mmol / L) was placed in a quartz cell and measurements were carried out at room temperature.

[0291] <Emission spectrum> In addition, Figure 37(A)(B) shows the thin film of the mixed material of 2mDBTPDBq-II and DPA2SF. Emission spectrum of the film (emission spectrum d-1), and 2mDBTPDBq-II and NPB The emission spectrum (emission spectrum d-2) of the thin film of the mixed material is shown in Figure 37(A). In this figure, the horizontal axis represents the wavelength (nm) and the vertical axis represents the molar absorption coefficient ε (M -1 ·cm -1 ) and The horizontal axis in FIG. 37(B) represents the luminescence intensity (arbitrary unit). The vertical axis is the molar extinction coefficient ε (M -1 ·cm -1 ) and luminescence intensity (arbitrary units).

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

[0293] The peaks of the emission spectrum d-1 and the emission spectrum d-2 are It was found that there is a large overlap with the absorption band that is thought to strongly contribute to the emission. The light-emitting device in which the guest material used in the examples and either of the host materials are used in the light-emitting layer is The overlap between the emission spectrum of the host material and the absorption spectrum of the guest material is utilized to Therefore, it is suggested that the energy transfer efficiency is high. It was suggested that a light-emitting device with high photon efficiency could be obtained.

[0294] Here, the emission spectrum d-2 has a shorter wavelength (higher energy) than the emission spectrum d-1. The peak of the emission spectrum d-2 is on the side of the emission spectrum d-1. 37. The emission spectrum that overlaps most with the absorption band that strongly contributes to the emission of absorption spectrum d is Specifically, the corresponding emission spectrum in the absorption spectrum d The difference between the peak of the absorption band and the peak of the emission spectrum d-1 is 0.39 eV. The difference between the peak of this absorption band and the peak of the emission spectrum d-2 at torr d is 0.19 eV. there were.

[0295] The difference in the peaks between emission spectrum d-1 and emission spectrum d-2 is This is thought to be due to the difference in the HOMO level. Specifically, the HOMO level of DPA2SF is The HOMO level of NPB was -5.38 eV (both (These values ​​were calculated by CV measurements.) Compared to DPA2SF, NPB has a lower HOMO level. (deeper), the peak of the emission spectrum d-2 is at a shorter wavelength ( It is thought that the

[0296] From the above, it is clear that the mixed material of 2mDBTPDBq-II and NPB and [Ir(tBup The light-emitting device using both 2mDBTPDBq-II and 2mDBTPDBq-II as the light-emitting layer was The mixed material of [Ir(tBuppm)2(acac)] and [DPA2SF] emits light. Compared with the light-emitting device using the layer, the emission spectrum of the host material and the absorption spectrum of the guest material Energy transfer is performed using a larger overlap with the electrons, resulting in more efficient energy transfer. Therefore, it is possible to obtain a light-emitting device with a higher external quantum efficiency. was suggested. [Example]

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

[0298] The method for fabricating the light-emitting elements 9 and 10 of this example will be described below.

[0299] (Light emitting element 9) First, a film of ITSO was formed on a glass substrate 1100 by sputtering, and the film served as an anode. The first electrode 1101 was formed to a thickness of 110 nm and an area of ​​2 mm x 2 mm.

[0300] Next, as a pretreatment for forming a light emitting element 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 The substrate is placed in a vacuum deposition apparatus whose inside pressure has been reduced to about 100 Pa. After vacuum baking at 170° C. for 30 minutes in the heating chamber of the device, the substrate 1100 was It was left to cool for about 0 minutes.

[0302] Next, the surface on which the first electrode 1101 is formed is placed downward. The substrate 1100 thus formed is fixed to a substrate holder provided in a vacuum deposition apparatus, and 10 -4 P After the pressure was reduced to about a, DBT3P-II and molybdenum oxide ( VI) was co-evaporated to form a hole injection layer 1111. The thickness of the layer was set to 40 nm. The weight ratio of DBT3P-II to molybdenum oxide was 4:2 (=DBT3P-II: The temperature was adjusted to be molybdenum oxide.

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

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

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

[0306] Next, a film of BPhen was formed on the first electron transport layer 1114a to a thickness of 20 nm. Then, a second electron transport layer 1114b was formed.

[0307] Furthermore, LiF was evaporated onto the second electron transport layer 1114b to a thickness of 1 nm to form an electron injection layer. 1115 was formed.

[0308] Finally, a 200 nm film of aluminum was deposited as the second electrode 1103, which served as the cathode. The light-emitting element 9 of this example was fabricated by vapor deposition so as to have a thickness of 1000 nm.

[0309] (Light-emitting element 10) The light-emitting layer 1113 of the light-emitting element 10 contains 2mDBTPDBq-II, NPB, and [Ir(tB uppm)2(acac)]. The weight ratio of I, NPB, and [Ir(tBuppm)2(acac)] was 0.8:0. 2:0.05(=2mDBTPDBq-II:NPB:[Ir(tBuppm)2(ac The thickness of the light-emitting layer 1113 was adjusted to 40 nm. The light-emitting element was fabricated in the same manner as in Light-emitting element 9 except for the layer 1113 .

[0310] In the above-described deposition process, the deposition was all carried out by resistance heating.

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

[0312] [Table 11]

[0313] These light emitting devices were placed in a glove box with a nitrogen atmosphere, and the light emitting devices were exposed to the atmosphere. After sealing the device to prevent leakage, the operating characteristics of the light-emitting device were measured. The measurements were carried out at room temperature (atmosphere maintained at 25°C).

[0314] FIG. 38 shows the current density-luminance characteristics of the light-emitting elements 9 and 10. In FIG. The axis represents the current density (mA / cm 2 ) and the vertical axis is luminance (cd / m 2 ) and voltage-brightness The characteristics are shown in Figure 39. In Figure 39, the horizontal axis represents voltage (V) and the vertical axis represents brightness (cd / m 2 ) The luminance-current efficiency characteristics are shown in Figure 40. In Figure 40, the horizontal axis represents the luminance (cd / m 2 ) and the vertical axis represents the current efficiency (cd / A). The luminance vs. external quantum efficiency characteristics are shown in Figure 4 1. In FIG. 41, the horizontal axis represents luminance (cd / m 2 ) and the vertical axis is the external quantum efficiency (%). Shows.

[0315] Furthermore, the luminance of the light-emitting element 9 and the light-emitting element 10 is 1000 cd / m 2 The voltage when 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 was applied to the light-emitting elements 9 and 10 were This is shown in Figure 42. In Figure 42, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit). Also, as shown in Table 12, 2 The CIE chromaticity coordinates of the light-emitting element 9 at the luminance The target is (x,y)=(0.43,0.56), and the brightness is 820cd / m 2 The luminous element at the brightness of The CIE chromaticity coordinates of the color 10 were (x,y) = (0.42,0.57). The light-emitting elements 9 and 10 are made of a compound derived from [Ir(tBuppm)2(acac)]. It was found that yellow-green light was obtained.

[0318] As can be seen from Table 12 and FIGS. 38 to 41, the light-emitting elements 9 and 10 exhibited a high current efficiency. The efficiency, power efficiency, and external quantum efficiency all showed high values.

[0319] The light-emitting devices 9 and 10 were prepared by mixing DPA2SF or NPB as shown in Example 10 with 2 mD BTPDBq-II and [Ir(tBuppm)2(acac)] were used for the light-emitting layer. From Example 10, the mixed material of 2mDBTPDBq-II and DPA2SF or NPB The emission spectrum of [Ir(tBuppm)2(acac)] is The overlap with the absorption band that is thought to strongly contribute to light emission is large. 10 utilizes this overlap to transfer energy, resulting in high energy transfer efficiency and In particular, the mixed material of 2mDBTPDBq-II and NPB is thought to have a high partial quantum efficiency. The emission spectrum is that of the mixture of 2mDBTPDBq-II and DPA2SF. Therefore, the light-emitting element 10 has a large overlap with the absorption band. Since the energy transfer is performed using the It is considered that the external quantum efficiency is high. In the light-emitting layer, the energy value of the peak of the emission spectrum of the host material and the guest material The difference in energy between the lowest energy absorption band peak in the absorption spectrum is 0. It is clear that it is preferable that the value is within 3 eV.

[0320] From the above results, it can be seen that by applying one embodiment of the present invention, a device with high external quantum efficiency can be realized. It was shown that [Example]

[0321] In this example, guest materials and host materials that can be used in a light-emitting element of one embodiment of the present invention are described. An example of the material will be described with reference to FIG.

[0322] The guest material used in this example is [Ir(mppr-Me)2(dpm)]. The host material used in this example is 2mDBTPDBq-II and 4,4',4''-trimethylsilyl. 1'-Triphenylamine (abbreviated as 1'-T NATA), and 2-[4-(dibenzothiophen-4-yl)phenyl] -1-phenyl-1H-benzimidazole (abbreviation: DBTBIm-II) and 1'-TN The chemical formulas of the materials used in this example are shown below. The chemical formulas of the materials used in the previous examples 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. Using a visible spectrophotometer (JASCO Corporation, Model V550), a dichloromethane solution (0.0 93 mmol / L) was placed in a quartz cell and measurements were carried out at room temperature.

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

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

[0327] The peaks of the emission spectrum e-1 and the emission spectrum e-2 are It was found that there is a large overlap with the absorption band that is thought to strongly contribute to the emission. The light-emitting device in which the guest material used in the examples and either of the host materials are used in the light-emitting layer is The overlap between the emission spectrum of the host material and the absorption spectrum of the guest material is utilized to Therefore, it is suggested that the energy transfer efficiency is high. It was suggested that a light-emitting device with high photon efficiency could be obtained.

[0328] Here, the emission spectrum e-2 has a shorter wavelength (higher energy) than the emission spectrum e-1. The peak of the emission spectrum e-2 is on the side of the emission spectrum e-1. It is located closer to the absorption band than the peak of The emission spectrum that overlaps most with the absorption band that strongly contributes to the emission of absorption spectrum e is Specifically, the absorption spectrum e was found to be Absorption band peak (shoulder peak around 520 nm) and peak of emission spectrum e-1 The difference between the peaks of the absorption bands in the absorption spectrum e (520 nm and The difference between the peak of the emission spectrum e-2 and the peak of the near shoulder peak was 0.01 eV.

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

[0330] From the above, the mixed material of DBTBIm-II and 1'-TNATA and [Ir(mp The light-emitting device using 2mDBTPDBq-II and 1'-T The light-emitting device using the mixed material of NATA and [Ir(mppr-Me)2(dpm)] Compared to the conventional method, there is a greater overlap between the emission spectrum of the mixed material and the absorption spectrum of the phosphorescent compound. This suggests that the energy transfer efficiency is higher because the energy transfer is performed using the This suggests that a light-emitting device with higher external quantum efficiency can be obtained. [Example]

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

[0332] The method for fabricating the light-emitting elements 11 and 12 of this example will be described below.

[0333] (Light emitting element 11) First, a film of ITSO was formed on a glass substrate 1100 by sputtering, and the film served as an anode. The first electrode 1101 was formed to a thickness of 110 nm and an area of ​​2 mm x 2 mm.

[0334] Next, as a pretreatment for forming a light emitting element 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 The substrate is placed in a vacuum deposition apparatus whose inside pressure has been reduced to about 100 Pa. After vacuum baking at 170° C. for 30 minutes in the heating chamber of the device, the substrate 1100 was It was left to cool for about 0 minutes.

[0336] Next, the surface on which the first electrode 1101 is formed is placed downward. The substrate 1100 thus formed is fixed to a substrate holder provided in a vacuum deposition apparatus, and 10 -4 P After the pressure was reduced to about 1000 kJ / cm, BPAFLP and molybdenum oxide (VI ) was co-evaporated to form a hole injection layer 1111. The thickness of the layer was set to 40 nm. The weight ratio of PAFLP to molybdenum oxide was 4:2 (=BPAFLP:molybdenum oxide). The value was adjusted to be 0.

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

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

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

[0340] Next, a film of BPhen was formed on the first electron transport layer 1114a to a thickness of 20 nm. Then, a second electron transport layer 1114b was formed.

[0341] Furthermore, LiF was evaporated onto the second electron transport layer 1114b to a thickness of 1 nm to form an electron injection layer. 1115 was formed.

[0342] Finally, a 200 nm film of aluminum was deposited as the second electrode 1103, which served as the cathode. The light emitting element 11 of this example was fabricated by vapor deposition so as to have a thickness of 1000 nm.

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

[0344] The first electron transport layer 1114a of the light emitting element 12 is made of DBTBIm-II with a thickness of 30 nm. The layers other than the light-emitting layer 1113 and the first electron transport layer 1114a were formed as follows. was fabricated in the same manner as in the light-emitting device 11.

[0345] In the above-described deposition process, the deposition was all carried out by resistance heating.

[0346] Table 13 shows the element structures of the thus obtained light-emitting elements 11 and 12.

[0347] [Table 13]

[0348] These light emitting devices were placed in a glove box with a nitrogen atmosphere, and the light emitting devices were exposed to the atmosphere. After sealing the device to prevent leakage, the operating characteristics of the light-emitting device were measured. The measurements were carried out at room temperature (atmosphere maintained at 25°C).

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

[0350] Furthermore, the luminance of the light-emitting element 11 and the light-emitting element 12 is 860 cd / m 2 Voltage (V) , current density (mA / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), power The efficiency (lm / W) and external quantum efficiency (%) are shown in Table 14.

[0351] [Table 14]

[0352] Furthermore, the emission spectra when a current of 0.1 mA is applied to the light-emitting elements 11 and 12 are shown in Table 1. In FIG. 48, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit). Also, as shown in Table 14, 860 cd / m 2 The light emitting element 11 and the light emitting element The CIE chromaticity coordinates of the color 12 were (x,y) = (0.53,0.46). The light-emitting elements 11 and 12 are derived from [Ir(mppr-Me)2(dpm)]. It was found that orange light emission was obtained.

[0353] As can be seen from Table 14 and FIGS. 44 to 47, the light-emitting elements 11 and 12 exhibited a current The efficiency, power efficiency, and external quantum efficiency all showed high values.

[0354] The light-emitting devices 11 and 12 were made of 2mDBTPDBq-II or D BTBIm-II, 1'-TNATA, and [Ir(mppr-Me)2(dpm)] , was used in the light-emitting layer. The emission spectrum of the mixture of I and 1'-TNATA is [Ir(mppr-Me)2 (dpm)] absorption spectrum, overlapping with the absorption band that is thought to strongly contribute to the emission. The light emitting element 11 and the light emitting element 12 transfer energy by utilizing this overlap. Therefore, it is thought that the energy transfer efficiency is high and the external quantum efficiency is high. The emission spectrum of the mixture of Im-II and 1'-TNATA is Compared with the emission spectrum of the mixed material of I and 1'-TNATA, there is a large overlap with the absorption band. Therefore, the light emitting element 12 utilizes the large overlap to transfer energy. It is considered that the energy transfer efficiency is higher than that of the light-emitting element 11, and the external quantum efficiency is higher. In addition, by referring to the results of Example 12, it is possible to confirm that the luminescence of the host material in the luminescent layer The energy value of the spectral peak and the lowest energy of the absorption spectrum of the guest material It was found that the difference in energy between the absorption band peak and the absorption band on the side of the Light.

[0355] From the above results, it can be seen that by applying one embodiment of the present invention, a device with high external quantum efficiency can be realized. It was shown that [Example]

[0356] In this example, guest materials and host materials that can be used in a light-emitting element of one embodiment of the present invention are described. An example of the material will be described with reference to FIG.

[0357] The guest material used in this example is [Ir(mppr-Me)2(dpm)]. The host material used in this example is a mixture of 2mDBTPDBq-II and PCBNBB. and 2mDBTPDBq-II and 9-phenyl-9H-3-(9-phenyl-9H- Carbazol-3-yl)carbazole (abbreviation: PCCP) and two types of mixed materials The chemical formulas of the materials used in this example are shown below. 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. Using a visible spectrophotometer (JASCO Corporation, Model V550), a dichloromethane solution (0.0 93 mmol / L) was placed in a quartz cell and measurements were carried out at room temperature.

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

[0361] From the absorption spectrum f of Figure 49(A), [Ir(mppr-Me)2(dpm)] is 5 It can be seen that there is a broad absorption band around 0.00 nm. This absorption band strongly contributes to the emission. It is thought that this is an absorption band.

[0362] The peaks of the emission spectrum f-1 and the emission spectrum f-2 are It was found that there is a large overlap with the absorption band that is thought to strongly contribute to the emission. The light-emitting device in which the guest material used in the examples and either of the host materials are used in the light-emitting layer is The overlap between the emission spectrum of the host material and the absorption spectrum of the guest material is utilized to Therefore, it is suggested that the energy transfer efficiency is high. It was suggested that a light-emitting device with high photon efficiency could be obtained.

[0363] In addition, from this example, it was found that only a mixed material containing an aromatic amine compound was used as the host material. It was suggested that mixed materials containing carbazole compounds could also be used. [Example]

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

[0365] The method for fabricating the light-emitting elements 13 and 14 of this example will be described below.

[0366] (Light-emitting element 13) First, a film of ITSO was formed on a glass substrate 1100 by sputtering, and the film served as an anode. The first electrode 1101 was formed to a thickness of 110 nm and an area of ​​2 mm x 2 mm.

[0367] Next, as a pretreatment for forming a light emitting element 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 The substrate is placed in a vacuum deposition apparatus whose inside pressure has been reduced to about 100 Pa. After vacuum baking at 170° C. for 30 minutes in the heating chamber of the device, the substrate 1100 was It was left to cool for about 0 minutes.

[0369] Next, the surface on which the first electrode 1101 is formed is placed downward. The substrate 1100 thus formed is fixed to a substrate holder provided in a vacuum deposition apparatus, and 10 -4 P After the pressure was reduced to about 1000 kJ / cm, BPAFLP and molybdenum oxide (VI ) was co-evaporated to form a hole injection layer 1111. The thickness of the layer was set to 40 nm. The weight ratio of PAFLP to molybdenum oxide was 4:2 (=BPAFLP:molybdenum oxide). The value was adjusted to be 0.

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

[0371] Furthermore, 2mDBTPDBq-II, PCBNBB, and [Ir(mppr-Me)2( dpm)] was co-evaporated to form a light-emitting layer 1113 on the hole transport layer 1112. mDBTPDBq-II, PCBNBB and [Ir(mppr-Me)2(dpm)] The weight ratio was 0.8:0.2:0.05 (=2mDBTPDBq-II:PCBNBB:[ The light-emitting layer 1113 was adjusted to have a thickness of 1000 nm. The film thickness was set to 20 nm.

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

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

[0374] Furthermore, LiF was evaporated onto the second electron transport layer 1114b to a thickness of 1 nm to form an electron injection layer. 1115 was formed.

[0375] Finally, a 200 nm film of aluminum was deposited as the second electrode 1103, which served as the cathode. The light emitting element 13 of this example was fabricated by vapor deposition so as to have a thickness of 1000 nm.

[0376] (Light emitting element 14) The light-emitting layer 1113 of the light-emitting element 14 is made of 2mDBTPDBq-II, 9-phenyl-9H-3 -(9-phenyl-9H-carbazol-3-yl)carbazole (abbreviation: PCCP) and It was formed by co-evaporation of [Ir(mppr-Me)2(dpm)] and [Ir(mppr-Me)2(dpm)]. 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 thickness of the light-emitting layer 1113 was adjusted to 2 The thickness was set to 0 nm. The light-emitting element 11 was fabricated in the same manner as the light-emitting element 13 except for the light-emitting layer 1113.

[0377] In the above-described deposition process, the deposition was all carried out by resistance heating.

[0378] Table 15 shows the element structures of the thus obtained light-emitting elements 13 and 14.

[0379] [Table 15]

[0380] These light emitting devices were placed in a glove box with a nitrogen atmosphere, and the light emitting devices were exposed to the atmosphere. After sealing the device to prevent leakage, the operating characteristics of the light-emitting device were measured. The measurements were carried out at room temperature (atmosphere maintained at 25°C).

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

[0382] Furthermore, the luminance of the light-emitting element 13 and the light-emitting element 14 is 1200 cd / m 2 Voltage at (V ), current density (mA / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency (cd / A), power The power efficiency (lm / W) and external quantum efficiency (%) are shown in Table 16.

[0383] [Table 16]

[0384] The emission spectra when a current of 0.1 mA was applied to the light-emitting elements 13 and 14 were , shown in Figure 54. In Figure 54, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit). Also, as shown in Table 16, 1200 cd / m 2 CIE 13 of the luminance of the light emitting element The chromaticity coordinates are (x,y)=(0.54,0.45), which is 1200cd / m 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, it can be seen that the light-emitting elements 13 and 14 have the same structure as [Ir(mppr-Me)2(dpm)] It was found that orange luminescence due to

[0385] As can be seen from Table 16 and FIGS. 50 to 53, the light-emitting elements 13 and 14 are The efficiency, power efficiency, and external quantum efficiency all showed high values.

[0386] Light-emitting devices 13 and 14 were prepared by combining 2mDBTPDBq-II shown in Example 14 and P CBNBB or PCCP and [Ir(mppr-Me)2(dpm)] are used for the light-emitting layer. From Example 14, it was found that 2mDBTPDBq-II was mixed with PCBNBB or PCCP. The emission spectrum of the composite material is the absorption spectrum of [Ir(mppr-Me)2(dpm)] The overlap with the absorption band that is thought to strongly contribute to light emission in the light-emitting element 13 and The light emitting element 14 transfers energy by utilizing the overlap, and therefore the energy transfer efficiency is It is considered that the external quantum efficiency is high.

[0387] In addition, from this example, it was found that an aromatic amine compound (PCBNB) was used as the host material for the light-emitting layer. Even if a mixed material containing 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 can be seen that by applying one embodiment of the present invention, a device with high external quantum efficiency can be realized. It was shown that

[0389] (Reference example 1) The organometallic complex used in the above examples, (acetylacetonato)bis(4,6-diphenylpiperidinyl) Bis[2-(6-phenyl-4-pyrimidinato)iridium(III)] [2,4-pentanedionato-κ](2,4-diol-κN3)phenyl-κC](2,4-pentanedionato-κ 2 O,O') Iridium (III)) (abbreviation: [Ir(dppm)2(acac)]) is shown below. The structure of [Ir(dppm)2(acac)] is shown below.

[0390] [ka]

[0391] <Step 1: Synthesis of 4,6-diphenylpyrimidine (abbreviation: Hdppm)> First, 5.02 g of 4,6-dichloropyrimidine, 8.29 g of phenylboronic acid, and sodium carbonate were added. 7.19g of sodium, bis(triphenylphosphine)palladium(II) dichloride (abbreviated Name: Pd(PPh3)2Cl2) 0.29 g, water 20 mL, acetonitrile 20 mL, The reaction vessel was placed in a recovery flask equipped with a reflux condenser, and the inside of the flask was replaced with argon. The sample was heated by irradiating it with microwaves (2.45 GHz, 100 W) for 60 minutes. 2.08g of boronic acid, 1.79g of sodium carbonate, 0.07g of Pd(PPh3)2Cl2 0g, 5mL of water, and 5mL of acetonitrile were placed in a flask and microwaved again (2.45G The solution was heated by irradiating it with a 100W (100Hz) lamp for 60 minutes. The organic layer was extracted with chloromethane. The resulting extract was washed with water and then extracted with magnesium sulfate. The dried solution was filtered. The solvent of this solution was evaporated, and the resulting residue was The product was purified by silica gel column chromatography using dichloromethane as a developing solvent. The rimidine derivative Hdppm was obtained (yellowish white powder, 38% yield). A microwave synthesizer (Discover manufactured by CEM) was used for this synthesis. The synthesis scheme (a-1) is shown below.

[0392] [ka]

[0393] Step 2: Di-μ-chloro-bis[bis(4,6-diphenylpyrimidinato)iridi Synthesis of [Ir(dppm)2Cl]2 Next, 15 mL of 2-ethoxyethanol, 5 mL of water, and the Hdppm1 obtained in Step 1 above were added. 0.10g, iridium chloride hydrate (IrCl3·H2O) 0.69g, The flask was then filled with argon. The mixture was irradiated with a 5 GHz 100 W power source for 1 hour to cause a reaction. After the solvent was distilled off, the resulting residue was After filtration and washing with ethanol, the dinuclear complex [Ir(dppm)2Cl]2 (red Brown powder, 88% yield. The synthesis scheme for step 2 (a-2) is shown below.

[0394] [ka]

[0395] Step 3: (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridide Synthesis of Ir(III) (abbreviation: [Ir(dppm)2(acac)]) Furthermore, 40 mL of 2-ethoxyethanol and [Ir(dppm)2 obtained in Step 2 above] 1.44 g of Cl2, 0.30 g of acetylacetone, and 1.07 g of sodium carbonate were refluxed. The flask was then filled with argon. The reaction was carried out by irradiating the mixture with microwaves (2.45 GHz, 120 W) for 60 minutes. The resulting residue was dissolved in dichloromethane and filtered to remove insoluble matter. The solution was washed with saturated saline and dried over magnesium sulfate. After distilling off the solvent from this solution, the resulting residue was diluted with dichloromethane:ethyl acetate=50: The product was purified by silica gel column chromatography using 1 (volume ratio) as the developing solvent. The target orange powder was obtained by recrystallization in a mixed solvent of dichloromethane and hexane. The compound was obtained (yield 32%). The synthesis scheme (a-3) of step 3 is shown below.

[0396] [ka]

[0397] Nuclear magnetic resonance spectroscopy ( 1 H NMR analysis results The results are shown below. From these results, it was found that the organometallic complex [Ir(dppm)2(acac)] was obtained. It was found 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-phenyl) Bis[2-(6-methyl-4-pyrimidinato)iridium(III)] 2,4-Pentanedionato-κN3)phenyl-κC](2,4-pent ... 2 O,O') Iriji The following is a synthesis example of Ir(mppm)2(acac) (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, 4.90 g of 4-chloro-6-methylpyrimidine, 4.80 g of phenylboronic acid, and charcoal sodium phosphate 4.03g, bis(triphenylphosphine)palladium(II) dichloride 0.16 g of Pd(PPh3)2Cl2, 20 mL of water, 10 mL of acetonitrile L was placed in a recovery flask equipped with a reflux condenser, and the inside of the flask was replaced with argon. The material was heated by irradiating it with microwaves (2.45 GHz, 100 W) for 60 minutes. 2.28 g of phenylboronic acid, 2.02 g of sodium carbonate, Pd(PPh3)2Cl2 0.082g, 5mL of water, and 10mL of acetonitrile were placed in a flask and microwaved again ( The solution was heated by irradiating it with a 2.45 GHz (100 W) power for 60 minutes. The extract was diluted with saturated aqueous sodium carbonate, water, The solution was then washed with saturated saline and dried over magnesium sulfate. The solvent was removed from this solution by distillation, and the resulting residue was diluted with dichloromethane:ethyl acetate=9 The desired product was purified by silica gel column chromatography using a 1:1 (volume ratio) developing solvent. The pyrimidine derivative Hmppm was obtained (orange oil, 46% yield). The irradiation was carried out using a microwave synthesis device (Discover manufactured by CEM). 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 were added. 0.51g, 1.26g of iridium chloride hydrate (IrCl3·H2O) The flask was then filled with argon. The mixture was irradiated with a 5 GHz 100 W power source for 1 hour to cause a reaction. After the solvent was distilled off, the resulting residue was The binuclear complex [Ir(mppm)2Cl]2 was obtained by washing with ethanol and filtering. (Dark green powder, 77% yield). The synthesis scheme (b-2) of Step 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 binuclear complex [Ir(mp pm)2Cl]2 1.84 g, acetylacetone 0.48 g, sodium carbonate 1.73 g The contents were placed in a recovery flask equipped with a reflux condenser, and the atmosphere in the recovery flask was replaced with argon. The reaction was carried out by irradiating with microwaves (2.45 GHz, 120 W) for 60 minutes. The resulting residue was dissolved in dichloromethane and filtered to remove insoluble matter. The solution was washed with water, then saturated saline, and dried over magnesium sulfate. The solution was filtered, and the solvent was evaporated, and the resulting residue was diluted with dichloromethane:ethyl acetate The product was purified by silica gel column chromatography using a 4:1 (volume ratio) developing solvent. After that, the target substance was recrystallized in a mixed solvent of dichloromethane and hexane to obtain a yellow crystalline solid. It was obtained as a powder (yield 22%). The synthesis scheme of step 3 (b-3) is shown below.

[0406] [ka]

[0407] Nuclear magnetic resonance spectroscopy ( 1 H NMR analysis results The results are shown below. From these results, it was found that the organometallic complex [Ir(mppm)2(acac)] was obtained. It was found 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) (synonym: bis[2-(6-tert -butyl-4-pyrimidinyl-κN3)phenyl-κC](2,4-pentanedionato- κ 2 O,O')iridium(III) (abbreviation: [Ir(tBuppm)2(acac) The structure of [Ir(tBuppm)2(acac)] is shown below. vinegar.

[0410] [ka]

[0411] Step 1: 4-tert-butyl-6-phenylpyrimidine (abbreviation: HtBuppm ) Synthesis First, 22.5 g of 4,4-dimethyl-1-phenylpentane-1,3-dione and formaldehyde 50 g of mide was placed in a recovery flask equipped with a reflux condenser, and the inside of the flask was replaced with nitrogen. The reaction solution was refluxed for 5 hours by heating. The organic layer was extracted with dichloromethane, and the obtained organic layer was washed with water and saturated brine. The solution was washed and dried over magnesium sulfate. After drying, the solution was filtered. After distilling off the solvent, the resulting residue was mixed with hexane:ethyl acetate=10:1 (volume ratio) as a developing solvent. The pyrimidine derivative HtBupp was purified by silica gel column chromatography using a solvent. m was obtained (colorless oil, 14% yield). The synthesis scheme of step 1 is shown in (c-1) below. vinegar.

[0412] [ka]

[0413] Step 2: Di-μ-chloro-bis[bis(6-tert-butyl-4-phenylpyridine] Synthesis of [Ir(tBuppm)2Cl]2 > Next, 15 mL of 2-ethoxyethanol, 5 mL of water, and the HtBupp obtained in step 1 above were added. 1.49 g of iridium chloride hydrate (IrCl3·H2O) was added to a The flask was then purged with argon. The mixture was irradiated with a 5 GHz 100 W power source for 1 hour to cause a reaction. After the solvent was distilled off, the resulting residue was After suction filtration and washing with ethanol, the binuclear complex [Ir(tBuppm)2Cl]2 (yellow) was obtained. Green powder, 73% yield. The synthesis scheme for step 2 is shown below in (c-2).

[0414] [ka]

[0415] Step 3: (acetylacetonato)bis(6-tert-butyl-4-phenylpyridine) Iridium(III) (abbreviation: [Ir(tBuppm)2(acac)]) > Furthermore, 40 mL of 2-ethoxyethanol and the binuclear complex [Ir(tB uppm)2Cl]21.61 g, acetylacetone 0.36 g, sodium carbonate 1. 27 g was placed in a recovery flask equipped with a reflux condenser, and the atmosphere in the flask was replaced with argon. The mixture was irradiated with microwaves (2.45 GHz, 120 W) for 60 minutes to react. The resulting residue was filtered off with ethanol and washed with water and ethanol. Dissolved in chloromethane, Celite (Wako Pure Chemical Industries, Ltd., Catalog No. 531-1 The mixture was filtered through a filter aid consisting of layers of 6855, alumina, and celite in that order. The solid obtained by removal of the solvent was recrystallized in a mixed solvent of dichloromethane and hexane, The target product was obtained as a yellow powder (yield 68%). The synthesis scheme of step 3 is shown below (c-3 ) shown.

[0416] [ka]

[0417] Nuclear magnetic resonance spectroscopy ( 1 H NMR analysis results The results are shown below. From these results, it is clear that the organometallic complex [Ir(tBuppm)2(acac)] It was found that it was obtained.

[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[ f,h]quinoxaline (abbreviation: 2mDBTPDBq-II) synthesis method is explained. .

[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]quinoxalate The synthesis scheme of the compound (abbreviation: 2mDBTPDBq-II) is shown in (d-1).

[0422] [ka]

[0423] In a 2 L three-neck flask, add 5.3 g (20 mmol) of 2-chlorodibenzo[f,h]quinoxaline. ), 3-(dibenzothiophen-4-yl)phenylboronic acid 6.1g (20mmol) , tetrakis(triphenylphosphine)palladium(0) 460 mg (0.4 mmol ), 300 mL of toluene, 20 mL of ethanol, and 20 mL of 2 M potassium carbonate aqueous solution were added. This mixture was degassed by stirring under reduced pressure, and the atmosphere inside the three-neck flask was replaced with nitrogen. The mixture was stirred at 100°C for 7.5 hours under a nitrogen atmosphere. The mixture was filtered to obtain a white residue. The residue was washed with water and then with ethanol. The resulting solid was dissolved in approximately 600 mL of hot toluene and then passed through a pad of Celite and Floridian. The resulting filtrate was concentrated to about 700 mL. The product was purified by silica gel column chromatography using hot toluene. The solid obtained here was mixed with acetone and ethanol and then subjected to ultrasonic irradiation. After irradiation, the resulting suspension was filtered and dried to give a white powder (yield: 7.85 g, The yield was 80%.

[0424] The above target material was relatively soluble in hot toluene, but was prone to precipitation when cooled. In addition, it was poorly soluble in other organic solvents such as acetone and ethanol. By taking advantage of the difference in decomposition rate, it was possible to synthesize the compound in a simple and efficient manner. After the reaction is complete, the mixture is returned to room temperature and the precipitated solid is collected by filtration, which allows most of the impurities to be easily removed. In addition, column chromatography using hot toluene as a developing solvent was performed. This enabled us to easily purify target compounds that tend to precipitate.

[0425] 4.0 g of the obtained white powder was purified by train sublimation. The white powder was heated to 300°C under the conditions of a pressure of 5.0 Pa and an argon flow rate of 5 mL / min. After purification by sublimation, 3.5 g of the target white powder was obtained in a yield of 88%.

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

[0427] of the obtained material 1 The 1 H 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 Light-emitting layer 704 Electron transport layer 705 Electron injection layer 706 Electron injection buffer layer 707 Electronic Relay Layer 708 Composite material layer 800 First EL layer 801 Second EL layer 803 Charge generation layer 1100 board 1101 First electrode 1103 Second electrode 1111 Hole injection layer 1112 Hole transport layer 1113 Light-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 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.

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 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.

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 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 0.1 eV.

6. 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, 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 0.1 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 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 0.2 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 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 0.2 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 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.

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 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.

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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