Light-emitting element

Abstract

To provide a light emitting element in which a plurality of light emitting substances emit light in a well-balanced manner, a light emitting element with high luminous efficiency, and a highly reliable light emitting element.SOLUTION: A light emitting element includes a first electrode, a first light emitting layer containing a first phosphorescent compound and a first host material on the first electrode, a second emissive layer containing a second phosphorescent compound and a second host material on the first light emitting layer, a third light emitting layer containing a third phosphorescent compound and a third host material on the second light emitting layer, and a second electrode on the third light emitting layer. The peak of emitted light of the second phosphorescent compound among the first phosphorescent compound, the second phosphorescent compound, and the third phosphorescent compound is on the longest wavelength side, and the peak of emitted light of the third phosphorescent compound is on the shortest wavelength side. The triplet excitation energy of the third host material is higher than the triplet excitation energies of the first host material and the second host material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light-emitting element, a lighting device, a light-emitting device, and an electronic device. Electroluminescence (hereinafter referred to as EL) phenomenon is used. The present invention relates to a light-emitting element, a lighting device, a light-emitting device, and an electronic device using the same. [Background technology]

[0002] Research and development of light-emitting devices that utilize the EL phenomenon is being actively pursued. The basic structure is a layer containing a light-emitting organic compound (hereinafter also referred to as an EL layer) between a pair of electrodes. Light-emitting devices that utilize the EL phenomenon can be made thin and lightweight, and are highly sensitive to input signals. Its characteristics include fast response and low DC voltage drive, making it a promising next-generation flat panel. In addition, displays using such light-emitting elements are attracting attention as The light-emitting device also has the characteristics of excellent contrast and image quality, and a wide viewing angle. Since it is a surface light source, it can also be used as a light source for backlighting of LCD displays and lighting. It is given.

[0003] A light-emitting element in which an organic compound is used as a light-emitting substance and a layer containing the organic compound is provided between a pair of electrodes. In this case, by applying a voltage to the element, electrons are emitted from the cathode and holes are emitted from the anode. The electrons and positive charges are injected into the layer containing the organic compound, causing a current to flow. The holes bring the organic compound into an excited state, and light is emitted from the excited organic compound.

[0004] The types of excited states that organic compounds can form are singlet excited states and triplet excited states. and the singlet excited state (S *) is emitted from the triplet excited state (T * ) This is called phosphorescence. Here, the compounds that emit fluorescence (hereinafter also referred to as fluorescent compounds) are At room temperature, phosphorescence is usually not observed, but fluorescence alone. The internal quantum efficiency (the photons generated for the injected carriers) of light-emitting devices using The theoretical limit of the ratio of the singlet excited state to the triplet excited state is 25%. It is said that...

[0005] On the other hand, if a compound that emits phosphorescence (hereinafter also referred to as a phosphorescent compound) is used, the internal quantity The efficiency of the photovoltaic device can be increased to 100%. For this reason, it is possible to obtain a high luminous efficiency. Therefore, in recent years, there has been active development of light-emitting devices using phosphorescent compounds.

[0006] Patent Document 1 discloses a light-emitting device having a blue light-emitting layer and an orange light-emitting layer using a phosphorescent material. An optical device is disclosed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent Application Publication No. 2005 / 0074630 Summary of the Invention [Problem to be solved by the invention]

[0008] Although phosphorescent compounds can theoretically achieve an internal quantum efficiency of 100%, It is difficult to achieve high efficiency without optimizing the combination with other materials. In a light-emitting device using a plurality of phosphorescent compounds with different bands (emission colors) as luminescent materials, In this case, it is necessary to consider not only the energy transfer but also the efficiency of the energy transfer itself. Without optimization, it is difficult to obtain high efficiency light emission.

[0009] In addition, in multicolor light-emitting devices using multiple types of luminescent materials with different luminescent colors, the luminous efficiency can be improved. It is necessary that not only the light-emitting materials emit light of different colors but also that the light-emitting materials emit light of different colors in a well-balanced manner. Achieving efficiency while also balancing the luminescence of each luminescent material is not an easy task.

[0010] In view of the above, one embodiment of the present invention provides a light-emitting element in which a plurality of light-emitting substances emit light in a well-balanced manner. Another object of one embodiment of the present invention is to provide a light-emitting element with high emission efficiency. Another object of one embodiment of the present invention is to provide a light-emitting element with high reliability. This is one of the objectives.

[0011] Another embodiment of the present invention is a light-emitting device with reduced power consumption by using the above-described light-emitting element. It is an object of the present invention to provide an optical device, an electronic device, and a lighting device. One embodiment is a light-emitting device, an electronic device, and a semiconductor device that have high reliability by using the above-described light-emitting element. It is an object of the present invention to provide a lighting device.

[0012] Note that one embodiment of the present invention does not necessarily solve all of the above problems. [Means for solving the problem]

[0013] One aspect of the present invention is a light-emitting device comprising a first electrode, a first phosphorescent compound and a first host compound on the first electrode, a first light-emitting layer including a second phosphorescent compound and a second host material on the first light-emitting layer; a second light-emitting layer including a third phosphorescent compound and a third host material on the second light-emitting layer; a third light-emitting layer containing a first phosphorescent compound; and a second electrode on the third light-emitting layer. , the second phosphorescent compound, and the third phosphorescent compound, the emission peak of the second phosphorescent compound The emission peak of the third phosphorescent compound is at the longest wavelength side, and the emission peak of the third phosphorescent compound is at the shortest wavelength side. The triplet excitation energy of the host material is the triplet excitation energy of the first host material and the second host material. It is a light-emitting element with a higher excitation energy than the nominal excitation energy.

[0014] In the above configuration, the first phosphorescent compound emits green light, and the second phosphorescent compound Preferably, the first phosphorescent compound emits red light, and the second phosphorescent compound emits blue light.

[0015] In this specification, the phosphorescent compound that emits green light has a wavelength of 520 nm or more and 600 nm or less. The phosphorescent compound that has a peak of red light emitted at less than 600 nm and emits light at 700 nm or more is Phosphorescent compounds that have an emission peak at 50 nm or less and emit blue light have an emission peak at 440 nm or less. It has an emission peak at less than 520 nm.

[0016] In each of the above structures, the first host material, the second host material, and the third host material are It is preferable that the first host material, the second host material, and the It is preferable that the third host material has a hole transporting property. The first host material, the second host material, and the third host material have electron transporting and hole transporting properties. It is preferable that the polymer has the following properties.

[0017] In each of the above structures, the first host material, the second host material, and the third host material are positive It is preferable that the host material has a hole transport skeleton and an electron transport skeleton. The saccharin and electron transport backbone may be different or the same.

[0018] In each of the above structures, it is preferable that the first host material and the second host material are the same. stomach.

[0019] In each of the above-described configurations, the first light-emitting layer further contains a first carrier transporting compound, and the first One of the host material and the first carrier transporting compound is a hole transporting compound, and the other is preferably an electron transporting compound.

[0020] In each of the above structures, the second light-emitting layer further contains a second carrier transporting compound, One of the host material and the second carrier transporting compound is a hole transporting compound, and the other is preferably an electron transporting compound.

[0021] In each of the above structures, the third light-emitting layer further contains a third carrier transporting compound, One of the host material and the third carrier transporting compound is a hole transporting compound, and the other is preferably an electron transporting compound.

[0022] In each of the above structures, the thickness of the second light-emitting layer is 2 nm or more and 20 nm or less, preferably 5 nm or less. It is preferable that the thickness is m or more and 10 nm or less.

[0023] In each of the above structures, the second light-emitting layer is preferably in contact with the first light-emitting layer and the third light-emitting layer. Specifically, one embodiment of the present invention is a light-emitting device including a first electrode and a first phosphorescent layer on the first electrode. a first light-emitting layer including the compound and a first host material; and a second phosphorescent material disposed on and in contact with the first light-emitting layer. a second light-emitting layer containing a photoactive compound and a second host material; and a third light-emitting layer disposed on and in contact with the second light-emitting layer. a third light-emitting layer including the phosphorescent compound and a third host material; and a second electrode on the third light-emitting layer. and a first phosphorescent compound, a second phosphorescent compound, and a third phosphorescent compound. The emission peak of the second phosphorescent compound is at the longest wavelength side, and the emission peak of the third phosphorescent compound is at the longest wavelength side. The triplet excitation energy of the third host material is the shortest wavelength. The triplet excitation energy of the second host material is higher than that of the second host material.

[0024] In each of the above structures, the first carrier transporting compound and the second carrier transporting compound are the same. The material may be:

[0025] Note that a light-emitting device, a lighting device, and an electronic device using the light-emitting element having each of the above structures are also embodiments of the present invention. It seems that

[0026] Note that the term "light-emitting device" in this specification includes a display device using a light-emitting element. The device is fitted with a connector, such as anisotropic conductive film, TCP (Tape Carrier P A module with a TCP package attached, and a printed wiring board attached to the TCP. The module or light emitting device is equipped with an IC (integrated circuit) by the COG (Chip On Glass) method. All modules in which a light emitting device (integrated circuit) is directly mounted are also included in the light emitting device. This also includes light-emitting devices used in tools, etc. [Effects of the Invention]

[0027] According to one embodiment of the present invention, a light-emitting element in which a plurality of light-emitting substances emit light in a well-balanced manner can be provided. According to one embodiment of the present invention, a light-emitting element with high emission efficiency can be provided. In this manner, a highly reliable light-emitting element can be provided.

[0028] In one embodiment of the present invention, the above-described light-emitting element is used to reduce power consumption. In one embodiment of the present invention, a light-emitting device, an electronic device, or a lighting device can be provided. By using the optical element, a highly reliable light emitting device, electronic device, or lighting device can be provided. do. [Brief explanation of the drawings]

[0029] [Figure 1] 1A and 1B illustrate examples of light-emitting elements according to embodiments of the present invention. [Figure 2] FIG. 10 is a diagram showing an example of a light-emitting element of a comparative example. [Figure 3] 1A and 1B are diagrams illustrating energy transfer in a light-emitting layer. [Figure 4] 1A and 1B illustrate an example of a light-emitting device according to one embodiment of the present invention. [Figure 5] 1A and 1B illustrate an example of a light-emitting device according to one embodiment of the present invention. [Figure 6] 1A to 1C illustrate examples of electronic devices of one embodiment of the present invention. [Figure 7] FIG. 1 illustrates an example of a lighting device according to one embodiment of the present invention. [Figure 8] 1A and 1B are diagrams showing light-emitting elements according to an embodiment; [Figure 9] FIG. 10 shows luminance-current efficiency characteristics of the light-emitting element of Example 1. [Figure 10] FIG. 10 is a graph showing voltage-luminance characteristics of the light-emitting element of Example 1. [Figure 11] FIG. 1 is a graph showing luminance-external quantum efficiency characteristics of the light-emitting element of Example 1. [Figure 12] FIG. 2 shows an emission spectrum of the light-emitting element of Example 1. [Figure 13] 10 shows the results of a reliability test of the light-emitting element of Example 1. FIG. [Figure 14] FIG. 10 shows luminance-current efficiency characteristics of the light-emitting element of Example 2. [Figure 15] FIG. 10 is a graph showing voltage-luminance characteristics of the light-emitting element of Example 2. [Figure 16] FIG. 10 is a graph showing luminance-external quantum efficiency characteristics of the light-emitting element of Example 2. [Figure 17] FIG. 10 shows an emission spectrum of the light-emitting element of Example 2. [Figure 18] 10 shows the results of a reliability test of the light-emitting element of Example 2. FIG. [Figure 19] 10 shows the results of a reliability test of the light-emitting element of Example 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0030] 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 described.

[0031] In the configuration of the invention described below, the same parts or parts having similar functions are designated by the same reference numerals. The same reference numerals are used in common among different drawings, and the repeated explanations thereof will be omitted. When referring to a function, the hatch pattern may be the same and no particular symbol may be added.

[0032] In addition, the position, size, range, etc. of each component shown in the drawings are not necessarily the same as those in the actual device for ease of understanding. Therefore, the disclosed invention may not necessarily represent the actual position, size, range, etc. The position, size, range, etc. are not necessarily limited to those disclosed in the drawings, etc.

[0033] (Embodiment 1) In this embodiment, a light-emitting element of one embodiment of the present invention will be described with reference to FIGS.

[0034] The gist of one embodiment of the present invention is to use three types of phosphorescent compounds each having a different emission peak wavelength. By efficiently emitting light from all three types of phosphorescent compounds, a multicolor light-emitting device can be realized. The aim is to improve the luminous efficiency and extend the life of the LED.

[0035] A common method for obtaining multicolor light-emitting devices using phosphorescent compounds is to A method of dispersing multiple phosphorescent compounds with different emission peak wavelengths in an appropriate ratio. However, in this case, phosphorescent compounds that emit light at the longest wavelength are Therefore, the device structure (especially the host material) to obtain multicolor emission is It is very difficult to design and control the concentration of each phosphorescent compound.

[0036] Another method for obtaining a multicolor light-emitting element is to connect light-emitting elements with different emission peak wavelengths in series. For example, a blue light-emitting element and a green light-emitting element are stacked on top of each other in a tandem structure. If three light emitting elements, one for the red light emitting element and one for the red light emitting element, are stacked in series and emit light simultaneously, multicolor light (in this case) can be easily produced. The device structure can also be optimized by individually configuring the blue, green, and red devices. However, since the three elements are stacked, Therefore, the number of layers increases, and the fabrication becomes complicated. If a problem occurs in the electrical contact, it may result in an increase in the driving voltage, i.e., power loss. do.

[0037] <Light-emitting element of comparative example> The light-emitting element 300 of the comparative example shown in FIG. 2A has a first electrode 301 and a and a second electrode 305 provided on the EL layer 303. One of the first electrode 301 and the second electrode 305 functions as an anode and the other functions as a cathode. In this embodiment, the first electrode 301 functions as an anode, and the second electrode 3 05 acts as the cathode.

[0038] A voltage higher than the threshold voltage of the light-emitting element is applied between the first electrode 301 and the second electrode 305. When this occurs, holes are injected into the EL layer 303 from the first electrode 301 side, and electrons are injected from the second electrode 305 side. The injected electrons and holes recombine in the EL layer 303, and The luminescent material contained in 3 emits light.

[0039] As shown in FIG. 2B, the EL layer 303 emits red light from the first electrode 301 side. A red light-emitting layer 311R includes a phosphorescent compound 311Rd and a host material 311Rh. A green light-emitting layer 311 containing a phosphorescent compound 311Gd and a host material 311Gh. G. Blue-emitting phosphorescent compound 311Bd and host material 311Bh. The phosphorescent compound contained in each light-emitting layer is dispersed in a host material. The phosphorescent compounds are separated from one another by their respective host materials.

[0040] In this case, electron exchange interactions (the so-called Dexter mechanism) occur between the phosphorescent compounds. In other words, the blue-emitting phosphorescent compound 311B After d is excited, the excitation energy is converted into green phosphorescence by the Dexter mechanism. The phenomenon of migration to the fluorescent compound 311Gd or the phosphorescent compound 311Rd, which emits red light, does not occur. In addition, after the phosphorescent compound 311Gd that emits green light is excited, the excited electrons Energy is transferred to the phosphorescent compound 311Rd, which emits red light, via the Dexter mechanism. Therefore, the phosphorescent compound 311Rd, which emits light at the longest wavelength, is the main Furthermore, the recombination of carriers in the light emitting device 300 is suppressed. The region 311ex is within the blue light-emitting layer 311B or between the blue light-emitting layer 311B and the green light-emitting layer 311B. The blue light-emitting phosphorescent compound 311Bd is mainly used in the vicinity of the interface with 11G. As a result, excitons are generated directly in the red light-emitting layer 311R, The phosphorescent compound 311Rd, which emits red light, is prevented from emitting light.

[0041] However, energy transfer from the blue-emitting phosphorescent compound 311Bd is completely suppressed. If this happens, the red light emitted by the phosphorescent compound 311Rd will not be emitted. Therefore, in the light-emitting element 300, a phosphorescent compound 311Bd that emits blue light is used. The excitation energy is transferred to the phosphorescent compound 311Gd, which partially emits green light. Furthermore, the excitation energy of the phosphorescent compound 311Gd, which emits green light, is partially red. The device is designed so that the light is transferred to the phosphorescent compound 311Rd, which emits light of the formula Energy transfer between such isolated molecules is called dipole-dipole interaction (Förster mechanism). This is possible by using the

[0042] As described above, each phosphorescent compound is dispersed in each host material. The phosphorescent compounds exhibit blue light emission because the compounds are isolated from each other by their respective host materials. All of the excitation energy generated in 311Bd is released via the Förster mechanism to produce green light. The phosphorescent compound 311Gd exhibits red light emission, and the phosphorescent compound 311Rd exhibits red light emission. For example, if the thickness of the green light-emitting layer 311G in FIG. 2(B) is 2 By setting the wavelength to 0 nm or less, partial energy transfer occurs, resulting in phosphorescent compounds 311Bd, Both the phosphorescent compound 311Gd and the phosphorescent compound 311Rd can emit light.

[0043] Energy transfer by the Forster mechanism between the phosphorescent compounds in the light-emitting device 300 A schematic diagram is shown in Figure 3(A). As shown in Figure 3(A), first, a phosphorescent compound 311Bd was used. The singlet excited state (S B ) can be converted to a triplet excited state (T B ) That is, the excitons in the blue light-emitting layer 311B are basically T B It is summarized as follows.

[0044] Next, this T B A part of the exciton energy is directly emitted and converted into blue light. However, by utilizing the Förster mechanism, some of the triplet excitations of the phosphorescent compound 311Gd Waking state (T G ) which is why the phosphorescent compound 311Bd is emissive. The phosphorescent compound 311Gd converts from the singlet ground state to the triplet state. It has a direct absorption corresponding to the electronic transition to the triplet excited state (absorption spectrum of the triplet excited state). If these conditions are met, the Förster mechanism RuT B From T G Triplet-triplet energy transfer to T B from phosphorescent The singlet excited state (S R ) also contributes to the energy transfer to , can occur if the conditions of the Förster mechanism are met. R is a phosphorescent compound due to intersystem crossing. The triplet excited state (T R ), which results in the emission of phosphorescent compound 311Rd. contribute to.

[0045] The phosphorescent compound 311Gd exhibits a singlet excited state (S G ) is the phosphorescent compound 311Bd Triplet excited state (T B ), the energy of the Therefore, it is omitted here.

[0046] Furthermore, the T of the phosphorescent compound 311Gd G A part of the exciton energy is emitted as it is. By utilizing the Förster mechanism, some of the light is converted into phosphorescent compounds. The triplet excited state (T R ) which is a phosphorescent compound. 311Gd is luminescent (high phosphorescence quantum yield φ), and the phosphorescent compound 311Rd It has direct absorption corresponding to the electronic transition from the singlet ground state to the triplet excited state (triplet This is due to the existence of an absorption spectrum in the first excited state. , T by the Förster mechanism G From T R triplet-triplet energy transfer to The T generated by the energy transfer described above R is the phosphorescent compound 311Rd In this way, light can be emitted from each of the phosphorescent compounds. do.

[0047] In addition, the energy donor in the Förster mechanism (in the light-emitting device 300, the phosphorescent compound 311Bd and phosphorescent compounds 311Gd) must be luminescent, so The phosphorescence quantum yields of 311Bd and the phosphorescent compound 311Gd are each 0.1 or more. It is preferable that:

[0048] As described above, the light-emitting device 300 of the comparative example has a structure in which each phosphorescent compound is mixed with a host material and a laminated layer. A device that primarily excites phosphorescent compounds that emit light at the shortest wavelength while isolating them using a structure In such an element structure, the distance between the electrodes is within a certain distance (for example, within 20 nm). ) energy transfer occurs partially via the Förster mechanism, resulting in blue light emission. The excitation energy of the phosphorescent compound exhibiting green light is partially transferred to the phosphorescent compound exhibiting green light. Furthermore, the excitation energy of the phosphorescent compound that emits green light is partially transferred to the red light. The light is transferred to a phosphorescent compound exhibiting the light emission of the formula (I), and light can be obtained from each phosphorescent compound.

[0049] However, if the blue light-emitting layer 311B deteriorates during operation, part of the energy of the excitons is transferred to the deteriorated material. In other words, the quencher is located at the position indicated by Q in Figure 3(A). It is believed that the energy level of the quencher (cha) is generated. As shown in Figure 3(A), The energy of the quencher is the T of the phosphorescent compound 311Gd. G lower than the exciton energy of Therefore, the T of the phosphorescent compound 311Bd B One of the exciton energies When the exciton is transferred to the quencher, the energy of the exciton on the quencher is then transferred to the phosphorescent compound. T of substance 311Gd G , and further, T of phosphorescent compound 311Rd R It is difficult to move to. That is, the T of the phosphorescent compound 311GdG , and further, T of phosphorescent compound 311Rd R Generation of This is one of the causes of the shortened life and reduced reliability of the light emitting element 300. It is thought that this is the case.

[0050] <Light-emitting element of one embodiment of the present invention> On the other hand, in the light-emitting element of one embodiment of the present invention, the light emitting layer that exhibits the shortest wavelength of light among the three light-emitting layers an emitting layer containing a phosphorescent compound and an emitting layer containing a phosphorescent compound that emits light at the longest wavelength; In addition, in the light-emitting element of one embodiment of the present invention, each of the three light-emitting layers is The recombination of carriers occurs.

[0051] The light-emitting element of one embodiment of the present invention shown in FIG. 1A includes a first electrode 101 and a second electrode 102. an EL layer 103 provided on the first electrode 102; and a second electrode 105 provided on the EL layer 103. One of the first electrode 101 and the second electrode 105 functions as an anode, and the other functions as a cathode. In this embodiment, the first electrode 101 functions as an anode, and the second electrode 105 functions as a cathode.

[0052] A voltage higher than the threshold voltage of the light-emitting element is applied between the first electrode 101 and the second electrode 105. When this occurs, holes are injected into the EL layer 103 from the first electrode 101 side, and electrons are injected from the second electrode 105 side. The injected electrons and holes recombine in the EL layer 103, and The luminescent material contained in 3 emits light.

[0053] The EL layer 103 has at least a light-emitting layer 203. The EL layer 103 does not include any layer other than the light-emitting layer. As the above, a hole injecting or electron injecting substance, a hole transporting or electron transporting substance, or The semiconductor device further includes a layer containing a bipolar substance (a substance having high electron transporting and hole transporting properties). The EL layer 103 may be made of either a low molecular weight compound or a high molecular weight compound. It may also contain an inorganic compound.

[0054] As shown in FIG. 1A, the light-emitting element of one embodiment of the present invention includes a first electrode as the light-emitting layer 203. A first light-emitting layer 203x on the electrode 101 and a second light-emitting layer 203y on the first light-emitting layer 203x and a third light-emitting layer 203z on the second light-emitting layer 203y. The three light-emitting layers are preferably provided in contact with each other, unlike the tandem structure. With this configuration, the recombination distribution of carriers between the light-emitting layers of each color can be adjusted, ultimately resulting in It is possible to obtain uniform light emission from the light-emitting layers of each color.

[0055] The first light-emitting layer 203x includes a first phosphorescent compound and a first host material. Layer 203y includes a second phosphorescent compound and a second host material. The compound includes a third phosphorescent compound and a third host material, where the first phosphorescent compound, the second Among the second phosphorescent compound and the third phosphorescent compound, the second phosphorescent compound has the highest emission peak. The emission peak of the third phosphorescent compound is on the long wavelength side, and the emission peak of the third phosphorescent compound is on the shortest wavelength side. The triplet excitation energy of the third host material is the triplet excitation energy of the first host material and the second host material. higher than the singlet excitation energy.

[0056] In the light-emitting element of one embodiment of the present invention, a first host material, a second host material, and a third host material are Alternatively, in the light-emitting element of one embodiment of the present invention, the first host material The first host material, the second host material, and the third host material have hole transport properties. In one embodiment of the light-emitting element, the first host material, the second host material, and the third host material In a light-emitting element to which any of these structures is applied, the light-emitting element has an electron transport property and a hole transport property. The recombination region of the carriers in the semiconductor layer is widely present from the first light-emitting layer to the third light-emitting layer. Therefore, the luminescent material contained in each luminescent layer emits light efficiently, resulting in a highly efficient multicolor light-emitting device. can be obtained.

[0057] For example, a third light-emitting layer (a light-emitting layer containing a phosphorescent compound whose emission peak has the shortest wavelength) is formed on the anode side. In the case where the light-emitting layer is provided, it is preferable that the host material of each light-emitting layer has hole transport properties. In the case where a third emitting layer is provided on the cathode side as in the present embodiment, the host material of each emitting layer is It is preferable that the material has electron transport properties.

[0058] In addition, the first host material, the second host material, and the third host material each have a hole transporting property. It is preferred that the polymer has a backbone and an electron transport backbone.

[0059] Examples of hole transport skeletons include aromatic amines and π-electron-rich heteroaromatic rings. The π-electron-rich heteroaromatic ring is preferred because of its high chemical and thermal stability. Examples of the heteroaromatic ring include a heteroaromatic ring containing a pyrrole skeleton, a heteroaromatic ring containing a furan skeleton, Examples of the aromatic heterocyclic ring include thiophene skeleton-containing aromatic heterocyclic rings. Examples include dibenzo[c,g]carbazole, dibenzofuran, and dibenzothiophene skeletons. can be done.

[0060] As the electron transport skeleton, a π-electron deficient heteroaromatic ring is preferred because it has excellent electron transport properties. The π-electron deficient heteroaromatic rings include heteroaromatic rings containing a pyridine skeleton and a phthalazine skeleton. heteroaromatic rings containing a pyrimidine skeleton, heteroaromatic rings containing a pyrazine skeleton, Heteroaromatic rings containing a riazine skeleton, heteroaromatic rings containing an imidazole skeleton, and oxazole skeletons heteroaromatic rings containing a thiazole skeleton, heteroaromatic rings containing a triazole skeleton Specific examples include pyridine, pyrimidine, quinoxaline, dibenzoyl Examples include the skeletons of zo[f,h]quinoxaline and benzimidazole.

[0061] The hole transport skeleton and the electron transport skeleton of each host material may be different from each other. , may be the same.

[0062] However, the triplet excitation energy of the third host material is higher than that of the first host material and the second host material. Since the triplet excitation energy is higher than that of the host material, the hole transport skeleton of the third host material The electron transport skeleton is a hole transport skeleton or an electron transport skeleton of the first host material or the second host material. It is preferable that the triplet excitation of the electron transport skeleton of the third host material is different from that of the electron transport skeleton of the third host material. The photovoltaic energy is generated by the triplet excitation of the electron transport skeleton of the first host material and the second host material. It is preferable that the voltage is higher than the electromotive force.

[0063] On the other hand, the hole transport skeleton and the electron transport skeleton of the first host material and the second host material are the same. It is particularly preferred that the electron transport skeletons are the same. In order to induce carrier recombination in both the first and second light-emitting layers, This is because the carrier movement between the light-emitting layers needs to be smooth. It is more preferred that the first and second host materials are the same.

[0064] In the light-emitting element of one embodiment of the present invention, the first light-emitting layer contains a first carrier-transporting compound. In this case, the first host material or the first carrier transporting compound may contain One is a hole transporting compound and the other is an electron transporting compound. It is preferable that the combination of the first carrier transporting compound and the second carrier transporting compound forms an exciplex. stomach.

[0065] Similarly, in the light-emitting element according to one embodiment of the present invention, the second light-emitting layer may include a second carrier-transporting layer. In this case, the second host material or the second carrier transporting compound may be contained. One of the compounds is a hole transporting compound and the other is an electron transporting compound. It is preferable that the material and the second carrier transporting compound are a combination that forms an exciplex. It's nice.

[0066] Similarly, in the light-emitting element according to one embodiment of the present invention, the third light-emitting layer may include a third carrier-transporting layer. In this case, the third host material or the third carrier transporting compound may be contained. One of the compounds is a hole transporting compound and the other is an electron transporting compound. It is preferable that the material and the third carrier transporting compound are a combination that forms an exciplex. It's nice.

[0067] The transport property of the light-emitting layer containing the carrier transport compound is determined by the host material and the carrier transport compound ( That is, the property is adjusted by changing the mixing ratio of the electron transport compound and the hole transport compound. It is possible.

[0068] A more detailed example of the light-emitting layer 203 is shown in FIG. 1(B). The light-emitting layer 203 shown in FIG. 1(B) is From the electrode 101 side of the photosensitive drum 1, a phosphorescent compound 203Gd that emits green light and a host material 20 A green light-emitting layer 203G containing a phosphorescent compound 203Rd and a phosphorescent compound 203Rd exhibiting red light emission. a red light-emitting layer 203R containing a phosphorescent material 203Rh; a blue light-emitting phosphorescent compound 203B; The blue light-emitting layer 203B contains a phosphorus 203b and a host material 203bh. The phosphorescent compounds are dispersed in the respective host materials, and the phosphorescent compounds are dispersed in the respective host materials. are isolated from each other by

[0069] In this case, electron exchange interactions (the so-called Dexter mechanism) occur between the phosphorescent compounds. That is, the blue-emitting phosphorescent compound 203B After d is excited, the excitation energy is converted into green phosphorescence by the Dexter mechanism. The phenomenon of migration to the fluorescent compound 203Gd or the phosphorescent compound 203Rd exhibiting red luminescence did not occur. In addition, after the phosphorescent compound 203Gd that emits green light is excited, the excited electrons Energy is transferred to the phosphorescent compound 203Rd, which emits red light, via the Dexter mechanism. Therefore, the phosphorescent compound 203Rd, which emits light at the longest wavelength, is the main This suppresses the phenomenon of light emission.

[0070] The recombination region of carriers in a light-emitting element to which the structure of the light-emitting layer 203 shown in FIG. 1(B) is applied The region is widely present from the blue light-emitting layer 203B to the green light-emitting layer 203G. The regeneration of the carriers occurs in the light-emitting layer 203B, the red light-emitting layer 203R, and the green light-emitting layer 203G. The binding region is present.

[0071] In the light-emitting element of one embodiment of the present invention, carrier recombination occurs in each layer constituting the light-emitting layer 203. Here, the singlet excited state (S B ) can be converted to a triplet excited state (T B ) is converted into blue light-emitting layer 2. The exciton in O3B is basically T B This T B The exciton energy of Similarly, phosphorescent compound 2, which emits red light, emits red light and is converted into blue light. The singlet excited state (S R ) can be converted to a triplet excited state (T R ) That is, the excitons in the red light-emitting layer 203R are basically converted into T R Consolidated into This T R The exciton energy is converted into red light by light emission. The singlet excited state (S) generated in the green-emitting phosphorescent compound 203Gd G ) is an intersystem The triplet excited state (T G ) in the green light-emitting layer 203G. The exciton is basically T G This T G The energy of the exciton is directly emitted and converted into green light.

[0072] In this way, the recombination region of the carriers in the light-emitting device is included in each light-emitting layer. This allows carriers to be recombined in each light-emitting layer, and the phosphorescent compounds contained in each light-emitting layer Light can be emitted from each of these.

[0073] In the light-emitting element of one embodiment of the present invention, T BThe exciton energy of The device is designed to move to compound 203Rd or phosphorescent compound 203Gd. Energy transfer between isolated molecules such as This is possible by utilizing the mechanism.

[0074] As described above, each phosphorescent compound is dispersed in each host material. The compounds are isolated from each other by their respective host materials, resulting in the phosphorescent compound 203Bd. All of the excitation energy is transferred to the phosphorescent compound 203Rd and the phosphorescent compound 203Rd via the Förster mechanism. For example, in Figure 1(B), the red By setting the film thickness of the color light-emitting layer 203R to 2 nm or more and 20 nm or less, partial energy transfer can be achieved. The phosphorescent compound 203Bd, the phosphorescent compound 203Rd, and the phosphorescent compound 203 Gd can be made to emit light.

[0075] In the light-emitting element of one embodiment of the present invention, energy is transferred between the phosphorescent compounds by the Förster mechanism. A schematic diagram of energy transfer is shown in FIG. 3(B). As shown in FIG. 3(B), first, phosphorescent compound 20 The singlet excited state (S B ) can be converted to a triplet excited state (T B ) That is, the excitons in the blue light-emitting layer 203B are basically converted into T B be summarized in .

[0076] Next, this T B A part of the exciton energy is directly emitted and converted into blue light. However, by utilizing the Förster mechanism, some of the triplet excitations of the phosphorescent compound 203Gd Waking state (T G) which is why the phosphorescent compound 203Bd is emissive. The phosphorescent compound 203Gd is capable of converting from the singlet ground state to the triplet state. It has a direct absorption corresponding to the electronic transition to the triplet excited state (absorption spectrum of the triplet excited state). If these conditions are met, the Förster mechanism RuT B From T G Triplet-triplet energy transfer to T B from phosphorescent The triplet excited state (T G ) also contributes to the energy transfer to , this can occur if the conditions of the Förster mechanism are met. G is the emission of phosphorescent compound 203Gd In addition, the energy donor in the Förster mechanism (here, the phosphorescent compound Since 203Bd) must be luminescent, the phosphorescence quantum yield of the phosphorescent compound 203Bd is , preferably 0.1 or more.

[0077] In the light-emitting element of one embodiment of the present invention, when the blue light-emitting layer 203B deteriorates during operation, the excitation Part of the energy of the molecule is quenched by the degradation product. B) It is thought that the energy level of the quencher is generated at the position indicated by Q. However, as shown in FIG. 3(B), the energy of the quencher is Rd T R Since the exciton energy is thought to be higher than that of the phosphorescent compound 311Bd T B When part of the energy of the exciton is transferred to the quencher, The exciton energy is T R Therefore, Therefore, in comparison with the light-emitting element 300 of the comparative example, the light-emitting element of one embodiment of the present invention exhibits a higher luminance due to the quencher. The T of the phosphorescent compound 311Gd G and T of phosphorescent compound 311Rd R This causes a disruption in the production of Therefore, by applying one embodiment of the present invention, the light-emitting element 300 can be obtained more satisfactorily than the light-emitting element 300 of the comparative example. This makes it possible to realize a light emitting device with a long life and high reliability.

[0078] In other words, the emitting layer where the quencher is generated and the adjacent emitting layer have higher energy than the quencher. By incorporating a phosphorescent compound with a triplet excited state energy lower than that of the It is possible to suppress a decrease in the life span and reliability of the light emitting element due to the generation of ions.

[0079] When the host material 203Rh and the host material 203Gh are the same, the green light-emitting layer 20 3G is easily accessible by carriers, T B From T G Advantages include the fact that energy transfer to There is, and it is preferable.

[0080] As described above, in the light-emitting element of one embodiment of the present invention, carrier recombination occurs in each light-emitting layer. Therefore, light can be emitted from each of the phosphorescent compounds contained in each light-emitting layer. In the energy transfer between light-emitting layers using the Wörster mechanism, triplet states are generated by quenchers. Therefore, the generation of excited states is prevented. It is possible to provide a light emitting element that emits light. It is also possible to provide a light emitting element with high luminous efficiency. Therefore, a light-emitting element with high light-emitting properties can be provided.

[0081] Another example of the light-emitting element of one embodiment of the present invention will be described below.

[0082] The light-emitting element shown in FIG. 1C has a first electrode 101 and a first light-emitting layer 203x. a hole injection layer 201 provided on the electrode 101; and a transport layer 202. In addition, between the third light-emitting layer 203z and the second electrode 105, The electron transport layer 204 is provided on the third light-emitting layer 203z. The first light-emitting layer 203x and the second light-emitting layer 203 The third light-emitting layer 203y and the third light-emitting layer 203z may have the same structure as that shown in FIG. 1(B).

[0083] The light-emitting element shown in FIG. 1D includes a first electrode 101 and an E an L layer 103, a charge generation region 107 provided on the EL layer 103, and a charge generation region 107 The EL layer 103 has the same structure as that shown in FIG. It is completed.

[0084] As in the light-emitting element shown in FIG. 1E, a plurality of light-emitting elements are provided between the first electrode 101 and the second electrode 105. In this case, a charge generating region may be provided between the stacked EL layers. It is preferable to provide 107.

[0085] The light-emitting element shown in FIG. 1E includes a first electrode 101 and an E The L layer 103a, the charge generation region 107 provided on the EL layer 103a, and the charge generation region 1 EL layer 103b provided on the first electrode 107, and a second electrode 105 provided on the first electrode 103b. At least one of the EL layer 103a and the EL layer 103b has the same structure as that shown in FIG. It is a similar configuration.

[0086] Electrons and positive charges in the charge generating region 107 provided between the EL layer 103a and the EL layer 103b The behavior of the hole will be explained. When a voltage higher than the threshold voltage is applied, holes and electrons are generated in the charge generation region 107, and the positive The holes move to the EL layer 103b provided on the second electrode 105 side, and the electrons move to the first electrode 101 The holes injected into the EL layer 103b move to the EL layer 103a provided on the side. The luminescent material contained in the EL layer 103b recombines with the electrons injected from the electrode 105 side. The electrons injected into the EL layer 103a are injected from the first electrode 101 side. The charge generation recombines with the electron holes, causing the light-emitting material contained in the EL layer 103a to emit light. The holes and electrons generated in the raw region 107 each lead to light emission in a different EL layer. .

[0087] By providing the EL layers in contact with each other, the same structure as the charge generation region is formed between them. In this case, the EL layers can be provided in contact with each other without the charge generation region 107 in between. For example, when a charge generating region is formed on one side of an EL layer, an EL layer is provided in contact with that side. It can be done.

[0088] The structure of the layer provided between the first electrode 101 and the second electrode 105 is the same as that described above. However, it is not limited to the above. The first electrode 101 and the second electrode 10 A preferred configuration is one in which a light-emitting region where holes and electrons recombine is provided at a location away from 5 .

[0089] The hole transport layer and electron transport layer in contact with the light emitting layer 203 are also used to transport electrons from excitons generated in the light emitting layer. In order to suppress the energy transfer, the triplet excitation energy is effectively transferred to the material that constitutes the light-emitting layer. It is preferable that the compound be made of a substance having a triplet excitation energy higher than that of the compound.

[0090] <Light-emitting element materials> Examples of materials that can be used for each layer are shown below. Each layer other than the light-emitting layer is The film may have a single layer structure or a laminated structure of two or more layers.

[0091] <anode> The electrode that functions as the anode is made of one or more conductive metals, alloys, conductive compounds, etc. In particular, it is possible to form a semiconductor layer using a material with a large work function (4.0 eV or more). For example, indium tin oxide (ITO) is preferably used. xide), indium tin oxide containing silicon or silicon oxide, indium zinc oxide Indium oxide containing tungsten oxide and zinc oxide, graphene, gold, platinum , nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, titanium Nitrides of metal materials (for example, titanium nitride) and the like can also be used. Aluminum, titanium, etc. are formed into nanowires (or lines or thin wires), and conductive Forming a substance (such as conductive organic material or graphene) by coating or printing methods The electrodes may be formed by

[0092] When the anode is in contact with the charge generating region, various conductive materials can be used without considering the magnitude of the work function. For example, aluminum, silver, and alloys containing aluminum can be used. You can be there.

[0093] <cathode> The electrode that functions as the cathode is made of one or more conductive metals, alloys, conductive compounds, etc. It can be formed by using several materials. In particular, it is preferable to use materials with a small work function (3.8 eV or less). For example, it is preferable to use an element belonging to Group 1 or Group 2 of the periodic table (e.g., lithium). Alkali metals such as tium and cesium, and alkaline earth metals such as calcium and strontium , magnesium, etc.), alloys containing these elements (e.g., Mg-Ag, Al-Li), Rare earth metals such as rhodium and ytterbium, alloys containing these rare earth metals, and aluminum , silver, etc. can be used.

[0094] When the cathode is in contact with the charge generating region, various conductive materials can be used without considering the magnitude of the work function. For example, ITO, indium containing silicon or silicon oxide, Tin oxide and the like can also be used.

[0095] The electrodes may be formed by vacuum deposition or sputtering. When paste or the like is used, a coating method or an ink jet method may be used.

[0096] The emitted light is emitted to the outside through either or both of the first electrode 101 and the second electrode 105. Therefore, either the first electrode 101 or the second electrode 105 or both When only the first electrode 101 is a light-transmitting electrode, light is emitted through the first electrode 101. The light is extracted through the first electrode 101. Only the second electrode 105 has light-transmitting properties. When the first electrode 101 and the second electrode 105 are connected, the emitted light is extracted through the second electrode 105. When both the first electrode 101 and the second electrode 105 are light-transmitting electrodes, light is emitted from the first electrode 101 and the second electrode 105. The light is extracted from both sides through the second electrode 105. It is preferable to use a light-reflecting material.

[0097] In addition, an insulating film such as an organic film, a transparent semiconductor film, or a silicon nitride film is formed on the cathode (or upper electrode). These films serve as passivation films and act as a light-emitting element. It is possible to suppress the penetration of impurities and moisture into the cathode. This can reduce the loss of light energy due to the

[0098] <Light-emitting layer> As described above, the light-emitting element of the present embodiment has three types of light-emitting layers, and each light-emitting layer is a phosphorescent layer. The compound includes a host material.

[0099] The phosphorescent compound can be considered as a guest material in each light-emitting layer. The material can be called a host material. Each light-emitting layer can also contain materials other than guest materials and host materials. In the present specification, the compound contained in the light-emitting layer in the largest proportion is referred to as the compound that is contained in the light-emitting layer in the largest proportion. The compound serves as a host material in the light-emitting layer.

[0100] In the light-emitting layer, the guest material is dispersed in the host material, Crystallization can be suppressed. In addition, concentration quenching due to high concentration of guest material can be suppressed. As the host material, an electron transport material as described later can be used. A hole transporting compound or a hole transporting compound can be used.

[0101] The T1 level (three The level of the singlet excitation energy is preferably higher than the T1 level of the guest material. If the T1 level of the host material is lower than that of the guest material, the triplet of the guest material that contributes to light emission The host material quenches the doublet excitation energy, resulting in a decrease in luminous efficiency. This is because.

[0102] As for phosphorescent compounds that emit blue light, those with an emission peak between 440 nm and 520 nm are Specifically, compounds having the formula tris{2-[5-(2-methylphenyl)- 4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN 2]phenyl-κC}iridium(III) (abbreviation: [Ir(mpptz-dmp)3] ), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)yl Ir(Mptz)3, tris[4-(3-biphenyl)-5 -isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III ) (abbreviation: Ir(iPrptz-3b)3) organometallic iridium complexes and tris[3-methyl-1-(2-methylphenyl)-5-phenyl] Iridium(III) (abbreviation: Ir(Mptz) 1-mp)3), tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4 -triazolato)iridium(III) (abbreviation: Ir(PrPrptz1-Me)3) Organometallic iridium complexes with a 1H-triazole skeleton and fac-tris[1-( 2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium( III) (abbreviation: Ir(iPrpmi)3), tris[3-(2,6-dimethylphenyl )-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation Organometallic iridium compounds with an imidazole skeleton, such as Ir(dmpimpt-Me)3 dium complexes and bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ] Iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FIr6), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]Iridium (I II) Picolinate (abbreviation: FIrpic), bis{2-[3',5'-bis(trifluoromethyl)methyl] (Oromethyl)phenyl]pyridinato-N,C 2’}Iridium(III) picolinate( Abbreviation: Ir(CF3ppy)2(pic)), bis[2-(4',6'-difluorophenyl) Nyl)pyridinato-N,C 2’ ]Iridium(III) acetylacetonate (abbreviation: F Organic compounds using phenylpyridine derivatives with electron-withdrawing groups as ligands, such as Iracac Metal iridium complexes are included.

[0103] Among the above, organometallic iridium complexes with a 4H-triazole skeleton have excellent reliability and This is particularly preferable because of its excellent luminous efficiency.

[0104] Polyazo compounds such as 4H-triazole, 1H-triazole, and imidazole Organometallic iridium complexes with a tetrahedral skeleton have a high hole trapping property. These compounds are used as phosphorescent compounds that emit blue light in the light-emitting element of one embodiment of the present invention. When the blue light-emitting layer is disposed closer to the cathode than the red and green light-emitting layers, Holes pass through the blue light-emitting layer, reducing the luminous efficiency (or reducing the luminous efficiency over time). This is preferable because it can suppress the above.

[0105] As for phosphorescent compounds that emit green light, those with emission peaks between 520 nm and 600 nm are Specifically, tris(4-methyl-6-phenylpyrimidinyl) Iridium(III) (abbreviation: [Ir(mppm)3]), tris(4-t-butyl -6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)3 ]), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium Ir(III) (abbreviation: [Ir(mppm)2(acac)]), (acetylacetonate) Bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation :[Ir(tBuppm)2(acac)]), (acetylacetonato)bis[4-(2 -norbornyl)-6-phenylpyrimidinato]iridium(III)(endo-,e xo-mixture) (abbreviation: [Ir(nbppm)2(acac)]), (acetylacetonate bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]yl Ir(mpmppm)2(acac) Iridium(III) (abbreviation: [Ir Organometallic iridium complexes with pyrimidine skeletons, such as (dppm)2(acac)] (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)yl Ir(mppr-Me)2(acac) (abbreviation: [Ir(mppr-Me)2(acac)]), (acetylated Cetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium (III) (abbreviation: [Ir(mppr-iPr)2(acac)]) Organometallic iridium complexes and tris(2-phenylpyridinato-N,C2’ ) Iridium(III) (abbreviation: [Ir(ppy)3]), bis(2-phenylpyridinato -N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(ppy)2 (acac)]), bis(benzo[h]quinolinato)iridium(III) acetylacetonate Tonanate (abbreviation: [Ir(bzq)2(acac)]), tris(benzo[h]quinolinone Iridium(III) (abbreviation: [Ir(bzq)3]), tris(2-phenylquinoline) Rinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(pq)3]), bis(2- Phenylquinolinato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: Organometallic iridium complexes with pyridine skeletons, such as [Ir(pq)2(acac)] In addition to the body, tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac)3(Phen)])

[0106] Among the above, organometallic iridium complexes with pyrimidine skeletons have excellent reliability and luminous efficiency. is particularly preferable because it is remarkably excellent.

[0107] Among the above, organometallic compounds having a diazine skeleton such as a pyrimidine skeleton or a pyrazine skeleton Iridium complexes have weak hole trapping properties and strong electron trapping properties. The compound is used as a phosphorescent compound that emits green light in a light-emitting element of one embodiment of the present invention. In addition, when the green light-emitting layer is provided closer to the anode than the red and blue light-emitting layers, It is easy to transport holes to the red and blue light-emitting layers, and electrons pass through the green light-emitting layer to emit light. This is preferable because it can prevent the efficiency from decreasing (or the luminous efficiency from decreasing over time).

[0108] As for phosphorescent compounds that emit red light, those with emission peaks between 600 nm and 750 nm are Specifically, (diisobutyrylmethanato)bis[4,6-bis(4,6-diisobutyrylmethanato) ... [Ir(5md ppm)2(dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinato ](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(5mdppm)2( dpm)]), bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloy) Iridium(III) (abbreviation: [Ir(d1npm)2(dpm)]) Organometallic iridium complexes with pyrimidine skeletons such as (acetylacetonato)bis( 2,3,5-triphenylpyrazinate)iridium(III) (abbreviation: [Ir(tppr )2(acac)]), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethyl Thanato)iridium(III) (abbreviation: [Ir(tppr)2(dpm)]), (acetyl quinoxalinato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium Ir(Fdpq)2(acac)] Organometallic iridium complexes and tris(1-phenylisoquinolinato-N,C 2’ )stomach Lithium(III) (abbreviation: [Ir(piq)3]), bis(1-phenylisoquinolinone) To-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(piq) In addition to organometallic iridium complexes with pyridine skeletons such as 2(acac)], 2,3 ,7,8,12,13,17,18-Octaethyl-21H,23H-porphyrin platinum (II) (abbreviation: PtOEP), and tris(1,3-diphenyl-1, 3-propanedionato)(monophenanthroline)europium(III) (abbreviation: [E u(DBM)3(Phen)]), tris[1-(2-thenoyl)-3,3,3-triphenylphosphine [Eu( Examples include rare earth metal complexes such as TTA)3(Phen)]).

[0109] Among the above, organometallic iridium complexes with pyrimidine skeletons have excellent reliability and luminous efficiency. In addition, organometallic iridium compounds having a pyrazine skeleton are particularly preferred. The complex emits red light with good chromaticity, and when applied to white light-emitting devices, it improves color rendering. It is possible.

[0110] Among the above, organometallic compounds having a diazine skeleton such as a pyrimidine skeleton or a pyrazine skeleton Iridium complexes have weak hole trapping properties and strong electron trapping properties. An organometallic iridium complex having an iridium skeleton is used as a phosphorescent compound that emits red light. In addition, when the red light-emitting layer is provided closer to the anode than the blue light-emitting layer, holes are transported to the blue light-emitting layer. In addition, electrons pass through the red light-emitting layer, reducing the luminous efficiency (or the luminous efficiency decreases over time). This is preferable because it can prevent the decrease in efficiency.

[0111] In place of the phosphorescent compound, a material exhibiting thermally activated delayed fluorescence, i.e., thermally activated delayed fluorescence (TADF) materials may also be used. Here, delayed fluorescence is a material with the same spectrum as normal fluorescence. Its lifetime is approximately 10 -6 seconds or more, preferably is 10 -3 The thermally activated delayed fluorescent material is specifically fullerene and its derivatives, acridine derivatives such as proflavine, eosin, etc. Mg, Zinc (Zn), Cadmium (Cd), Tin (Sn), Platinum (Pt), In Examples include metal-containing porphyrins containing indium (In) or palladium (Pd). The metal-containing porphyrin may be, for example, a protoporphyrin-tin fluoride complex ( abbreviation: SnF2(Proto IX)), mesoporphyrin-tin fluoride complex (abbreviation: S nF2(Meso IX)), hematoporphyrin-tin fluoride complex (abbreviated as SnF2( Hemato IX), coproporphyrin tetramethyl ester-tin fluoride complex ( Abbreviation: SnF2(Copro III-4Me)), Octaethylporphyrin-Fluoride Tin complex (abbreviation: SnF2(OEP)), etioporphyrin-tin fluoride complex (abbreviation: SnF2(Etio I)), octaethylporphyrin-platinum chloride complex (abbreviated as PtC 12(OEP)) and the like. Furthermore, 2-(biphenyl-4-yl)-4,6-biphenyl bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5- π-electron rich heteroaromatic rings such as triazine (abbreviation: PIC-TRZ) and π-electron deficient heteroaromatic rings A heterocyclic compound having an aromatic ring can also be used. The materials in which the π-electron-deficient heteroaromatic ring is directly bonded to the π-electron-rich heteroaromatic ring exhibit the donor property and π The acceptor properties of the electron-deficient heteroaromatic rings become stronger, and the S1 level (singlet excitation energy This is particularly preferable because the difference between the T1 level and the T2 level becomes small.

[0112] Examples of the electron transporting compound include π-electron deficient heteroaromatic compounds such as nitrogen-containing heteroaromatic compounds. Aromatic compounds, metal complexes having a quinoline or benzoquinoline skeleton, oxazole and metal complexes having a thiazole-based ligand or a thiazole-based ligand.

[0113] Specifically, for example, bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation Name: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato) Aluminum (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Zn q), bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn( BOX) 2), bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation: Metal complexes such as Zn(BTZ)2), 2-(4-biphenylyl)-5-(4-tert- butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenyl)- (4-tert-butylphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-thiazolinone 1,3-bis[5-(p-tert-butylphenyl)-1, 3,4-Oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5 -phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazol (abbreviation: CO11), 2,2',2''-(1,3,5-benzenetriyl)tris( 1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzo Thiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: Heterocyclic compounds with polyazole skeletons such as mDBTBIm-II, 2-[3-(diphenyl 2-imidazoline) benzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2m DBTPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl- 3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2 -[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[ f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophene (4-phenyl)dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDB q-II), and 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f ,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 2-[3'-(9H-carba [f,h]quinoxaline (abbreviation: 2 mCzBPDBq) and other heterocyclic compounds having a quinoxaline skeleton or a dibenzoquinoxaline skeleton. The ring compound, 4,6-bis[3-(phenanthrene-9-yl)phenyl]pyrimidine (abbreviation Name: 4,6mPnP2Pm), 4,6-bis[3-(9H-carbazol-9-yl)phenyl] phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm), 4,6-bis[3-(4-diphenyl)pyrimidine Diazolidinyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II) Heterocyclic compounds with a pyrimidine skeleton (pyrimidine skeleton or pyrazine skeleton), 3,5-bis[3- (9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 3,5DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), 3,3',5,5'-tetra[(m-pyridyl)-phen-3-yl]biphenyl (abbreviation Among the above, heterocyclic compounds having a pyridine skeleton such as BP4mPy can be mentioned. Heterocyclic compounds having a quinoxaline skeleton or a dibenzoquinoxaline skeleton, diazines ( Heterocyclic compounds with pyrimidine or pyrazine skeletons, heterocyclic compounds with pyridine skeletons In particular, heterocyclic compounds having a diazine skeleton are preferred because they have good reliability. It has high transmission properties and also contributes to reducing driving voltage.

[0114] Furthermore, tris(8-quinolinolato)aluminum (abbreviation: Alq), tris(4-methyl quinoline skeleton or benzophenone such as (8-quinolinolato)aluminum (abbreviation: Almq3) Metal complexes with a benzoquinoline skeleton, bathophenanthroline (abbreviated as BPhen), Cuproine (abbreviation: BCP), 3-(4-tert-butylphenyl)-4-(4-ethylhexyl) pE tTAZ), 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene ( Examples of heteroaromatic compounds include poly(2,5-pyridinediamine) and poly(2,5-pyridinediamine). yl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)- co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), poly[(9,9-dioctadecyl) (2,2'-bipyridine-6,6'-diyl)-co-(2,2'-bipyridine-2,7-diyl) )] (abbreviation: PF-BPy) and other polymer compounds.

[0115] Also, 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazo CzPA, 9-phenyl-3-[4-(10-phenyl-9-anthryl )phenyl]-9H-carbazole (abbreviation: PCzPA), 3,6-diphenyl-9-[ 4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: DP CzPA), 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DP PA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 2-tert- Butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA) Compounds that have transport properties but also have a tendency to accept holes can also be suitably used. In one embodiment of the light-emitting element, a hole-trapping fluorescent compound that emits blue light is dispersed. When an electron transporting compound has an anthracene skeleton, it not only has electron transporting properties but also hole transporting properties. It is also preferable because it is easy to receive.

[0116] Examples of the hole transporting compound include compounds having an aromatic amine skeleton, carbazole skeleton, and the like. compounds having a thiophene skeleton, compounds having a furan skeleton, etc. In particular, π-electron-rich heteroaromatic compounds are preferred. Compounds having a carbazole skeleton and compounds having a carbazole skeleton have good reliability and are good hole transporters. This is preferable because it has high transmission properties and contributes to reducing the driving voltage.

[0117] Specifically, 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl) PCBA1BP, 4,4'-diphenyl-4''-(9-phenyl- (phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP) ), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl) Triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-( 9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNB) B), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol- (3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), N-phenyl -N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9, 9'-Bifluoren-2-amine (abbreviation: PCBASF), 3-[N-(1-naphthyl) -N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole ( Abbreviation: PCzPCN1), 4,4',4''-tris[N-(1-naphthyl)-N-phenyl] Nylamino]triphenylamine (abbreviation: 1'-TNATA), 2,7-bis[N-(4 -diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPA2SF), N,N'-bis(9-phenylcarbazol-3-yl)-N ,N'-Diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N-(9,9- Dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine (abbreviation) N,N',N''-triphenyl-N,N',N''-tris(9-phenyl- (phenylcarbazol-3-yl)benzene-1,3,5-triamine (abbreviation: PCA3B ), 2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro -9,9'-bifluorene (abbreviation: PCASF), 2-[N-(4-diphenylamino) (phenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPASF) , N,N'-bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl -9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F), N,N'-bi (3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4 '-diamine (abbreviation: TPD), 4,4'-bis[N-(4-diphenylaminophenyl )-N-phenylamino]biphenyl (abbreviation: DPAB), N-(9,9-dimethyl-9 H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'- (9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluorene-7- 3-[N-(9-phenylcarbazol-1-yl)phenylamine (abbreviation: DFLADFL), [N-3-yl]-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPC A1), 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenyla 3-[N-(4-diphenylamino)-9-phenylcarbazole (abbreviation: PCzPCA2) N-phenylaminophenyl)-9-phenylcarbazole (abbreviation: PC zDPA1), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenyla 4,4'-bis(N-[(amino)-9-phenylcarbazole (abbreviation: PCzDPA2) 4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenyl (amino)biphenyl (abbreviation: DNTPD), 3,6-bis[N-(4-diphenylamino)biphenyl [1-naphthylamino]-9-phenylcarbazole (abbreviation: PC zTPN2) etc.

[0118] Furthermore, 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation Name: NPB or α-NPD), 4,4',4''-tris(N,N-diphenylamino) Triphenylamine (abbreviation: TDATA), 4,4',4''-tris[N-(3-methyl (triphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), 4, 4'-Bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino] ]biphenyl (abbreviation: BSPB), 4,4',4''-tris(N-carbazolyl)triphenyl Phenylamine (abbreviation: TCTA), 4-phenyl-4'-(9-phenylfluorene- 9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-yl)triphenylamine mBPAFLP), 4,4'-phenylfluoren-9-yltriphenylamine -Bis[N-(9,9-dimethylfluoren-2-yl)-N-phenylamino]biphenyl Aromatic amine compounds such as 1,3-bis(N-carbamoyl) 4,4'-di(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole CzTP, 3,3'-bis(9-phenyl-9H-carbazole) PCCP), CzPA, PCzPA, and other carbazole derivatives. (N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl] N-phenyl-N'-phenylamino}phenyl) methacrylamide (abbreviation: PTP DMA), poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl) Examples of suitable polymer compounds include poly(benzidine) (abbreviation: Poly-TPD).

[0119] Also, 4,4',4''-(1,3,5-benzenetriyl)tri(dibenzothiophene ) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H -fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III ), 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyl Compounds with a thiophene skeleton, such as dibenzothiophene (abbreviation: DBTFLP-IV) and 4,4',4''-(1,3,5-benzenetriyl)tri(dibenzofuran) ( Abbreviation: DBF3P-II), 4-{3-[3-(9-phenyl-9H-fluorene-9- (I)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II) Examples include compounds having a furan skeleton.

[0120] Here, in order to increase the efficiency of energy transfer from the host material to the guest material, intermolecular transfer Mechanisms known as the Förster mechanism (dipole-dipole interaction) and the Dexter mechanism Considering the structure (electron exchange interaction), the emission spectrum of the host material (singlet excited state When discussing energy transfer from the fluorescence spectrum, energy from the triplet excited state The phosphorescence spectrum when discussing migration) and the absorption spectrum of the guest material (more specifically, The overlap with the spectrum in the absorption band on the long wavelength (low energy) side becomes large. is preferred.

[0121] However, the fluorescence spectrum of the host material is usually determined by the longest wavelength (low energy) of the guest material. It is difficult to superimpose the absorption spectrum on the absorption band on the (high) side. In this case, the phosphorescence spectrum of the host material will be longer wavelength (low energy) than the fluorescence spectrum. Since the T1 level of the host material is lower than that of the guest material, This is because the quench problem described above occurs. To avoid this, the T1 level of the host material is designed to be higher than the T1 level of the guest material. This time, the fluorescence spectrum of the host material shifts to the short wavelength (high energy) side, The fluorescence spectrum is the absorption spectrum in the longest wavelength (lowest energy) absorption band of the guest material. Therefore, the fluorescence spectrum of the host material is the most closely related to the guest material. The absorption spectrum of the host material is superimposed on the absorption band on the long wavelength (low energy) side. Maximizing energy transfer from excited states is usually difficult.

[0122] Thus, the light-emitting layer of the light-emitting element of one embodiment of the present invention contains, in addition to the phosphorescent compound and the host material, The host material and the carrier transport compound are exciplexes (exciplexes). In this case, it is preferable that the light-emitting layer is a combination that forms a complex. When carriers (electrons and holes) recombine in the host material and the carrier transport compound, This forms an exciplex, which allows the emission spectrum and excitation spectrum of the host material to be The fluorescence spectrum of carrier transport compounds is closer to the emission spectrum of exciplexes located on the longer wavelength side. The emission spectrum of the exciplex and the absorption spectrum of the guest material are then If the host material and the carrier transporting compound are selected so that the overlap of It is possible to maximize the energy transfer from the excited state. Regarding the luminescence, it is believed that energy transfer occurs from the exciplex rather than from the host material. In one embodiment of the present invention in which such a structure is applied, the emission spectrum of the exciplex and the phosphorescent compound Energy transfer efficiency is improved by utilizing the overlap of the absorption spectrum with that of Therefore, a light-emitting device with high external quantum efficiency can be realized.

[0123] The host material and the carrier transporting compound may be any combination that generates an exciplex. For example, either the host material or the carrier transporting compound is an electron transporting compound. The electron transport compound and the hole transport compound may be a compound having a hole transporting property. Examples of the materials that can be used as the host material or the carrier transporting compound include the above-mentioned materials. The materials that can form the exciplex are not limited to the above-mentioned materials, and any combinations that can form the exciplex can be used. The emission spectrum of the exciplex overlaps with the absorption spectrum of the guest material, and the exciplex If the peak of the emission spectrum of the guest material is longer than the peak of the absorption spectrum of the guest material, That's fine.

[0124] The carrier balance is controlled by the mixture ratio of the host material and the carrier transport compound. Specifically, the ratio of the host material to the carrier transporting compound is preferably in the range of 1:9 to 9:1. It's nice.

[0125] The exciplex may also be formed at the interface between the two layers. When a layer containing a substance and a layer containing a hole transporting compound are stacked, an exciplex is formed near the interface. However, these two layers may be used as the light-emitting layer in the light-emitting element of one embodiment of the present invention. In this case, the phosphorescent compound may be added in the vicinity of the interface. It is sufficient that the additive is added to at least one of the two or both of the two.

[0126] <Hole transport layer> The hole transport layer 202 is a layer containing a substance with hole transport properties.

[0127] The hole transporting substance may be any substance that transports holes more efficiently than electrons. 0 -6 cm 2 It is preferable that the material has a hole mobility of 1 / Vs or more.

[0128] The hole transport layer 202 contains a hole transport compound exemplified as a material that can be used in the light emitting layer. The object can be applied.

[0129] Aromatic hydrocarbon compounds such as CzPA, t-BuDNA, DNA, and DPAnth are also used. You can be there.

[0130] <Electron transport layer> The electron transporting layer 204 is a layer containing a substance with an electron transporting property.

[0131] The electron transporting substance may be any substance that transports electrons more than holes, and in particular, 0 -6 cm 2 It is preferable that the material has an electron mobility of 1 / Vs or more.

[0132] The electron transport layer 204 may contain, for example, the electron transport material exemplified as a material that can be used in the light-emitting layer. A protective compound can be applied.

[0133] The electron transport layer is a stack of a first electron transport layer on the anode side and a second electron transport layer on the cathode side. In this case, the first electron transport layer in contact with the light-emitting layer located closest to the cathode may be a layer structure. Substances having an anthracene skeleton or anthracene and carbazole skeletons in the layer By using such a structure, deterioration is slow and the voltage caused by driving is low. A light-emitting element with a small increase in internal resistance (which can be said to be a small increase in internal resistance when driven) can be realized.

[0134] Generally, it is necessary to smooth the injection of electrons from the cathode to the light-emitting layer and to prevent the electrons from being injected over a high barrier. In order to suppress deterioration due to contact with the electrons and to lower the driving voltage, The LUMO levels of the electron transport layer material and the host material are designed to become shallower in stages. However, in the light-emitting element of one embodiment of the present invention, the anthracene used in the electron-transport layer Even if the LUMO level of a substance with a silicon skeleton is the deepest, degradation is largely suppressed. Of course, the LUMO level of the substance having the anthracene skeleton is The material is the same as the material of the electron injection layer, or the material between the electron injection layer material and the host material as described above. Degradation can be suppressed even at the LUMO level.

[0135] Examples of substances having an anthracene skeleton include CzPA, 7-[4-(10-phenyl [c,g]carbazole (abbreviation: cg DBCzPA), 4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzyl benzofuran (abbreviation: 2mDBFPPA-II), 6-[3-(9,10-diphenyl-2 -anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBn fPPA) can be suitably used.

[0136] When a substance having an anthracene skeleton is used for the first electron transport layer, the second electron transport layer is made of an organic The organic compound may be a substance having an electron transport property. In addition, the LUMO level of the organic compound contained in the second electron transport layer is higher than that of the organic compound used as the host material. From the viewpoint of driving voltage, it is preferable that the LUMO level is located deeper than the LUMO level of the material. In addition, aromatic hydrocarbons, which do not contain heterocycles and are composed only of aromatic condensed rings, are also known. When the element is used as the main material of the electron transport layer, it does not function as a light-emitting device. , a cathode or a single-layer electron transport layer in contact with the electron injection layer has an anthracene skeleton When using anthracene, electrons are transported from the cathode to the electron transport layer because anthracene is an aromatic hydrocarbon. Therefore, when a substance having an anthracene skeleton is used for the first electron transport layer, When using a second electron transport layer, a second electron transport layer is required on the cathode side of the first electron transport layer. The organic compound used in the layer is one that easily accepts electrons from the cathode and has an anthracene skeleton. The material must have a small electron injection barrier to the first electron transport layer. In order to easily accept electrons from the cathode, a π-electron deficient heteroaromatic compound is preferred. Heteroaromatic rings containing a pyridine skeleton, heteroaromatic rings containing a phthalazine skeleton, pyrimidine skeleton heteroaromatic rings containing a pyrazine skeleton, heteroaromatic rings containing a triazine skeleton, etc. Specific examples of these heteroaromatic rings include: For example, pyridine, pyrimidine, quinoline, quinoxaline, dibenzo[f,h]quinoxaline Examples of the skeleton include phosphorus skeletons, but the bipyridine skeleton is particularly useful. As the first electron transport layer, 2,2'-bipyridine and phenanthroline are preferable. In order to reduce the electron injection barrier to the second electron transport layer, the organic compound LUM O level is equal to or higher than that of the substance having an anthracene skeleton used in the first electron transport layer. It is preferable to make it shallower, but as mentioned above, it is preferable to make it deeper than the host material. .

[0137] Examples of organic compounds that can be used in the second electron transport layer include Alq, BAlq, and , BCP, BPhen, 2,9-bis(naphthalen-2-yl)-4,7-diphenyl- 1,10-phenanthroline (abbreviation: NBphen), BP4mPy, 2,2'-[2, 2'-bipyridine-5,6-diylbis(biphenyl-4,4'-diyl)]bisbenzo Oxazole (abbreviation: BOxP2BPy) and the like can be suitably used.

[0138] <Hole injection layer> The hole injection layer 201 is a layer containing a substance with hole injection properties.

[0139] Examples of the hole-injecting material include molybdenum oxide, titanium oxide, and vanadium oxide. Rhenium oxide, ruthenium oxide, chromium oxide, zirconium oxide, hafnium Metal oxides such as aluminum oxide, tantalum oxide, silver oxide, tungsten oxide, and manganese oxide Compounds such as nitroxides can be used.

[0140] In addition, phthalocyanine (abbreviated as HPc), copper(II) phthalocyanine (abbreviated as CuPc Phthalocyanine compounds such as

[0141] In addition, TDATA, MTDATA, DPAB, DNTPD, 1,3,5-tris[N-( 4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B) Aromatic amine compounds such as PCzPCA1, PCzPCA2, and PCzPCN1 can be used. This can be done.

[0142] In addition, polymer compounds such as PVK, PVTPA, PTPDMA, and Poly-TPD, poly( 3,4-ethylenedioxythiophene) / poly(styrenesulfonic acid) (PEDOT / P SS), polyaniline / poly(styrene sulfonic acid) (PAni / PSS), etc. A polymer compound having the above structure can be used.

[0143] The hole injection layer 201 may also be used as a charge generation region. When the charge generation region is the charge generation region, various conductive materials can be used for the anode without considering the work function. The materials constituting the charge generating region will be described later.

[0144] <Electron injection layer> The electron injection layer 205 is a layer containing a substance with electron injection properties.

[0145] Examples of electron-injecting materials include lithium, cesium, calcium, lithium oxide, Lithium carbonate, cesium carbonate, lithium fluoride, cesium fluoride, calcium fluoride, Alkali metals, alkaline earth metals, rare earth metals, or their compounds such as erbium fluoride Compounds (oxides, carbonates, halides, etc.) can be used.

[0146] The electron injection layer 205 may also serve as a charge generation region. When the charge generation region is a region where the cathode is electrically conductive, various conductive materials can be used for the cathode without considering the work function. The materials constituting the charge generating region will be described later.

[0147] <Charge generation region> The charge generation region constituting the hole injection layer or electron injection layer, or the charge generation region 107, is a region in which holes are generated. Even if an electron acceptor is added to a transporting substance, the electron transporting The substance may have a structure in which an electron donor (donor) is added. The composition may be laminated.

[0148] As a hole transporting substance or an electron transporting substance that can be used in the light emitting layer, Examples of the hole transporting compounds and electron transporting compounds include the above-mentioned compounds.

[0149] The electron acceptor is 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroethylene. Examples include fluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, etc. Further, transition metal oxides can be mentioned. Examples of oxides of metals belonging to the group include vanadium oxide, niobium oxide, Tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, lenium oxide Molybdenum oxide is particularly stable in the atmosphere. It is preferable because it has low hygroscopicity and is easy to handle.

[0150] The electron donor may be an alkali metal, an alkaline earth metal, a rare earth metal, or a peripheral element. Metals belonging to Group 13 of the periodic table and their oxides and carbonates can be used. Generally, lithium, cesium, magnesium, calcium, ytterbium, and indium It is preferable to use lithium oxide, cesium carbonate, etc. Organic compounds such as amines may also be used as electron donors.

[0151] The layers constituting the EL layer 103 and the charge generating region 107 are formed by evaporation. (including vacuum deposition), transfer method, printing method, inkjet method, coating method, etc. It is possible.

[0152] The light emitting element in this embodiment mode can be fabricated on a substrate made of glass, plastic, or the like. The order of fabrication on the substrate may be from the first electrode 101 side onwards, or from the second electrode 102 side onwards. The light emitting device may be formed by forming one light emitting element on one substrate. A single light emitting element may be formed on one substrate, or a plurality of light emitting elements may be formed on one substrate. By manufacturing multiple elements, it is possible to manufacture lighting devices with separate elements or passive matrix light-emitting devices. Also, a thin film transistor, for example, can be formed on a substrate made of glass, plastic, or the like. A thin-film transistor (TFT) is formed, and a light-emitting element is fabricated on the electrode electrically connected to the TFT. This allows for an active matrix type display in which the driving of light emitting elements is controlled by TFTs. The structure of the TFT is not particularly limited. The crystallinity of the semiconductor used in the TFT is There are no particular limitations on the material, and either an amorphous semiconductor or a crystalline semiconductor may be used. The driving circuit formed on the TFT substrate is also made up of N-type and P-type TFTs. Alternatively, the TFT may be composed of only one of N-type TFTs or P-type TFTs. It is also possible.

[0153] 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.

[0154] As described above, the light-emitting element of one embodiment of the present invention has high emission efficiency. The optical element has a long life and high reliability. Furthermore, the light-emitting element of one embodiment of the present invention can be a tandem type. Since the layers are different, the manufacturing process is not complicated and the power loss due to the intermediate layer is small. It is also highly useful as a white light emitting element.

[0155] This embodiment mode can be freely combined with other embodiment modes.

[0156] (Embodiment 2) In this embodiment, a light-emitting device of one embodiment of the present invention will be described with reference to FIGS. The light-emitting device of this embodiment includes a light-emitting element according to one embodiment of the present invention. Therefore, a highly reliable light emitting device can be realized.

[0157] FIG. 4A is a plan view illustrating a light-emitting device according to one embodiment of the present invention, and FIG. 4B is a plan view illustrating a light-emitting device according to one embodiment of the present invention. ) is a cross-sectional view taken along dashed line AB.

[0158] The light emitting device of this embodiment is surrounded by a support substrate 401, a sealing substrate 405, and a sealing material 407. The light emitting element 403 is provided in the space 415. The light emitting element 403 has a bottom emission structure. Specifically, a first electrode 42 that transmits visible light is formed on a support substrate 401. 1, an EL layer 423 on the first electrode 421, and a second electrode 42 on the EL layer 423. The light-emitting element 403 is a light-emitting element to which one embodiment of the present invention described in Embodiment 1 is applied. The sealing substrate 405 has a desiccant 418 on the light emitting element 403 side.

[0159] The first terminal 409a is electrically connected to the auxiliary wiring 417 and the first electrode 421. An insulating layer 419 is provided on the electrode 421 in a region overlapping with the auxiliary wiring 417 . The first terminal 409a and the second electrode 425 are electrically insulated by an insulating layer 419. The second terminal 409b is electrically connected to the second electrode 425. 4 shows a configuration in which the first electrode 421 is formed on the auxiliary wiring 417. An auxiliary wiring 417 may be formed on the wiring 421 .

[0160] It is preferable to have a light extraction structure 411a at the interface between the support substrate 401 and the atmosphere. By providing a light extraction structure 411a at the interface between the support substrate 401 and the light source 402, the light is not emitted to the atmosphere due to the influence of total reflection. This reduces the amount of light that cannot be extracted, thereby improving the light extraction efficiency of the light emitting device.

[0161] In addition, a light extraction structure 411b is provided at the interface between the light emitting element 403 and the support substrate 401. When the light extraction structure 411b has unevenness, the light extraction structure 411b and the first It is preferable to provide a planarization layer 413 between the first electrodes 421. The electrode 421 can be a flat film, and the unevenness of the first electrode 421 in the EL layer 423 can be Furthermore, the occurrence of leakage current due to the above can be suppressed. Since the light extraction structure 411b is provided at the interface with 401, the light is extracted to the atmosphere due to the effect of total reflection. This reduces unwanted light and improves the light extraction efficiency of the light emitting device.

[0162] The planarization layer 413 has a surface in contact with the first electrode 421 rather than a surface in contact with the light extraction structure 411b. The planarizing layer 413 is made of a material that is light-transmitting and has a high refractive index. Glass, resin, etc. can be used.

[0163] FIG. 5A is a plan view illustrating a light-emitting device according to one embodiment of the present invention, and FIG. 5B is a plan view illustrating a light-emitting device according to one embodiment of the present invention. ) is a cross-sectional view taken along dashed line CD.

[0164] The active matrix light emitting device according to this embodiment has a light emitting section on a support substrate 501. 551, a drive circuit unit 552 (gate side drive circuit unit), a drive circuit unit 553 (source side drive circuit unit) The light emitting section 551 and the driving circuit sections 552 and 553 are supported by a support member. The substrate 501 is sealed in a space 515 formed by the sealing substrate 505 and the sealing material 507. .

[0165] FIG. 5B shows a light-emitting portion 551 manufactured by applying a color filter method.

[0166] The light emitting unit 551 includes a switching transistor 541a and a current control transistor 541b. 541b and the wiring (source electrode or drain electrode) of the transistor 541b. The light emitting element 520 is formed by a plurality of light emitting units each including a first electrode 521 connected to the light emitting element 520 .

[0167] The light emitting element 503 of the light emitting section 551 has a top emission structure, and the first electrode 5 21, an EL layer 523, and a second electrode 525 that transmits visible light. A partition wall 519 is formed to cover the edge of the first electrode 521 .

[0168] On the support substrate 501, external signals (video signals, clock signals) are supplied to the drive circuit sections 552 and 553. Connect the external input terminal that transmits signals such as a clock signal, start signal, or reset signal, or a potential. Here, an FPC 509 is provided as an external input terminal. This shows an example of providing a Flexible Printed Circuit (FPC).

[0169] The driver circuit portions 552 and 553 each include a plurality of transistors. Among the transistors included in the transistor 552, two transistors (transistor 542 and transistor The figure shows the resistor 543.

[0170] In order to prevent an increase in the number of processes, the lead wiring 517 is formed by connecting the electrodes and wiring used in the light emitting section and the drive circuit section. It is preferable to manufacture the lead wire from the same material and in the same process as the lead wire. The line 517 is connected to the source electrodes of the transistors included in the light emitting section 551 and the driving circuit section 552. This example shows a case where the gate electrode is fabricated using the same material and process as the drain electrode.

[0171] In FIG. 5B, the sealing material 507 is in contact with the first insulating layer 511 on the lead wiring 517. The sealing material 507 may have poor adhesion to metal. It is preferable that the insulating film 514 contacts the inorganic insulating film provided on the lead wiring 517. By adopting this configuration, it is possible to realize a light emitting device with high sealing and adhesion properties and high reliability. Inorganic insulating films include oxide films of metals and semiconductors, nitride films of metals and semiconductors, and Examples include semiconductor oxynitride films, specifically silicon oxide films, silicon nitride films, and oxynitride films. Examples of the film include a silicon nitride film, a silicon oxide nitride film, an aluminum oxide film, and a titanium oxide film. .

[0172] The first insulating layer 511 also serves to prevent impurities from diffusing into the semiconductor that constitutes the transistor. In addition, the second insulating layer 513 reduces surface irregularities caused by the transistor. Therefore, it is preferable to select an insulating film that has a planarizing function.

[0173] The sealing substrate 505 shown in FIG. 5B has a light-emitting element 503 (light-emitting region) overlapping therewith. A color filter 533, which is a colored layer, is provided at a position where it overlaps with the partition wall 519. A black matrix 531 is provided. Furthermore, a color filter 533 and a black matrix An overcoat layer 535 is provided over the trix 531 .

[0174] Examples of materials that can be used in the light-emitting device of one embodiment of the present invention will be described below.

[0175] [substrate] The substrate on the side where light from the light emitting element is extracted is made of a material that transmits the light. For example, glass Materials such as quartz, ceramic, sapphire, and organic resin can be used. A flexible material is used for the substrate of a flexible light emitting device.

[0176] Examples of glass include alkali-free glass, barium borosilicate glass, and aluminoboron glass. Silicate glass or the like can be used.

[0177] Examples of materials that are flexible and transparent to visible light include: Thick glass, polyethylene terephthalate (PET), polyethylene naphthalate ( Polyester resins such as PEN, polyacrylonitrile resins, polyimide resins, polymethyl methacrylate resin, polycarbonate (PC) resin, polyethersulfone (PES) ) resin, polyamide resin, cycloolefin resin, polystyrene resin, polyamide-imide Resin, polyvinyl chloride resin, etc. are examples. In particular, it is preferable to use a material with a low thermal expansion coefficient. For example, polyamide-imide resin, polyimide resin, PET, etc. are preferably used. In addition, substrates made of glass fiber impregnated with organic resin and inorganic fillers impregnated with organic resin can be used. It is also possible to use a substrate with a lower thermal expansion coefficient by mixing a material such as Because of its light weight, the light emitting device using the substrate can also be made light weight.

[0178] In addition, the substrate on the side from which light is not extracted does not need to be light-transmitting. In addition to the substrate, a metal substrate made of a metal material or an alloy material can also be used. The heat transfer efficiency of the encapsulation substrate is high, and the heat transfer efficiency of the encapsulation substrate is high. In order to obtain flexibility and bendability, it is preferable to use a metal The thickness of the substrate is preferably 10 μm or more and 200 μm or less, and more preferably 20 μm or more and 50 μm or less. It is more preferable to do so.

[0179] The material for forming the metal substrate is not particularly limited, but examples thereof include aluminum, copper, and nickel. It is preferable to use a metal alloy such as aluminum alloy or stainless steel. can be done.

[0180] In addition, insulating treatment is performed by oxidizing the surface of a conductive substrate or forming an insulating film on the surface. For example, a coating method such as spin coating or dipping may be used. The insulating film may be formed by electrodeposition, vapor deposition, sputtering, or the like. In addition to leaving it in the atmosphere or heating it, an oxide film is formed on the surface of the substrate by anodizing or other methods. You may do so.

[0181] As for the flexible substrate, a layer using the above material is used as a protective layer to protect the surface of the light emitting device from scratches. Hard coat layer (e.g., silicon nitride layer) or layer of material that can disperse pressure (e.g., The light-emitting element may be laminated with a layer of a luminescent material such as an aramid resin layer. In order to prevent the deterioration of the life of the silicon, the nitrogen and silicon nitride films such as silicon nitride films and silicon oxynitride films are used. Insulating films with low water permeability, such as films containing nitrogen and aluminum, or films containing nitrogen and aluminum, such as aluminum nitride films. It may have a velum.

[0182] The substrate may be formed by laminating a plurality of layers. In particular, when the substrate has a glass layer, This improves the barrier properties against water and oxygen, thereby making it possible to provide a highly reliable light-emitting device.

[0183] For example, a substrate having a glass layer, an adhesive layer, and an organic resin layer stacked from the side closer to the light emitting element is used. The thickness of the glass layer is 20 μm or more and 200 μm or less, preferably The thickness of the glass layer is 25 μm or more and 100 μm or less. A glass layer with such a thickness has high resistance to water and oxygen. The thickness of the organic resin layer is 10 μm or less. The thickness of the organic resin layer is set to 200 μm or less, preferably 20 μm or more and 50 μm or less. By placing it outside the glass layer, it is possible to suppress breakage and cracks in the glass layer and to prevent mechanical damage. The strength can be improved. When such a composite material of glass material and organic resin is applied to the substrate, By using this, a highly reliable and flexible light emitting device can be obtained.

[0184] [Insulating film] An insulating film may be formed between the support substrate and the light emitting element or between the support substrate and the transistor. The insulating film is made of inorganic materials such as silicon oxide, silicon nitride, silicon oxynitride, and silicon nitride oxide. It can be formed using an insulating material. In particular, it is possible to prevent moisture and the like from entering transistors and light-emitting elements. Therefore, insulating films with low water permeability such as silicon oxide film, silicon nitride film, and aluminum oxide film are used. It is preferable to use an insulating film that covers a transistor or a light-emitting element for the same purpose and with the same material. It may be provided.

[0185] [Light-emitting element] A light-emitting device according to one embodiment of the present invention includes one or more light-emitting elements described in Embodiment 1.

[0186] [Bulkhead] The partition wall can be made of an organic resin or an inorganic insulating material. , polyimide resin, polyamide resin, acrylic resin, siloxane resin, epoxy resin, or As the inorganic insulating material, phenol resin or the like can be used. Silicon nitride or the like can be used. Photosensitive resin is particularly preferred because it makes it easier to fabricate the partition walls. It is preferable to use

[0187] The method for forming the partition wall is not particularly limited, and may be, for example, a photolithography method, a sputtering method, or a vapor deposition method. method, droplet ejection method (inkjet method, etc.), printing method (screen printing, offset printing, etc.) etc. can be used.

[0188] [Auxiliary wiring] Although it is not necessary to provide auxiliary wiring, it is recommended to provide it in order to suppress the voltage drop caused by the resistance of the electrodes. Therefore, it is preferable to provide such a filter.

[0189] The materials for the auxiliary wiring are copper (Cu), titanium (Ti), tantalum (Ta), and tungsten (W ), molybdenum (Mo), chromium (Cr), neodymium (Nd), scandium (Sc), Nickel (Ni), or alloy materials containing these as the main components, The auxiliary wiring may be formed by laminating or by using aluminum. When aluminum is used, it will corrode if it is placed in direct contact with a transparent oxide conductive material. Therefore, to prevent corrosion, the auxiliary wiring is made to have a laminated structure and is connected to ITO, etc. It is preferable to use aluminum for the layer that is not covered by the auxiliary wiring. The thickness can be set to 0.1 μm or less, and preferably 0.1 μm or more and 0.5 μm or less.

[0190] When paste (such as silver paste) is used as the material for the auxiliary wiring, the metal that makes up the auxiliary wiring becomes granular. As a result, the surface of the auxiliary wiring becomes rough and has many gaps, and for example, Even if an auxiliary wiring is provided on the edge layer 419, it is difficult for the EL layer to completely cover the auxiliary wiring. This is preferable because it makes it easier to electrically connect the electrode and the auxiliary wiring.

[0191] [Sealing material] The sealing method of the light emitting device is not limited, and may be, for example, solid sealing or hollow sealing. For example, glass materials such as glass frit and two-component resins that harden at room temperature are Resin materials such as curable resin, photocurable resin, and thermosetting resin can be used. The device may be filled with an inert gas such as nitrogen or argon, and may be made of PVC (polyvinyl chloride). chloride) resin, acrylic resin, polyimide resin, epoxy resin, silicone resin, Resins such as PVB (polyvinyl butyral) resin and EVA (ethylene vinyl acetate) resin The resin may contain a desiccant.

[0192] [Light extraction structure] The light extraction structure includes a hemispherical lens, a microlens array, and a filter with a concave-convex structure. For example, the above-mentioned lens or film may be formed on a substrate. The substrate or the lens or film is bonded to the substrate using an adhesive or the like having a refractive index similar to that of the substrate or the lens or film. By bonding the film, a light extraction structure can be formed.

[0193] [Transistor] The light-emitting device of one embodiment of the present invention may include a transistor. The transistor is not limited to a specific type, and a top-gate transistor or a bottom-gate transistor such as an inverted staggered transistor may be used. Alternatively, an n-channel transistor may be used. A channel type transistor may be used. For example, oxide semiconductors such as silicon and In-Ga-Zn-based metal oxides can be used. The transistor used in the channel formation region can be applied.

[0194] This embodiment mode can be combined with other embodiment modes as appropriate.

[0195] (Embodiment 3) In this embodiment, a light-emitting device and a lighting device using a light-emitting device according to one embodiment of the present invention will be described. An example will be described with reference to FIGS.

[0196] The electronic devices of this embodiment include a light-emitting device according to one embodiment of the present invention in a display portion. The lighting device of this embodiment includes the light-emitting device of one embodiment of the present invention in a light-emitting portion (lighting portion). By using the light-emitting device of one embodiment, highly reliable electronic devices and lighting devices can be realized.

[0197] As an electronic device to which a light emitting device is applied, for example, a television set (television or television (also called television receivers), computer monitors, digital cameras, digital video Cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), mobile phones These include portable game machines, mobile information terminals, sound reproduction devices, and large game machines such as pachinko machines. Specific examples of these electronic devices and lighting devices are shown in FIGS.

[0198] FIG. 6A shows an example of a television device. The television device 7100 is A display unit 7102 is built into the body 7101. The display unit 7102 displays images. The light-emitting device to which one embodiment of the present invention is applied can be used for the display portion 7102. In addition, the configuration in which the housing 7101 is supported by a stand 7103 is shown here. are.

[0199] The television device 7100 can be operated using an operation switch on the housing 7101 or a separate remote control. This can be done by the remote control operation device 7111. This allows you to control the channel and volume, and the video displayed on the display unit 7102. In addition, the remote control operation device 7111 can be operated. A display unit may be provided to display information output from the

[0200] The television device 7100 includes a receiver, a modem, and the like. It is possible to receive more general television broadcasts, and also to receive them by wire or wirelessly via a modem. By connecting to a communication network, it can be transmitted in one direction (sender to receiver) or two directions (transmit to receiver). It is also possible to communicate information between followers and recipients, or between recipients themselves.

[0201] FIG. 6B shows an example of a computer. The computer 7200 includes a main body 720 1, a housing 7202, a display unit 7203, a keyboard 7204, an external connection port 7205, The computer includes an imaging device 7206 and the like. The device is manufactured by using it as the display portion 7203 .

[0202] FIG. 6C shows an example of a portable game machine. The portable game machine 7300 has a housing 7 It is composed of two housings, housing 7301a and housing 7301b, and the opening is connected by a connecting part 7302. The display unit 7303a is incorporated in the housing 7301a, and the housing 73 The display unit 7303b is incorporated in the portable game console 01b. The device includes a speaker section 7304, a recording medium insertion section 7305, operation keys 7306, and a connection terminal 73 07, Sensor 7308 (force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid , magnetic, temperature, chemical, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, (including functions to measure humidity, gradient, vibration, odor or infrared rays), LED lamp, Of course, the configuration of the portable game machine is not limited to the above. At least one of the display portion 7303a and the display portion 7303b may include a display device according to one embodiment of the present invention. It is sufficient to use a light emitting device, and other auxiliary equipment may be provided as appropriate. The portable game machine shown in FIG. 6(C) uses a program or data recorded on a recording medium. It also has the function of reading the information and displaying it on the display, as well as the function of sharing information with other portable game consoles via wireless communication. The functions of the portable game machine shown in FIG. 6(C) are not limited to these. It can have a variety of functions.

[0203] FIG. 6D shows an example of a mobile phone. A mobile phone 7400 is provided in a housing 7401. In addition to the built-in display unit 7402, operation buttons 7403, external connection port 7404, The mobile phone 7400 includes a speaker 7405, a microphone 7406, and the like. The light-emitting device of one embodiment of the above is used for the display portion 7402 .

[0204] In a mobile phone 7400 shown in FIG. 6D, information can be displayed by touching the display portion 7402 with a finger or the like. You can also make a call or write an email using the This can be done by touching the display portion 7402 with a finger or the like.

[0205] The screen of the display unit 7402 has three main modes. The first is a display mode that mainly displays images. The first mode is a display mode, and the second mode is an input mode that mainly inputs information such as characters. This is a display + input mode that combines two modes: display mode and input mode.

[0206] For example, when making a call or creating an email, the display unit 7402 is used to input characters. This is the main input mode, and you can input characters displayed on the screen.

[0207] In addition, the mobile phone 7400 includes sensors for detecting tilt, such as a gyro sensor and an acceleration sensor. By providing a detection device having a sensor, the orientation of the mobile phone 7400 (portrait or landscape) can be determined. In this way, the screen display on the display portion 7402 can be automatically switched.

[0208] The screen mode can be switched by touching the display portion 7402 or by operating the housing 7401. This is done by operating the button 7403. Also, depending on the type of image displayed on the display unit 7402, For example, if the image signal to be displayed on the display unit is a video signal, If it is data, the display mode is switched to, and if it is text data, the input mode is switched to.

[0209] In the input mode, the optical sensor of the display unit 7402 detects a signal and displays it. If there is no input by touch operation on the part 7402 for a certain period of time, the screen mode is changed to the input mode. Alternatively, the display mode may be switched from the normal mode to the display mode.

[0210] The display portion 7402 can also function as an image sensor. By touching the device with your palm or fingers and capturing an image of your palm print or fingerprint, you can authenticate your identity. In addition, a backlight that emits near-infrared light to the display unit or a sensing light source that emits near-infrared light By using this, it is possible to capture images of finger veins, palm veins, etc.

[0211] FIG. 6(E) shows an example of a foldable tablet terminal (open state). The tablet terminal 7500 includes a housing 7501a, a housing 7501b, a display unit 7502a, and a display The housing 7501a and the housing 7501b are connected by a shaft 7503. The housing 7501 can be opened and closed around the axis 7503. The a has a power supply 7504, operation keys 7505, a speaker 7506, etc. The portable terminal 7500 includes a light-emitting device according to one embodiment of the present invention in a display portion 7502a, a display portion 750b, and a display portion 750c. 2b or both.

[0212] At least a part of the display portion 7502a or the display portion 7502b is a touch panel area. By touching the displayed operation keys, data can be input. For example, The entire surface of the display unit 7502a is used as a touch panel by displaying keyboard buttons. 02b can be used as a display screen.

[0213] The indoor lighting device 7601, the roll-type lighting device 7602, and the tabletop lighting device shown in FIG. 7(A) The planar lighting device 7603 and the planar lighting device 7604 are lighting devices using the light-emitting device of one embodiment of the present invention. The light-emitting device of one embodiment of the present invention can be made large in area; It can be used as a lighting device. Also, because it is thin, it can be attached to a wall. This can be done.

[0214] The table lamp shown in FIG. 7B includes a lighting portion 7701, a support 7703, a support stand 7705, and the like. The lighting portion 7701 includes a light-emitting device according to one embodiment of the present invention. In the embodiment, the lighting device has a light-emitting portion having a curved surface, or a lighting device having a flexibly bendable lighting portion. In this way, a flexible light-emitting device can be used in a lighting device. This not only increases the degree of freedom in designing lighting devices, but also makes it possible to install lighting devices in, for example, automobile ceilings, This makes it possible to install the lighting device in a place with a curved surface such as a dashboard.

[0215] This embodiment mode can be combined with other embodiment modes as appropriate. [Example]

[0216] In this example, a light-emitting element of one embodiment of the present invention will be described with reference to FIG. The chemical formula of the material used is shown below:

[0217] [ka]

[0218] The light-emitting element of this example has three light-emitting layers. In the light-emitting element 1, green light is emitted from the anode side. In the comparative light-emitting element 2, a red light-emitting layer, a red light-emitting layer, and a blue light-emitting layer are stacked from the anode side. The light-emitting element 1 of this example and the comparative light-emitting element 2 are laminated. A method for fabricating comparative light emitting element 2 will be described.

[0219] (Light-emitting element 1) First, an indium tin oxide (ITSO) film containing silicon oxide was sputtered onto a glass substrate. The first electrode 1101 was formed by a deposition method. The thickness of the first electrode 1101 was 110 nm. The electrode area was set to 2 mm x 2 mm. Here, the first electrode 1101 was used as the anode of the light-emitting element. It is an electrode that functions as a

[0220] Next, as a pretreatment for forming a light-emitting element on the glass substrate, the substrate surface is washed with water. After baking at 200°C for 1 hour, UV ozone treatment was performed for 370 seconds.

[0221] Then, 10 -4 The glass substrate was placed in a vacuum deposition device whose interior had been decompressed to approximately 100 Pa. After vacuum baking at 170°C for 30 minutes in the heating chamber of the vacuum deposition equipment, the glass substrate It was left to cool for about 30 minutes.

[0222] Next, the surface on which the first electrode 1101 is formed is placed downward. The glass substrate was fixed to a substrate holder installed in a vacuum deposition apparatus, and -4 Pa After the pressure is reduced to about 4,4 ',4''-(1,3,5-benzenetriyl)tri(dibenzothiophene) (abbreviation: D The hole injection layer 1111 was formed by co-evaporating BT3P-II and molybdenum oxide (VI). The thickness of the film was 40 nm, and the ratio of DBT3P-II to molybdenum oxide was The ratio was adjusted to 2:1 (=DBT3P-II:molybdenum oxide). The evaporation method is a method in which evaporation is carried out simultaneously from a plurality of evaporation sources in one processing chamber.

[0223] Next, 4,4'-di(1-naphthyl)-4''-(9-phenyl)- (9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB) for 20 The hole transport layer 1112 was formed by depositing the film to a thickness of 1000 nm.

[0224] Furthermore, 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo 2mDBTBPDBq-II), 4,4'-di(1- naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenyl PCBNBB and (acetylacetonato)bis(6-tert-butyl- 4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)2( A first light-emitting layer, which is a green light-emitting layer, is formed on the hole transport layer 1112 by co-evaporating a first layer of a green light-emitting material (a layer of a luminescent layer containing ... The optical layer 1113a was formed. The film thickness was 20 nm. The weight ratio of CBNBB and [Ir(tBuppm)2(acac)] was 0.7:0.3: 0.05(=2mDBTBPDBq-II:PCBNBB:[Ir(tBuppm)2( The concentration was adjusted to be 0.05%.

[0225] Next, 2mDBTBPDBq-II, PCBNBB, and bis(2,3,5-triphenyl [Ir(tppr)](pyrazinato)(dipivaloylmethanato)iridium(III) )2(dpm)]) was co-deposited on the first light-emitting layer 1113a to form a red light-emitting layer. The second light-emitting layer 1113b was formed. Its thickness was 5 nm and it contained 2mDBTBPDBq-I The weight ratio of I, PCBNBB, and [Ir(tppr)2(dpm)] was 0.8:0.2: 0.05(=2mDBTBPDBq-II:PCBNBB:[Ir(tppr)2(dp The ratio was adjusted to be 1 / 2 m).

[0226] Next, 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviated :3,5DCzPPy), 9-phenyl-9H-3-(9-phenyl-9H-carbazole PCCP and tris{2-[5-(2-methylphenyl)-3-yl]carbazole (phenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazole-3- {Ir(mpptz-d mp)3]) was co-deposited on the second light-emitting layer 1113b to form a third blue light-emitting layer. The light-emitting layer 1113c was formed. Its thickness was 30 nm, and it contained 3,5DCzPPy, PCCP and [Ir(mpptz-dmp)3] in a weight ratio of 0.3:0.7:0.06 (=3, The mixture was adjusted to 5DCzPPy:PCCP:[Ir(mpptz-dmp)3] .

[0227] Next, 3,5DCzPPy was evaporated to a thickness of 10 nm, and then bathophenanthro Phosphorus (abbreviation: BPhen) was vapor deposited to a thickness of 20 nm to form a third light-emitting layer 1 An electron transport layer 1114 was formed on 113c.

[0228] Furthermore, lithium fluoride (LiF) was evaporated to a thickness of 1 nm, and the electron transport An electron injection layer 1115 was formed on the layer 1114 .

[0229] Finally, a second electrode 1103 functioning as a cathode was formed by depositing aluminum to a thickness of 200 nm. The vapor deposition was carried out so that

[0230] (Comparative light-emitting element 2) The comparative light-emitting element 2 has a light-emitting layer (a first light-emitting layer 1113a, a second light-emitting layer 1113b, and a The comparative light-emitting element 2 was fabricated in the same manner as the light-emitting element 1 except for the light-emitting layer 1113c). A method for producing the light-emitting layer will be described.

[0231] First, 2mDBTBPDBq-II, PCBNBB and [Ir(tppr)2(dpm) ] is co-deposited on the hole transport layer 1112 to form a first light-emitting layer 1113, which is a red light-emitting layer. The film thickness was 10 nm, and 2mDBTBPDBq-II, PCBNBB, and The weight ratio of [Ir(tppr)2(dpm)] to [Ir(tppr)2(dpm)] was 0.5:0.5:0.05 (=2mD BTBPDBq-II:PCBNBB:[Ir(tppr)2(dpm)] was adjusted to.

[0232] Next, 2mDBTBPDBq-II, PCBNBB, and [Ir(tBuppm)2(ac a) and b) are co-deposited on the first light-emitting layer 1113a to form a second light-emitting layer, which is a green light-emitting layer. The layer 1113b was formed with a thickness of 10 nm. The weight ratio of BNBB and [Ir(tBuppm)2(acac)] was 0.5:0.5:0. .05(=2mDBTBPDBq-II:PCBNBB:[Ir(tBuppm)2(a cac)]).

[0233] Then, 3,5DCzPPy, PCCP, and [Ir(mpptz-dmp)3] were co-evaporated. By this, a third light-emitting layer 1113c, which is a blue light-emitting layer, is formed on the second light-emitting layer 1113b. The film thickness was 30 nm and consisted of 3,5DCzPPy, PCCP, and [Ir(mppt The weight ratio of DCzPPy to PCz-dmp3 was 0.5:0.5:0.06 (=3,5DCzPPy:PCz-dmp3). CP: [Ir(mpptz-dmp)3]).

[0234] In the above-described deposition process, the deposition was all carried out by resistance heating.

[0235] The element structure of the light-emitting element of this example obtained as described above is shown in Table 1.

[0236] [Table 1]

[0237] The light-emitting element 1 and the comparative light-emitting element 2 were placed in a glove box with a nitrogen atmosphere. After sealing the device with a glass substrate to prevent it from being exposed to the atmosphere, The operating characteristics of the device were measured. The measurements were carried out at room temperature (an atmosphere maintained at 25°C). It was.

[0238] The luminance-current efficiency characteristics of the light-emitting element of this example are shown in FIG. 9. In FIG. 9, the horizontal axis represents the luminance (c d / m 2 The vertical axis represents the current efficiency (cd / A), and the voltage-luminance characteristics are shown in Figure 10. In Figure 10, the horizontal axis represents voltage (V) and the vertical axis represents luminance (cd / m 2 ) and also represents The luminance vs. external quantum efficiency characteristics are shown in Figure 11. In Figure 11, the horizontal axis represents the luminance (cd / m 2 )of, The vertical axis represents the external quantum efficiency (%). / m 2 Voltage (V), current density (mA / cm 2 ), CIE chromaticity coordinates (x, y), current Table 2 shows the efficiency (cd / A), power efficiency (lm / W), and external quantum efficiency (%).

[0239] [Table 2]

[0240] As described above, it was found that the light-emitting element 1 and the comparative light-emitting element 2 exhibited favorable element characteristics.

[0241] The emission spectrum of the light-emitting element of this example is shown in FIG. 12. In FIG. 12, the horizontal axis represents The vertical axis represents the wavelength (nm), and the vertical axis represents the luminous intensity (arbitrary unit). Brightness 1000 cd / m 2 Light emitted when The CIE chromaticity coordinates of element 1 were (x,y) = (0.46,0.46). Luminance 1000 cd / m 2 The CIE chromaticity coordinates of the comparative light-emitting element 2 are (x, y) = (0.44, 0.44 ) As shown in FIG. 12 and Table 2, the light-emitting device of this example had a luminance of [Ir(tppr)2 (dpm)] and green light from [Ir(tBuppm)2(acac)] The emission spectrum includes both blue light from [Ir(mpptz-dmp)3] and blue light from [Ir(mpptz-dmp)3]. It was found to show torque.

[0242] Next, reliability tests were performed on the light-emitting element 1 and the comparative light-emitting element 2. The results of the reliability tests are shown in FIG. In FIG. 13, the vertical axis indicates normalized luminance (%) when the initial luminance is 100%. The horizontal axis indicates the driving time (h) of the device. cd / m 2 The light emitting device of this example was driven under the condition of a constant current density. Although the light emitted from each light-emitting layer of the light-emitting element 1 is all phosphorescence, Even after a certain period of time, the device maintained 51% of its initial brightness, demonstrating that it is a highly durable device. On the other hand, the luminance of the comparative light-emitting element 2 after 370 hours was less than 50% of the initial luminance. The test results show that the light-emitting element 1 has a longer life than the comparative light-emitting element 2. It was.

[0243] In the comparative light-emitting element 2, the blue light-emitting layer and the green light-emitting layer are in contact with each other, so the [I A portion of the exciton energy in the triplet excited state of [r(mpptz-dmp)3] emits blue light. After transferring the energy to the quencher generated in the [Ir It is difficult to move to the triplet excited state of [(tBuppm)2(acac)]. In the optical element 1, the blue light-emitting layer and the red light-emitting layer are in contact with each other, so part of the energy of the excitons is transferred to the blue light-emitting layer. After being transferred to the quencher generated in the color-emitting layer, the energy is contained in the red-emitting layer. It is possible to transfer to the triplet excited state of [Ir(tppr)2(dpm)]. In the optical element 1, carrier recombination occurs in each light-emitting layer, and therefore, phosphorescence contained in each light-emitting layer Therefore, the light-emitting element 1 can emit light from each of the compounds. It is believed to have a longer lifespan than 2.

[0244] The results of this example show that the light-emitting element 1 of one embodiment of the present invention has good element characteristics and a long life. It was found that the light-emitting device has a long life and can obtain well-balanced light from the three guest materials. It was. [Example]

[0245] In this example, a light-emitting element of one embodiment of the present invention will be described with reference to FIG. The chemical formulas of the materials used are shown below. Materials already mentioned are omitted.

[0246] [ka]

[0247] The method for fabricating the light emitting device 3 of this example will be described below.

[0248] (Light-emitting element 3) First, similarly to the light-emitting element 1, a first electrode 1101 and a hole injection layer 1111 were formed on a glass substrate. Then, a hole transport layer 1112 was formed.

[0249] Next, 2mDBTBPDBq-II, PCBNBB, and [Ir(tBuppm)2(ac a) and b) are co-deposited on the hole transport layer 1112 to form a first light-emitting layer 1113, which is a green light-emitting layer. The film thickness was 20 nm, and 2mDBTBPDBq-II, PCBN The weight ratio of BB to [Ir(tBuppm)2(acac)] was 0.8:0.2:0.0 5(=2mDBTBPDBq-II:PCBNBB:[Ir(tBuppm)2(aca c)]).

[0250] Next, 2mDBTBPDBq-II, PCBNBB, and [Ir(tppr)2(dpm) ] is co-deposited on the first light-emitting layer 1113a, whereby the second light-emitting layer 1113a is a red light-emitting layer. The film thickness was 5 nm, and 2mDBTBPDBq-II, PCBNBB and [Ir(tppr)2(dpm)] in a weight ratio of 0.8:0.2:0.05 (=2m DBTBPDBq-II:PCBNBB:[Ir(tppr)2(dpm)]) I adjusted it to fit.

[0251] Next, 3,5DCzPPy, PCCP, and [Ir(mpptz-dmp)3] were co-evaporated. By this, a third light-emitting layer 1113c, which is a blue light-emitting layer, is formed on the second light-emitting layer 1113b. The film thickness was 30 nm, and the components were 3,5DCzPPy, PCCP, and [Ir(mpptz -dmp)3] weight ratio is 0.7:0.3:0.06 (=3,5DCzPPy:PCC P:[Ir(mpptz-dmp)3]).

[0252] Next, 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA) was evaporated to a thickness of 10 nm, and then BPhen was evaporated to a thickness of 15 nm. The electron transport layer 1114 is formed on the third light-emitting layer 1113c by vapor deposition so that the thickness of the third light-emitting layer 1113c becomes m. did.

[0253] Furthermore, lithium fluoride (LiF) was evaporated to a thickness of 1 nm, and the electron transport An electron injection layer 1115 was formed on the layer 1114 .

[0254] Finally, a second electrode 1103 functioning as a cathode was formed by depositing aluminum to a thickness of 200 nm. The vapor deposition was carried out so that

[0255] In the above-described deposition process, the deposition was all carried out by resistance heating.

[0256] The element structure of the light-emitting element of this example obtained as described above is shown in Table 3.

[0257] [Table 3]

[0258] The light emitting element 3 is placed in a glove box with a nitrogen atmosphere so that the light emitting element is not exposed to the atmosphere. After sealing with a glass substrate as described above, the operating characteristics of the light emitting element of this example were examined. The measurements were carried out at room temperature (an atmosphere maintained at 25°C).

[0259] The luminance-current efficiency characteristics of the light-emitting element of this example are shown in FIG. 14. In FIG. 14, the horizontal axis represents the luminance (cd / m 2 ) and the vertical axis represents the current efficiency (cd / A). The voltage-luminance characteristics are shown in Figure 15 In FIG. 15, the horizontal axis represents voltage (V) and the vertical axis represents luminance (cd / m 2 ) and The luminance-external quantum efficiency characteristics are shown in Figure 16. In Figure 16, the horizontal axis represents luminance (cd / m 2 ) The vertical axis represents the external quantum efficiency (%). 2 Voltage (V), current density (mA / cm 2 ), CIE chromaticity coordinates (x, y), current efficiency The optical density (cd / A), power efficiency (lm / W), and external quantum efficiency (%) are shown in Table 4.

[0260] [Table 4]

[0261] As described above, it was found that the light-emitting element 3 exhibited good device characteristics.

[0262] The emission spectrum of the light-emitting element of this example is shown in FIG. 17. In FIG. 17, the horizontal axis represents The vertical axis represents the wavelength (nm), and the vertical axis represents the luminous intensity (arbitrary unit). Brightness 1000 cd / m 2 Light emitted when The CIE chromaticity coordinates of element 3 were (x, y) = (0.46, 0.47). As shown in Figure 4, the light-emitting element of this example emits red light derived from [Ir(tppr)2(dpm)]. green light from [Ir(tBuppm)2(acac)] and [Ir(mpptz -dmp)3]. .

[0263] Next, a reliability test was conducted on the light-emitting element 3. The results of the reliability test are shown in FIGS. In FIG. 18, the vertical axis indicates the normalized brightness (%) when the initial brightness is 100%, and the horizontal axis indicates The vertical axis in Figure 19 shows the driving time (h) of the element. The horizontal axis shows the activation voltage, and the horizontal axis shows the device operation time (h). 3000cd / m 2 The light emitting device of this example was driven under the condition of a constant current density. As can be seen from FIG. 18, although the light emitted from each light-emitting layer of the light-emitting element 3 is all phosphorescence, The brightness remained at 72% of the initial value even after 1100 hours. It was found that the light-emitting element 3 has a long life. It was found that the light emitting device had a small voltage rise over time and had good reliability.

[0264] In the electron transport layer of the light-emitting element 3, the layer on the anode side contains Cz PA was used, and BPhen, a π-electron deficient heteroaromatic compound, was used as the cathode layer. This is probably why the voltage rise during driving of the light-emitting element 3 was small.

[0265] The results of this example show that the light-emitting element 3 of one embodiment of the present invention has favorable element characteristics and a long life. It was found that the light-emitting device has a long life and can obtain well-balanced light from the three guest materials. It was.

[0266] (Reference example) The tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)- (4H-1,2,4-triazol-3-yl-κN2]phenyl-κC} Synthetic method of iridium(III) (abbreviation: [Ir(mpptz-dmp)3]) explain.

[0267] [ka]

[0268] <Step 1: Synthesis of N-benzoyl-N'-2-methylbenzoylhydrazide> First, 15.0 g (110.0 mmol) of benzoylhydrazine and N-methyl-2-pyrrolidone were mixed. 75 ml of lysinone (NMP) was placed in a 300 ml three-necked flask and stirred under ice cooling. The mixture was mixed with 17.0 g (110.0 mmol) of o-toluic acid chloride and 15 ml of NMP. After the dropwise addition, the mixture was stirred at room temperature for 24 hours. When the reaction solution was slowly added to 500 ml of water, a white solid precipitated. The sample was ultrasonically cleaned alternately with 1M hydrochloric acid and hexane, and then with N-benzoxanthracene. A white solid of 19.5 g of methyl-N'-2-benzoylhydrazide was obtained in 70% yield. The synthesis scheme of step 1 is shown below in (a-1).

[0269] [ka]

[0270] <Step 2; [Chloro(2-methylphenyl)methanone][chloro(phenyl)methyl Synthesis of denhydrazones> Next, N-benzoyl-N'-2-methylbenzoylhydrazide 1 obtained in Step 1 above was 2.0 g (47.2 mmol) and 200 ml of toluene were placed in a 500 ml three-neck flask. To this mixed solution, 19.4 g (94.4 mmol) of phosphorus pentachloride was added and heated at 120°C for 6 hours. After the reaction time, the reaction solution was slowly poured into 200 ml of water and stirred for 1 hour. After stirring, the organic layer and the aqueous layer were separated, and the organic layer was washed with water and a saturated aqueous solution of sodium bicarbonate. After washing, the organic layer was dried over anhydrous magnesium sulfate. Magnesium sulfate was removed by filtration, and the filtrate was concentrated to give [chloro(2-methylphenyl) 12.6g of brown liquid of [chloro(phenyl)methanone] [chloro(phenyl)methylidene]hydrazone The synthesis scheme of step 2 is shown below in (a-2).

[0271] [ka]

[0272] Step 3: 3-(2-methylphenyl)-4-(2,6-dimethylphenyl)-5- Synthesis of phenyl-4H-1,2,4-triazole (abbreviation: Hmpptz-dmp) Next, [chloro(2-methylphenyl)methanone][chloro(phenyl)methanone] obtained in Step 2 above was 12.6g (43.3mmol) 2,6-dimethylaniline hydrazone 15.7g (134.5mmol) of phosphorus and 100ml of N,N-dimethylaniline are added to 500 The mixture was placed in a 100 ml recovery flask and heated and stirred at 120°C for 20 hours. The solution was slowly added to 200 ml of 1N hydrochloric acid. Dichloromethane was added to this solution to form an organic layer. The target substance was extracted. The obtained organic layer was washed with water and an aqueous solution of sodium bicarbonate, and The magnesium sulfate was removed by gravity filtration, and the resulting filtrate was concentrated. A black liquid was obtained, which was purified by silica gel column chromatography. The developing solvent was ethyl acetate:hexane = 1:5. The obtained fraction was concentrated to give a white This solid was recrystallized from ethyl acetate to give a white solid. 4.5 g of a solid was obtained in a yield of 31%. The synthesis scheme for Step 3 is shown below in (a-3). .

[0273] [ka]

[0274] <Step 4: Synthesis of [Ir(mpptz-dmp)3]> Next, 2.5 g (7.4 mmol) of Hmpptz-dmp obtained in Step 3 above, Tris (Acetylacetonato)iridium(III) 0.7g (1.5mmol) The reaction vessel was heated at 250°C for 48 hours under Ar flow. After the reaction time, the obtained solid was washed with dichloromethane. The solid was obtained by suction filtration. This solid was dissolved in toluene and mixed with alumina and celite (Wako The obtained solution was filtered through a layer of 100% ethanol (Pure Chemical Co., Ltd., Catalog No. 531-16855). The fraction containing the compound was concentrated to give a green solid. This solid was recrystallized from toluene to give a green solid. 0.8 g of powder was obtained in a yield of 45%. The synthesis scheme for step 4 is shown below in (a-4). .

[0275] [ka]

[0276] Nuclear magnetic resonance spectroscopy (NMR) of the green powder obtained in step 4 above 1 H NMR analysis results The results are shown below. From these results, it is clear that [Ir(mpptz-dmp)3] was obtained. It was.

[0277] 1 H NMR.δ(toluene-d8):1.82(s,3H),1.90(s, 3H),2.64(s,3H),6.56-6.62(m,3H),6.67-6.75 (m,3H),6.82-6.88(m,1H),6.91-6.97(t,1H),7 .00-7.12(m,2H),7.63-7.67(d,1H). [Explanation of symbols]

[0278] 101 first electrode 103 EL layer 103a EL layer 103b EL layer 105 Second electrode 107 Charge generation region 201 Hole injection layer 202 Hole transport layer 203 Light-emitting layer 203x First light-emitting layer 203y Second light-emitting layer 203z Third luminescent layer 203B Blue light-emitting layer 203Bd Phosphorescent compound 203Bh host material 203G Green light-emitting layer 203Gd Phosphorescent compound 203Gh host material 203R Red light-emitting layer 203Rd Phosphorescent compound 203Rh host material 204 Electron transport layer 205 Electron injection layer 300 light-emitting elements 301 First electrode 303 EL layer 305 Second electrode 311B Blue light-emitting layer 311Bd Phosphorescent compound 311Bh host material 311ex recombination area 311G Green light-emitting layer 311Gd Phosphorescent compound 311Gh host material 311R Red light-emitting layer 311Rd Phosphorescent compound 311Rh host material 401 Support substrate 403 Light-emitting element 405 Sealing substrate 407 Sealing material 409a First terminal 409b Second terminal 411a Light extraction structure 411b Light extraction structure 413 Planarization layer 415 Space 417 Auxiliary wiring 418 Desiccant 419 Insulating Layer 421 First electrode 423 EL layer 425 Second Electrode 501 Support substrate 503 Light-emitting element 505 Sealing substrate 507 Sealing material 509 FPC 511 Insulating layer 513 Insulating Layer 515 Space 517 Wiring 519 Bulkhead 521 First electrode 523 EL layer 525 Second electrode 541a Transistor 541b transistor 542 transistor 543 Transistor 551 Light-emitting part 552 Drive circuit section 553 Drive circuit section 1101 First electrode 1103 Second electrode 1111 Hole injection layer 1112 Hole transport layer 1113a First light-emitting layer 1113b Second light-emitting layer 1113c Third light-emitting layer 1114 Electron transport layer 1115 Electron injection layer 7100 Television equipment 7101 Housing 7102 Display section 7103 Stand 7111 Remote control device 7200 Computer 7201 Main unit 7202 Case 7203 Display section 7204 keyboard 7205 External connection port 7206 Pointing Device 7300 Handheld Game Console 7301a housing 7301b housing 7302 Connection section 7303a Display section 7303b Display section 7304 Speaker section 7305 Recording medium insertion section 7306 Operation Key 7307 Connection terminal 7308 Sensor 7400 mobile phone 7401 Housing 7402 Display section 7403 Operation button 7404 External connection port 7405 Speaker 7406 Microphone 7500 tablet devices 7501a housing 7501b housing 7502a Display section 7502b Display section 7503 Shaft 7504 Power supply 7505 Operation Key 7506 Speaker 7601 Lighting equipment 7602 Lighting equipment 7603 Tabletop lighting device 7604 Planar lighting device 7701 Lighting Department 7703 Post 7705 Support stand

Claims

1. a first light-emitting layer, a second light-emitting layer, and a third light-emitting layer between a first electrode and a second electrode; the second light-emitting layer is located between the first light-emitting layer and the third light-emitting layer; the first light-emitting layer includes a first host material and a first phosphorescent compound; the first host material comprises a first compound having a π-electron-deficient heteroaromatic ring and at least one of an aromatic amine and a π-electron-rich heteroaromatic ring, and a second compound that forms an exciplex with the first compound; the second light-emitting layer includes a second host material and a second phosphorescent compound; the second host material comprises a third compound having a π-electron-deficient heteroaromatic ring and at least one of an aromatic amine and a π-electron-rich heteroaromatic ring, and a fourth compound that forms an exciplex with the third compound; the third light-emitting layer includes a third host material and a third phosphorescent compound; the third host material comprises a fifth compound having a π-electron-deficient heteroaromatic ring and at least one of an aromatic amine and a π-electron-rich heteroaromatic ring; and a sixth compound that forms an exciplex with the fifth compound; the T 1 level of the third host material is higher than the T 1 level of the first host material; the T 1 level of the third host material is higher than the T 1 level of the second host material; a light-emitting element, wherein, among the first phosphorescent compound, the second phosphorescent compound, and the third phosphorescent compound, the emission peak of the second phosphorescent compound is at the longest wavelength side, and the emission peak of the third phosphorescent compound is at the shortest wavelength side.

2. a first light-emitting layer, a second light-emitting layer, and a third light-emitting layer between a first electrode and a second electrode; the second light-emitting layer is located between the first light-emitting layer and the third light-emitting layer; the first light-emitting layer includes a first host material and a first phosphorescent compound; the first host material comprises a first compound having a π-electron-deficient heteroaromatic ring and at least one of an aromatic amine and a π-electron-rich heteroaromatic ring, and a second compound that forms an exciplex with the first compound; the second light-emitting layer includes a second host material and a second phosphorescent compound; the second host material comprises a third compound having a π-electron-deficient heteroaromatic ring and at least one of an aromatic amine and a π-electron-rich heteroaromatic ring, and a fourth compound that forms an exciplex with the third compound; the third light-emitting layer includes a third host material and a third phosphorescent compound; the third host material comprises a fifth compound having a π-electron-deficient heteroaromatic ring and at least one of an aromatic amine and a π-electron-rich heteroaromatic ring; and a sixth compound that forms an exciplex with the fifth compound; the T 1 level of the third host material is higher than the T 1 level of the first host material; the T 1 level of the third host material is higher than the T 1 level of the second host material; T of the third phosphorescent compound １ The level is the T １ Higher than the level, T of the first phosphorescent compound １ The level is the T １ A light emitting element with a higher level.

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