Light-emitting element, display device, electronic device and lighting device

Abstract

Light-emitting element comprising: a light-emitting layer between an anode and a cathode; and a first layer between the light-emitting layer and the cathode, wherein the first layer is an electron injection layer, wherein the first layer includes a first organic compound and a transition metal, wherein the first organic compound contains an unshared electron pair, and where the first organic compound and the transition metal form a SOMO (single occupied molecular orbital).

Description

Technical area

[0001] One embodiment of the present invention relates to a novel light-emitting element having an electron injection layer. One embodiment of the present invention also relates to a display device, an electronic device, and a lighting device, each incorporating the light-emitting element.

[0002] It should be noted that an embodiment of the present invention is not limited to the above technical field. The technical field of an embodiment of the invention disclosed in this specification and the like relates to an article, a method, or a manufacturing method. An embodiment of the present invention additionally relates to a process, a machine, a product, and a composition. Examples of the technical field of an embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a storage device, a driving method for any of them, and a manufacturing method for any of them. State of the art

[0003] In recent years, intensive research and development has been conducted on light-emitting elements utilizing electroluminescence (EL). The basic structure of such a light-emitting element consists of a layer containing a light-emitting substance (an EL layer) sandwiched between a pair of electrodes. By applying a voltage between the electrodes of this element, light emission from the light-emitting material can be obtained.

[0004] Since the above light-emitting element is of a self-luminous type, a display device using this light-emitting element has the following advantages: high visibility, no need for backlighting, and low power consumption. Furthermore, such a light-emitting element is also advantageous in that the element can be made thin and lightweight, and it has a high response speed.

[0005] In a conventional light-emitting element, an electron injection layer is provided between a cathode and a light-emitting layer to reduce the operating voltage. A metal with a low work function, such as an alkali metal or an alkaline earth metal, typically lithium (Li) or calcium (Ca), or a compound thereof, is used in the electron injection layer to lower the electron injection barrier between the electron injection layer and the cathode (e.g., Patent Document 1).

[0006] In the case where the above light-emitting element is used for a light-emitting device, there are the following two methods: a method of providing subpixels in one pixel with EL layers having functions of emitting light of different colors (hereinafter referred to as a separate coloring method) and a method of providing subpixels in one pixel with, for example, a common EL layer having a function of emitting white light and color filters having functions of transmitting light of different colors (hereinafter referred to as a color filtering method).

[0007] One of the advantages of the color filter method is that the EL layer can be shared by all subpixels. Therefore, compared with the separate coloring method, the material loss of the EL layer is low and the number of steps required to form the EL layer can be reduced, allowing light-emitting devices to be manufactured cost-effectively and with high productivity. While the separate coloring method requires a space between the subpixels to prevent mixing of the EL layer materials within the subpixels, the color filter method eliminates such a space, thus enabling a high-resolution light-emitting device with a higher pixel density.

[0008] The light-emitting element can emit light of various colors depending on the type of light-emitting substance contained in the EL layer. Regarding the application of the light-emitting element to lighting devices, a high-efficiency light-emitting element that emits white light or colored light close to white is required. Regarding the application of the light-emitting element to a light-emitting device that uses a color filter process, a high-efficiency light-emitting element that emits light with high color purity is required. Furthermore, low power consumption is required for the light-emitting element used for the lighting device and the light-emitting device.

[0009] Increasing the light extraction efficiency from a light-emitting device is important for increasing the emission efficiency of a light-emitting element. To improve the light extraction efficiency from a light-emitting element, a method has been proposed that uses an optical microresonator (microcavity) structure, which utilizes a light resonance effect between a pair of electrodes to enhance the intensity of light with a specific wavelength (see, for example, Patent Document 2).

[0010] As a light-emitting element that emits white light, an element having a charge generation layer between a plurality of EL layers (a tandem element) has been proposed.

[0011] To improve element properties of such a light-emitting element, improvement of an element structure, development of a material, and the like have been actively pursued. US 2016 / 0285016 A1 discloses an organic light-emitting element containing a neutral molecular paramagnetic metal complex as an emitter in its organic emission layer. US 2011 / 0240980 A1 discloses an organic electronic device containing an n-type dopant with an imidazole-based material comprising a hydrogen-based material bonded between nitrogen atoms. [References][Patent Documents] [Patent Document 1] Japanese Patent Laid-Open No. JP 2001 - 102 175 A [Patent Document 2] Japanese Patent Laid-Open No. JP 2015 - 130 319 A Disclosure of the invention

[0012] A metal with a low work function and a metal compound are difficult to handle due to their high reactivity with oxygen or water. When the metal or compound is used for a light-emitting element, a reduction in emission efficiency, an increase in operating voltage, a decrease in reliability, or the like of the light-emitting element are sometimes caused by oxygen or water. Accordingly, there is a need to develop an electron injection layer that is hardly affected by oxygen and water and presents only a small barrier to electron injection between the electron injection layer and a cathode.

[0013] Furthermore, an electron injection layer adjacent to a charge generation layer of a tandem element must have excellent electron injection properties. Accordingly, an alkali metal such as lithium or cesium, or a compound of an alkali metal, or an alkaline earth metal such as calcium, or a compound of an alkaline earth metal is used for the electron injection layer. However, if the metal or compound is used for the electron injection layer, the metal diffuses into an electron transport layer, causing crosstalk in some cases.

[0014] In view of the problems described above, an object of an embodiment of the present invention is to provide a light-emitting element with a low operating voltage. Another object of an embodiment of the present invention is to provide a light-emitting element with high moisture resistance. Another object of an embodiment of the present invention is to provide a light-emitting element with high oxidation resistance. Another object of an embodiment of the present invention is to provide a light-emitting element with low power consumption. Another object of an embodiment of the present invention is to provide a light-emitting element with high reliability. Another object of an embodiment of the present invention is to provide a novel light-emitting element.Another object of an embodiment of the present invention is to provide a novel semiconductor device. Another object of an embodiment of the present invention is to provide a light-emitting element in which crosstalk is unlikely to occur. Another object of an embodiment of the present invention is to provide a light-emitting element that emits light with high color purity.

[0015] Another object of an embodiment of the present invention is to provide an electronic device and a lighting device, each having high moisture resistance and including the light-emitting element. Another object of an embodiment of the present invention is to provide a low-power consumption light-emitting device using the light-emitting element. Another object of an embodiment of the present invention is to provide a long-life light-emitting device using the light-emitting element.

[0016] It should be noted that the description of the above objects does not preclude the existence of further objects. In or in an embodiment of the present invention, it is not necessary to fulfill all of the objects. Further objects will become apparent from the explanation of the description and the like and can be derived therefrom.

[0017] Accordingly, the invention relates to a light-emitting element according to any one of claims 1 to 5, a display device according to claim 19, an electronic device according to claim 20, and a lighting device according to claim 21. Advantageous embodiments are described in the subclaims. One embodiment of the present invention is a light-emitting element comprising a light-emitting layer between an anode and a cathode and a first layer between the light-emitting layer and the cathode. The first layer comprises a transition metal and a first organic compound having an unshared or lone pair of electrons. The first organic compound and the transition metal form a singly occupied molecular orbital (SOMO).

[0018] Another embodiment of the present invention is a light-emitting element comprising a first light-emitting unit and a second light-emitting unit between an anode and a cathode, and a first layer between the first light-emitting unit and the second light-emitting unit. The first layer includes a first organic compound and a transition metal. The first organic compound has an unshared electron pair. The first organic compound and the transition metal form SOMO.

[0019] Another embodiment of the present invention is a light-emitting element comprising a first light-emitting unit and a second light-emitting unit between an anode and a cathode, and a first layer and a charge generation layer between the first light-emitting unit and the second light-emitting unit. The first layer and the charge generation layer are in contact with each other. The first layer includes a first organic compound and a first transition metal. The first organic compound has an unshared electron pair. The first organic compound and the first transition metal form SOMO.

[0020] In any of the above embodiments, it is preferable that the first organic compound includes an electron-deficient heteroaromatic ring. It is further preferable that the first organic compound includes at least one of a pyridine ring, a diazine ring, and a triazine ring.

[0021] In any of the above embodiments, it is preferable that the first organic compound has 25 to 100 carbon atoms.

[0022] In any of the above embodiments, it is preferable that the first organic compound does not contain a 1,10-phenanthroline skeleton.

[0023] In any of the above embodiments, it is preferable that a lowest unoccupied molecular orbital (LUMO) level of the first organic compound is higher than or equal to -3.6 eV and lower than or equal to -2.3 eV.

[0024] In any of the above embodiments, it is preferable that a transition metal is a metal of Group 5, Group 7, Group 9, or Group 11 of the Periodic Table. It is further preferable that the transition metal is a metal of Group 11. It is particularly preferred that the transition metal is Ag.

[0025] In any of the above embodiments, it is preferable that a second layer is included between the cathode and the first layer, and the second layer includes a second organic compound having an electron-deficient heteroaromatic ring.

[0026] In any of the above embodiments, it is preferable that a LUMO level of the second organic compound is lower than a SOMO level.

[0027] In any of the above embodiments, it is preferable that an alkali metal and an alkaline earth metal are not contained in the light-emitting element.

[0028] In any of the above embodiments, it is preferable that a molar ratio of the metal to the first organic compound in the first layer is greater than or equal to 0.2 and less than or equal to 0.8.

[0029] In any of the above embodiments, it is preferable that the cathode contains a metal corresponding to the metal of the first layer. Furthermore, it is preferable that the light-emitting layer contains the first organic compound.

[0030] Another embodiment of the present invention is an electronic device comprising the display device having any of the above structures and a housing and / or a touch sensor. Another embodiment of the present invention is a lighting device comprising the light-emitting element having any of the above structures and a housing and / or a touch sensor. The category of an embodiment of the present invention includes not only the light-emitting device comprising the light-emitting element, but also an electronic device comprising the light-emitting device. Therefore, the light-emitting device of this description relates to an image display device or a light source (including a lighting device). It is a display module in which a connection member such asa flexible printed circuit (FPC) or a tape carrier package (TCP) is connected to a light-emitting element, a display module in which a printed circuit board is provided at the top of a TCP, and a display module in which an integrated circuit (IC) is directly mounted on a light-emitting element by a chip-on-glass (COG) method are also embodiments of the present invention.

[0031] An embodiment of the present invention makes it possible to provide a light-emitting element with a low operating voltage. An embodiment of the present invention makes it possible to provide a light-emitting element with high moisture resistance. An embodiment of the present invention makes it possible to provide a light-emitting element with high oxidation resistance. An embodiment of the present invention makes it possible to provide a light-emitting element with low power consumption. An embodiment of the present invention makes it possible to provide a light-emitting element with high reliability. An embodiment of the present invention makes it possible to provide a novel light-emitting element. An embodiment of the present invention makes it possible to provide a novel semiconductor device.An embodiment of the present invention makes it possible to provide a light-emitting element in which crosstalk is unlikely to occur. An embodiment of the present invention makes it possible to provide a light-emitting element that emits light with high color purity.

[0032] An embodiment of the present invention makes it possible to provide an electronic device and a lighting device, each having high moisture resistance and including the light-emitting element. An embodiment of the present invention makes it possible to provide a light-emitting device with low power consumption using the light-emitting element. An embodiment of the present invention makes it possible to provide a light-emitting device with a long lifetime using the light-emitting element.

[0033] It should be noted that the description of these effects does not preclude the existence of other effects. An embodiment of the present invention does not necessarily achieve all of the effects listed above. Other effects will become apparent from and can be derived from the explanation of the specification, drawings, claims, and the like. Short description of the drawings Fig. 1A to Fig. 1C are schematic cross-sectional views illustrating a light-emitting element of an embodiment of the present invention and a diagram illustrating the correlation between energy levels in an electron injection layer. Fig. 2A and Fig. 2B are schematic cross-sectional views each illustrating a light-emitting element of an embodiment of the present invention. Fig. 3A and Fig. 3B are schematic cross-sectional views each illustrating a light-emitting element of an embodiment of the present invention. Fig. 4A and Fig. 4B are a plan view and a schematic cross-sectional view illustrating a display device of an embodiment of the present invention. Fig. 5A and Fig. 5B are plan views each illustrating a display device of an embodiment of the present invention. Fig. 6 is a schematic cross-sectional view illustrating a display device of an embodiment of the present invention. Fig. 7A to Fig. 7G are cross-sectional views showing examples of a transistor. Fig. 8A to Fig. 8D show electronic devices of an embodiment of the present invention. Fig. 9A to Fig. 9E are perspective views illustrating display devices of an embodiment of the present invention. Fig. 10A to Fig. 10C show lighting devices of an embodiment of the present invention. Fig. 11 shows lighting devices of an embodiment of the present invention. Fig. 12 is a schematic cross-sectional view illustrating a light-emitting element of an example. Fig. Figure 13 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 14 shows the current density-voltage characteristics of light-emitting elements of an example. Fig. Figure 15 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 16 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 17 shows electroluminescence spectra of light-emitting elements of an example. Fig. Figure 18 shows absorption spectra of thin films of an example. Fig. Figure 19 shows absorption spectra of thin films of an example. Fig. Figure 20 shows absorption spectra of thin films of an example. Fig. Figure 21 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 22 shows the current-voltage characteristics of light-emitting elements of an example. Fig. Figure 23 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 24 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 25 shows electroluminescence spectra of light-emitting elements of an example. Fig. Figure 26 shows absorption spectra of thin films of an example. Fig. Figure 27 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 28 shows the current density-voltage characteristics of light-emitting elements of an example. Fig. Figure 29 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 30 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 31 shows electroluminescence spectra of light-emitting elements of an example. Fig. 32 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 33 shows the current-voltage characteristics of light-emitting elements of an example. Fig. 34 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 35 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 36 shows electroluminescence spectra of light-emitting elements of an example. Fig. 37 is a schematic cross-sectional view illustrating a light-emitting element of an example. Fig. 38 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 39 shows the current density-voltage characteristics of light-emitting elements of an example. Fig. 40 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 41 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 42 shows electroluminescence spectra of light-emitting elements of an example. Fig. 43 shows the results of the operating life tests of light-emitting elements of an example. Fig. 44 shows the results of the operating life tests of light-emitting elements of an example. Fig. 45 shows the results of the operating life tests of light-emitting elements of an example. Fig. 46 shows the power efficiency-luminance characteristics of a light-emitting element of an example. Fig. 47 shows the current-voltage characteristics of a light-emitting element of an example. Fig. 48 shows an electroluminescence spectrum of a light-emitting element of an example. Fig. 49A and Fig. 49B are schematic cross-sectional views each illustrating a light-emitting element of an embodiment of the present invention. Fig. 50A and Fig. 50B are schematic cross-sectional views each illustrating a light-emitting element of an embodiment of the present invention. Fig. 51 is a schematic cross-sectional view showing light-emitting elements of an example. Fig. 52A and Fig. 52B are enlarged photographs of light-emitting elements of an example. Fig. 53 shows the relationship between the brightness and the distance from a neighboring pixel of an example. Fig. 54 is a schematic cross-sectional view illustrating a light-emitting element of an example. Fig. 55 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 56 shows the current density-voltage characteristics of light-emitting elements of an example. Fig. 57 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 58 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 59 shows electroluminescence spectra of light-emitting elements of an example. Fig. 60 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 61 shows the current density-voltage characteristics of light-emitting elements of an example. Fig. 62 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 63 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 64 shows electroluminescence spectra of light-emitting elements of an example. Fig. 65 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 66 shows the current density-voltage characteristics of light-emitting elements of an example. Fig. 67 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 68 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 69 shows electroluminescence spectra of light-emitting elements of an example. Fig. 70 is a schematic cross-sectional view illustrating a light-emitting element of an example. Fig. 71 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 72 shows the current-voltage characteristics of light-emitting elements of an example. Fig. 73 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 74 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 75 shows electroluminescence spectra of light-emitting elements of an example. Fig. 76 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 77 shows the current-voltage characteristics of light-emitting elements of an example. Fig. 78 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 79 shows electroluminescence spectra of light-emitting elements of an example. Fig. 80 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 81 shows the current-voltage characteristics of light-emitting elements of an example. Fig. 82 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 83 shows electroluminescence spectra of light-emitting elements of an example. Fig. 84 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 85 shows the current-voltage characteristics of light-emitting elements of an example. Fig. 86 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 87 shows electroluminescence spectra of light-emitting elements of an example. Fig. 88A and Fig. 88B each show the relationship between the LUMO level of an organic compound and the emission area ratio after a constant temperature and humidity maintenance test of an example. Fig. 89 is a schematic cross-sectional view illustrating a light-emitting element of an example. Fig. 90 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 91 shows the current-voltage characteristics of light-emitting elements of an example. Fig. 92 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 93 shows electroluminescence spectra of light-emitting elements of an example. Fig. 94 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 95 shows the current-voltage characteristics of light-emitting elements of an example. Fig. 96 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 97 shows electroluminescence spectra of light-emitting elements of an example. Fig. 98 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. Figure 99 shows the current-voltage characteristics of light-emitting elements of an example. Fig. 100 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 101 shows electroluminescence spectra of light-emitting elements of an example. Fig. 102 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 103 shows the current-voltage characteristics of light-emitting elements of an example. Fig. 104 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 105 shows electroluminescence spectra of light-emitting elements of an example. Fig. 106 shows the results of the operating life tests of light-emitting elements of an example. Fig. 107 shows the results of an electron spin resonance (ESR) measurement. Fig. 108 shows the power efficiency-luminance characteristics of light-emitting elements of an example. Fig. 109 shows the current-voltage characteristics of light-emitting elements of an example. Fig. 110 shows external quantum efficiency-luminance characteristics of light-emitting elements of an example. Fig. 111 shows electroluminescence spectra of light-emitting elements of an example. Best mode for carrying out the invention

[0034] Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following description, and the modes and details can be changed in various ways without departing from the scope and spirit of the present invention. Therefore, the present invention should not be construed as being limited to the contents of the following embodiments.

[0035] Note that the position, size, range, or the like of each structure illustrated in the drawings and the like is not precisely illustrated in some cases for ease of understanding. Therefore, the disclosed invention is not necessarily limited to the position, size, range, or the like disclosed in the drawings and the like.

[0036] Note that ordinal numbers such as "first," "second," and the like are used in this specification and the like for convenience, and do not indicate the order of steps or the arrangement order of layers. Therefore, for example, an appropriate description can be made even if "first" is replaced with "second" or "third." Furthermore, the ordinal numbers in this specification and the like are not necessarily the same as those specifying an embodiment of the present invention.

[0037] When structures of the invention are described with reference to the drawings in this specification and the like, common reference numerals are used for the same portions in different drawings.

[0038] In this specification and the like, the terms "film" and "layer" may be interchanged depending on the situation or circumstances. For example, the term "conductive layer" may be replaced with the term "conductive film" in some cases. Also, the term "insulating film" may be replaced with the term "insulating layer" in some cases. (Embodiment 1)

[0039] In this embodiment, a light-emitting element of an embodiment of the present invention will be described below with reference to Fig. 1A to Fig. 1C described. <Strukturbeispiel 1 des Licht emittierenden Elements>

[0040] Fig. 1A is a schematic cross-sectional view of a light-emitting element 150 of an embodiment of the present invention.

[0041] The light-emitting element 150 includes a pair of electrodes (an electrode 101 and an electrode 102) and an EL layer 100 between the pair of electrodes. The EL layer 100 includes at least a light-emitting layer 140 and an electron-injection layer 130.

[0042] The EL layer 100, which is Fig. 1A, in addition to the light-emitting layer 140 and the electron injection layer, it includes functional layers such as a hole injection layer 111, a hole transport layer 112, and an electron transport layer 118.

[0043] Although in this embodiment, description is made assuming that the electrode 101 and the electrode 102 of the pair of electrodes serve as the anode and the cathode, respectively, the structure of the light-emitting element 150 is not limited to this. That is, the electrode 101 may be a cathode, the electrode 102 may be an anode, and the arrangement order of the layers between the electrodes may be reversed. In other words, the hole-injection layer 111, the hole-transport layer 112, the light-emitting layer 140, the electron-transport layer 118, and the electron-injection layer 130 may be arranged in this order from the anode side.

[0044] It should be noted that the structure of the EL layer 100 is not limited to the Fig. 1A, and that the EL layer 100 includes at least the light-emitting layer 140 and the electron-injection layer 130 and does not necessarily include the hole-injection layer 111, the hole-transport layer 112, and the electron-transport layer 118.

[0045] These layers can be formed in the EL layer between the pair of electrodes depending on their functions, and are not limited to the above layers. In other words, the EL layer between the pair of electrodes may include a layer having any of the following functions: a layer that lowers a hole or electron injection barrier, a layer that enhances a hole or electron transport property, a layer that prevents hole or electron transport, a layer that suppresses an electrode-induced quenching effect, or the like.

[0046] The light-emitting layer 140 preferably includes a host material and a guest material (a light-emitting material).

[0047] As the host material, it is preferable to use one or both of a material with a hole-transporting function (hole-transport property) and a material with an electron-transporting function (electron-transport property). Alternatively, it is preferable to use a material with both a hole-transporting property and an electron-transporting property.

[0048] When the host material is a combination of an electron-transport material and a hole-transport material, the charge carrier balance can be easily controlled by adjusting the mixing ratio. Specifically, the weight ratio of the electron-transport material to the hole-transport material is preferably in a range of 1:9 to 9:1. Since the charge carrier balance can be easily controlled through the structure, a charge carrier recombination range can also be easily controlled.

[0049] The guest material may be a light-emitting compound, and the light-emitting compound is preferably a substance capable of emitting fluorescence (hereinafter also referred to as a fluorescent compound) or a substance capable of emitting phosphorescence (hereinafter also referred to as a phosphorescent compound).

[0050] In order to reduce the driving voltage of the light-emitting element, it is necessary to lower a barrier to electron injection between the light-emitting layer 140 and the electrode 102. Therefore, it is preferable to provide the electron injection layer 130 between the light-emitting layer 140 and the electrode 102. In a conventional light-emitting element, the electron injection layer 130 is formed using a metal material including an alkali metal or an alkaline earth metal with a low work function. However, a metal material with a low work function has high reactivity with oxygen or water; accordingly, when such a metal material is used for a light-emitting element, a decrease in emission efficiency, an increase in driving voltage, a reduction in the element lifetime, and fading occur.Shrinkage (a non-emission area at the end of a light-emitting portion) or the like may occur in the light-emitting element, which in some cases leads to deterioration of the characteristics or a reduction in the reliability of the light-emitting element. In other words, a metal material with a low work function may lead to degradation of the elements. Thus, a light-emitting element without alkali or alkaline earth metal is preferable to suppress deterioration of the characteristics or a reduction in the reliability of the light-emitting element.

[0051] Meanwhile, if a metal with a high work function is used for the electron-injection layer 130, a barrier to electron injection is formed between the electron-injection layer 130 and the electrode 102, even though such a metal has low reactivity with oxygen and water. In this case, an increase in the operating voltage or a decrease in the emission efficiency occurs in the light-emitting element.

[0052] The present inventors have found that a barrier to electron injection between the electron injection layer and the cathode can be reduced and the moisture resistance of the light-emitting element can be increased by forming SOMO by interaction between a compound having an unshared electron pair and a transition metal and using a composite material of the compound and the transition metal forming the SOMO in combination for the electron injection layer.

[0053] To form SOMO through the interaction between a compound with an unshared electron pair and a transition metal, the sum of the number of electrons of the compound and the transition metal is preferably an odd number. Accordingly, if the number of electrons of the compound is an even number, the transition metal is preferably a metal belonging to an odd-numbered group of the periodic table. In the case where the number of electrons of the compound is an odd number, the transition metal is preferably a metal belonging to an even-numbered group of the periodic table.

[0054] As a compound having an unshared electron pair, an organic compound with an electron-transporting function is preferably used. Furthermore, an organic compound that acts as an electron acceptor with respect to the transition metal is preferably used.

[0055] Thus, the light-emitting element of one embodiment of the present invention is a light-emitting element in which a composite material of a transition metal and an organic compound having an unshared electron pair is used for an electron injection layer.

[0056] A transition metal has low reactivity with water and oxygen; accordingly, in a light-emitting element using a transition metal, element deterioration by water and oxygen, which may occur when using a metal with a low work function, hardly occurs. Thus, according to one embodiment of the present invention, a light-emitting element with high moisture resistance and high oxidation resistance can be provided.

[0057] Fig. Figure 1B is a schematic view of the electron injection layer 130 in the light-emitting element of one embodiment of the present invention. The electron injection layer 130 includes a compound 131 having an unshared electron pair and a transition metal 132.

[0058] Fig. 1C is a diagram illustrating the energy in the electron injection layer 130 of the light-emitting element of one embodiment of the present invention. When the transition metal 132 and the compound 131 are mixed, the compound 131 interacts with an atom of the transition metal 132, thereby forming an SOMO. At this time, it is preferable that the highest occupied molecular orbital (HOMO) level formed by the interaction between the compound 131 and the atom of the transition metal 132 be approximately equal to the HOMO level of the original compound 131. In the case where an organic compound having a function of transporting an electron is used for the compound 131, the HOMO level of the compound 131 is low, and a hole is not easily injected into the compound 131.Therefore, when the HOMO level formed by the interaction between compound 131 and the transition metal atom 132 is approximately equal to the HOMO level of the original compound 131, a barrier to hole injection between electron injection layer 130 and electrode 102 is high; accordingly, a hole cannot easily penetrate from electron injection layer 130 to electrode 102, resulting in an improvement in the charge carrier balance in the light-emitting element. Note that in this specification and the like, HOMO refers to a molecular orbital having the highest energy among the orbitals occupied by electrons.

[0059] SOMO is an orbital with only one electron. When a voltage is applied to the light-emitting element 150, the electron in the SOMO serves as a charge carrier in the light-emitting element and is transported to the electron-transport layer 118 and the light-emitting layer 140. Furthermore, electrons can be easily injected from the electrode 102 into the electron-injection layer 130. That is, when the electron-injection layer 130 includes materials that form SOMO in combination, electrons can be easily injected from the electrode 102 into the EL layer 100. The SOMO level is preferably lower than the LUMO level of the compound 131. Accordingly, the LUMO level of the compound 131 is preferably high. Specifically, the LUMO level of the compound 131 is preferably higher than or equal to -3.6 eV and lower than or equal to -2.3 eV.When an organic compound having such a LUMO level and a transition metal are mixed, an SOMO level suitable for electron injection is formed by the interaction, whereby a barrier for electron injection between the electron injection layer 130 and the electrode 102 can be lowered.

[0060] It should be noted that the HOMO level and LUMO level of an organic material are generally estimated by cyclic voltammetry (CV), photoelectron spectroscopy, optical absorption spectroscopy, inverse photoemission spectroscopy, or the like. When comparing values ​​of different compounds, it is desirable to use values ​​estimated using the same measurement method.

[0061] The transition metal described above preferably belongs to Group 5, Group 7, Group 9 or Group 11. Among the transition metals belonging to the odd-numbered groups, a metal having one electron (an unpaired electron) in the outermost shell orbital is particularly advantageous because it has the property of easily forming SOMO by combining with compound 131. <Schätzung des SOMO-Niveaus, das durch Wechselwirkung zwischen dem Übergangsmetall 132 und der Verbindung 131 gebildet wird, durch quantenchemische Berechnungen>

[0062] The interaction between compound 131 and transition metal 132 is required for the formation of SOMO. Accordingly, the stabilization energy when an organic compound interacts with various transition metal atoms and the SOMO levels formed by interaction between the organic compound and the transition metal atoms are estimated by quantum chemical calculations. The results are presented in Table 1. Note that 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen) is used as the organic compound with an unshared electron pair, which is shown below. [Table 1] Stabilisierungsenergie (eV) HOMO (eV) SOMO (eV) LUMO (eV) NBPhen - -5,74 - -2,04 NBPhen + Cu -2,28 -5,04 -3,04 -1,99 NBPhen + Ag -0,23 -5,85 -3,26 -2,07 NBPhen +Au -0,23 -5,85 -4,41 -2,67 NBPhen + Co -2,47 -5,25 -3,10 -2,09 NBPhen + Mn -2,70 -5,43 -3,31 -1,98 NBPhen + Li -2,31 -5,50 -2,96 -1,91

[0063] Gaussian 09 is used as the quantum chemical calculation program. A high-performance computer (ICE X, manufactured by SGI Japan, Ltd.) is used for the calculations. First, the most stable structures in the ground state of the organic compound alone, the ground state of each transition metal alone, and the ground state of a composite material of the organic compound and each transition metal are calculated using density functional theory (DFT). 6-311G(d,p) and LanL2DZ are used as the basis functions, and B3LYP is used as the functional. Then, the stabilization energy is calculated by subtracting the sum of the total energy of the organic compound alone and the total energy of the transition metal alone from the total energy of the composite material of the organic compound and the transition metal.That is, (stabilization energy) = (the total energy of the composite material composed of the organic compound and the transition metal) - (the total energy of the organic compound alone) - (the total energy of the transition metal alone) is satisfied. In DFT, the total energy is represented as the sum of the potential energy, the electrostatic energy between electrons, the electronic kinetic energy, and the exchange-correlation energy, including all complex interactions between electrons. In DFT, an exchange-correlation interaction is also approximated by a functional (a function of another function) of an electron potential with respect to the electron density to enable calculations with high accuracy.

[0064] As shown in Table 1, when manganese (Mn), a Group 7 transition metal, cobalt (Co), a Group 9 transition metal, and copper (Cu), silver (Ag), and gold (Au), Group 11 transition metals, are used as the transition metals of the composite materials, the stabilization energy is a negative value. This indicates that when an organic compound with an unshared electron pair (here, NBPhen) and a transition metal are mixed, the state in which the organic compound interacts with an atom of the transition metal is more stable than the state in which the organic compound does not interact with an atom of the transition metal. That is, Table 1 shows that when the transition metal and the organic compound with an unshared electron pair are mixed, the organic compound interacts with the transition metal, and the organic compound-transition metal composite material becomes stable.It should be noted that the values ​​of the energy levels of HOMO and LUMO in Table 1 and Table 2 are calculated values ​​and in some cases the values ​​differ from the measured values.

[0065] SOMO is formed by the interaction between the organic compound and the transition metal. The SOMO is an orbital originating from an unpaired electron of a metal and also shared with the orbital of the organic compound. Accordingly, it is shown that the electron orbital of a transition metal and the electron orbital of the organic compound interact with each other. Table 1 shows the SOMO levels. In the case where the composite material of compound 131 and transition metal 132 is used for the electron-injection layer 130, a higher SOMO level is preferable in terms of electron injection. Thus, Cu, Ag, Co, and Mn, each having an SOMO level approximately equivalent to that of Li, which is frequently used as a material for an electron-injection layer, are particularly suitable for the transition metal 132 interacting with compound 131 in one embodiment of the present invention.

[0066] The formation of SOMO through the interaction between compound 131 and transition metal 132 creates an unpaired electron in electron injection layer 130. Thus, the formation of SOMO can be observed by electron spin resonance (ESR). To favorably inject electrons from electrode 102 into light-emitting layer 140, the spin density originating from SOMO is preferably greater than or equal to 1 × 10 16 Spins / cm 3 , more preferably greater than or equal to 5 × 10 16 Spins / cm 3 , even more preferably greater than or equal to 1 × 10 17 Spins / cm 3 .

[0067] Meanwhile, in a manufacturing process of a light-emitting element, an EL layer of a light-emitting element, particularly an electron injection layer, and a cathode are generally formed by a vacuum evaporation method. In these cases, it is preferable to use a material that can be easily deposited by vacuum evaporation, that is, a material with a low melting point. The melting point of a Group 11 element is lower than the melting point of a Group 7 or Group 9 element; accordingly, a Group 11 element can be suitably used for deposition by vacuum evaporation. Among the Group 11 elements, Ag has a particularly low melting point and is preferable. Furthermore, a vacuum evaporation method is preferably used because it allows easy mixing of a transition metal atom and an organic compound.

[0068] Ag or Cu can also be used as the cathode material. Using the same material for the electron injection layer 130 and the electrode 102 is preferable because the light-emitting element is easy to manufacture. Furthermore, using the same material for the electron injection layer 130 and the electrode 102 can increase the adhesion between the electron injection layer 130 and the electrode 102, thereby increasing the reliability of the light-emitting element. Furthermore, the manufacturing cost of the light-emitting element can be reduced.

[0069] Next, the stabilization energy and SOMO levels when Ag is used as the transition metal 132, various organic compounds with unshared electron pairs are used as compounds 131, and the interaction occurs between compounds 131 and Ag atoms are estimated by quantum chemical calculations. The results are presented in Table 2. The organic compounds used for the estimation and their abbreviations are shown below. Note that a calculation method for quantum chemical calculations is similar to a calculation method for calculating the values ​​presented in Table 1. [Table 2] Stabilisierungsenergie (eV) HOMO (eV) SOMO (eV) LUMO (eV) 2mDBTBPDBq-II - -5,96 - -2,10 2mDBTBPDBq-II + Ag -0,08 -5,98 -4,37 -2,71 Alq3 - -5,25 - -2,01 Alq3 + Ag -0,16 -5,42 -3,78 -2,20 HATNA - -6,65 - -2,90 HATNA + Ag -0,59 -6,30 -4,05 -3,01 2Py3Tzn - -6,89 - -2,20 2Py3Tzn + Ag -0,28 -6,78 -3,63 -2,45 TmPPPyTz - -6,52 - -2,26 TmPPPyTz + Ag -0,04 -6,55 -4,51 -2,89 Zn(BTZ)2 - -5,60 - -2,00 Zn(BTZ)2 + Ag -0,14 -5,68 -4,09 -2,33

[0070] In Table 2, the stabilization energy shows negative values ​​in the case where the various organic compounds with unshared electron pairs are mixed with transition metals (here Ag), which shows that a composite material composed of the organic compound with an unshared electron pair and a transition metal is stabilized by interaction.

[0071] In the case where compound 131 interacts with an atom of transition metal 132, it is desirable that the atom of transition metal 132 and compound 131 serve as electron donors and electron acceptors, respectively. In this case, compound 131 preferably has an electron-deficient heteroaromatic ring. Compound 131 with such a structure readily accepts electrons, thereby lowering the stabilization energy when compound 131 and the atom of transition metal 132 interact with each other. A compound having an electron-deficient heteroaromatic ring has a favorable electron-transport property; accordingly, such a compound is preferably used as compound 131 of the electron-injection layer to reduce the operating voltage of the light-emitting element.

[0072] Preferably, the electron-deficient heteroaromatic ring is a nitrogen-containing heteroaromatic ring; further, the nitrogen-containing heteroaromatic ring preferably includes at least one of a pyridine ring, a diazine ring (a pyrimidine ring, a pyrazine ring, or a pyridazine ring), and a triazine ring. Light-emitting elements including these rings can have high reliability because these rings have high electrochemical stability. Furthermore, the operating voltage of the light-emitting elements can be reduced because these rings have high electron-transport properties. Note that a compound including the electron-deficient heteroaromatic ring may be a metal complex.

[0073] In the case where an organic compound is used as compound 131, the organic compound preferably has 25 to 100 carbon atoms. When an organic compound has such a number of carbon atoms, the organic compound can exhibit a high sublimation property, and accordingly, thermal decomposition of the organic compound during vacuum evaporation can be suppressed, thereby achieving advantageous and efficient material utilization. Furthermore, the glass transition temperature (Tg) is preferably 100°C or higher. When an organic compound having such a Tg is used for the EL layer, the light-emitting element can exhibit high heat resistance.

[0074] As shown in Table 1 and Table 2, the stabilization energy in the case where NBPhen, diquinoxalino[2,3-a:2',3'-c]phenazine (abbreviation: HATNA), and 2,4,6-tris[3'-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz) interact with Ag atoms is lower than the stabilization energy in the case where the other organic compounds interact with Ag atoms. This is because the heterocycles of the above compounds (NBPhen, HATNA, and TmPPPyTz) each have a conjugated double bond NCCN across the plurality of heterocycles, so that a chelate ring (a ring structure) can be formed by the interaction between compound 131 and transition metal 132. Accordingly, in the case where compound 131 coordinates to an atom of transition metal 132, a chelate ring is preferentially formed because the stabilization energy becomes low.

[0075] The molar ratio of the transition metal 132 to the compound 131 is preferably higher than or equal to 0.1 and lower than or equal to 10, more preferably higher than or equal to 0.2 and lower than or equal to 2, even more preferably higher than or equal to 0.2 and lower than or equal to 0.8. When the transition metal 132 and the compound 131 are mixed in such a molar ratio, a light-emitting element having a favorable electron injection property can be provided. In the case where the molar ratio of the transition metal 132 to the compound 131 is too low compared to the above-described ratio, the amount of the compound 131 that interacts with the transition metal 132 to form SOMO is small, resulting in a lower electron injection property in some cases.In case the molar ratio of the transition metal 132 to the compound 131 is too high compared to the ratio described above, the transmittance of the electron injection layer 130 is reduced, which in some cases reduces the emission efficiency of the light-emitting element.

[0076] The thickness of the electron-injection layer 130 is preferably greater than or equal to 3 nm, more preferably greater than or equal to 5 nm. With this structure, the composite material of the transition metal 132 and the compound 131 can work advantageously. The thickness of the electron-injection layer 130 is preferably less than or equal to 50 nm, more preferably less than or equal to 20 nm, even more preferably less than or equal to 10 nm. With this structure, the electron-injection layer 130 is less likely to absorb light, thereby enabling the light-emitting element to have high emission efficiency.

[0077] Next, the stabilization energy and SOMO level for the case where iron (Fe), a transition metal belonging to an even-numbered group, is used as the transition metal 132 and copper phthalocyanine (abbreviation: CuPc) is used as the compound 131, and the interaction between the transition metal 132 and the compound 131 occurs are estimated by quantum chemical calculations. The results are presented in Table 3. Note that a calculation method of the quantum chemical calculations is similar to the calculation method for calculating the values ​​presented in Table 1. [Table 3] Stabilisierungsenergie (eV) HOMO (eV) SOMO (eV) LUMO (eV) CuPc - -5,17 -6,55 -2,98 CuPc + Fe -3,80 -4,84 -3,92 -2,95

[0078] Copper phthalocyanine is a compound with an odd number of electrons, and the SOMO is located at an energy level lower than the HOMO level. As shown in Table 3, when copper phthalocyanine is used as an organic compound with an unshared electron pair and mixed with an even-numbered transition metal (here, Fe), the stabilization energy is negative. This indicates that the interaction between the organic compound with an unshared electron pair and the transition metal atom leads to stabilization.

[0079] The interaction between copper phthalocyanine and Fe creates a SOMO of a copper phthalocyanine-Fe composite material. An energy level of the SOMO lies between a HOMO level and a LUMO level of copper phthalocyanine. Thus, using the composite material for the electron-injection layer 130, a light-emitting element with a high electron-injection property can be provided. <Strukturbeispiel 2 des Licht emittierenden Elements>

[0080] Structural examples different from that of the light-emitting element 150 shown in Fig. 1A to Fig. 1C are shown using Fig. 2A and Fig. 2B.

[0081] Fig. 2A and Fig. 2B are each a cross-sectional view of a light-emitting device of an embodiment of the present invention. It should be noted that in Fig. 2A and Fig. 2B in some cases a section with a similar function to that in Fig. 1A to Fig. 1C is represented by the same hatching pattern and is not specifically designated by a reference symbol. Furthermore, the same reference symbols are used for sections with similar functions, and in some cases, a detailed description of such sections is not repeated.

[0082] A light-emitting element 152 arranged in Fig. 2A includes a pair of electrodes (electrode 101 and electrode 102) and an EL layer 105 between the pair of electrodes. EL layer 105 includes at least light-emitting layer 140 and electron-injection layer 130. Additionally, a buffer layer 117 is included. Buffer layer 117 is provided between electron-injection layer 130 and electrode 102.

[0083] The EL layer 105, which is Fig. 2A, in addition to the light-emitting layer 140, it comprises functional layers such as the hole injection layer 111, the hole transport layer 112, and the electron transport layer 118.

[0084] The buffer layer 117 provided between the electrode 102 and the electron-transport layer 118 reduces the possibility of the electron-transport layer 118, the electron-injection layer 130, the light-emitting layer 140, and the like coming into contact with oxygen and moisture; accordingly, the moisture resistance and oxidation resistance of the light-emitting element can be increased.

[0085] In one embodiment of the present invention, the above-described composite material of compound 131 and transition metal 132 is used for the electron-injection layer 130, and an organic compound containing an electron-deficient heteroaromatic ring is used for the buffer layer 117. As described above, an electron-deficient heteroaromatic ring has a high electron-transport property, so the operating voltage of the light-emitting element can be reduced.

[0086] The buffer layer 117 is preferably provided between the electron injection layer 130 and the electrode 102, in which case, an energy barrier between the electrode 102 and the electron injection layer 130 can be lowered. The thickness of the buffer layer is preferably greater than or equal to 1 nm and less than or equal to 20 nm. With such a structure, an electron injection barrier can be lowered while maintaining a high electron transport property.

[0087] The LUMO level of the organic compound used for the buffer layer 117 is preferably lower than the SOMO level formed in the electron injection layer 130. With such a structure, a barrier to electron injection between the electron injection layer 130 and the electrode 102 can be lowered.

[0088] Note that the above-described composite material of the transition metal 132 and the compound 131 having an unshared electron pair can be used for a thin-film solar cell. In particular, the above-described composite material can also be suitably used for an electron injection layer of a thin-film solar cell. <Strukturbeispiel 3 des Licht emittierenden Elements>

[0089] A light-emitting element 154 which is Fig. 2B, includes a pair of electrodes (electrode 101 and electrode 102) and an EL layer 107 between the pair of electrodes. EL layer 107 includes at least light-emitting layer 140 and electron-injection layer 130. Additionally, a charge generation layer 160 is included. Charge generation layer 160 is provided between electron-injection layer 130 and electrode 102.

[0090] The EL layer 107, which is Fig. 2B, in addition to the light-emitting layer 140, it includes functional layers such as the hole injection layer 111, the hole transport layer 112, and the electron transport layer 118.

[0091] The charge generation layer 160 provided between the electrode 102 and the electron-transport layer 118 reduces the amount of oxygen and moisture entering the electron-transport layer 118, the electron-injection layer 130, the light-emitting layer 140, and the like; accordingly, the moisture resistance and oxidation resistance of the light-emitting element can be increased.

[0092] As described above, when the charge generation layer 160 includes a hole-transport material and an electron-accepting material, and the electron injection layer 130 includes a metal material including an alkali metal or an alkaline earth metal with a low work function, the electron accepting material of the charge generation layer 160 extracts an electron from a material used for the electron injection layer 130. Therefore, a depletion layer forms near the interface between the charge generation layer 160 and the electron injection layer 130, which in some cases increases the operating voltage. To prevent the formation of the depletion layer, a layer having an electron-transferring function has conventionally been required between the electron injection layer 130 and the charge generation layer 160.

[0093] Meanwhile, in the light-emitting element of one embodiment of the present invention, the electron injection layer 130 includes the composite material of the transition metal and the compound having an unshared electron pair, in which case an electron is hardly extracted from the material having an electron-accepting property of the charge generation layer 160. Thus, the charge generation layer 160 can be provided without forming the above-described depletion layer, so that a light-emitting element including a small number of stacked layers and operating at a low operating voltage can be manufactured.

[0094] The thickness of the charge generation layer 160 is not particularly limited and can be controlled accordingly. For example, by controlling the thickness from the light-emitting layer 140 to the electrode 102, the light emitted from the light-emitting layer 140 can be efficiently extracted to the outside of the light-emitting element. That is, by controlling the thickness of the charge generation layer 160, the light extraction efficiency can be increased.

[0095] It is preferable that the charge generation layer 160 is in contact with the electrode 102. With this structure, a barrier to electron injection between the electrode 102 and the EL layer 107 can be lowered, thereby reducing the operating voltage of the light-emitting element. It is further preferable that the charge generation layer 160 is in contact with the electron injection layer 130. As described above, in one embodiment of the present invention, a light-emitting element with a low operating voltage can be manufactured even if the charge generation layer 160 is in contact with the electron injection layer 130. With this structure, the number of stacked layers in the EL layer 107 can be reduced.

[0096] A transition metal oxide can be suitably used as the electron acceptor material of the charge generation layer 160. Examples of the transition metal oxide include titanium oxide, vanadium oxide, tantalum oxide, molybdenum oxide, tungsten oxide, rhenium oxide, ruthenium oxide, chromium oxide, zirconium oxide, hafnium oxide, and silver oxide. Among them, molybdenum oxide is particularly preferable due to its high stability in air, low hygroscopicity, and low cost. By using the transition metal oxide, a barrier to electron injection between the electrode 102 and the charge generation layer 160 can be lowered. Thus, one embodiment of the present invention is a light-emitting element in which both the electron injection layer 130 and the charge generation layer 160 include a transition metal element.It should be noted that the electron acceptor material of the charge generation layer 160 is not limited to the compounds described above.

[0097] As the hole-transport material of the charge generation layer 160, an organic compound having a pyrrole skeleton, a thiophene skeleton, a furan skeleton, or an aromatic amine skeleton is preferably used. The organic compound having the skeleton has a high hole-transport property; accordingly, using the organic compound having the skeleton for the charge generation layer 160 can reduce the operating voltage of the light-emitting element. The hole-transport material of the charge generation layer 160 is not limited to the compound described above. <Strukturbeispiel 4 des Licht emittierenden Elements>

[0098] Structural examples that differ from the structures of the light-emitting element 150 shown in Fig. 1A to Fig. 1C, and the light emitting elements 152 and 154, which are shown in Fig. 2A and Fig. 2B are shown using Fig. 49A and Fig. 49B.

[0099] Fig. 49A and Fig. 49B are schematic cross-sectional views of a light-emitting element 2250a and a light-emitting element 2250b.

[0100] The light-emitting elements 2250a and 2250b each include an electrode 2101, an electrode 2102, an electrode 2103, and an electrode 2104 above a substrate 2200. At least one light-emitting unit 2106, a light-emitting unit 2108, and an electron injection layer 2130 are provided between the electrode 2101 and the electrode 2102, between the electrode 2102 and the electrode 2103, and between the electrode 2102 and the electrode 2104. A charge generation layer 2115 is provided between the light-emitting unit 2106 and the light-emitting unit 2108. Note that the light-emitting unit 2106 and the light-emitting unit 2108 may have the same structure or may have different structures.

[0101] The charge generation layer 2115 provided between the light-emitting unit 2106 and the light-emitting unit 2108 is configured, for example, such that electrons are injected into the light-emitting unit on one side and holes are injected into the light-emitting unit on the other side when a voltage is applied between the electrode 2101 and the electrode 2102. For example, Fig. 49A and Fig. 49B, the charge generation layer 2115 supplies electrons into the light-emitting unit 2106 and holes into the light-emitting unit 2108 when a voltage is applied such that the potential of the electrode 2102 becomes higher than that of the electrode 2101.

[0102] The light-emitting unit 2106 includes, for example, a hole injection layer 2111, a hole transport layer 2112, a light-emitting layer 2140, and an electron transport layer 2113. The light-emitting unit 2108 includes, for example, a hole injection layer 2116, a hole transport layer 2117, a light-emitting layer 2170, an electron transport layer 2118, and an electron injection layer 2119.

[0103] As in Fig. 49A and Fig. 49B, it is preferable that the electron injection layer 2130 is adjacent to the electron transport layer 2113 and is provided between the light-emitting unit 2108 and the electron transport layer 2113. It is preferable that the charge generation layer 2115 is adjacent to the electron injection layer 2130 and is provided between the electron injection layer 2130 and the light-emitting unit 2108. With such a structure, electrons can be efficiently transported to the light-emitting unit 2106.

[0104] Note that in the structural examples of the light-emitting element, electrode 2101, electrode 2103, and electrode 2104 are used as anodes, and electrode 2102 is used as a cathode, but the structures of the light-emitting element 2250a and the light-emitting element 2250b are not limited to this. That is, electrode 2101, electrode 2103, and electrode 2104 may be cathodes, electrode 2102 may be an anode, and the arrangement order of the layers between the electrodes may be reversed.That is, the hole injection layer 2111, the hole transport layer 2112, the light-emitting layer 2140, the electron transport layer 2113, and the electron injection layer 2130 are stacked in this order from the anode side in the light-emitting unit 2106, and the hole injection layer 2116, the hole transport layer 2117, the light-emitting layer 2170, the electron transport layer 2118, and the electron injection layer 2119 are stacked in this order from the anode side in the light-emitting unit 2108.

[0105] The structures of the light-emitting element 2250a and the light-emitting element 2250b are not limited to the Fig. 49A and Fig.49B. At least the light-emitting layer 2140, the light-emitting layer 2170, the charge generation layer 2115, and the electron injection layer 2130 are included in each of the light-emitting elements 2250a and 2250b, but the hole injection layer 2111, the hole injection layer 2116, the hole transport layer 2112, the hole transport layer 2117, the electron transport layer 2113, the electron transport layer 2118, and the electron injection layer 2119 may be optionally included.

[0106] Layers are not limited to the above layers as long as they are formed between the pair of electrodes. In other words, layers between the pair of electrodes may include a layer having any of the following functions: a layer that lowers a hole or electron injection barrier, a layer that enhances a hole or electron transport property, a layer that prevents transport of holes or electrons, a layer that suppresses an electrode-induced quenching effect, or the like.

[0107] Note that when a surface of a light-emitting unit on the anode side is in contact with the charge generation layer 2115, such as a surface in the light-emitting unit 2108, the charge generation layer 2115 may also serve as a hole injection layer in the light-emitting unit 2108 in some cases; therefore, a hole injection layer may not necessarily be formed in the light-emitting unit in such cases.

[0108] The light-emitting elements, each having two light-emitting units, are Fig. 49A and Fig.49B; however, a similar structure can also be applied to a light-emitting element in which three or more light-emitting units are stacked. As in the light-emitting elements 2250a and 2250b, when a plurality of light-emitting units separated by the charge generation layer are arranged between a pair of electrodes, a light-emitting element with high luminance and a long lifetime can be obtained while keeping the current density low. A light-emitting element with low power consumption can also be obtained.

[0109] In the light-emitting element 2250a, the electrode 2101, the electrode 2103, and the electrode 2104 each have a visible light reflecting function, and the electrode 2102 has a visible light transmitting function. In the light-emitting element 2250b, the electrode 2101, the electrode 2103, and the electrode 2104 each have a visible light transmitting function, and the electrode 2102 has a visible light reflecting function.

[0110] Accordingly, the light emitted from the light-emitting element 2250a is guided outward through the electrode 2102, and the light emitted from the light-emitting element 2250b is guided outward through the electrode 2101, the electrode 2103, and the electrode 2104. However, an embodiment of the present invention is not limited to this, and a dual-emission light-emitting element in which light is extracted from both the top and bottom directions of the substrate 2200 in which the light-emitting element is formed may be used.

[0111] The electrode 2101 includes a conductive layer 2101a and a conductive layer 2101b over and in contact with the conductive layer 2101a. The electrode 2103 includes a conductive layer 2103a and a conductive layer 2103b over and in contact with the conductive layer 2103a. The electrode 2104 includes a conductive layer 2104a and a conductive layer 2104b over and in contact with the conductive layer 2104a.

[0112] The conductive layer 2101b, the conductive layer 2103b, and the conductive layer 2104b each have a visible light transmitting function. In the light-emitting element 2250a, the conductive layer 2101a, the conductive layer 2103a, and the conductive layer 2104a each have a visible light reflecting function. In the light-emitting element 2250b, the conductive layer 2101a, the conductive layer 2103a, and the conductive layer 2104a each have a visible light transmitting function.

[0113] The light-emitting element 2250a, which is Fig. 49A, and the light-emitting element 2250b shown in Fig. 49B each include a partition wall 2145 between a region 2222B disposed between the electrode 2101 and the electrode 2102, a region 2222G disposed between the electrode 2102 and the electrode 2103, and a region 2222R disposed between the electrode 2102 and the electrode 2104. The partition wall 2145 has an insulating property. The partition wall 2145 covers end portions of the electrodes 2101, 2103, and 2104 and has openings overlapping with the electrodes. By the partition wall 2145, the electrodes provided above the substrate 2200 in the regions can be divided into island shapes.

[0114] In Fig. 49A and Fig.49B, the hole injection layer 2111, the hole injection layer 2116, the hole transport layer 2112, the hole transport layer 2117, the light-emitting layer 2140, the light-emitting layer 2170, the electron transport layer 2113, the electron transport layer 2118, the electron injection layer 2119, the charge generation layer 2115, and the electrode 2102 are provided in the regions without being divided; however, they may be provided separately in each of the regions.

[0115] In each of the light-emitting elements 2250a and 2250b of one embodiment of the present invention, applying a voltage between the pair of electrodes (electrode 2101 and electrode 2102) in region 2222B, between the pair of electrodes (electrode 2102 and electrode 2103) in region 2222G, and between the pair of electrodes (electrode 2102 and electrode 2104) in region 2222R enables electron injection from the cathode into the electron injection layer 2119 and hole injection from the anode into the hole injection layer 2111, thereby causing current to flow. Electrons are injected from the charge generation layer 2115 into the electron injection layer 2130, and holes are injected from the charge generation layer 2115 into the hole injection layer 2116. Excitons are formed by the recombination of the injected charge carriers (electrons and holes).When charge carriers (electrons and holes) recombine and excitons are formed in the light-emitting layer 2140 and the light-emitting layer 2170 containing light-emitting materials, the light-emitting materials in the light-emitting layer 2140 and the light-emitting layer 2170 are brought into an excited state, thereby causing light emission from the light-emitting materials.

[0116] Each of the light-emitting layers 2140 and 2170 preferably includes one or more light-emitting materials that emit light of violet, blue, blue-green, green, yellow-green, yellow, yellow-orange, orange, and red.

[0117] The light-emitting layer 2140 and the light-emitting layer 2170 may each have a two-layer structure. Two light-emitting layers, each containing two types of light-emitting materials (a first compound and a second compound) for emitting light of different colors, enable the emission of light of a variety of colors. In particular, it is preferable to select the light-emitting materials of the light-emitting layer 2140 and the light-emitting layer 2170 such that white light or light of a color close to white can be obtained by combining light emissions from the light-emitting layers.

[0118] The light-emitting layer 2140 and / or the light-emitting layer 2170 may have a multilayer structure of three or more layers, which may include a layer that does not contain a light-emitting material.

[0119] The light-emitting elements 2250a and 2250b each include the substrate 2220 provided with an optical element 2224B, an optical element 2224G, and an optical element 2224R in the direction in which light emitted from the region 2222B, light emitted from the region 2222G, and light emitted from the region 2222R are taken out. The light emitted from each region is emitted to the outside of the light-emitting element via each optical element. In other words, the light from the region 2222B, the light from the region 2222G, and the light from the region 2222R are emitted via the optical element 2224B, the optical element 2224G, and the optical element 2224R, respectively.

[0120] The optical elements 2224B, 2224G, and 2224R each have a function of selectively transmitting light of a specific color of the incident light. For example, the light emitted from region 2222B via optical element 2224B is blue light, the light emitted from region 2222G via optical element 2224G is green light, and the light emitted from region 2222R via optical element 2224R is red light.

[0121] It should be noted that in Fig. 49A and Fig. 49B blue light (B), green light (G) and red light (R) emitted from the regions via the optical elements are schematically represented by arrows made of dashed lines. Fig. 49A is a top-emission light-emitting element, and the light-emitting element 2250a shown in Fig.Light-emitting element 2250b shown in Figure 49B is a bottom-emission light-emitting element.

[0122] An opaque layer 2223 is provided between the optical elements. The opaque layer 2223 has a function of blocking light emitted from adjacent regions. Note that a structure without the opaque layer 2223 may also be employed. A structure in which one or more of the optical elements 2224B, 2224G, and 2224R is / are not provided may be employed. With the structure in which the optical element 2224B, the optical element 2224G, or the optical element 2224R is not provided, the extraction efficiency of the light emitted from the light-emitting element can be increased.

[0123] The charge generation layer 2115 may be formed with a material obtained by adding an electron acceptor (Acceptor) to a hole transport material or a material obtained by adding an electron donor (Donor) to an electron transport material.

[0124] To reduce the operating voltage of the light-emitting element, it is preferable to lower a barrier for electron injection from the charge generation layer 2115 to the electron transport layer 2113 so that the electrons generated in the charge generation layer 2115 are smoothly injected and transported to the electron transport layer 2113. Therefore, the electron injection layer 2130 is preferably provided between the charge generation layer 2115 and the electron transport layer 2113. The electron injection layer 2119 and the electron injection layer 2130 are required to have a high electron injection property, and accordingly, an alkali metal such as lithium (Li) or cesium (Cs), a compound of an alkali metal, an alkaline earth metal such as calcium (Ca), or a compound of an alkaline earth metal is used for the electron injection layers 2119 and 2130.However, in the case where the metal or compound is used for the electron injection layer 2130, as in . Fig. 50A and Fig. 50B, when current flows in the region 2222G by applying a voltage between the electrode 2103 and the electrode 2102, the current also flows in the regions 2222B and 2222R adjacent to the region 2222G through the electron injection layer 2130 and the electron transport layer 2113, and in some cases, light is emitted not only from the region 2222G but also from the regions 2222B and 2222R adjacent to the region 2222G (this phenomenon is referred to as crosstalk in some cases). It should be noted that in Fig. 50A and Fig. 50B the current flowing in the regions 2222G, 2222R and 2222B is indicated by a solid arrow.

[0125] In the case where the crosstalk occurs in the light-emitting elements as described above, the light is emitted not only from a desired region (e.g., the region 2222G) but also from other regions (e.g., the regions 2222B and 2222R), which in some cases results in a reduction in the color purity or the intensity of the light emitted from the light-emitting elements 2250a and 2250b.

[0126] One cause of crosstalk is the diffusion of an alkali metal, an alkaline earth metal, or a compound of an alkali metal or an alkaline earth metal from the electron-injection layer 2130, which is disposed between the charge generation layer 2115 and the electron-transport layer 2113, into the electron-transport layer 2113, which increases the conductivity of the electron-transport layer 2113 (especially the conductivity in a direction perpendicular to the voltage application direction). In particular, a metal with a small atomic number, such as Li or Ca, or a compound thereof in the electron-injection layer 2130, is easily diffused into the electron-transport layer 2113. Therefore, it is preferable that an alkali metal and an alkaline earth metal are not included in the electron-injection layer 2130 to suppress crosstalk.On the other hand, when an alkali metal, an alkaline earth metal, or a compound of an alkali metal or an alkaline earth metal is not contained in the electron injection layer 2130, a barrier to electron injection from the charge generation layer 2115 into the electron transport layer 2113 is increased, and electrons are not easily injected into the electron transport layer 2113, which in some cases leads to an increase in the operating voltage or a decrease in the emission efficiency of the light-emitting element.

[0127] Thus, in order to reduce the operating voltage of the light-emitting element, increase the emission efficiency of the light-emitting element, and suppress crosstalk, a metal with high electron injection property that does not easily diffuse is preferably used for the electron injection layer 2130. It is preferable to use a metal with a long atomic radius as the metal that does not easily diffuse and is used for the electron injection layer 2130. Furthermore, a metal with a large atomic weight is preferably used.

[0128] However, if a metal with a long atomic radius or large atomic weight that does not diffuse easily is used for the electron injection layer 2130, a barrier to electron injection is formed between the charge generation layer 2115 and the electron transport layer 2113, which in some cases causes an increase in the operating voltage and a decrease in the emission efficiency of the light-emitting element.

[0129] In view of this, the present inventors have found that when the composite material of the compound and the transition metal forming SOMO in combination is used for the electron injection layer 2130 adjacent to the charge generation layer 2115 in the light-emitting element, the light-emitting element can have a favorable electron injection property and the crosstalk in the light-emitting element is suppressed.

[0130] The light-emitting element of one embodiment of the present invention is a light-emitting element in which a plurality of light-emitting units are provided, and the electron injection layer 2130 is provided with a composite material of a transition metal and an organic compound having an unshared electron pair between the light-emitting units.

[0131] A transition metal has a large atomic weight and is not easily diffused in an organic compound, so that a light-emitting element can be provided in which crosstalk is suppressed.

[0132] It should be noted that since the organic compound with an unshared electron pair transports electrons, the organic compound with an unshared electron pair preferably includes at least one π-conjugated system. In this case, an atom with a π electron (Pz orbital) preferably includes the unshared electron pair, or an atom bonded (adjacent) to an atom with a π electron (Pz orbital) preferably includes the unshared electron pair.

[0133] In the case where a composite material of the transition metal 132 and the compound 131, which is Fig. 1A to Fig.1C is included in the electron injection layer 2130, the HOMO level formed by interaction between the compound 131 and an atom of the transition metal 132 is preferably approximately equal to the HOMO level of the original compound 131. In the case where an organic compound having a function of transporting an electron is used for the compound 131, the HOMO level of the compound 131 is low, and holes are not easily injected into the compound 131.Therefore, in the case where the HOMO level formed by the interaction between the compound 131 and the transition metal 132 is approximately equal to the HOMO level of the original compound 131, a barrier to hole injection between the electron injection layer 2130 and the charge generation layer 2115 is high; accordingly, a hole does not easily penetrate from the electron injection layer 2130 to the charge generation layer 2115, resulting in an improvement in the charge carrier balance in the light-emitting element.

[0134] SOMO is a single-electron orbital; in the case where the above-described composite material is used for the electron injection layer 2119 and the electron injection layer 2130, by applying a voltage to the light-emitting element 2250a and the light-emitting element 2250b, an electron in SOMO serves as a charge carrier in the light-emitting element and is transported to the electron transport layer 2113 and the light-emitting layer 2140. Furthermore, electrons can be easily injected from the charge generation layer 2115 into the electron injection layer 2130. That is, when the electron injection layer 2130 includes materials that form SOMO in combination, electrons can be easily injected from the charge generation layer 2115 into the light-emitting device 2106. The SOMO level is preferably lower than the LUMO level of compound 2131.Accordingly, the LUMO level of compound 131 is preferably high. Specifically, the LUMO level of compound 131 is preferably higher than or equal to -3.6 eV and lower than or equal to -2.3 eV. When an organic compound having such a LUMO level and a transition metal are mixed, an SOMO level suitable for electron injection is formed by the interaction between the organic compound and the transition metal, whereby a barrier to electron injection between the electron injection layer 2130 and the charge generation layer 2115 can be lowered.

[0135] Due to the formation of SOMO through the interaction between compound 131 and transition metal 132, an unpaired electron is formed in electron injection layer 130. Thus, the formation of SOMO can be observed by ESR. To favorably inject electrons from charge generation layer 2115 into light-emitting layer 2140, the spin density originating from SOMO is preferably greater than or equal to 1 × 10 16 Spins / cm 3 , more preferably greater than or equal to 5 × 10 16 Spins / cm 3 , even more preferably greater than or equal to 1 × 10 17 Spins / cm 3 . To suppress crosstalk, the spin density originating from SOMO is preferably less than or equal to 5 × 10 17 Spins / cm 3 . <Komponenten des Licht emittierenden Elements>

[0136] The components of the Fig. 1A to Fig. 1C, Fig. 2A and Fig. 2B, Fig.49A and Fig. 49B and Fig. 50A and Fig. The light-emitting elements shown in Figure 50B are described in detail below.

[0144] < <elektroneninjektionsschicht>>

[0137] The electron-injection layers 130, 2130, and 2119 are layers each containing a substance with a high electron-injection property, and the above-described composite material of the transition metal and the organic compound having an unshared electron pair can be suitably used for the layers. As the organic compound for the electron-injection layers 130, 2130, and 2119, a material with a high electron-transport property is preferably used, and specifically, for example, a metal complex or a heteroaromatic compound described below can be used.

[0138] For the electron-injection layer 130, the electron-injection layer 2130, and the electron-injection layer 2119, a metal complex containing a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand, a pyridine derivative, a pyrimidine derivative, a pyrazine derivative, a triazine derivative, an oxadiazole derivative, a triazole derivative, a phenanthroline derivative, or the like can be used. Specifically, a metal complex such as Alq3, Almq3, BeBq2, Balq, bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), or bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ) can be used. Furthermore, one of the following can be used: heterocyclic compounds with azole skeletons, such as2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 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-carbazole (abbreviation: CO11), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: p-EtTAZ), 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs), 2,2',2"-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI) and 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II); heterocyclic compounds with diazine skeletons, such as2-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(Dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-Carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4-(3,6-Diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), 6-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm) and 4-{3-[3'-(9H-carbazol-9-yl)]biphenyl-3-yl}benzofuro[3,2-d]pyrimidine (abbreviation: 4mCzBPBfpm); heterocyclic compounds with triazine skeletons, such as2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2,4,6-tris[3'-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz) and 2,4,6-tris(2-pyridyl)-1,3,5-triazine (abbreviation: 2Py3Tzn); and heterocyclic compounds with pyridine skeletons, such as. E.g., 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), bathocuproine (abbreviation: BCP), and 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen). Among the materials described above, heterocyclic compounds with diazine skeletons and triazine skeletons and heterocyclic compounds with pyridine skeletons exhibit high reliability and are therefore preferable.In particular, heterocyclic compounds with diazine (pyrimidine or pyrazine) skeletons and those with triazine skeletons exhibit high electron transport properties and contribute to a reduction in operating voltage. The substances mentioned here are mainly those with an electron mobility of 1 × 10 -6 cm 2 / Vs or higher. Note that other substances may also be used for the electron injection layer 130, the electron injection layer 2130, and the electron injection layer 2119 as long as their electron transport properties are higher than their hole transport properties. < <lochinjektionsschicht>>

[0139] The hole injection layers 111 and 2111 each have a function of promoting hole injection by reducing a barrier to hole injection from one of the pair of electrodes (the electrode 101 or the electrode 102 or the electrode 2101 or the electrode 2102), and the hole injection layer 2116 has a function of promoting hole injection by reducing a barrier to hole injection from the charge generation layer 2115. The hole injection layers 111, 2111, and 2116 are each formed using, for example, a transition metal oxide, a phthalocyanine derivative, or an aromatic amine. As the transition metal oxide, molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide, or the like can be specified. Phthalocyanine, metal phthalocyanine or the like can be specified as the phthalocyanine derivative.As the aromatic amine, a benzidine derivative, a phenylenediamine derivative, or the like can be specified. It is also possible to use a high-molecular compound such as polythiophene or polyaniline; a typical example is poly(ethylenedioxythiophene) / poly(styrenesulfonic acid), which is a self-doped polythiophene.

[0140] For each of the hole-injection layers 111, 2111, and 2116, a layer containing a composite material of a hole-transport material and a material having a property of accepting electrons from the hole-transport material may also be used. Alternatively, a layer arrangement of a layer containing a material having an electron-accepting property and a layer containing a hole-transport material may also be used. In a stable state or in the presence of an electric field, electric charges can be transferred between these materials. As examples of the material having a property of accepting electrons, organic acceptors such as a quinodimethane derivative, a chloranil derivative, and a hexaazatriphenylene derivative can be cited.A specific example is a compound having an electron-withdrawing group (a halogen group or a cyano group), such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, or 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN). Alternatively, a transition metal oxide such as an oxide of a Group 4 to Group 8 metal can be used. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, or the like can be used. In particular, molybdenum oxide is preferred because it is stable in air, has low hygroscopicity, and is easy to handle.

[0141] A material with a property of transporting more holes than electrons can be used as a hole transport material, whereby a material with a hole mobility of 1 × 10 -6 cm 2 / Vs or higher is preferable. Specifically, any of an aromatic amine, a carbazole derivative, an aromatic hydrocarbon, a stilbene derivative, and the like, which have been described as examples of the hole-transport material that can be used in the light-emitting layer 140, can be used. Furthermore, the hole-transport material may be a high-molecular compound.

[0142] Other examples of hole transport materials include aromatic hydrocarbons such as: B. 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9,10-di(1-naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene (abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene (abbreviation: DMNA), 2-tert-Butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene, 2,3,6,7-Tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9'-bianthryl, 10,10'-diphenyl-9,9'-bianthryl, 10,10'-bis(2-phenylphenyl)-9,9'-bianthryl, 10,10'-Bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bianthryl, anthracene, tetracene, rubrene, perylene and 2,5,8,11-tetra(tert-butyl)perylene.Other examples include pentacene, coronene, and the like. The aromatic hydrocarbon, which has a hole mobility of 1 × 10 -6 cm 2 / Vs or higher and 14 to 42 carbon atoms is particularly preferred.

[0143] The aromatic hydrocarbon may have a vinyl skeleton. Examples of aromatic hydrocarbons with a vinyl group include 4,4'-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi), 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA), and the like.

[0144] Further examples include thiophene compounds, furan compounds, fluorene compounds, triphenylene compounds, phenanthrene compounds and the like, such as: B. 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II), 4,4',4"-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 1,3,5-tri(dibenzothiophen-4-yl)benzene (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-phenyldibenzothiophene (abbreviation: DBTFLP-IV) and 4-[3-(triphenylen-2-yl)phenyl]dibenzothiophene (abbreviation: mDBTPTp-II). Among the above compounds, compounds comprising a pyrrole skeleton, a furan skeleton, a thiophene skeleton, or an aromatic amine skeleton are preferred due to their high stability and reliability.In addition, the connections with such frameworks have a high hole transport property, which contributes to a reduction in the operating voltage. < <lochtransportschicht>>

[0145] The hole-transport layers 112, 2112, and 2117 each include a hole-transport material and can be formed using any of the materials given as examples of the materials of the hole-injection layers 111, 2111, and 2116. The hole-transport layers 112, 2112, and 2117 each have a function of transporting a hole injected from the hole-injection layers 111, 2111, and 2116 to the light-emitting layers 140, 2140, and 2170.

[0146] In this case, a hole-transport material whose HOMO level lies between the LUMO level of the acceptor material of the hole-injection layer 111 and the HOMO level of the material of the light-emitting layer 140 is preferably used for the hole-transport layer 112. Likewise, a hole-transport material whose HOMO level lies between the LUMO level of the acceptor material of the hole-injection layer 2111 and the HOMO level of the material of the light-emitting layer 2140 is preferably used for the hole-transport layer 2112. Each of the hole-transport layers 112, 2112, and 2117 is not limited to a single layer and may include a layer arrangement of two or more layers.In this case, it is preferable to stack hole transport materials to lower the HOMO level so that the HOMO levels of the hole transport materials on the light-emitting layer 140 side, the light-emitting layer 2140 side, and the light-emitting layer 2170 side are lower than those of the hole transport materials on the hole-injection layer 111 side, the hole-injection layer 2111 side, and the hole-injection layer 2116 side, respectively.In the case where the hole transport layers 112, 2112 and 2117 each include a layer arrangement of two or more layers to smoothly transport holes, the difference in HOMO level between the hole transport materials is preferably greater than or equal to 0 eV and less than or equal to 0.5 eV, more preferably greater than or equal to 0 eV and less than or equal to 0.3 eV, even more preferably greater than or equal to 0 eV and less than or equal to 0.2 eV.

[0147] Examples of the hole transport material include compounds with aromatic amine frameworks, such as4,4'-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N'-Bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4'-Bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-Phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-Phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-Phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-Diphenyl-4"-(9-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: PCBNBB), 9,9-Dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF) or N-Phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF), a compound with a carbazole skeleton, such as1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP) or 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), a compound with a thiophene skeleton, such as. B. 4,4',4"-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III) or 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), as well as a compound with a furan skeleton, such as 4,4',4"-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) or 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II).Among the above materials, a compound with an aromatic amine skeleton and a compound with a carbazole skeleton are preferred because these compounds are highly reliable and exhibit high hole-transport properties, thus contributing to a reduction in operating voltage. Hole-transport materials can be selected from various substances as well as from the hole-transport materials listed above.

[0148] Furthermore, examples of the substance with a high hole transport property include compounds with aromatic amine skeletons, such as: B. 3-[4-(1-Naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 3-[4-(9-Phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn), 4-Phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-Di(1-naphthyl)-4"-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 4-Phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl)amine (abbreviation: PCA1BP), 3,3'-Bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), N-[4-(9H-Carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline (abbreviation: YGA1BP), 1,3,5-Tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II), 4,4',4"-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-[3-(Triphenylen-2-yl)phenyl]dibenzothiophene (abbreviation: mDBTPTp-II), 4,4'-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4',4"-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), 4,4',4"-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4',4"-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA) and 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB); 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1); 3,6-Bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2); 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1); and the like. Further examples include carbazole compounds such as 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP) and 1,3,5-Tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB); amine compounds; dibenzothiophene compounds; dibenzofuran compounds; fluorene compounds; triphenylene compounds; and phenanthrene compounds. The substances listed here are mainly substances that have a hole mobility of 1 × 10, -6 cm 2 / Vs or higher. It should be noted that any other material can be used as long as it has the property of transporting more holes than electrons.

[0149] It should be noted that any of these compounds that can be used for the hole transport layer can also be used for the hole injection layer. < <ladungserzeugungsschicht>>

[0150] Each of the charge generation layers 160 and 2115 may have either a structure in which an acceptor substance, which is an electron acceptor, is added to a hole-transporting material, or a structure in which a donor substance, which is an electron donor, is added to an electron-transporting material. Alternatively, both of these structures may be arranged one above the other.

[0151] In the case where each of the charge generation layers 160 and 2115 contains a composite material of an organic compound and an acceptor substance, the composite material that can be used for the above-described hole injection layer 111 can be used for the composite material. As the organic compound, various compounds such as an aromatic amine compound, a carbazole compound, an aromatic hydrocarbon, and a high-molecular compound (such as an oligomer, a dendrimer, or a polymer) can be used. A substance having a hole mobility of 1 × 10 -6 cm 2 / Vs or higher is preferably used as the organic compound. Note that any other material can be used as long as it has a property of transporting more holes than electrons. Since the composite material of an organic compound and an acceptor substance has excellent charge injection and charge transport properties, low-voltage operation or low-current operation can be achieved. Note that when surfaces of light-emitting units on the anode side are in contact with the charge generation layers 160 and 2115, the charge generation layers 160 and 2115 can also serve as a hole injection layer or a hole transport layer of the light-emitting unit, respectively; therefore, a hole injection layer or a hole transport layer need not necessarily be included in the light-emitting unit.

[0152] The charge generation layers 160 and 2115 may each have a multilayer structure composed of a layer containing the composite material of an organic compound and an acceptor substance and a layer containing another material. For example, the charge generation layers 160 and 2115 may each be formed by combining a layer containing the composite material of an organic compound and an acceptor substance with a layer containing a compound selected from materials having an electron-donating property and a compound having a high electron-transporting property. Furthermore, the charge generation layers 160 and 2115 may each be formed using a combination of a layer containing the composite material of an organic compound and an acceptor substance with a layer including a transparent conductive material.

[0153] Note that in terms of light extraction efficiency, the charge generation layers 160 and 2115 preferentially transmit visible light (specifically, the charge generation layers 160 and 2115 each have a visible light transmittance higher than or equal to 40%). The charge generation layers 160 and 2115 operate even if they have a lower conductivity than the pair of electrodes (the electrodes 2101, 2102, 2103, and 2104).

[0154] By forming the charge generation layers 160 and 2115 using any of the above materials, an increase in the driving voltage caused by the stacking of the light-emitting layers can be suppressed. <<Licht emittierende Schicht> >

[0155] The light-emitting layers 140, 2140, and 2170 each include a light-emitting material having a function of emitting at least one of violet light, blue light, blue-green light, green light, yellow-green light, yellow light, orange light, and red light. Furthermore, the light-emitting layers 140, 2140, and 2170 each include an electron-transport material and / or a hole-transport material as a host material in addition to the light-emitting material.

[0156] Any light-emitting substance that converts singlet excitation energy into luminescence and any light-emitting substance that converts triplet excitation energy into luminescence can be used as the light-emitting material. Examples of the light-emitting substance are given below.

[0157] Examples of the light-emitting substance that can convert singlet excitation energy into luminescence include substances that emit fluorescence (a fluorescent compound). Although there is no particular limitation on the fluorescent compound, it is preferable to use an anthracene derivative, a tetracene derivative, a chrysene derivative, a phenanthrene derivative, a pyrene derivative, a perylene derivative, a stilbene derivative, an acridone derivative, a coumarin derivative, a phenoxazine derivative, a phenothiazine derivative, or the like. For example, one of the following substances can be used.

[0158] Specific examples of the fluorescent compound include 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-Bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-bis(4-tert-butylphenyl)pyrene-1,6-diamine (abbreviation: 1,6tBu-FLPAPrn), N,N'-Diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-3,8-dicyclohexylpyrene-1,6-diamine (abbreviation: ch-1,6FLPAPrn), N,N'-(Pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-03), N,N'-Bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (Abbreviation: YGA2S), 4-(9H-Carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (Abbreviation: YGAPA), 4-(9H-Carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra(tert-butyl)perylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N''-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA), N,9-Diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-Diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N',N',N'',N'',N''',N'''-Octaphenyldibenzo[g,p]chrysen-2,7,10,15-tetraamine (abbreviation: DBC1), Coumarin 30, N-(9,10-Diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis(1,1'-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracene-9-amine (abbreviation: DPhAPhA), coumarin 6, coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (abbreviation: TBRb), Nile Red, 5,12-Bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(Dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-Methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N',N'-Tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-Diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2,6-Bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-Bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM) and 5,10,15,20-tetraphenylbisbenzo[5,6]indeno[1,2,3-cd:1',2',3'-Im]perylene.

[0159] As an example of the light-emitting substance that can convert triplet excitation energy into luminescence, a substance that emits phosphorescence (a phosphorescent compound) can be cited. An iridium-, rhodium-, or platinum-based organometallic complex or metal complex can be used as the phosphorescent compound. Further, a platinum complex containing a porphyrin ligand, an organoiridium complex, and the like can be cited. In particular, an organoiridium complex such as an iridium-based ortho-metalated complex is preferred. As the ortho-metalated ligand, a 4H-triazole ligand, a 1H-triazole ligand, an imidazole ligand, a pyridine ligand, a pyrimidine ligand, a pyrazine ligand, an isoquinoline ligand, or the like can be cited.In this case, the phosphorescent compound exhibits an absorption band based on a triplet MLCT (metal to ligand charge transfer) transition.

[0160] Examples of the substance exhibiting an emission peak in the blue or green wavelength range include organometallic iridium complexes having a 4H-triazole skeleton, such as: B. Tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: Ir(mpptz-dmp)3), Tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Mptz)3), Tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPrptz-3b)3) and Tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPr5btz)3); organometallic iridium complexes with a 1H-triazole framework, such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(Mptz1-mp)3) and tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Prptz1-Me)3); organometallic iridium complexes with an imidazole framework, such asfac-Tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: Ir(iPrpmi)3) and tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: Ir(dmpimpt-Me)3); and organometallic iridium complexes in which a phenylpyridine derivative with an electron-withdrawing group is a ligand, such as 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(III)picolinate (abbreviation: Flrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C 2' }iridium(III)picolinate (abbreviation: Ir(CF3ppy)2(pic)) and bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2' ]iridium(III) acetylacetonate (abbreviation: Flr(acac)). Among the above-mentioned materials, organometallic iridium complexes comprising a five-membered nitrogen-containing heterocyclic framework, such as a 4H-triazole framework, a 1H-triazole framework, or an imidazole framework, exhibit high triplet excitation energy, reliability, and emission efficiency and are therefore particularly preferred.

[0161] Examples of the substance exhibiting an emission peak in the green or yellow wavelength range include organometallic iridium complexes with a pyrimidine skeleton, such asTris(4-methyl-6-phenylpyrimidinato)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(III) (abbreviation: Ir(mppm)2(acac)), (Acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm)2(acac)), (Acetylacetonato)bis[4-(2-norbornyl)-6-phenylpyrimidinato]iridium(III) (abbreviation: Ir(nbppm)2(acac)), (Acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: Ir(mpmppm)2(acac)), (Acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}iridium(III) (abbreviation: Ir(dmppm-dmp)2(acac)) and (Acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: Ir(dppm)2(acac)); organometallic iridium complexes with a pyrazine framework, such as(Acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-Me)2(acac)) and (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-iPr)2(acac)); organometallic iridium complexes with a pyridine framework, such as tris(2-phenylpyridinato-N,C 2' )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 (abbreviation: Ir(bzq)2(acac)), tris(benzo[h]quinolinato)iridium(III) (abbreviation: Ir(bzq)3), tris(2-phenylquinolinato-N, C 2' )iridium(III) (abbreviation: Ir(pq)3) and bis(2-phenylquinolinato-N,C 2' )iridium(III)acetylacetonate (abbreviation: Ir(pq)2(acac)); organometallic iridium complexes, such as bis(2,4-diphenyl-1,3-oxazolato-N, C 2' )iridium(III)acetylacetonate (abbreviation: Ir(dpo)2(acac)), bis{2-[4'-(perfluorophenyl)phenyl]pyridinato-N,C 2'}iridium(III)acetylacetonate (abbreviation: Ir(p-PF-ph)2(acac)), and bis(2-phenylbenzothiazolato-N, C 2' )iridium(III) acetylacetonate (abbreviation: Ir(bt)2(acac)); and a rare earth metal complex, such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: Tb(acac)3(Phen)). Among the materials listed above, the organometallic iridium complexes with a pyrimidine framework exhibit very high reliability and very high emission efficiency and are therefore particularly preferred.

[0162] Examples of the substance exhibiting an emission peak in the yellow or red wavelength range include organometallic iridium complexes having a pyrimidine skeleton, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: Ir(5mdppm)2(dibm)), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(5mdppm)2(dpm)) and bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(d1npm)2(dpm)); organometallic iridium complexes having a pyrazine skeleton, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: Ir(5mdppm)2(dpm)). B. (Acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: Ir(tppr)2(acac)), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: Ir(tppr)2(dpm)) and (Acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: Ir(Fdpq)2(acac)); organometallic iridium complexes with a pyridine framework, such as tris(1-phenylisoquinolinato-N,C 2' )iridium(III) (abbreviation: Ir(piq)3) and bis(1-phenylisoquinolinato-N,C 2' )iridium(III) acetylacetonate (abbreviation: Ir(piq)2(acac)); a platinum complex, such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviation: PtOEP); and rare earth metal complexes, such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: Eu(DBM)3(Phen)) and tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: Eu(TTA)3(Phen)). Among the materials listed above, organometallic iridium complexes with a pyrimidine framework exhibit very high reliability and very high emission efficiency and are therefore particularly preferred. Furthermore, red light emission with favorable chromaticity can be obtained from an organometallic iridium complex with a pyrazine framework.

[0163] As an example of a material that can convert triplet excitation energy into light emission, in addition to a phosphorescent compound, a thermally activated delayed fluorescence (TADF) material can be cited. Accordingly, the term "phosphorescent compound" can be replaced with the term "thermally activated delayed fluorescence compound" in the description. The thermally activated delayed fluorescence compound is a material that has a small difference between the singlet excitation energy level and the triplet excitation energy level and a function of converting triplet excitation energy into singlet excitation energy through reverse intersystem crossing.The thermally activated delayed fluorescent material can thus upconvert a triplet excitation state to a singlet excitation state using a small amount of thermal energy (i.e., reverse intersystem crossing is thus possible) and efficiently emit light (fluorescence) from the singlet excitation state. The TADF is efficiently obtained under the condition where the difference between the singlet excitation energy level and the triplet excitation energy level is preferably greater than 0 eV and less than or equal to 0.3 eV, more preferably greater than 0 eV and less than or equal to 0.2 eV, and even more preferably greater than 0 eV and less than or equal to 0.1 eV.

[0164] For example, in the case where the thermally activated delayed fluorescent compound consists of one type of material, any of the following materials can be used.

[0165] First, a fullerene, a derivative thereof, an acridine derivative such as proflavin, eosin, and the like can be cited. Other examples include a metal-containing porphyrin, such as a porphyrin containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd). Examples of the metal-containing porphyrin include a protoporphyrin-tin fluoride complex (SnF2(Proto IX)), a mesoporphyrin-tin fluoride complex (SnF2(Meso IX)), a hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), a coproporphyrin-tetramethyl ester-tin fluoride complex (SnF2(Copro III-4Me)), an octaethylporphyrin-tin fluoride complex (SnF2(OEP)), an etioporphyrin-tin fluoride complex (SnF2(Etio I)), and an octaethylporphyrin-platinum chloride complex (PtCl2OEP).

[0166] For the thermally activated delayed fluorescent compound composed of one type of material, a heterocyclic compound comprising a π-electron-rich heteroaromatic framework and a π-electron-poor heteroaromatic framework can also be used. In particular, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-Dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS) or 10-phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (abbreviation: ACRSA) can be used.The heterocyclic compound is preferably used because it has the π-electron-rich heteroaromatic skeleton and the π-electron-poor heteroaromatic skeleton; therefore, the electron-transport property and the hole-transport property are high. Among the π-electron-poor heteroaromatic skeletons, a diazine skeleton (a pyrimidine skeleton, a pyrazine skeleton, or a pyridazine skeleton) and a triazine skeleton have high stability and high reliability and are particularly preferable. Among the π-electron-rich heteroaromatic skeletons, an acridine skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a furan skeleton, a thiophene skeleton, and a pyrrole skeleton have high stability and high reliability; therefore, one or more of these skeletons is preferably included. As a pyrrole skeleton, an indole skeleton, a carbazole skeleton or a 9-phenyl-3,3'-bi-9H-carbazole skeleton is particularly preferable.It should be noted that a substance in which the π-electron-rich heteroaromatic skeleton is directly bonded to the π-electron-poor heteroaromatic skeleton is particularly preferred because both the donor property of the π-electron-rich heteroaromatic skeleton and the acceptor property of the π-electron-poor heteroaromatic skeleton are increased and the difference between the singlet excitation energy level and the triplet excitation energy level becomes small.

[0167] The material emitting thermally activated delayed fluorescence may be a material capable of forming a singlet excited state from a triplet excited state through reverse intersystem crossing, or may be a combination of a plurality of materials forming an exciplex.

[0168] As the host material used for the light-emitting layers 140, 2140 and 2170, hole transport materials and electron transport materials can be used.

[0169] Although there is no particular limitation on a material that can be used as the host material of the light-emitting layer, for example, any of the following substances can be used as the host material: metal complexes such as: B. Tris(8-quinolinolato)aluminum(III) (abbreviation: Alq3), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO) and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ); heterocyclic compounds, such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), bathocuproine (abbreviation: BCP) and 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11); and aromatic amine compounds, such as B. 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), and 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB). In addition, condensed polycyclic aromatic compounds such as anthracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives, and dibenzo[g,p]chrysene derivatives can be used.Specific examples of the condensed polycyclic aromatic compound include 9,10-diphenylanthracene (abbreviation: DPAnth), N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine (abbreviation: DPhPA), YGAPA, PCAPA, N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine (abbreviation: PCAPBA), 2PCAPA, 6,12-dimethoxy-5,11-diphenylchrysene, DBC1, 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: DPCzPA), 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 9,9'-bianthryl (abbreviation: BANT), 9,9'-(stilbene-3,3'-diyl)diphenanthrene (abbreviation: DPNS), 9,9'-(stilbene-4,4'-diyl)diphenanthrene (abbreviation: DPNS2) and 1,3,5-tri(1-pyrenyl)benzene (abbreviation: TPB3).One or more substances with a larger energy gap than the above-described light-emitting material are preferably selected from these substances and various substances. In the case where the light-emitting material is a phosphorescent compound, a substance with a triplet excitation energy higher than that of the light-emitting material is preferably selected as the host material.

[0170] In the case where a variety of materials are used as the host material of the light-emitting layer, a combination of two types of compounds forming an exciplex is preferably used. In this case, various charge-transporting materials can be used appropriately. To efficiently form an exciplex, it is particularly advantageous to combine an electron-transporting material and a hole-transporting material.

[0171] This is because, when a combination of a material with electron-transport properties and a material with hole-transport properties forming an exciplex is used as the host material, the charge carrier balance between holes and electrons in the light-emitting layer can be easily optimized by adjusting the mixing ratio of the material with electron-transport properties and the material with hole-transport properties. Optimizing the charge carrier balance between holes and electrons in the light-emitting layer can prevent a region where electrons and holes recombine on one side of the light-emitting layer. By preventing the region where electrons and holes recombine on one side, the reliability of the light-emitting element can be improved.

[0172] As the electron-transport material, a zinc- or aluminum-containing metal complex, a π-electron-deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound, or the like can be used. Specifically, one of the following materials can be used: bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ); heterocyclic compounds with azole skeletons, such as2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-Biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-Bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-Phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2',2''-(1,3,5-Benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI) and 2-[3-(Dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II); heterocyclic compounds with diazine skeletons, such as2-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(Dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-Carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq); 2-[4-(3,6-Diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), 6-[3-(Dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 4,6-Bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-Bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4,6-Bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm) and 4-{3-[3'-(9H-carbazol-9-yl)]biphenyl-3-yl}benzofuro[3,2-d]pyrimidine (abbreviation: 4mCzBPBfpm), heterocyclic compounds with triazine skeletons, such as2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2,4,6-tris[3'-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz) and 2,4,6-tris(2-pyridyl)-1,3,5-triazine (abbreviation: 2Py3Tz) and heterocyclic compounds with pyridine skeletons, such as. B. 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy) and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB). Among the materials described above, heterocyclic compounds with diazine and triazine skeletons and heterocyclic compounds with pyridine skeletons are highly reliable and thus preferable. Heterocyclic compounds with diazine (pyrimidine or pyrazine) and triazine skeletons exhibit high electron transport properties and contribute to a reduction in operating voltage.

[0173] As the hole-transport material, a π-electron-rich heteroaromatic compound (e.g., a carbazole derivative or an indole derivative), an aromatic amine compound, or the like can be advantageously used. Specific examples include compounds with aromatic amine skeletons, such as phenyl ethers. B. 2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), 4,4',4''-tris[N-(1-naphthyl)-N-phenylamino]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: DPNF), N,N',N''-Triphenyl-N,N',N''-tris(9-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-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPASF), N,N'-Bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F), 4,4'-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N'-Bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4'-Bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), 4,4'-Bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-Phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (Abbreviation: BPAFLP), 4-Phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (Abbreviation: mBPAFLP), N-(9,9-Dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine (Abbreviation: DFLADFL), 3-[N-(9-Phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (Abbreviation: PCzPCA1), 3-[N-(4-Diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (Abbreviation: PCzDPA1), 3,6-Bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (Abbreviation: PCzDPA2), N,N'-Bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (abbreviation: DNTPD), 3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole (abbreviation: PCzTPN2), 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-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: PCBNBB), 3-[N-(1-Naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1), 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), N-(4-Biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine (abbreviation: PCBiF) and N-(1,1'-Biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), compounds with carbazole skeletons, such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP) and 9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carbazole (abbreviation: PCCP), compounds with thiophene skeletons, such as B. 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV) and compounds with furan skeletons, such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl} dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above materials, a compound with an aromatic amine skeleton and a compound with a carbazole skeleton are preferred because these compounds are highly reliable and exhibit high hole-transport properties, which contributes to a reduction in operating voltage.

[0174] It should be noted that the combination of materials forming an exciplex and used as a host material is not limited to the compounds described above, as long as they can transport carriers, the combination can form an exciplex, and the light emission of the exciplex overlaps with an absorption band on the longest wavelength side in an absorption spectrum of a light-emitting material (an absorption corresponding to the transition of the light-emitting material from the singlet ground state to the singlet excited state), and other materials can be used.

[0175] A thermally activated, delayed fluorescent material can be used as the host material of the light-emitting layer.

[0176] The electron-transport material used for the light-emitting layer can be the same as the electron-transport material used for the electron-injection layer. This simplifies the fabrication of the light-emitting element and reduces the manufacturing cost of the light-emitting element. < <elektronentransportschicht>>

[0177] The electron-transport layers 118, 2113, and 2118 each contain a substance having a high electron-transport property. Examples of the substance having a high electron-transport property used for the electron-transport layers 118, 2113, and 2118 include metal complexes having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, and a thiazole ligand; an oxadiazole derivative; a triazole derivative; a phenanthroline derivative; a pyridine derivative; and a bipyridine derivative. Specifically, any of the metal complexes and heteroaromatic compounds given as examples of the compound that can be used for the electron-injection layers 130, 2130, and 2119 can be used.It should be noted that other substances can also be used for the electron transport layers 118, 2113 and 2118 as long as their electron transport properties are higher than their hole transport properties.

[0178] The electron transport layers 118, 2113 and 2118 are not limited to a single layer and may be a stacked arrangement of two or more layers containing the substances specified above.

[0179] A layer that controls the transport of electron carriers can be provided between the electron-transport layer 118 and the light-emitting layer 140, between the electron-transport layer 2113 and the light-emitting layer 2140, and between the electron-transport layer 2118 and the light-emitting layer 2170. This layer is formed by adding a small amount of a substance with a high electron-capture property to the above-described material with a high electron-transport property, and can regulate the carrier balance by suppressing the transport of electron carriers. Such a structure is very effective for preventing a problem (such as a shortening of the element's lifetime) that occurs when electrons pass through the light-emitting layer.

[0180] The electron-transport material used for the electron-transport layer can be the same as the electron-transport material used for the electron-injection layer. The electron-transport material used for the electron-transport layer can be the same as the electron-transport material used for the light-emitting layer. With this structure, the light-emitting element can be easily manufactured and the manufacturing cost of the light-emitting element can be reduced.

[0181] Note that the hole-injection layer, the hole-transport layer, the light-emitting layer, the electron-transport layer, and the electron-injection layer described above can each be formed by an evaporation method (including a vacuum evaporation method), an inkjet method, a coating method, a gravure printing method, or the like. In addition to the above-mentioned materials, an inorganic compound such as a quantum dot or a high-molecular compound (e.g., an oligomer, a dendrimer, or a polymer) can be used in the hole-injection layer, the hole-transport layer, the light-emitting layer, the electron-transport layer, and the electron-injection layer.

[0182] For example, the quantum dot can be a gelatinous quantum dot, an alloyed quantum dot, a core-shell quantum dot, or a core quantum dot. The quantum dot containing elements belonging to groups 2 and 16, elements belonging to groups 13 and 15, elements belonging to groups 13 and 17, elements belonging to groups 11 and 17, or elements belonging to groups 14 and 15 can be used. Alternatively, the quantum dot containing an element such as cadmium (Cd), selenium (Se), zinc (Zn), sulfur (S), phosphorus (P), indium (In), tellurium (Te), lead (Pb), gallium (Ga), arsenic (As), or aluminum (Al) can be used.

[0183] An example of the liquid medium used for the wet process includes an organic solvent of ketones such as methyl ethyl ketone and cyclohexanone; fatty acid esters such as ethyl acetate; halogenated hydrocarbons such as dichlorobenzene; aromatic hydrocarbons such as toluene, xylene, mesitylene, and cyclohexylbenzene; aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane; dimethylformamide (DMF); dimethyl sulfoxide (DMSO); or the like.

[0184] Examples of the high molecular compound that can be used for the light-emitting layer include a phenylenevinylene (PPV) derivative such as poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (abbreviation: MEH-PPV) or poly(2,5-dioctyl-1,4-phenylenevinylene); a polyfluorene derivative such as poly(ethylene glycol monomethyl ether); B. Poly(9,9-di-n-octylfluorenyl-2,7-diyl) (abbreviation: PF8), poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazole-4,8-diyl)] (abbreviation: F8BT), poly(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(2,2'-bithiophene-5,5'-diyl)] (abbreviation: F8T2), poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-(9,10-anthracene)] or poly[(9,9-dihexylfluorene-2,7-diyl)-alt-(2,5-dimethyl-1,4-phenylene)]; a polyalkylthiophene (PAT) derivative, such as poly(3-hexylthiophene-2,5-diyl) (abbreviation: P3HT); and a polyphenylene derivative. These high-molecular-weight compounds or a high-molecular-weight compound, such asPoly(9-vinylcarbazole) (abbreviation: PVK), poly(2-vinylnaphthalene), or poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (abbreviation: PTAA) can be doped with a low-molecular-weight compound exhibiting light-emitting properties and used for the light-emitting layer. Any of the fluorescent compounds described above can be used as the low-molecular-weight compound exhibiting light-emitting properties. <<Paar von Elektroden> >

[0185] Electrodes 101, 102, 2101, 2102, 2103, and 2104 each serve as the anode or cathode of the light-emitting element. Electrodes 101, 102, 2101, 2102, 2103, and 2104 can each be formed using a metal, an alloy, a conductive compound, a mixture, or a layered arrangement thereof.

[0186] The electrode 101 or the electrode 102 is preferably formed using a conductive material having a function of reflecting light. The electrode 2102 or the electrodes 2101, 2103, and 2104 is / are preferably formed using a conductive material having a function of reflecting light. Examples of the conductive material include aluminum (Al), an alloy containing Al, and the like. Examples of the alloy containing Al include an alloy containing Al and L (L represents one or more of titanium (Ti), neodymium (Nd), nickel (Ni), and lanthanum (La)), such as an alloy containing Al and Ti, and an alloy containing Al, Ni, and La. Aluminum has low resistance and high light reflectivity.Aluminum is abundant in the earth's crust and is inexpensive; therefore, it is possible to reduce the cost of manufacturing a light-emitting element with aluminum. Silver (Ag) can be advantageously used as an electrode material due to its high light reflectivity. In addition, Ag is a Group 11 transition metal, and Ag is preferably used as the cathode of the light-emitting element, in which Ag is used for the electron-injection layer, thereby improving the adhesion between the electrode and the electron-injection layer. Alternatively, for example, an alloy of Ag and N (N represents one or more of yttrium (Y), Nd, magnesium (Mg), ytterbium (Yb), Al, Ti, gallium (Ga), zinc (Zn), indium (In), tungsten (W), manganese (Mn), tin (Sn), iron (Fe), Ni, copper (Cu), palladium (Pd), iridium (Ir), and gold (Au)) can be used.Examples of the silver-containing alloy include an alloy containing silver, palladium, and copper, an alloy containing silver and copper, an alloy containing silver and magnesium, an alloy containing silver and nickel, an alloy containing silver and gold, an alloy containing silver and ytterbium, and the like. In addition, a transition metal such as tungsten, chromium (Cr), molybdenum (Mo), copper, or titanium may be used.

[0187] Light emitted from the light-emitting layer is taken out via the electrode 101 and / or the electrode 102 or via the electrode 2102 and / or the electrodes 2101, 2103, and 2104. Accordingly, at least one of the electrode 101 and the electrode 102, and at least one of the electrode 2102 and a group of the electrodes 2101, 2103, and 2104 are preferably formed using a conductive material having a function of transmitting light. As the conductive material, a conductive material whose visible light transmittance is higher than or equal to 40% and lower than or equal to 100%, preferably higher than or equal to 60% and lower than or equal to 100%, and whose resistivity is lower than or equal to 1 × 10 -2 Ω·cm.

[0188] The electrodes 101, 102, 2101, 2102, 2103, and 2104 can each be formed using a conductive material having a function of transmitting light and reflecting light. As the conductive material, a conductive material whose visible light reflectance is higher than or equal to 20% and lower than or equal to 80%, preferably higher than or equal to 40% and lower than or equal to 70%, and whose resistivity is lower than or equal to 1 × 10 2 Ω cm. For example, one or more types of conductive metals and alloys, conductive compounds, and the like can be used. Specifically, a metal oxide such as indium tin oxide (hereinafter referred to as ITO), indium tin oxide containing silicon or silicon oxide (ITSO), indium oxide-zinc oxide (indium zinc oxide), indium oxide-tin oxide containing titanium, indium titanium oxide, or tungsten oxide and indium oxide containing zinc oxide can be used. A thin metal film having a thickness that allows light transmission (preferably a thickness greater than or equal to 1 nm and less than or equal to 30 nm) can also be used. As the metal, Ag, an alloy of Ag and Al, an alloy of Ag and Mg, an alloy of Ag and Au, an alloy of Ag and Yb, or the like can be used.

[0189] The conductive layer 2101b, the conductive layer 2103b, and the conductive layer 2104b are each preferably formed using the above-described conductive material having a light-transmitting function. The conductive layer 2101a, the conductive layer 2103a, and the conductive layer 2104a are each preferably formed using the conductive material having a light-reflecting function, the conductive material having a light-transmitting function, or the conductive material having a light-transmitting and reflecting function.

[0190] In this specification and the like, as a material having a light-transmitting function, a material that transmits visible light and has conductivity is used. Examples of the material include, in addition to the above-described oxide conductor, of which ITO is a typical example, an oxide semiconductor and an organic conductor containing an organic substance. Examples of the organic conductor containing an organic substance include a composite material in which an organic compound and an electron donor (donor) are mixed, and a composite material in which an organic compound and an electron acceptor (acceptor) are mixed. Alternatively, an inorganic carbon-based material such as graphene may be used. The specific resistance of the material is preferably less than or equal to 1 × 10 5 Ω·cm, more preferably less than or equal to 1 × 10 4 Ω cm.

[0191] Alternatively, the electrode 101 and / or the electrode 102 and the electrode 2102 and / or the group of electrodes 2101, 2103 and 2104 may be formed by stacking a plurality of the materials described above.

[0192] To improve light extraction efficiency, a material whose refractive index is higher than that of an electrode with a function of transmitting light may be formed in contact with the electrode. The material may be electrically conductive or non-conductive as long as it has a function of transmitting visible light. In addition to the oxide conductors described above, an oxide semiconductor and an organic substance can be given as examples of the material. Examples of the organic substance include the materials for the light-emitting layer, the hole-injection layer, the hole-transport layer, the electron-transport layer, and the electron-injection layer. Alternatively, an inorganic carbon-based material or a metal film thin enough to transmit light may be used.As a further alternative, superimposed layers with a thickness of several nanometers to several tens of nanometers can be used.

[0193] In the case where electrode 101 or electrode 102 serves as the cathode, the electrode preferably contains a material with a low work function (3.8 eV or lower). In the case where electrode 2102 or electrodes 2101, 2103, and 2104 serve as the cathode, the electrode(s) preferably contain a material with a low work function (3.8 eV or lower).

[0194] In the case where electrode 101 or electrode 102 is used as the anode, the anode preferably contains a material with a high work function (4.0 eV or higher). In the case where electrode 2102 or electrodes 2101, 2103, and 2104 serve as the anode, the anode preferably contains a material with a high work function (4.0 eV or higher).

[0195] Electrode 101 and electrode 102 may be a laminated structure composed of a conductive material having a light-reflecting function and a conductive material having a light-transmitting function. Such a structure is preferable because electrode 101 and electrode 102 may each have a function of adjusting the optical path length so that light of a desired wavelength emitted from each light-emitting layer is oscillated and amplified. Electrode 2102 and / or electrodes 2101, 2103, and 2104 may similarly each be a laminated structure composed of a conductive material having a light-reflecting function and a conductive material having a light-transmitting function.Such a structure is preferable because the electrodes 2101, 2102, 2103, and 2104 can each have a function of adjusting the optical path length so that light of a desired wavelength emitted from each light-emitting layer is oscillated and amplified.

[0196] As a method for forming the electrodes 101, 102, 2101, 2102, 2103, and 2104, a sputtering method, an evaporation method, a printing method, a coating method, a molecular beam epitaxy (MBE) method, a CVD method, a pulsed laser deposition method, an atomic layer deposition (ALD) method, or the like can be used as needed. <<Mikrokavitätsstruktur> >

[0197] The light-emitting element of one embodiment of the present invention may employ a micro-optical resonator (microcavity) structure in which the electrode 2101 is formed using a conductive material having a function of reflecting light and the electrode 2102 is formed using a conductive material having a function of transmitting and reflecting light, as shown in Fig. 49A and Fig. 49B. With such a structure, the light emitted from the light-emitting layer 2140 or the light-emitting layer 2170 can oscillate between the electrodes, and desired light among light emitted by the electrode 2102 can be amplified.

[0198] Note that in this embodiment, light is extracted to the electrode 2102 side (cathode side), but light may be extracted to the electrode 2101 side (anode side). In this case, the electrode 2101 is formed using a conductive material with a function of reflecting and transmitting light, and the electrode 2102 is formed using a conductive material with a function of reflecting light.

[0199] Light emitted from the light-emitting layer 2140 and the light-emitting layer 2170 oscillates between a pair of electrodes (e.g., the electrode 2101 and the electrode 2102). The light-emitting layer 2140 and the light-emitting layer 2170 are formed at locations that amplify the intensity of light of a desired wavelength among light to be emitted. For example, by adjusting an optical path length from a reflective region of the electrode 2101 to a light-emitting region of the light-emitting layer 2170 and an optical path length from a reflective region of the electrode 2102 to the light-emitting region of the light-emitting layer 2170, the light of a desired wavelength among light emitted from the light-emitting layer 2170 can be amplified.For example, by adjusting an optical path length from the reflective region of the electrode 2101 to a light-emitting region of the light-emitting layer 2140 and an optical path length from the reflective region of the electrode 2102 to the light-emitting region of the light-emitting layer 2140, light of a desired wavelength can be amplified among light emitted from the light-emitting layer 2140. When a light-emitting element has a layer arrangement of a plurality of light-emitting layers (here, the light-emitting layers 2140 and 2170), the optical path lengths of the light-emitting layers 2140 and 2170 are preferably optimized.

[0200] For example, in order to amplify light of a desired wavelength (wavelength: λ) obtained from the light-emitting layer 2140, it is preferable to adjust the optical path length from the reflecting region of the electrode 2101 to a region where the light of the desired wavelength is obtained in the light-emitting layer 2140 (a light-emitting region) and the optical path length from the reflecting region of the electrode 2102 to the region where the light of the desired wavelength is obtained in the light-emitting layer 2140 (the light-emitting region) to approximately (2m'-1)λ / 4 (m' is a natural number). Here, the light-emitting region refers to a region where holes and electrons recombine in the light-emitting layer 2140.

[0201] By such optical adjustment, the spectrum of light obtained from the light-emitting layer 2140 can be narrowed and light emission with high color purity can be obtained. < <substrat>>

[0202] The light-emitting element of one embodiment of the present invention can be formed over a substrate made of glass, plastic, or the like. As a way of stacking layers over the substrate, layers can be arranged sequentially from the electrode 101 side or sequentially from the electrode 102 side. As a way of stacking layers of the light-emitting element 2250a and the light-emitting element 2250b, the layers can be arranged sequentially from the electrode 2101 side, the electrode 2102 side, and the electrode 2103 side, or sequentially from the electrode 2102 side.

[0203] For the substrate over which the light-emitting element of one embodiment of the present invention can be formed, for example, glass, quartz, plastic, or the like can be used. Alternatively, a flexible substrate can be used. The flexible substrate is, for example, a substrate that can be bent, such as a plastic substrate made of polycarbonate or polyarylate. Alternatively, a film, an inorganic film formed by vapor deposition, or the like can be used. Another material can be used as long as the substrate serves as a support in a manufacturing process of the light-emitting elements or the optical elements. Another material having a function of protecting the light-emitting elements or the optical elements can be used.

[0204] For example, in this specification and the like, a light-emitting element can be formed using various substrates. The type of substrate is not particularly limited. Examples of the substrate include a semiconductor substrate (e.g., a single-crystal substrate or a silicon substrate), an SOI substrate, a glass substrate, a quartz substrate, a plastic substrate, a metal substrate, a stainless steel substrate, a substrate containing a stainless steel foil, a tungsten substrate, a substrate containing a tungsten foil, a flexible substrate, an attachment film, cellulose nanofiber (CNF) and paper containing a fiber material, a base material film, and the like. As an example of a glass substrate, a barium borosilicate glass substrate, an aluminum borosilicate glass substrate, a soda-lime glass substrate, and the like can be given.Examples of the flexible substrate, the fixing film, the base material film, and the like include substrates made of plastics, typical examples being polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polytetrafluoroethylene (PTFE). Another example includes a resin such as acrylic. Alternatively, polypropylene, polyester, polyvinyl fluoride, polyvinyl chloride, or the like may be used. Alternatively, polyamide, polyimide, aramid, epoxy, an inorganic film formed by vapor deposition, paper, or the like may be used.

[0205] A flexible substrate may be used as the substrate, and the light-emitting element may be provided directly above the flexible substrate. A separation layer may be provided between the substrate and the light-emitting element. The separation layer may be used when part or all of the light-emitting element formed above the separation layer is completed, separated from the substrate, and transferred to another substrate. In such a case, the light-emitting element may also be transferred to a substrate with low heat resistance or to a flexible substrate. For the above separation layer, for example, a layer assembly comprising inorganic films, namely a tungsten film and a silicon oxide film, or a resin film of polyimide or the like formed over a substrate may be used.

[0206] In other words, after the light-emitting element is formed using one substrate, the light-emitting element can be transferred to another substrate. Examples of a substrate to which the light-emitting element is transferred include, in addition to the substrates described above, a cellophane substrate, a stone substrate, a wood substrate, a fabric substrate (including a natural fiber (e.g., silk, cotton, or hemp), a synthetic fiber (e.g., nylon, polyurethane, or polyester), a regenerated fiber (e.g., acetate, cupro, viscose, or regenerated polyester) or the like), a leather substrate, and a rubber substrate. When such a substrate is used, a light-emitting element with high durability, a light-emitting element with high heat resistance, a lightweight light-emitting element, or a thin light-emitting element can be obtained.

[0207] Light-emitting element 150, light-emitting element 2250a, and light-emitting element 2250b may each be formed, for example, over an electrode electrically connected to a field-effect transistor (FET) formed over one of the substrates described above. In this way, an active matrix display device can be fabricated in which the FET controls the operation of the light-emitting element.

[0208] As the substrate 2220 over which the optical element is formed, the substrate described above can be used. <<lichtundurchlässige Schicht> >

[0209] The light-impermeable layer 2223 has a function of reducing the reflection of external light. The light-impermeable layer 2223 has a function of preventing mixing of light emitted from an adjacent light-emitting element. As the light-impermeable layer 2223, a metal, a resin containing a black pigment, carbon black, a metal oxide, a composite oxide containing a solid solution of a plurality of metal oxides, or the like can be used. <<optisches Element> >

[0210] The optical elements 2224B, 2224G, and 2224R each have a function of selectively transmitting light of a specific color of the incident light. For example, the light emitted from region 2222B via optical element 2224B is blue light, the light emitted from region 2222G via optical element 2224G is green light, and the light emitted from region 2222R via optical element 2224R is red light.

[0211] For example, a color layer (also called a color filter), a bandpass filter, a multilayer filter, or the like can be used for the optical elements 2224R, 2224G, and 2224B. Alternatively, color conversion elements can be used as the optical elements. A color conversion element is an optical element that converts incident light into light with a longer wavelength than the incident light. Quantum dot elements can be advantageously used as the color conversion elements. The use of the quantum dot can increase the color reproducibility of the display device.

[0212] One or more optical elements may be further disposed over each of the optical elements 2224R, 2224G, and 2224B. As another optical element, for example, a circularly polarizing plate, an anti-reflection film, or the like may be provided. A circularly polarizing plate provided on the side where light emitted from the light-emitting element of the display device is taken out can prevent a phenomenon in which light incident from the outside of the display device is reflected inside the display device and redirected to the outside. An anti-reflection film can attenuate external light reflected from a surface of the display device. This leads to clear observation of light emitted from the display device. < <trennwand>>

[0213] The partition wall 2145 has an insulating property and is formed using an inorganic or organic material. Examples of the inorganic material include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, and aluminum nitride. Examples of the organic material include photosensitive resin materials such as an acrylic resin and a polyimide resin.

[0214] It should be noted that a silicon oxynitride film refers to a film in which the oxygen content is higher than the nitrogen content. The silicon oxynitride film preferably contains oxygen, nitrogen, silicon, and hydrogen in the respective ranges of 55 atomic % to 65 atomic %, 1 atomic % to 20 atomic %, 25 atomic % to 35 atomic % and 0.1 atomic % to 10 atomic %. A silicon nitride oxide film refers to a film in which the nitrogen content is higher than the oxygen content. The silicon nitride oxide film preferably contains nitrogen, oxygen, silicon, and hydrogen in the respective ranges of 55 atomic % to 65 atomic %, 1 atomic % to 20 atomic %, 25 atomic % to 35 atomic % and 0.1 atomic % to 10 atomic %.

[0215] The structure described in this embodiment may be appropriately combined with any of the other embodiments. (Embodiment 2)

[0216] In this embodiment, a light-emitting element having a structure different from that described in Embodiment 1 and a light-emitting mechanism of the light-emitting element will be described below with reference to Fig. 3A and Fig. 3B. In Fig. 3A and Fig. 3B will in some cases be a section with a similar function to that in Fig. 1A by the same hatching pattern as in Fig. 1A and are not specifically identified by a reference symbol. In addition, the same reference symbols are used for sections with similar functions, and a detailed description of the sections is omitted in some cases. <Strukturbeispiel 5 des Licht emittierenden Elements>

[0217] Fig. 3A and Fig. 3B are schematic cross-sectional views of a light-emitting element 250 and a light-emitting element 252.

[0218] The light-emitting elements 250 and 252, which are Fig. 3A and Fig. 3B each comprise a plurality of light-emitting units (a light-emitting unit 106 and a light-emitting unit 108 in Fig. 3A and Fig. 3B) between the pair of electrodes (the electrode 101 and the electrode 102). Note that the electrode 101 serves as the anode and the electrode 102 serves as the cathode in the following description of the light-emitting elements 250 and 252; however, the functions of the light-emitting element 250 may be interchanged.

[0219] In the light-emitting elements 250 and 252, which are Fig. 3A and Fig. 3B, the light-emitting unit 106 and the light-emitting unit 108 are stacked, and a charge generation layer 115 is provided between the light-emitting unit 106 and the light-emitting unit 108. Note that the light-emitting unit 106 and the light-emitting unit 108 may have the same structure or may have different structures.

[0220] The light-emitting elements 250 and 252 each comprise a light-emitting layer 140 and the light-emitting layer 170. The light-emitting unit 106 comprises, in addition to the light-emitting layer 170, the hole-injection layer 111, the hole-transport layer 112, an electron-transport layer 113, and an electron-injection layer 114. The light-emitting unit 108 comprises, in addition to the light-emitting layer 140, a hole-injection layer 116, a hole-transport layer 119, the electron-transport layer 118, and the electron-injection layer 130.

[0221] The composite material of the transition metal and the organic compound having an unshared electron pair described in Embodiment 1 can be suitably used for the electron injection layer 114 and the electron injection layer 130. With such a structure, a highly reliable light-emitting element with high moisture resistance and operable at a low voltage can be provided. Furthermore, the charge generation layer 160 can be provided between the electron injection layer 130 and the electrode 102 as in the embodiment shown in Fig. 3B. This structure can further improve the moisture resistance and oxidation resistance of the element.

[0222] As described above, each of the charge generation layers 115 and 160 may have either a structure in which an acceptor substance, i.e., an electron acceptor, is added to a hole-transporting material, or a structure in which a donor substance, i.e., an electron donor, is added to an electron-transporting material. Alternatively, both of these structures may be stacked. With this structure, a light-emitting element with high moisture resistance can be easily manufactured.

[0223] In the light-emitting elements of one embodiment of the present invention, the charge generation layers 115 and 160 can be formed using the same material. For example, the charge generation layers 115 and 160 can be formed using the same hole-transport material and the same acceptor material. With this structure, a light-emitting element with high moisture resistance can be easily manufactured.

[0224] The charge generation layer 115 provided between the light-emitting unit 106 and the light-emitting unit 108 may have any structure as long as electrons can be injected into the light-emitting unit on one side and holes can be injected into the light-emitting unit on the other side when a voltage is applied between the electrode 101 and the electrode 102. For example, Fig. 3A and Fig. 3B, the charge generation layer 115 transfers electrons into the light-emitting unit 106 and holes into the light-emitting unit 108 when a voltage is applied such that the potential of the electrode 101 is higher than that of the electrode 102.

[0225] The light-emitting element, which has two light-emitting units, is Fig. 3A and Fig. 3B; however, a similar structure can also be applied to a light-emitting element in which three or more light-emitting units are stacked. By placing a plurality of light-emitting units separated by the charge generation layer between a pair of electrodes, just as in the light-emitting element 250, a light-emitting element capable of emitting light with high luminance while keeping the current density low and having a long lifetime can be provided. A light-emitting element with low power consumption can also be provided.

[0226] Note that, in each of the structures described above, the emission colors of the guest materials used in the light-emitting unit 106 and the light-emitting unit 108 may be the same or different. In the case where guest materials emitting light of the same color are used for the light-emitting unit 106 and the light-emitting unit 108, the light-emitting elements 250 and 252 can exhibit high emission luminance at a small current value, which is preferable. In the case where guest materials emitting light of different colors are used for the light-emitting unit 106 and the light-emitting unit 108, the light-emitting element 250 can exhibit multi-color light emission, which is preferable.In this case, when a plurality of light-emitting materials with different emission wavelengths are used in one or both of the light-emitting layers 140 and 170, the light-emitting element 250 emits light obtained by synthesizing lights with different emission peaks. That is, the emission spectrum of the light-emitting element 250 has at least two peaks.

[0227] The above structure is also suitable for obtaining white light emission. When the light-emitting layer 140 and the light-emitting layer 170 emit light of complementary colors, white light emission can be obtained. Preferably, the guest materials are particularly selected such that white light emission with high color rendering properties or light emission of at least red, green, and blue can be obtained.

[0228] It should be noted that when using a light-emitting element in which three or more light-emitting units are stacked, the emission colors of the guest materials used in the light-emitting units may be the same or different. In the case where a light-emitting element includes light-emitting units having the same emission color, the emission color of the light-emitting units can have a higher light emission luminance than another emission color of a light-emitting unit at a lower current value. Such a structure can be suitably used to adjust light emission colors. The structure is particularly suitable when guest materials with different emission efficiencies and different emission colors are used.For example, if the light-emitting element includes three layers of light-emitting units, the light-emitting units are two light-emitting units containing a fluorescent compound and emitting light of the same color, and one light-emitting unit containing a phosphorescent compound and emitting light of a different color than the fluorescent compound. In this case, the intensity of fluorescence and phosphorescence can be adjusted. That is, the emission intensity of light of each color can be adjusted by the number of light-emitting units.

[0229] When the light-emitting element includes two layers of fluorescence-emitting units and one layer of phosphorescence-emitting units, the preferred combinations of the emitting units are as follows: a combination of the two layers of fluorescence-emitting units containing a blue fluorescent compound and the one layer of phosphorescence-emitting units containing a yellow phosphorescence-emitting compound; a combination of the two layers of fluorescence-emitting units containing a blue fluorescent compound and the one layer of phosphorescence-emitting units containing a red phosphorescent compound and a green phosphorescent compound;and a combination of the two layers of fluorescence-emitting units containing a blue fluorescent compound and the one layer of phosphorescent units containing a red phosphorescent compound, a yellow phosphorescent compound, and a green phosphorescent compound. These combinations are preferable because they enable efficient white light emission.

[0230] At least one of the light-emitting layers 140 and 170 may be further divided into layers, and the divided layers may include different light-emitting materials. That is, at least one of the light-emitting layers 140 and 170 may be composed of two or more layers. For example, in the case where the light-emitting layer is formed by stacking a first light-emitting layer and a second light-emitting layer in this order from the hole-transport layer side, the first light-emitting layer is formed using a material having a hole-transport property as a host material, and the second light-emitting layer is formed using a material having an electron-transport property as a host material.In this case, a light-emitting material included in the first light-emitting layer may be the same as or different from a light-emitting material included in the second light-emitting layer. Furthermore, the materials may have functions of emitting light of the same color or light of different colors. White light emission with high color rendering properties formed from three primary colors or four or more colors can be obtained by using a plurality of light-emitting materials that emit light of different colors.

[0231] Note that the light-emitting units 106 and 108 and the charge generation layer 115 can be formed by an evaporation method (including a vacuum evaporation method), an inkjet method, a coating method, gravure printing, or the like.

[0232] It should be noted that the structure described in this embodiment may be combined with any of the structures described in the other embodiments as needed. (Embodiment 3)

[0233] In this embodiment, examples of a light-emitting device using the light-emitting element described in Embodiments 1 and 2 will be described with reference to Fig. 4A and Fig. 4B, Fig. 5A and Fig. 5B and Fig. 6 described.

[0234] Fig. 4A is a plan view of the light-emitting device, and Fig. Figure 4B is a cross-sectional view along lines AB and CD in Fig. 4A. The light-emitting device includes a driver circuit section (source-side driver circuit) 601, a pixel section 602, and a driver circuit section (gate-side driver circuit) 603, which control the light emission of a light-emitting element and are represented by dotted lines. Furthermore, reference numeral 604 denotes a sealing substrate, reference numeral 625 a desiccant, and reference numeral 605 a sealing material. A portion surrounded by the sealing material 605 is a space 607.

[0235] Note that a lead line 608 is a line for transmitting signals to be input to the source-side drive circuit 601 and the gate-side drive circuit 603, and for receiving a video signal, a clock signal, a start signal, a reset signal, and the like from a flexible printed circuit (FPC) 609 serving as an external input terminal. Although only the FPC is illustrated here, a printed wiring board (PWB) may be attached to the FPC. The light-emitting device in this specification includes within its category not only the light-emitting device itself but also the light-emitting device provided with the FPC or the PWB.

[0236] Next, a cross-sectional structure of the light-emitting device is shown using Fig. 4B. The driver circuit portion and the pixel portion are formed over an element substrate 610. Here, the source-side driver circuit 601, which is the driver circuit portion, and one pixel of the pixel portion 602 are illustrated.

[0237] In the source-side driver circuit 601, a CMOS circuit is formed in which an n-channel TFT 623 and a p-channel TFT 624 are combined. The driver circuit can be formed using various circuits, such as a CMOS circuit, a PMOS circuit, or an NMOS circuit. Furthermore, in this embodiment, a driver-integrated type is described in which the driver circuit is formed above the substrate; however, the driver circuit does not necessarily have to be formed above the substrate and may be formed outside the substrate.

[0238] The pixel section 602 includes a plurality of pixels including a switching TFT 611, a current control TFT 612, and a first electrode 613 electrically connected to a drain of the current control TFT 612. Note that an insulator 614 is formed to cover an end portion of the first electrode 613. The insulator 614 can be formed using a positive photosensitive resin film.

[0239] To improve coverage with a film formed over the insulator 614, the insulator 614 is formed to have a curved surface with a curvature at its upper or lower end portion. For example, in the case where a photosensitive acrylic is used for a material of the insulator 614, it is preferable that only the upper end portion of the insulator 614 has a curved surface. The radius of curvature of the curved surface is preferably greater than or equal to 0.2 µm and less than or equal to 0.3 µm. Either a negative photosensitive material or a positive photosensitive material can be used as the insulator 614.

[0240] An EL layer 616 and a second electrode 617 are formed over the first electrode 613. As the material for the first electrode 613, which serves as an anode, a material with a high work function is preferably used. For example, a single-layer film of an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing 2 wt% to 20 wt% zinc oxide, a titanium nitride film, a chromium film, a tungsten film, a Zn film, a Pt film, or the like, a stacked film of a titanium nitride film and a film containing aluminum as its main component, a stacked film of three layers of a titanium nitride film, a film containing aluminum as its main component, and a titanium nitride film, or the like can be used. The multilayer structure enables low conduction resistance, good ohmic contact, and function as an anode.

[0241] The EL layer 616 is formed by one of various methods, such as an evaporation method using an evaporation mask, an inkjet method, and a spin coating method. As another material included in the EL layer 616, a low-molecular compound or a high-molecular compound (including an oligomer or a dendrimer) can be used.

[0242] As the material for the second electrode 617 formed over the EL layer 616 and serving as a cathode, a material with a low work function (e.g., Al) is preferably used. When light generated in the EL layer 616 is transmitted through the second electrode 617, a stacked arrangement of a thin metal film and a transparent conductive film (e.g., ITO, indium oxide containing 2 wt% or more and 20 wt% or less of zinc oxide, indium tin oxide containing silicon, or zinc oxide (ZnO)) is preferably used for the second electrode 617.

[0243] Note that the light-emitting element 618 is formed by the first electrode 613, the EL layer 616, and the second electrode 617. The light-emitting element 618 preferably has the structure described in Embodiment 1 and Embodiment 2. In the light-emitting device of this embodiment, the pixel portion including a plurality of light-emitting elements may include both the light-emitting element having the structure described in Embodiment 1 or Embodiment 2 and a light-emitting element having a different structure.

[0244] The sealing substrate 604 is attached to the element substrate 610 with the sealant 605, so that the light-emitting element 618 is provided in the space 607 enclosed by the element substrate 610, the sealing substrate 604, and the sealant 605. The space 607 is filled with a filler. The filler may be an inert gas (such as nitrogen or argon), a resin, and / or a desiccant.

[0245] An epoxy-based resin or a glass frit is preferably used for the sealant 605. Furthermore, these materials are preferably materials that allow as little moisture or oxygen permeation as possible. A glass substrate, a quartz substrate, or a plastic substrate made of fiber-reinforced plastic (FRP), poly(vinyl fluoride) (PVF), polyester, acrylic, or the like can be used as the sealant substrate 604.

[0246] As described above, the light-emitting device including the light-emitting element described in Embodiments 1 and 2 can be obtained. <Strukturbeispiel 1 für Licht emittierende Vorrichtung>

[0247] Fig. 5A and Fig. 5B each shows, as an example of a light-emitting device, a light-emitting device including a light-emitting element that emits white light and a color layer (a color filter).

[0248] Fig. 5A illustrates a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, and 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral portion 1042, a pixel portion 1040, a driving circuit portion 1041, first electrodes 1024W, 1024R, 1024G, and 1024B of light-emitting elements, a partition wall 1026, an EL layer 1028, a second electrode 1029 of the light-emitting elements, a sealing substrate 1031, a sealant 1032, and the like.

[0249] In Fig. 5A and Fig. 5B, color layers (a red color layer 1034R, a green color layer 1034G, and a blue color layer 1034B) are further provided on a transparent base material 1033. Additionally, a black layer (black matrix) 1035 may be provided. The transparent base material 1033, provided with the color layers and the black layer, is positioned and fixed to the substrate 1001. Note that the color layers and the black layer are covered with a cover layer 1036. In Fig. 5A, light emitted from some of the light-emitting layers does not pass through the color layers, while light emitted from the other light-emitting layers passes through the color layers. Since the light that does not pass through the color layers is white, and the light that passes through one of the color layers is red, blue, or green, an image can be displayed using pixels of the four colors.

[0250] Fig. 5B illustrates an example in which the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B are formed between the gate insulating film 1003 and the first interlayer insulating film 1020. As shown in Fig. 5B, the color layers may be provided between the substrate 1001 and the sealing substrate 1031.

[0251] The light-emitting device described above has a structure in which light is taken out from the side of the substrate 1001 where the TFTs are formed (bottom-emission structure), but it may also have a structure in which light is taken out from the side of the sealing substrate 1031 (top-emission structure). <Strukturbeispiel 2 der Licht emittierenden Vorrichtung>

[0252] Fig. 6 is a cross-sectional view of a light-emitting device with a top-emission structure. In this case, a substrate that does not transmit light can be used as the substrate 1001. The process up to the step of forming a connection electrode that connects the TFT and the anode of the light-emitting element is performed in a manner similar to that of the light-emitting device with a bottom-emission structure. A third interlayer insulating film 1037 is then formed to cover an electrode 1022. This insulating film may have a planarization function. The third interlayer insulating film 1037 may be formed using a material similar to that of the second interlayer insulating film 1021 or using other various materials.

[0253] The first lower electrodes 1025W, 1025R, 1025G, and 1025B of the light-emitting elements serve as anodes here, but they can also serve as cathodes. Furthermore, in the case of the light-emitting device with a top-emission structure, as shown in Fig. 6, the lower electrodes 1025W, 1025R, 1025G, and 1025B are preferably reflective electrodes. Note that the second electrode 1029 preferably has a function of reflecting light and a function of transmitting light. It is preferable that a microcavity structure is used between the second electrode 1029 and the lower electrodes 1025W, 1025R, 1025G, and 1025B, in which case, light having a specific wavelength is amplified. The EL layer 1028 is formed with a structure similar to that described in Embodiment 2, whereby white light emission can be obtained.

[0254] In Fig. 5A and Fig. 5B and Fig. 6, the structure of the EL layer for providing white light emission can be achieved by, for example, using a plurality of light-emitting layers or a plurality of light-emitting units. Note that the structure for providing white light emission is not limited to the above.

[0255] With a top issue structure like in Fig. 6, sealing can be performed with the sealing substrate 1031 on which the color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) are provided. The sealing substrate 1031 can be provided with the black layer (black matrix) 1030 positioned between pixels. The color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) and the black layer (black matrix) can be covered with the cover layer. Note that a light-transmitting substrate is used as the sealing substrate 1031.

[0256] Although an example is shown here in which full-color display is performed using four colors, namely red, green, blue, and white, there is no particular limitation, and full-color display may be performed using three colors, namely red, green, and blue, or four colors, namely red, green, blue, and yellow.

[0257] As described above, the light-emitting device including the light-emitting element described in Embodiments 1 and 2 can be obtained.

[0258] It should be noted that this embodiment may be appropriately combined with any of the other embodiments. (Embodiment 4)

[0259] In this embodiment, a transistor that can be used in a display device of an embodiment of the present invention will be described with reference to Fig. 7A to 7G.

[0260] One in Fig. The transistor shown in Figure 7A is a so-called channel-etched bottom-gate transistor. The transistor includes, over a substrate 411, a conductive layer 431 serving as a gate electrode, an insulating layer 434 serving as a gate insulating layer, a semiconductor layer 432, and a pair of conductive layers 433a and 433b serving as a source and drain electrode. A region of the semiconductor layer 432 that overlaps with the conductive layer 431 serves as a channel formation region. The semiconductor layer 432 is connected to the conductive layer 433a and the conductive layer 433b.

[0261] The transistor, which is Fig. 7A includes a pair of impurity semiconductor layers 435 serving as a source region and a drain region. The impurity semiconductor layers 435 are provided between the semiconductor layer 432 and the conductive layer 433a, and between the semiconductor layer 432 and the conductive layer 433b. The semiconductor layer 432 and the impurity semiconductor layers 435 are provided in contact with each other. The impurity semiconductor layer 435 is provided in contact with one of the conductive layer 433a and the conductive layer 433b.

[0262] For example, a semiconductor containing silicon can be used as the semiconductor layer 432. As the semiconductor containing silicon, hydrogenated amorphous silicon, microcrystalline silicon, or polycrystalline silicon can be used, for example. In particular, hydrogenated amorphous silicon is preferably used because it can be formed over a large substrate with high yield. The display device of one embodiment of the present invention can also advantageously display an image with a transistor containing amorphous silicon, which has a relatively low field-effect mobility.

[0263] An organic substance can be used for the semiconductor layer 432. For example, the electron-transport material or hole-transport material described above can be used as the organic substance. Furthermore, a high-molecular compound such as polythiophene, polyparaphenylenevinylene, or polydiacetylene can be used. Note that the organic substance is not limited to these.

[0264] The impurity semiconductor film constituting the impurity semiconductor layer 435 is formed using a semiconductor to which an impurity element that imparts a conductivity type has been added. In the case where the transistor is an n-channel transistor, silicon to which P or As has been added can be specified as the semiconductor to which an impurity element that imparts a conductivity type has been added. For example, when the transistor is a p-channel transistor, it is possible to add B as the impurity element that imparts a conductivity type; however, an n-channel transistor is preferably used. Note that the impurity semiconductor layer can be formed using an amorphous semiconductor or using a crystalline semiconductor such as a microcrystalline semiconductor.Note that the composite material of the transition metal and the organic compound having an unshared electron pair described in Embodiment 1 can be suitably used for the impurity semiconductor layer 435.

[0265] A transistor that is Fig. 7B, comprises a semiconductor layer 437 between the semiconductor layer 432 and the impurity semiconductor layer 435.

[0266] The semiconductor layer 437 may be formed using the same semiconductor film as the semiconductor layer 432. The semiconductor layer 437 may serve as an etching stopper to prevent the semiconductor layer 432 from being removed during etching of the impurity semiconductor layer 435. Although Fig. 7A illustrates an example in which the semiconductor layer 37 is divided into right and left portions, a part of the semiconductor layer 437 may cover a channel formation region of the semiconductor layer 432.

[0267] Furthermore, the concentration of an impurity in the semiconductor layer 437 may be lower than that in the impurity semiconductor layer 435. Thus, the semiconductor layer 437 may serve as a lightly doped drain (LDD) region and suppress hot carrier degradation when the transistor is driven.

[0268] In a Fig. In the transistor shown in Figure 7C, an insulating layer 484 is provided over a channel formation region of the semiconductor layer 432. The insulating layer 484 serves as an etching stopper at the time of etching the impurity semiconductor layer 435.

[0269] One in Fig. The transistor shown in Figure 7D includes a semiconductor layer 432p instead of the semiconductor layer 432. The semiconductor layer 432p includes a semiconductor film with high crystallinity. For example, the semiconductor layer 432p includes a polycrystalline semiconductor or a single-crystal semiconductor. Thus, a transistor with high field-effect mobility can be provided.

[0270] One in Fig. 7E includes the semiconductor layer 432p in a channel formation region of the semiconductor layer 432. For example, the transistor shown in Fig. 7E can be formed by irradiating a semiconductor film, which will become the semiconductor layer 432, with laser light or the like, so that the semiconductor film is locally crystallized. Thus, a transistor with high field-effect mobility can be provided.

[0271] One in Fig. 7F includes the semiconductor layer 432p having crystallinity in a channel formation region of the semiconductor layer 432 of the transistor shown in Fig. 7B shown transistor.

[0272] One in Fig. 7G includes the semiconductor layer 432p having crystallinity in a channel formation region of the semiconductor layer 432 of the transistor shown in Fig. 7C shown transistor.

[0273] Components of the transistor are described in detail below.

[0274] The transistors each include a conductive layer that serves as the gate electrode, the semiconductor layer, a conductive layer that serves as the source electrode, a conductive layer that serves as the drain electrode, and an insulating layer that serves as the gate insulating layer.

[0275] Note that there is no particular limitation on the structure of the transistor included in the display device of one embodiment of the present invention. For example, a planar transistor, a staggered transistor, or an inverted staggered transistor may be used. A top-gate transistor or a bottom-gate transistor may be used. Gate electrodes may be provided above and below a channel.

[0276] There is no particular limitation on the crystallinity of a semiconductor material used for transistors, and an amorphous semiconductor or a semiconductor having crystallinity (a microcrystalline semiconductor, a polycrystalline semiconductor, a single-crystal semiconductor, or a semiconductor partially containing crystal regions) can be used. Preferably, a semiconductor having crystallinity is used, in which case, deterioration of transistor characteristics can be suppressed.

[0277] For example, silicon can be used as the semiconductor in which a channel of the transistor is formed. Amorphous silicon is particularly preferred as the silicon. Using amorphous silicon, a transistor can be formed over a large substrate with high yield, resulting in high mass productivity.

[0278] In addition, silicon with crystallinity, such as microcrystalline silicon, polycrystalline silicon, or single-crystal silicon, can be used. In particular, polycrystalline silicon can be formed at a lower temperature than single-crystal silicon, and it exhibits higher field-effect mobility and higher reliability than amorphous silicon.

[0279] The bottom-gate transistor described in this embodiment is preferable because the number of manufacturing steps can be reduced. When amorphous silicon, which can be formed at a lower temperature than polycrystalline silicon, is used for the semiconductor layer, materials with low heat resistance can also be used for a wiring, an electrode, or a substrate under the semiconductor layer, resulting in a wider range of materials. For example, a very large glass substrate can be advantageously used. On the other hand, the top-gate transistor is preferable because an impurity region is easily self-aligned and fluctuations in characteristics can be reduced. In some cases, the top-gate transistor is particularly preferable when using polycrystalline silicon, single-crystal silicon, or the like. < <substrat>>

[0280] There is no particular limitation on the property of a material and the like of the substrate 411, as long as the material has heat resistance sufficient to withstand at least subsequent heat treatment. For example, a glass substrate, a ceramic substrate, a quartz substrate, a sapphire substrate, or the like can be used as the substrate 411. Alternatively, a single-crystal semiconductor substrate or a polycrystalline semiconductor substrate made of silicon or silicon carbide, a compound semiconductor substrate made of silicon germanium or the like, an SOI (silicon on insulator) substrate, or the like can be used as the substrate 411, or any of these substrates provided with a semiconductor element can be used as the substrate 411.In the case where a glass substrate is used as the substrate 411, a large glass substrate having any of the following sizes can be used: the sixth generation (1500 mm × 1850 mm), the seventh generation (1870 mm × 2200 mm), the eighth generation (2200 mm × 2400 mm), the ninth generation (2400 mm × 2800 mm), and the tenth generation (2950 mm × 3400 mm). Consequently, a large display device can be manufactured. Such a large substrate is preferably used because it can reduce the manufacturing cost.

[0281] Alternatively, a flexible substrate may be used as substrate 411, and the transistor may be provided directly on the flexible substrate. A separation layer may be provided between substrate 411 and the transistor. The separation layer may be used when part or all of the transistor formed above the separation layer is completed, separated from substrate 411, and transferred to another substrate. In such a case, the transistor may also be transferred to a substrate with low heat resistance or to a flexible substrate. <<Leitende Schicht> >

[0282] As materials for a gate, source, and drain of a transistor, any metals such as aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, and tungsten, or an alloy containing any of these metals as its main components, can be used. A single-layer structure or a multilayer structure made of a film containing any of these materials can be used. For example, the following structures can be given: a single-layer structure of an aluminum film containing silicon; a two-layer structure in which an aluminum film is arranged over a titanium film; a two-layer structure in which an aluminum film is arranged over a tungsten film; a two-layer structure in which a copper film is arranged over a copper-magnesium-aluminum alloy film; a two-layer structure,in which a copper film is arranged over a titanium film, a two-layer structure in which a copper film is arranged over a tungsten film, a three-layer structure in which a titanium film or a titanium nitride film, an aluminum film or a copper film, and a titanium film or a titanium nitride film are arranged one above the other in this order, and a three-layer structure in which a molybdenum film or a molybdenum nitride film, an aluminum film or a copper film, and a molybdenum film or a molybdenum nitride film are arranged one above the other in this order. It should be noted that an oxide such as indium oxide, tin oxide, or zinc oxide may be used. Copper containing manganese is preferably used because shape controllability is increased during etching processing.

[0283] As a light-transmitting conductive material that can be used for the gate, source, and drain of the transistor, a conductive oxide such as indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zinc oxide, or zinc oxide with gallium added, or graphene, can be used. A metal material such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, or titanium, an alloy material containing one of these metal materials, or a nitride of the metal material (e.g., titanium nitride) can also be used. When using the metal material or the alloy material (or the nitride thereof), the film thickness is set to be small enough to transmit light. Alternatively, a multilayer film made of any of the above materials can be used for the conductive layers.For example, a multilayer film made of indium tin oxide and an alloy of silver and magnesium is preferably used because conductivity can be increased. They can also be used for conductive layers, such as various wirings and electrodes included in a display device, and conductive layers (such as conductive layers serving as a pixel electrode or common electrode) included in a display element. < <isolierschicht>>

[0284] Examples of an insulating material that can be used for the insulating layers include a resin such as an acrylic or epoxy resin, a resin having a siloxane bond such as silicone, and an inorganic insulating material such as silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, or aluminum oxide.

[0285] Examples of the low water permeability insulating film include a film containing nitrogen and silicon (e.g., a silicon nitride film and a silicon nitride oxide film) and a film containing nitrogen and aluminum (e.g., an aluminum nitride film). Alternatively, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, or the like may be used.

[0286] It should be noted that the films included in the transistor described in Embodiment 4 (i.e., the conductive film, the insulating film, the semiconductor film, and the like) can be formed by a sputtering method, a chemical vapor deposition (CVD) method, a plasma-enhanced chemical vapor deposition (PECVD) method, a vacuum evaporation method, or a pulsed laser deposition (PLD) method. However, an embodiment of the present invention is not limited to this, and the films can be formed by, for example, a coating method, a printing method, a thermal CVD method, or an atomic layer deposition (ALD) method. The conductive film, the insulating film, the semiconductor film, and the like can be formed by a thermal CVD method such as evaporation.a metal-organic CVD (MOCVD) process. (Embodiment 5)

[0287] In this embodiment, electronic devices of an embodiment of the present invention will be described.

[0288] One embodiment of the present invention is a light-emitting element using organic EL, allowing highly reliable electronic devices with flat surfaces and favorable emission efficiency to be manufactured. According to one embodiment of the present invention, highly reliable electronic devices with curved surfaces and favorable emission efficiency can be manufactured.

[0289] Examples of the electronic devices include a television set, a desktop or notebook personal computer, a monitor of a computer or the like, a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a portable information terminal, an audio playback device, and a large gaming machine such as a pinball machine.

[0290] A portable information terminal 900 which is Fig. 8A and Fig. 8B includes a housing 901, a case 902, a display portion 903, a hinge portion 905, and the like.

[0291] The housing 901 and the housing 902 are connected to each other via the hinge portion 905. The portable information terminal 900 can, as in Fig. 8B, from a closed state ( Fig. 8A). Thus, the portable information terminal 900 has high portability when worn and excellent visibility when used thanks to its large display area.

[0292] In the portable information terminal 900, the flexible display portion 903 is provided across the case 901 and the case 902, which are connected to each other by the hinge portion 905.

[0293] The light-emitting device manufactured using an embodiment of the present invention can be used for the display section 903. Thus, the portable information terminal can be manufactured with high yield.

[0294] The display section 903 can display at least one of a text, a still image, a moving image, and the like. When a text is displayed on the display section, the portable information terminal 900 can be used as an e-book reader.

[0295] When the portable information terminal 900 is opened, the display portion 903 is significantly curved. For example, the display portion 903 is held while including a curved portion with a radius of curvature greater than or equal to 1 mm and less than or equal to 50 mm, preferably greater than or equal to 5 mm and less than or equal to 30 mm. A portion of the display portion 903 can display an image in the curved state because pixels are continuously arranged from the housing 901 to the housing 902.

[0296] The display section 903 serves as a touch screen and can be operated with a finger, a pen, or the like.

[0297] The display portion 903 is preferably formed using a flexible display. Thus, a continuous image can be displayed between the housing 901 and the housing 902. Note that both the housing 901 and the housing 902 may be provided with a display.

[0298] The hinge portion 905 preferably includes a locking mechanism so that an angle formed between the housing 901 and the case 902 does not become larger than a predetermined angle when the portable information terminal 900 is opened. For example, an angle at which the housing 901 and the case 902 are locked (they will not be opened further) is preferably greater than or equal to 90° and smaller than 180°, and may typically be 90°, 120°, 135°, 150°, 175°, or the like. In this case, the convenience, safety, and reliability of the portable information terminal 900 can be improved.

[0299] When the hinge portion 905 includes a locking mechanism, excessive force is not applied to the display portion 903; thus, damage to the display portion 903 can be prevented. Consequently, a highly reliable portable information terminal can be provided.

[0300] For the housing 901 and the housing 902, a power button, an operation button, an external connection port, a speaker, a microphone, or the like may be provided.

[0301] Either the housing 901 or the housing 902 is provided with a wireless communication module, and data can be transmitted and received via a computer network such as the Internet, a local area network (LAN), or Wi-Fi (registered trademark).

[0302] A portable information terminal 910 which is Fig. 8C includes a housing 911, a display section 912, an operation button 913, an external connection terminal 914, a speaker 915, a microphone 916, a camera 917, and the like.

[0303] The light-emitting device manufactured using an embodiment of the present invention can be used for the display section 912. Thus, the portable information terminal can be manufactured with high yield.

[0304] The portable information terminal 910 includes a touch sensor in the display section 912. Operations such as making a call and entering text can be performed by touching the display section 912 with a finger, a stylus, or the like.

[0305] The operation buttons 913 can be used to turn the power on / off. Furthermore, the types of images displayed on the display section 912 can be switched. For example, an image from an email writing screen can be switched to a main menu screen using the operation button 913.

[0306] When a detection device such as a gyroscope sensor or an acceleration sensor is provided within the portable information terminal 910, the direction of the display on the screen of the display section 912 can be automatically changed by determining the orientation of the portable information terminal 910 (whether the portable information terminal 910 is arranged horizontally or vertically). The direction of the display on the screen can also be changed by touching the display section 912, operating the operation button 913, inputting sound from the microphone 916, or the like.

[0307] The portable information terminal 910 serves, for example, as one or more of a telephone, a notebook, and an information search system. Specifically, the portable information terminal 910 can be used as a smartphone. The portable information terminal 910 can execute various applications, such as making mobile phone calls, sending and receiving emails, displaying and editing text, playing music, playing moving images, Internet communication, and playing computer games.

[0308] A camera 920, which is Fig. 8D includes a housing 921, a display section 922, operation buttons 923, a shutter button 924, and the like. Furthermore, an attachable lens 926 is attached to the camera 920.

[0309] The light-emitting device manufactured using an embodiment of the present invention can be used for the display section 922. Thus, a low-power camera can be manufactured.

[0310] Although the lens 926 of the camera 920 is removable from the housing 921 for replacement, the lens 926 may be integrated into the housing 921.

[0311] A still image or a moving image can be captured with the camera 920 when the shutter button 924 is pressed. In addition, images can also be captured by touching the display section 922, which has a function of a touch screen.

[0312] It should be noted that a strobe, a viewfinder, or the like may additionally be attached to the camera 920. Alternatively, these may be integrated into the housing 921.

[0313] Fig. 9A is a perspective view of a wristwatch-type portable information terminal 9200. Fig. 9B is a perspective view of a wristwatch-type portable information terminal 9201.

[0314] The portable information terminal 9200, which is Fig. 9A can perform various applications, such as making mobile phone calls, sending and receiving emails, displaying and editing texts, playing music, Internet communication, and playing computer games. The display surface of the display section 9001 is curved, and an image can be displayed on the curved display surface. The portable information terminal 9200 can use short-range communication according to a communication standard. For example, in this case, mutual communication can be performed between the portable information terminal 9200 and a headset capable of wireless communication, thereby enabling hands-free calling.The portable information terminal 9200 includes the connection port 9006, and data can be directly sent and received to and from another information terminal via a connector. Charging via the connection port 9006 is also possible. Note that charging can be performed without the connection port 9006 by wireless power supply.

[0315] In contrast to the Fig. 9A, the display area of ​​the display section 9001 in the portable information terminal shown in Fig. 9B is not curved. Moreover, the external state of the display section of the portable information terminal 9201 is a non-rectangular shape (a circular shape in Fig. 9B).

[0316] Fig. 9C to Fig. 9E are perspective views of a foldable portable information terminal 9202. Fig. 9C is a perspective view illustrating the portable information terminal 9202 being opened. Fig. 9D is a perspective view illustrating the portable information terminal 9202 being opened or folded. Fig. 9E is a perspective view illustrating the portable information terminal 9202 being folded.

[0317] The folded portable information terminal 9202 is highly portable, and the opened portable information terminal 9202 is highly searchable thanks to a seamless large display area. The display section 9001 of the portable information terminal 9202 is supported by three housings 9000 connected to each other by hinges 9055. The shape of the portable information terminal 9202 can be reversibly changed from the opened state to the folded state by folding the portable information terminal 9202 at a connecting portion between two housings 9000 with the hinges 9055. For example, the portable information terminal 9202 can be bent with a radius of curvature greater than or equal to 1 mm and less than or equal to 150 mm.

[0318] It should be noted that this embodiment may be appropriately combined with any of the other embodiments. (Embodiment 6)

[0319] In this embodiment, examples in which the light-emitting element of one embodiment of the present invention is used for various lighting devices will be explained with reference to Fig. 10A to Fig. 10C and Fig. 11. By using the light-emitting element of one embodiment of the present invention, a highly reliable lighting device with favorable emission efficiency can be manufactured.

[0320] An electronic device or a lighting apparatus having a light-emitting region with a curved surface can be obtained by using the light-emitting element of one embodiment of the present invention, which is fabricated over a substrate having flexibility.

[0321] Furthermore, a light-emitting device using the light-emitting element of one embodiment of the present invention can also be used for lighting for vehicles; examples include lighting for a windshield, a vehicle ceiling, and the like.

[0322] Fig. 10A is a perspective view illustrating a surface of a multifunction device 3500, and Fig. 10B is a perspective view illustrating the other surface of the multifunctional device 3500. A housing 3502 of the multifunctional device 3500 incorporates a display section 3504, a camera 3506, an illuminator 3508, and the like. The light-emitting device of one embodiment of the present invention can be used for the illuminator 3508.

[0323] The illuminator 3508, which includes the light-emitting device of one embodiment of the present invention, serves as a planar light source. Accordingly, the illuminator 3508 can provide low-directivity light emission, unlike a point light source, of which an LED is a typical example. For example, when the illuminator 3508 and the camera 3506 are used in combination, image capture can be performed by the camera 3506 with the illuminator 3508 flashing or blinking. Because the illuminator 3508 serves as a planar light source, a photograph can be taken in the same way as under natural light.

[0324] It should be noted that the multifunction device 3500, which was Fig. 10A and Fig. 10B, as in the electronic devices used in Fig. 9A to Fig. 9C, can have a variety of functions.

[0325] The housing 3502 may include a speaker, a sensor (a sensor with a function for measuring or detecting force, displacement, position, speed, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, electric power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays), a microphone, and the like. If a detection device including a sensor such as a gyroscope sensor or an acceleration sensor for detecting inclination is provided within the multifunctional device 3500, the display on the screen of the display section 3504 can be automatically changed by determining the orientation of the multifunctional device 3500 (whether the multifunctional device is arranged horizontally or vertically in a landscape or portrait orientation).

[0326] The display section 3504 can serve as an image sensor. For example, an image of a palm print, a fingerprint, or the like is captured by touching the display section 3504 with the palm or finger, thereby performing personal authentication. Furthermore, by providing a backlight or a scanning light source that emits near-infrared light in the display section 3504, an image of a finger vein, a palm vein, or the like can be captured. Note that the light-emitting device of one embodiment of the present invention can be used for the display section 3504.

[0327] Fig. 10C is a perspective view of a security light 3600. The security light 3600 includes an illuminator 3608 on the outside of the housing 3602, and a speaker 3610 and the like are installed in the housing 3602. The light-emitting element of one embodiment of the present invention can be used for the illuminator 3608.

[0328] The safety light 3600 emits light when the light 3608 is grasped or held, for example. An electronic circuit that can control the type of light emission from the safety light 3600 can be provided in the housing 3602. The electronic circuit can be a circuit that allows light emission once or periodically numerous times, or can be a circuit that can adjust the amount of light emitted by controlling the current value for the light emission. A circuit can be incorporated that emits a loud audible alarm from the speaker 3610 simultaneously with the light emission from the light 3608.

[0329] The security light 3600 can emit light in various directions; thus, it is possible to intimidate a criminal or the like with light, or light and noise. Furthermore, the security light 3600 can incorporate a camera, such as a digital still camera, to provide a photography function.

[0330] Fig. 11 illustrates an example in which the light-emitting element is used for an indoor lighting device 8501. Since the light-emitting element can have a larger area, a lighting device with a large area can also be formed. In addition, a lighting device 8502 in which a light-emitting region has a curved surface can also be formed using a housing with a curved surface. A light-emitting element described in this embodiment has a thin film shape, which makes it possible to design the housing more freely. Consequently, the lighting device can be artistically designed in various ways. Furthermore, a wall of the room can be provided with a large lighting device 8503.Touch sensors may be provided in the lighting devices 8501, 8502 and 8503 to control the switching on or off of the lighting devices.

[0331] Furthermore, when the light-emitting element is used on the surface side of a table, a lighting device 8504 having a function as a table can be obtained. When the light-emitting element is used as part of another piece of furniture, a lighting device having a function as a piece of furniture in question can be obtained.

[0332] As described above, lighting devices and electronic devices can be obtained using the light-emitting device of one embodiment of the present invention. Note that the light-emitting device can be used for lighting devices and electronic devices in various fields, without being limited to the lighting devices and electronic devices described in this embodiment.

[0333] The structure described above in this embodiment may be appropriately combined with any of the structures described in the other embodiments. [Example 1]

[0334] In this example, examples of the production of the light-emitting elements 2 to 4 of an embodiment of the present invention and a comparative light-emitting element 1 are described. In Fig. Figure 12 shows a schematic cross-sectional view of the light-emitting elements prepared in this example. Details of the element structures are shown in Table 4. Chemical formulas of the organic compounds used in this example are shown below. Note that for the structures and abbreviations of the other compounds, reference can be made to Embodiment 1. [Table 4] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting reference element 1 electrode 102 200 Al - Electron injection layer 130 1 LiF - Electron transport layer 118(2) 20 NBPhen - 118(1) 25 2mDBTBPDBq-II - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF :Ir(dmdppr-dmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II: MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting element 2 electrode 102 200 Al - Electron injection layer 130 10 NBPhen:Ag 1:0,38 Electron transport layer 118(2) 10 NBPhen - 118(1) 25 2mDBTBPDBq-II - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdppr-dmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II: MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting element 3 electrode 102 200 Al - Electron injection layer 130 10 Alq3:Ag 1:0,48 Electron transport layer 118(2) 10 NBPhen - 118(1) 25 2mDBTBPDBq-II - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdppr-dmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II: MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting element 4 electrode 102 200 Al - Electron injection layer 130 10 2mDBTBPDBq-II:Ag 1:0,40 Electron transport layer 118(2) 10 NBPhen - 118(1) 25 2mDBTBPDBq-II - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdppr-dmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II: MoO3 1:0,5 electrode 101 70 ITSO -

[0335] The LUMO levels of the organic compounds used in the electron injection layer 130 of the light-emitting elements 2 to 4 were calculated by cyclic voltammetry (CV) measurement.

[0336] An electrochemical analyzer (ALS Model 600A or 600C, manufactured by BAS Inc.) was used as the measuring device. To prepare a solution for CV measurement, anhydrous dimethylformamide (DMF, manufactured by Sigma-Aldrich Inc., 99.8%, Catalog No. 22705-6) was used as the solvent, and tetra-n-butylammonium perchlorate (n-Bu4NCIO4, manufactured by Tokyo Chemical Industry Co., Ltd., Catalog No. T0836) was dissolved as the supporting electrolyte at a concentration of 100 mmol / L. Furthermore, the object to be measured was also dissolved at a concentration of 2 mmol / L. A platinum electrode (PTE platinum electrode, manufactured by BAS Inc.) was used as the working electrode, another platinum electrode (Pt counter electrode for VC-3 (5 cm), manufactured by BAS Inc.) was used as the auxiliary electrode, and an Ag / Ag electrode was used. + An electrode (RE7 reference electrode for a non-aqueous solvent, manufactured by BAS Inc.) was used as the reference electrode. Note that the measurement was performed at room temperature (20°C to 25°C). In addition, the scanning speed in the CV measurement was set to 0.1 V / s, and an oxidation potential Ea [V] and a reduction potential Ec [V] with respect to the reference electrode were measured. The potential Ea is an intermediate potential of an oxidation-reduction wave, and the potential Ec is an intermediate potential of a reduction-oxidation wave. Here, since the potential energy of the reference electrode used in this example is known to be -4.94 [eV] with respect to the vacuum level, the HOMO level and the LUMO level can be calculated by the following formulas: HOMO level [eV] = -4.94 - Ea and LUMO level [eV] = -4.94 - Ec.

[0337] From the above measurement, the LUMO levels of NBPhen, Alq3 and 2mDBTBPDBq-II were calculated to be -2.83 eV, -2.80 eV and -2.94 eV, respectively. <Herstellung der Licht emittierenden Elemente>

[0338] Methods for manufacturing the light-emitting elements of this example are described below. Comparative light-emitting element 1 uses LiF, a Li compound typically used for the electron injection layer. Light-emitting elements 2 to 4 each use a composite material of a transition metal and an organic compound having an unshared electron pair according to an embodiment of the present invention for the electron injection layer. <<Herstellung des Licht emittierenden Vergleichselements 1> >

[0339] As the electrode 101, an ITSO film with a thickness of 70 nm was formed over a substrate 210. It should be noted that the electrode area of ​​the electrode 101 was set to 4 mm 2 (2 mm × 2 mm) was set.

[0340] Next, DBT3P-II and molybdenum oxide (MoO3) were deposited as the hole injection layer 111 over the electrode 101 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 to a thickness of 60 nm.

[0341] As hole transport layer 112, BPAFLP was then deposited by evaporation to a thickness of 20 nm over the hole injection layer 111.

[0342] As the light-emitting layer 140, 2mDBTBPDBq-II, PCBBiF and bis{4,6-dimethyl-2-[5-(2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2',6,6'-tetramethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: Ir(dmdppr-dmp)2(dpm)) is deposited by co-evaporation over the hole-transport layer 112 in a weight ratio of 2mDBTBPDBq-II:PCBBiF:Ir(dmdppr-dmp)2(dpm) = 0.75:0.25:0.06 to a thickness of 40 nm. Note that in the light-emitting layer 140, 2mDBTBPDBq-II and PCBBiF are host materials, and Ir(dmdppr-dmp)2(dpm) is a guest material (a phosphorescent material).

[0343] Next, 2mDBTBPDBq-II was deposited as the electron transport layer 118(1) by evaporation to a thickness of 25 nm over the light-emitting layer 140.

[0344] NBPhen was then deposited as electron transport layer 118(2) by evaporation to a thickness of 20 nm over the electron transport layer 118(1).

[0345] Lithium fluoride (LiF) was deposited as electron injection layer 130 by evaporation to a thickness of 1 nm over the electron transport layer 118(2).

[0346] Next, aluminum (Al) was deposited as electrode 102 by evaporation to a thickness of 200 nm over the electron injection layer 130.

[0347] Subsequently, a heat treatment was performed for one hour at 80 °C in air without sealing. Through the above steps, the comparative light-emitting element 1 was obtained. <<Herstellung des Licht emittierenden Elements 2> >

[0348] The light-emitting element 2 was manufactured through the same steps as those of the comparative light-emitting element 1, except for the steps of forming the electron transport layer 118(2) and the electron injection layer 130.

[0349] As the electron transport layer 118(2) of the light-emitting element 2, NBPhen was deposited by evaporation to a thickness of 10 nm over the electron transport layer 118(1).

[0350] As electron injection layer 130, NBPhen and Ag were deposited by co-evaporation in a weight ratio of NBPhen:Ag = 1:0.38 in a thickness of 10 nm over the electron transport layer 118(2). <<Herstellung der Licht emittierenden Elemente 3 und 4> >

[0351] The light-emitting elements 3 and 4 were manufactured through the same steps as those of the light-emitting element 2, except for the step of forming the electron injection layer 130. <Herstellung des Licht emittierenden Elements 3>

[0352] As the electron injection layer 130, Alq3 and Ag were deposited by co-evaporation in a weight ratio of Alq3:Ag = 1:0.48 in a thickness of 10 nm over the electron transport layer 118(2) of the light-emitting element 3. <Herstellung des Licht emittierenden Elements 4>

[0353] As the electron injection layer 130, 2mDBTBPDBq-II and Ag were deposited by co-evaporation in a weight ratio of 2mDBTBPDBq-II: Ag = 1:0.40 in a thickness of 10 nm over the electron transport layer 118(2) of the light-emitting element 4. <Eigenschaften der Licht emittierenden Elemente>

[0354] Subsequently, the elemental properties of the fabricated comparative light-emitting element 1 and the fabricated light-emitting elements 2 to 4 were measured. The luminance and CIE chromaticity were measured using a luminance colorimeter (BM-5A, manufactured by TOPCON TECHNOHOUSE CORPORATION), and the electroluminescence spectra were measured using a multi-channel spectrometer (PMA-11, manufactured by Hamamatsu Photonics KK).

[0355] Fig. 13 shows the current efficiency-luminance characteristics of the fabricated comparative light-emitting element 1 and the fabricated light-emitting elements 2 to 4; Fig. 14 shows the current density-voltage characteristics thereof; Fig. 15 shows the energy efficiency-luminance characteristics thereof; and Fig. Figure 16 shows the external quantum efficiency-luminance characteristics of these devices. Note that the measurements of the light-emitting elements were performed at room temperature (in an atmosphere maintained at 23 °C). Fig. Figure 17 shows the electroluminescence spectra of the light-emitting elements through which a current at a current density of 2.5 mA / cm 2 flows. It should be noted that the measurement was carried out at room temperature.

[0356] Table 5 shows the element properties of the comparative light-emitting element 1 and the light-emitting elements 2 to 4 at about 1000 cd / m 2 . [Table 5] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x, y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) external quantum efficiency (%) Light-emitting reference element 1 3,3 2,1 (0,67, 0,33) 747 35 34 31 Light-emitting element 2 3,6 3,0 (0,67, 0,33) 1021 34 30 29 Light-emitting element 3 5,6 3,7 (0,66, 0,34) 1017 28 17 23 Light-emitting element 4 4,4 3,3 (0,66, 0,34) 1072 32 23 27

[0357] As in Fig. 16 and Table 5, the comparative light-emitting element 1 and the light-emitting elements 2 to 4 each exhibited high emission efficiency with an external quantum efficiency of over 20%. The comparative light-emitting element 1 and the light-emitting elements 2 to 4 also exhibited high current efficiency and high energy efficiency, as shown in the Fig. 13 and Fig. 15. In particular, comparative light-emitting element 1, light-emitting element 2, and light-emitting element 4 exhibited significantly high external quantum efficiencies exceeding 25%. Light-emitting elements 2 and 4 of one embodiment of the present invention exhibited high efficiencies equivalent to those of comparative light-emitting element 1 using LiF, which is typically used for the electron injection layer.

[0358] As in Fig. As shown in Figure 14, comparative light-emitting element 1 and light-emitting elements 2 to 4 exhibited favorable current density-voltage characteristics. In particular, the current density-voltage characteristics of light-emitting element 2 are similar to those of comparative light-emitting element 1, indicating that the NBPhen-Ag composite material exhibits significantly high electron injection characteristics.

[0359] As in Fig. As shown in Figure 17, comparative light-emitting element 1 and light-emitting elements 2 to 4 each exhibited red emission, the electroluminescence spectrum of which had a peak wavelength at approximately 619 nm and a half-width of 58 nm. The obtained electroluminescence spectrum revealed that the light was emitted from the guest material Ir(dmdppr-dmp)2(dmp). <Zuverlässigkeitstests der Licht emittierenden Elemente>

[0360] A constant temperature and humidity preservation test was conducted on the reference light-emitting element 1 and light-emitting elements 2 to 4. Since each of the light-emitting elements is unsealed, the cathode and EL layer are exposed to the atmosphere of the test environment. Generally, moisture entering the light-emitting element causes dark spots (non-emission areas in a light-emitting section) or shrinkage (non-emission areas at the end of the light-emitting section), which negatively affects the reliability of the light-emitting element. Thus, the constant temperature and humidity preservation test enables an evaluation of the light-emitting element's reliability against moisture.

[0361] The reference light-emitting element 1 and the light-emitting elements 2 to 4 were placed in a thermostatic bath maintained at a temperature of 65 °C and a humidity of 95% for 48 hours; then, the emission state of each light-emitting element was measured.

[0362] The emission state was measured by estimating the proportion of the emission area before and after the preservation test at constant temperature and humidity. The results are shown in Table 6. [Table 6] Share of emission area Light-emitting reference element 1 6% Light-emitting element 2 56 % Light-emitting element 3 83 % Light-emitting element 4 68 %

[0363] In Table 6, the emission area ratio (%) is the emission area after the constant temperature and humidity preservation test / the emission area before the constant temperature and humidity preservation test × 100. Table 6 shows that the light-emitting elements 2 to 4 of one embodiment of the present invention each have a larger emission area than the comparative light-emitting element 1 that uses LiF, an alkali metal compound, for the electron injection layer. This indicates that the light-emitting elements of one embodiment of the present invention have higher moisture resistance than the light-emitting element that uses a material with a low work function, such as an alkali metal, for the electron injection layer.This is because the material with a low work function reacts strongly with water, allowing moisture to penetrate into the light-emitting element. In contrast, moisture hardly penetrates the light-emitting elements of one embodiment of the present invention that use a transition metal that is prone to reacting with water. Thus, highly moisture-resistant light-emitting elements can be realized. <Absorptionsspektrum des Verbundmaterials aus der organischen Verbindung und dem Übergangsmetall>

[0364] Subsequently, the absorption spectrum of a thin film composed of a composite material of an organic compound and Ag, which is used for the electron injection layers of the light-emitting elements 2 to 4, was measured. In addition, the absorption spectra of an Ag thin film and an organic compound thin film were measured. The results are shown in Fig. 18 to Fig. 20. The thin film consisting of the composite material of the organic compound and Ag was formed over a quartz substrate by vacuum evaporation at a molar ratio of the organic compound:Ag = 1:1 to a thickness of 50 nm. The thin film of the organic compound was formed over a quartz substrate by vacuum evaporation to a thickness of 50 nm. The Ag thin film was formed over a quartz substrate by vacuum evaporation to a thickness of 2 nm. Note that the amount of Ag contained in the 2 nm thick Ag thin film is approximately equal to the amount of Ag contained in the 50 nm thick thin film consisting of the composite material of the organic compound and Ag. The absorption spectrum was measured with a spectrophotometer (U-4100 spectrophotometer, manufactured by Hitachi High-Technologies Corporation).

[0365] As in Fig. As shown in Figures 18 to 20, a surface plasmon peak specific to a metal thin film was observed at about 450 nm for the Ag thin film. In contrast, the surface plasmon peak was not observed for the organic compound-Ag composite material. Surface plasmons are observed on the surface of a tiny (nanometer-sized) metal, such as a metal thin film or a metal nanoparticle. Therefore, in the organic compound-Ag composite material, Ag does not exist as a group of Ag atoms like an Ag thin film or Ag nanoparticle, but in a state such that an Ag atom interacts with the organic compound. In other words, in the organic compound-Ag composite film, they interact with each other as a transition metal.

[0366] For this reason, the light-emitting element of one embodiment of the present invention has advantageous electron injection characteristics and therefore has a low operating voltage and high emission efficiency. Furthermore, the light-emitting element is highly moisture-resistant because it does not use a low-work-function material. The structures shown in this example can be appropriately combined with any of the other embodiments and examples. [Example 2]

[0367] In this example, examples of manufacturing a light-emitting element 6 of an embodiment of the present invention and a comparative light-emitting element 5 are described. In Fig. Figure 12 shows a schematic cross-sectional view of the light-emitting elements fabricated in this example. Details of the element structures are shown in Table 7. The structure and abbreviation of a compound used in this example are shown below. Note that for the structures and abbreviations of the other compounds, reference can be made to the above embodiments. [Table 7] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting reference element 5 electrode 102 200 Al - Electron injection layer 130 1 LiF - Electron transport layer 118 40 4mCzBPBfpm - Light-emitting layer 140 40 4mCzBPBfpm:PCBBi F: Ir(dmdppr-dmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II: MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting element 6 electrode 102 200 Al - Electron injection layer 130 15 4mCzBPBfpm:Ag 1:0,22 Electron transport layer 118 25 4mCzBPBfpm - Light-emitting layer 140 40 4mCzBPBfpm:PCBBi F: Ir(dmdppr-dmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II: MoO3 1:0,5 electrode 101 70 ITSO -

[0368] The LUMO level of 4mCzBPBfpm used in the electron injection layer 130 of the light-emitting element 6 was calculated by cyclic voltammetry (CV) measurement. The measurement was performed in a similar manner to Example 1.

[0369] As a result, the LUMO levels of 4mCzBPBfpm and Alq3 were calculated to be -2.83 eV and -2.97 eV, respectively. <Herstellung der Licht emittierenden Elemente>

[0370] Methods for manufacturing the light-emitting elements of this example are described below. In this example, the electron-transport layer is a single layer. The comparative light-emitting element 5 uses LiF, a Li compound typically used for the electron-injection layer. The light-emitting element 6 uses a composite material of a transition metal and an organic compound having an unshared electron pair according to an embodiment of the present invention for the electron-injection layer. In the light-emitting elements of this example, an organic compound having a pyrimidine ring is used as the organic compound having an unshared electron pair. <<Herstellung des Licht emittierenden Vergleichselements 5> >

[0371] As the electrode 101, an ITSO film with a thickness of 70 nm was formed over the substrate 210. It should be noted that the electrode area of ​​the electrode 101 was set to 4 mm 2 (2 mm × 2 mm) was set.

[0372] Next, DBT3P-II and MoO3 were deposited as the hole injection layer 111 over the electrode 101 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 to a thickness of 70 nm.

[0373] As hole transport layer 112, BPAFLP was then deposited by evaporation to a thickness of 20 nm over the hole injection layer 111.

[0374] As the light-emitting layer 140, 4mCzBPBfpm, PCBBiF, and Ir(dmdppr-dmp)2(dpm) were then co-evaporated over the hole-transport layer 112 in a weight ratio of 4mCzBPBfpm:PCBBiF:Ir(dmdppr-dmp)2(dpm) = 0.75:0.25:0.06 to a thickness of 40 nm. Note that in the light-emitting layer 140, 4mCzBPBfpm and PCBBiF are host materials, and Ir(dmdppr-dmp)2(dpm) is a guest material (a phosphorescent material).

[0375] Next, 4mCzBPBfpm was deposited as the electron transport layer 118 by evaporation to a thickness of 40 nm over the light-emitting layer 140.

[0376] Lithium fluoride (LiF) was deposited as electron injection layer 130 by evaporation to a thickness of 1 nm over the electron transport layer 118.

[0377] Next, aluminum (Al) was deposited as electrode 102 by evaporation to a thickness of 200 nm over the electron injection layer 130.

[0378] Subsequently, a heat treatment was performed for one hour at 80 °C in air without sealing. Through the above steps, comparative light-emitting element 5 was obtained. <<Herstellung des Licht emittierenden Elements 6> >

[0379] The light-emitting element 6 was manufactured through the same steps as those of the comparative light-emitting element 5, except for the steps of forming the electron transport layer 118 and the electron injection layer 130.

[0380] As the electron transport layer 118 of the light-emitting element 6, 4mCzBPBfpm was deposited by evaporation to a thickness of 25 nm over the light-emitting layer 140.

[0381] As electron injection layer 130, 4mCzBPBfpm and Ag were deposited by co-evaporation in a weight ratio of 4mCzBPBfpm: Ag = 1:0.22 in a thickness of 15 nm over the electron transport layer 118. <Eigenschaften der Licht emittierenden Elemente>

[0382] Subsequently, the element properties of the fabricated comparative light-emitting element 5 and the fabricated light-emitting element 6 were measured. The measurement was carried out in a similar manner to Example 1.

[0383] Fig. 21 shows the current efficiency-luminance characteristics of the fabricated comparative light-emitting element 5 and the fabricated light-emitting element 6; Fig. 22 shows the current-voltage characteristics thereof; Fig. 23 shows the energy efficiency-luminance characteristics thereof; and Fig. Figure 24 shows the external quantum efficiency-luminance characteristics thereof. Fig. Figure 25 shows the electroluminescence spectra of the light-emitting elements through which a current at a current density of 2.5 mA / cm 2 flows.

[0384] Table 8 shows the element properties of the comparative light-emitting element 5 and the light-emitting element 6 at about 1000 cd / m 2 . [Table 8] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x, y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) external quantum efficiency (%) Light-emitting reference element 5 6,6 5,9 (0,66, 0,34) 1092 19 9 14 Light-emitting element 6 4,2 3,6 (0,66, 0,34) 872 24 18 18

[0385] As in Fig. As shown in Figure 22, the light-emitting element 6 exhibited favorable current density-voltage characteristics compared to the comparative light-emitting element 5. This indicates that, when the host material of the light-emitting layer is used for the electron-transport layer and the electron-injection layer is in contact with the electron-transport layer, the light-emitting element of one embodiment of the present invention exhibits electron-injection characteristics superior to those of the light-emitting element using LiF, which is a typical material for the electron-injection layer.

[0386] As in Fig. 21, Fig. 23 and Fig. 24 and Table 8, the light-emitting element 6 exhibited higher emission efficiency (current efficiency, power efficiency, and external quantum efficiency) than the comparative light-emitting element 5. That is, as described above, the light-emitting element 6 exhibits superior electron injection characteristics to the comparative light-emitting element 5 and thus exhibits a favorable charge carrier balance.

[0387] As in Fig. As shown in Figure 25, the comparative light-emitting element 5 and the light-emitting element 6 each exhibited red emission, the electroluminescence spectrum of which had a peak wavelength at approximately 616 nm and a half-width of 53 nm. The obtained electroluminescence spectrum revealed that the light was emitted from the guest material Ir(dmdppr-dmp)2(dmp).

[0388] Then, the endurance tests of the reference light-emitting element 5 and the light-emitting element 6 were carried out. The measurement results of the endurance tests are shown in Fig. 43. It should be noted that during the duration tests, each light-emitting element was continuously operated at a constant current density of 25 mA / cm 2 was operated.

[0389] As in Fig. 43, the light-emitting element 6, which has a longer operating life than the comparative light-emitting element 5, had a favorable operating life.

[0390] That is, the light-emitting element including the electron injection layer of one embodiment of the present invention had a favorable operating life. <Absorptionsspektrum des Verbundmaterials aus der organischen Verbindung und dem Übergangsmetall>

[0391] Subsequently, the absorption spectrum of a composite material of 4mCzBPBfpm and Ag, which is used for the electron injection layer of the light-emitting element 6, was measured. The results are shown in Fig. 26. The preparation and measurement of the samples were carried out in a similar manner as in Example 1.

[0392] As in Fig. As shown in Figure 26, a surface plasmon peak specific to a metal thin film was observed at about 450 nm for the Ag thin film. In contrast, the surface plasmon peak was not observed for the 4mCzBPBfpm and Ag composite material as in Example 1. Therefore, in the thin film composed of the 4mCzBPBfpm and Ag composite material, 4mCzBPBfpm and Ag likely interact with each other.

[0393] For this reason, the light-emitting element of one embodiment of the present invention can be advantageously used as an element in which a host material of a light-emitting layer is used for an electron-injection layer and an electron-transport layer, and the electron-injection layer is in contact with the electron-transport layer. Furthermore, a material having a pyrimidine ring can be advantageously used for the light-emitting element of one embodiment of the present invention. The structures shown in this example can be appropriately combined with any of the other embodiments and examples. [Example 3]

[0394] In this example, examples of the production of the light-emitting elements 8 to 10 of an embodiment of the present invention and a comparative light-emitting element 7 are described. In Fig. Figure 12 shows a schematic cross-sectional view of the light-emitting elements fabricated in this example. Details of the element structures are shown in Table 9. Note that for the structures and abbreviations of the compounds used in this example, reference can be made to the above embodiments and examples. [Table 9] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting reference element 7 electrode 102 200 Al - Electron injection layer 130 1 Li2O - Electron transport layer 118(2) 20 NBPhen - 118(1) 20 2mDBTBPDBq-II - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdpprdmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II: MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting element 8 electrode 102 200 Al - Electron injection layer 130 5 NBPhen:Ag 1:0,19 Electron transport layer 118(2) 15 NBPhen - 118(1) 20 2mDBTBPDBq-II - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdpprdmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II: MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting element 9 electrode 102 200 Al - Electron injection layer 130 5 2Py3Tzn:Ag 1:0,35 Electron transport layer 118(3) 5 NBPhen:Ag 1:0,19 118(2) 10 NBPhen - 118(1) 20 2mDBTBPDBq-II - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdpprdmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II: MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting element 10 electrode 102 200 Al - Electron injection layer 130 5 TmPPPyTz:Ag 1:0,15 Electron transport layer 118(2) 15 NBPhen - 118(1) 20 2mDBTBPDBq-II - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdpprdmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II: MoO3 1:0,5 electrode 101 70 ITSO -

[0395] The LUMO levels of the organic compounds used in the electron injection layer 130 of the light-emitting elements 9 and 10 were calculated by cyclic voltammetry (CV) measurement. The measurement was performed in a similar manner to Example 1.

[0396] As a result, the LUMO levels of 2Py3Tzn and TmPPPyTz were calculated to be -3.15 eV and -3.00 eV, respectively. <Herstellung der Licht emittierenden Elemente>

[0397] Methods for manufacturing the light-emitting elements of this example are described below. The comparative light-emitting element 7 uses Li2O, a Li compound typically used for the electron injection layer. The light-emitting elements 8 to 10 each use a composite material of a transition metal and an organic compound having an unshared electron pair according to an embodiment of the present invention for the electron injection layer. In the light-emitting elements of this example, an organic compound having a triazine ring is used as the organic compound having an unshared electron pair. <<Herstellung des Licht emittierenden Vergleichselements 7> >

[0398] The comparative light-emitting element 7 was manufactured through the same steps as those of the comparative light-emitting element 1, except for the steps of forming the electron transport layer 118 and the electron injection layer 130.

[0399] As electron-transport layer 118(1), 2mDBTBPDBq-II was deposited by evaporation to a thickness of 20 nm over the light-emitting layer 140. Subsequently, NBPhen was deposited by evaporation to a thickness of 20 nm as electron-transport layer 118(2). Li2O was then deposited by evaporation to a thickness of 0.2 nm over the electron-transport layer 118(2) as electron-injection layer 130. <<Herstellung der Licht emittierenden Elemente 8 bis 10> >

[0400] The light-emitting elements 8 to 10 were manufactured through the same steps as those of the comparative light-emitting element 7, except for the steps of forming the electron transport layer 118(2) and the electron injection layer 130. <Herstellung des Licht emittierenden Elements 8>

[0401] As the electron transport layer 118(2) of the light-emitting element 8, NBPhen was deposited by evaporation to a thickness of 15 nm over the electron transport layer 118(1).

[0402] As electron injection layer 130, NBPhen and Ag were deposited by co-evaporation in a weight ratio of NBPhen:Ag = 1:0.19 in a thickness of 5 nm over the electron transport layer 118(2). <Herstellung des Licht emittierenden Elements 9>

[0403] As the electron-transport layer 118(2) of the light-emitting element 9, NBPhen was deposited by evaporation to a thickness of 10 nm over the electron-transport layer 118(1). Subsequently, as the electron-transport layer 118(3), NBPhen and Ag were co-evaporated to a thickness of 5 nm in a weight ratio of NBPhen:Ag = 1:0.19.

[0404] As electron injection layer 130, 2Py3Tzn and Ag were deposited by co-evaporation in a weight ratio of 2Py3Tzn: Ag = 1:0.35 in a thickness of 5 nm over the electron transport layer 118(3). <Herstellung des Licht emittierenden Elements 10>

[0405] As the electron transport layer 118(2) of the light-emitting element 10, NBPhen was deposited by evaporation to a thickness of 15 nm over the electron transport layer 118(1).

[0406] As the electron injection layer 130, TmPPPyTz and Ag were deposited by co-evaporation in a weight ratio of TmPPPyTz: Ag = 1:0.15 in a thickness of 5 nm over the electron transport layer 118(2). <Eigenschaften der Licht emittierenden Elemente>

[0407] Subsequently, the element properties of the fabricated comparative light-emitting element 7 and the fabricated light-emitting elements 8 to 10 were measured. The measurement was carried out in a similar manner to Example 1.

[0408] Fig. Fig. 27 shows the current efficiency-luminance characteristics of the fabricated comparative light-emitting element 7 and the fabricated light-emitting elements 8 to 10; Fig. 28 shows the current density-voltage characteristics thereof; Fig. 29 shows the energy efficiency-luminance characteristics thereof; and Fig. 30 shows the external quantum efficiency-luminance characteristics thereof. Fig. Figure 31 shows the electroluminescence spectra of the light-emitting elements through which a current at a current density of 2.5 mA / cm 2 flows.

[0409] Table 10 shows the element properties of the comparative light-emitting element 7 and the light-emitting elements 8 to 10 at about 1000 cd / m 2 . [Table 10] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x, y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) external quantum efficiency (%) Light-emitting reference element 7 3,2 2,5 (0,66, 0,34) 964 39 38 31 Light-emitting element 8 3,3 2,9 (0,66, 0,34) 1111 38 36 30 Light-emitting element 9 3,3 3,0 (0,66, 0,34) 1123 37 35 29 Light-emitting element 10 3,3 2,6 (0,66, 0,34) 988 38 36 30

[0410] As in Fig. 30 and Table 10, the comparative light-emitting element 7 and the light-emitting elements 8 to 10 each exhibited high emission efficiency with an external quantum efficiency of over 25%. The comparative light-emitting element 7 and the light-emitting elements 8 to 10 also exhibited high current efficiency and high energy efficiency, as shown in the Fig. 27 and Fig. 29. The light-emitting elements 8 to 10 of one embodiment of the present invention showed high efficiency equivalent to that of the comparative light-emitting element 7 using Li2O typically used for the electron injection layer.

[0411] As in Fig. As shown in Figure 28, the comparative light-emitting element 7 and the light-emitting elements 8 to 10 exhibited favorable current density-voltage characteristics. It was also found that the light-emitting elements 8 to 10 of one embodiment of the present invention exhibited electron injection characteristics similar to those of the comparative light-emitting element 7 using Li2O, which is typically used for the electron injection layer.

[0412] As in Fig. As shown in Figure 31, comparative light-emitting element 7 and light-emitting elements 8 to 10 each exhibited red emission, the electroluminescence spectrum of which had a peak wavelength at approximately 616 nm and a half-width of 53 nm. The obtained electroluminescence spectrum revealed that the light was emitted from the guest material Ir(dmdppr-dmp)2(dmp).

[0413] Then, the endurance tests of the reference light-emitting element 7 and the light-emitting elements 8 to 10 were carried out. The measurement results of the endurance tests are shown in Fig. 44. It should be noted that during the duration tests, each light-emitting element was continuously operated at a constant current density of 25 mA / cm 2 was operated.

[0414] As in Fig. 44, the light-emitting elements 8 to 10 showed an operating life similar to that of the comparative light-emitting element 7.

[0415] For this reason, an organic compound having a triazine ring can be advantageously used for the light-emitting element of one embodiment of the present invention. The structures shown in this example can be appropriately combined with any of the other embodiments and examples. [Example 4]

[0416] In this example, examples of the manufacture of the light-emitting elements 12 to 14 of an embodiment of the present invention and a comparative light-emitting element 11 are described. In Fig. Figure 12 shows a schematic cross-sectional view of the light-emitting elements fabricated in this example. Details of the element structures are shown in Table 11. The structure and abbreviation of a compound used in this example are shown below. Note that for the structures and abbreviations of the other compounds, reference can be made to the above embodiments and examples. [Table 11] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting reference element 11 electrode 102 200 Al - Electron transport layer 118(2) 15 NBPhen - 118(1) 20 2mDBTBPDBq-II - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdpprdmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II : MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting element 12 electrode 102 200 Al - Electron injection layer 130 5 NBPhen:Ag 1:0,19 Electron transport layer 118(2) 15 NBPhen - 118(1) 20 2mDBTBPDBq-II - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdpprdmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II : MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting element 13 electrode 102 200 Al - Electron injection layer 130(2) 5 HATNA:Ag 1:0,28 130(1) 5 NBPhen:Ag 1:0,19 Electron transport layer 118(2) 10 NBPhen - 118(1) 20 2mDBTBPDBq-II - Light-emitting layer 140(1) 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdpprdmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II : MoO3 1:0,5 electrode 101 70 ITSO - Light-emitting element 14 electrode 102 200 Al - buffer layer 117 5 HAT-CN - Electron injection layer 130(2) 5 HATNA:Ag 1:0,28 130(1) 5 NBPhen:Ag 1:0,19 Electron transport layer 118(2) 10 NBPhen - 118(1) 20 2mDBTBPDBq-II - Light-emitting layer 140(1) 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdpprdmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II : MoO3 1:0,5 electrode 101 70 ITSO -

[0417] The LUMO level of HATNA used in the electron injection layer 130 of the light-emitting elements 13 and 14 was calculated by cyclic voltammetry (CV) measurement. The measurement was performed in a similar manner to Example 1.

[0418] As a result, the LUMO level of HATNA was calculated to be -3.50 eV. <<Herstellung des Licht emittierenden Vergleichselements 11> >

[0419] The comparative light-emitting element 11 was manufactured through the same steps as those of the comparative light-emitting element 1, except for the steps of forming the electron transport layer 118 and the electron injection layer 130.

[0420] As the electron transport layer 118(1) of the comparative light-emitting element 11, 2mDBTBPDBq-II was deposited by evaporation to a thickness of 20 nm.

[0421] Next, NBPhen was deposited as the electron-transport layer 118(2) by evaporation to a thickness of 15 nm over the electron-transport layer 118(1). In the comparative light-emitting element 11, the electron-injection layer 130 was not provided over the electron-transport layer 118(2). <<Herstellung des Licht emittierenden Elements 12> >

[0422] The light-emitting element 12 was manufactured through the same steps as those of the comparative light-emitting element 11, except for the step of forming the electron injection layer 130.

[0423] As the electron injection layer 130 of the light-emitting element 12, NBPhen and Ag were deposited by co-evaporation in a weight ratio of NBPhen:Ag = 1:0.19 to a thickness of 5 nm over the electron transport layer 118(2). <Herstellung des Licht emittierenden Elements 13>

[0424] The light-emitting element 13 was manufactured through the same steps as those of the comparative light-emitting element 11, except for the steps of forming the electron transport layer 118(2) and the electron injection layer 130.

[0425] As the electron transport layer 118(2) of the light-emitting element 13, NBPhen was deposited by evaporation to a thickness of 10 nm over the electron transport layer 118(1).

[0426] As the electron injection layer 130, NBPhen and Ag were co-evaporated in a weight ratio of NBPhen:Ag = 1:0.19 to a thickness of 5 nm over the electron transport layer 118(2). HATNA and Ag were further co-evaporated in a weight ratio of HATNA:Ag = 1:0.28 to a thickness of 5 nm. <<Herstellung des Licht emittierenden Elements 14> >

[0427] The light-emitting element 14 was manufactured through the same steps as those of the light-emitting element 13, except for the step of additionally forming the buffer layer 117.

[0428] As buffer layer 117, HAT-CN was deposited by evaporation to a thickness of 5 nm over the electron injection layer 130. <Eigenschaften der Licht emittierenden Elemente>

[0429] Subsequently, the element properties of the fabricated comparative light-emitting element 11 and the fabricated light-emitting elements 12 to 14 were measured. The measurement was carried out in a similar manner to Example 1.

[0430] Fig. 32 shows the current efficiency-luminance characteristics of the fabricated comparative light-emitting element 11 and the fabricated light-emitting elements 12 to 14; Fig. 33 shows the current-voltage characteristics thereof; Fig. 34 shows the energy efficiency-luminance characteristics thereof; and Fig. 35 shows the external quantum efficiency-luminance characteristics thereof. Fig. Figure 36 shows the electroluminescence spectra of the light-emitting elements through which a current at a current density of 2.5 mA / cm 2 flows.

[0431] Table 12 shows the element properties of the comparative light-emitting element 11 and the light-emitting elements 12 to 14 at about 1000 cd / m 2 . [Table 12] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x, y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) external quantum efficiency (%) Light-emitting reference element 11 9,4 5,8 (0,66, 0,34) 904 16 5 12 Light-emitting element 12 3,2 2,4 (0,66, 0,34) 912 38 38 31 Light-emitting element 13 3,2 2,4 (0,66, 0,34) 920 38 37 30 Light-emitting element 14 3,2 2,5 (0,66, 0,34) 876 36 36 30

[0432] As in Fig. 35 and Table 12, the light-emitting elements 12 to 14 each exhibited high emission efficiency with an external quantum efficiency of about 30%. The light-emitting elements 12 to 14 also exhibited high current efficiency and high energy efficiency, as shown in Fig. 32 and Fig. 34. In contrast, the comparative light-emitting element 11, which does not include the electron injection layer 130, exhibits low efficiency, indicating that the light-emitting element including the electron injection layer of one embodiment of the present invention has a favorable charge carrier balance. Furthermore, the efficiency of the light-emitting elements 13 and 14 is equivalent to that of the light-emitting element 12; thus, HATNA can be advantageously used as an organic compound having an unshared electron pair. The light-emitting element 14, which includes the buffer layer provided between the cathode and the electron injection layer, exhibited similar properties to the light-emitting element 12.

[0433] As in Fig. 33, the light-emitting elements 12 to 14 exhibited favorable current-voltage characteristics. Furthermore, the equivalent current-voltage characteristics of the light-emitting elements 12 to 14 indicate that the electron-injection layer including the composite material of HATNA and the transition metal has advantageous properties. The light-emitting element 14 including the buffer layer provided between the cathode and the electron-injection layer also exhibited similar properties to the light-emitting element 12. In contrast, the comparative light-emitting element 11, which does not include the electron-injection layer 130, exhibits a high operating voltage, indicating that the light-emitting element including the electron-injection layer of one embodiment of the present invention has improved electron-injection characteristics.

[0434] As in Fig. As shown in Figure 36, comparative light-emitting element 11 and light-emitting elements 12 to 24 each exhibited red emission, the electroluminescence spectrum of which had a peak wavelength at about 618 nm and a half-width of 58 nm. The obtained electroluminescence spectrum revealed that the light was emitted from the guest material Ir(dmdppr-dmp)2(dmp).

[0435] From the above, it is apparent that an organic compound having a conjugated double bond NCCN via a variety of ring structures, such as HATNA, can be advantageously used for the light-emitting element of one embodiment of the present invention. Furthermore, the light-emitting element of one embodiment of the present invention, which includes the buffer layer provided between the cathode and the electron injection layer comprising the composite material of a transition metal and an organic compound having an unshared electron pair, has high emission efficiency and low operating voltage, and consumes little power. <Zuverlässigkeitstests der Licht emittierenden Elemente>

[0436] Then, the endurance tests of the reference light-emitting element 11 and the light-emitting elements 12 to 14 were carried out. The measurement results of the endurance tests are shown in Fig. 45. It should be noted that during the duration tests, each light-emitting element was continuously operated at a constant current density of 25 mA / cm 2 was operated.

[0437] As in Fig. 45, the light-emitting elements 12 to 14 had a longer operating life than the comparative light-emitting element 11. Moreover, the light-emitting elements 13 and 14 had a longer operating life than the light-emitting element 12, indicating that the light-emitting element including the electron injection layer of one embodiment of the present invention has good reliability.

[0438] Next, a preservation test was conducted at constant temperature and humidity on the light-emitting elements 13 and 14. Since each of the light-emitting elements is unsealed, the cathode and the EL layer are exposed to the atmosphere of the test environment.

[0439] Light-emitting elements 13 and 14 were placed in a thermostatic bath maintained at a temperature of 65°C and a humidity of 95% for 48 hours. Subsequently, the emission state of each light-emitting element was measured. The measurement was performed in a similar manner to Example 1. Table 13 shows the measurement results. [Table 13] Share of emission area Light-emitting element 13 83 % Light-emitting element 14 67 %

[0440] The emission area ratio before and after the preservation test at constant temperature and humidity was estimated to be 83% (the light-emitting element 13) and 67% (the light-emitting element 14). This means that the light-emitting elements of one embodiment of the present invention proved to be highly moisture-resistant.

[0441] The structures shown in this example may be appropriately combined with any of the other embodiments and examples. [Example 5]

[0442] In this example, examples of the manufacture of the light-emitting elements 16 to 18 of an embodiment of the present invention and a comparative light-emitting element 15 are described. In Fig. Figure 37 shows a schematic cross-sectional view of the light-emitting elements manufactured in this example. Details of the element structures are shown in Table 14. The element shown in this example has a so-called inverted multilayer structure in which an EL layer is provided over a cathode (a structure in which an EL layer is provided over an anode is called an ordered multilayer structure). For the structures and abbreviations of the organic compounds used in this example, reference can be made to the above examples and Embodiment 1. [Table 14] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting reference element 15 electrode 102 200 Al - Hole injection layer 111 25 DBT3P-II: MoO3 1:0,5 Hole transport layer 112 20 BPAFLP - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdppr-dmp)2(dpm) 0,75:0,25:0,06 Electron transport layer 118(2) 30 2mDBTBPDBq-II - 118(1) 30 NBPhen Electron injection layer 130(2) 0.2 Li2O - 130(1) 5 NBPhen - electrode 101 70 ITSO - Light-emitting element 16 electrode 102 200 Al - Hole injection layer 111 25 DBT3P-II: MoO3 1:0,5 Hole transport layer 112 20 BPAFLP - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdppr-dmp)2(dpm) 0,75:0,25:0,06 Electron transport layer 118(2) 30 2mDBTBPDBq-II - 118(1) 30 NBPhen Electron injection layer 130 5 NBPhen: Ag 1:0,19 electrode 101 70 ITSO - Light-emitting element 17 electrode 102 200 Al - Hole injection layer 111 25 DBT3P-II: MoO3 1:0,5 Hole transport layer 112 20 BPAFLP - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdppr-dmp)2(dpm) 0,75:0,25:0,06 Electron transport layer 118(2) 30 2mDBTBPDBq-II - 118(1) 25 NBPhen Electron injection layer 130(2) 5 NBPhen:Ag 1:0,19 130(1) 5 2Py3Tz:Ag 1:0,35 electrode 101 70 ITSO - Light-emitting element 18 electrode 102 200 Al - Hole injection layer 111 25 DBT3P-II: MoO3 1:0,5 Hole transport layer 112 20 BPAFLP - Light-emitting layer 140 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdppr-dmp)2(dpm) 0,75:0,25:0,06 Electron transport layer 118(2) 30 2mDBTBPDBq-II - 118(1) 25 NBPhen Electron injection layer 130(2) 5 NBPhen:Ag 1:0,19 130(1) 5 TmPPPyTz:Ag 1:0,15 electrode 101 70 ITSO - <<Herstellung des Licht emittierenden Vergleichselements 15> >

[0443] As the electrode 101, an ITSO film with a thickness of 70 nm was formed over the substrate 210. It should be noted that the electrode area of ​​the electrode 101 was set to 4 mm 2 (2 mm × 2 mm) was set.

[0444] NBPhen was then deposited by evaporation to a thickness of 5 nm over the electrode 101 as the electron injection layer 130. Subsequently, Li2O was deposited by evaporation to a thickness of 0.2 nm.

[0445] Next, NBPhen was deposited by evaporation to a thickness of 30 nm over the electron injection layer 130 as the electron transport layer 118(1). Subsequently, 2mDBTBPDBq-II was deposited by evaporation to a thickness of 30 nm as the electron transport layer 118(2).

[0446] As the light-emitting layer 140, 2mDBTBPDBq-II, PCBBiF, and Ir(dmdppr-dmp)2(dpm) were then co-evaporated over the electron-transport layer 118(2) in a weight ratio of 42mDBTBPDBq-II:PCBBiF:Ir(dmdpprdmp)2(dpm) = 0.75:0.25:0.06 to a thickness of 40 nm. Note that in the light-emitting layer 140, 2mDBTBPDBq-II and PCBBiF are host materials, and Ir(dmdppr-dmp)2(dpm) is a guest material (a phosphorescent compound).

[0447] As hole transport layer 112, BPAFLP was then deposited by evaporation to a thickness of 20 nm over the light-emitting layer 140.

[0448] Next, DBT3P-II and MoO3 were deposited as the hole injection layer 111 over the hole transport layer 112 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 to a thickness of 25 nm.

[0449] Next, aluminum (Al) was deposited as electrode 102 by evaporation to a thickness of 200 nm over the hole injection layer 111.

[0450] Subsequently, a heat treatment was performed for one hour at 80 °C in air without sealing. Through the above steps, comparative light-emitting element 13 was obtained. <<Herstellung der Licht emittierenden Elemente 16 bis 18> >

[0451] The light-emitting elements 16 to 18 were manufactured through the same steps as those of the comparative light-emitting element 15, except for the steps of forming the electron injection layer 130 and the electron transport layer 118(1). <Herstellung des Licht emittierenden Elements 16>

[0452] As the electron injection layer 130 of the light-emitting element 16, NBPhen and Ag were deposited by co-evaporation in a weight ratio of NBPhen:Ag = 1:0.19 to a thickness of 5 nm over the electrode 101.

[0453] As electron transport layer 118(1), NBPhen was deposited by evaporation to a thickness of 30 nm over the electron injection layer 130. <Herstellung des Licht emittierenden Elements 17>

[0454] As the electron injection layer 130 of the light-emitting element 17, 2Py3Tzn and Ag were co-evaporated in a weight ratio of 2Py3Tzn:Ag = 1:0.35 to a thickness of 5 nm over the electrode 101. Subsequently, NBPhen and Ag were co-evaporated in a weight ratio of NBPhen:Ag = 1:0.19 to a thickness of 5 nm.

[0455] As electron transport layer 118(1), NBPhen was deposited by evaporation to a thickness of 25 nm over the electron injection layer 130. <Herstellung des Licht emittierenden Elements 18>

[0456] As the electron injection layer 130 of the light-emitting element 18, TmPPPyTz and Ag were co-evaporated in a weight ratio of TmPPPyTz:Ag = 1:0.15 to a thickness of 5 nm over the electrode 101. Subsequently, NBPhen and Ag were co-evaporated in a weight ratio of NBPhen:Ag = 1:0.19 to a thickness of 5 nm.

[0457] As electron transport layer 118(1), NBPhen was deposited by evaporation to a thickness of 25 nm over the electron injection layer 130. <Eigenschaften der Licht emittierenden Elemente>

[0458] Subsequently, the element properties of the fabricated comparative light-emitting element 15 and the fabricated light-emitting elements 16 to 18 were measured. The measurement was carried out in a similar manner to Example 1.

[0459] Fig. 38 shows the current efficiency-luminance characteristics of the fabricated comparative light-emitting element 15 and the fabricated light-emitting elements 16 to 18; Fig. 39 shows the current-voltage characteristics thereof; Fig. 40 shows the energy efficiency-luminance characteristics thereof; and Fig. 41 shows the external quantum efficiency-luminance characteristics thereof. Fig. Figure 42 shows the electroluminescence spectra of the light-emitting elements through which a current at a current density of 2.5 mA / cm 2 flows.

[0460] Table 15 shows the element properties of the comparative light-emitting element 15 and the light-emitting elements 16 to 18 at about 1000 cd / m 2 . [Table 15] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x, y) Luminance (cd / m 2 ) Power efficiency (cd / A) Power efficiency (Im / W) external quantum efficiency (%) Light-emitting reference element 15 4,8 2,6 (0,66, 0,34) 933 36 24 27 Light-emitting element 16 4,8 2,4 (0,66, 0,34) 853 36 23 27 Light-emitting element 17 4,8 3,1 (0,66, 0,34) 1135 37 24 27 Light-emitting element 18 4,6 2,3 (0,66, 0,34) 937 38 25 28

[0461] As in Fig. 41 and Table 15, the comparative light-emitting element 15 and the light-emitting elements 16 to 18 each exhibited high emission efficiency with an external quantum efficiency of over 25%. The comparative light-emitting element 15 and the light-emitting elements 16 to 18 also exhibited high current efficiency and high energy efficiency, as shown in Fig. 38 and Fig. 40. Furthermore, the efficiency of the light-emitting elements 16 to 18 is equivalent to that of the comparative light-emitting element 15, indicating that the light-emitting element of one embodiment of the present invention can achieve favorable emission efficiency when applied to the inverted stacked element.

[0462] As in Fig. As shown in FIG. 39, the comparative light-emitting element 15 and the light-emitting elements 16 to 18 exhibited favorable current density-voltage characteristics. Furthermore, the comparative light-emitting element 15 and the light-emitting elements 16 to 18 exhibit equivalent current density-voltage characteristics, indicating that the light-emitting element of one embodiment of the present invention can achieve favorable current density-voltage characteristics when applied to the inverted multilayer element.

[0463] As in Fig. As shown in Figure 42, the comparative light-emitting element 15 and the light-emitting elements 16 to 18 each exhibited red emission, the electroluminescence spectrum of which had a peak wavelength at about 619 nm and a half-width of 58 nm. The obtained electroluminescence spectrum revealed that the light was emitted from the guest material Ir(dmdppr-dmp)2(dmp).

[0464] As described above, the light-emitting element of one embodiment of the present invention can also be applied to the inverted multilayer element. The structures shown in this example can be appropriately combined with any of the other embodiments and examples. [Example 6]

[0465] In this example, an example of manufacturing a light-emitting element 19 of an embodiment of the present invention is described. In Fig. Figure 12 shows a schematic cross-sectional view of the light-emitting element fabricated in this example. Details of the element structure are shown in Table 16. Note that for the structures and abbreviations of the organic compounds used in this example, reference can be made to Embodiment 1. [Table 16] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting element 19 electrode 102(2) 70 DBT3P-II - 102(1) 25 Ag - Electron injection layer 130 5 NBphen:Ag 1:0,19 Electron transport layer 118(2) 15 NBphen - 118(1) 25 2mDBTBPDBq-II - Light-emitting layer 140(1) 40 2mDBTBPDBq-II:PCBBiF: Ir(dmdpprdmp)2(dpm) 0,75:0,25:0,06 Hole transport layer 112 20 BPAFLP - Hole injection layer 111 65 DBT3P-II: MoO3 1:0,5 electrode 101(2) 110 ITSO - 101(1) 100 APC - <Herstellung des Licht emittierenden Elements 19>

[0466] A method for manufacturing the light-emitting element of this example will be described below.

[0467] As the electrode 101, an alloy of silver, palladium, and copper (Ag-Pd-Cu or APC) was formed to a thickness of 100 nm over the substrate 210, and then ITSO was formed to a thickness of 110 nm. Note that the electrode area of ​​the electrode 101 was set to 4 mm 2 (2 mm × 2 mm) was set.

[0468] Next, DBT3P-II and molybdenum oxide (MoO3) were deposited as the hole injection layer 111 over the electrode 101 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 to a thickness of 65 nm.

[0469] As hole transport layer 112, BPAFLP was then deposited by evaporation to a thickness of 20 nm over the hole injection layer 111.

[0470] As the light-emitting layer 140, 2mDBTBPDBq-II, PCBBiF, and Ir(dmdppr-dmp)2(dpm) were then co-evaporated over the hole-transport layer 112 in a weight ratio of 2mDBTBPDBq-II:PCBBiF:Ir(dmdppr-dmp)2(dpm) = 0.75:0.25:0.06 to a thickness of 40 nm. Note that in the light-emitting layer 140, 2mDBTBPDBq-II and PCBBiF are host materials, and Ir(dmdppr-dmp)2(dpm) is a guest material (a phosphorescent compound).

[0471] Next, 2mDBTBPDBq-II was deposited as the electron transport layer 118(1) by evaporation to a thickness of 25 nm over the light-emitting layer 140.

[0472] Next, NBPhen was deposited as electron transport layer 118(2) by evaporation to a thickness of 15 nm over the electron transport layer 118(1).

[0473] As electron injection layer 130, NBPhen and Ag were then deposited by co-evaporation in a weight ratio of NBPhen:Ag = 1:0.19 in a thickness of 5 nm over the electron transport layer 118(2).

[0474] As electrode 102, Ag was then deposited by evaporation to a thickness of 25 nm over the electron injection layer 130; subsequently, DBT3P-II was deposited by evaporation to a thickness of 70 nm.

[0475] Subsequently, a heat treatment was performed for one hour at 80 °C in air without sealing. Through the above steps, comparative light-emitting element 19 was obtained. <Eigenschaften des Licht emittierenden Elements>

[0476] Subsequently, the element properties of the fabricated light-emitting element 19 were measured. The measurement was carried out in a similar manner to Example 1.

[0477] Fig. 46 shows the current efficiency-luminance characteristics of the fabricated light-emitting element 19, and Fig. 47 shows the current-voltage characteristics of it. Fig. Figure 48 shows the electroluminescence spectrum of the light-emitting element 19 through which a current at a current density of 2.5 mA / cm 2 flows. It should be noted that the measurement was carried out at room temperature.

[0478] Table 17 shows the element properties of the light-emitting element 19 at about 1000 cd / m 2 . [Table 17] Voltage (V) Current density (mA / cm 2 ) CIE chromaticity (x, y) Luminance (cd / m 2 ) Power efficiency (cd / A) Light-emitting element 19 3,0 1,0 (0,67, 0,33) 998 96

[0479] As in Fig. As shown in Figure 48, the light-emitting element 19 exhibited red emission, whose electroluminescence spectrum had a peak wavelength at 616 nm and a half-width of 24 nm. The obtained electroluminescence spectrum revealed that the light was emitted from the guest material Ir(dmdppr-dmp)2(dmp).

[0480] As in Fig. 46 and Table 17, the light-emitting element 19 showed a favorable current efficiency of over 96 cd / A while emitting deep red.

[0481] As in Fig. As shown in Figure 47, the light-emitting element 19 exhibited favorable current-voltage characteristics, indicating that the composite material of NBPhen and Ag exhibits favorable electron injection characteristics. Therefore, the light-emitting element using the same metal for the electron injection layer 130 and the electrode 102 as the cathode exhibits advantageous characteristics.

[0482] The structures shown in this example may be appropriately combined with any of the other embodiments and examples. [Example 7]

[0483] To evaluate crosstalk, a passive matrix array with a pixel density of 326 ppi was fabricated in this example. The array consists of R, G, and B pixels arranged in a stripe. The pixel size is 78 µm × 78 µm. The size of a subpixel (each R, G, and B pixel) is 26 µm × 78 µm. The aperture ratio is 65.7%.

[0484] Examples of manufacturing a light-emitting element 20 of an embodiment of the present invention and a comparative light-emitting element 21 will be described. In Fig. Figure 51 shows a schematic cross-sectional view of the light-emitting elements fabricated in this example. Tables 18 and 19 show details of the element structures. Fig. 51, a region 2622R, a region 2622G, and a region 2622B each represent a red pixel, a green pixel, and a blue pixel. The light-emitting element manufactured in this example includes a plurality of red (R) pixels, a plurality of green (G) pixels, and a plurality of blue (B) pixels. In the light-emitting element manufactured in this example, the plurality of pixels are arranged in the order of R, G, and B pixels. The structures and abbreviations of the compounds used in this example are shown below. Note that for the structures and abbreviations of the other compounds, reference can be made to the above embodiments and examples. [Table 18] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting element 20 electrode 2641(2) 70 DBT3P-II - 2641(1) 20 Ag - Electron injection layer 2639 0.2 Li2O - Electron transport layer 2638(2) 15 NBPhen - 2638(1) 15 2mDBTBPDBq-II - Light-emitting layer 2646(2) 20 2mDBTBPDBq-II : PCBBiF : Ir(dmdppr-dmp)2(dpm) 0,8:0,2:0,06 2646(1) 20 2mDBTBPDBq-ll : PCBBiF : Ir(tBuppm)2 (acac) 0,7:0,3:0,06 Hole transport layer 2637 20 BPAFLP - Charge generation layer 2635 13 DBT3P-II : MoO3 1:0,5 Electron injection layer 2634 5 NBPhen:Ag 1:0,19 Electron transport layer 2633(2) 10 NBPhen - 2633(1) 5 cqDBCzPA - Light-emitting layer 2644 30 cqDBCzPA : 1.6mMemFLPAPm 1:0,03 Hole transport layer 2632 20 PCPPn - Hole injection layer 2631 13 DBT3P-II : MoO3 1:0,5 electrode see Table 19 Light-emitting reference element 21 electrode 2641(2) 70 DBT3P-II 2641(1) 20 Aq - Electron injection layer 2639 0,2 Li2O - Electron transport layer 2638(2) 20 NBPhen - 2638(1) 15 2mDBTBPDBq-II - Light-emitting layer 2646(2) 20 2mDBTBPDBq-ll : PCBBiF : Ir(dmdppr-dmp)2(dpm) 0,8:0,2:0,06 2646(1) 20 2mDBTBPDBq-ll : PCBBiF : Ir(tBuppm)2 (acac) 0,7:0,3:0,06 Hole transport layer 2637 20 BPAFLP - Charge generation layer 2635 13 DBT3P-II : MoO3 1:0,5 Electron injection layer 2634(2) 1 CuPc - 2634(1) 0,2 Li2O - Electron transport layer 2633(1) 15 NBPhen - 2644 5 cgDBCzPA - Light-emitting layer 2632 30 cgDBCzPA : 1.6mMemFLPAPm 1:0,03 Hole transport layer 2631 20 PCPPn - Hole injection layer 631 13 DBT3P-II : MoO3 1:0,5 electrode see Table 19 [Table 19] pixel Reference symbol Thickness (nm) material R-Pixel 2664c 80 ITSO 2664b 6 Ti 2664a 200 Al-Ni-La G-Pixel 2663c 40 ITSO 2663b 6 Ti 2663a 200 Al-Ni-La B-pixel 2661b 6 Ti 2661a 200 Al-Ni-La <Herstellung des Licht emittierenden Elements>

[0485] A method for manufacturing the light-emitting element of this example is described below. The light-emitting element 20 is a light-emitting element of one embodiment of the present invention, which uses a composite film of a transition metal and an organic compound having an unshared electron pair for an electron-injection layer between two emission units. The comparative light-emitting element 21 uses lithium oxide (Li2O), a Li compound typically used for the electron-injection layer. <<Herstellung des Licht emittierenden Elements 20> >

[0486] As electrodes 2661, 2663, and 2664, an aluminum (Al), nickel (Ni), and lanthanum (La) alloy film was formed over a substrate 2650 to a thickness of 200 nm. A titanium (Ti) film was then formed to a thickness of 6 nm, and heat-treated at 300°C for one hour. Next, an ITSO film was formed to a thickness of 80 nm in the R pixel and 40 nm in the G pixel.

[0487] Next, DBT3P-II and molybdenum oxide (MoO3) were deposited as hole injection layer 2631 over the electrodes 2661, 2663 and 2664 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 to a thickness of 13 nm.

[0488] PCPPn was then deposited as hole transport layer 2632 by evaporation to a thickness of 20 nm over the hole injection layer 2631.

[0489] As the light-emitting layer 2644, cgDBCzPA and 1.6mMemFLPAPrn were then co-evaporated over the hole-transport layer 2632 in a weight ratio of cgDBCzPA:1.6mMemFLPAPrn = 1:0.03 to a thickness of 30 nm. Note that in the light-emitting layer 2644, cgDBCzPA is a host material, and 1.6mMemFLPAPrn is a guest material (a fluorescent compound).

[0490] Next, cgDBCzPA was deposited as the electron transport layer 2633(1) by evaporation to a thickness of 5 nm over the light-emitting layer 2644.

[0491] Next, NBPhen was deposited as electron transport layer 2633(2) by evaporation to a thickness of 10 nm over the electron transport layer 2633(1).

[0492] As electron injection layer 2634, NBPhen and Ag were deposited by co-evaporation in a weight ratio of NBPhen:Ag = 1:0.19 in a thickness of 5 nm over the electron transport layer 2633(2).

[0493] Next, as the charge generation layer 2635, DBT3P-II and MoO3 were deposited over the electron injection layer 2634 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 to a thickness of 13 nm.

[0494] As hole transport layer 2637, BPAFLP was then deposited by evaporation to a thickness of 20 nm over the charge generation layer 2635.

[0495] As the light-emitting layer 2646, 2mDBTBPDBq-II, PCBBiF, and Ir(tBuppm)2(acac) were then co-evaporated over the hole-transport layer 2637 in a weight ratio of 2mDBTBPDBq-II: PCBBiF: Ir(tBuppm)2(acac) = 0.7:0.3:0.06 to a thickness of 20 nm. Subsequently, 2mDBTBPDBq-II, PCBBiF, and Ir(dmdppr-dmp)2(dpm) were co-evaporated to a thickness of 20 nm in a weight ratio of 2mDBTBPDBq-II: PCBBiF: Ir(dmdppr-dmp)2(dpm) = 0.8:0.2:0.06. It should be noted that in the light-emitting layer 2646, 2mDBTBPDBq-II and PCBBiF are host materials and Ir(dmdppr-dmp)2(dpm) and Ir(tBuppm)2(acac) are guest materials (phosphorescent compounds).

[0496] Next, 2mDBTBPDBq-II was deposited as the electron transport layer 2638(1) by evaporation to a thickness of 15 nm over the light-emitting layer 2646.

[0497] Next, NBPhen was deposited as electron transport layer 2638(2) by evaporation to a thickness of 15 nm over the electron transport layer 2638(1).

[0498] As electron injection layer 2639, Li2O was deposited by evaporation to a thickness of 0.2 nm over the electron transport layer 2638(2).

[0499] Ag was then deposited over the electron injection layer 2639 by evaporation to a thickness of 20 nm as electrode 2662. Subsequently, DBT3P-II was deposited by evaporation to a thickness of 70 nm.

[0500] Next, the light-emitting element 20 was sealed in a glove box having a nitrogen atmosphere by attaching a substrate 2652 to the substrate 2650 over which the organic compound was deposited, using a sealant for an organic EL device. Specifically, the sealant was applied to the periphery of the substrate 2652, and the substrate 2652 was attached to the substrate 2650 over which the organic compound was deposited; then, irradiation with UV light having a wavelength of 365 nm at 6 J / cm 2 and a heat treatment at 80 °C for one hour. Through the above steps, the light-emitting element 20 was obtained. <<Herstellung des Licht emittierenden Vergleichselements 21> >

[0501] The comparative light-emitting element 21 was manufactured through the same steps as those of the light-emitting element 20, except for the steps of forming the electron transport layer 2633(2) and the electron injection layer 2634.

[0502] NBPhen was deposited by evaporation to a thickness of 15 nm as the electron-transport layer 2633(2) of the comparative light-emitting element 21. Subsequently, Li2O was deposited by evaporation to a thickness of 0.2 nm as the electron-injection layer 2634, followed by the deposition of CuPc by evaporation to a thickness of 1 nm. <Beobachtung des Nebensprechens jedes Licht emittierenden Elements>

[0503] The crosstalk of the light-emitting element 20 and the comparison light-emitting element 21 was evaluated. The results are shown in Fig. 52A and Fig. 52B shown. Fig. 52A is an enlarged photograph of pixels of the light-emitting element 20 in which blue pixels emit light, and Fig. Figure 52B is an enlarged photograph of pixels of the comparative light-emitting element 21 in which blue pixels emit light. In Fig. 52A and Fig. 52B, a current flows in blue pixels indicated by arrows and in blue pixels to the left of the blue pixels indicated by arrows, while no current flows in red pixels, green pixels, and blue pixels to the right of the blue pixels indicated by the arrows.

[0504] Fig. 52A and Fig. 52B show that in the comparative light-emitting element 21, light is emitted not only from the current-supplied blue pixels but also from the green and red pixels adjacent to these blue pixels, while in the light-emitting element 20, the light emitted from the green and red pixels adjacent to the blue pixels is reduced compared to the comparative light-emitting element 21. In the comparative light-emitting element 21, Li2O, an alkali metal compound, is used for the electron-transport layer adjacent to the charge generation layer, so Li easily diffuses into the electron-transport layer, and a current supplied to the blue pixels to emit light flows through the electron-transport layer into the green and red pixels adjacent to the blue pixels, resulting in crosstalk.In contrast, the light-emitting element 20 of one embodiment of the present invention uses a transition metal for the electron transport layer, so that the diffusion of the metal is not easily caused and the crosstalk can be reduced.

[0505] Next, the intensity of light emitted due to crosstalk from pixels adjacent to the blue-emitting pixels was estimated with respect to the distance from the blue pixels. The results are presented in Fig. 53 shown. In Fig. 53, the longitudinal axis represents the brightness of the red light, which is determined from the Fig. 52A and Fig. 52B, and the cross axis represents the distance from the points indicated by the arrows in Fig. 52A and Fig. 52B to the red pixels to the right of these blue pixels, which consists of the Fig. 52A and Fig. 52B. The longitudinal and transverse axes each represent an arbitrary unit. Fig. 53 shows that the emission intensity of the light-emitting element 20 is lower than that of the comparison light-emitting element 21. In other words, the crosstalk covers a smaller distance in the light-emitting element 20 than in the comparison light-emitting element 21.

[0506] Based on this, it was found that the light-emitting element of one embodiment of the present invention effectively reduces crosstalk. [Example 8]

[0507] Examples of manufacturing a light-emitting element 22 of an embodiment of the present invention and a comparative light-emitting element 23 will be described. In Fig. Figure 54 shows a schematic cross-sectional view of the light-emitting elements prepared in this example. Details of the element structures are shown in Table 20. For the structures and abbreviations of the organic compounds used in this example, reference can be made to the above examples and Embodiment 1. <Herstellung der Licht emittierenden Elemente>

[0508] A method for manufacturing the light-emitting elements of this example is described below. The light-emitting element 22 is a light-emitting element of one embodiment of the present invention, which uses a composite film of a transition metal and an organic compound having an unshared electron pair for an electron-injection layer between two emission units. The comparative light-emitting element 23 uses Li2O, a Li compound typically used for the electron-injection layer. [Table 20] layer Reference symbol Thickness (nm) material Weight ratio Light-emitting element 22 electrode 3641 200 Al - Electron injection layer 3639 5 NBPhen:Ap 1:0,19 Electron transport layer 3638(2) 10 NBPhen - 3638(1) 15 2mDBTBPDBq-II - Light-emitting layer 3646(2) 20 2mDBTBPDBq-II : PCBBiF : Ir(dmdppr-dmp)2(dpm) 0,8:0,2:0,06 3646(1) 20 2mDBTBPDBq-II : PCBBiF : Ir(tBuppm)2(acac) 0,7:0,3:0,06 Hole transport layer 3637 20 BPAFLP - Charge generation layer 3635 30 DBT3P-II : MoO3 1:0,5 Electron injection layer 3634 5 NBPhen:Ag 1:0,19 Electron transport layer 3633(2) 10 NBPhen - 3633(1) 5 cgDBCzPA - Light-emitting layer 3644 25 cgDBCzPA : 1.6mMemFLPAPm 1:0,03 Hole transport layer 3632 10 PCPPn - Hole injection layer 3631 10 DBT3P-II : MoO3 1:0,5 electrode 3642 70 ITSO - Light-emitting reference element 23 electrode 3641 200 Al - Electron injection layer 3639 1 LiF 1:0,19 Electron transport layer 3638(2) 15 NBPhen - 3638(1) 15 2mDBTBPDBq-II - Light-emitting layer 3646(2) 20 2mDBTBPDBq-II : PCBBiF : Ir(dmdppr-dmp)2(dpm) 0,8:0,2:0,06 3646(1) 20 2mDBTBPDBq-II : PCBBiF : Ir(tBuppm)2(acac) 0,7:0,3:0,06 Hole transport layer 3637 20 BPAFLP - Charge generation layer 3635(2) 30 DBT3P-II : MoO3 1:0,5 3635(1) 1 CuPc - Electron injection layer 3634(1) 0.2 Li2O - Electron transport layer 3633(2) 15 NBPhen - 3633(1) 5 caDBCzPA - Light-emitting layer 3644 25 cgDBCzPA : 1.6mMemFLPAPm 1:0,03 Hole transport layer 3632 10 PCPPn - Hole injection layer 3631 10 DBT3P-II : MoO3 1:0,5 electrode 3642 70 ITSO - <<Herstellung des Licht emittierenden Elements 22> >

[0509] As electrode 3642, an ITSO film with a thickness of 70 nm was formed over a substrate 3650. The electrode area was set to 4 mm 2 (2 mm × 2 mm).

[0510] Next, DBT3P-II and MoO3 were deposited as hole injection layer 3631 over the electrode 3642 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 to a thickness of 10 nm.

[0511] As hole transport layer 3632, PCPPn was then deposited by evaporation to a thickness of 10 nm over the hole injection layer 3631.

[0512] As the light-emitting layer 3644, cgDBCzPA and 1.6mMemFLPAPrn were then co-evaporated over the hole-transport layer 3632 in a weight ratio of cgDBCzPA:1.6mMemFLPAPrn = 1:0.03 to a thickness of 25 nm. Note that in the light-emitting layer 3644, cgDBCzPA is a host material, and 1.6mMemFLPAPrn is a guest material (a fluorescent compound).

[0513] Next, cgDBCzPA was deposited as the electron transport layer 3633(1) by evaporation to a thickness of 5 nm over the light-emitting layer 3644.

[0514] Next, NBPhen was deposited as electron transport layer 3633(2) by evaporation to a thickness of 10 nm over the electron transport layer 3633(1).

[0515] As electron injection layer 3634, NBPhen and Ag were deposited by co-evaporation in a weight ratio of NBPhen:Ag = 1:0.19 in a thickness of 5 nm over the electron transport layer 3633(2).

[0516] Next, as the charge generation layer 3635, DBT3P-II and MoO3 were deposited over the electron injection layer 3634 by co-evaporation in a weight ratio of DBT3P-II:MoO3 = 1:0.5 to a thickness of 30 nm.

[0517] As hole transport layer 3637, BPAFLP was then deposited by evaporation to a thickness of 20 nm over the charge generation layer 3635.

[0518] As the light-emitting layer 3646, 2mDBTBPDBq-II, PCBBiF, and Ir(tBuppm)2(acac) were then co-evaporated over the hole-transport layer 3637 in a weight ratio of 2mDBTBPDBq-II: PCBBiF: Ir(tBuppm)2(acac) = 0.7:0.3:0.06 to a thickness of 20 nm. Subsequently, 2mDBTBPDBq-II, PCBBiF, and Ir(dmdppr-dmp)2(dpm) were co-evaporated to a thickness of 20 nm in a weight ratio of 2mDBTBPDBq-II: PCBBiF: Ir(dmdppr-dmp)2(dpm) = 0.8:0.2:0.06. It should be noted that in the light-emitting layer 3646, 2mDBTBPDBq-II and PCBBiF are host materials and Ir(dmdppr-dmp)2(dpm) and Ir(tBuppm)2(acac) are guest materials (phosphorescent compounds).

[0519] Next, 2mDBTBPDBq-II was deposited as the electron transport layer 3638(1) by evaporation to a thickness of 15 nm over the light-emitting layer 3646.

[0520] Next, NBPhen was deposited as electron transport layer 3638(2) by evaporation to a thickness of 10 nm over the electron transport layer 3638(1).

[0521] As electron injection layer 3639, NBPhen and Ag were deposited by co-evaporation in a weight ratio of NBPhen:Ag = 1:0.19 in a thickness of 5 nm over the electron transport layer 3638(2).

[0522] As electrode 3641, Al was then deposited over the electron injection layer 3639 by evaporation to a thickness of 200 nm.

[0523] Next, the light-emitting element 22 was sealed in a glove box having a nitrogen atmosphere by attaching a substrate 3652 to the substrate 3650 over which the organic compound film was deposited, using a sealant for an organic EL device. Specifically, the sealant was applied to the periphery of the substrate 3652, and the substrate 3652 was attached to the substrate 3650 over which the organic compound film was deposited; then, irradiation with UV light having a wavelength of 365 nm at 6 J / cm 2 and a heat treatment at 80 °C for one hour. Through the above steps, the light-emitting element 22 was obtained. <<Herstellung des Licht emittierenden Vergleichselements 23> >

[0524] The comparative light-emitting element 23 was manufactured through the same steps as those of the light-emitting element 22, except for the steps of forming the electron transport layer 3633(2), the electron injection layer 3634, the electron transport layer 3638(2), and the electron injection layer 3639.

[0525] As the electron transport layer 3633(2) of the comparative light-emitting element 23, NBPhen was deposited by evaporation to a thickness of 15 nm over the electron transport layer 3633(1).

[0526] As the electron injection layer 3634, Li2O was deposited by evaporation to a thickness of 0.2 nm over the electron transport layer 3633(2), followed by the deposition of CuPc by evaporation to a thickness of 1 nm.

[0527] As electron transport layer 3638(2), NBPhen was deposited by evaporation to a thickness of 15 nm over the electron transport layer 3638(1).

[0528] As electron injection layer 3639, LiF was deposited by evaporation to a thickness of 1 nm over the electron transport layer 3638(2). <<Messung der Licht emittierenden Elemente> >

[0529] The elemental properties of the fabricated light-emitting element 22 and the fabricated comparison light-emitting element 23 were measured. The luminance and CIE chromaticity were measured using a luminance colorimeter (BM-5A, manufactured by TOPCON TECHNOHOUSE CORPORATION), and the electroluminescence spectra were measured using a multi-channel spectrometer (PMA-11, manufactured by Hamamatsu Photonics KK).

[0530] Fig. 55 shows the current efficiency-luminance characteristics of the fabricated light-emitting element 22 and the fabricated comparative light-emitting element 23; Fig. 56 shows the current density-voltage characteristics thereof; Fig. 57 shows the energy efficiency-luminance characteristics thereof; and Fig. Figure 58 shows the external quantum efficiency-luminance characteristics of these. Note that the measurements of the light-emitting elements were performed at room temperature (in an atmosphere maintained at 23 °C). Fig. Figure 59 shows the electroluminescence spectra of the light-emitting elements through which a current at a current density of 2.5 mA / cm 2 flows. It should be noted that the measurement was carried out at room temperature.

[0531] Table 21 shows the element properties of the light-emitting element 22 and the comparativ...

Claims

[1] Light-emitting element comprising: a light-emitting layer between an anode and a cathode; and a first layer between the light-emitting layer and the cathode, wherein the first layer is an electron injection layer, wherein the first layer includes a first organic compound and a transition metal, wherein the first organic compound contains an unshared electron pair, and where the first organic compound and the transition metal form a SOMO (single occupied molecular orbital). [2] Light-emitting element comprising: a first light-emitting unit and a second light-emitting unit between an anode and a cathode; and a first layer between the first light-emitting unit and the second light-emitting unit, wherein the first layer comprises a first organic compound and a transition metal, wherein the first organic compound contains an unshared electron pair, wherein the transition metal is a metal of Group 5, Group 7, Group 9 or Group 11 of the Periodic Table, and where the first organic compound and the transition metal form a SOMO. [3] Light-emitting element comprising: a first light-emitting unit and a second light-emitting unit between an anode and a cathode; and a first layer and a charge generation layer between the first light-emitting unit and the second light-emitting unit, wherein the first layer and the charge generation layer are in contact with each other, wherein the first layer comprises a first organic compound and a transition metal, wherein the first organic compound contains an unshared electron pair, wherein the transition metal is a metal of Group 5, Group 7, Group 9 or Group 11 of the Periodic Table, and where the first organic compound and the transition metal form a SOMO. [4] Light-emitting element comprising: a light-emitting layer between an anode and a cathode; and a first layer between the light-emitting layer and the cathode, wherein the first layer comprises a first organic compound and a transition metal, wherein the first organic compound contains an unshared electron pair, and wherein the spin density of a film comprising the first organic compound and the transition metal in a molar ratio of 1:1 is higher than or equal to 1 × 10 16 Spins / cm 3 is. [5] Light-emitting element comprising: a first light-emitting unit and a second light-emitting unit between an anode and a cathode; and a first layer between the first light-emitting unit and the second light-emitting unit, wherein the first layer comprises a first organic compound and a transition metal, wherein the first organic compound contains an unshared electron pair, and wherein the spin density of a film comprising the first organic compound and the transition metal in a molar ratio of 1:1 is higher than or equal to 1 × 10 16 Spins / cm 3 and less than or equal to 5 × 10 17 Spins / cm 3 is. [6] The light-emitting element according to any one of claims 1, 4 and 5, wherein the transition metal is a metal belonging to Group 5, Group 7, Group 9 or Group 11 of the Periodic Table. [7] The light-emitting element according to any one of claims 1 to 5, wherein the transition metal is a metal belonging to Group 11 of the Periodic Table. [8] A light-emitting element according to any one of claims 1 to 5, wherein the transition metal is Ag. [9] The light-emitting element according to any one of claims 1 to 5, wherein the first organic compound includes an electron-deficient heteroaromatic ring. [10] The light-emitting element according to claim 9, wherein the electron-deficient heteroaromatic ring includes at least one of a pyridine ring, a diazine ring, and a triazine ring. [11] The light-emitting element according to any one of claims 1 to 5, wherein the first organic compound has 25 to 100 carbon atoms. [12] The light-emitting element according to any one of claims 1 to 5, wherein the first organic compound does not include a 1,10-phenanthroline skeleton. [13] The light-emitting element according to any one of claims 1 to 5, wherein a LUMO level of the first organic compound is higher than or equal to -3.6 eV and lower than or equal to -2.3 eV. [14] The light-emitting element according to any one of claims 1 to 3, further comprising a second layer between the cathode and the first layer, wherein the second layer includes a second organic compound including an electron-deficient heteroaromatic ring. [15] The light-emitting element according to claim 14, wherein a LUMO level of the second organic compound is lower than an energy level of the SOMO. [16] A light-emitting element according to any one of claims 1 to 5, wherein an alkali metal and an alkaline earth metal are not contained. [17] The light-emitting element according to any one of claims 1 to 5, wherein a molar ratio of the transition metal to the first organic compound in the first layer is higher than or equal to 0.2 and lower than or equal to 0.

8. [18] The light-emitting element according to any one of claims 1 to 5, wherein the cathode includes a metal which is the same as the transition metal. [19] Display device comprising: the light-emitting element according to any one of claims 1 to 5; and at least one of a color filter and a transistor. [20] Electronic device comprising: the display device of claim 19; and at least one of a housing and a touch sensor. [21] Lighting device comprising: the light-emitting element according to any one of claims 1 to 5; and at least one of a housing and a touch sensor.

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