Light-emitting device, electronic device and lighting device

Abstract

Light-emitting device comprising: an anode; a cathode; and an EL layer between the anode and the cathode, wherein the EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer and a fourth layer in that order from an anode side, where the first layer is in contact with the anode, where the fourth layer is in contact with the light-emitting layer, wherein the first layer contains a first organic compound and a second organic compound, the second layer contains a third organic compound, the third layer contains a fourth organic compound, wherein the light-emitting layer includes a fifth organic compound and a sixth organic compound, the fourth layer contains a seventh organic compound and an eighth substance, wherein the first organic compound has an electron-accepting property with respect to the second organic compound, where the fifth organic compound is an emission center substance, where the HOMO level of the second organic compound is higher than or equal to -5.7 eV and lower than or equal to -5.4 eV, and the eighth substance is an organic complex.

Description

Technical field

[0001] Embodiments of the present invention relate to a light-emitting device, an electronic device, and a lighting device. It should be noted that an embodiment of the present invention is not limited to the aforementioned technical field. The technical field of an embodiment of the invention disclosed in this description and the like relates to an object, a method, or a manufacturing process. An embodiment of the present invention relates to a process, a machine, a product, or a composition.Specific examples for the technical field of an embodiment of the present invention disclosed in this description include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, an energy storage device, a storage device, an imaging device, an operating method therefor, and a manufacturing method therefor. State of the art

[0002] Light-emitting devices (organic EL devices) comprising organic compounds and utilizing electroluminescence (EL) are increasingly used in practice. In the basic structure of such light-emitting devices, an organic compound layer containing a light-emitting material (an EL layer) is positioned between a pair of electrodes. Charge carriers are injected by applying a voltage to the element, and the recombination energy of the charge carriers is utilized, thereby generating light emission from the light-emitting material.

[0003] Since such light-emitting devices are self-illuminating, when used as pixels in a display, they offer advantages over liquid crystals in that pixel visibility is high and backlighting is not required. Displays incorporating such light-emitting devices are also highly advantageous in that they can be thin and lightweight. Furthermore, these devices also exhibit a very fast response time.

[0004] Since the light-emitting layers of such light-emitting devices can be successively formed in two dimensions, planar light emission can be achieved. This feature is difficult to realize with point light sources, such as incandescent lamps and LEDs, or linear light sources, such as fluorescent lamps. Therefore, light-emitting devices also have great potential as planar light sources that can be applied to lighting devices and the like.

[0005] Displays or lighting devices comprising light-emitting devices can, as described above, be appropriately used for a variety of electronic devices, and research and development of light-emitting devices has progressed with a view to higher efficiency or longer lifespan.

[0006] In a structure disclosed in patent document 1, a hole transport material, the HOMO level of which lies between the HOMO level of a first hole injection layer and the HOMO level of a host material, is provided between a light-emitting layer and a first hole transport layer in contact with the hole injection layer.

[0007] Although the properties of light-emitting devices have improved remarkably, the increased demands regarding various properties, including efficiency and durability, have not yet been met. [Reference][Patent documents] [Patent Document 1] WO 2011 / 065 136 A1 [Patent document 2] US 2015 / 0 243 892 A1 [Patent document 3] US 2017 / 0 222 155 A1 [Patent Document 4] WO 2017 / 109 722 A1 [Patent document 5] US 2012 / 0 080 667 A1 [Patent document 6] US 2017 / 0 222 156 A1 Disclosure of the invention

[0008] One object of an embodiment of the present invention is to provide a novel light-emitting device. Another object of an embodiment of the present invention is to provide a light-emitting device with high emission efficiency. Another object of an embodiment of the present invention is to provide a light-emitting device with a long lifetime. Another object of an embodiment of the present invention is to provide a light-emitting device with a low operating voltage.

[0009] A further object of an embodiment of the present invention is to provide a light-emitting device, an electronic device, and a display device, each exhibiting high reliability. A further object of an embodiment of the present invention is to provide a light-emitting device, an electronic device, and a display device, each exhibiting low power consumption.

[0010] The present invention requires only that at least one of the above-described problems be fulfilled.

[0011] One embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a light-emitting layer. A decay curve, showing the change in luminance of a light emission obtained when a constant current is supplied to the light-emitting device, exhibits a local maximum value.

[0012] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order from the anode side. The first layer is in contact with the anode. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound. The first organic compound exhibits electron-accepting properties with respect to the second organic compound.The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is higher than or equal to -5.7 eV and lower than or equal to -5.4 eV. The electron mobility of the seventh organic compound is higher than or equal to 1 × 10⁻⁶. -7 cm 2 / Vs and less than or equal to 5 × 10 -5 cm 2 / Vs, when the square root of the electric field strength [V / cm] is 600. A decay curve showing a change in the luminance of a light emission obtained when a constant current is supplied to the light-emitting device has a local maximum value.

[0013] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order from the anode side. The first layer is in contact with the anode. The fourth layer is in contact with the light-emitting layer. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound.The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is higher than or equal to -5.7 eV and lower than or equal to -5.4 eV. The electron mobility of the seventh organic compound is higher than or equal to 1 × 10⁻⁶. -7 cm 2 / Vs and less than or equal to 5 × 10 -5 cm 2 / Vs when the square root of the electric field strength [V / cm] is 600. The HOMO level of the seventh organic compound is higher than or equal to -6.0 eV. A decay curve showing a change in the luminance of a light emission obtained when a constant current is supplied to the light-emitting device exhibits a local maximum value.

[0014] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order from the anode side. The first layer is in contact with the anode. The fourth layer is in contact with the light-emitting layer. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound.The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is greater than or equal to -5.7 eV and less than or equal to -5.4 eV. The difference between the HOMO level of the third organic compound and the HOMO level of the second organic compound is less than or equal to 0.2 eV. The HOMO level of the third organic compound is equal to or lower than the HOMO level of the second organic compound. The electron mobility of the seventh organic compound is greater than or equal to 1 × 10⁻⁶ eV. -7 cm 2 / Vs and less than or equal to 5 × 10 -5 cm 2 / Vs when the square root of the electric field strength [V / cm] is 600. The HOMO level of the seventh organic compound is higher than or equal to -6.0 eV. A decay curve showing a change in the luminance of a light emission obtained when a constant current is supplied to the light-emitting device exhibits a local maximum value.

[0015] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order from the anode side. The first layer is in contact with the anode. The fourth layer is in contact with the light-emitting layer. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound.The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The second organic compound possesses a first hole-transport framework. The third organic compound possesses a second hole-transport framework. The fourth organic compound possesses a third hole-transport framework. The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is greater than or equal to -5.7 eV and less than or equal to -5.4 eV. The first hole-transport framework, the second hole-transport framework, and the third hole-transport framework are each independently a carbazole framework, a dibenzofuran framework, a dibenzothiophene framework, or anthracene framework, respectively. The electron mobility of the seventh organic compound is greater than or equal to 1 × 10⁻⁶. -7 cm 2 / Vs and less than or equal to 5 × 10 -5 cm 2 / Vs when the square root of the electric field strength [V / cm] is 600. The HOMO level of the seventh organic compound is higher than or equal to -6.0 eV. A decay curve showing a change in the luminance of a light emission obtained when a constant current is supplied to the light-emitting device exhibits a local maximum value.

[0016] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order, starting from the anode side. The first layer is in contact with the anode. The fourth layer is in contact with the light-emitting layer. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound and an eighth substance.The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is higher than or equal to -5.7 eV and lower than or equal to -5.4 eV. The seventh organic compound is an organic compound possessing an anthracene framework. The eighth substance is an organic complex of an alkali metal or an alkaline earth metal. A decay curve, showing the change in luminance of a light emission obtained when a constant current is applied to the light-emitting device, exhibits a local maximum value.

[0017] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order, starting from the anode side. The first layer is in contact with the anode. The fourth layer is in contact with the light-emitting layer. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound and an eighth substance.The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is greater than or equal to -5.7 eV and less than or equal to -5.4 eV. The difference between the HOMO level of the third organic compound and the HOMO level of the second organic compound is less than or equal to 0.2 eV. The HOMO level of the third organic compound is equal to or lower than the HOMO level of the second organic compound. The seventh organic compound is an organic compound possessing an anthracene framework. The eighth substance is an organic complex of an alkali metal or an alkaline earth metal.A decay curve showing a change in the luminance of a light emission obtained when a constant current is supplied to the light-emitting device has a local maximum value.

[0018] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order, starting from the anode side. The first layer is in contact with the anode. The fourth layer is in contact with the light-emitting layer. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound and an eighth substance.The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The second organic compound possesses a first hole-transport framework. The third organic compound possesses a second hole-transport framework. The fourth organic compound possesses a third hole-transport framework. The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is higher than or equal to -5.7 eV and lower than or equal to -5.4 eV. The first hole-transport framework, the second hole-transport framework, and the third hole-transport framework are each independently a carbazole framework, a dibenzofuran framework, a dibenzothiophene framework, or an anthracene framework, respectively. The seventh organic compound is an organic compound possessing an anthracene framework. The eighth substance is an organic complex of an alkali metal or an alkaline earth metal.A decay curve showing a change in the luminance of a light emission obtained when a constant current is supplied to the light-emitting device has a local maximum value.

[0019] Another embodiment of the present invention is a light-emitting device with the above structure, wherein the decay curve has a section in which the luminance exceeds 100%.

[0020] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order from the anode side. The first layer is in contact with the anode. The fourth layer is in contact with the light-emitting layer. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound.The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is higher than or equal to -5.7 eV and lower than or equal to -5.4 eV. The electron mobility of the seventh organic compound is higher than or equal to 1 × 10⁻⁶. -7 cm 2 / Vs and less than or equal to 5 × 10 -5 cm 2 / Vs, if the square root of the electric field strength [V / cm] is 600. The HOMO level of the seventh organic compound is higher than or equal to -6.0 eV.

[0021] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order from the anode side. The first layer is in contact with the anode. The fourth layer is in contact with the light-emitting layer. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound.The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is greater than or equal to -5.7 eV and less than or equal to -5.4 eV. The difference between the HOMO level of the third organic compound and the HOMO level of the second organic compound is less than or equal to 0.2 eV. The HOMO level of the third organic compound is equal to or lower than the HOMO level of the second organic compound. The electron mobility of the seventh organic compound is greater than or equal to 1 × 10⁻⁶ eV. -7 cm 2 / Vs and less than or equal to 5 × 10 -5 cm 2 / Vs, if the square root of the electric field strength [V / cm] is 600. The HOMO level of the seventh organic compound is higher than or equal to -6.0 eV.

[0022] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order from the anode side. The first layer is in contact with the anode. The fourth layer is in contact with the light-emitting layer. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound.The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The second organic compound possesses a first hole-transport framework. The third organic compound possesses a second hole-transport framework. The fourth organic compound possesses a third hole-transport framework. The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is greater than or equal to -5.7 eV and less than or equal to -5.4 eV. The first hole-transport framework, the second hole-transport framework, and the third hole-transport framework are each independently a carbazole framework, a dibenzofuran framework, a dibenzothiophene framework, or anthracene framework, respectively. The electron mobility of the seventh organic compound is greater than or equal to 1 × 10⁻⁶. -7 cm 2 / Vs and less than or equal to 5 × 10 -5 cm 2 / Vs, if the square root of the electric field strength [V / cm] is 600. The HOMO level of the seventh organic compound is higher than or equal to -6.0 eV.

[0023] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order, starting from the anode side. The first layer is in contact with the anode. The fourth layer is in contact with the light-emitting layer. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound and an eighth substance.The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is higher than or equal to -5.7 eV and lower than or equal to -5.4 eV. The seventh organic compound is an organic compound possessing an anthracene framework. The eighth substance is an organic complex of an alkali metal or an alkaline earth metal.

[0024] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order, starting from the anode side. The first layer is in contact with the anode. The fourth layer is in contact with the light-emitting layer. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound and an eighth substance.The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is greater than or equal to -5.7 eV and less than or equal to -5.4 eV. The difference between the HOMO level of the third organic compound and the HOMO level of the second organic compound is less than or equal to 0.2 eV. The HOMO level of the third organic compound is equal to or lower than the HOMO level of the second organic compound. The seventh organic compound is an organic compound possessing an anthracene framework. The eighth substance is an organic complex of an alkali metal or an alkaline earth metal.

[0025] Another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in that order, starting from the anode side. The first layer is in contact with the anode. The fourth layer is in contact with the light-emitting layer. The first layer comprises a first organic compound and a second organic compound. The second layer comprises a third organic compound. The third layer comprises a fourth organic compound. The light-emitting layer comprises a fifth organic compound and a sixth organic compound. The fourth layer comprises a seventh organic compound and an eighth substance.The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The second organic compound possesses a first hole-transport framework. The third organic compound possesses a second hole-transport framework. The fourth organic compound possesses a third hole-transport framework. The fifth organic compound is an emission center substance. The HOMO level of the second organic compound is higher than or equal to -5.7 eV and lower than or equal to -5.4 eV. The first hole-transport framework, the second hole-transport framework, and the third hole-transport framework are each independently a carbazole framework, a dibenzofuran framework, a dibenzothiophene framework, or an anthracene framework, respectively. The seventh organic compound is an organic compound possessing an anthracene framework. The eighth substance is an organic complex of an alkali metal or an alkaline earth metal.

[0026] Another embodiment of the present invention is a light-emitting device with the above structure, wherein the seventh organic compound comprises an anthracene framework and a heterocyclic framework.

[0027] Another embodiment of the present invention is a light-emitting device with the above structure, wherein the electron mobility of the seventh organic compound is lower than the electron mobility of the sixth organic compound.

[0028] Another embodiment of the present invention is a light-emitting device with the above structure, wherein the difference between the HOMO levels of the third organic compound and the fourth organic compound is less than or equal to 0.2 eV.

[0029] Another embodiment of the present invention is a light-emitting device with the above structure, wherein the HOMO level of the fourth organic compound is lower than the HOMO level of the third organic compound.

[0030] Another embodiment of the present invention is a light-emitting device with the above structure, wherein the second organic compound has a dibenzofuran skeleton.

[0031] Another embodiment of the present invention is a light-emitting device with the above structure, wherein the second organic compound and the third organic compound are the same substance.

[0032] Another embodiment of the present invention is a light-emitting device with the above structure, wherein the fifth organic compound is a blue fluorescent material.

[0033] Another embodiment of the present invention is an electronic device which, in the above structure, includes a sensor, a control button, a loudspeaker or a microphone.

[0034] Another embodiment of the present invention is a light-emitting device which, in the above structure, includes a transistor or a substrate.

[0035] Another embodiment of the present invention is a lighting device which, in the above structure, includes a housing.

[0036] It should be noted that the light-emitting device in this description includes, within its category, an image display device with a light-emitting device. The light-emitting device may be contained in a module in which a light-emitting device is provided with a connector, such as an anisotropic conductive film or a tape carrier package (TCP); in a module in which a printed circuit board is provided at the end of a TCP; or in a module in which an integrated circuit (IC) is directly mounted to a light-emitting device by a chip-on-glass (COG) process. The light-emitting device may be contained within a lighting device or the like.

[0037] One embodiment of the present invention can provide a novel light-emitting device. Another embodiment of the present invention can provide a light-emitting device with a long lifetime. A further embodiment of the present invention can provide a light-emitting device with high emission efficiency.

[0038] Another embodiment of the present invention can provide a light-emitting device, an electronic device, and a display device, each exhibiting high reliability. Another embodiment of the present invention can provide a light-emitting device, an electronic device, and a display device, each exhibiting low power consumption.

[0039] It should be noted that the descriptions of the effects do not preclude the existence of further effects. One embodiment of the present invention does not necessarily achieve all of the effects listed above. Further effects will become apparent from the explanation of the description, the drawings, the claims, and the like, and can be derived from them. Brief description of the drawings

[0040] In the accompanying drawings: Fig. Figures 1A to 1C are schematic representations of light-emitting devices; Fig. 2A and Fig. 2B are illustrations to explain an extension of service life; Fig. 3A and Fig. 3B are illustrations to explain an increase in luminance; Fig. 4A and Fig. Figure 4B are conceptual representations of a light-emitting active matrix device; Fig. 5A and Fig. 5B are conceptual representations of light-emitting active matrix devices; Fig. Figure 6 is a conceptual representation of a light-emitting active matrix device; Fig. 7A and Fig. 7B are conceptual representations of a light-emitting passive matrix device; Fig. 8A and Fig. 8B represents a lighting device; Fig. 9A, Fig. 9B1, Fig. 9B2 and Fig. 9C represent electronic devices; Fig. 10A to 10C represent electronic devices; Fig. 11 represents a lighting device; Fig. 12 represents a lighting device; Fig. 13 represents display devices and lighting devices in a vehicle; Fig. 14A and Fig. 14B represents an electronic device; Fig. 15A to 15C represent an electronic device; Fig. Figure 16 shows the luminance-current density properties of a light-emitting device 1; Fig. Figure 17 shows the power efficiency-luminance characteristics of the light-emitting device 1; Fig. Figure 18 shows the luminance-voltage properties of the light-emitting device 1; Fig. Figure 19 shows the current-voltage characteristics of the light-emitting device 1; Fig. Figure 20 shows the external quantum efficiency luminance properties of the light-emitting device 1; Fig. Figure 21 shows an emission spectrum of the light-emitting device 1; Fig. Figure 22 shows the time dependence of the normalized luminance of the light-emitting device 1; Fig. Figure 23 shows the luminance-current density properties of a light-emitting device 2; Fig. Figure 24 shows the power efficiency-luminance characteristics of the light-emitting device 2; Fig. Figure 25 shows the luminance-voltage characteristics of the light-emitting device 2; Fig. Figure 26 shows the current-voltage characteristics of the light-emitting device 2; Fig. Figure 27 shows the external quantum efficiency luminance properties of the light-emitting device 2; Fig. Figure 28 shows an emission spectrum of the light-emitting device 2; Fig. Figure 29 shows the time dependence of the normalized luminance of the light-emitting device 2; Fig. Figure 30 shows the luminance-current density properties of a light-emitting device 3; Fig. Figure 31 shows the power efficiency-luminance characteristics of the light-emitting device 3; Fig. Figure 32 shows the luminance-voltage properties of the light-emitting device 3; Fig. Figure 33 shows the current-voltage characteristics of the light-emitting device 3; Fig. Figure 34 shows the external quantum efficiency luminance properties of the light-emitting device 3; Fig. Figure 35 shows an emission spectrum of the light-emitting device 3; Fig. Figure 36 shows the time dependence of the normalized luminance of the light-emitting device 3; Fig. Figure 37 represents the structure of an all-electron cell; Fig. Figure 38 shows the current density-voltage properties of an all-electron cell; Fig. Figure 39 shows the calculated frequency characteristics of the capacitance C when a DC voltage is 7.0 V and a ratio of ZADN to Liq is 1:1; Fig. Figure 40 shows the frequency characteristics of -ΔB when the DC voltage is 7.0 V and the ratio of ZADN to Liq is 1:1; Fig. Figure 41 shows the dependence of electron mobility on the electric field strength of organic compounds; Fig. Figure 42 shows the luminance-current density properties of a light-emitting device 4; Fig. Figure 43 shows the power efficiency-luminance characteristics of the light-emitting device 4; Fig. Figure 44 shows the luminance-voltage characteristics of the light-emitting device 4; Fig. Figure 45 shows the current-voltage characteristics of the light-emitting device 4; Fig. Figure 46 shows the external quantum efficiency luminance properties of the light-emitting device 4; Fig. Figure 47 shows an emission spectrum of the light-emitting device 4; Fig. Figure 48 shows the time dependence of the normalized luminance of the light-emitting device 4; Fig. Figure 49 shows the luminance-current density properties of a light-emitting device 5; Fig. Figure 50 shows the power efficiency-luminance characteristics of the light-emitting device 5; Fig. Figure 51 shows the luminance-voltage characteristics of the light-emitting device 5; Fig. Figure 52 shows the current-voltage characteristics of the light-emitting device 5; Fig. Figure 53 shows the external quantum efficiency luminance properties of the light-emitting device 5; Fig. Figure 54 shows an emission spectrum of the light-emitting device 5; Fig. Figure 55 shows the time dependence of the normalized luminance of the light-emitting device 5; Fig. Figure 56 shows the luminance-current density properties of a light-emitting device 6; Fig. Figure 57 shows the power efficiency-luminance characteristics of the light-emitting device 6; Fig. Figure 58 shows the luminance-voltage characteristics of the light-emitting device 6; Fig. Figure 59 shows the current-voltage characteristics of the light-emitting device 6; Fig. Figure 60 shows the external quantum efficiency luminance properties of the light-emitting device 6; Fig. Figure 61 shows an emission spectrum of the light-emitting device 6; Fig. Figure 62 shows the time dependence of the normalized luminance of the light-emitting device 6; Fig. Figure 63 shows the luminance-current density properties of a light-emitting device 7; Fig. Figure 64 shows the power efficiency-luminance characteristics of the light-emitting device 7; Fig. Figure 65 shows the luminance-voltage characteristics of the light-emitting device 7; Fig. Figure 66 shows the current-voltage characteristics of the light-emitting device 7; Fig. Figure 67 shows the external quantum efficiency luminance properties of the light-emitting device 7; Fig. Figure 68 shows an emission spectrum of the light-emitting device 7; Fig. Figure 69 shows the time dependence of the normalized luminance of the light-emitting device 7; Fig. Figure 70 shows the luminance-current density properties of light-emitting devices 8 and 9; Fig. Figure 71 shows the power efficiency-luminance characteristics of the light-emitting devices 8 and 9; Fig. Figure 72 shows the luminance-voltage characteristics of the light-emitting devices 8 and 9; Fig. Figure 73 shows the current-voltage characteristics of the light-emitting devices 8 and 9; Fig. Figure 74 shows the external quantum efficiency luminance properties of the light-emitting devices 8 and 9; Fig. Figure 75 shows the emission spectra of the light-emitting devices 8 and 9; and Fig. Figure 76 shows the time dependence of the normalized luminance of the light-emitting devices 8 and 9. Best way to implement the invention

[0041] Embodiments of the present invention are described in detail below with reference to the drawings. (Version 1)

[0042] Fig. Figure 1A represents a light-emitting device of an embodiment of the present invention. The light-emitting device of an embodiment of the present invention comprises an anode 101, a cathode 102, and an EL layer 103. The EL layer comprises a hole injection layer 111, a hole transport layer 112, a light-emitting layer 113, and an electron transport layer 114.

[0043] Although Fig. Although 1A additionally represents an electron injection layer 115 in the EL layer 103, the structure of the light-emitting device is not limited to this. As long as the components described above are included, a layer with a different function may be included.

[0044] The hole injection layer 111 comprises a first organic compound and a second organic compound. The first organic compound exhibits electron-accepting properties with respect to the second organic compound. The second organic compound has a relatively low HOMO level, higher than or equal to -5.7 eV and lower than or equal to -5.4 eV. The relatively low HOMO level of the second organic compound facilitates the injection of holes into the hole transport layer 112.

[0045] For example, the first organic compound can be one containing an electron-withdrawing group (especially a cyano group or a halogen group, such as a fluorine group). A substance exhibiting electron-accepting properties with respect to the second organic compound is then appropriately selected from among such compounds. Examples of such an organic compound include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ), and 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile. A compound in which electron-withdrawing groups are bonded to a fused aromatic ring with a variety of heteroatoms, such as HAT-CN, is preferred because it is thermally stable.A [3]radialene derivative containing an electron-withdrawing group (especially a cyano group or a halogen group, such as a fluorine group) exhibits very high electron-accepting properties and is therefore preferred. Specific examples include α,α',α''-1,2,3-cyclopropanetriylidentris[4-cyano-2,3,5,6-tetrafluorobenzolacetonitrile], α,α',α''-1,2,3-cyclopropanetriylidentris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzolacetonitrile], and α,α',α''-1,2,3-cyclopropanetriylidentris[2,3,4,5,6-pentafluorobenzolacetonitrile].

[0046] The second organic compound is preferably an organic compound with hole-transporting properties and a carbazole, dibenzofuran, dibenzothiophene, or anthracene framework. In particular, an aromatic amine with a substituent comprising a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine comprising a naphthalene ring, or an aromatic monoamine in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group is preferably used. It should be noted that the second organic compound with an N,N-bis(4-biphenyl)amino group is preferred because it allows for the fabrication of a long-life light-emitting device. Specific examples of the second organic compound include N-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BnfABP), N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), 4,4'-Bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl)-4"-phenyltriphenylamine (abbreviation: BnfBB1BP), N,N-Bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-6-amine (abbreviation: BBABnf(6)), N,N-Bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-Bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-4-amine (abbreviation: BBABnf(II)(4)), N,N-Bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(Dibenzothiophen-4-yl)phenyl]-N-phenyl-4-biphenylamine (abbreviation: ThBA1BP), 4-(2-Naphthyl)-4',4"-diphenyltriphenylamine (abbreviation: BBAßNB), 4-[4-(2-Naphthyl)phenyl]-4',4"-diphenyltriphenylamine (abbreviation: BBAßNBi), 4-(2;1'-Binaphthyl-6-yl)-4',4"-diphenyltriphenylamine (abbreviation: BBAαNβNB), 4,4'-Diphenyl-4"-(7;1'-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB-03), 4,4'-Diphenyl-4"-(7-phenyl)naphthyl-2-yltriphenylamine (abbreviation: BBAPβNB-03), 4-(6;2'-Binaphthyl-2-yl)-4',4"-diphenyltriphenylamine (abbreviation: BBA(βN2)B), 4-(2;2'-Binaphthyl-7-yl)-4',4"-diphenyltriphenylamine (abbreviation: BBA(βN2)B-03), 4-(1;2'-Binaphthyl-4-yl)-4',4"-diphenyltriphenylamine (abbreviation: BBAβNαNB), 4-(1;2'-Binaphthyl-5-yl)-4',4"-diphenyltriphenylamine (abbreviation: BBAβNαNB-02), 4-(4-Biphenylyl)-4'-(2-naphthyl)-4"-phenyltriphenylamine (abbreviation: TPBiAßNB), 4-(3-Biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4"-phenyltriphenylamine (abbreviation: mTPBiAßNBi), 4-(4-Biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4"-phenyltriphenylamine (Abbreviation: TPBiAßNBi), 4-(1-Naphthyl)-4'-phenyltriphenylamine (abbreviation: αNBA1BP), 4,4'-Bis(1-naphthyl)triphenylamine (abbreviation: αNBB1BP), 4,4'-Diphenyl-4"-[4'-(carbazol-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBi1BP), 4'-[4-(3-Phenyl-9H-carbazol-9-yl)phenyl]tris(1,1'-biphenyl-4-yl)amine (abbreviation: YGTBi1BP-02), 4-[4'-(Carbazol-9-yl)biphenyl-4-yl]-4'-(2-naphthyl)-4"-phenyltriphenylamine (abbreviation: YGTBißNB), N-[4-(9-Phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBNBSF), N,N-Bis([1,1'-biphenyl]-4-yl)-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: BBASF), N,N-Bis([1,1'-biphenyl]-4-yl)-9,9'-spirobi[9H-fluorene]-4-amine (abbreviation: BBASF(4)), N-(1,1'-Biphenyl-2-yl)-N-(9,9-dimethyl-9H-fluorene-2-yl)-9,9'-spirobi[9H-fluorene]-4-amine (abbreviation: oFBiSF), N-(4-Biphenyl)-N-(9,9-dimethyl-9H-fluorene-2-yl)dibenzofuran-4-amine (abbreviation: FrBiF), N-[4-(1-Naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBfBNBN), 4-Phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-Phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-Phenyl-4'-[4-(9-phenylfluoren-9-yl)phenyl]triphenylamine (abbreviation: BPAFLBi), 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),N-Phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBASF) and N-(1,1'-Biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluorene-2-amine (abbreviation: PCBBiF).

[0047] The hole transport layer 112 comprises a first hole transport layer 112-1 and a second hole transport layer 112-2. The first hole transport layer 112-1 is located closer to the side of the anode 101 than the second hole transport layer 112-2. It should be noted that the second hole transport layer 112-2 also serves as an electron blocking layer in some cases.

[0048] The first hole transport layer 112-1 and the second hole transport layer 112-2 contain a third organic compound and a fourth organic compound, respectively.

[0049] The third and fourth organic compounds are preferably organic compounds with hole-transport properties. The organic compound that can be used as the second organic compound can be used similarly as the third and fourth organic compounds.

[0050] The materials for the second and third organic compounds are preferably selected such that the HOMO level of the third organic compound is lower than that of the second organic compound and the difference between the HOMO levels is less than or equal to 0.2 eV. More preferably, the second and third organic compounds are the same substance.

[0051] Furthermore, the HOMO level of the fourth organic compound is preferably lower than that of the third organic compound. Materials for the third and fourth organic compounds are preferably selected such that the difference between their HOMO levels is less than or equal to 0.2 eV. Thanks to the relationship between the HOMO levels of the second to the fourth organic compound described above, holes are readily injected into each layer, preventing an increase in operating voltage and a lack of holes in the light-emitting layer.

[0052] The second to fourth organic compounds each preferably have a hole-transporting framework. Preferably, a carbazole framework, a dibenzofuran framework, a dibenzothiophene framework, or anthracene framework is used as the hole-transporting framework, ensuring that the HOMO levels of the organic compounds do not become too shallow. Materials for adjacent layers (e.g., the second and third organic compounds, or the third and fourth organic compounds) preferably have the same hole-transporting framework, allowing for easy hole injection. In particular, a dibenzofuran framework is preferably used as the hole-transporting framework.

[0053] Furthermore, materials contained in adjacent layers (e.g., the second organic compound and the third organic compound, or the third organic compound and the fourth organic compound) are preferably identical, in which case holes can be easily injected. In particular, the second organic compound and the third organic compound are preferably the same material.

[0054] The light-emitting layer 113 contains a fifth organic compound and a sixth organic compound. The fifth organic compound is an emission center substance, and the sixth organic compound is a host material in which the fifth organic compound is to be dispersed.

[0055] Fluorescent substances, phosphorescent substances, substances emitting thermally activated delayed fluorescence (TADF), or other light-emitting materials can be used as the emission center substance. Furthermore, the light-emitting layer 113 can be a single layer or comprise a plurality of layers containing different light-emitting materials. It should be noted that one embodiment of the present invention is preferred in which the light-emitting layer 113 emits a fluorescence, in particular a blue fluorescence.

[0056] Examples of the material that can be used as a fluorescent substance in the light-emitting layer 113 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-(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''',N'''-Octaphenyldibenzo[g,p] / / / rysene-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: 2DPAPPhA), 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 545T, N,N'-Diphenylquinacridone,(Abbreviation: DPQd), Rubrene, 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)propanenitrile (Abbreviation: DCM1), 2-{2-Methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[lj]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene} propanenitrile (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)propanenitrile (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}propanenitrile (abbreviation: BisDCJTM) and N,N'-(pyrene-1-,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-03), 3,10-Bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02), 3,10-Bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02). Condensed aromatic diamine compounds, typically pyrenediamine compounds such as 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03, are particularly preferred due to their high hole-trapping properties, high emission efficiency, and high reliability. Other fluorescent substances can also be used.

[0057] Examples of materials that can be used when a phosphorescent substance is used as the emission center substance in the light-emitting layer 113 are as follows: a metal-organic iridium complex with a 4H-triazole framework, 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]) and Tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(iPrptz-3b)3]), an organometallic iridium complex with a 1H-triazole skeleton, such as e.g. B. 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]), a metal-organic iridium complex with an imidazole skeleton, 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 an organometallic iridium complex 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: Firpic), 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: FIr(acac)). These compounds emit blue phosphorescence and exhibit an emission peak at 440 nm to 520 nm.

[0058] Other examples include organometallic iridium complexes with a pyrimidine framework, such as... B. Tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)3]), Tris(4-tert-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[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [[Ir(nbppm)2(acac)]), (Acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmppm)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 skeleton, 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)]), and a rare-earth metal complex, such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac)3(Phen)]). These are mainly compounds that emit green phosphorescence and exhibit an emission peak at 500 nm to 600 nm. It should be noted that organometallic iridium complexes with a pyrimidine framework exhibit significantly higher reliability and emission efficiency and are therefore particularly preferred.

[0059] Other examples include organometallic iridium complexes with a pyrimidine framework, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinatoiridium(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 with a pyrazine framework, such as... 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)quinoxalinatoiridium(III) (abbreviation: [Ir(Fdpq)2(acac)]), organometallic iridium complexes with a pyridine skeleton, 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)]), platinum complexes, such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatin(II) (abbreviation: [PtOEP]), and rare earth metal complexes, such as Tris(1,3-diphenyl-1,3-propanediumato)(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)]). These compounds emit red phosphorescence with an emission peak at 600 nm to 700 nm. Furthermore, the metal-organic iridium complexes with a pyrazine framework can provide red light emission with advantageous chromaticity.

[0060] In addition to the above phosphorescent compounds, other known phosphorescent materials can also be selected and used.

[0061] Examples of TADF material include a fullerene, a derivative thereof, an acridine, a derivative thereof, and an eosin derivative. Furthermore, a metal-containing porphyrin, such as a porphyrin containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd), may be specified. 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(Hämato 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), which are represented by the following structural formulas.

[0062] Alternatively, a heterocyclic compound that has a π-electron-rich heteroaromatic ring and / or a π-electron-poor heteroaromatic ring and is represented by one of the following structural formulas, such as... B. 2-(Biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviation: PCCzTzn) (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-dihydroacridin)phenyl]sulfone (abbreviation: DMAC-DPS) or 10-Phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (abbreviation: ACRSA).Such a heterocyclic compound is preferred due to its excellent electron and hole transport properties, as it comprises a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring. Among frameworks with the π-electron-deficient heteroaromatic ring, a pyridine framework, a diazine framework (a pyrimidine framework, a pyrazine framework, and a pyridazine framework), and a triazine framework are preferred due to their high stability and reliability. In particular, a benzofuropyrimidine framework, a benzothienopyrimidine framework, a benzofuropyrazine framework, and a benzothienopyrazine framework are preferred due to their high acceptor properties and reliability.Among frameworks with the π-electron-rich heteroaromatic ring, an acridine framework, a phenoxazine framework, a phenothiazine framework, a furan framework, a thiophene framework, and a pyrrole framework exhibit high stability and reliability; consequently, at least one of these frameworks is preferably included. A dibenzofuran framework is preferred as the furan framework. A dibenzothiophene framework is preferred as the thiophene framework. In particular, an indole framework, a carbazole framework, an indolocarbazole framework, a bicarbazole framework, and a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole framework are preferred as the pyrrole framework.It should be noted that a substance in which the π-electron-rich heteroaromatic ring is directly bonded to the π-electron-poor heteroaromatic ring is particularly preferred, since both the electron-donating property of the π-electron-rich heteroaromatic ring and the electron-accepting property of the π-electron-poor heteroaromatic ring are improved, and the energy difference between the S1 level and the T1 level becomes small; therefore, thermally activated delayed fluorescence can be obtained with high efficiency. It should also be noted that an aromatic ring to which an electron-withdrawing group, such as a cyano group, is bonded can be used instead of the π-electron-poor heteroaromatic ring. An aromatic amine framework, a phenazine framework, or the like can be used as the π-electron-rich framework.A π-electron-deficient framework can be a xanthene framework, a thioxanthene dioxide framework, an oxadiazole framework, a triazole framework, an imidazole framework, an anthraquinone framework, a boron-containing framework such as phenylborane or boranthrene, an aromatic ring or a heteroaromatic ring with a cyano group or a nitrile group such as benzonitrile or cyanobenzene, a carbonyl framework such as benzophenone, a phosphine oxide framework, a sulfone framework, or the like. As described above, a π-electron-deficient framework and a π-electron-rich framework can be used instead of the π-electron-deficient heteroaromatic ring and / or the π-electron-rich heteroaromatic ring.

[0063] The TADF material is preferably a substance represented by one of the following general formulas (G1) to (G11).

[0064] It should be noted that in the above general formula (G1) at least one of R 1 to R 5 represents a cyano group, at least one of R 1 to R 5 a substituted or unsubstituted 9-carbazolyl group, a substituted or unsubstituted 1,2,3,4-tetrahydro-9-carbazolyl group, a substituted or unsubstituted 1-indolyl group, or a substituted or unsubstituted diarylamino group, and the others of R 1 to R 5 each can independently represent a hydrogen atom or a substituent.

[0065] In the above general formula (G2), R represents 11 and R 12each independently represents a hydrogen atom or any substituent, and A represents a substituent in which at least one heteroaryl group that may have a substituent, or at least one arylamino group that may have a substituent, is bonded directly or via an aromatic group to carbon in the 4-position of a pyridine ring.

[0066] In the above general formula (G3), Ar represent 1 to Ar 3 each represents an aryl group, and at least one of Ar 1 to Ar 3 represents an aryl group that is substituted by a dibenzo-1,4-oxazine group or a dibenzo-1,4-thiazine group.

[0067] In the general formula above (G4), X represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted fused polycyclic aromatic group, or a disubstituted amino group substituted by groups selected from an aromatic hydrocarbon group, an aromatic heterocyclic group, and a fused polycyclic aromatic group. Y represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group, which may have one substituent and has 1 to 6 carbon atoms, a cycloalkyl group, which may have one substituent and has 5 to 10 carbon atoms, or a linear or branched alkenyl group.which may have one substituent and has 2 to 6 carbon atoms, a linear or branched alkyloxy group which may have one substituent and has 1 to 6 carbon atoms, a cycloalkyloxy group which may have one substituent and has 5 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted fused polycyclic aromatic group, a substituted or unsubstituted aryloxy group, or a disubstituted amino group which is substituted by groups selected from an aromatic hydrocarbon group, an aromatic heterocyclic group, and a fused polycyclic aromatic group. R, 21 , R 22 and R 25 to R 28, which may be identical or different from each other, each independently represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group which may have one substituent and has 1 to 6 carbon atoms, a cycloalkyl group which may have one substituent and has 5 to 10 carbon atoms, a linear or branched alkenyl group which may have one substituent and has 2 to 6 carbon atoms, a linear or branched alkyloxy group which may have one substituent and has 1 to 6 carbon atoms, a cycloalkyloxy group which may have one substituent and has 5 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group,a substituted or unsubstituted fused polycyclic aromatic group, a substituted or unsubstituted aryloxy group, or a disubstituted amino group substituted by groups selected from an aromatic hydrocarbon group, an aromatic heterocyclic group, and a fused polycyclic aromatic group. R, 21 , R 22 and R 25 to R 28 They can be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0068] In the above general formula (G5) A 1 to A 3 Each independently represents a substituted or unsubstituted dibenzofuranyl group.

[0069] In the above general formula (G6) R 31 to R 34and a to h each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group with 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group with 1 to 20 carbon atoms, a substituted or unsubstituted aryl group with 6 to 20 carbon atoms or an amino group.

[0070] In the above general formula (G7) R 41 to R 48 each independently represents a hydrogen atom or an electron donor group, and at least one of R 41 to R 48 represents an electron donor group. R 49 to R 56 each independently represents a hydrogen atom or an electron-withdrawing group other than a triazino group, and at least one of R 49 to R 56represents a different electron-withdrawing group than a triazino group. It should be noted that 11 to 14 of R 41 to R 56 Represent hydrogen atoms.

[0071] In the above general formula (G8), R represents 61 to R 68 and R 77 each independently represents a hydrogen atom or an electron donor group, and at least one of R 61 to R 68 and R 77 represents an electron donor group. R 69 to R 76 Each of the following represents, independently of one another, a hydrogen atom or an electron-withdrawing group that does not have a shared electron pair in the α-position. Z represents a single bond or =C=Y, while YS represents C(CN)₂ or C(COOH)₂. It should be noted that if Z represents a single bond, at least one of R represents 69 to R 76represents an electron-withdrawing group that does not have an undivided electron pair in the α position.

[0072] In the general formula (G9) above, ring α is an aromatic ring condensed at an arbitrary position with an adjacent ring and is represented by formula (g9-1), and ring β is a heterocycle condensed at an arbitrary position with an adjacent ring and is represented by formula (g9-2). Ar in formula (G9) and Ar in formula (g9-2) each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group.Rs in formula (G9) and Rs in formula (g9-1) each independently represent hydrogen or a monovalent substituent selected from the group consisting of an alkyl group with 1 to 10 carbon atoms, an alkoxy group with 1 to 10 carbon atoms, an alkylthio group with 1 to 10 carbon atoms, an alkylamino group with 1 to 10 carbon atoms, an acyl group with 2 to 10 carbon atoms, an aralkyl group with 7 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group with 6 to 30 carbon atoms, and a substituted or unsubstituted six-membered aromatic heterocyclic group with 3 to 30 carbon atoms, and the substituents that are adjacent may be bonded to each other to form a ring. n represents an integer greater than or equal to 1 and less than or equal to 4.

[0073] In the above general formula (G10), X represents 1 , X 2 and X 3, which may be the same or different from each other, each independently containing a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group which may have one substituent and has 1 to 6 carbon atoms, a cycloalkyl group which may have one substituent and has 5 to 10 carbon atoms, a linear or branched alkenyl group which may have one substituent and has 2 to 6 carbon atoms, a linear or branched alkyloxy group which may have one substituent and has 1 to 6 carbon atoms, a cycloalkyloxy group which may have one substituent and has 5 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group,a substituted or unsubstituted fused polycyclic aromatic group, a substituted or unsubstituted aryloxy group, or a disubstituted amino group substituted by groups selected from an aromatic hydrocarbon group, an aromatic heterocyclic group, and a fused polycyclic aromatic group. At least one of X, 1 , X 2 and X 3 represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted fused polycyclic aromatic group, or a disubstituted amino group substituted by groups selected from an aromatic hydrocarbon group, an aromatic heterocyclic group, and a fused polycyclic aromatic group. Ar 4represents a substituted or unsubstituted divalent aromatic hydrocarbon group, a substituted or unsubstituted divalent heteroaromatic hydrocarbon group, or a substituted or unsubstituted divalent fused polycyclic aromatic hydrocarbon group. R 81 to R 86 and R 89 to R 94, which may be identical or different from each other, each independently represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a linear or branched alkyl group which may have one substituent and has 1 to 6 carbon atoms, a cycloalkyl group which may have one substituent and has 5 to 10 carbon atoms, a linear or branched alkenyl group which may have one substituent and has 2 to 6 carbon atoms, a linear or branched alkyloxy group which may have one substituent and has 1 to 6 carbon atoms, a cycloalkyloxy group which may have one substituent and has 5 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group,a substituted or unsubstituted fused polycyclic aromatic group, a substituted or unsubstituted aryloxy group, or a disubstituted amino group substituted by groups selected from an aromatic hydrocarbon group, an aromatic heterocyclic group, and a fused polycyclic aromatic group. R, 81 to R 86 and R 89 to R 94 They can be bonded to each other via a single bond, a substituted or unsubstituted methylene group, an oxygen atom, or a sulfur atom to form a ring.

[0074] In the above general formula (G11), R represents 101 to R 104each independently represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted cycloalkyl group, R 105 and R 106 Each independently represents a substituted or unsubstituted alkyl group, R 107 , R 108 and R 109 Each independently represents a substituted or unsubstituted aryl group or a substituted or unsubstituted alkyl group; n1 to n4 and n7 each independently represent an integer selected from 0 to 4; n5 and n6 each independently represent an integer selected from 0 to 3; and n8 and n9 each independently represent an integer selected from 0 to 5. If n1 to n9, which each represent R 101 to R109 corresponding to an integer of 2 or more, R 101 s may be the same or different from each other; the same applies to R 102 to R 109 .

[0075] It should be noted that a TADF material is one that exhibits a small difference between the S1 and T1 levels and possesses a function for converting triplet excitation energy to singlet excitation energy via reverse intersystem crossing. Thus, a TADF material can, using a small amount of thermal energy, convert triplet excitation energy upwards to singlet excitation energy (i.e., reverse intersystem crossing) and efficiently generate a singlet excitation state. Furthermore, the triplet excitation energy can be converted into luminescence.

[0076] An exciplex whose excitation state is formed by two types of substances has a very small difference between the S1 level and the T1 level and serves as a TADF material that can convert the triplet excitation energy into the singlet excitation energy.

[0077] A phosphorescence spectrum observed at low temperature (e.g., 77 K to 10 K) is used to define the T1 level. If the energy level corresponding to a wavelength of the line obtained by extrapolating a tangent to the fluorescence spectrum at a tail on the short-wavelength side is the S1 level, and the energy level corresponding to a wavelength of the line obtained by extrapolating a tangent to the phosphorescence spectrum at a tail on the short-wavelength side is the T1 level, then the difference between the S1 level and the T1 level of the TADF material is preferably less than or equal to 0.3 eV, more preferably less than or equal to 0.2 eV.

[0078] When the TADF material is used as the emission center substance, the S1 level and the T1 level of the host material are preferably higher than those of the TADF material.

[0079] Various charge carrier transport materials can be used as host material for the light-emitting layer, such as materials with electron transport properties, materials with hole transport properties, and TADF materials.

[0080] Examples of materials with hole transport properties include compounds with an aromatic amine skeleton, such as: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-(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) and N-Phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBASF), compounds with a carbazole skeleton, such as... B.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 3,3'-Bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), compounds 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) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and compounds with a furan skeleton, 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 aforementioned materials, the compound with an aromatic amine framework and the compound with a carbazole framework are preferred because these compounds are very reliable and exhibit high hole transport properties, thus contributing to a reduction in operating stress. Furthermore, the organic compounds given as examples of the second organic compound mentioned above can also be used.

[0081] Examples of materials with electron transport properties include metal complexes, such as bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminium(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 a polyazole skeleton, such as...2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-Biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-Bis[5-(p-tert-butylphenyl)-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), 2-[3-(Dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II) and 2-{4-[9,10-Di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN), heterocyclic compounds with a diazine backbone, 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), 4,6-Bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm) and 4,6-Bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), and heterocyclic compounds with a pyridine skeleton, such as 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 aforementioned materials, the heterocyclic compound with a diazine backbone and the heterocyclic compound with a pyridine backbone exhibit high reliability and are therefore preferable.In particular, the heterocyclic compound with a diazine (pyrimidine or pyrazine) framework exhibits excellent electron transport properties, thereby contributing to a reduction in operating voltage.

[0082] The materials mentioned above can also be used as TADF material, serving as the host material. When the TADF material is used as the host material, the triplet excitation energy generated within it is converted into singlet excitation energy via reverse intersystem crossing and transferred to the emission center substance, thereby increasing the emission efficiency of the light-emitting device. Here, the TADF material acts as an energy donor, and the emission center substance acts as an energy acceptor.

[0083] This is very effective when the emission center substance is a fluorescent substance. In this case, the S1 level of the TADF material is preferably higher than the S1 level of the fluorescent substance to achieve high emission efficiency. Furthermore, the T1 level of the TADF material is preferably higher than the S1 level of the fluorescent substance. Therefore, the T1 level of the TADF material is preferably higher than the T1 level of the fluorescent substance.

[0084] A TADF material that emits light whose wavelength overlaps with the wavelength of an absorption band on the lowest energy side of the fluorescent substance is preferably used, wherein in this case the excitation energy is easily transferred from the TADF material to the fluorescent substance and light emission can be efficiently obtained.

[0085] Furthermore, charge carrier recombination preferably takes place in the TADF material so that the singlet excitation energy is efficiently generated from the triplet excitation energy by reverse intersystem crossing. It is also preferable that the triplet excitation energy generated in the TADF material is not transferred to the triplet excitation energy of the fluorescent substance. For this reason, the fluorescent substance preferably has a protecting group around a luminophore (a framework that generates light emission) of the fluorescent substance. Preferably, a substituent lacking a π-bond and a saturated hydrocarbon are used as the protecting group. Specific examples include an alkyl group with 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 to 10 carbon atoms, and a trialkylsilyl group with 3 to 10 carbon atoms.It is further preferable that the fluorescent substance has a variety of protecting groups. The substituents that do not have a π-bond exhibit poor charge carrier transport properties, which allows the TADF material and the luminophore of the fluorescent substance to be separated from each other with little impact on charge carrier transport or recombination. Here, the luminophore denotes a group of atoms (a framework) that generates light emission in a fluorescent substance. The luminophore is preferably a framework with a π-bond, more preferably it comprises an aromatic ring, and even more preferably it comprises a fused aromatic ring or a fused heteroaromatic ring.Examples of condensed aromatic rings or condensed heteroaromatic rings include phenanthrene, stilbene, acridone, phenoxazine, and phenothiazine frameworks. In particular, a fluorescent compound with a naphthalene, anthracene, fluorene, chrysene, triphenylene, tetracene, pyrene, perylene, coumarin, quinacridone, or naphthobisbenzofuran framework is preferred due to its high fluorescence quantum yield.

[0086] In cases where a fluorescent substance is used as the emission center material, a material with an anthracene framework is preferably used as the host material. Using a substance with an anthracene framework as the host material for the fluorescent substance allows for the creation of a light-emitting layer with high emission efficiency and high stability. Among the substances with an anthracene framework, a substance with a diphenylanthracene framework, in particular a substance with a 9,10-diphenylanthracene framework, is chemically stable and is therefore preferably used as the host material.The host material preferably has a carbazole framework, as this improves the hole injection and hole transport properties; more preferably, the host material has a benzocarbazole framework in which a benzene ring is further condensed to carbazole, since its HOMO level is approximately 0.1 eV shallower than that of carbazole, thus facilitating hole penetration into the host material. In particular, the host material preferably has a dibenzocarbazole framework, as its HOMO level is approximately 0.1 eV shallower than that of carbazole, thus facilitating hole penetration into the host material, improving the hole transport properties, and increasing heat resistance. Consequently, a substance having both a 9,10-diphenylanthracene framework and a carbazole framework (or a benzocarbazole or dibenzocarbazole framework) is further preferred as a host material.It should be noted that, with regard to the hole injection and hole transport properties described above, a benzofluorene scaffold or a dibenzofluorene scaffold can be used instead of a carbazole scaffold. Examples of such substances include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3-[4-(1-naphthyl)phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-Phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4'-yl}anthracene (abbreviation: FLPPA) and 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth). It should be noted that CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA exhibit excellent properties and are therefore preferably selected.

[0087] It should be noted that the host material can be a mixture of several types of substances; in the case of using a mixed host material, a material with electron transport properties is preferably mixed with a material with hole transport properties. By mixing the material with electron transport properties with the material with hole transport properties, the transport properties of the light-emitting layer 113 can be easily adjusted, and a recombination range can be easily controlled. The weight ratio of the content of the material with hole transport properties to the content of the material with electron transport properties can be from 1:19 to 19:1.

[0088] It should be noted that a phosphorescent substance can be used as part of the mixture. If a fluorescent substance is used as the emission center substance, a phosphorescent substance can be used as an energy donor to supply the excitation energy to the fluorescent substance.

[0089] An exciplex can be formed from these mixed materials. If these materials are selected to form an exciplex that emits light whose wavelength overlaps with the wavelength of an absorption band on the lowest energy side of the light-emitting material, energy can be easily transferred and efficient light emission can be achieved. The use of such a structure is preferred because the operating voltage can also be reduced.

[0090] It should be noted that at least one of the materials forming an exciplex can be a phosphorescent substance. In this case, the triplet excitation energy can be efficiently converted into the singlet excitation energy by reverse intersystem crossing.

[0091] A combination of a material with electron transport properties and a material with hole transport properties, whose HOMO level is higher than or equal to that of the material with electron transport properties, is preferred for the efficient formation of an exciplex. Furthermore, the LUMO level of the material with hole transport properties is preferably higher than or equal to the LUMO level of the material with electron transport properties. It should be noted that the LUMO and HOMO levels of the materials can be obtained from the electrochemical properties (the reduction potentials and the oxidation potentials) of the materials, which are measured by cyclic voltammetry (CV).

[0092] The formation of an exciplex can be confirmed, for example, by a phenomenon in which the emission spectrum of the mixed film containing the material with a hole-transporting property and the material with an electron-transporting property is shifted towards the longer wavelength side than the emission spectra of each of the materials (or the emission spectrum exhibits a different peak on the longer wavelength side). This phenomenon is observed by comparing the emission spectra of the material with a hole-transporting property, the material with an electron-transporting property, and the mixed film of these materials. Alternatively, the formation of an exciplex can be confirmed by a difference in the transient response, such as...A phenomenon is confirmed in which the lifetime of the transient photoluminescence (PL) of the mixed film exhibits components with longer lifetimes or a larger proportion of delay components than that of each of the materials. This difference is observed by comparing the transient photoluminescence (PL) of the material with hole transport properties, the material with electron transport properties, and the mixed film of the materials. The transient PL can be reformulated as transient electroluminescence (EL). That is, the formation of an exciplex can also be confirmed by a difference in the transient response observed by comparing the transient EL of the material with hole transport properties, the material with electron transport properties, and the mixed film of the materials.

[0093] The electron transport layer 114 is provided in contact with the light-emitting layer 113. The electron transport layer 114 comprises a seventh organic compound with electron transport properties and a HOMO level of -6.0 eV or higher. The seventh organic compound is an organic compound with electron transport properties and preferably has an anthracene framework. The electron transport layer 114 may further comprise an eighth substance, which is an organic complex of an alkali metal or an alkaline earth metal. That is to say, the electron transport layer 114 can be formed from the seventh organic compound alone or from a mixture containing the seventh organic compound and another substance, such as a mixture of the seventh organic compound and the eighth substance.

[0094] The seventh organic compound more preferably has an anthracene framework and a heterocyclic framework, and a nitrogen-containing five-membered ring framework is preferably used as the heterocyclic framework. The seventh organic compound preferably has a nitrogen-containing five-membered ring framework comprising two heteroatoms in one ring, such as a pyrazole ring, an imidazole ring, an oxazole ring, or a thiazole ring.

[0095] Alternatively, a material that has been specified as an organic compound with an electron transport property that can be used as a seventh organic compound, or as an organic compound that can be used as a host material for the fluorescent substance, can be used as an organic compound with an electron transport property that can be used as a host material.

[0096] The organic complex of an alkali metal or alkaline earth metal is preferably an organic complex of lithium and particularly preferably 8-hydroxyquinolinatelithium (abbreviation: Liq).

[0097] The electron mobility of the material contained in the electron transport layer 114 is, in the case where the square root of the electric field strength [V / cm] is 600, preferably higher than or equal to 1 × 10 -7 cm 2 / Vs and less than or equal to 5 × 10 -5 cm 2 / Vs.

[0098] Furthermore, the electron mobility of the material contained in the electron transport layer 114 is preferably lower than that of the sixth organic compound or the material contained in the light-emitting layer 113, provided the electric field strength [V / cm] is 600. The amount of electrons injected into the light-emitting layer can be controlled by reducing the electron transport property of the electron transport layer, thus preventing the light-emitting layer from having excess electrons.

[0099] If the light-emitting layer has excess electrons, it is a light-emitting region 113-1, as shown in Fig. 2A, as shown, is limited to a portion and is subjected to high stress, which promotes deterioration. Furthermore, electrons that cannot recombine and pass through the light-emitting layer also reduce emission efficiency and lifetime. In one embodiment of the present invention, the reduction in the electron transport property of the electron transport layer 114, as shown in Fig. Figure 2B shows the light-emitting area 113-1 and distributes the load over the material contained in the light-emitting layer 113. Therefore, a light-emitting device with a long lifetime and high emission efficiency can be provided.

[0100] The decay curve of a light-emitting device with such a structure, obtained through an operational test at constant current density, exhibits a local maximum value in some cases. In other words, the shape of the decay curve of the light-emitting device of an embodiment of the present invention may include a section in which the luminance increases over time. The light-emitting device exhibiting such deterioration behavior allows the rapid decay in the first operating stage, known as initial decay, to be counteracted by the increase in luminance. This enables the light-emitting device to have a very long lifetime with a reduced initial decay.

[0101] A differential value of such a decay curve with a local maximum value is 0 in one part. In other words, the light-emitting device of an embodiment of the present invention, whose decay curve has a differential value of 0 in one part, can have a very long lifetime with a lower initial decay.

[0102] As in Fig. As shown in Figure 3A, this phenomenon is probably caused by recombination that does not contribute to light emission in a non-light-emitting recombination region 114-1. In a light-emitting device of the present invention with the structure described above, the hole injection barrier in the first operating stage is small and the electron transport property of the electron transport layer 114 is relatively low; consequently, the light-emitting region 113-1 (i.e., recombination region) is formed on the side of the electron transport layer 114.Since the HOMO level of the seventh organic compound contained in electron transport layer 114 is -6.0 eV or higher, which is relatively high, some holes even reach the electron transport layer 114, causing recombination there as well; therefore, the non-light-emitting recombination region 114-1 is formed. This phenomenon also occurs in some cases where the difference between the HOMO levels of the sixth and seventh organic compounds is 0.2 eV or less.

[0103] As the operating time changes the charge carrier equilibrium, the light-emitting region 113-1 (recombination region) shifts, as shown in Fig. Figure 3B shows the direction of the hole transport layer 112. A reduction in the non-light-emitting recombination region 114-1 allows the energy of the recombining charge carriers to contribute effectively to light emission, thus increasing the luminance. This increase in luminance counteracts the rapid decrease in luminance during the first operating stage, known as initial decay, of the light-emitting device. Therefore, the light-emitting device can have a long operating time with less initial decay.

[0104] If the initial decay can be reduced, the problem of burn-in, which is still mentioned as a major disadvantage of organic EL devices, as well as the time and labor required for aging to reduce the problem before shipping, can be significantly reduced.

[0105] The light-emitting device of an embodiment of the present invention with the structure described above can have a long service life. (Version 2)

[0106] Next, examples of specific structures and materials of the aforementioned light-emitting device are described. As described above, the light-emitting device of an embodiment of the present invention includes the EL layer 103, which is positioned between the pair of electrodes (the anode 101 and the cathode 102) and has a plurality of layers. The EL layer 103 comprises the hole injection layer 111, the first hole transport layer 112-1, the second hole transport layer 112-2, the light-emitting layer 113, and the electron transport layer from the side of the anode 101.

[0107] There is no particular restriction regarding the other layers contained in the EL layer 103, and various layers, such as a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, a charge carrier blocking layer, an exciton blocking layer, and a charge generation layer, can be used.

[0108] The anode 101 is preferably formed using a metal, an alloy, a conductive compound with a high work function (particularly a work function greater than or equal to 4.0 eV), a mixture thereof, or the like. Specific examples include indium tin oxide (ITO), indium tin oxide containing silicon or silicon oxide, indium zinc oxide, and indium oxide containing tungsten oxide and zinc oxide (IWZO). Such conductive metal oxide films are generally formed by a sputtering process, but can also be formed by a sol-gel process or the like. In one example of the formation process, indium zinc oxide is deposited by a sputtering process using a target obtained by adding 1 wt.% to 20 wt.% zinc oxide to indium oxide.Furthermore, an indium oxide film containing tungsten oxide and zinc oxide (IWZO) can be formed by a sputtering process using a target in which 0.5 wt% to 5 wt% tungsten oxide and 0.1 wt% to 1 wt% zinc oxide are added to the indium oxide. Alternatively, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), a nitride of a metallic material (e.g., titanium nitride), or the like can be used. Graphene can also be used.It should be noted that, although the typical materials for forming the anode have been listed above, a composite material consisting of an organic compound with a hole transport property and a substance having an electron acceptor property with respect to the organic compound is used for the hole injection layer 111 of an embodiment of the present invention; therefore, an electrode material can be selected independently of its work function.

[0109] Two types of multilayered structures of EL layer 103 are described, namely one in Fig. 1A structure shown, comprising the electron injection layer 115 in addition to the hole injection layer 111, the first hole transport layer 112-1, the second hole transport layer 112-2, the light-emitting layer 113 and the electron transport layer 114, and a in Fig. The structure shown in Figure 1B comprises a charge-generating layer 116 in addition to the hole-injection layer 111, the first hole-transport layer 112-1, the second hole-transport layer 112-2, the light-emitting layer 113, and the electron-transport layer 114. Materials for forming each layer are described in detail below.

[0110] Since the hole injection layer 111, the hole transport layer 112 (the first hole transport layer 112-1 and the second hole transport layer 112-2), the light-emitting layer 113, and the electron transport layer 114 have been described in detail in the section on embodiment 1, their description is not repeated here. Reference may be made to the description of embodiment 1.

[0111] An electron injection layer 115 between the electron transport layer 114 and the cathode 102 can be a layer containing an alkali metal, an alkaline earth metal, or a compound thereof, such as lithium fluoride (LiF), cesium fluoride (CsF), or calcium fluoride (CaF₂). For example, an electrid or a layer formed using a substance with electron transport properties and containing an alkali metal, an alkaline earth metal, or a compound thereof can be used as the electron injection layer 115. Examples of the electrid include a substance in which electrons are added to calcium oxide-aluminum oxide at a high concentration.

[0112] Instead of the electron injection layer 115, the charge generation layer 116 can be provided between the electron transport layer 114 and the cathode 102 ( Fig. 1B). The charge-generating layer 116 is a layer capable of injecting holes into a layer in contact with the cathode side of the charge-generating layer 116 and electrons into a layer in contact with its anode side when a potential is applied. The charge-generating layer 116 comprises at least one p-type layer 117. The p-type layer 117 is preferably formed using one of the composite materials given above as examples of materials that can be used for the hole injection layer 111. The p-type layer 117 can be formed by layering a film containing the acceptor material described above and a film containing a hole transport material on top of each other.When a potential is applied to the p-type layer 117, electrons are injected into the electron transport layer 114 and holes into the cathode 102, which serves as the cathode; this is how the light-emitting device works.

[0113] It should be noted that the charge generation layer 116 preferably comprises, in addition to the p-type layer 117, an electron conduction layer 118 and / or an electron injection buffer layer 119.

[0114] The electron conduction layer 118 contains at least the substance with electron transport properties and has a function for preventing interaction between the electron injection buffer layer 119 and the p-type layer 117 and a function for the smooth transfer of electrons. The LUMO level of the substance with electron transport properties contained in the electron conduction layer 118 is preferably between the LUMO level of the electron acceptor substance in the p-type layer 117 and the LUMO level of a substance in a layer of the electron transport layer 114 that is in contact with the charge generation layer 116. Specifically, the LUMO level of the substance with electron transport properties in the electron conduction layer 118 is preferably higher than or equal to -5.0 eV, more preferably higher than or equal to -5.0 eV and lower than or equal to -3.0 eV.It should be noted that the substance with an electron transport property in the electron conduction layer 118 is preferably a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand.

[0115] A substance with high electron injection properties can be used for the electron injection buffer layer 119. For example, an alkali metal, an alkaline earth metal, a rare earth metal, or a compound thereof (an alkali metal compound (including an oxide, such as lithium oxide, a halide, and a carbonate, such as lithium carbonate and cesium carbonate), an alkaline earth metal compound (including an oxide, a halide, and a carbonate), or a rare earth metal compound (including an oxide, a halide, and a carbonate)) can be used.

[0116] In the case where the electron injection buffer layer 119 contains the substance with electron transport properties and a substance with electron donation properties, an organic compound such as tetrathianaphthacene (abbreviation: TTN), nickelocene, or decamethylnickelocene can be used as the substance with electron donation properties, as can an alkali metal, an alkaline earth metal, a rare earth metal, or a compound thereof (an alkali metal compound (including an oxide, such as lithium oxide, a halide, and a carbonate, such as lithium carbonate and cesium carbonate), an alkaline earth metal compound (including an oxide, a halide, and a carbonate), or a rare earth metal compound (including an oxide, a halide, and a carbonate)). A material similar to the material described above for the electron transport layer 114 can be used as the substance with electron transport properties.

[0117] For the cathode 102, a metal, alloy, electrically conductive compound, or a mixture thereof, each exhibiting a low work function (particularly a work function of less than or equal to 3.8 eV), or the like, can be used. Specific examples of such a cathode material are elements belonging to groups 1 and 2 of the periodic table, such as alkali metals (e.g., lithium (Li) and cesium (Cs)), magnesium (Mg), calcium (Ca), and strontium (Sr), alloys containing these elements (e.g., MgAg and AlLi), rare-earth metals, such as europium (Eu) and ytterbium (Yb), and alloys containing these rare-earth metals. However, once the electron injection layer between the cathode 102 and the electron transport layer is provided, various conductive materials, such as…Aluminum, silver, ITO, or indium oxide-tin oxide containing silicon or silicon oxide can be used for cathode 102, regardless of the work function. Films of these conductive materials can be formed by a dry process, such as vacuum evaporation, sputtering, inkjet printing, spin coating, or the like. Alternatively, a wet process using a sol-gel or paste-based metallic material can be employed.

[0118] Furthermore, various methods can be used to form the EL layer 103, regardless of whether it is a dry or wet process. For example, a vacuum evaporation process, a gravure printing process, an offset printing process, a screen printing process, an inkjet process, a rotary coating process, or the like can be used.

[0119] Different methods can be used to form the electrodes or layers described above.

[0120] The structure of the layers provided between the anode 101 and the cathode 102 is not limited to the structure described above. Preferably, a light-emitting region, in which holes and electrons recombine, is located away from the anode 101 and the cathode 102, so that quenching due to the proximity between the light-emitting region and a metal used for electrodes and charge carrier injection layers can be prevented.

[0121] In order to suppress the energy transfer of an exciton generated in the light-emitting layer, the hole transport layer and the electron transport layer, which are in contact with the light-emitting layer 113, and in particular a charge carrier transport layer which is closer to the recombination region in the light-emitting layer 113, are preferably formed using a substance which has a larger band gap than the light-emitting material of the light-emitting layer or the light-emitting material which is contained in the light-emitting layer.

[0122] Next, an embodiment of a light-emitting device with a structure in which a plurality of light-emitting units are arranged one above the other (this type of light-emitting device is also referred to as a multilayer or tandem light-emitting device) is described using the following examples: Fig. 1C described. This light-emitting device includes a plurality of light-emitting units between an anode and a cathode. A light-emitting unit has essentially the same structure as the EL layer 103 described in Fig. 1A is shown. In other words: The light-emitting device that is shown in Fig. 1A or Fig. Figure 1B shows a single light-emitting unit, and the light-emitting device shown in Fig. 1C, as represented, includes a variety of light-emitting units.

[0123] In Fig. In 1C, a first light-emitting unit 511 and a second light-emitting unit 512 are arranged one above the other between an anode 501 and a cathode 502, and a charge-generating layer 513 is provided between the first light-emitting unit 511 and the second light-emitting unit 512. The anode 501 and the cathode 502 correspond to the anode 101 and the cathode 102, respectively, in Fig. 1A, and the materials used in the description of the Fig. The values ​​specified in 1A can be used. Furthermore, the first light-emitting unit 511 and the second light-emitting unit 512 can have the same or different structures.

[0124] The charge-generating layer 513 has a function for injecting electrons into one of the light-emitting units and injecting holes into the other of the light-emitting units when a voltage is applied between the anode 501 and the cathode 502. That is to say, in Fig. 1C injects electrons into the first light-emitting unit 511 and holes into the second light-emitting unit 512 into the charge-generating layer 513 when a voltage is applied such that the potential of the anode is higher than the potential of the cathode.

[0125] The charge generation layer 513 preferably has a structure similar to that of the one described by Fig. The charge-generating layer 116 described in 1B is similar. A composite material consisting of an organic compound and a metal oxide exhibits excellent charge carrier injection and transport properties; consequently, low-voltage and low-current operation can be achieved. In the case where a surface of a light-emitting unit on the anode side is in contact with the charge-generating layer 513, the charge-generating layer 513 can also serve as a hole injection layer for the light-emitting unit; therefore, a hole injection layer does not necessarily need to be provided within the light-emitting unit itself.

[0126] In the case where the charge generation layer 513 includes the electron injection buffer layer 119, the electron injection buffer layer 119 serves as an electron injection layer in the light-emitting unit on the anode side; therefore, an electron injection layer does not necessarily have to be formed in the light-emitting unit on the anode side.

[0127] The light-emitting device, which has two light-emitting units, is described by means of Fig. 1C described; however, an embodiment of the present invention can also be applied to a light-emitting device in which three or more light-emitting units are arranged one above the other. When a plurality of light-emitting units, separated by the charge-generating layer 513, are arranged between a pair of electrodes, as in the light-emitting device of this embodiment, it is possible to provide a long-life element capable of emitting light with high luminance at low current density. A light-emitting device that can be operated at low voltage and has low current consumption can be provided.

[0128] If the emission colors of the light-emitting units differ from one another, a light emission of a desired color can be obtained from the light-emitting device as a whole. For example, in a light-emitting device that has two light-emitting units, the emission colors of the first light-emitting unit can be red and green, and the emission color of the second light-emitting unit can be blue, so that the light-emitting device as a whole can emit white light.The light-emitting device, in which three or more light-emitting units are arranged one above the other, can, for example, be a tandem device in which a first light-emitting unit contains a first blue light-emitting layer, a second light-emitting unit contains a yellow or yellow-green light-emitting layer and a red light-emitting layer, and a third light-emitting unit contains a second blue light-emitting layer. The tandem device, like the light-emitting device described above, can provide white light emission.

[0129] The electrodes and layers described above, such as the EL layer 103, the first light-emitting unit 511, the second light-emitting unit 512, and the charge-generating layer, can be formed by a process such as evaporation (including vacuum evaporation), droplet ejection (also known as inkjet), coating, or gravure printing. Low-molecular-weight material, medium-molecular-weight material (including oligomers and dendrimers), or high-molecular-weight material can be incorporated into the layers and electrodes. (Version 3)

[0130] In this embodiment, a light-emitting device is described which includes the light-emitting device described in embodiments 1 and 2.

[0131] In this embodiment, the light-emitting device, which is manufactured using the light-emitting device described in embodiments 1 and 2, is based on Fig. 4A and Fig. 4B described. It should be noted that Fig. 4A is a top view of the light-emitting device and Fig. 4B a cross-sectional view along lines AB and CD of the Fig. 4A. This light-emitting device includes a driver circuit section (a source line driver circuit) 601, a pixel section 602, and a driver circuit section (a gate line driver circuit) 603, which control the light emission of a light-emitting device and are represented by dashed lines. A reference numeral 604 denotes a sealing substrate; 605, a sealing material; and 607, a space enclosed by the sealing material 605.

[0132] A connecting line 608 is a line for transmitting signals input to the source line driver circuit 601 and the gate line driver circuit 603, and for receiving signals, such as a video signal, a clock signal, a start signal, and a reset signal, from a flexible printed circuit (FPC) 609 serving as an external input terminal. Although only the FPC is shown here, a printed circuit board (PWB) may be attached to the FPC. The term "light-emitting device" in this description includes not only the light-emitting device itself, but also the light-emitting device that is connected to the FPC or the PWB.

[0133] Next, a cross-sectional structure will be created based on... Fig. 4B is described. The driver circuit sections and the pixel section are formed on an element substrate 610. Here, the source line driver circuit 601, which is a driver circuit section, and a pixel in the pixel section 602 are shown.

[0134] The element substrate 610 can be a substrate containing glass, quartz, an organic resin, a metal, an alloy or a semiconductor, or a plastic substrate formed from fiber reinforced plastic (FRP), polyvinyl fluoride (PVF), polyester or acrylic resin.

[0135] The structure of the transistors used in pixels and driver circuits is not particularly restricted. For example, inverted-staggered or staggered transistors can be used. Furthermore, top-gate or bottom-gate transistors can be used. The semiconductor material used for the transistors is also not particularly restricted; for example, silicon, germanium, silicon carbide, gallium nitride, or the like can be used. Alternatively, an oxide semiconductor containing at least one of indium, gallium, and zinc, such as an indium-gallium-zinc (InGa-Zn)-based metal oxide, can be used.

[0136] There is no particular restriction regarding the crystallinity of a semiconductor material used for the transistors, and an amorphous semiconductor or a semiconductor with crystallinity (a microcrystalline semiconductor, a polycrystalline semiconductor, a single-crystal semiconductor, or a semiconductor that partially comprises crystalline regions) can be used. Preferably, a semiconductor with crystallinity is used, in which case a deterioration of the transistor properties can be suppressed.

[0137] Here, an oxide semiconductor is preferably used for semiconductor devices, such as the transistors provided in the pixels and driver circuits, and transistors used for touch sensors, which will be described later, and the like. In particular, an oxide semiconductor with a larger band gap than silicon is preferably used. When an oxide semiconductor with a larger band gap than silicon is used, the reverse current of the transistors can be reduced.

[0138] The oxide semiconductor preferably contains at least indium (In) or zinc (Zn). More preferably, the oxide semiconductor contains an oxide formed by an In-M-Zn-based oxide (M being a metal, such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce or Hf).

[0139] An oxide semiconductor that can be used in an embodiment of the present invention is described below.

[0140] An oxide semiconductor (metal oxide) is divided into a single-crystal oxide semiconductor and a non-single-crystal oxide semiconductor. Examples of a non-single-crystal oxide semiconductor include a c-axis aligned crystalline oxide semiconductor (CAAC-OS), a polycrystalline oxide semiconductor, a nanocrystalline oxide semiconductor (nc-OS), an amorphous-like oxide semiconductor (a-like OS), and an amorphous oxide semiconductor.

[0141] The CAAC-OS exhibits an orientation with respect to the c-axis, its nanocrystals are connected in the direction of the ab-plane, and its crystal structure exhibits distortion. It should be noted that distortion refers to a section where the direction of a lattice arrangement changes between a region with a uniform lattice arrangement and another region with a uniform lattice arrangement in a region where the nanocrystals are connected.

[0142] The shape of the nanocrystal is generally hexagonal; however, the shape is not always a regular hexagon and is, in some cases, irregular. Pentagonal, heptagonal, and similar lattice arrangements are sometimes present within the distortion. It should be noted that even near the distortion, it is difficult to observe a distinct grain boundary in the CAAC-OS. This means that the lattice arrangement is distorted, and thus the formation of a grain boundary is suppressed. This is because the CAAC-OS can tolerate distortion thanks to a low density of the oxygen atom arrangement towards the ab plane, a change in the interatomic bond distance through the substitution of a metallic element, and similar factors.

[0143] There is a tendency for CAAC-OS to exhibit a layered crystal structure (also referred to as a multilayer structure) in which a layer containing indium and oxygen (hereinafter referred to as the In layer) and a layer containing the element M, zinc, and oxygen (hereinafter referred to as the (M, Zn) layer) are arranged one above the other. It should be noted that indium and the element M can be interchanged, and that if the element M in the (M, Zn) layer is replaced by indium, the layer can also be referred to as the (In, M, Zn) layer. Conversely, if the indium in the In layer is replaced by the element M, the layer can also be referred to as the (In, M) layer.

[0144] CAAC-OS is an oxide semiconductor with high crystallinity. In contrast, reductions in electron mobility due to grain boundaries are less likely in CAAC-OS, as distinct grain boundaries are difficult to observe. The ingress of impurities, the formation of defects, or similar factors could reduce the crystallinity of an oxide semiconductor. This means that CAAC-OS is an oxide semiconductor that can tolerate small amounts of impurities and defects (e.g., oxygen vacancies, also known as Vx). O Therefore, an oxide semiconductor containing CAAC-OS is physically stable. Consequently, the oxide semiconductor containing CAAC-OS is heat-resistant and exhibits high reliability.

[0145] In the nc-OS, a microscopic region (e.g., a region greater than or equal to 1 nm and less than or equal to 10 nm, in particular a region greater than or equal to 1 nm and less than or equal to 3 nm) exhibits a regular atomic arrangement. There is no regularity in the crystal orientation between different nanocrystals in the nc-OS. Therefore, no orientation of the entire film is observed. Consequently, in some cases, the nc-OS cannot be distinguished from an a-like OS or an amorphous oxide semiconductor using a specific analytical method.

[0146] It should be noted that indium gallium zinc oxide (hereinafter IGZO), an oxide semiconductor containing indium, gallium, and zinc, exhibits a stable structure in some cases when formed from the nanocrystals described above. In particular, IGZO crystals tend not to grow in air, and therefore a stable structure is obtained when IGZO is formed from smaller crystals (e.g., the nanocrystals described above) rather than from larger crystals (here, crystals several millimeters or several centimeters in size).

[0147] The a-like oxide semiconductor (A-OS) has a structure intermediate between that of the non-crystalline oxide semiconductor (NC-OS) and the amorphous oxide semiconductor. The A-like OS exhibits a cavity or low-density region. This means that the A-like OS has lower crystallinity compared to the NC-OS and the CAAC-OS.

[0148] An oxide semiconductor can have different structures that exhibit various different properties. Two or more of the amorphous oxide semiconductor, the polycrystalline oxide semiconductor, the a-like oxide semiconductor, the nc-oxide semiconductor, and the CAAC-oxide semiconductor can be included in an oxide semiconductor of an embodiment of the present invention.

[0149] A cloud-aligned composite (CAC) OS can be used as an oxide semiconductor in addition to the materials mentioned above.

[0150] A CAC-OS exhibits a conductive function in one part of the material and an insulating function in another part; as a whole, the CAC-OS functions like a semiconductor. It should be noted that when the CAC-OS is used in a semiconductor layer of a transistor, the conductive function allows electrons (or holes) to flow, acting as charge carriers, while the insulating function prevents electrons from flowing, also acting as charge carriers. Due to the complementary action of the conductive and insulating functions, the CAC-OS can exhibit a switching (on / off) function. Within the CAC-OS, a separation of these functions can maximize each function.

[0151] Furthermore, the CAC-OS comprises conductive and insulating regions. The conductive regions exhibit the conductive function described above, and the insulating regions exhibit the insulating function described above. In some cases, the conductive and insulating regions are separated on the nanoparticle scale within the material. In some cases, the conductive and insulating regions are also unevenly distributed within the material. Additionally, in some cases, the conductive regions are observed to be cloud-coupled, with indistinct boundaries.

[0152] Furthermore, in some cases in the CAC-OS, the conductive regions and the insulating regions each have a size greater than or equal to 0.5 nm and less than or equal to 10 nm, preferably greater than or equal to 0.5 nm and less than or equal to 3 nm, and they are dispersed in the material.

[0153] Furthermore, the CAC-OS contains components with different band gaps. For example, the CAC-OS includes a component with a large band gap due to the insulating region and a component with a small band gap due to the conducting region. In this structure, when charge carriers flow, they predominantly flow in the component with the small band gap. The component with the small band gap also complements the component with the large band gap, and charge carriers also flow in the component with the large band gap in conjunction with the component with the small band gap. Consequently, when the CAC-OS described above, or a CAC metal oxide, is used in a channel-forming region of a transistor, high current-driving capability in a forward-biased state of the transistor, i.e., high forward current and high field-effect mobility, can be obtained.

[0154] In other words, the CAC-OS can be described as a matrix composite or metal-matrix composite.

[0155] The use of the oxide semiconductor materials described above for the semiconductor layer makes it possible to provide a highly reliable transistor in which changes in electrical properties are suppressed.

[0156] Thanks to the transistor's low reverse current, a charge accumulated in a capacitor via a transistor incorporating the semiconductor layer described above can be retained for a long time. When such a transistor is used in a pixel, the operation of a driver circuit can be interrupted while maintaining a grayscale level of the image displayed in each area of ​​the screen. As a result, a very low-power electronic device can be obtained.

[0157] For stable properties or similar characteristics of the transistor, a base film is preferably provided. The base film can be configured as a single-layer structure or a multi-layer structure using an inorganic insulating film, such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a silicon nitride oxide film. The base film can be formed by a sputtering process, a chemical vapor deposition (CVD) process (e.g., a plasma CVD process, a thermal CVD process, or a metal-organic CVD (MOCVD) process), an atomic layer deposition (ALD) process, a coating process, a printing process, or the like. It should be noted that the base film does not necessarily have to be provided.

[0158] It should be noted that a FET 623 is represented as a transistor formed in the driver circuit section 601. Furthermore, the driver circuit can be formed using one of various circuits, such as a CMOS circuit, a PMOS circuit, or an NMOS circuit. Although this embodiment describes a driver-integrated type in which the driver circuit is formed on top of the substrate, the driver circuit need not necessarily be formed on top of the substrate and can be formed outside of it.

[0159] The pixel section 602 comprises a plurality of pixels, each containing a switching FET 611, a current-controlling FET 612, and an anode 613 electrically connected to a drain of the current-controlling FET 612. An embodiment of the present invention is not limited to this structure. The pixel section 602 can include three or more FETs and a capacitor in combination.

[0160] It should be noted that an insulator 614 is formed to cover an end section of the anode 613. Here, the insulator 614 can be formed using a positive photosensitive acrylic.

[0161] To improve the coverage with an EL layer or the like, which is formed subsequently, the insulator 614 is designed to have a curved surface with a curvature at its upper or lower end section. For example, if a positive photosensitive acrylic is used as the material of the insulator 614, preferably only the upper end section of the insulator 614 has a curved surface with a radius of curvature (0.2 µm to 3 µm). Either a negative photosensitive resin or a positive photosensitive resin can be used as the insulator 614.

[0162] An EL layer 616 and a cathode 617 are formed above the anode 613. Preferably, a material with a high work function is used for the anode 613. 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 zinc film, a platinum film, or the like; a layer arrangement of a titanium nitride film and a film containing aluminum as its main component; a layer arrangement of three layers, namely a titanium nitride film, a film containing aluminum as its main component, and a titanium nitride film; or the like may be used. The multi-layer structure enables low conduction resistance and good ohmic contact, as well as functioning as a cathode.

[0163] The EL layer 616 is formed by one of several processes, such as an evaporation process using an evaporation mask, an inkjet process, and a rotational coating process. The EL layer 616 has the structure described in embodiments 1 and 2. A low-molecular-weight compound or a high-molecular-weight compound (including an oligomer or a dendrimer) can be used as an additional material incorporated into the EL layer 616.

[0164] The material used for the cathode 617, which is formed above the EL layer 616, is preferably a material with a low work function (e.g., Al, Mg, Li, Ca, or an alloy or compound thereof, such as MgAg, MgIn, or AlLi). In cases where light generated in the EL layer 616 is passed through the cathode 617, a layer arrangement consisting of a thin metal film and a transparent conductive film (e.g., ITO, indium oxide containing 2 wt.% to 20 wt.% zinc oxide, indium tin oxide containing silicon, or zinc oxide (ZnO)) is preferably used for the cathode 617.

[0165] It should be noted that the light-emitting device is configured with the anode 613, the EL layer 616, and the cathode 617. The light-emitting device is the same as described in embodiments 1 and 2. In the light-emitting device of this embodiment, the pixel section, which includes a plurality of light-emitting devices, can include both the light-emitting device described in embodiments 1 and 2 and a light-emitting device with a different structure.

[0166] The sealing substrate 604 is attached to the element substrate 610 by means of the sealing material 605, so that a light-emitting device 618 is provided in the space 607, which is surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. The space 607 can be filled with a filler or can be filled with an inert gas (such as nitrogen or argon) or the sealing material. It is preferred that the sealing substrate be provided with a recessed section and that a desiccant be provided in the recessed section, in which case deterioration due to the influence of moisture can be suppressed.

[0167] An epoxy-based resin or a glass frit is preferably used for the sealing material 605. Preferably, such a material should allow as little moisture or oxygen to pass through as possible. A glass substrate, a quartz substrate, or a plastic substrate made of fiber-reinforced plastic (FRP), polyvinyl fluoride (PVF), polyester, or acrylic can be used as the sealing substrate 604.

[0168] Although in Fig. 4A and Fig. Not shown in Figure 4B, a protective film can be provided over the cathode. The protective film can be an organic resin film or an inorganic insulating film. The protective film can be configured to cover an exposed portion of the sealing material 605. Alternatively, the protective film can be provided to cover the surfaces and side faces of the substrate pair and exposed side faces of a sealing layer, an insulating layer, and the like.

[0169] The protective film can be formed using a material that does not easily allow contaminants, such as water, to pass through. This effectively prevents the diffusion of contaminants, such as water, from the outside into the inside.

[0170] The material for the protective film can be an oxide, a nitride, a fluoride, a sulfide, a ternary compound, a metal, a polymer or the like. For example, the material may contain aluminum oxide, hafnium oxide, hafnium silicate, lanthanum oxide, silicon oxide, strontium titanate, tantalum oxide, titanium oxide, zinc oxide, niobium oxide, zirconium oxide, tin oxide, yttrium oxide, cerium oxide, scandium oxide, erbium oxide, vanadium oxide, indium oxide, aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride, gallium nitride, a titanium and aluminum nitride, a titanium and aluminum oxide, an aluminum and zinc oxide, a manganese and zinc sulfide, a cerium and strontium sulfide, an erbium and aluminum oxide, an yttrium and zirconium oxide, or the like.

[0171] The protective film is preferably formed using a deposition process with favorable step coverage. One such process is atomic layer deposition (ALD). A material suitable for ALD deposition is preferably used for the protective film. A dense protective film with reduced defects, such as cracks or small holes, or with a uniform thickness can be formed using an ALD process. Furthermore, damage to a process element during the formation of the protective film can be reduced.

[0172] An ALD process can form a uniform protective film with few defects, even on a surface with a complex, irregular shape or on the top, side, and bottom surfaces of a touchscreen.

[0173] As described above, the light-emitting device can be obtained using the light-emitting device described in embodiments 1 and 2.

[0174] The light-emitting device of this embodiment is manufactured using the light-emitting device described in embodiments 1 and 2, and can therefore have advantageous properties. Since the light-emitting device described in embodiments 1 and 2 has a particularly long service life, the light-emitting device can exhibit high reliability. Since the light-emitting device used in embodiments 1 and 2 has high emission efficiency, the light-emitting device can achieve low power consumption.

[0175] Fig. 5A and Fig. 5B each represent an example of a light-emitting device in which a full-color display is achieved by forming a light-emitting device that has white light emission and using color layers (color filters) and the like. Fig. 5A represents 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 section 1042, a pixel section 1040, a driver circuit section 1041, anodes 1024W, 1024R, 1024G and 1024B of light-emitting devices, a partition 1025, an EL layer 1028, a cathode 1029 of the light-emitting devices, a sealing substrate 1031, a sealing material 1032 and the like.

[0176] In Fig. 5A consists of color layers (a red color layer 1034R, a green color layer 1034G, and a blue color layer 1034B) on a transparent base material 1033. A black matrix 1035 can also be provided. The transparent base material 1033, which is coated with the color layers and the black matrix, is aligned with and attached to the substrate 1001. It should be noted that the color layers and the black matrix 1035 are covered with a protective layer 1036. Fig. 5A The light emitted by one part of the light-emitting layer does not pass through the color layers, while the light emitted by the other part of the light-emitting layer does pass through the color layers. The light that does not pass through the color layers is white, and the light that does pass through one of the color layers is red, green, or blue; therefore, an image can be displayed using pixels of the four colors.

[0177] Fig. Figure 5B provides an example in which the color layers (the red color layer 1034R, the green color layer 1034G, and the blue color layer 1034B) are provided between the gate insulating film 1003 and the first intermediate insulating film 1020. As with the structure, the color layers can be provided between the substrate 1001 and the sealing substrate 1031.

[0178] The light-emitting device described above is a light-emitting device with a structure in which light is extracted from the side of the substrate 1001 where FETs are formed (bottom-emission structure); however, it can be a light-emitting device with a structure in which light is extracted from the side of the sealing substrate 1031 (top-emission structure). Fig. Figure 6 shows a cross-sectional view of a light-emitting device with a top-emission structure. In this case, an opaque substrate can be used as substrate 1001. The process up to the step of forming a connecting electrode that links the FET and the anode of the light-emitting device is carried out in a manner similar to that of the light-emitting device with a bottom-emission structure. Subsequently, a third interlayer insulating film 1037 is formed to cover an electrode 1022. This insulating film can have a flattening function. The third interlayer insulating film 1037 can be formed using a material similar to that of the second interlayer insulating film or, alternatively, using another known material.

[0179] The anodes 1024W, 1024R, 1024G and 1024B of the light-emitting devices are ternary, although each is an anode, they can also be configured as a cathode. In the case of a Fig. In the light-emitting device with a top-emission structure shown in Figure 6, the anodes are preferably also reflective electrodes. The EL layer 1028 is designed to have a structure similar to that of the EL layer 103 described in embodiments 1 and 2, and in which white light emission can be obtained.

[0180] In the event of an Fig. In the top-emission structure shown in Figure 6, sealing can be carried out using 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 matrix 1035, which is 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 matrix can be covered with the cover layer 1036. It should be noted that a translucent substrate is used as the sealing substrate 1031.Although an example is shown here in which a full-color display is performed using four colors, namely red, green, blue and white, there is no particular restriction, and a full-color display can be performed using four colors, namely red, yellow, green and blue, or using three colors, namely red, green and blue.

[0181] In a light-emitting device with a top-emission structure, a microcavity structure can be advantageously employed. A light-emitting device with a microcavity structure is designed using a reflective electrode as the anode and a semi-transparent, semi-reflective electrode as the cathode. The light-emitting device with a microcavity structure includes at least one EL layer between the reflective electrode and the semi-transparent, semi-reflective electrode, which comprises at least one light-emitting layer serving as the light-emitting region.

[0182] It should be noted that the reflective electrode has a reflectance for visible light of 40% to 100%, preferably 70% to 100%, and a resistivity of 1 × 10 -2The electrode has a resistivity of Ωcm or lower. Furthermore, the semi-transparent and semi-reflective electrode has a visible light reflectance of 20% to 80%, preferably 40% to 70%, and a resistivity of 1 × 10⁻⁶ Ωcm. -2 Ωcm or lower.

[0183] Light emitted by the light-emitting layer contained within the EL layer is reflected by the reflecting electrode and the semi-transparent and semi-reflective electrode and brought into resonance.

[0184] In the light-emitting device, the optical path length between the reflecting electrode and the semi-transparent / semi-reflective electrode can be changed by altering the thicknesses of the transparent conductive film, the composite material, the charge carrier transport material, and the like. In this way, light with a wavelength that resonates between the reflecting electrode and the semi-transparent / semi-reflective electrode can be amplified, while light with a wavelength that does not resonate between them can be attenuated.

[0185] It should be noted that light reflected back from the reflecting electrode (first reflected light) significantly interferes with the light entering the semi-transparent, semi-reflective electrode directly from the light-emitting layer (first incident light). For this reason, the optical path length between the reflecting electrode and the light-emitting layer is preferably set to (2n-1)λ / 4 (n is a natural number of 1 or greater, and λ is a wavelength of the color to be amplified). By adjusting the optical path length, the phases of the first reflected light and the first incident light can be aligned, and the light emitted by the light-emitting layer can be further amplified.

[0186] It should be noted that in the above structure, the EL layer can comprise a plurality of light-emitting layers or a single light-emitting layer. The light-emitting tandem device described above can be combined with a plurality of EL layers; for example, a light-emitting device can have a structure in which a plurality of EL layers are provided, a charge-generating layer is provided between the EL layers, and each EL layer comprises a plurality of light-emitting layers or a single light-emitting layer.

[0187] The microcavity structure allows for increased emission intensity at a specific wavelength in the forward direction, thereby reducing power consumption. It should be noted that in the case of a light-emitting device displaying images with subpixels of four colors—red, yellow, green, and blue—the device can exhibit advantageous properties, as the luminance can be increased thanks to the yellow light emission, and each subpixel can have a microcavity structure suitable for the wavelengths of its corresponding color.

[0188] The light-emitting device of this embodiment is manufactured using the light-emitting device described in embodiments 1 and 2, and can therefore have advantageous properties. Since the light-emitting device described in embodiments 1 and 2 has a particularly long service life, the light-emitting device can exhibit high reliability. Since the light-emitting device used in embodiments 1 and 2 has high emission efficiency, the light-emitting device can achieve low power consumption.

[0189] The light-emitting active matrix device has been described above, whereas a light-emitting passive matrix device is described below. Fig. 7A and Fig. Figure 7B represents a light-emitting passive matrix device produced using the present invention. It should be noted that Fig. 7A is a perspective view of the light-emitting device and Fig. 7B a cross-sectional view along line XY in Fig. 7A is. In Fig. 7A and Fig. 7B, an EL layer 955 is provided between an electrode 952 and an electrode 956 over a substrate 951. An end section of the electrode 952 is covered with an insulating layer 953. A separating layer 954 is provided over the insulating layer 953. The side walls of the separating layer 954 are inclined such that the distance between the two side walls gradually decreases towards the surface of the substrate. In other words, a cross-section along the short side of the separating layer 954 is trapezoidal, and the lower side (a side of the trapezoid that is parallel to the surface of the insulating layer 953 and in contact with the insulating layer 953) is shorter than the upper side (a side of the trapezoid that is parallel to the surface of the insulating layer 953 and not in contact with the insulating layer 953).The separating layer 954 provided in this way can prevent defects in the light-emitting device due to static electricity or other factors. The passive matrix light-emitting device also includes the light-emitting device described in embodiments 1 and 2; thus, the light-emitting device can exhibit high reliability or low power consumption.

[0190] Since many microfine light-emitting devices in a matrix can be separately controlled in the light-emitting device described above, the light-emitting device can be used appropriately as a display device for showing images.

[0191] This embodiment can be freely combined with any of the other embodiments. (Version 4)

[0192] In this embodiment, an example in which the light-emitting device described in embodiments 1 and 2 is used for a lighting device is illustrated by means of Fig. 8A and Fig. 8B described. Fig. Figure 8B is a top view of the lighting device, and Fig. 8A is a cross-sectional view along the line ef in Fig. 8B.

[0193] In the lighting device of this embodiment, an anode 401 is formed above a substrate 400, which serves as a support and has a light-transmitting property. The anode 401 corresponds to the anode 101 of embodiment 2. When light is extracted via the side of the anode 401, the anode 401 is formed using a material with a light-transmitting property.

[0194] A contact point (pad) 412 for applying a voltage to a cathode 404 is formed above the substrate 400.

[0195] An EL layer 403 is formed above the anode 401. The structure of the EL layer 403 corresponds, for example, to the structure of the EL layer 103 of embodiments 1 and 2, or to the structure in which the light-emitting units 511 and 512 and the charge-generating layer 513 are combined. Reference can be made to the descriptions regarding the structure.

[0196] The cathode 404 is configured to cover the EL layer 403. The cathode 404 corresponds to the cathode 102 of embodiment 2. The cathode 404 is formed using a material with a high reflectivity when light is extracted via the side of the anode 401. The cathode 404 is connected to the contact point 412, thereby applying a voltage.

[0197] As described above, the lighting device described in this embodiment comprises a light-emitting device including the anode 401, the EL layer 403, and the cathode 404. Since the light-emitting device is a light-emitting device with high emission efficiency, the lighting device of this embodiment can be a low-power lighting device.

[0198] The substrate 400, which is provided with a light-emitting device with the aforementioned structure, is attached to a sealing substrate 407 using sealing materials 405 and 406, and a seal is applied, thereby completing the lighting device. It is possible to use only the sealing material 405 or the sealing material 406. The inner sealing material 406 (not in Fig. (shown in 8B) can be mixed with a desiccant, which allows for the adsorption of moisture and leads to increased reliability.

[0199] If parts of the contact point 412 and the anode 401 extend beyond the sealing materials 405 and 406, these extended parts can serve as external input terminals. An IC chip 420, mounted with a converter or the like, can be provided via these external input terminals.

[0200] The lighting device described in this embodiment comprises, as the EL element, the light-emitting device described in embodiments 1 and 2; thus, the light-emitting device can exhibit high reliability. Furthermore, the light-emitting device can consume less power. (Version 5)

[0201] This embodiment describes examples of electronic devices, each incorporating the light-emitting device described in embodiments 1 and 2. The light-emitting device described in embodiments 1 and 2 exhibits a long lifetime and high reliability. As a result, the electronic devices described in this embodiment can each incorporate a highly reliable light-emitting section.

[0202] Examples of the electronic device incorporating the aforementioned light-emitting device include television sets (also called TVs or television receivers), computer monitors and the like, digital cameras, digital video cameras, digital photo frames, mobile phones (also called cell phones or mobile phone devices), portable game consoles, portable information terminals, audio playback devices, and large gaming machines, such as pinball machines. Specific examples of these electronic devices are shown below.

[0203] Fig. Figure 9A represents an example of a television set. In this television set, a display section 7103 is installed in a housing 7101. Here, the housing 7101 is supported by a stand 7105. Images can be displayed on the display section 7103, and the light-emitting devices described in embodiments 1 and 2 are arranged in a matrix within the display section 7103.

[0204] The television can be operated using a control switch on the housing 7101 or a separate remote control 7110. The remote control 7110's control buttons 7109 allow control of television channels and volume, as well as control of images displayed on the display section 7103. Furthermore, the remote control 7110 can be equipped with a display section 7107 for displaying data output by the remote control 7110.

[0205] It should be noted that the television set is equipped with a receiver, a modem, and the like. Using the receiver, general television broadcasts can be received. Furthermore, if the television set is connected to a communication network via the modem, either wirelessly or via a fixed connection, unidirectional (from a sender to a receiver) or bidirectional (between a sender and a receiver or between receivers) data communication can take place.

[0206] Fig. 9B1 represents a computer comprising a main part 7201, a housing 7202, a display section 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, and the like. It should be noted that this computer is manufactured in the display section 7203 by using the light-emitting devices described in embodiments 1 and 2, arranged in a matrix. The Fig. The computer shown in 9B1 can be in Fig. exhibit the structure shown in 9B2. One in Fig. The computer shown in Figure 9B2 is equipped with a second display section 7210 in place of the keyboard 7204 and the pointing device 7206. The second display section 7210 is a touchscreen, and input can be performed by touching the input display on the second display section 7210 with a finger or an associated stylus. The second display section 7210 can also display images other than the input display. The display section 7203 can also be a touchscreen. Connecting the two screens by means of a hinge prevents problems such as cracking or damage to the screens when storing or transporting the computer.

[0207] Fig. Figure 9C presents an example of a portable terminal device. A mobile phone is provided with a display section 7402, which is built into a housing 7401, control buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like. It should be noted that the mobile phone includes the display section 7402, which contains the light-emitting devices described in embodiments 1 and 2 and arranged in a matrix.

[0208] If the display section 7402 of the portable device is in Fig. When 9C is touched with a finger or similar object, data can be entered into the portable device. In this case, operations such as making calls and writing emails can be performed by touching the display section 7402 with a finger or similar object.

[0209] The 7402 display section has three main screen modes. The first mode is a display mode, primarily for showing images. The second mode is an input mode, primarily for entering information, such as text. The third mode is a combined display and input mode.

[0210] For example, when making calls or writing emails, a text input mode is primarily selected for entering text into display section 7402, allowing the text displayed on the screen to be entered. In this case, it is preferred that a keyboard or number keys are displayed across almost the entire screen of display section 7402.

[0211] If a detection device incorporating a sensor for detecting inclination, such as a gyroscope or accelerometer, is provided within the portable terminal, a display on the screen of display section 7402 can be automatically changed in its direction by determining the orientation of the portable terminal (depending on whether the portable terminal is positioned horizontally or vertically).

[0212] The screen modes are switched by touching the display section 7402 or by operating the control knobs 7403 on the housing 7401. Alternatively, the screen modes can be switched depending on the type of image displayed on the display section 7402. For example, if a signal from an image displayed on the display section is a data signal from a moving image, the screen mode switches to display mode. If the signal is a data signal from text, the screen mode switches to input mode.

[0213] Furthermore, if no input is made by touching the display section 7402 for a certain period of time in input mode, while a signal detected by an optical sensor in the display section 7402 is being detected, the screen mode can be controlled such that it switches from input mode to display mode.

[0214] The display section 7402 can also function as an image sensor. For example, when the display section 7402 is touched with a palm or finger, an image of the handprint, fingerprint, or the like is captured, enabling personal authentication. Furthermore, by providing a backlight or a scanning light source emitting near-infrared light in the display section, an image of a finger vein, palm vein, or the like can be captured.

[0215] It should be noted that the structure described in this embodiment can be appropriately combined with one of the structures described in embodiments 1 to 4.

[0216] As described above, the application range of the light-emitting device described in embodiments 1 and 2 is extensive, allowing it to be applied to electronic devices in various fields. By using the light-emitting device described in embodiments 1 and 2, a highly reliable electronic device can be obtained.

[0217] Fig. 10A is a schematic view that represents an example of a cleaning robot.

[0218] A 5100 cleaning robot includes a display 5101 on its top, multiple cameras 5102 on its side, a brush 5103, and control buttons 5104. Although not shown, the underside of the 5100 cleaning robot is equipped with a wheel, an inlet, and similar features. The 5100 cleaning robot also includes various sensors, such as an infrared sensor, an ultrasonic sensor, an accelerometer, a piezoelectric sensor, an optical sensor, and a gyroscope. The 5100 cleaning robot features a wireless communication system.

[0219] The cleaning robot 5100 is self-driving, captures dust 5120 and vacuums up the dust through the inlet opening provided on the underside.

[0220] The 5100 cleaning robot can determine whether an obstacle, such as a wall, piece of furniture, or step, is present by analyzing images captured by the 5102 cameras. If the 5100 cleaning robot detects an object that could become entangled in the 5103 brush (e.g., a wire) by analyzing an image, the rotation of the 5103 brush can be stopped.

[0221] The 5101 display can show the remaining battery power, the amount of dust collected, and similar information. The 5101 display can also show the route the 5100 cleaning robot has traveled. The 5101 display may be a touchscreen, and the 5104 control buttons may be integrated into the 5101 display.

[0222] The 5100 cleaning robot can communicate with a portable electronic device 5140, such as a smartphone. The portable electronic device 5140 can display images captured by the 5102 cameras. Therefore, the owner of the 5100 cleaning robot can monitor their room even when they are not at home. The owner can also check the display 5101 using the portable electronic device 5140, such as a smartphone.

[0223] The light-emitting device of an embodiment of the present invention can be used for the display 5101.

[0224] A robot 2100, which is in Fig. Figure 10B includes an arithmetic device 2110, an illuminance sensor 2101, a microphone 2102, an upper camera 2103, a loudspeaker 2104, a display 2105, a lower camera 2106, an obstacle sensor 2107 and a movement mechanism 2108.

[0225] The microphone 2102 has a function to capture a user's voice, ambient noise, and the like. The speaker 2104 also has a function to output a sound. The robot 2100 can communicate with a user using the microphone 2102 and the speaker 2104.

[0226] The Display 2105 has a function to display various types of information. The Robot 2100 can display user-requested information on the Display 2105. The Display 2105 can be equipped with a touchscreen. Furthermore, the Display 2105 can be a detachable information terminal, in which case charging and data communication can occur when the Display 2105 is positioned at the predetermined location of the Robot 2100.

[0227] The upper camera 2103 and the lower camera 2106 each have a function for capturing an image of the robot 2100's surroundings. The obstacle sensor 2107 can detect an obstacle in the direction in which the robot 2100 is moving forward with the movement mechanism 2108. The robot 2100 can move safely by perceiving its surroundings with the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107. The light-emitting device of an embodiment of the present invention can be used for the display 2105.

[0228] Fig. Figure 10C provides an example of a spectacle-like display. The spectacle-like display includes, for example, a housing 5000, a display section 5001, a speaker 5003, an LED lamp 5004, a connection connector 5006, a sensor 5007 (a sensor with a function for measuring force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, electrical energy, radiation, flow rate, humidity, gradient, vibration, odor, or infrared beam), a microphone 5008, a display section 5002, a support 5012, and an earpiece 5013.

[0229] The light-emitting device of an embodiment of the present invention can be used for the display section 5001 and the display section 5002.

[0230] Fig. Figure 11 presents an example in which the light-emitting device described in embodiments 1 and 2 is used for a table lamp, which is a lighting device. The table lamp in Fig. 11 includes a housing 2001 and a light source 2002, and the lighting device described in embodiment 3 can be used for the light source 2002.

[0231] Fig. Figure 12 presents an example in which the light-emitting device described in embodiments 1 and 2 is used for an interior lighting device 3001. Since the light-emitting device described in embodiments 1 and 2 has high reliability, the lighting device can also have high reliability. Furthermore, since the light-emitting device described in embodiments 1 and 2 can have a large area, it can be used for a lighting device with a large area. Furthermore, since the light-emitting device described in embodiments 1 and 2 is thin, it can be used for a lighting device with a reduced thickness.

[0232] The light-emitting device described in embodiments 1 and 2 can also be used for a car windshield or car dashboard. Fig. Figure 13 represents an embodiment in which the light-emitting devices described in embodiments 1 and 2 are used for a car windshield and a car dashboard. Display areas 5200 to 5203 each include the light-emitting device described in embodiments 1 and 2.

[0233] Display areas 5200 and 5201 are display devices provided in the car windshield and in which light-emitting devices are incorporated, each of which has been described in embodiments 1 and 2. The light-emitting devices described in embodiments 1 and 2 can be configured as a so-called transparent display device through which the opposite side can be seen, if it includes an anode and a cathode consisting of electrodes with a light-transmitting property. Such transparent display devices can even be provided in the car windshield without obstructing the view.In the case where a driver transistor or the like is provided, a transistor with a light transmittance property is preferably used, such as an organic transistor containing an organic semiconductor material or a transistor containing an oxide semiconductor.

[0234] A display device, including the light-emitting device described in embodiments 1 and 2, is provided in display area 5002 in a pillar section. Display area 5202 can compensate for the view obstructed by the pillar by displaying an image captured by an imaging unit provided in the vehicle body. Display area 5203, provided in a part of the instrument panel, can likewise compensate for the view obstructed by the vehicle body by displaying an image captured by an imaging unit provided outside the vehicle. Therefore, blind spots can be eliminated to increase safety. Images that compensate for the areas a driver cannot see allow the driver to easily and conveniently confirm safety.

[0235] Display area 5203 can provide various types of information, including navigation data, a speedometer, a tachometer, an odometer, a fuel gauge, a gear indicator, climate control settings, and the like. The content or layout of the display can be freely modified by the user as appropriate. It should be noted that such information can also be displayed on display areas 5200 to 5203. Display areas 5200 to 5203 can also be used as lighting devices.

[0236] Fig. 14A and Fig. 14B represents a foldable, portable information terminal 5150. The foldable, portable information terminal 5150 includes a housing 5151, a display area 5152, and a bending section 5153. Fig. Figure 14A represents the portable information terminal 5150, which is unfolded. Fig. Figure 14B depicts the portable information terminal 5150 in its folded state. Despite its large display area 5152, the portable information terminal 5150 is compact and highly portable when folded.

[0237] The display area 5152 can be folded twice with the bending section 5153. The bending section 5153 comprises a flexible element and a plurality of support elements. When the display area is folded, the flexible element expands and the bending section 5153 has a radius of curvature greater than or equal to 2 mm, preferably greater than or equal to 3 mm.

[0238] It should be noted that the display area 5152 can be a touchscreen (an input / output device) that includes a touch sensor (an input device). The light-emitting device of an embodiment of the present invention can be used for the display area 5152.

[0239] Fig. 15A to 15C represent a foldable, portable information terminal 9310. Fig. Figure 15A represents the portable information terminal 9310, which is unfolded. Fig. Figure 15B depicts the portable information terminal 9310 during unfolding or folding. Fig. Figure 15C depicts the 9310 portable information terminal in its folded state. When unfolded, the 9310 portable information terminal offers excellent searchability due to its large, seamless display area.

[0240] A display panel 9311 is supported by three housings 9315, which are connected to one another by hinges 9313. It should be noted that the display panel 9311 can be a touchscreen (an input / output device) that includes a touch sensor (an input device). The shape of the portable information terminal 9310 can be reversibly changed from the unfolded state to the folded state by folding the display panel 9311 at the hinges 9313 between two housings 9315. The light-emitting device of an embodiment of the present invention can be used for the display panel 9311. [Example 1]

[0241] This example describes a light-emitting device 1 of an embodiment of the present invention. Structural formulas of organic compounds used for the light-emitting device 1 are shown below. (Method for manufacturing the light-emitting device 1)

[0242] First, indium tin oxide containing silicon oxide (ITSO) was deposited onto a glass substrate by sputtering to form anode 101. The thickness of anode 101 was 70 nm, and the electrode area was 2 mm × 2 mm.

[0243] Next, in a pretreatment to form the light-emitting device over a substrate, a surface of the substrate was washed with water and baked at 200 °C for 1 hour, and then a UV ozone treatment was carried out for 370 seconds.

[0244] The substrate was then transferred to a vacuum evaporation unit, where the pressure was increased to approximately 10 -4 After the Pa was reduced, vacuum baking was carried out for 30 minutes at 170 °C in a heating chamber of the vacuum evaporation device, and then the substrate was cooled for approximately 30 minutes.

[0245] Next, the substrate, which was equipped with the anode 101, was attached to a substrate holder provided in the vacuum evaporation apparatus such that the side on which the anode 101 was formed faced downwards. Then, N,N-Bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), represented by structural formula (i), and NDP-9 (manufactured by Analysis Atelier Corporation, material serial number 1S20170124) were deposited onto the anode 101 by co-evaporation using a resistance heating process to a thickness of 10 nm, such that the weight ratio of BBABnf to NDP-9 was 1:0.1, thereby forming the hole injection layer 111.

[0246] Subsequently, BBABnf was deposited over the hole injection layer 111 by evaporation to a thickness of 20 nm to form the first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2), represented by structural formula (ii), was deposited by evaporation to a thickness of 10 nm to form the second hole transport layer 112-2, thus forming the hole transport layer 112. It should be noted that the second hole transport layer 112-2 also serves as an electron blocking layer.

[0247] Subsequently, 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), represented by structural formula (iii), and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02), represented by structural formula (iv), were deposited by co-evaporation to a thickness of 25 nm such that the weight ratio of αN-βNPAnth to 3,10PCA2Nbf(IV)-02 was 1:0.015, thereby forming the light-emitting layer 113.

[0248] Subsequently, 2-{4-[9,10-Di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN), represented by structural formula (v), and 8-hydroxyquinolinatolithium (abbreviation: Liq), represented by structural formula (vi), were deposited over the light-emitting layer 113 by co-evaporation to a thickness of 25 nm such that the weight ratio of ZADN to Liq was 1:0.9, thereby forming the electron transport layer 114.

[0249] After forming the electron transport layer 114, Liq was deposited by evaporation to a thickness of 1 nm to form the electron injection layer 115. Subsequently, aluminum was deposited by evaporation to a thickness of 200 nm to form the cathode 102. Thus, the light-emitting device 1 of this example was fabricated.

[0250] The structure of the light-emitting device 1 is listed in the following table. [Table 1] Lochinjektionsschicht Lochtransportschicht Licht emittierendeSchicht Elektronentransportschicht Elektroneninjektionsschicht 1 2 10 nm 20 nm 10 nm 25 nm 25 nm 1 nm LichtemittierendeVorrichtung1 BBABnf:NDP-9(1:0,1) BBABnf PCzN2 αN-βNPAnth:3,10PCANbf(IV)-02(1:0,015) ZADN:Liq(1:0,9) Liq

[0251] The HOMO levels, LUMO levels, and electron mobilities of the organic compounds used in this example are listed in the following table. The electron mobilities were measured at a field strength of 600 V / cm. [Table 2] HOMO-Niveau (eV) LUMO-Niveau (eV) Electron mobility (cm) 2 / Vs) BBABnf -5,56 - - PCzN2 -5,71 - - αN-βNPAnth -5,85 -2,74 - ZADN - -2,87 - ZADN:Liq (1:1) - - 3,1 × 10 -6

[0252] The light-emitting device was sealed using a glass substrate in a glove box containing a nitrogen atmosphere, thus preventing exposure to air (a sealing material was applied to completely enclose the element, and the sealing process included UV treatment and a heat treatment at 80 °C for 1 hour). The initial properties and reliability of the light-emitting device were then measured. It should be noted that the measurements were performed at room temperature.

[0253] Fig. Figure 16 shows the luminance-current density properties of the light-emitting device 1. Fig. Figure 17 shows the power efficiency-luminance properties of these. Fig. Figure 18 shows the luminance-voltage properties of these. Fig. Figure 19 shows the current-voltage characteristics of these. Fig. Figure 20 shows the external quantum efficiency luminance properties of these. Fig. Figure 21 shows the emission spectrum of this device. Table 3 shows the main characteristics of the light-emitting device 1 at a luminance of approximately 1000 cd / m². 2 . [Table 3] Spannung(V) Current (mA) Current density (mA / cm³) 2 ) Chromaticityx Chromaticity Power efficiency (cd / A) external quantum efficiency (%) Light-emitting device 1 4,2 0,42 10,4 0,14 0,12 10,8 11,1

[0254] Fig. 16, Fig. 17, Fig. 18, Fig. 19, Fig. 20 to Fig. Figure 21 and Table 3 show that the light-emitting device 1 of an embodiment of the present invention is a blue light-emitting device with favorable properties.

[0255] Fig. Figure 22 is a diagram showing changes in luminance with respect to operating time at a current density of 50 mA / cm². 2 shows. As in Fig.As shown in Figure 22, the luminance remains at approximately 90% of the initial luminance even after 600 hours have elapsed. This reveals that the reduction in luminance during operation over time is particularly small and that the light-emitting device 1 of an embodiment of the present invention has a very long service life.

[0256] In the decay curve of the light-emitting device 1, the luminance drops once and then increases. This means that the decay curve has a local maximum value. The light-emitting device 1, which exhibits such deterioration behavior, has a very long lifespan. [Example 2]

[0257] This example describes a light-emitting device 2 of an embodiment of the present invention. Structural formulas of organic compounds used for the light-emitting device 2 are shown below. (Method for manufacturing the light-emitting device 2)

[0258] First, indium tin oxide containing silicon oxide (ITSO) was deposited onto a glass substrate by sputtering to form anode 101. The thickness of anode 101 was 70 nm, and the electrode area was 2 mm × 2 mm.

[0259] Next, in a pretreatment to form the light-emitting device over a substrate, a surface of the substrate was washed with water and baked at 200 °C for 1 hour, and then a UV ozone treatment was carried out for 370 seconds.

[0260] The substrate was then transferred to a vacuum evaporation unit, where the pressure was increased to approximately 10 -4 After the Pa was reduced, vacuum baking was carried out for 30 minutes at 170 °C in a heating chamber of the vacuum evaporation device, and then the substrate was cooled for approximately 30 minutes.

[0261] Next, the substrate, which was equipped with the anode 101, was attached to a substrate holder provided in the vacuum evaporation apparatus such that the side on which the anode 101 was formed faced downwards. Then, N,N-Bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), represented by structural formula (i), and NDP-9 (manufactured by Analysis Atelier Corporation, material serial number 1S20170124) were deposited onto the anode 101 by co-evaporation using a resistance heating process to a thickness of 10 nm, such that the weight ratio of BBABnf to NDP-9 was 1:0.1, thereby forming the hole injection layer 111.

[0262] Subsequently, BBABnf was deposited over the hole injection layer 111 by evaporation to a thickness of 20 nm to form the first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2), represented by structural formula (ii), was deposited by evaporation to a thickness of 10 nm to form the second hole transport layer 112-2, thus forming the hole transport layer 112. It should be noted that the second hole transport layer 112-2 also serves as an electron blocking layer.

[0263] Subsequently, 7-[4-(10-Phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), represented by structural formula (vii), and N,N'-(Pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-03), represented by structural formula (viii), were deposited by co-evaporation to a thickness of 25 nm such that the weight ratio of cgDBCzPA to 1,6BnfAPrn-03 was 1:0.03, forming the light-emitting layer 113.

[0264] Subsequently, 2-{4-[9,10-Di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN), represented by structural formula (v), and 8-hydroxyquinolinatolithium (abbreviation: Liq), represented by structural formula (vi), were deposited over the light-emitting layer 113 by co-evaporation to a thickness of 25 nm such that the weight ratio of ZADN to Liq was 1:1, thereby forming the electron transport layer 114.

[0265] After forming the electron transport layer 114, Liq was deposited by evaporation to a thickness of 1 nm to form the electron injection layer 115. Subsequently, aluminum was deposited by evaporation to a thickness of 200 nm to form the cathode 102. Thus, the light-emitting device 2 of this example was fabricated.

[0266] The structure of the light-emitting device 2 is listed in the following table. [Table 4] Hole injection layer Hole transport layer light-emitting layer electron transport layer Electron injection layer 1 2 10 nm 20 nm 10 nm 25 nm 25 nm 1 nm Light-emitting device 2 BBABnf:NDP-9(1:0,1) BBABnf PCzN2 cgDBCzPA:1.6BnfAPrn-03(1:0.03) ZADN:Liq(1:1) Liq

[0267] The HOMO levels, LUMO levels, and electron mobilities of the organic compounds used in this example are listed in the following table. The electron mobilities were measured at a field strength of 600 V / cm. [Table 5] HOMO level (eV) LUMO level (eV) Electron mobility (cm) 2 / Vs) BBABnf -5,56 - - PCzN2 -5,71 - - cgDBCzPA -5,69 -2,74 7,7 × 10 -5 ZADN - -2,87 - ZADN:Liq (1:1) - - 3,1 × 10 -6

[0268] The light-emitting device was sealed using a glass substrate in a glove box containing a nitrogen atmosphere, thus preventing exposure to air (a sealing material was applied to completely enclose the element, and the sealing process included UV treatment and a heat treatment at 80 °C for 1 hour). The initial properties and reliability of the light-emitting device were then measured. It should be noted that the measurements were performed at room temperature.

[0269] Fig. Figure 23 shows the luminance-current density properties of the light-emitting device 2. Fig. Figure 24 shows the power efficiency-luminance properties of these. Fig. Figure 25 shows the luminance-voltage properties of these. Fig. Figure 26 shows the current-voltage characteristics of these. Fig.Figure 27 shows the external quantum efficiency luminance properties of these. Fig. Figure 28 shows the emission spectrum of this device. Table 6 shows the main characteristics of the light-emitting device 2 at a luminance of approximately 1000 cd / m². 2 . [Table 6] Voltage (V) Current (mA) Current density (mA / cm³) 2 ) Chromaticityx Chromaticity Y Power efficiency (cd / A) external quantum efficiency Light-emitting device 2 3,6 0,43 10,7 0,14 0,13 9,5 9,4

[0270] Fig. 23, Fig. 24, Fig. 25, Fig. 26, Fig. 27 to Fig. Figure 28 and Table 6 show that the light-emitting device 2 of an embodiment of the present invention is a blue light-emitting device with favorable properties.

[0271] Fig. Figure 29 is a diagram showing changes in luminance with respect to operating time at a current density of 50 mA / cm². 2 shows. As in Fig.As shown in Figure 29, the luminance remains at 97% or more of the initial luminance even after 300 hours have elapsed. This reveals that a decrease in luminance during operation over time is particularly small and that the light-emitting device 2 of an embodiment of the present invention has a very long service life.

[0272] In the decay curve of the light-emitting device 2, the luminance drops once and then increases. This indicates that the decay curve has a local maximum value. The light-emitting device 2, which exhibits such deterioration behavior, has a very long lifetime with a shorter initial decay. [Example 3]

[0273] This example describes a light-emitting device 3 of an embodiment of the present invention. Structural formulas of organic compounds used for the light-emitting device 3 are shown below. (Method for manufacturing the light-emitting device 3)

[0274] First, indium tin oxide containing silicon oxide (ITSO) was deposited onto a glass substrate by sputtering to form anode 101. The thickness of anode 101 was 70 nm, and the electrode area was 2 mm × 2 mm.

[0275] Next, in a pretreatment to form the light-emitting device over a substrate, a surface of the substrate was washed with water and baked at 200 °C for 1 hour, and then a UV ozone treatment was carried out for 370 seconds.

[0276] The substrate was then transferred to a vacuum evaporation unit, where the pressure was increased to approximately 10 -4 After the Pa was reduced, vacuum baking was carried out for 30 minutes at 170 °C in a heating chamber of the vacuum evaporation device, and then the substrate was cooled for approximately 30 minutes.

[0277] Next, the substrate, which was equipped with the anode 101, was attached to a substrate holder provided in the vacuum evaporation apparatus such that the side on which the anode 101 was formed faced downwards. Then, N,N-Bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), represented by structural formula (i), and NDP-9 (manufactured by Analysis Atelier Corporation, material serial number 1S20170124) were deposited onto the anode 101 by co-evaporation using a resistance heating process to a thickness of 10 nm, such that the weight ratio of BBABnf to NDP-9 was 1:0.1, thereby forming the hole injection layer 111.

[0278] Subsequently, BBABnf was deposited over the hole injection layer 111 by evaporation to a thickness of 20 nm to form the first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2), represented by structural formula (ii), was deposited by evaporation to a thickness of 10 nm to form the second hole transport layer 112-2, thus forming the hole transport layer 112. It should be noted that the second hole transport layer 112-2 also serves as an electron blocking layer.

[0279] Subsequently, 7-[4-(10-Phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), represented by structural formula (vii), and 3,10-Bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02), represented by structural formula (iv), were deposited by co-evaporation to a thickness of 25 nm such that the weight ratio of cgDBCzPA to 3,10PCA2Nbf(IV)-02 was 1:0.015, forming the light-emitting layer 113.

[0280] Subsequently, 2-{4-[9,10-Di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN), represented by structural formula (v), and 8-hydroxyquinolinatolithium (abbreviation: Liq), represented by structural formula (vi), were deposited over the light-emitting layer 113 by co-evaporation to a thickness of 25 nm such that the weight ratio of ZADN to Liq was 1:1, thereby forming the electron transport layer 114.

[0281] After forming the electron transport layer 114, Liq was deposited by evaporation to a thickness of 1 nm to form the electron injection layer 115. Subsequently, aluminum was deposited by evaporation to a thickness of 200 nm to form the cathode 102. Thus, the light-emitting device 3 of this example was fabricated.

[0282] The structure of the light-emitting device 3 is listed in the following table. [Table 7] Hole injection layer Hole transport layer light-emitting layer electron transport layer Electron injection layer 1 2 10 nm 20 nm 10 nm 25 nm 25 nm 1 nm Light-emitting device 3 BBABnf:NDP-9(1:0,1) BBABnf PCzN2 cgDBCzPA:3.10PCANbf(IV)-02(1:0.015) ZADN:Liq(1:1) Liq

[0283] The HOMO levels, LUMO levels, and electron mobilities of the organic compounds used in this example are listed in the following table. The electron mobilities were measured at a field strength of 600 V / cm. [Table 8] HOMO level (eV) LUMO level (eV) Electron mobility (cm) 2 / Vs) BBABnf -5,56 - - PCzN2 -5,71 - - cgDBCzPA -5,69 -2,74 7,7 × 10 -5 ZADN - -2,87 - ZADN:Liq (1:1) - - 3,1 × 10 -6

[0284] The light-emitting device was sealed using a glass substrate in a glove box containing a nitrogen atmosphere, thus preventing exposure to air (a sealing material was applied to completely enclose the element, and the sealing process included UV treatment and a heat treatment at 80 °C for 1 hour). The initial properties and reliability of the light-emitting device were then measured. It should be noted that the measurements were performed at room temperature.

[0285] Fig. Figure 30 shows the luminance-current density properties of the light-emitting device 3. Fig. Figure 31 shows the power efficiency-luminance properties of these. Fig. Figure 32 shows the luminance-voltage properties of these. Fig. Figure 33 shows the current-voltage characteristics of these. Fig.Figure 34 shows the external quantum efficiency luminance properties of these. Fig. Figure 35 shows the emission spectrum of this device. Table 9 shows the main characteristics of the light-emitting device 3 at a luminance of approximately 1000 cd / m². 2 . [Table 9] Voltage (V) Current (mA) Current density (mA / cm³) 2 ) Chromaticityx Chromaticity Power efficiency (cd / A) external quantum efficiency (%) Light-emitting device 3 3,5 0,39 9,6 0,14 0,11 10,5 11,1

[0286] Fig. 30, Fig. 31, Fig. 32, Fig. 33, Fig. 34 to Fig. Figure 35 and Table 9 show that the light-emitting device 3 of an embodiment of the present invention is a blue light-emitting device with favorable properties.

[0287] Fig. Figure 36 is a diagram showing changes in luminance with respect to operating time at a current density of 50 mA / cm². 2 shows. As in Fig.Figure 36 shows that in the light-emitting device 3 of an embodiment of the present invention, 94% or more of the initial luminance was maintained even after 300 hours had passed; thus it was found that this is a light-emitting device with a very long lifetime, the luminance of which decreases only slightly over the operating time.

[0288] In the decay curve of the light-emitting device 3, the luminance decreases and then increases. This indicates that the decay curve has a local maximum value. The light-emitting device 3, which exhibits such deterioration behavior, has a very long lifetime with a shorter initial decay. [Example 4]

[0289] This example describes a light-emitting device 4 of an embodiment of the present invention. Structural formulas of organic compounds used for the light-emitting device 4 are shown below. (Method for manufacturing the light-emitting device 4)

[0290] First, an alloy film of silver (Ag), palladium (Pd), and copper (Cu), i.e., an Ag-Pd-Cu (APC) film, was formed as a reflective electrode by sputtering to a thickness of 100 nm. Then, a film of indium tin oxide containing silicon oxide (ITSO) was formed as a transparent electrode by sputtering to a thickness of 85 nm; thus, anode 101 was formed. The electrode area was set to 4 mm². 2 (2 mm × 2 mm) set.

[0291] Next, in a pretreatment to form the light-emitting device over a substrate, a surface of the substrate was washed with water and baked at 200 °C for 1 hour, and then a UV ozone treatment was carried out for 370 seconds.

[0292] The substrate was then transferred to a vacuum evaporation unit, where the pressure was increased to approximately 10 -4 After the Pa was reduced, vacuum baking was carried out for 30 minutes at 170 °C in a heating chamber of the vacuum evaporation device, and then the substrate was cooled for approximately 30 minutes.

[0293] Next, the substrate, which was equipped with the anode 101, was attached to a substrate holder provided in the vacuum evaporation apparatus such that the side on which the anode 101 was formed faced downwards. Then, N,N-Bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), represented by structural formula (i), and NDP-9 (manufactured by Analysis Atelier Corporation, material serial number 1S20170124) were deposited onto the anode 101 by co-evaporation using a resistance heating process to a thickness of 10 nm, such that the weight ratio of BBABnf to NDP-9 was 1:0.05, thereby forming the hole injection layer 111.

[0294] Subsequently, BBABnf was deposited over the hole injection layer 111 by evaporation to a thickness of 25 nm to form the first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2), represented by structural formula (ii), was deposited by evaporation to a thickness of 10 nm to form the second hole transport layer 112-2, thus forming the hole transport layer 112. It should be noted that the second hole transport layer 112-2 also serves as an electron blocking layer.

[0295] Subsequently, 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), represented by structural formula (iii), and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02), represented by structural formula (iv), were deposited by co-evaporation to a thickness of 25 nm such that the weight ratio of αN-βNPAnth to 3,10PCA2Nbf(IV)-02 was 1:0.015, thereby forming the light-emitting layer 113.

[0296] Subsequently, 2-{4-[9,10-Di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN), represented by structural formula (v), and 8-hydroxyquinolinatolithium (abbreviation: Liq), represented by structural formula (vi), were deposited over the light-emitting layer 113 by co-evaporation to a thickness of 25 nm such that the weight ratio of ZADN to Liq was 1:1, thereby forming the electron transport layer 114.

[0297] After forming the electron transport layer 114, the electron injection layer 115 was formed by evaporating Liq to a thickness of 1 nm. The cathode 102 was formed by evaporation to a thickness of 15 nm such that the volume ratio of silver (Ag) to magnesium (Mg) was 1:0.1. Thus, the light-emitting device 4 was produced. The cathode 102 is a semi-transparent and semi-reflective electrode, having a function for reflecting light and a function for transmitting light; therefore, the light-emitting device 4 of this example is a top-emission device in which light is extracted via the cathode 102. Above the cathode 102, 1,3,5-Tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II), represented by the structural formula (ix), was deposited by evaporation to a thickness of 80 nm, thus improving the extraction efficiency.

[0298] The structure of the light-emitting device 4 is listed in the following table. [Table 10] Hole injection layer Hole transport layer light-emitting layer electron transport layer Electron injection layer 1 2 10 nm 25 nm 10 nm 25 nm 25 nm 1 nm Light-emitting device 4 BBABnf:NDP-9(1:0,05) BBABnf PCzN2 αN-βNPAnth:3.10PCANbf(IV)-02(1:0.015) ZADN:Liq(1:1) Liq

[0299] The HOMO levels, LUMO levels, and electron mobilities of the organic compounds used in this example are listed in the following table. The electron mobilities were measured at a field strength of 600 V / cm. [Table 11] HOMO level (eV) LUMO level (eV) Electron mobility (cm) 2 / Vs) BBABnf -5,56 - - PCzN2 -5,71 - - αN-βNPAnth -5,85 -2,74 - ZADN - -2,87 - ZADN:Liq (1:1) - - 3,1 × 10 -6

[0300] The light-emitting device was sealed using a glass substrate in a glove box containing a nitrogen atmosphere, thus preventing its exposure to air (a sealing material was applied to enclose the element, and the sealing process included UV treatment and a heat treatment at 80 °C for 1 hour). The initial properties and reliability of the light-emitting device 4 were then measured. It should be noted that the measurement was performed at room temperature.

[0301] Fig. Figure 42 shows the luminance-current density properties of the light-emitting device 4. Fig. Figure 43 shows the power efficiency-luminance properties of these. Fig. Figure 44 shows the luminance-voltage properties of these. Fig. Figure 45 shows the current-voltage characteristics of these. Fig.Figure 46 shows the external quantum efficiency luminance properties of these. Fig. Figure 47 shows the emission spectra of these. Table 12 shows the main characteristics of the light-emitting device 4 at a luminance of approximately 1000 cd / m². 2 . [Table 12] Voltage (V) Current (mA) Current density (mA / cm³) 2 ) Chromaticityx Chromaticity Power efficiency (cd / A) external quantum efficiency (%) light-emitting device 4 5,2 0,87 21,9 0,14 0,05 4,7 9,1

[0302] Fig. 42, Fig. 43, Fig. 44, Fig. 45, Fig. 46 to Fig. Figure 47 and Table 12 show that the light-emitting device 4 of an embodiment of the present invention is a blue light-emitting device with favorable properties.

[0303] Fig. Figure 48 shows a change in the luminance of the light-emitting device with operating time under the following conditions: The initial luminance was 1300 cd / m² 2 and the current density was constant. As in Fig.As shown in Figure 48, the light-emitting device 4 of an embodiment of the present invention maintained approximately 95% of its initial luminance even after 1000 hours had passed; thus, it was found that this is a long-life light-emitting device whose luminance decreases slightly over the operating time. [Example 5]

[0304] This example describes a light-emitting device 5 of an embodiment of the present invention. Structural formulas of organic compounds used for the light-emitting device 5 are shown below. (Method for manufacturing the light-emitting device 5)

[0305] First, indium tin oxide containing silicon oxide (ITSO) was deposited onto a glass substrate by sputtering to form anode 101. The thickness of anode 101 was 70 nm, and the electrode area was 2 mm × 2 mm.

[0306] Next, in a pretreatment to form the light-emitting device over a substrate, a surface of the substrate was washed with water and baked at 200 °C for 1 hour, and then a UV ozone treatment was carried out for 370 seconds.

[0307] The substrate was then transferred to a vacuum evaporation unit, where the pressure was increased to approximately 10 -4 After the Pa was reduced, vacuum baking was carried out for 30 minutes at 170 °C in a heating chamber of the vacuum evaporation device, and then the substrate was cooled for approximately 30 minutes.

[0308] Next, the substrate, which was equipped with the anode 101, was attached to a substrate holder provided in the vacuum evaporation apparatus such that the side on which the anode 101 was formed faced downwards. Then, N,N-Bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), represented by structural formula (i), and NDP-9 (manufactured by Analysis Atelier Corporation, material serial number 1S20170124) were deposited onto the anode 101 by co-evaporation using a resistance heating process to a thickness of 10 nm, such that the weight ratio of BBABnf to NDP-9 was 1:0.1, thereby forming the hole injection layer 111.

[0309] Subsequently, BBABnf was deposited over the hole injection layer 111 by evaporation to a thickness of 20 nm to form the first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2), represented by structural formula (ii), was deposited by evaporation to a thickness of 80 nm to form the second hole transport layer 112-2, thus forming the hole transport layer 112. It should be noted that the second hole transport layer 112-2 also serves as an electron blocking layer.

[0310] Subsequently, 9-[(3'-Dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), represented by structural formula (x), N-[4-(9-Phenyl-9H-carbazol-3-yl)phenyl]-bis(9,9-dimethyl-9H-fluoren-2-yl)amine (abbreviation: PCBFF), represented by structural formula (xi), and Bis[4,6-dimethyl-2-(7-(2-methylpropyl)-2-quinolinyl-{N)phenyl-κC](2,4-pentanedionato-κ 2 O,O')iridium(III) (abbreviation: RS003), which is represented by the structural formula (xii), is deposited by Co evaporation in a thickness of 65 nm such that the weight ratio of 9mDBtBPNfpr to PCBFF and RS003 was 0.5:0.5:0.05, thereby forming the light-emitting layer 113.

[0311] Subsequently, 2-{4-[9,10-Di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN), represented by structural formula (v), and 8-hydroxyquinolinatolithium (abbreviation: Liq), represented by structural formula (vi), were deposited over the light-emitting layer 113 by co-evaporation to a thickness of 20 nm such that the weight ratio of ZADN to Liq was 1:1, thereby forming the electron transport layer 114.

[0312] After forming the electron transport layer 114, Liq was deposited by evaporation to a thickness of 1 nm to form the electron injection layer 115. Subsequently, aluminum was deposited by evaporation to a thickness of 200 nm to form the cathode 102. Thus, the light-emitting device 5 of this example was fabricated.

[0313] The structure of the light-emitting device 5 is listed in the following table. [Table 13] Hole injection layer Hole transport layer light-emitting layer electron transport layer Electron injection layer 1 2 10 nm 20 nm 80 nm 65 nm 20 nm 1 nm Light-emitting device 5 BBABnf:NDP-9(1:0,1) BBABnf PCzN2 9mDBtBPNfpr:PCBFF:RS003(0,5:0,5:0,05) ZADN:Liq(1:1) Liq

[0314] The HOMO levels, LUMO levels, and electron mobilities of the organic compounds used in this example are listed in the following table. The electron mobilities were measured at a field strength of 600 V / cm. [Table 14] HOMO level (eV) LUMO level (eV) Electron mobility (cm) 2 / Vs) BBABnf -5,56 - - PCzN2 -5,71 - - ZADN -5,82 -2,87 - ZADN:Liq (1:1) - - 3,5 × 10 -6

[0315] The light-emitting device was sealed using a glass substrate in a glove box containing a nitrogen atmosphere, thus preventing exposure to air (a sealing material was applied to completely enclose the element, and the sealing process included UV treatment and a heat treatment at 80 °C for 1 hour). The initial properties and reliability of the light-emitting device were then measured. It should be noted that the measurements were performed at room temperature.

[0316] Fig. Figure 49 shows the luminance-current density properties of the light-emitting device 5. Fig. 50 shows the power efficiency-luminance properties of this. Fig. Figure 51 shows the luminance-voltage properties of these. Fig. Figure 52 shows the current-voltage characteristics of these. Fig.Figure 53 shows the external quantum efficiency luminance properties of these. Fig. Figure 54 shows the emission spectra of these. Table 15 shows the main properties of the light-emitting device 5 at a luminance of approximately 1000 cd / m². 2 . [Table 15] Voltage (V) Current (mA) Current density (mA / cm³) 2 ) Chromaticityx Chromaticity Power efficiency (cd / A) external quantum efficiency (%) Light-emitting device 5 4,4 0,29 7,2 0,67 0,33 13,1 12,4

[0317] Fig. 49, Fig. 50, Fig. 51, Fig. 52, Fig. 53 to Fig. Figure 54 and Table 15 show that the light-emitting device 5 of an embodiment of the present invention is a red light-emitting device with favorable properties.

[0318] Fig. Figure 55 is a diagram (decay curve) showing changes in luminance over time at a current density of 75 mA / cm². 2 shows. As in Fig.As shown in Figure 55, the luminance remains at 99% or more of the initial luminance even after 100 hours have elapsed. This reveals that the decrease in luminance during operation over time is particularly small, and the light-emitting device 5 of an embodiment of the present invention has a very long lifetime. The decay curve has a characteristic shape, i.e., it has a local maximum value, so that the light-emitting device 5 can have a very long lifetime by exhibiting the aforementioned deterioration behavior. [Example 6]

[0319] This example describes a light-emitting device 6 of an embodiment of the present invention. Structural formulas of organic compounds used for the light-emitting device 6 are shown below. (Method for manufacturing the light-emitting device 6)

[0320] First, indium tin oxide containing silicon oxide (ITSO) was deposited onto a glass substrate by sputtering to form anode 101. The thickness of anode 101 was 70 nm, and the electrode area was 4 mm². 2 (2 mm × 2 mm).

[0321] Next, in a pretreatment to form the light-emitting device over a substrate, a surface of the substrate was washed with water and baked at 200 °C for 1 hour, and then a UV ozone treatment was carried out for 370 seconds.

[0322] The substrate was then transferred to a vacuum evaporation unit, where the pressure was increased to approximately 10 -4 After the Pa was reduced, vacuum baking was carried out for 30 minutes at 170 °C in a heating chamber of the vacuum evaporation device, and then the substrate was cooled for approximately 30 minutes.

[0323] Next, the substrate, which was equipped with the anode 101, was attached to a substrate holder provided in the vacuum evaporation apparatus such that the side on which the anode 101 was formed faced downwards. Then, N,N-Bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), represented by structural formula (i), and NDP-9 (manufactured by Analysis Atelier Corporation, material serial number 1S20170124) were deposited onto the anode 101 by co-evaporation using a resistance heating process to a thickness of 10 nm, such that the weight ratio of BBABnf to NDP-9 was 1:0.1, thereby forming the hole injection layer 111.

[0324] Subsequently, BBABnf was deposited over the hole injection layer 111 by evaporation to a thickness of 15 nm to form the first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2), represented by structural formula (ii), was deposited by evaporation to a thickness of 40 nm to form the second hole transport layer 112-2, thus forming the hole transport layer 112. It should be noted that the second hole transport layer 112-2 also serves as an electron blocking layer.

[0325] Subsequently, 8-(1,1'-Biphenyl-4-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtPBfpm), represented by structural formula (xiii), 3,3'-Bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), represented by structural formula (xiv), and [2-(4-Methyl-5-phenyl-2-pyridinyl-κN)phenyl-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy)2(mdppy)]), represented by structural formula (xv), were deposited by co-evaporation to a thickness of 45 nm such that the weight ratio of 8BP-4mDBtPBfpm to PCCP and [Ir(ppy)2(mdppy)] 0,4:0,6:0,1 was formed, creating the light-emitting layer 113.

[0326] Subsequently, 2-{4-[9,10-Di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN), represented by structural formula (v), and 8-hydroxyquinolinatolithium (abbreviation: Liq), represented by structural formula (vi), were deposited over the light-emitting layer 113 by co-evaporation to a thickness of 25 nm such that the weight ratio of ZADN to Liq was 1:0.9, thereby forming the electron transport layer 114.

[0327] After forming the electron transport layer 114, Liq was deposited by evaporation to a thickness of 1 nm to form the electron injection layer 115. Subsequently, aluminum was deposited by evaporation to a thickness of 200 nm to form the cathode 102. Thus, the light-emitting device 6 of this example was fabricated.

[0328] The structure of the light-emitting device 6 is listed in the following table. [Table 16] Hole injection layer Hole transport layer light-emitting layer electron transport layer Electron injection layer 1 2 10 nm 15 nm 40 nm 45 nm 25 nm 1 nm Light-emitting device 6 BBABnf:NDP-9(1:0,1) BBABnf PCzN2 8BP-4mDBtBPBfpm:PCCP:[Ir(ppy)2(mdppy)](0.4:0.6:0.1) ZADN:Liq(1:0,9) Liq

[0329] The HOMO levels, LUMO levels, and electron mobilities of the organic compounds used in this example are listed in the following table. The electron mobilities were measured at a field strength of 600 V / cm. [Table 17] HOMO level (eV) LUMO level (eV) Electron mobility (cm) 2 / Vs) BBABnf -5,56 - - PCzN2 -5,71 - - ZADN -5,82 -2,87 - ZADN:Liq (1:1) - - 3,5 × 10 -6

[0330] The light-emitting device was sealed using a glass substrate in a glove box containing a nitrogen atmosphere, thus preventing exposure to air (a sealing material was applied to completely enclose the element, and the sealing process included UV treatment and a heat treatment at 80 °C for 1 hour). The initial properties and reliability of the light-emitting device were then measured. It should be noted that the measurements were performed at room temperature.

[0331] Fig. Figure 56 shows the luminance-current density properties of the light-emitting device 6. Fig. Figure 57 shows the power efficiency-luminance properties of these. Fig. Figure 58 shows the luminance-voltage properties of these. Fig. Figure 59 shows the current-voltage characteristics of these. Fig.Figure 60 shows the external quantum efficiency luminance properties of these. Fig. Figure 61 shows the emission spectrum of this device. Table 18 shows the main characteristics of the light-emitting device 6 at a luminance of approximately 1000 cd / m². 2 . [Table 18] Voltage (V) Current (mA) Current density (mA / cm³) 2 ) Chromaticityx Chromaticity Power efficiency (cd / A) external quantum efficiency (%) Light-emitting device 6 3,7 0,05 1,2 0,33 0,63 80,8 21,7

[0332] Fig. 56, Fig. 57, Fig. 58, Fig. 59, Fig. 60 to Fig. Figure 61 and Table 18 show that the light-emitting device 6 of an embodiment of the present invention is a green light-emitting device with favorable properties.

[0333] Fig. Figure 62 is a diagram showing changes in luminance with respect to operating time at a current density of 50 mA / cm². 2 shows. As in Fig.Figure 62 shows that the luminance remains at 80% or more of the initial luminance even after 200 hours have passed. This reveals that the reduction in luminance during operation over time is particularly small and that the light-emitting device 6 of an embodiment of the present invention has a very long service life. [Example 7]

[0334] This example describes a light-emitting device 7 of an embodiment of the present invention. Structural formulas of organic compounds used for the light-emitting device 7 are shown below. (Method for manufacturing the light-emitting device 7)

[0335] First, indium tin oxide containing silicon oxide (ITSO) was deposited onto a glass substrate by sputtering to form anode 101. The thickness of anode 101 was 70 nm, and the electrode area was 2 mm × 2 mm.

[0336] Next, in a pretreatment to form the light-emitting device over a substrate, a surface of the substrate was washed with water and baked at 200 °C for 1 hour, and then a UV ozone treatment was carried out for 370 seconds.

[0337] The substrate was then transferred to a vacuum evaporation unit, where the pressure was increased to approximately 10 -4 After the Pa was reduced, vacuum baking was carried out for 30 minutes at 170 °C in a heating chamber of the vacuum evaporation device, and then the substrate was cooled for approximately 30 minutes.

[0338] Next, the substrate, which was equipped with the anode 101, was attached to a substrate holder provided in the vacuum evaporation apparatus such that the side on which the anode 101 was formed faced downwards. Then, N,N-Bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), represented by structural formula (i), and NDP-9 (manufactured by Analysis Atelier Corporation, material serial number 1S20170124) were deposited onto the anode 101 by co-evaporation using a resistance heating process to a thickness of 10 nm, such that the weight ratio of BBABnf to NDP-9 was 1:0.1, thereby forming the hole injection layer 111.

[0339] Subsequently, BBABnf was deposited over the hole injection layer 111 by evaporation to a thickness of 55 nm to form the first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2), represented by structural formula (ii), was deposited by evaporation to a thickness of 30 nm to form the second hole transport layer 112-2, thus forming the hole transport layer 112. It should be noted that the second hole transport layer 112-2 also serves as an electron blocking layer.

[0340] Subsequently, 9-[(3'-Dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), represented by structural formula (x), N-(1,1'-Biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluorene-2-amine (abbreviation: PCBBiF), represented by structural formula (xvi), and Bis{4,6-dimethyl-2-[5-(5-cyano-2-methylphenyl)-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-m5CP)2(dpm)]), which is represented by the structural formula (xvii), was deposited by Co evaporation in a thickness of 60 nm such that the weight ratio of 9mDBtBPNfpr to PCBBiF and [Ir(dmdppr-m5CP)2(dpm)] was 0.8:0.2:0.1, thereby forming the light-emitting layer 113.

[0341] Subsequently, 2-{4-[9,10-Di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN), represented by structural formula (v), and 8-hydroxyquinolinatolithium (abbreviation: Liq), represented by structural formula (vi), were deposited over the light-emitting layer 113 by co-evaporation to a thickness of 25 nm such that the weight ratio of ZADN to Liq was 1:0.9, thereby forming the electron transport layer 114.

[0342] After forming the electron transport layer 114, Liq was deposited by evaporation to a thickness of 1 nm to form the electron injection layer 115. Subsequently, aluminum was deposited by evaporation to a thickness of 200 nm to form the cathode 102. Thus, the light-emitting device 7 of this example was fabricated.

[0343] The structure of the light-emitting device 7 is listed in the following table. [Table 19] Hole injection layer Hole transport layer light-emitting layer electron transport layer Electron injection layer 1 2 10 nm 55 nm 30 nm 60 nm 25 nm 1 nm Light-emitting device 7 BBABnf:NDP-9(1:0,1) BBABnf PCzN2 9mDBtBPNfpr:PCBBiF:[Ir(dmdppr-m5CP)2(dpm)](0.8:0.2:0.1) ZADN:Liq(1:1) Liq

[0344] The HOMO levels, LUMO levels, and electron mobilities of the organic compounds used in this example are listed in the following table. The electron mobilities were measured at a field strength of 600 V / cm. [Table 20] HOMO level (eV) LUMO level (eV) Electron mobility (cm) 2 / Vs) BBABnf -5,56 - - PCzN2 -5,71 - - ZADN -5,82 -2,87 - ZADN:Liq (1:1) - - 3,5 × 10 -6

[0345] The light-emitting device was sealed using a glass substrate in a glove box containing a nitrogen atmosphere, thus preventing exposure to air (a sealing material was applied to completely enclose the element, and the sealing process included UV treatment and a heat treatment at 80 °C for 1 hour). The initial properties and reliability of the light-emitting device were then measured. It should be noted that the measurements were performed at room temperature.

[0346] Fig. Figure 63 shows the luminance-current density properties of the light-emitting device 7. Fig. Figure 64 shows the power efficiency-luminance properties of these. Fig. Figure 65 shows the luminance-voltage properties of these. Fig. Figure 66 shows the current-voltage characteristics of these. Fig.Figure 67 shows the external quantum efficiency luminance properties of these. Fig. Figure 68 shows the emission spectrum of this device. Table 21 shows the main characteristics of the light-emitting device 7 at a luminance of approximately 1000 cd / m². 2 . [Table 21] Voltage (V) Current (mA) Current density (mA / cm³) 2 ) Chromaticityx Chromaticity Power efficiency (cd / A) external quantum efficiency (%) Light-emitting device 7 4,4 0,28 7,0 0,71 0,29 13,9 28,4

[0347] Fig. 63, Fig. 64, Fig. 65, Fig. 66, Fig. 67 to Fig. Figure 68 and Table 21 show that the light-emitting device 7 of an embodiment of the present invention is a red light-emitting device with favorable properties.

[0348] Fig. Figure 69 is a diagram showing changes in luminance with respect to operating time at a current density of 75 mA / cm². 2 shows. As in Fig.As shown in Figure 69, the luminance remains at 90% or more of the initial luminance even after 400 hours have elapsed. This reveals that a decrease in luminance during operation over time is particularly small and that the light-emitting device 7 of an embodiment of the present invention has a very long service life. [Example 8]

[0349] This example describes light-emitting devices 8 and 9 of an embodiment of the present invention. Structural formulas of organic compounds used for the light-emitting devices 8 and 9 are shown below. (Method for manufacturing the light-emitting device 8)

[0350] First, indium tin oxide containing silicon oxide (ITSO) was deposited onto a glass substrate by sputtering to form anode 101. The thickness of anode 101 was 70 nm, and the electrode area was 4 mm². 2 (2 mm × 2 mm).

[0351] Next, in a pretreatment to form the light-emitting device over a substrate, a surface of the substrate was washed with water and baked at 200 °C for 1 hour, and then a UV ozone treatment was carried out for 370 seconds.

[0352] The substrate was then transferred to a vacuum evaporation unit, where the pressure was increased to approximately 10 -4 After the Pa was reduced, vacuum baking was carried out for 30 minutes at 170 °C in a heating chamber of the vacuum evaporation device, and then the substrate was cooled for approximately 30 minutes.

[0353] Next, the substrate, which was equipped with the anode 101, was attached to a substrate holder provided in the vacuum evaporation apparatus such that the side on which the anode 101 was formed faced downwards. Then, N,N-Bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), represented by structural formula (i), and NDP-9 (manufactured by Analysis Atelier Corporation, material serial number 1S20170124) were deposited onto the anode 101 by co-evaporation using a resistance heating process to a thickness of 10 nm, such that the weight ratio of BBABnf to NDP-9 was 1:0.05, thereby forming the hole injection layer 111.

[0354] Subsequently, BBABnf was deposited over the hole injection layer 111 by evaporation to a thickness of 40 nm to form the first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2), represented by structural formula (ii), was deposited by evaporation to a thickness of 20 nm to form the second hole transport layer 112-2, thus forming the hole transport layer 112. It should be noted that the second hole transport layer 112-2 also serves as an electron blocking layer.

[0355] Subsequently, 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4.6mCzP2Pm), represented by structural formula (xviii), 8-(dibenzothiophen-4-yl)-4-phenyl-2-(9'-phenyl-3,3'-bi-9H-carbazol-9-yl)-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4Ph-8DBt-2PCCzBfpm), represented by structural formula (xx), and 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (abbreviation: TBRb), represented by structural formula (xii), were deposited by co-evaporation to a thickness of 40 nm such that the weight ratio of 4,6mCzP2Pm to 4Ph-8DBt-2PCCzBfpm and TBRb 1,0:0,1:0,01, which formed the light-emitting layer 113.

[0356] Subsequently, 2-{4-[9,10-Di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN), represented by structural formula (v), and 8-hydroxyquinolinatolithium (abbreviation: Liq), represented by structural formula (vi), were deposited over the light-emitting layer 113 by co-evaporation to a thickness of 25 nm such that the weight ratio of ZADN to Liq was 1:1, thereby forming the electron transport layer 114.

[0357] After forming the electron transport layer 114, Liq was deposited by evaporation to a thickness of 1 nm to form the electron injection layer 115. Subsequently, aluminum was deposited by evaporation to a thickness of 200 nm to form the cathode 102. Thus, the light-emitting device 8 of this example was fabricated. (Method for manufacturing the light-emitting device 9)

[0358] The light-emitting device 9 was manufactured in the same way as the light-emitting device 8, except that the first hole transport layer 112-1 of the light-emitting device 8 was formed in a thickness of 30 nm and the light-emitting layer 113 was formed without TBRb.

[0359] The structures of the light-emitting devices 8 and 9 are listed in the following table. [Table 22] Hole injection layer Hole transport layer light-emitting layer electron transport layer Electron injection layer 1 2 10 nm *1 20 nm 40 nm 25 nm 1 nm Light-emitting device 8 BBABnf:NDP-9(1:0,05) BBABnf PCzN2 4.6mCzP2Pm:4Ph-8DBt-2PCCzBfpm:TBRb(1:0.1:0.01) ZADN:Liq(1:1) Liq Light-emitting device9 4.6mCzP2Pm:4Ph-8DBt-2PCCzBfpm(1:0.1) *1 Light-emitting device 8:40 nm Light-emitting device 9:30 nm

[0360] It should be noted that 4Ph-8DBt-2PCCzBfpm, used in the light-emitting layer, is a substance that emits thermally activated delayed fluorescence (TADF). In light-emitting device 8, 4Ph-8DBt-2PCCzBfpm is used as a host material. In light-emitting device 9, which has a light emission mechanism in which energy is transferred to TBRb, a fluorescent substance, 4Ph-8DBt-2PCCzBfpm, being a TADF material, itself emits light.

[0361] The HOMO levels, LUMO levels, and electron mobilities of the organic compounds used in this example are listed in the following table. The electron mobilities were measured at a field strength of 600 V / cm. [Table 23] HOMO level (eV) LUMO level (eV) Electron mobility (cm) 2 / Vs) BBABnf -5,56 - - PCzN2 -5,71 - - ZADN -5,82 -2,87 - ZADN:Liq (1:1) - - 3,5 × 10 -6

[0362] These light-emitting devices were sealed using a glass substrate in a glove box containing a nitrogen atmosphere to prevent exposure to air (a sealing material was applied to enclose the element, and the sealing process included UV treatment and a heat treatment at 80 °C for 1 hour). The initial properties and reliability of the light-emitting devices were then measured. It should be noted that the measurements were performed at room temperature.

[0363] Fig. Figure 70 shows the luminance-current density properties of the light-emitting devices 8 and 9. Fig. Figure 71 shows the power efficiency-luminance properties of these. Fig. Figure 72 shows the luminance-voltage properties of these. Fig. Figure 73 shows the current-voltage characteristics of these. Fig.Figure 74 shows the external quantum efficiency luminance properties of these. Fig. Figure 75 shows the emission spectra of these. Table 24 shows the main characteristics of the light-emitting devices 8 and 9 at a luminance of approximately 1000 cd / m². 2 . [Table 24] Voltage (V) Current (mA) Current density (mA / cm³) 2 ) Chromaticityx Chromaticity Power efficiency (cd / A) external quantum efficiency (%) Light-emitting device 8 4,8 0,10 2,6 0,41 0,54 34,5 10,3 Light-emitting device 9 4,8 0,12 3,1 0,25 0,53 33,4 11,6

[0364] Fig. 70, Fig. 71, Fig. 72, Fig. 73, Fig. 74 to Fig. Reference 75 and Table 24 show that the light-emitting devices 8 and 9 of an embodiment of the present invention are light-emitting devices with high emission efficiency.

[0365] Fig. Figure 76 is a diagram showing changes in luminance with respect to operating time at a current density of 50 mA / cm². 2 shows. As in Fig.As shown in Figure 76, it was found that the light-emitting device 8 and the light-emitting device 9 of an embodiment of the present invention have a long lifetime by using TADF for a host material and a light-emitting material. <Referenzbeispiel 1>

[0366] This reference example describes methods for calculating the HOMO levels, LUMO levels and electron mobilities of the organic compounds used in the examples.

[0367] The HOMO level and the LUMO level can be calculated by a cyclic voltammetry (CV) measurement.

[0368] An electrochemical analyzer (ALS model 600A or 600C, manufactured by BAS Inc.) was used as the measuring device. A solution for the CV measurement was prepared as follows: Tetra-n-butylammonium perchlorate (n-Bu4NClO4, manufactured by Tokyo Chemical Industry Co., Ltd., catalog no. T0836) as the carrier electrolyte was dissolved in anhydrous dimethylformamide (DMF, manufactured by Sigma-Aldrich Co. LLC., 99.8%, catalog no. 22705-6) as the solvent at a concentration of 100 mmol / L, and the object to be measured was dissolved in it 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 +A reference electrode (RE7 reference electrode for a non-aqueous solvent, manufactured by BAS Inc.) was used. The measurement was performed at room temperature (20 °C to 25 °C). Additionally, the sampling rate for the CV measurement was set to 0.1 V / s, and an oxidation potential Ea [V] and a reduction potential Ec [V] relative to the reference electrode were measured. Potential Ea is an intermediate potential of an oxidation-reduction wave, and potential Ec is an intermediate potential of a reduction-oxidation wave. 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 using the following formulas: HOMO level [eV] = -4.94 - Ea and LUMO level [eV] = -4.94 - Ec.

[0369] Electron mobility can be measured using impedance spectroscopy (IS).

[0370] Methods for measuring the charge carrier mobility of an EL material have long included time-of-flight (TOF) techniques, methods utilizing IV properties of a space-charge-limited current (SCLC), and similar approaches. The TOF method requires a sample with a much greater thickness than that of an actual organic EL element. The SCLC method has the disadvantage that, for example, a dependence of the charge carrier mobility on the electric field strength cannot be achieved. Since the organic film required for measurement with the IS method is thin (approximately a few tens of nanometers), the organic film can be formed from a relatively small amount of EL material, allowing the mobility to be measured with a thickness close to that of a film in an actual EL element.This method can also be used to measure the dependence of charge carrier mobility on the electric field strength.

[0371] In the IS method, a microsinusoidal voltage signal (V = V0[exp(jωt)]) is applied to an EL element, and the impedance of the EL element is obtained from the phase difference between the current amplitude of a response current signal (I = I0exp[j(ωt + ϕ)]) and the input signal. By applying the voltage to the EL element while its frequency changes from a high level to a low level, components with different relaxation times that contribute to the impedance can be separated and measured.

[0372] Here, the admittance Y (= 1 / Z), which is the reciprocal of the impedance, can be represented by the conductance G and the susceptance B as in the following formula (1). [Formula 1] Y=1Z=G+jB

[0373] Furthermore, the following formulas (2) and (3) can be calculated using a single injection model. In formula (4), g is the differential admittance. In the formula, C represents the capacitance, θ represents a transmission angle (ωt), ω represents the angular frequency, and t represents the transit time. The analysis uses the current equation, the Poisson equation, and the current continuity equation, while ignoring diffusion current and trapping conditions. [Formula 2] G=gθ36θ−sin θ(θ−sin θ)2+(θ22−cos θ−1)2 G=ωC=g036θ22+cos θ−1(θ−sin θ)2+(θ22+cos θ−1)2 g=94εμV0d3

[0374] A method for calculating mobility from the frequency characteristics of capacitance is a -ΔB method. A method for calculating mobility from the frequency characteristics of admittance is a ωΔG method.

[0375] In practice, an all-electron cell is first fabricated using a material whose electron mobility is to be calculated. The all-electron cell is designed such that only electrons flow within it as charge carriers. This description outlines a method for calculating the mobility from the frequency properties of the capacitance (the -ΔB method). Fig. Figure 37 is a schematic diagram of an all-electron cell used for measurement.

[0376] As in Fig.As shown in Figure 37, the all-electron cell prepared for measurement in this example comprises a first layer 210, a second layer 211, and a third layer 212 between an anode 201 and a cathode 202. The material whose electron mobility is to be preserved is used as the material for the second layer 211. For illustration, an example is given in which the electron mobility of a film formed by co-evaporation of ZADN and Liq in a weight ratio of 1:1 is measured. A specific structural example is listed in the following table. [Table 25] anode first shift second shift third layer cathode 100nm 50 nm 100nm 1 nm 200 nm 1 nm 100 nm APC NITO Al Liq ZADN:Liq(1:1) Liq Al

[0377] Fig. Figure 38 shows the current density-voltage properties of the only-electron cell in which the film formed by co-evaporation of ZADN and Liq is used as the second layer 211.

[0378] The impedance was measured under conditions where the frequency was 1 Hz to 3 MHz, the AC voltage was 70 mV, and a DC voltage in the range of 5.0 V to 9.0 V was applied. Here, the capacitance is calculated from the admittance, which is the reciprocal of the obtained impedance (the preceding formula (1)). Fig. Figure 39 shows the frequency characteristics of the calculated capacitance C at the applied voltage of 7.0 V.

[0379] The frequency characteristics of the capacitance C result from a phase difference of the current generated, since a space charge created by charge carriers injected by the microvoltage signal cannot fully follow the micro-AC voltage. The transit time (propagation time) of the injected charge carriers in the film is defined by the time T until the charge carriers reach a counter electrode and is represented by the following formula (5).

[0380] [Formula 3] T=43L2μV0

[0381] A change in negative susceptance (-ΔB) corresponds to a value (-ωΔC) obtained by multiplying a change in capacitance -ΔC by an angular frequency ω. Formula (3) shows that there is a relationship between the peak frequency on the side of the lowest frequency f' max (=ω max / 2π) and the transit time T, as shown in the following formula (6). [Formula 4] T=4.52πfmax'

[0382] Fig. Figure 40 shows the frequency characteristics of -ΔB calculated from the preceding measurement (i.e., -ΔB at a DC voltage of 7.0 V). The peak frequency on the side of the lowest frequency is f'. max will be in Fig. 40 marked by an arrow.

[0383] The transit time T is calculated from f' max, which is obtained from the preceding measurement and analysis (see formula (6) above); thus, in this example, the electron mobility at a DC voltage of 7.0 V can be obtained from formula (5) above. By performing the same measurement with a DC voltage in the range of 5.0 V to 9.0 V, the electron mobility can be calculated at any voltage (electric field strength), so that the dependence of the mobility on the electric field strength can also be measured.

[0384] Fig. Figure 41 shows the final dependence of the electron mobility on the electric field strength of the organic compounds obtained using the above calculation method, and Table 10 shows the values ​​of the electron mobility in the case where the square root of the electric field strength [V / cm] read from the figure is 600 [V / cm]. 1 / 2 fraud. [Table 26] Electron mobility (cm) 2 / Vs) cgDBCzPA 7,7 × 10 -5 2mDBTBPDBq-II 2,2 × 10 -5 ZADN:Liq (1:1) 3,5 × 10 -6

[0385] Electron mobility can be calculated as described above. For details of the measurement procedure, please refer to the following reference: T. Okachi et al., Japanese Journal of Applied Physics, Vol. 47, No. 12, pp. 8965-8972, 2008. <Referenzbeispiel 2>

[0386] Synthesis methods for 9mDBtBPNfpr and 8BP-4mDBtPBfpm, which are unpublished substances and are used in the example, are described. <<Syntheseverfahren von 9mDBtBPNfpr> >

[0387] A method for synthesizing 9-[(3'-Dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), represented by the structural formula (x) of Example 1, is described. The structure of 9mDBtBPNfpr is shown below. (Step 1: Synthesis of 6-chloro-3-(2-methoxynaphthalen-1-yl)pyrazine-2-amine)

[0388] In a three-necked flask equipped with a reflux tube, 4.37 g of 3-bromo-6-chloropyrazine-2-amine, 4.23 g of 2-methoxynaphthalene-1-boronic acid, 4.14 g of potassium fluoride, and 75 ml of anhydrous tetrahydrofuran were first placed, and the air in the flask was replaced with nitrogen. The mixture in the flask was degassed by stirring under reduced pressure, and then 0.57 g of tris(dibenzylideneacetone)dipalladium(0) (abbreviation: Pd₂(dba)₃) and 4.5 ml of tri-tert-butylphosphine (abbreviation: P(tBu)₃) were added. The mixture was stirred at 80 °C for 54 hours to initiate a reaction.

[0389] After a predetermined time, the resulting mixture was subjected to suction filtration, and the filtrate was concentrated. Purification was then carried out by silica gel column chromatography using a mobile phase (toluene:ethyl acetate = 9:1) to obtain a pyrazine derivative, which was the target compound (2.19 g of a yellowish-white powder in a yield of 36%). The synthesis scheme for step 1 is shown below. (Step 2: Synthesis of 9-Chlornaphtho[1',2':4,5]furo[2,3-b]pyrazine)

[0390] Next, 2.18 g of 6-chloro-3-(2-methoxynaphthalen-1-yl)pyrazine-2-amine, obtained in step 1, were added to a three-necked flask, along with 63 mL of anhydrous tetrahydrofuran and 84 mL of acetic acid, and the air in the flask was replaced with nitrogen. After the flask had been cooled to -10 °C, 2.8 mL of tert-butyl nitrite were added dropwise, and the mixture was stirred at -10 °C for 30 minutes and at 0 °C for 3 hours. After a predetermined time, 250 mL of water were added to the resulting suspension, and suction filtration was carried out, giving a pyrazine derivative, which was the target compound (1.48 g of a yellowish-white powder in a yield of 77%). The synthesis scheme of step 2 is shown below. (Step 3: Synthesis of 9-[(3'-Dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr))

[0391] Into a three-necked flask, 1.48 g of 9-chloronaphtho[1',2':4,5]furo[2,3-b]pyrazine, obtained in step 2, 3.41 g of 3'-(4-dibenzothiophene)-1,1'-biphenyl-3-boronic acid, 8.8 mL of a 2 M aqueous potassium carbonate solution, 100 mL of toluene, and 10 mL of ethanol were added, and the air in the flask was replaced with nitrogen. The mixture in the flask was degassed by stirring under reduced pressure, and then 0.84 g of bis(triphenylphosphine)palladium(II) dichloride (abbreviation: Pd(PPh3)2Cl2) was added. The mixture was stirred at 80 °C for 18 hours to initiate a reaction.

[0392] After a predetermined time, the resulting suspension was subjected to suction filtration and washed with water and ethanol. The resulting solid was dissolved in toluene, and the mixture was filtered through a filter aid containing Celite, aluminum oxide, and Celite in that order. Recrystallization was then carried out from a mixed solvent of toluene and hexane to obtain the target compound (2.66 g of a pale yellow solid in 82% yield).

[0393] 2.64 g of the obtained pale yellow solid were purified by sublimation using a train sublimation process. The solid was heated under sublimation purification conditions of 2.6 Pa pressure and 15 ml / min argon flow rate at 315 °C. After sublimation purification, 2.34 g of a pale yellow solid, which was the target compound, were obtained with a recovery rate of 89%. The synthesis scheme for step 3 is shown below.

[0394] The nuclear magnetic resonance ( 1 The analytical results obtained by 1H NMR spectroscopy of the pale yellow solid obtained in step 3 are shown below. The results reveal that 9mDBtBPNfpr was obtained.

[0395] 1 H NMR. δ (CD2Cl2): 7.47-7.51 (m, 2H), 7.60-7.69 (m, 5H), 7.79-7.89 (m, 6H), 8.05 (d, 1H), 8.10-8.11 (m, 2H), 8.18-8.23 (m, 3H), 8.53 (s, 1H), 9.16 (d, 1H), 9.32 (s, 1H). <<Syntheseverfahren von 8BP-4mDBtPBfpm> >

[0396] A method for synthesizing 8-(1,1'-biphenyl-4-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtPBfpm), represented by the structural formula (xiii) of the example, is described. The structure of 8BP-4mDBtPBfpm is shown below. (Synthesis of 8-(1,1'-Biphenyl-4-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine)

[0397] Into a three-necked flask, 1.37 g of 8-chloro-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine, 0.657 g of 4-biphenylboronic acid, 1.91 g of tripotassium phosphate, 30 ml of diglyme, and 0.662 g of t-butanol were placed. The mixture was degassed by stirring under reduced pressure, and the air in the flask was replaced with nitrogen.

[0398] This mixture was heated at 60 °C, to which 23.3 mg of palladium(II) acetate and 66.4 mg of di(1-adamantyl)-n-butylphosphine were added, and the mixture was stirred at 120 °C for 27 hours. Water was added to this reaction solution, suction filtration was carried out, and the resulting residue was washed with water, ethanol, and toluene. This residue was dissolved in heated toluene, and the solution was filtered through a filter aid containing Celite, aluminum oxide, and Celite in that order. The resulting solution was concentrated and dried, and then recrystallized from toluene, affording 1.28 g of a white solid, which was the target compound, in a 74% yield.

[0399] 1.26 g of the white solid were purified by sublimation using a train sublimation process. The solid was heated under sublimation purification conditions of 2.56 Pa pressure and 10 ml / min argon flow rate at 310 °C. After sublimation purification, 1.01 g of a pale yellow solid, the target compound, was obtained with a recovery rate of 80%. The synthesis scheme is shown below.

[0400] The nuclear magnetic resonance ( 1 The analytical results obtained by 1H NMR spectroscopy of the pale yellow solid obtained by the above reaction are shown below. The results reveal that 8BP-4mDBtPBfpm was obtained.

[0401] 1H NMR. δ (CDCl3): 7.39 (t, 1H), 7.47-7.53 (m, 4H), 7.63-7.67 (m, 2H), 7.68 (d, 2H), 7.75 (d, 2H), 7.79-7.83 (m, 4H), 7.87 (d, 1H), 7.98 (d, 1H), 8.02 (d, 1H), 8.23-8.26 (m, 2H), 8.57 (s, 1H), 8.73 (d, 1H), 9.05 (s, 1H), 9.34 (s, 1H). <<Syntheseverfahren von 4Ph-8DBt-2PCCzBfpm> >

[0402] A method for synthesizing 8-(dibenzothiophen-4-yl)-4-phenyl-2-(9'-phenyl-3,3'-bi-9H-carbazol-9-yl)-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4Ph-8DBt-2PCCzBfpm), represented by the structural formula (xix) of the example, is described. The structure of 4Ph-8DBt-2PCCzBfpm is shown below. (Step 1; Synthesis of 2,8-Dichloro-4-phenyl-[1]benzofuro[3,2-d]pyrimidine)

[0403] Into a 500 mL three-necked flask, 10 g (37 mmol) of 2,4,8-trichloro[1]benzofuro[3,2-d]pyrimidine, 4.5 g (371 mmol) of phenylboronic acid, 37 mL of a 2 M aqueous potassium carbonate solution, 180 mL of toluene, and 18 mL of ethanol were added. The mixture in the flask was degassed, and the air in the flask was replaced with nitrogen. 1.3 g (1.8 mmol) of bis(triphenylphosphine)palladium(II) dichloride was added to this mixture, and the mixture was stirred at 80 °C for 16 hours.

[0404] After the predetermined time, the resulting reaction mixture was concentrated, water was added, and the mixture was subjected to suction filtration. The residue was washed with ethanol to obtain a solid. This solid was dissolved in toluene, and the solution was subjected to suction filtration through a filter medium containing celite, aluminum oxide, and celite in that order. The filtrate was concentrated to obtain 11 g of a white solid, the target compound, in 91% yield. The synthesis scheme for step 1 is shown below. (Step 2; Synthesis of 8-chloro-4-phenyl-2-(9'-phenyl-3,3'-bi-9H-carbazol-9-yl)-[1]benzofuro[3,2-d]pyrimidine)

[0405] Into a 300 ml three-necked flask, 5.0 g (16 mmol) of 2,8-dichloro-4-phenyl-[1]benzofuro[3,2-d]pyrimidine, obtained in step 1, 6.5 g (16 mmol) of 9-phenyl-3,3'-bi-9H-carbazole, 3.1 g (32 mmol) of tert-sodium butoxide, and 150 ml of xylene were added, and the air in the flask was replaced with nitrogen. Then, 224 mg (0.64 mmol) of di-tert-butyl(1-methyl-2,2-diphenylcyclopropyl)phosphine (abbreviation: cBRIDP) and 58 mg (0.16 mmol) of allylpalladium(II) chloride dimer were added, and the mixture was heated and stirred at 90 °C for 7 hours.

[0406] Water was added to the resulting reaction mixture, and an aqueous layer was subjected to toluene extraction. The resulting extract solution and an organic layer were combined and washed with a saturated salt solution, and anhydrous magnesium sulfate was added to the organic layer for drying. The resulting mixture was gravity-filtered, and the filtrate was concentrated to obtain a solid. This solid was purified by silica gel column chromatography using a mixed solvent containing toluene and hexane in a 1:1 ratio. The resulting fraction was concentrated to obtain 5.5 g of a yellow solid, which was the target compound, in a 50% yield. The synthesis scheme for step 2 is shown below. (Step 3: Synthesis of 4Ph-8DBt-2PCCzBfpm)

[0407] Into a three-necked flask, 2.25 g (3.3 mmol) of 8-chloro-4-phenyl-2-(9'-phenyl-3,3'-bi-9H-carbazol-9-yl)[1]benzofuro[3,2-d]pyrimidine obtained in step 2, 0.82 g (3.6 mmol) of 4-dibenzothiophenboronic acid, 1.5 g (9.8 mmol) of cesium fluoride and 35 ml of xylene were added, and the air in the flask was replaced with nitrogen.

[0408] The temperature of this mixture was increased to 60 °C, and 60 mg (0.065 mmol) of tris(dibenzylideneacetone)dipalladium(0) and 77 mg (0.2 mmol) of 2'-(dicyclohexylphosphino)acetophenone ethyleneketal were added. The mixture was heated and stirred at 100 °C for 16 hours. Further additions to this mixture were 30 mg (0.032 mmol) of tris(dibenzylideneacetone)dipalladium(0) and 36 mg (0.1 mmol) of 2'-(dicyclohexylphosphino)acetophenone ethyleneketal. The mixture was heated and stirred at 110 °C for 7 hours and then at 120 °C for 7 hours.

[0409] Water was added to the resulting reaction product, the mixture was subjected to suction filtration, and the residue was washed with ethanol. This solid was dissolved in toluene, and the solution was subjected to suction filtration through a filter medium in which celite, aluminum oxide, and celite were arranged in that order. The resulting filtrate was concentrated, and recrystallization from toluene was carried out, affording 1.87 g of a yellow solid, which was the target compound, in a yield of 68%. The synthesis scheme is shown below.

[0410] 0.90 g of the obtained yellow solid were purified by sublimation using a train sublimation process. The solid was heated under sublimation purification conditions at a pressure of 1.58 × 10 -2The Pa value was 400 °C. After sublimation purification, 0.78 g of a yellow solid, which was the target substance, were obtained with a recovery rate of 86%.

[0411] The nuclear magnetic resonance ( 1 The analytical results obtained by 1H NMR spectroscopy of the yellow solid obtained in the above reaction are shown below. The results reveal that 4Ph-8DBt-2PCCzBfpm was obtained.

[0412] 1 H NMR. δ (CDCl3): 7.33 (t, 1H), 7.41-7.53 (m, 7H), 7.59 (t, 1H), 7.62-7.70 (m, 7H), 7.72-7.75 (m, 2H), 7.83 (dd, 1H), 7.87 (dd, 1H), 7.93-7.95 (m, 2H), 8.17 (dd, 1H), 8.23-8.26 (m, 4H), 8.44 (d, 1H), 8.52 (d, 1H), 8.75 (d, 1H), 8.2 (d, 2H), 9.02 (d, 1H), 9.07 (d, 1H). Explanation of reference symbols

[0413] 101: Anode, 102: Cathode, 103: EL layer, 111: Hole injection layer, 112: Hole transport layer, 112-1: First hole transport layer, 112-2: Second hole transport layer, 113: Light-emitting layer, 113-1: Light-emitting region, 114: Electron transport layer, 114-1: Non-light-emitting recombination region, 115: Electron injection layer, 116: Charge generation layer, 117: p-type layer, 118: Electron conduction layer, 119: Electron injection buffer layer, 201: Anode, 202: Cathode, 210: First layer, 211: Second layer, 212: Third layer, 400: Substrate, 401: Anode, 403: EL layer, 404: Cathode, 405: Sealing material, 406: Sealing material, 407: Sealing substrate, 412: Contact point, 420: IC chip, 501: Anode, 502: Cathode, 511: First light-emitting unit, 512: Second light-emitting unit, 513: Charge generation layer, 601: Driver circuit section (source line driver circuit), 602: Pixel section,603: Driver circuit section (gate line driver circuit), 604: Sealing substrate, 605: Sealing material, 607: Space, 608: Conduit, 609: Flexible printed circuit (FPC), 610: Element substrate, 611: Switching FET, 612: Current-controlling FET, 613: Anode, 614: Insulator, 616: EL layer, 617: Cathode, 618: Light-emitting device, 951: Substrate, 952: Electrode, 953: Insulating layer, 954: Separating layer, 955: EL layer, 956: Electrode, 1001: Substrate, 1002: Base insulating film, 1003: Gate insulating film, 1006: Gate electrode, 1007: Gate electrode 1008: Gate electrode, 1020: First interlayer insulating film, 1021: Second interlayer insulating film, 1022: Electrode, 1024W: Anode, 1024R: Anode, 1024G: Anode, 1024B: Anode, 1025: Partition, 1028: EL layer, 1029: Cathode, 1031: Gasket substrate, 1032: Gasket material, 1033: Transparent base material, 1034R: Red color layer, 1034G: Green color layer, 1034B: Blue color layer, 1035: Black matrix, 1036: Cover layer037: third interlayer insulating film, 1040: pixel section, 1041: driver circuit section, 1042: peripheral section, 2001: housing, 2002: light source, 2100: robot, 2110: arithmetic device, 2101: illuminance sensor, 2102: microphone, 2103: upper camera, 2104: speaker, 2105: display, 2106: lower camera, 2107: obstacle sensor, 2108: movement mechanism, 3001: lighting device, 5000: housing, 5001: display section, 5002: display section, 5003: speaker, 5004: LED lamp, 5006: connection port, 5007: sensor, 5008: microphone, 5012: support 5013: Earpiece, 2100: Cleaning robot, 5101: Display, 5102: Camera, 5103: Brush, 5104: Control button, 5150: Portable information terminal, 5151: Housing, 5152: Display area, 5153: Bending section, 5120: Dust, 5200: Display area, 5201: Display area, Perforated transport layer, 5202: Display area, 5203: Display area, 7101: Housing, 7103: Display section, 7105: Stand, 7107: Display section7109: Control button, 7110: Remote control, 7201: Main part, 7202: Housing, 7203: Display section, 7204: Keyboard, 7205: External connection port, 7206: Pointing device, 7210: Second display section, 7401: Housing, 7402: Display section, 7403: Control knob, 7404: External connection port, 7405: Speaker, 7406: Microphone, 9310: Portable information terminal, 9311: Display panel, 9313: Joint, 9315: Housing.

Claims

[1] Light-emitting device comprising: an anode; a cathode; and an EL layer between the anode and the cathode, wherein the EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer and a fourth layer in that order from an anode side, where the first layer is in contact with the anode, where the fourth layer is in contact with the light-emitting layer, wherein the first layer contains a first organic compound and a second organic compound, the second layer contains a third organic compound, the third layer contains a fourth organic compound, wherein the light-emitting layer includes a fifth organic compound and a sixth organic compound, the fourth layer contains a seventh organic compound and an eighth substance, wherein the first organic compound has an electron-accepting property with respect to the second organic compound, where the fifth organic compound is an emission center substance, where the HOMO level of the second organic compound is higher than or equal to -5.7 eV and lower than or equal to -5.4 eV, and the eighth substance is an organic complex. [2] Light-emitting device according to claim 1, where the difference between the HOMO level of the second organic compound and the HOMO level of the third organic compound is less than or equal to 0.2 eV, and where the HOMO level of the third organic compound is equal to or lower than the HOMO level of the second organic compound. [3] Light-emitting device comprising: an anode; a cathode; and an EL layer between the anode and the cathode, wherein the EL layer comprises a first layer, a second layer, a third layer, a light-emitting layer and a fourth layer in that order from an anode side, where the first layer is in contact with the anode, where the fourth layer is in contact with the light-emitting layer, wherein the first layer contains a first organic compound and a second organic compound, the second layer contains a third organic compound, the third layer contains a fourth organic compound, wherein the light-emitting layer includes a fifth organic compound and a sixth organic compound, the fourth layer contains a seventh organic compound and an eighth substance, wherein the first organic compound has an electron-accepting property with respect to the second organic compound, wherein the second organic compound contains a first hole transport scaffold, wherein the third organic compound contains a second hole transport scaffold, wherein the fourth organic compound contains a third hole transport scaffold, where the fifth organic compound is an emission center substance, where the HOMO level of the second organic compound is higher than or equal to -5.7 eV and lower than or equal to -5.4 eV, wherein the first hole transport scaffold, the second hole transport scaffold and the third hole transport scaffold are each independently a carbazole scaffold, a dibenzofuran scaffold, a dibenzothiophene scaffold or an anthracene scaffold, and the eighth substance is an organic complex. [4] Light-emitting device according to claim 1 or 3, wherein the seventh organic compound contains an anthracene skeleton. [5] Light-emitting device according to claim 1 or 3, wherein the eighth substance is the organic complex of an alkali metal or an alkaline earth metal. [6] Light-emitting device according to claim 1 or 3, wherein a decay curve showing a change in the luminance of a light emission obtained when a constant current is supplied to the light-emitting device has a local maximum value. [7] Light-emitting device according to claim 6, wherein the decay curve has a section in which the luminance exceeds 100%. [8] Light-emitting device according to claim 1 or 3, wherein the seventh organic compound comprises an anthracene framework and a heterocyclic framework. [9] Light-emitting device according to claim 1 or 3, wherein the electron mobility of the seventh organic compound is lower than the electron mobility of the sixth organic compound. [10] Light-emitting device according to claim 1 or 3, wherein the difference between HOMO levels of the third organic compound and the fourth organic compound is less than or equal to 0.2 eV. [11] Light-emitting device according to claim 1 or 3, wherein a HOMO level of the fourth organic compound is equal to or lower than a HOMO level of the third organic compound. [12] Light-emitting device according to claim 1 or 3, wherein the second organic compound contains a dibenzofuran skeleton. [13] Light-emitting device according to claim 1 or 3, wherein the second organic compound and the third organic compound are the same substance. [14] Light-emitting device according to claim 1 or 3, wherein the fifth organic compound is a blue fluorescent material. [15] Electronic device comprising the light-emitting device according to claim 1 or 3 and at least one element selected from the group consisting of sensor, control knob, loudspeaker and microphone. [16] Lighting device comprising the light-emitting device according to claim 1 or 3 and a housing.

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