US-12622128-B2 - Light-emitting device, light-emitting apparatus, electronic device, and lighting device

Abstract

A light-emitting device including an EL layer including a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in this order from the anode side is provided. The first layer contains a first organic compound and a second organic compound. The light-emitting layer contains a sixth organic compound. The fourth layer contains a seventh organic compound. The first organic compound exhibits an electron-accepting property with respect to the second organic compound. A HOMO level of the second organic compound is higher than or equal to −5.7 eV and lower than or equal to −5.2 eV. A HOMO level of the third organic compound is equal to or deeper than the HOMO level of the second organic compound. A difference between the HOMO levels of the second organic compound and the third organic compound is less than or equal to 0.2 eV.

Inventors

• Satoshi Seo
• Tsunenori Suzuki
• Takumu Okuyama
• Yusuke TAKITA
• Naoaki HASHIMOTO
• Hiromi Seo

Assignees

• SEMICONDUCTOR ENERGY LABORATORY CO., LTD.

Dates

Publication Date

20260505

Application Date

20190920

Priority Date

20180926

Claims (20)

1. 1 . A 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 this order from an anode side, wherein the first layer is in contact with the anode, wherein the first layer comprises a first organic compound and a second organic compound, wherein the second layer comprises a third organic compound, wherein the third layer comprises a fourth organic compound, wherein the light-emitting layer comprises a fifth organic compound and a sixth organic compound, wherein the fourth layer comprises a seventh organic compound, wherein the first organic compound exhibits an electron-accepting property with respect to the second organic compound, wherein the second organic compound and the third organic compound are the same substance, wherein the fifth organic compound is an emission center substance, wherein the sixth organic compound has a heterocyclic skeleton, wherein a HOMO level of the second organic compound is higher than or equal to −5.7 eV and lower than or equal to −5.2 eV, wherein electron mobility of the seventh organic compound when a square root of electric field strength [V/cm] is 600 is higher than or equal to 1×10 −7 cm 2 /Vs and lower than or equal to 5 ×10 −5 cm 2 /Vs, wherein a HOMO level of the fourth organic compound is deeper than a HOMO level of the third organic compound, wherein a difference between the HOMO level of the third organic compound and the HOMO level of the fourth organic compound is less than or equal to 0.2 eV, wherein a difference between the HOMO level of the fourth organic compound and a HOMO level of the sixth organic compound is less than 0.2 eV, and wherein the fourth organic compound is a compound having an aromatic amine skeleton having a substituent that includes a dibenzofuran ring, and a nitrogen directly bonded to an aromatic group in the aromatic amine skeleton is not in a carbazolyl group.
2. 2 . The light-emitting device according to claim 1 , wherein the second organic compound has a first hole-transport skeleton, wherein the third organic compound has a second hole-transport skeleton, wherein the fourth organic compound has a third hole-transport skeleton, and wherein each of the first hole-transport skeleton, the second hole-transport skeleton, and the third hole-transport skeleton is independently any one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton.
3. 3 . The light-emitting device according to claim 1 , wherein the sixth organic compound further has an anthracene skeleton.
4. 4 . The light-emitting device according to claim 1 , wherein the second organic compound has a dibenzofuran skeleton.
5. 5 . The light-emitting device according to claim 1 , wherein the seventh organic compound has a quinoxaline skeleton.
6. 6 . The light-emitting device according to claim 1 , wherein the fifth organic compound is a blue fluorescent material.
7. 7 . A light-emitting apparatus comprising: the light-emitting device according to claim 1 ; and a transistor, or a substrate.
8. 8 . A 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 this order from an anode side, wherein the first layer is in contact with the anode, wherein the first layer comprises a first organic compound and a second organic compound, wherein the second layer comprises a third organic compound, wherein the third layer comprises a fourth organic compound, wherein the light-emitting layer comprises a fifth organic compound and a sixth organic compound, wherein the fourth layer comprises a seventh organic compound, wherein the first organic compound exhibits an electron-accepting property with respect to the second organic compound, wherein the second organic compound and the third organic compound are the same substance, wherein the fifth organic compound is an emission center substance, wherein the sixth organic compound has a heterocyclic skeleton, wherein a HOMO level of the second organic compound is higher than or equal to −5.7 eV and lower than or equal to −5.2 eV, wherein a LUMO level of the sixth organic compound is shallower than a LUMO level of the seventh organic compound, wherein a difference between the LUMO level of the sixth organic compound and the LUMO level of the seventh organic compound is greater than or equal to 0.1 eV and less than or equal to 0.3 eV, wherein a HOMO level of the fourth organic compound is deeper than a HOMO level of the third organic compound, wherein a difference between the HOMO level of the third organic compound and the HOMO level of the fourth organic compound is less than or equal to 0.2 eV, wherein a difference between the HOMO level of the fourth organic compound and a HOMO level of the sixth organic compound is less than 0.2 eV, and wherein the fourth organic compound is a compound having an aromatic amine skeleton having a substituent that includes a dibenzofuran ring, and a nitrogen directly bonded to an aromatic group in the aromatic amine skeleton is not in a carbazolyl group.
9. 9 . The light-emitting device according to claim 8 , wherein the second organic compound has a first hole-transport skeleton, wherein the third organic compound has a second hole-transport skeleton, wherein the fourth organic compound has a third hole-transport skeleton, and wherein each of the first hole-transport skeleton, the second hole-transport skeleton, and the third hole-transport skeleton is independently any one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton.
10. 10 . The light-emitting device according to claim 8 , wherein the sixth organic compound further has an anthracene skeleton.
11. 11 . The light-emitting device according to claim 8 , wherein the second organic compound has a dibenzofuran skeleton.
12. 12 . The light-emitting device according to claim 8 , wherein the seventh organic compound has a quinoxaline skeleton.
13. 13 . The light-emitting device according to claim 8 , wherein the fifth organic compound is a blue fluorescent material.
14. 14 . A light-emitting apparatus comprising: the light-emitting device according to claim 8 ; and a transistor, or a substrate.
15. 15 . A 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 this order from an anode side, wherein the first layer is in contact with the anode, wherein the first layer comprises a first organic compound and a second organic compound, wherein the second layer comprises a third organic compound, wherein the third layer comprises a fourth organic compound, wherein the light-emitting layer comprises a fifth organic compound and a sixth organic compound, wherein the fourth layer comprises a seventh organic compound, wherein the first organic compound exhibits an electron-accepting property with respect to the second organic compound, wherein the second organic compound and the third organic compound are the same substance, wherein the fifth organic compound is an emission center substance, wherein the sixth organic compound has a heterocyclic skeleton, wherein a HOMO level of the second organic compound is higher than or equal to −5.7 eV and lower than or equal to −5.2 eV, wherein the seventh organic compound is a x-electron deficient heteroaromatic compound comprising a triazine skeleton, wherein a LUMO level of the sixth organic compound is shallower than a LUMO level of the seventh organic compound, wherein a difference between the LUMO level of the sixth organic compound and the LUMO level of the seventh organic compound is greater than or equal to 0.1 eV and less than or equal to 0.3 eV, wherein a HOMO level of the fourth organic compound is deeper than a HOMO level of the third organic compound, wherein a difference between the HOMO level of the third organic compound and the HOMO level of the fourth organic compound is less than or equal to 0.2 eV, wherein a difference between the HOMO level of the fourth organic compound and a HOMO level of the sixth organic compound is less than 0.2 eV, and wherein the fourth organic compound is a compound having an aromatic amine skeleton having a substituent that includes a dibenzofuran ring, and a nitrogen directly bonded to an aromatic group in the aromatic amine skeleton is not in a carbazolyl group.
16. 16 . The light-emitting device according to claim 15 , wherein the second organic compound has a first hole-transport skeleton, wherein the third organic compound has a second hole-transport skeleton, wherein the fourth organic compound has a third hole-transport skeleton, and wherein each of the first hole-transport skeleton, the second hole-transport skeleton, and the third hole-transport skeleton is independently any one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton.
17. 17 . The light-emitting device according to claim 15 , wherein the sixth organic compound further has an anthracene skeleton.
18. 18 . The light-emitting device according to claim 15 , wherein a difference between the HOMO level of the third organic compound and a HOMO level of the fourth organic compound is less than or equal to 0.2 eV.
19. 19 . The light-emitting device according to claim 15 , wherein the second organic compound has a dibenzofuran skeleton.
20. 20 . The light-emitting device according to claim 15 , wherein the seventh organic compound has a quinoxaline skeleton.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a U.S. National Phase Application under 35 U.S.C. § 371 of International Application PCT/IB2019/057955, filed on Sep. 20, 2019, and claims the benefit of foreign priority applications filed in Japan on Sep. 26, 2018, as Application No. 2018-180795, on Oct. 10, 2018, as Application No. 2018-191552, and on Nov. 29, 2018, as Application No. 2018-224074, all of which are incorporated by reference. TECHNICAL FIELD Embodiments of the present invention relate to a light-emitting device, a display module, a lighting module, a display device, a light-emitting apparatus, an electronic device, and a lighting device. Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. One embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a liquid crystal display device, a light-emitting apparatus, a lighting device, a power storage device, a memory device, an imaging device, a driving method thereof, and a manufacturing method thereof. BACKGROUND ART Light-emitting devices (organic EL elements) including organic compounds and utilizing electroluminescence (EL) have been put to more practical use. In the basic structure of such light-emitting devices, an organic compound layer containing a light-emitting material (an EL layer) is interposed between a pair of electrodes. Carriers are injected by application of voltage to the element, and recombination energy of the carriers is used, whereby light emission can be obtained from the light-emitting material. Since such light-emitting devices are of self-light-emitting type, light-emitting devices have advantages over liquid crystal displays when used as pixels of a display in that visibility of pixels is high and backlight is not required. Displays including such light-emitting devices are also highly advantageous in that they can be thin and lightweight. Moreover, such a light-emitting devices also have a feature that response speed is extremely fast. Since light-emitting layers of such light-emitting devices can be successively formed two-dimensionally, planar light emission can be achieved. This feature is difficult to realize with point light sources typified by incandescent lamps and LEDs or linear light sources typified by fluorescent lamps. Thus, light-emitting devices also have great potential as planar light sources, which can be applied to lighting devices and the like. Displays or lighting devices including light-emitting devices can be suitably used for a variety of electronic devices as described above, and research and development of light-emitting devices have progressed for higher efficiency or longer lifetimes. In a structure disclosed in Patent Document 1, a hole-transport material whose HOMO level is 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. Although the characteristics of light-emitting devices have been improved remarkably, advanced requirements for various characteristics including efficiency and durability are not yet satisfied. REFERENCE [Patent Document] [Patent Document 1] PCT International Publication No. WO2011/065136 DISCLOSURE OF INVENTION An object of one embodiment of the present invention is to provide a novel light-emitting device. Another object of one embodiment of the present invention is to provide a light-emitting device with high emission efficiency. Another object of one embodiment of the present invention is to provide a light-emitting device with a long lifetime. Another object of one embodiment of the present invention is to provide a light-emitting device with low driving voltage. Another object of one embodiment of the present invention is to provide a light-emitting apparatus, an electronic device, and a display device each having high reliability. Another object of one embodiment of the present invention is to provide a light-emitting apparatus, an electronic device, and a display device each with low power consumption. It is only necessary that at least one of the above-described objects be achieved in the present invention. One embodiment of the present invention is a light-emitting device including an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer includes a light-emitting layer. A decay curve showing a change in luminance of light emission obtained when a constant current is supplied to the light-emitting device has a maximum value. Another embodiment of th