Light-emitting device
地域：
Sakai
摘要
A light-emitting device includes an HTL including a metal chalcogenide between an anode and an EML, with an IL including an organic material at least between the HTL and the EML. A distance between the HTL and the EML in a light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength is greater than a distance between the HTL and the EML in each of the other light-emitting elements.
說明書
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The disclosure relates to a light-emitting device.
Shen, Huaibin, et al., “High-Efficiency, Low Turn-on Voltage Blue-Violet Quantum-Dot-Based Light-Emitting Diodes,” Nano Lett., 2015, 15, 1211-1216 discloses that, in a light-emitting element that uses blue quantum dots in a light-emitting layer and organic materials in a hole injection layer and a hole transport layer, a quantum efficiency can be improved by replacing ligands of the blue quantum dots with shorter ligands.
Further, Wang Ting et al., “Influence of Shell Thickness on the Performance of NiO-Based All-Inorganic Quantum Dot Light-Emitting Diodes,” ACS Appl. Mater. Interfaces, 2018, 10, 14894-14900 discloses that, in a light-emitting element that uses green quantum dots in a light-emitting layer and nickel oxide (NiO) in a hole transport layer, light emission quenching and device performance degradation can be suppressed by increasing a thickness of shells of the green quantum dots.
權(quán)利要求
The invention claimed is:1. A light-emitting device comprising:a plurality of types of light-emitting elements each having a light emission peak wavelength in a different wavelength band, wherein the plurality of types of light-emitting elements each include, in this order, an anode, a light-emitting layer including quantum dots, and a cathode, a layer having hole transport properties and including a metal chalcogenide being between the anode and the light-emitting layer, and an intermediate layer including an organic material being between the light-emitting layer and at least the layer including the metal chalcogenide of, among the plurality of types of light-emitting elements, a light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength, and a distance between the light-emitting layer and the layer including the metal chalcogenide of, among the plurality of types of light-emitting elements, the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength is greater than a distance between the light-emitting layer and the layer including the metal chalcogenide of each of the other light-emitting elements, wherein the intermediate layer is provided between the light-emitting layer and the layer including the metal chalcogenide in each of the plurality of types of light-emitting elements. 2. The light-emitting device according to claim 1 ,wherein the metal chalcogenide is at least one type selected from the group consisting of nickel oxide, copper oxide, and copper sulfide. 3. The light-emitting device according to claim 1 ,wherein the intermediate layer is an insulating layer. 4. The light-emitting device according to claim 3 ,wherein the distance between the light-emitting layer and the layer including the metal chalcogenide of the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength is within a range from 0.5 nm to 12.5 nm. 5. The light-emitting device according to claim 3 ,wherein a difference between the distance between the light-emitting layer and the layer including the metal chalcogenide of the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength and the distance between the light-emitting layer and the layer including the metal chalcogenide of each of the other light-emitting elements is within a range from 0.5 nm to 12.5 nm. 6. The light-emitting device according to claim 3 ,wherein the insulating layer is composed of at least one type of insulating material selected from the group consisting of polymethyl methacrylate, polyvinyl pyrrolidone, and poly[(9,9-bis(3′-(N,N-dimethylamino) propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)]. 7. The light-emitting device according to claim 1 ,wherein the layer including the metal chalcogenide is a hole injection layer, and the intermediate layer is a hole transport layer. 8. The light-emitting device according to claim 7 ,wherein the distance between the light-emitting layer and the layer including the metal chalcogenide of the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength is within a range from 30.5 nm to 60 nm. 9. The light-emitting device according to claim 7 ,wherein the difference between the distance between the light-emitting layer and the layer including the metal chalcogenide of the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength and the distance between the light-emitting layer and the layer including the metal chalcogenide of each of the other light-emitting elements is within a range from 0.5 nm to 30 nm. 10. The light-emitting device according to claim 7 ,wherein the hole transport layer includes at least one type of organic hole transport material selected from the group consisting of poly(N-vinylcarbazole) and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-4-sec-butylphenyl))diphenylamine)]. 11. The light-emitting device according to claim 1 ,wherein the quantum dots of the plurality of types of light-emitting elements each include a core and a shell covering the core, and a thickness of the shell of the quantum dots of the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength is thinner than a thickness of the shell of the quantum dots of each of the other light-emitting elements. 12. The light-emitting device according to claim 1 ,wherein the light-emitting layer of each of the plurality of types of light-emitting elements includes a ligand adsorbed on a surface of each of the quantum dots, and a length of the ligand in the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength is shorter than a length of the ligand in each of the other light-emitting elements. 13. The light-emitting device according to claim 1 ,wherein the plurality of types of light-emitting elements each include an electron transport layer between the cathode and the light-emitting layer, and a material of the electron transport layer in the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength is the same as a material of the electron transport layer in at least a portion of light-emitting elements of the other light-emitting elements. 14. The light-emitting device according to claim 1 ,wherein a level of a conduction band lower end of the light-emitting layer in the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength is shallower than a level of a conduction band lower end of the light-emitting layer of each of the other light-emitting elements. 15. The light-emitting device according to claim 1 ,wherein the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength is a light-emitting element that emits blue light, and the other light-emitting elements are a light-emitting element that emits red light and a light-emitting element that emits green light. 16. A light-emitting device comprising:a plurality of types of light-emitting elements each having a light emission peak wavelength in a different wavelength band, wherein the plurality of types of light-emitting elements each include, in this order, an anode, a light-emitting layer including quantum dots, and a cathode, a layer having hole transport properties and including a metal chalcogenide being between the anode and the light-emitting layer, and an intermediate layer including an organic material being between the light-emitting layer and at least the layer including the metal chalcogenide of, among the plurality of types of light-emitting elements, a light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength, and a distance between the light-emitting layer and the layer including the metal chalcogenide of, among the plurality of types of light-emitting elements, the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength is greater than a distance between the light-emitting layer and the layer including the metal chalcogenide of each of the other light-emitting elements, wherein the intermediate layer is an insulating layer. 17. The light-emitting device according to claim 16 ,wherein the distance between the light-emitting layer and the layer including the metal chalcogenide of the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength is within a range from 0.5 nm to 12.5 nm. 18. The light-emitting device according to claim 16 ,wherein a difference between the distance between the light-emitting layer and the layer including the metal chalcogenide of the light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength and the distance between the light-emitting layer and the layer including the metal chalcogenide of each of the other light-emitting elements is within a range from 0.5 nm to 12.5 nm. 19. The light-emitting device according to claim 16 ,wherein the insulating layer is composed of at least one type of insulating material selected from the group consisting of polymethyl methacrylate, polyvinyl pyrrolidone, and poly[(9,9-bis(3′-(N,N-dimethylamino) propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)].
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