Light-emitting element, comprising an organometallic complex light-emitting material, a light-emitting device and an electronic device comprising the light-emitting element
View Patent ↗To provide a light-emitting element with high light emission efficiency, a long lifetime, and reduced driving voltage. To provide a light-emitting element including an anode, a cathode, and a plurality of light-emitting layers which are in contact with each other so that a stacked structure is formed, between the anode and the cathode, in which the plurality of light-emitting layers are formed with a first light-emitting layer which is close to the anode and a second light-emitting layer which is close to the cathode, the first light-emitting layer and the second light-emitting layer each include a host material, a hole-transporting material, and a light-emitting material, and the concentration of the hole-transporting material in the first light-emitting layer is higher than the concentration of the hole-transporting material in the second light-emitting layer.
1. A light-emitting element comprising:
an anode;
a first light-emitting layer over the anode;
a second light-emitting layer over the first light-emitting layer; and
a cathode over the second light-emitting layer,
wherein each of the first light-emitting layer and the second light-emitting layer comprises a host material, a hole-transporting material, and a light-emitting material,
wherein a mass ratio of the hole-transporting material to the host material in the first light-emitting layer is greater than or equal to 0.25 and less than or equal to 0.5, and
wherein a mass ratio of the hole-transporting material to the host material in the second light-emitting layer is equal to 0.1.
2. The light-emitting element according to claim 1 , wherein the host material has an electron-transporting property.
3. The light-emitting element according to claim 1 , wherein the hole-transporting material is an aromatic amine compound or a carbazole derivative.
4. The light-emitting element according to claim 1 , wherein the light-emitting material comprises iridium.
5. A light-emitting element comprising:
an anode;
a hole-injection layer over the anode;
a hole-transporting layer over the hole-injection layer;
a first light-emitting layer over the hole-transporting layer;
a second light-emitting layer over the first light-emitting layer; and
a cathode over the second light-emitting layer,
wherein each of the first light-emitting layer and the second light-emitting layer comprises a host material, a hole-transporting material, and a light-emitting material,
wherein each of the hole-injection layer and the hole-transporting layer comprises the hole-transporting material,
wherein the host material is a heteroaromatic compound or a metal complex, and has an electron-transporting property,
wherein the hole-transporting material is a carbazole derivative,
wherein the light-emitting material is a compound emitting phosphorescence,
wherein a mass ratio of the hole-transporting material to the host material in the first light-emitting layer is greater than or equal to 0.25 and less than or equal to 0.5, and
wherein a mass ratio of the hole-transporting material to the host material in the second light-emitting layer is equal to 0.1.
6. The light-emitting element according to claim 1 , further comprising:
an electron-transporting layer between the second light-emitting layer and the cathode,
wherein the second light-emitting layer is in contact with the electron-transporting layer.
7. A light-emitting device comprising the light-emitting element according to claim 1 .
8. An electronic device comprising the light-emitting device according to claim 7 .
9. The light-emitting element according to claim 1 , wherein the hole-transporting layer further comprises a transition metal oxide.
10. A lighting device comprising the light-emitting element according to claim 1 .
11. A light-emitting element comprising:
an anode;
a cathode;
a first light-emitting layer and a second light-emitting layer between the anode and the cathode;
a hole-injection layer between the anode and the first light-emitting layer; and
a hole-transporting layer between the hole-injection layer and the first light-emitting layer,
wherein each of the first light-emitting layer and the second light-emitting layer comprises a host material, a hole-transporting material, and a light-emitting material,
wherein each of the hole-injection layer and the hole-transporting layer comprises the hole-transporting material,
wherein the host material is a heteroaromatic compound or a metal complex, and has an electron-transporting property,
wherein the hole-transporting material is a carbazole derivative,
wherein the light-emitting material is a compound emitting phosphorescence,
wherein a mass ratio of the hole-transporting material to the host material in the first light-emitting layer is greater than or equal to 0.25 and less than or equal to 0.5, and
wherein a mass ratio of the hole-transporting material to the host material in the second light-emitting layer is equal to 0.1.
12. The light-emitting element according to claim 11 , further comprising:
an electron-transporting layer between the second light-emitting layer and the cathode,
wherein the second light-emitting layer is in contact with the electron-transporting layer.
13. A light-emitting device comprising the light-emitting element according to claim 11 .
14. An electronic device comprising the light-emitting device according to claim 13 .
15. The light-emitting element according to claim 11 , wherein the hole-transporting layer further comprises a transition metal oxide.
16. A lighting device comprising the light-emitting element according to claim 11 .
17. A light-emitting element comprising:
an anode;
a cathode; and
a first light-emitting layer and a second light-emitting layer between the anode and the cathode,
wherein each of the first light-emitting layer and the second light-emitting layer comprises a host material, a hole-transporting material, and a light-emitting material,
wherein the host material is one of bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) and 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]carbazole,
wherein the hole-transporting material is one of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl and 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine,
wherein the light-emitting material is one of (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III), and bis{2-(4-fluorophenyl)-3,5-dimethylpyrazinato}(picolinato) iridium(III),
wherein a mass ratio of the hole-transporting material to the host material in the first light-emitting layer is greater than or equal to 0.25 and less than or equal to 0.5, and
wherein a mass ratio of the hole-transporting material to the host material in the second light-emitting layer is equal to 0.1.
18. The light-emitting element according to claim 17 , further comprising:
an electron-transporting layer between the second light-emitting layer and the cathode,
wherein the second light-emitting layer is in contact with the electron-transporting layer.
19. A light-emitting device comprising the light-emitting element according to claim 17 .
20. An electronic device comprising the light-emitting device according to claim 19 .
21. The light-emitting element according to claim 17 , further comprising:
a hole-transporting layer between the first light-emitting layer and the anode,
wherein the first light-emitting layer is in contact with the hole-transporting layer.
22. The light-emitting element according to claim 21 , wherein the hole-transporting layer comprises a hole-transporting compound and a transition metal oxide.
23. A lighting device comprising the light-emitting element according to claim 17 .