Light-Emitting Device

• US 20120217487A1
• Filed: 02/27/2012
• Published: 08/30/2012
• Est. Priority Date: 02/28/2011
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei, Seo, Satoshi, Ohsawa, Nobuharu, Shitagaki, Satoko, Inoue, Hideko, Kadoma, Hiroshi, Osaka, Harue, Suzuki, Kunihiko, Takemura, Yasuhiko
• Granted Patent: US 9,929,350 B2
• Time in Patent Office: Days
• US Class Current: 257/40
• CPC Class Codes: H10K 2101/30 Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values
• CPC Class Codes: H10K 2101/90 Multiple hosts in the emissive layer
• CPC Class Codes: H10K 85/631 Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
• CPC Class Codes: H10K 85/654 comprising only nitrogen as heteroatom H10K85/652 takes precedence

Abstract

A light-emitting element includes a light-emitting layer including a guest, an n-type host and a p-type host between a pair of electrodes, where the difference between the energy difference between a triplet excited state and a ground state of the n-type host (or p-type host) and the energy difference between a triplet excited state and a ground state of the guest is 0.15 eV or more. Alternatively, in such a light-emitting element, the LUMO level of the n-type host is higher than the LUMO level of the guest by 0.1 eV or more, or the HOMO level of the p-type host is lower than the HOMO level of the guest by 0.1 eV or more.

Claims

1. A light-emitting element comprising:

a pair of electrodes; and

a light-emitting layer between the pair of electrodes, the light-emitting layer comprising;

a phosphorescent compound;

a first organic compound having an electron-transport property superior to a hole-transport property; and

a second organic compound having a hole-transport property superior to an electron-transport property,

wherein an energy difference between a triplet excited state and a ground state of the first organic compound and an energy difference between a triplet excited state and a ground state of the second organic compound are both higher than an energy difference between a triplet excited state and a ground state of the phosphorescent compound by 0.15 eV or more.

2. The light-emitting element according to claim 1, wherein an exciplex is formed from the first organic compound and the second organic compound.

3. The light-emitting element according to claim 2, wherein excitation energy of the exciplex is transferred to the phosphorescent compound, so that the phosphorescent compound emits phosphorescence.

4. The light-emitting element according to claim 1, wherein an exciplex is formed from an anion of the first organic compound and a cation of the second organic compound.

5. The light-emitting element according to claim 4, wherein excitation energy of the exciplex is transferred to the phosphorescent compound, so that the phosphorescent compound emits phosphorescence.

6. The light-emitting element according to claim 1, wherein at least one of the first organic compound and the second organic compound is a fluorescent compound.

7. The light-emitting element according to claim 1, wherein the phosphorescent compound is an organometallic complex.

8. A light-emitting element comprising:

a pair of electrodes; and

a light-emitting layer between the pair of electrodes, the light-emitting layer comprising;

a phosphorescent compound;

a first organic compound having an electron-transport property superior to a hole-transport property; and

a second organic compound having a hole-transport property superior to an electron-transport property,

wherein a lowest unoccupied molecular orbital (LUMO) level of the first organic compound is higher than a LUMO level of the phosphorescent compound by 0.1 eV or more.

9. The light-emitting element according to claim 8, wherein an exciplex is formed from the first organic compound and the second organic compound.

10. The light-emitting element according to claim 9, wherein excitation energy of the exciplex is transferred to the phosphorescent compound, so that the phosphorescent compound emits phosphorescence.

11. The light-emitting element according to claim 8, wherein an exciplex is formed from an anion of the first organic compound and a cation of the second organic compound.

12. The light-emitting element according to claim 11, wherein excitation energy of the exciplex is transferred to the phosphorescent compound, so that the phosphorescent compound emits phosphorescence.

13. The light-emitting element according to claim 8, wherein at least one of the first organic compound and the second organic compound is a fluorescent compound.

14. The light-emitting element according to claim 8, wherein the phosphorescent compound is an organometallic complex.

15. A light-emitting element comprising:

a pair of electrodes; and

a light-emitting layer between the pair of electrodes, the light-emitting layer comprising;

a phosphorescent compound;

a first organic compound having an electron-transport property superior to a hole-transport property; and

a second organic compound having a hole-transport property superior to an electron-transport property,

wherein a highest occupied molecular orbital (HOMO) level of the second organic compound is lower than a HOMO level of the phosphorescent compound by 0.1 eV more.

16. The light-emitting element according to claim 15, wherein an exciplex is formed from the first organic compound and the second organic compound.

17. The light-emitting element according to claim 16, wherein excitation energy of the exciplex is transferred to the phosphorescent compound, so that the phosphorescent compound emits phosphorescence.

18. The light-emitting element according to claim 15, wherein an exciplex is formed from an anion of the first organic compound and a cation of the second organic compound.

19. The light-emitting element according to claim 18, wherein excitation energy of the exciplex is transferred to the phosphorescent compound, so that the phosphorescent compound emits phosphorescence.

20. The light-emitting element according to claim 15, wherein at least one of the first organic compound and the second organic compound is a fluorescent compound.

21. The light-emitting element according to claim 15, wherein the phosphorescent compound is an organometallic complex.