LIGHT-EMITTING ELEMENT, LIGHT-EMITTING DEVICE, ELECTRONIC DEVICE, AND LIGHTING DEVICE

• US 20140061604A1
• Filed: 03/12/2013
• Published: 03/06/2014
• Est. Priority Date: 04/06/2012
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: SEO, Hiromi, SHITAGAKI, Satoko, SEO, Satoshi, USHIKUBO, Takahiro, SASAKI, Toshiki, UESAKA, Shogo
• Granted Patent: US 9,391,289 B2
• Time in Patent Office: Days
• US Class Current: 257/40
• CPC Class Codes: C07F 15/0033 Iridium compounds
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• CPC Class Codes: C09K 2211/1007 Non-condensed systems
• CPC Class Codes: C09K 2211/1044 containing two nitrogen atoms as heteroatoms
• CPC Class Codes: C09K 2211/185 of the platinum group, i.e. Os, Ir, Pt, Ru, Rh or Pd
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 2101/27 Combination of fluorescent and phosphorescent emission
• CPC Class Codes: H10K 2101/40 Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers
• CPC Class Codes: H10K 50/00 Organic light-emitting devices integrated devices or assemblies of multiple devices H10K59/00, H10K65/00; organic semiconductor lasers H01S5/36
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/121 for assisting energy transfer, e.g. sensitization
• CPC Class Codes: H10K 50/13 comprising stacked EL layers within one EL unit
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair
• CPC Class Codes: H10K 59/30 Devices specially adapted for multicolour light emission
• CPC Class Codes: H10K 59/32 Stacked devices having two or more layers, each emitting at different wavelengths
• CPC Class Codes: H10K 59/876 comprising a resonant cavity structure, e.g. Bragg reflector pair
• CPC Class Codes: H10K 85/342 comprising iridium
• CPC Class Codes: H10K 85/611 Charge transfer complexes
• CPC Class Codes: H10K 85/615 Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
• CPC Class Codes: H10K 85/622 containing four rings, e.g. pyrene
• CPC Class Codes: H10K 85/626 : containing more than one polycyclic condensed aromatic rings, e.g. bis-anthracene
• 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 85/633 : comprising polycyclic condensed aromatic hydrocarbons as substituents on the nitrogen atom
• CPC Class Codes: H10K 85/636 : comprising heteroaromatic hydrocarbons as substituents on the nitrogen atom
• CPC Class Codes: H10K 85/6572 : comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole
• CPC Class Codes: H10K 85/6576 : comprising only sulfur in the heteroaromatic polycondensed ring system, e.g. benzothiophene

Abstract

A light-emitting element having high external quantum efficiency is provided. A light-emitting element having a long lifetime is provided. A light-emitting layer is provided between a pair of electrodes. The light-emitting layer is a stack of a first light-emitting layer, which contains a first phosphorescent compound, a first organic compound having an electron-transport property, and a second organic compound having a hole-transport property and is provided on the anode side, and a second light-emitting layer, which contains at least a second phosphorescent compound and the first organic compound having an electron-transport property. A combination of the first organic compound and the second organic compound forms an exciplex.

Claims

1. A light-emitting device comprising:

a first light-emitting layer over an anode, the first light-emitting layer comprising a first phosphorescent compound, a first organic compound having an electron transport property, and a second organic compound having a hole-transport property;

a second light-emitting layer over the first light-emitting layer, the second light-emitting layer comprising a second phosphorescent compound and the first organic compound; and

a cathode over the second light-emitting layer,

wherein an emission spectrum of an exciplex of the first organic compound and the second organic compound overlaps with an absorption spectrum of the first phosphorescent compound.

2. The light-emitting device according to claim 1, wherein the first phosphorescent compound is different from the second phosphorescent compound.

3. The light-emitting device according to claim 2, wherein light emitted from the first light-emitting layer has a shorter wavelength than light emitted from the second light-emitting layer.

4. The light-emitting device according to claim 1, wherein a peak of the emission spectrum of the exciplex has a longer wavelength than a peak of the absorption spectrum of the first phosphorescent compound.

5. The light-emitting device according to claim 1, wherein a peak of the emission spectrum of the exciplex has a longer wavelength than a peak of an emission spectrum of each of the first organic compound and the second organic compound.

6. The light-emitting device according to claim 1, wherein at least one of the first phosphorescent compound and the second phosphorescent compound is an organometallic complex.

7. The light-emitting device according to claim 1, wherein the first organic compound is a π

-electron deficient heteroaromatic compound.

8. The light-emitting device according to claim 1, wherein the second organic compound is a π

-electron rich heteroaromatic compound or an aromatic amine compound.

9. An electronic device comprising the light-emitting device according to claim 1.

10. A lighting device comprising the light-emitting device according to claim 1.

11. A light-emitting device comprising:

a first electroluminescent layer and a second electroluminescent layer between an anode and a cathode, at least one of the first electroluminescent layer and the second electroluminescent layer comprising a first light-emitting layer and a second light-emitting layer; and

a charge generation layer between the first electroluminescent layer and the second electroluminescent layer,

wherein the first light-emitting layer comprises a first phosphorescent compound, a first organic compound having an electron-transport property, and a second organic compound having a hole-transport property,

wherein the second light-emitting layer comprises a second phosphorescent compound and the first organic compound, and

wherein an emission spectrum of an exciplex of the first organic compound and the second organic compound overlaps with an absorption spectrum of the first phosphorescent compound.

12. The light-emitting device according to claim 11, wherein the first phosphorescent compound is different from the second phosphorescent compound.

13. The light-emitting device according to claim 12, wherein light emitted from the first light-emitting layer has a shorter wavelength than light emitted from the second light-emitting layer.

14. The light-emitting device according to claim 11, wherein a peak of the emission spectrum of the exciplex has a longer wavelength than a peak of the absorption spectrum of the first phosphorescent compound.

15. The light-emitting device according to claim 11, wherein a peak of the emission spectrum of the exciplex has a longer wavelength than a peak of an emission spectrum of each of the first organic compound and the second organic compound.

16. The light-emitting device according to claim 11, wherein at least one of the first phosphorescent compound and the second phosphorescent compound is an organometallic complex.

17. The light-emitting device according to claim 11, wherein the first organic compound is a π

-electron deficient heteroaromatic compound.

18. The light-emitting device according to claim 11, wherein the second organic compound is a π

-electron rich heteroaromatic compound or an aromatic amine compound.

19. An electronic device comprising the light-emitting device according to claim 11.

20. A lighting device comprising the light-emitting device according to claim 11.