Light-emitting element and lighting device

• US 8,564,190 B2
• Filed: 02/24/2011
• Issued: 10/22/2013
• Est. Priority Date: 03/02/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Seo, Satoshi, Ushikubo, Takahiro
• Primary Examiner(s): Bowman, Mary Ellen
• Application Number:
  US13/033,739
• Publication Number:
  US 20110215714A1
• Time in Patent Office: 971 Days
• Field of Search: 313/503, 313/504, 313/512, 428/690
• US Class Current: 313/504
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• CPC Class Codes: C09K 2211/1007 Non-condensed systems
• CPC Class Codes: C09K 2211/1011 Condensed systems
• CPC Class Codes: C09K 2211/1014 bridged by heteroatoms, e.g. N, P, Si or B
• CPC Class Codes: C09K 2211/1029 containing one nitrogen atom as the heteroatom
• 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: H05B 33/14 characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/19 Tandem OLEDs
• CPC Class Codes: H10K 59/32 Stacked devices having two or more layers, each emitting at different wavelengths
• CPC Class Codes: H10K 85/342 comprising iridium
• 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

Abstract

To provide a light-emitting element whose power efficiency is improved and which emits light of natural color like light bulb color. In the light-emitting element, at least three light-emitting units are stacked. The emission spectrum of the light-emitting element has two peaks. One of the two peaks is obtained by combining spectra of light emitted from two light-emitting units. The peak is in the yellow to orange wavelength range and has a wavelength greater than or equal to 560 nm and less than 580 nm. Thus, a wavelength range of high luminosity can be used and the power efficiency can be improved. The color of light emitted from the light-emitting element is close to a blackbody locus in a chromaticity diagram, and light of natural color like light bulb color can be achieved.

Claims

1. A light-emitting element comprising:

an anode;

a cathode; and

a first light-emitting layer, a second light-emitting layer, a third light-emitting layer, a first intermediate layer, and a second intermediate layer between the anode and the cathode,

wherein the first intermediate layer is provided between the first light-emitting layer and the second light-emitting layer,

wherein the second intermediate layer is provided between the second light-emitting layer and the third light-emitting layer,

wherein a spectrum of light emitted from each of two of the first to third light-emitting layers has a peak in a yellow to orange wavelength range,

wherein an emission spectrum obtained by combining the spectra of light emitted from the two of the first to third light-emitting layers has a peak of which a wavelength is greater than or equal to 560 nm and less than 580 nm, and

wherein a spectrum of light emitted from the other of the first to third light-emitting layers has a peak in a blue wavelength range.

2. The light-emitting element according to claim 1,

wherein one of the anode and the cathode, the first light-emitting layer and

the first intermediate layer constitute a first light-emitting unit,

wherein the first intermediate layer, the second light-emitting layer and the second intermediate layer constitute a second light-emitting unit, and

wherein the second intermediate layer, the third light-emitting layer and the other of the anode and the cathode constitute a third light-emitting unit.

3. The light-emitting element according to claim 1,

wherein the two of the first to third light-emitting layers each contain a light-emitting substance, the light-emitting substance being a phosphorescent compound.

4. The light-emitting element according to claim 1,

wherein the other of the first to third light-emitting layers contains a light-emitting substance, the light-emitting substance being a fluorescent compound.

5. The light-emitting element according to claim 1,

wherein the two of the first to third light-emitting layers each contain a first light-emitting substance, the first light-emitting substance being a phosphorescent compound, and

wherein the other of the first to third light-emitting layers contains a second light-emitting substance, the second light-emitting substance being a fluorescent compound.

6. The light-emitting element according to claim 3,

wherein the phosphorescent compound includes an organometallic complex in which a pyrazine derivative serves as a ligand.

7. The light-emitting element according to claim 5,

wherein the phosphorescent compound includes an organometallic complex in which a pyrazine derivative serves as a ligand.

8. The light-emitting element according to claim 4,

wherein the fluorescent compound includes a pyrene diamine derivative.

9. The light-emitting element according to claim 5,

wherein the fluorescent compound includes a pyrene diamine derivative.

10. The light-emitting element according to claim 1,

wherein color of light obtained by combining light having a peak in the yellow to orange wavelength range and having a wavelength of the peak of greater than or equal to 560 nm and less than 580 nm and light having a peak in the blue wavelength range is in the range of ±

0.02 uv from a blackbody locus in a chromaticity diagram.

18. A lighting device comprising the light-emitting element according to claim 1 used as a light source.

11. A light-emitting element comprising:

at least three stacked light-emitting units,

wherein an emission spectrum of the light-emitting element has two peaks,

wherein one of the two peaks is a peak obtained by combining spectra of light emitted from two of the at least three stacked light-emitting units,

wherein the peak is in a yellow to orange wavelength range and the wavelength of the peak is greater than or equal to 560 nm and less than 580 nm, and

wherein the other of the two peaks is in a blue wavelength range.

12. The light-emitting element according to claim 11,

wherein the two of the at least three stacked light-emitting units each have a peak of an emission spectrum in the yellow to orange wavelength range.

13. The light-emitting element according to claim 11,

wherein the two of the at least three stacked light-emitting units each contain a light-emitting substance having a peak of an emission spectrum in the yellow to orange wavelength range, the light-emitting substance being a phosphorescent compound.

14. The light-emitting element according to claim 13,

wherein the phosphorescent compound includes an organometallic complex in which a pyrazine derivative serves as a ligand.

15. The light-emitting element according to claim 11,

wherein the other one of the at least three stacked light-emitting units contains a light-emitting substance having a peak of an emission spectrum in the blue wavelength range, the light-emitting substance being a fluorescent compound.

16. The light-emitting element according to claim 15,

wherein the fluorescent compound includes a pyrene diamine derivative.

17. The light-emitting element according to claim 11,

wherein color of light obtained by combining light having the peak in the yellow to orange wavelength range and having a wavelength of the peak of greater than or equal to 560 nm and less than 580 nm and light having the peak in the blue wavelength range is in the range of ±

0.02 uv from a blackbody locus in a chromaticity diagram.

19. A lighting device comprising the light-emitting element according to claim 11 used as a light source.