Light-Emitting Element, Light-Emitting Device, Electronic Device, and Lighting Device

• US 20150243918A1
• Filed: 02/17/2015
• Published: 08/27/2015
• Est. Priority Date: 02/21/2014
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Sasaki, Toshiki, Uesaka, Shogo, Seo, Satoshi
• Granted Patent: US 10,535,830 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 2101/30 Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values
• CPC Class Codes: H10K 2101/40 Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers
• CPC Class Codes: H10K 2101/90 Multiple hosts in the emissive layer
• 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 50/131 with spacer layers between the electroluminescent layers
• CPC Class Codes: H10K 50/19 Tandem OLEDs
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair
• 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 85/615 Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
• 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 with a high current efficiency is provided. A low-power consumption light-emitting device is also provided. In addition, low-power consumption electronic device and lighting device are provided. The light-emitting element includes an EL layer between a pair of electrodes. The EL layer includes a light-emitting layer. The light-emitting layer includes a first light-emitting layer and a second light-emitting layer. The emission peak of the second light-emitting layer is at a shorter wavelength than that of the first light-emitting layer. The first light-emitting layer includes a host material and a guest material. The LUMO level of the guest material is in the range of ±0.1 eV of the LUMO level of the host material.

Claims

1. A light-emitting element comprising:

a first EL layer between an anode and a cathode,

wherein the first EL layer includes a first light-emitting layer and a second light-emitting layer,

wherein the first light-emitting layer is located between the cathode and the second light-emitting layer,

wherein the first light-emitting layer is in contact with the second light-emitting layer,

wherein an emission peak of the second light-emitting layer is at a shorter wavelength than that of the first light-emitting layer,

wherein the first light-emitting layer includes a host material and a guest material, and

wherein a lowest unoccupied molecular orbital level of the guest material is in a range of ±

0.1 eV of a lowest unoccupied molecular orbital level of the host material.

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

a second EL layer between the anode and the cathode; and

a charge-generation layer between the first EL layer and the second EL layer.

3. The light-emitting element according to claim 2, wherein the first EL layer is located between the charge-generation layer and the cathode.

4. The light-emitting element according to claim 2, wherein the first EL layer is located between the charge-generation layer and the anode.

5. The light-emitting element according to claim 1, further comprising a third light-emitting layer,

wherein the third light-emitting layer is located between the first light-emitting layer and the cathode,

wherein the third light-emitting layer is in contact with the first light-emitting layer, and

wherein the second light-emitting layer and the third light-emitting layer include the same material.

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

wherein emission in the first light-emitting layer has a peak at a wavelength from 560 nm to 700 nm, and

wherein emission in the second light-emitting layer has a peak at a wavelength from 500 nm to 560 nm.

7. The light-emitting element according to claim 1, wherein the guest material is a phosphorescent organometallic iridium complex.

8. A light-emitting device comprising:

the light-emitting element according to claim 1; and

a flexible printed circuit.

9. An electronic device comprising:

the light-emitting device according to claim 8; and

an operation key, a speaker, a microphone, or an external connection portion.

10. A lighting device comprising:

the light-emitting device according to claim 8; and

a housing.

11. A light-emitting element comprising:

a first EL layer between an anode and a cathode,

wherein the first EL layer includes a first light-emitting layer and a second light-emitting layer,

wherein the first light-emitting layer is located between the cathode and the second light-emitting layer,

wherein the first light-emitting layer is in contact with the second light-emitting layer,

wherein an emission peak of the second light-emitting layer is at a shorter wavelength than that of the first light-emitting layer,

wherein the first light-emitting layer and the second light-emitting layer include the same host material,

wherein the first light-emitting layer includes a guest material, and

wherein a lowest unoccupied molecular orbital level of the guest material is in a range of ±

0.1 eV of a lowest unoccupied molecular orbital level of the host material.

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

a second EL layer between the anode and the cathode; and

a charge-generation layer between the first EL layer and the second EL layer.

13. The light-emitting element according to claim 12, wherein the first EL layer is located between the charge-generation layer and the cathode.

14. The light-emitting element according to claim 12, wherein the first EL layer is located between the charge-generation layer and the anode.

15. The light-emitting element according to claim 11, further comprising a third light-emitting layer,

wherein the third light-emitting layer is located between the first light-emitting layer and the cathode,

wherein the third light-emitting layer is in contact with the first light-emitting layer, and

wherein the second light-emitting layer and the third light-emitting layer include the same material.

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

wherein emission in the first light-emitting layer has a peak at a wavelength from 560 nm to 700 nm, and

wherein emission in the second light-emitting layer has a peak at a wavelength from 500 nm to 560 nm.

17. The light-emitting element according to claim 11, wherein the guest material is a phosphorescent organometallic iridium complex.

18. A light-emitting device comprising:

the light-emitting element according to claim 11; and

a flexible printed circuit.

19. An electronic device comprising:

the light-emitting device according to claim 18; and

an operation key, a speaker, a microphone, or an external connection portion.

20. A lighting device comprising:

the light-emitting device according to claim 18; and

a housing.