Light-emitting element, lighting device, light-emitting device, and electronic device

• US 9,130,182 B2
• Filed: 06/24/2014
• Issued: 09/08/2015
• Est. Priority Date: 06/28/2013
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Seo, Hiromi, Takahashi, Tatsuyoshi
• Primary Examiner(s): WOJCIECHOWICZ, EDWARD JOSEPH
• Application Number:
  US14/313,356
• Publication Number:
  US 20150001502A1
• Time in Patent Office: 441 Days
• Field of Search: 257/40
• US Class Current: 1/1
• CPC Class Codes: H10K 2101/27 Combination of fluorescent and phosphorescent emission
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/12 comprising dopants
• CPC Class Codes: H10K 50/15 Hole transporting layers
• CPC Class Codes: H10K 50/16 Electron transporting layers
• CPC Class Codes: H10K 50/81 Anodes
• CPC Class Codes: H10K 50/82 Cathodes

Abstract

A light-emitting element with high emission efficiency is provided. A light-emitting element with a long lifetime is provided. The light-emitting element includes an anode; a hole-transport layer over the anode, containing a hole-transport compound and a compound; a light-emitting layer over the hole-transport layer, containing a host material and a guest material; and a cathode over the light-emitting layer. The host material is an electron-transport compound. The guest material and the compound are each independently a phosphorescent compound or a thermally activated delayed fluorescence material. A peak of an emission spectrum of the compound is on a shorter wavelength side than a peak of an emission spectrum of the guest material. Only the guest material emits light.

Claims

1. A light-emitting element comprising:

an anode;

a hole-transport layer over the anode, the hole-transport layer containing a hole-transport compound and a first compound;

a light-emitting layer over the hole-transport layer, the light-emitting layer containing a host material and a guest material; and

a cathode over the light-emitting layer,

wherein the first compound is any one of a phosphorescent compound and a thermally activated delayed fluorescence material,

wherein the host material is an electron-transport compound,

wherein the guest material is any one of a phosphorescent compound and a thermally activated delayed fluorescence material,

wherein a peak of an emission spectrum of the first compound is on a shorter wavelength side than a peak of an emission spectrum of the guest material, and

wherein only the guest material emits light.

2. The light-emitting element according to claim 1, wherein the hole-transport compound has an electron-blocking property.

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

wherein the electron-transport compound has a hole-blocking property.

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

wherein the electron-transport compound forms an exciplex in combination with the first compound.

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

wherein the first compound and the guest material are each an organometallic complex containing iridium.

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

wherein the peak of the emission spectrum of the first compound is determined by a photoluminescence method in a solvent, and

wherein the peak of the emission spectrum of the first compound is determined by a photoluminescence method in the solvent.

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

8. A light-emitting element comprising:

an anode;

a hole-transport layer over the anode, the hole-transport layer containing a hole-transport compound and a first compound;

a light-emitting layer over and in contact with the hole-transport layer, the light-emitting layer containing a host material and a guest material; and

a cathode over the light-emitting layer,

wherein the first compound is any one of a phosphorescent compound and a thermally activated delayed fluorescence material,

wherein the host material is an electron-transport compound,

wherein the guest material is any one of a phosphorescent compound and a thermally activated delayed fluorescence material,

wherein a peak of an emission spectrum of the first compound is on a shorter wavelength side than a peak of an emission spectrum of the guest material, and

wherein only the guest material emits light.

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

wherein the hole-transport compound has an electron-blocking property.

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

wherein the electron-transport compound has a hole-blocking property.

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

wherein the electron-transport compound forms an exciplex in combination with the first compound.

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

wherein the first compound and the guest material are each an organometallic complex containing iridium.

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

wherein the peak of the emission spectrum of the first compound is determined by a photoluminescence method in a solvent, and

wherein the peak of the emission spectrum of the first compound is determined by a photoluminescence method in the solvent.

14. A lighting device comprising the light-emitting element according to claim 8.