MULTILAYER POLYMER ELECTROLUMINESCENT DEVICE COMPRISING WATER-SOLUBLE POLYMER LAYER CONTAINING CATIONS AND METHOD FOR FABRICATING THE SAME

• US 20100252821A1
• Filed: 02/12/2008
• Published: 10/07/2010
• Est. Priority Date: 07/12/2007
• Status: Active Grant

• Current Assignee: Kyungsung University Industry Cooperation Foundation
• Original Assignee: Kyungsung University Industry Cooperation Foundation
• Inventors: Cho, Seong-Jin, Kwon, Tae-Woo, Park, Dong Kyu, Woo, Hyung Suk
• Granted Patent: US 8,350,254 B2
• Time in Patent Office: Days
• US Class Current: 257/40
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• CPC Class Codes: C09K 2211/14 Macromolecular compounds
• CPC Class Codes: H05B 33/10 Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
• CPC Class Codes: H10K 50/165 comprising dopants
• CPC Class Codes: H10K 50/166 comprising a multilayered structure

Abstract

A polymer electroluminescent device is provided. The device comprises an anode, a light-emitting layer, a cation-containing water-soluble polymer layer and a cathode formed in this order on a substrate wherein the cation-containing water-soluble polymer layer is formed by wet coating. The cation-containing water-soluble polymer layer as a secondary thin film layer is not dissolved in a solvent for the formation of the underlying light-emitting layer to prevent intermixing between the two layers, thereby enabling the formation of a multilayer structure by wet coating. In addition, the cation-containing water-soluble polymer layer attracts electrons injection from the cathode by an attractive Coulomb force to effectively increase the mobility of the electrons while blocking high-mobility holes from the anode at an interface between the light-emitting layer and the water-soluble layer. Further provided is a method for fabricating the electroluminescent device.

Claims

1. A polymer electroluminescent device comprising an anode, a light-emitting layer, a cation-containing water-soluble polymer layer and a cathode formed in this order on a substrate wherein the cation-containing water-soluble polymer layer is formed by wet coating.

2. The device according to claim 1, wherein the cation-containing water-soluble polymer layer contains a water-soluble polyurethane resin.

3. The device according to claim 2, wherein the water-soluble polyurethane resin is polyurethane-polyurea, polyurethane-polyacrylate, or a mixture thereof.

4. The device according to claim 1, wherein the cation-containing water-soluble polymer layer has a thickness of 1 to 10 nm.

5. The device according to claim 1, wherein the cation-containing water-soluble polymer layer contains at least one kind of cations selected from the group consisting of Cs⁺,Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, Ca²⁺, Ba²⁺, Al³⁺ and Ag²⁺ cations.

6. The device according to claim 1, wherein the light-emitting layer may be composed of a blue, red or green light emitting material.

7. The device according to claim 1, further comprising at least one layer selected from the group consisting of a hole injection layer, a hole transport layer, an electron transport layer and an electron injection layer between the first electrode and the second electrode.

8. The device according to claim 1, wherein the device has a multilayer structure consisting of:

an anode/a hole injection layer/a light-emitting layer/a cation-containing water-soluble polymer layer/a cathode;

an anode/a hole injection layer/a light-emitting layer/a cation-containing water-soluble polymer layer/an electron injection layer/a cathode;

an anode/a hole injection layer/a hole transport layer/a light-emitting layer/a cation-containing water-soluble polymer layer/a cathode;

an anode/a hole injection layer/a hole transport layer/a light-emitting layer/a cation-containing water-soluble polymer layer/an electron injection layer/a cathode;

or

an anode/a hole injection layer/a hole transport layer/a light-emitting layer/a cation-containing water-soluble polymer layer/an electron transport layer/an electron injection layer/a cathode.

9. A method for fabricating a polymer electroluminescent device, the method comprising the steps of forming an anode on a substrate, forming a light-emitting layer on the anode, forming a cation-containing water-soluble polymer layer on the light-emitting layer and a cathode on the cation-containing water-soluble polymer layer wherein the cation-containing water-soluble polymer layer is formed by wet coating.

10. The method according to claim 9, wherein the wet coating is performed using a solution of a water-soluble polymer in cation-containing distilled water.

11. The method according to claim 10, wherein the water-soluble polymer is a water-soluble polyurethane resin.

12. The method according to claim 10, wherein the water-soluble polymer is present at a concentration of 0.4 to 2% by weight in the cation-containing solution of the water-soluble polymer.

13. The method according to claim 10, wherein the cation-containing distilled water is prepared by purifying a solution of an ionic compound containing both cations and anions by column chromatography to selectively separate the cations only.

14. The method according to claim 10, wherein the cations are present at a concentration of 1 to 20 ppm in the cation-containing distilled water.

15. The method according to claim 9, wherein the cations are selected from the group consisting of Cs⁺, Li⁺, Na⁺, Be²⁺, Mg²⁺, Ca²⁺, Ba²⁺, Al³⁺, Ag²⁺ cations, and combinations thereof.

16. The method according to claim 9, wherein the cation-containing water-soluble polymer layer has a thickness of 1 to 10 nm.

17. The method according to claim 9, further comprising the step of forming at least one layer selected from the group consisting of a hole injection layer, a hole transport layer, an electron transport layer and an electron injection layer between the first electrode and the second electrode.