Electroluminescent devices

• US 7,227,180 B2
• Filed: 04/22/2005
• Issued: 06/05/2007
• Est. Priority Date: 03/13/1998
• Status: Expired due to Term

• Current Assignee: Cambridge Display Technology Limited (Sumitomo Chemical Company Limited)
• Original Assignee: Cambridge Display Technology Limited (Sumitomo Chemical Company Limited)
• Inventors: Burroughes, Jeremy Henley, Friend, Richard Henry, Lacey, David John, Devine, Peter, Bright, Christopher John
• Primary Examiner(s): TRINH, MICHAEL MANH
• Application Number:
  US11/113,283
• Publication Number:
  US 20050184658A1
• Time in Patent Office: 774 Days
• Field of Search: 438/22, 438/99, 438 28- 29, 257/40, 257/98, 257/103
• US Class Current: 257/40
• CPC Class Codes: C08G 2261/3142 fluorene-based, e.g. fluorene, indenofluorene, or spirobifluorene
• CPC Class Codes: C08G 2261/3162 Arylamines
• CPC Class Codes: C08G 2261/3246 containing nitrogen and sulfur as heteroatoms
• 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 50/12 comprising dopants
• CPC Class Codes: H10K 50/15 Hole transporting layers
• CPC Class Codes: H10K 50/16 Electron transporting layers
• CPC Class Codes: H10K 71/12 using liquid deposition, e.g. spin coating
• CPC Class Codes: H10K 85/115 Polyfluorene; Derivatives thereof
• CPC Class Codes: H10K 85/151 Copolymers

Abstract

An electroluminescent device comprising: a first charge carrier injecting layer for injecting positive charge carriers; a second charge carrier injecting layer for injecting negative charge carriers; and a light-emissive layer located between the charge carrier injecting layers and comprising a mixture of: a first component for accepting positive charge carriers from the first charge carrier injecting layer; a second component for accepting negative charge carriers from the second charge carrier injecting layer; and a third, organic light-emissive component for generating light as a result of combination of charge carriers from the first and second components; at least one of the first, second and third components forming a type II semiconductor interface with another of the first, second and third components.

Claims

1. An electroluminescent device comprising:

a first charge carrier injecting layer for injecting positive charge carriers;

a second charge carrier injecting layer for injecting negative charge carriers; and

a light-emissive layer located between the charge carrier injecting layers and comprising;

a first component for accepting positive charge carriers from the first charge carrier injecting layer;

a second component for accepting negative charge carriers from the second charge carrier injecting layer; and

a third, organic light-emissive component for generating light as a result of combination of charge carriers from the first and second components; and

at least one of the first, second and third components forming a type II semiconductor interface with another of the first, second the third components; and

wherein the first charge carrier injecting layer is a positive charge carrier transport layer which is located between the light-emissive layer and an anode electrode layer.

2. An electroluminescent device as claimed in claim 1, wherein all of the first, second and third components form type II semiconductor interfaces with the others of the first, second and third components.

3. An electroluminescent device as claimed in claim 1, wherein the optical gap of the third components is greater than 1.8 eV.

4. An electroluminescent device a claimed in claim 1, wherein the first component is capable of accepting positive charge carriers from the first charge carrier injecting layer and contains amine groups.

5. An electroluminescent device as claimed in claim 1, wherein the second component is F8.

6. An electroluminescent device as claimed in claim 1, wherein the first component has a LUMO energy level between the LUMO energy levels of the second and third components.

7. An electroluminescent device as claimed in claim 1, wherein the optical gap of the third component is less than the optical gaps of the first and second components.

8. An electroluminescent device as claimed in claim 1, wherein the third component is F8BT or a soluble PPV.

9. An electroluminescent device as claimed in claim 1, wherein the first charge carrier injecting layer forms a type II semiconductor interface with the light-emissive layer.

10. An electroluminescent device as claimed in claim 1, wherein the first charge carrier injecting layer is an anode electrode layer.

11. An electroluminescent device as claimed in claim 1, wherein the anode electrode layer has a workfunction greater than 4.3 eV.

12. An electroluminescent device as claimed in claim 1, wherein the second charge carrier injecting layer is a negative charge carrier transport layer which is located between the light-emissive layer and a cathode electrode layer.

13. An electroluminescent device as claimed in claim 12, wherein the second charge carrier injecting layer forms a type II semiconductor interface with the light-emissive layer.

14. An electroluminescent device as claimed in claim 1, wherein the second charge carrier injecting layer is a cathode electrode layer.

15. An electroluminescent device as claimed in claim 14, wherein the cathode electrode layer has a workfunction less than 3.5 eV.

16. An electroluminescent device as claimed in claim 1, wherein at least one of the charge carrier injecting layers is a light transmissive electrode layer.

17. A method for forming an electroluminescent device comprising the steps of:

depositing a first charge carrier injecting layer for injecting charge carriers of a first polarity;

depositing a light-emissive layer comprising;

a first component for accepting charge carriers of the first polarity from the first charge carrier injecting layer;

a second component for accepting charge carriers of the opposite polarity from a second charge carrier injecting layer; and

a third, organic light-emissive component for generating light as a result of combination of charge carriers from the first and second components;

at least one of the first, second and third components forming a type II semiconductor interface with another of the first, second and third components;

wherein the first charge carrier injecting layer is a positive charge carrier transport layer which is located between the light-emissive layer and an anode electrode layer; and

depositing the second charge carrier injecting layer over the light-emissive layer for injecting charge carriers of the opposite polarity.

18. A method as claimed in claim 17, wherein the light-emissive layer is deposited from solution.