Electroluminescent devices

• US 8,115,199 B2
• Filed: 10/07/2008
• Issued: 02/14/2012
• Est. Priority Date: 03/13/1998
• Status: Expired due to Fees

• 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, Bright, Christopher John, Lacey, David John, Devine, Peter
• Primary Examiner(s): Trinh, Michael
• Application Number:
  US12/246,729
• Publication Number:
  US 20090096363A1
• Time in Patent Office: 1,225 Days
• Field of Search: 438/28, 438/99, 438/22, 438/47, 257/40, 257/98, 257/E33.001, 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;

an organic light-emissive layer located between the charge carrier injecting layers; and

a plurality of positive charge carrier transport layers located between the light emissive layer and the positive charge carrier injecting layer;

wherein a luminescent type II heterojunction is formed between one of the positive charge carrier transport layers and the light-emissive layer;

wherein the plurality of positive charge carrier transport layers provide a series of intermediate energy steps between the light-emissive layer and the positive charge carrier injection layer.

2. An electroluminescent device according to claim 1, wherein one or more of the positive charge carrier transport layers are organic.

4. An electroluminescent device according to claim 1, comprising:

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

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

an organic light-emissive layer located between the charge carrier injecting layers; and

a plurality of positive charge carrier transport layers located between the light emissive layer and the positive charge carrier injecting layer;

wherein a luminescent type II heterojunction is formed between one of the positive charge carrier transport layers and the light-emissive layer;

wherein the organic light-emissive layer comprises a light-emissive component and a charge transporting component; and

wherein the plurality of positive charge carrier transport layers provide a series of intermediate energy steps between the light-emissive layer and the positive charge carrier injection layer.

5. An electroluminescent device according to claim 4, wherein the charge transporting component is for transporting negative charge carriers.

6. An electroluminescent device according to claim 4, wherein the organic light-emissive component and the charge transporting component are provided as components of a single molecule.

7. An electroluminescent device according to claim 4, wherein the organic light-emissive component and the charge transporting component form a type II semiconductor interface.

3. 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;

an organic light-emissive layer located between the charge carrier injecting layers; and

a plurality of positive charge carrier transport layers located between the light emissive layer and the positive charge carrier injecting layer;

wherein a luminescent type II heterojunction is formed between one of the positive charge carrier transport layers and the light-emissive layer;

wherein a further organic charge transporting layer is located between the light-emissive layer and the negative charge carrier injecting layers; and

wherein the plurality of positive charge carrier transport layers provide a series of intermediate energy steps between the light-emissive layer and the positive charge carrier injection layer.

8. A method for forming an electroluminescent device,

comprising:

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

depositing an organic light-emissive layer over the first charge carrier injecting layer; and

depositing a second charge carrier injecting layer for injecting negative charge carriers over the organic light-emissive layer,

wherein the method comprises a further step of depositing a plurality of positive charge transport layers located between the light-emissive layer and the positive charge carrier injecting layer forming a luminescent type II heterojunction between one of the positive charge carrier transport layers and the light-emissive layer; and

wherein the plurality of positive charge carrier transport layers provide a series of intermediate energy steps between the light-emissive layer and the positive charge carrier injection layer.

9. A method according to claim 8, wherein the organic light-emissive layer and one or more of the positive charge carrier transport layers are deposited from solution.

10. A method according to claim 9, wherein the organic light-emissive layer and one or more of the positive charge carrier transport layers are deposited together from solution and phase separate to form the organic light-emissive layer and the one or more positive charge carrier transport layers.

11. A method according to claim 9, wherein the organic light-emissive layer and one or more of the positive charge carrier transport layers are deposited in separate deposition steps.

12. A method according to claim 8, wherein one or more of the positive charge carrier transport layers are organic.

14. A method according to claim 8, for forming an electroluminescent device, comprising:

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

depositing an organic light-emissive layer over the first charge carrier injecting layer; and

depositing a second charge carrier injecting layer for injecting negative charge carriers over the organic light-emissive layer,

wherein the method comprises a further step of depositing a plurality of positive charge transport layers located between the light-emissive layer and the positive charge carrier injecting layer forming a luminescent type II heterojunction between one of the positive charge carrier transport layers and the light-emissive layer, and

wherein the organic light-emissive layer comprises a light-emissive component and a charge transporting component.

15. A method according to claim 14, wherein the charge transporting component is for transporting negative charge carriers.

16. A method according to claim 14, wherein the organic light-emissive component and the charge transporting component are provided as components of a single molecule.

17. A method according to claim 14, wherein the organic light-emissive component and the charge transporting component form a type II semiconductor interface.

13. A method for forming an electroluminescent device, comprising:

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

depositing an organic light-emissive layer over the first charge carrier injecting layer; and

depositing a second charge carrier injecting layer for injecting negative charge carriers over the organic light-emissive layer;

wherein the method comprises a further step of depositing a plurality of positive charge transport layers located between the light-emissive layer and the positive charge carrier injecting layer forming a luminescent type II heterojunction between one of the positive charge carrier transport layers and the light-emissive layer;

wherein a further organic charge transporting layer is disposed between the light emissive layer and the negative charge carrier injecting layer; and

wherein the plurality of positive charge carrier transport layers provide a series of intermediate energy steps between the light-emissive layer and the positive charge carrier injection layer.