Electroluminescent device

• US 6,416,885 B1
• Filed: 08/28/1998
• Issued: 07/09/2002
• Est. Priority Date: 08/29/1997
• Status: Expired due to Term

• Current Assignee: IPIFS Guarantee Corp.
• Original Assignee: Cambridge Display Technology Limited (Sumitomo Chemical Company Limited)
• Inventors: Carter, Julian Charles, Heeks, Stephen Karl, Towns, Carl Robert
• Primary Examiner(s): YAMNITZKY, MARIE ROSE
• Application Number:
  US09/143,100
• Time in Patent Office: 1,411 Days
• Field of Search: 428/690, 428/917, 428/195, 428/201, 428/209, 313/504, 313/505, 313/506, 313/509, 257/40, 257/88, 257/91, 257/93, 257/96, 257/97, 257/99, 257/103
• US Class Current: 428/690
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/17 Carrier injection layers
• CPC Class Codes: H10K 50/805 Electrodes
• CPC Class Codes: H10K 59/00 Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/17 Passive-matrix OLED displays
• CPC Class Codes: H10K 85/1135 Polyethylene dioxythiophene [PEDOT]; Derivatives thereof
• CPC Class Codes: Y10S 428/917 Electroluminescent
• CPC Class Codes: Y10T 428/24802 Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
• CPC Class Codes: Y10T 428/24851 Intermediate layer is discontinuous or differential
• CPC Class Codes: Y10T 428/24917 including metal layer

Abstract

An electroluminescent device comprising: a first charge-carrier injecting layer for injecting positive charge carriers and a second charge-carrier injecting layer for injecting negative charge carriers, at least one of the charge-carrier injecting layers being patterned so as to comprise spaced-apart charge-injecting regions; an organic light-emitting layer located between the first and second charge-carrier injecting layers; and an unpatterned conductive polymer layer located between the organic light-emitting layer and the patterned charge-carrier injecting layer, the resistivity of the conductive polymer layer being sufficiently low to allow charge carriers to flow through it from the charge-injecting regions to generate light in the organic light-emitting layer but sufficiently high to resist lateral spreading of charge carriers beyond the charge-injecting regions.

Claims

1. An electroluminescent device comprising:

a first charge-carrier injecting layer for injecting positive charge carriers and a second charge-carrier injecting layer for injecting negative charge carriers, one of the charge-carrier injecting layers being patterned so as to comprise spaced-apart charge-injecting regions;

an organic light-emitting layer located between the first and second charge-carrier injecting layers; and

an unpatterned conductive polymer layer comprising polyethylene dioxythiophene and being located between the organic light-emitting layer and the patterned charge-carrier injecting layer, the resistivity of the conductive polymer layer being sufficiently low to allow charge carriers to flow through it from the charge-injecting regions to generate light in the organic light-emitting layer but greater than 10⁶ Ohms/square so as to resist lateral spreading of charge carriers beyond the charge-injecting regions.

2. An electroluminescent device as claimed in claim 1, wherein the light-emitting layer comprises a light-emitting conductive polymer.

3. An electroluminescent device as claimed in claim 1, wherein the light-emitting layer comprises a semiconductive conjugated polymer.

4. An electroluminescent device as claimed in claim 1, wherein the conductive polymer layer comprises a dopant, the presence of which affects the resistivity of the conductive polymer layer.

5. An electroluminescent device as claimed in claim 4, wherein the dopant is polystyrene sulphonic acid.

6. An electroluminescent device as claimed in claim 4, wherein the conductive polymer layer contains greater than 50 wt % dopant.

7. An electroluminescent device as claimed in claim 1, wherein the conductive polymer layer includes a cross-linking agent.

8. An electroluminescent device as claimed in claim 7, wherein the cross-linking agent is epoxy-silane.

9. An electroluminescent device as claimed in claim 7, wherein the conductive polymer layer contains greater than 50 wt % of the cross-linking agent.

10. An electroluminescent device as claimed in claim 1, wherein the regions of the light emitting layer capable of emitting light in use do not extend laterally beyond the charge injecting regions by more than 10% of the width of the charge injecting regions.

11. An electroluminescent device as claimed in claim 1, wherein each charge-injecting region defines one or more pixel regions of the device.

12. An electroluminescent device as claimed in claim 1, wherein each charge-injecting region is operable independently of the other charge-injecting region.

13. An electroluminescent device as claimed in claim 1, wherein the first charge-carrier injecting layer is the patterned charge-carrier injecting layer.

14. An electroluminescent device as claimed in claim 1, wherein the first and second charge-carrier injecting layers are patterned so as to comprise spaced-apart charge-injecting regions.