Organic electroluminescent device with stabilized cathode

• US 5,047,687 A
• Filed: 07/26/1990
• Issued: 09/10/1991
• Est. Priority Date: 07/26/1990
• Status: Expired due to Term

• Current Assignee: Global OLED Technology LLC (LG Display Co., Ltd.)
• Original Assignee: Eastman Kodak Company
• Inventors: VanSlyke, Steven A.
• Primary Examiner(s): O SHEA, SANDRA L
• Application Number:
  US07/557,848
• Time in Patent Office: 411 Days
• Field of Search: 313/503, 313/504, 313/506, 428/457
• US Class Current: 313/503
• CPC Class Codes: H05B 33/04 Sealing arrangements , e.g. against humidity
• CPC Class Codes: H05B 33/12 Light sources with substantially two-dimensional radiating surfaces
• CPC Class Codes: H05B 33/14 characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source
• CPC Class Codes: H05B 33/26 characterised by the composition or arrangement of the conductive material used as an electrode
• CPC Class Codes: H10K 50/82 Cathodes
• CPC Class Codes: H10K 50/826 Multilayers, e.g. opaque multilayers
• CPC Class Codes: H10K 50/844 Encapsulations
• CPC Class Codes: H10K 50/846 comprising getter material or desiccants
• CPC Class Codes: Y10T 428/31678 Of metal

Abstract

An organic electroluminescent device is disclosed which is protected from dark spot formation. The device is comprised of, in sequence, a support, an anode, an organic electroluminescent medium, and a cathode. The cathode contains a plurality of metals, at least one of which is a low work function metal other than an alkali metal. Overlying the cathode is a protective layer comprised of a mixture of at least one organic component of the organic electroluminescent medium and at least one metal having a work function in the range of from 4.0 to 4.5 eV capable of being oxidized in the presence of ambient moisture.

Claims

1. An organic electroluminescent device comprising in sequence, a support, an anode, an organic electroluminescent medium, and a cathode,

characterized in that

said cathode is comprised of a layer consisting essentially of a plurality of metals other than alkali metals, at least one of said metals having a work function of less than 4 eV, and,

overlying said cathode, a protective layer comprised of a mixture of

at least one organic component of said organic electroluminescent medium and

at least one metal having a work function in the range of from 4.0 to 4.5 eV capable of being oxidized in the presence of ambient moisture.

2. An organic electroluminescent device according to claim 1 further characterized in that said anode is light transmissive.

3. An organic electroluminescent device according to claim 1 further characterized in that said organic electroluminescent medium includes an organic electron injecting and transporting zone.

4. An organic electroluminescent device according to claim 3 further characterized in that said organic electron injecting and transporting zone is comprised of a stilbene or chelated oxinoid compound.

5. An organic electroluminescent device according to claim 3 further characterized in that at least one said organic component of said protective layer is also present in said organic electron injecting and transporting zone.

6. An organic electroluminescent device according to claim 1 further characterized in that said organic electroluminescent medium includes a hole injecting and transporting zone.

7. An organic electroluminescent device according to claim 6 further characterized in that said hole injecting and transporting zone includes at least one aromatic tertiary amine.

8. An organic electroluminescent device according to claim 6 further characterized in that said hole injecting and transporting zone includes at least one porphorinic compound.

9. An organic electroluminescent device according to claim 6 further characterized in that least one said organic component of said protective layer is also present in said organic hole injecting and transporting zone.

10. An organic electroluminescent device according to claim 1 further characterized in that said protective layer has a thickness of at least 200 Å

.

11. An organic electroluminescent device according to claim 1 further characterized in that said protective layer has a thickness of up to 5 μ

m.

12. An organic electroluminescent device according to claim 11 further characterized in that said protective layer has a thickness in the range of from 500 Å

to 2 μ

m.

13. An organic electroluminescent device according to claim 1 further characterized in that said metal present in said protective layer accounts for 20 to 90 percent by weight of said protective layer, based on total weight.

14. An organic electroluminescent device according to claim 13 further characterized in that said metal present in said protective layer accounts for 30 to 80 percent by weight of said protective layer, based on total weight.