Claims
- 1. An OLED device, comprising:
a) a substrate; b) an anode formed of a conductive material over the substrate; c) an emissive layer having an electroluminescent material provided over the anode layer; d) a buffer structure including at least two layers, a first buffer layer provided over the electron-transport layer and containing an alkaline halide and a second buffer layer provided over the first buffer layer and containing a metal or metal alloy and having a work function of between 2.0 to 4.0 V; and e) a sputtered layer of a metal or metal alloy provided over the buffer structure.
- 2. An OLED device, comprising:
a) a substrate; b) an anode formed of a conductive material over the substrate; c) a hole-injection layer provided over the anode layer; d) a hole-transport layer provided over the hole-injection layer; e) an emissive layer having an electroluminescent material provided over the hole-transport layer; f) an electron-transport layer provided over the emissive layer; g) a buffer structure including at least two layers, a first buffer layer provided over the electron-transport layer and containing an alkaline halide and a second buffer layer provided over the first buffer layer and containing a metal or metal alloy and having a work function of between 2.0 to 4.0 V; and h) a sputtered layer of a metal or metal alloy provided over the buffer structure.
- 3. The OLED device of claim 1 wherein the first buffer layer has a thickness less than 10 nm but greater than 0 nm.
- 4. The OLED device of claim 1 wherein the first buffer layer has a thickness less than 3 nm but greater than 0.1 nm.
- 5. The OLED device of claim 1 wherein the second buffer layer has a thickness less than 20 nm but greater than 0 nm.
- 6. The OLED device of claim 1 wherein the second buffer layer has a thickness less than 10 nm but greater than 0 nm.
- 7. The OLED device of claim 1 wherein the alkaline halide includes LiF.
- 8. The OLED device of claim 1 wherein the metal having a work function between 2.0 V to 4.0 V includes yttrium, manganese, gallium, indium, lead, scandium, titanium, zirconium, hafnium, niobium, alkaline metals, alkaline earth metals and rare earth metals or metal alloys thereof.
- 9. The OLED device of claim 1 wherein the sputtered layer includes silver, aluminum, copper and, gold and alloys thereof.
- 10. The OLED device of claim 1 wherein the electron-transport layer includes Alq.
- 11. The OLED device of claim 1 wherein the emissive layer contains one or more light emitting doped materials.
- 12. The OLED device of claim 1 wherein the buffer structure has a thickness of less than 30 nm and greater than 0 nm.
- 13. The OLED device of claim 12 wherein the buffer structure has a thickness less than 5 nm and greater than 0 nm.
- 14. A method of making an OLED device, comprising the steps of:
(a) providing a substrate; (b) forming an anode of a conductive material over the substrate; (c) depositing an hole-injecting layer over the anode (d) depositing an emissive layer having an electroluminescent material provided over the hole-injecting layer; (e) forming a buffer structure including at least two layers, a first buffer layer provided over the electron-transport layer and containing an alkaline halide and a second buffer layer provided over the first buffer layer and containing a metal or metal alloy and having a work function of between 2.0 to 4.0 V; and (f) sputtering a metal or metal alloy layer provided over the buffer structure.
- 16. The method of claim 15 wherein the sputtering is accomplished using either DC or RF sputtering.
- 17. The method of claim 15 wherein the sputtering step is accomplished by sputtering materials from one or more targets.
- 18. The method of claim 15 wherein the first buffer layer has a thickness less than 10 nm but greater than 0 nm.
- 19. The method of claim 15 wherein the first buffer layer has a thickness less than 3 nm but greater than 0 nm.
- 20. The method of claim 15 wherein the second buffer layer has a thickness less than 20 nm but greater than 0 nm.
- 21. The method of claim 15 wherein the second buffer layer has a thickness less than 10 nm but greater than 0 nm.
- 22. The method of claim 14 wherein the buffer structure has a thickness of less than 30 nm and greater than 0 nm.
- 23. The method of claim 14 wherein the buffer structure has a thickness less than 5 nm and greater than 0 nm.
CROSS REFERENCE TO RELATED APPLICATION
[0001] Reference is made to commonly-assigned U.S. patent application Ser. No. 09/636,494 filed Aug. 11, 2000, entitled “Improved Cathode Layer in Organic Light-Emitting Diode Devices” by Raychaudhuri et al, the disclosure of which is incorporated herein.