Active matrix OED array with improved OED cathode

• US 5,998,805 A
• Filed: 12/11/1997
• Issued: 12/07/1999
• Est. Priority Date: 12/11/1997
• Status: Expired due to Term

• Current Assignee: Universal Display Corporation
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Lee, Hsing-Chung, So, Franky, Shi, Song Q.
• Primary Examiner(s): MINTEL, WILLIAM A
• Application Number:
  US08/988,976
• Time in Patent Office: 726 Days
• Field of Search: 257/40, 257/103, 257/94, 257/96, 257/97, 257/88, 257/72, 257/59
• US Class Current: 257/40
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: H10K 2102/3026 Top emission
• CPC Class Codes: H10K 2102/351 Thickness
• CPC Class Codes: H10K 50/171 Electron injection layers
• CPC Class Codes: H10K 50/816 Multilayers, e.g. transparent multilayers
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/38 comprising colour filters or colour changing media [CCM]

Abstract

An active matrix OED array with an improved device cathode includes a plurality of control transistors formed on a semiconductor substrate with insulating material positioned over the control transistors to form a planar surface. A plurality of contact pads are formed on the planar surface and electrically coupled to the control transistors. A thin (5 Å to 20 Å) electron injecting layer of either alkaline metal oxide or alkaline metal fluoride is positioned on each contact pad and organic material is deposited on the electron injecting layer so as to define an organic light emitting device on each contact pad and electrical and light conducting material is positioned over the organic material to define a second terminal for the OEDs.

Claims

1. An active matrix organic light emitting device array with improved device cathode comprising:

a substrate having an array area defined thereon;

a plurality of control transistors formed on the substrate in the array area;

a planarizing layer of insulating material positioned over the plurality of control transistors in the array area and defining a substantially planar surface;

a plurality of contact pads formed on the planar surface of the planarizing layer in the array area, the plurality of contact pads being electrically coupled with the plurality of control transistors;

an electron injecting layer of one of alkaline metal oxide and alkaline metal fluoride positioned on each contact pad of the plurality of contact pads;

a plurality of layers of organic material sequentially formed in overlying relationship on each of the electron injecting layers in the array area so as to define an organic light emitting device on each contact pad with each contact pad operating as a first terminal of an overlying organic light emitting device; and

electrical and light conducting material positioned in overlying relationship over the layers of organic material in the array area and defining a second terminal of each of the organic light emitting devices.

2. An active matrix organic light emitting device array as claimed in claim 1 wherein the substrate includes one of silicon, GaAs, SiC, and sapphire.

3. An active matrix organic light emitting device array as claimed in claim 1 wherein the plurality of control transistors includes MOSFETs.

4. An active matrix organic light emitting device array as claimed in claim 1 wherein the plurality of layers of organic material includes an electron transporting layer, a light emitting layer and a hole transporting layer sequentially formed in overlying relationship.

5. An active matrix organic light emitting device array as claimed in claim 1 wherein the planarizing layer of insulating material includes SiO₂.

6. An active matrix organic light emitting device array as claimed in claim 1 wherein the first terminal of each of the overlying organic light emitting devices is a cathode.

7. An active matrix organic light emitting device array as claimed in claim 6 wherein the second terminal includes a transparent or semitransparent layer of material selected from a group including gold, silver, palladium, ITO, ZnO_x, VO_x, and combinations thereof.

8. An active matrix organic light emitting device array as claimed in claim 1 wherein the electron injecting layer is less than 50 Å

thick.

9. An active matrix organic light emitting device array as claimed in claim 1 wherein the electron injecting layer has a thickness in a range of approximately 1 Å

to 20 Å

.

10. An active matrix organic light emitting device array as claimed in claim 1 wherein the electron injecting layer including an alkaline metal oxide from the group LiO_x, MgO_x, CaO_x, and CsO_x.

11. An active matrix organic light emitting device array as claimed in claim 1 wherein the electron injecting layer including an alkaline metal fluoride from the group LiF, MgF₂, and CaF₂.

12. An active matrix organic light emitting device array as claimed in claim 1 wherein the electrical and light conducting material includes at least one light filter for producing a color display.

13. An active matrix organic light emitting device array with improved device cathode comprising:

a substrate having an array area defined thereon;

a plurality of field effect transistors, each including first and second current carrying terminals and a control terminal, formed in the array area on the substrate in rows and columns, each of the rows including a row bus coupled to the first current carrying terminal of each field effect transistor in the row, and each of the columns including a column bus coupled to the control terminal of each field effect transistor in the column;

a planarizing layer of insulating material positioned over the plurality of field effect transistors in the array area and defining a substantially planar surface;

a plurality of contact pads formed on the planar surface of the planarizing layer in the array area in rows and columns, one contact pad associated with each field effect transistor of the plurality of field effect transistors and coupled to the second current carrying terminal of the associated field effect transistor;

an electron injecting layer of one of alkaline metal oxide and alkaline metal fluoride positioned on each contact pad of the plurality of contact pads;

a plurality of layers of organic material sequentially formed in overlying relationship on the electron injecting layer in the array area so as to define an organic light emitting device on each contact pad with each contact pad operating as a first terminal of an overlying organic light emitting device; and

electrical and light conducting material positioned in overlying relationship over the layers of organic material in the array area and operating as a common second terminal of the organic light emitting devices.

14. An active matrix organic light emitting device array as claimed in claim 13 wherein the substrate includes one of silicon, GaAs, SiC, and sapphire.

15. An active matrix organic light emitting device array as claimed in claim 13 wherein the plurality of control transistors includes MOSFETs.

16. An active matrix organic light emitting device array as claimed in claim 13 wherein the plurality of layers of organic material includes an electron transporting layer, a light emitting layer and a hole transporting layer sequentially formed in overlying relationship.

17. An active matrix organic light emitting device array as claimed in claim 13 wherein the planarizing layer of insulating material includes SiO₂.

18. An active matrix organic light emitting device array as claimed in claim 13 wherein the first terminal of each of the overlying organic light emitting devices is a cathode.

19. An active matrix organic light emitting device array as claimed in claim 18 wherein the second terminal includes a transparent or semitransparent layer of material selected from a group including gold, silver, palladium, ITO, ZnO_x, VO_x, and combinations thereof.

20. An active matrix organic light emitting device array as claimed in claim 13 wherein the electron injecting layer is less than 50 Å

thick.

21. An active matrix organic light emitting device array as claimed in claim 13 wherein the electron injecting layer has a thickness in a range of approximately 1 Å

to 20 Å

.

22. An active matrix organic light emitting device array as claimed in claim 13 wherein the electron injecting layer including an alkaline metal oxide from the group LiO_x, MgO_x, CaO_x, and CsO_x.

23. An active matrix organic light emitting device array as claimed in claim 13 wherein the electron injecting layer including an alkaline metal fluoride from the group LiF, MgF₂, and CaF₂.

24. An active matrix organic light emitting device array as claimed in claim 13 wherein the electrical and light conducting material includes a light filter component for producing a color display.