Color-Tunable OLED Lighting Device

• US 20150108917A1
• Filed: 10/18/2013
• Published: 04/23/2015
• Est. Priority Date: 10/18/2013
• Status: Active Grant

• Current Assignee: OLEDWorks LLC
• Original Assignee: OLEDWorks LLC
• Inventors: Hamer, John W.
• Granted Patent: US 9,142,595 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: H05B 45/60 Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]
• 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 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/19 Tandem OLEDs
• CPC Class Codes: H10K 59/32 Stacked devices having two or more layers, each emitting at different wavelengths

Abstract

A color-tunable OLED device comprising: a charge-carrying cathode layer and a charge-carrying anode layer disposed parallel to each other; at least a first organic light-emitting unit and a second organic light-emitting unit disposed between the cathode and anode; and at least one charge-generating layer disposed between the cathode and anode, wherein the charge-generating layer is a charge-carrying layer of lesser lateral conductivity than the anode and cathode, and said charge-generating layer is electrically connected without additional circuit elements to another charge-carrying layer and disposed such that at least one organic light-emitting unit is wedged between two directly-connected charge-carrying layers, and at least one organic light-emitting unit is not thusly wedged.

Claims

1. A color-tunable OLED device comprising:

a. a charge-carrying cathode layer and a charge-carrying anode layer disposed parallel to each other;

b. at least a first organic light-emitting unit and a second organic light-emitting unit disposed between the cathode and anode; and

c. at least one charge-generating layer disposed between the cathode and anode, wherein the charge-generating layer is a charge-carrying layer of lesser lateral conductivity than the anode and cathode, and said charge-generating layer is electrically connected without additional circuit elements to another charge-carrying layer and disposed such that at least one organic light-emitting unit is wedged between two directly-connected charge-carrying layers, and at least one organic light-emitting unit is not thusly wedged.

2. The color-tunable OLED device of claim 1 wherein the charge-carrying layer to which the charge-generating layer is electrically connected is the anode.

3. The color-tunable OLED device of claim 1 wherein the charge-carrying layer to which the charge-generating layer is electrically connected is the cathode.

4. The color-tunable OLED device of claim 1 wherein the lateral conductivity of the charge generating layer is selected to be greater than the lateral conductivity of the first and second light-emitting units.

5. The color-tunable OLED device of claim 4 wherein the resistivity of the charge-generating layer is in the range from 100 to 3000 ohms/square.

6. The color-tunable OLED device of claim 5 wherein the lateral conductivity of the charge-generating layer is selected such that at a first light-producing voltage the lateral voltage change across the charge-generating layer is less than or equal to the practical threshold voltage of the wedged organic light-emitting unit, such that vertical current substantially only flows through, and light is substantially only emitted by, the non-wedged organic light-emitting unit.

7. The color-tunable OLED device of claim 6 wherein the lateral conductivity of the charge-generating layer is further selected such that at a second light-producing voltage greater than the first light-producing voltage, the lateral voltage change across the charge-generating layer is greater than the threshold voltage of the wedged organic light-emitting unit, such that vertical current flows through, and light is emitted by, at least a portion of the wedged organic light-emitting unit.

8. The color-tunable OLED device of claim 1 wherein the charge generating layer comprises a metal, a metal oxide, or a conductive doping material in a less conductive material.

9. The color-tunable OLED device of claim 8 wherein the charge-generating layer comprises silver, calcium, indium-tin oxide, zinc oxide, or molybdenum oxide.

10. The color-tunable OLED device of claim 8 wherein the conductivity of the charge generating layer is adjusted by varying the thickness of the layer, or the percentage of conductive doping material, or both.

11. The color-tunable OLED device of claim 1 wherein the device is connected to and controlled by a control circuit that includes a variable voltage source.

12. The color-tunable OLED device of claim 11 wherein the control circuit further includes a pulse-width modulating unit.

13. The color-tunable OLED device of claim 1 wherein the first organic light-emitting unit provides light in a selected first portion of the visible spectrum, and the second organic light-emitting unit provides light in a selected second portion of the visible spectrum.

14. The color-tunable OLED device of claim 13 wherein the selected first portion of the visible spectrum and the selected second portion of the visible spectrum are complementary colors that together can produce white light.

15. The color-tunable OLED device of claim 1 further including a third light-emitting unit and a second charge-generating layer disposed between the cathode and anode.

16. The color-tunable OLED device of claim 15 wherein the charge-carrying layer to which the charge-generating layer is electrically connected is the second charge-generating layer.

17. The color-tunable OLED device of claim 15 wherein the charge-generating layer is electrically connected to the second charge-generating layer and to one of the electrodes.

18. The color-tunable OLED device of claim 15 wherein the charge-generating layer is electrically connected to one of the electrodes and the second charge-generating layer is not connected to another charge-carrying layer.

19. The color-tunable OLED device of claim 15 wherein the charge-generating layer is electrically connected to one of the electrodes and the second charge-generating layer is connected to the other electrode.

20. The color-tunable OLED device of claim 15 wherein the lateral conductivity of the second charge-generating layer is different from the lateral conductivity of the first charge-generating layer.

21. The color-tunable OLED device of claim 15 wherein the first organic light-emitting unit provides light in a selected first portion of the visible spectrum, the second organic light-emitting unit provides light in a selected second portion of the visible spectrum, and the third organic light-emitting unit provides light in a selected third portion of the visible spectrum.

22. The color-tunable OLED device of claim 21 wherein the selected portions of the visible spectrum are complementary colors that together can produce white light.

23. The color-tunable OLED device of claim 15 wherein the first and third organic light-emitting units provide light in a selected first portion of the visible spectrum, and the second organic light-emitting unit provides light in a selected second portion of the visible spectrum.

24. The color-tunable OLED device of claim 23 wherein the selected first portion of the visible spectrum and the selected second portion of the visible spectrum are complementary colors that together can produce white light.

25. The color-tunable OLED device of claim 15 wherein the light emissions for the first, second, and third organic light-emitting units have different areas, as defined by the overlap of electrodes and charge-generating layer.

26. The color-tunable OLED device of claim 1 wherein the electrical connection of the charge-generating layer to the electrode is located a selected distance outside of the emitting area of the device.

27. The color-tunable OLED device of claim 1 wherein the light emissions for the first and second organic light-emitting units have different areas, as defined by the overlap of electrodes and charge-generating layer.

28. The color-tunable OLED device of claim 1 further including a diffuser on the light-emitting side of the device.

29. A method for tuning the color emission of an OLED device, comprising:

a. providing a substrate;

b. providing a first formed charge-carrying electrode over the substrate;

c. providing a first light-emitting unit formed over the first electrode;

d. providing a charge-generating layer over the first light-emitting unit, wherein the charge-generating layer is electrically connected without additional circuit elements to another charge-carrying layer;

e. providing a second light-emitting unit formed over the charge-generating layer;

f. providing a second charge-carrying electrode formed over the second light-emitting unit; and

g. varying the potential between the first and second electrodes to change the color emission of the device.

30. The method of claim 29 further including varying the duty cycle of the device to compensate for brightness changes due to varying the voltage applied to the device.