LED DEVICE HAVING IMPROVED CONTRAST

• US 20090051283A1
• Filed: 08/21/2007
• Published: 02/26/2009
• Est. Priority Date: 08/21/2007
• Status: Active Grant

• Current Assignee: Global OLED Technology LLC (LG Display Co., Ltd.)
• Original Assignee: Global OLED Technology LLC (LG Display Co., Ltd.)
• Inventors: Preuss, Donald R., Tyan, Yuan-Sheng, Shore, Joel D., Cok, Ronald S.
• Granted Patent: US 7,859,188 B2
• Time in Patent Office: Days
• US Class Current: 313/506
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair
• CPC Class Codes: H10K 50/854 comprising scattering means
• CPC Class Codes: H10K 50/86 Arrangements for improving contrast, e.g. preventing reflection of ambient light
• CPC Class Codes: H10K 59/351 comprising more than three subpixels, e.g. red-green-blue-white [RGBW]
• CPC Class Codes: H10K 59/38 comprising colour filters or colour changing media [CCM]
• CPC Class Codes: H10K 59/876 comprising a resonant cavity structure, e.g. Bragg reflector pair
• CPC Class Codes: H10K 59/877 comprising scattering means
• CPC Class Codes: H10K 59/8791 Arrangements for improving contrast, e.g. preventing reflection of ambient light

Abstract

A light-emitting diode device, including a substrate; and a reflective electrode and a semi-transparent electrode formed over the substrate and an unpatterned white light-emitting layer formed between the reflective electrode and the semi-transparent electrode, the reflective electrode, semi-transparent electrode, and unpatterned white-light-emitting layer forming an optical microcavity, and wherein either the reflective or semi-transparent electrodes is patterned to form a plurality of independently controllable light-emitting elements with at least one light-emitting element having no color filter. Color filters are formed over a side of the semi-transparent electrodes opposite the unpatterned white light-emitting layer in correspondence with the light-emitting elements, the color filters having at least two different colors. Additionally, a reflected-light absorbing layer is located over all of the light-emitting elements.

Claims

1. A light-emitting diode device, comprising:

a) a substrate;

b) a reflective electrode and a semi-transparent electrode formed over the substrate and an unpatterned white light-emitting layer formed between the reflective electrode and the semi-transparent electrode, the reflective electrode, semi-transparent electrode, and unpatterned white-light-emitting layer forming an optical microcavity, and wherein either the reflective or semi-transparent electrode is patterned to form a plurality of independently controllable light-emitting elements;

c) a plurality of color filters formed over a side of the semi-transparent electrodes opposite the unpatterned white light-emitting layer in correspondence with the light-emitting elements, the plurality of color filters having at least two different colors and wherein at least one light-emitting element has no color filter; and

d) a reflected-light absorbing layer located over all of the light-emitting elements.

2. The light-emitting diode device of claim 1 wherein the reflected-light absorbing layer is a circular polarizer.

3. The light-emitting diode device of claim 1 wherein the device is a top-emitter device.

4. The light-emitting diode device of claim 1 wherein the device is a bottom-emitter device.

5. The light-emitting diode device of claim 1 wherein the optical microcavity of each light-emitting element having a color filter is tuned to emit light at a peak wavelength approximately corresponding to the peak transmission wavelength of the color filter.

6. The light-emitting diode device of claim 1 further comprising a light-scattering layer that scatters light emitted by the at least one light-emitting element that has no color filter.

7. The light-emitting diode device of claim 6 wherein the reflective electrode comprises a reflective layer and a transparent conductive layer, and the light-scattering layer is formed between the reflective and transparent conductive layers.

8. The light-emitting diode device of claim 6 wherein the light-scattering layer is formed on a side of the semi-transparent electrode opposite the white light-emitting layer.

9. The light-emitting diode device of claim 1 wherein the at least one light-emitting element that has no color filter comprises a plurality of optical microcavities, each optical microcavity tuned to emit light at a different wavelength.

10. The light-emitting diode device of claim 9 wherein the optical microcavities of the at least one light-emitting element that has no color filter are tuned to emit colors that, in combination, are perceived as white.

11. The light-emitting diode device of claim 9 wherein the optical microcavities of the at least one light-emitting element that has no color filter are tuned to emit complementary colors of light.

12. The light-emitting diode device of claim 11 wherein the optical microcavities of the at least one light-emitting element that has no color filter are tuned to emit blue and yellow light or red and cyan light.

13. The light-emitting diode device of claim 9 wherein the optical microcavities are tuned to emit primary colors of light.

14. The light-emitting diode device of claim 9 wherein the optical microcavities are tuned to emit red, green, yellow, cyan, or blue light.

15. The light-emitting diode device of claim 1, wherein the white light-emitting layer comprises organic materials.

16. The light-emitting diode device of claim 1 wherein the white light-emitting layer comprises inorganic quantum dots formed in a poly-crystalline semiconductor matrix.

19. The light-emitting diode device of claim 1 wherein the white light-emitting layer emits light having a spectrum with two or more peaks, wherein at least one of the peaks has a peak frequency corresponding to the frequency at which the microcavity is tuned.

17. A method of making the LED device, comprising the steps of:

a) forming a substrate;

b) forming a reflective electrode and a semi-transparent electrode over the substrate;

c) forming an unpatterned white light-emitting layer between the reflective electrode and the semi-transparent electrode;

wherein the reflective electrode, semi-transparent electrode, and unpatterned white-light-emitting layer form an optical microcavity, and wherein either the reflective or semi-transparent electrodes is patterned to form a plurality of independently controllable light-emitting elements;

d) forming a plurality of color filters over a side of the semi-transparent electrode opposite the unpatterned white light-emitting layer in correspondence with the light-emitting elements, the plurality of color filters having at least two different colors and wherein at least one light-emitting element has no color filter; and

e) forming a reflected-light absorbing layer over all of the light-emitting elements.

18. A display system comprising:

an LED device, including;

a) a substrate;

b) a reflective electrode and a semi-transparent electrode formed over the substrate and a unpatterned white light-emitting layer formed between the reflective electrode and the semi-transparent electrode, the reflective electrode, semi-transparent electrode, and unpatterned white-light-emitting layer forming an optical microcavity, and wherein either the reflective or semi-transparent electrodes is patterned to form a plurality of independently controllable light-emitting elements;

c) a plurality of color filters formed over a side of the semi-transparent electrode opposite the unpatterned white light-emitting layer in correspondence with the light-emitting elements, the plurality of color filters having at least two different colors and wherein at least one light-emitting element has no color filter;

d) a reflected-light absorbing layer located over all of the light-emitting elements; and

e) a controller that drives the LED device in response to a display signal.