Pixel structure of an organic light-emitting diode display device and its fabrication method

• US 20020125820A1
• Filed: 03/08/2001
• Published: 09/12/2002
• Est. Priority Date: 09/29/2000
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Wang, Wen-Chun, Yeh, Yung-Hui, Sheu, Chai-Yuan
• Granted Patent: US 6,522,066 B2
• Time in Patent Office: Days
• US Class Current: 313/505
• CPC Class Codes: H10K 50/865 comprising light absorbing layers, e.g. light-blocking layers
• 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

A pixel structure of a full-color organic light-emitting diode (OLED) display device comprises a black matrix, a color changing medium, two thin film transistors, a storage capacitor, and an OLED device arranged on a substrate. The pixel structure of the display device uses blue organic light-emitting diodes or polymer light-emitting diodes as electroluminescent media. The low-temperature poly Si (LTPS) thin film transistors provide a current to the OLED device and serve as an active driving device. The color changing medium changes blue light into red or green light to form full-color OLED. The processing steps include the black matrix process, the island process, the gate process, the interlayer process, the color changing medium process, and the OLED deposition process. Because a color changing medium is integrated on the LTPS thin film transistors, this invention can make display devices of high resolution, high luminous efficiency and wide viewing angle.

Claims

1. A pixel structure of a full-color organic light-emitting diode display device, said pixel structure comprising:

a black matrix region deposited and defined on a top surface of an insulating substrate;

a buffer layer deposited over said black matrix region;

a polycrystalline silicon layer deposited over said buffer layer, said polycrystalline silicon layer having source and drain regions of a first thin-film-transistor and source and drain regions of a second thin-film-transistor defined therein for forming a polycrystalline silicon island;

a gate layer deposited over said polycrystalline silicon island and defining gate electrodes of said first and second thin film transistors therein;

a storage capacitor;

an interlayer deposited over said gate layer and said polycrystalline silicon island and defining source and drain electrode metal regions therein;

a passivation layer deposited over said interlayer;

a color changing medium region defined in said passivation layer;

a layer of transparent conductive material deposited over said color changing medium region and a portion of said passivation layer;

an organic light-emitting diode layer deposited over said layer of transparent conductive material and said passivation layer; and

a cathode metal layer deposited over said organic light-emitting diode layer.

2. The pixel structure of a full-color organic light-emitting diode display device as claimed in claim 1, said organic light-emitting diode layer being electrically connected to the drain electrode of said second thin-film-transistor.

3. The pixel structure of a full-color organic light-emitting diode display device as claimed in claim 1, the drain electrode of said first thin-film-transistor being electrically connected to the gate electrode of said second thin-film-transistor.

4. The pixel structure of a full-color organic light-emitting diode display device as claimed in claim 1, said second thin-film-transistor being a low-temperature poly Si thin-film-transistor for providing current to said organic light-emitting diode layer.

5. The pixel structure of a full-color organic light-emitting diode display device as claimed in claim 1, said second thin-film-transistor being an active driving device.

6. The pixel structure of a full-color organic light-emitting diode display device as claimed in claim 1, the gate electrode of said second thin-film-transistor being electrically connected to said storage capacitor.

7. The pixel structure of a full-color organic light-emitting diode display device as claimed in claim 1, said second thin-film-transistor being in series with said organic light-emitting diode layer and said first thin-film-transistor being in series with said storage capacitor.

8. A method of fabricating a pixel structure of a full-color organic light-emitting diode display device comprising the steps of:

(a) preparing an insulating substrate;

(b) depositing and defining a black matrix region on a top surface of said insulating substrate;

(c) depositing a buffer layer over said black matrix region;

(d) depositing a polycrystalline silicon layer over said buffer layer;

(e) defining source and drain regions of a first thin-film-transistor and source and drain regions of a second thin-film-transistor to form a polycrystalline silicon island by a laser crystallization method and an etching method;

(f) depositing electrode materials to form a gate layer over said polycrystalline silicon island;

(g) depositing an interlayer over said gate layer and said polycrystalline silicon island and depositing and patterning source and drain electrodes by a photolithography process and an etching method;

(h) depositing a passivation layer over said interlayer and forming a color changing medium region in said passivation layer;

(i) depositing a layer of transparent conductive material over said color changing medium region and a portion of said passivation layer;

(j) depositing an organic light-emitting diode layer over said layer of transparent conductive material and said passivation layer; and

(k) depositing a cathode metal layer over said organic light-emitting diode layer.

9. The method of fabricating a pixel structure of a full-color organic light-emitting diode display device as claimed in claim 8, wherein defining source and drain regions of said first thin-film-transistor in step (e) includes doping with N⁺-type dopants over said buffer layer, and defining source and drain regions of said second thin-film-transistor in step (e) includes doping with P⁺-type dopants over said buffer layer.

10. The method of fabricating a pixel structure of a full-color organic light-emitting diode display device as claimed in claim 8, said electrode materials in step (f) including gate oxide and gate metal.

11. The method of fabricating a pixel structure of a full-color organic light-emitting diode display device as claimed in claim 8, said gate layer in step (f) including gate electrodes of said first and second thin film transistors.

12. The method of fabricating a pixel structure of a full-color organic light-emitting diode display device as claimed in claim 8, wherein forming a color changing medium region in step (h) further comprises the steps of:

(h1) etching said passivation layer to define said color changing medium region and a portion of electrode contacting area; and

(h2) filling said color changing medium region with color changing media by spin-coating repeatedly and forming color changing medium patterns of discrete red, green, and blue pixels using photolithography technique.

13. The method of fabricating a pixel structure of a full-color organic light-emitting diode display device as claimed in claim 8, said transparent conductive material in step (i) being indium-tin-oxide.

14. The method of fabricating a pixel structure of a full-color organic light-emitting diode display device as claimed in claim 8, said organic light-emitting diode layer in step (j) using blue organic light-emitting diodes as electroluminescent media.

15. The method of fabricating a pixel structure of a full-color organic light-emitting diode display device as claimed in claim 8, said organic light-emitting diode layer in step (j) using polymer light-emitting diodes as electroluminescent media.