Organic electroluminescent devices and fabrication methods thereof

1. An organic electroluminescent device, comprising:

a pixel element comprising:

a substrate comprising a control area and a sensitive area;

a switch device and a driving device overlying the control area;

a photo sensor overlying the sensitive area;

an OLED element disposed in the sensitive area and operative to illuminate the photo sensor; and

a capacitor coupled to the photo sensor and the driving device;

wherein a photo current corresponding to a brightness of the OLED element is generated by the photo sensor responsive to the OLED element illuminating the photo sensor such that a the voltage of the capacitor is adjusted by the photo current to control the current passing through the driving device, thus changing the illumination of the OLED element,

wherein the switch device and the driving device are top gate transistors, and the photo sensor is an amorphous silicon bottom gate transistor.

2. The organic electroluminescent device as claimed in claim 1 , wherein the pixel element is formed of multiple layers, and the switch device, the driving device, and the photo sensor have gates located in the same one of the layers.

3. The organic electroluminescent device as claimed in claim 1 , further comprising:

a first active layer disposed in the switch device;

a second active layer disposed in the driving device; and

a gate dielectric layer disposed overlying the first and second active layers and the sensitive area.

4. The organic electroluminescent device as claimed in claim 3 , further comprising:

first and second gates disposed on the gate dielectric layer overlying the control area, wherein the first gate is in the switch device, and the second gate is in the driving device; and

a third gate disposed on the gate dielectric layer overlying the sensitive area, wherein the first, second, and third gates are of the same layer.

5. The organic electroluminescent device as claimed in claim 4 , further comprising:

a dielectric layer at least covering the first, second, and third gates; and

a third active layer disposed overlying a portion of the dielectric layer overlying the sensitive area.

6. The organic electroluminescent device as claimed in claim 5 , further comprising:

a photo sensor doped layer disposed overlying the third active layer; and

a photo sensor source and a photo sensor drain electrically connecting opposite sides of the photo sensor doped layer respectively.

7. The organic electroluminescent device as claimed in claim 3 , wherein the dielectric layer further comprises a plurality of openings, exposing the first and second gates and a portion of the first and second active areas, and the openings are filled with conductive contacts.

8. The organic electroluminescent device as claimed in claim 7 , further comprising:

a passivation layer disposed overlying the conductive contacts, the dielectric layer, the photo sensor source and the photo sensor drain; and

a planarization layer disposed overlying the passivation layer and underlying the photo sensor.

9. The organic electroluminescent device as claimed in claim 8 , further comprising:

a first electrode overlying the planarization layering layer;

an organic light emitting layer disposed on the first electrode; and

a second electrode disposed overlying the organic light emitting layer, wherein the first electrode, the organic light emitting layer and the second electrode forms together the OLED element.

10. The organic electroluminescent device as claimed in claim 1 , further comprising:

a display panel, wherein the pixel element is arranged in an array of pixel elements of the display panel.

11. The organic electroluminescent device as claimed in claim 10 , further comprising:

an input unit coupled to the display panel and operative to provide input to the display panel such that they display panel displays images.

12. The organic electroluminescent device as claimed in claim 10 , further comprising:

means for providing input to the display panel.

13. The organic electroluminescent device as claimed in claim 10 , wherein the display panel is a portion of an electronic device.

14. The organic electroluminescent device as claims in claim 1 , wherein the switch device has a first active layer, the driving device has a second active layer, and the photo sensor has a third active layer,

wherein the second active layer and the third active layer are formed in different levels.

15. The organic electroluminescent device as claims in claim 1 , wherein the switch device has a first active layer, the driving device has a second active layer, and the photo sensor has a third active layer,

wherein the second active layer and the third active layer are of different materials.

16. The organic electroluminescent device as claimed in claim 15 , wherein the second active layer is a polysilicon layer, and the third active layer is an amorphous silicon layer.

17. The organic electroluminescent device as claimed in claim 16 , wherein the first active layer is a polysilicon layer.

18. An organic electroluminescent device, comprising:

a substrate comprising a control area and a sensitive area;

a switch device and a driving device overlying the control area;

a photo sensor overlying the sensitive area; and

an OLED element disposed in the sensitive area and operative to illuminate the photo sensor;

a capacitor coupled to the photo sensor and the driving device;

wherein a photo current corresponding to a brightness of the OLED element is generated in the photo sensor responsive to the OLED element illuminating on the photo sensor such that a the voltage of the capacitor is adjusted by the photo current to control the current passing through the driving device, thus changing the illumination of the OLED element,

wherein the switch device is a top gate transistor, and the photo sensor is a bottom gate transistor.

19. A method for forming an organic electroluminescent device, comprising:

providing a substrate comprising a control area and a sensitive area;

forming an active layer overlying the control area of the substrate;

forming a gate dielectric layer overlying the active layer and the sensitive area of the substrate;

forming a conductive layer on the gate dielectric layer;

patterning the conductive layer to form first and second gates in the control area, and a third gate in the sensitive area;

forming a dielectric layer at least covering the first, second, and third gates;

forming a photo sensor active layer on a portion of the dielectric layer overlying the sensitive area;

forming a photo sensor doped layer on the photo sensor active layer;

forming a photo sensor source and a photo sensor drain electrically connecting opposite sides of the photo sensor doped layer respectively; and

forming an OLED element overlying a portion of the control area and the sensitive area.