Organic electroluminescent device and fabrication methods thereof

An organic electroluminescent device, comprising a pixel element, the pixel element comprising;

• a substrate, comprising a control area and a sensitive area;
• a switch device and a driving device overlying the control area, wherein the switch device has a first active layer, the driving device has a second active layer, wherein the first and second active layers are polysilicon layers;
• a photo diode overlying the sensitive area, wherein the photo diode serves as a photo sensor, wherein the photo diode comprises:
• a third active layer, a fourth active layer, and a fifth active layer, wherein the fifth active layer is connected to both the third and fourth active layers;
• an OLED element disposed in the sensitive area and illuminating to the photo sensor;
• a capacitor coupled to the photo sensor and the driving device;
• a gate dielectric layer disposed overlying the first, the second, the third and the fourth active layers;
• a first gate and a second gate 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
• an interlayer dielectric layer disposed on the gate dielectric layer overlying the sensitive area, the interlayer dielectric layer having a plurality of first openings therein to expose the third and fourth active layers, wherein the first openings are filled with the fifth active layer;
• wherein a photo current corresponding to a brightness of the OLED element is generated by the photo diode responsive to the OLED element illuminating the photo diode such that a 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.