AMOLED display with optical feedback compensation
In one aspect of the invention, a display includes a substrate, and a plurality of pixels formed on the substrate and arranged in an array. Each pixel has a driving transistor having a gate electrode, a drain electrode and a source electrode, formed on the substrate, an organic light emitting diode (OLED) having a cathode layer, a anode layer and an emissive layer formed between the cathode layer and the anode layer, and formed over the driving transistor such that the anode layer of the OLED is electrically connected to the source electrode of the driving transistor, a bias electrode formed over the substrate, and a photo sensor having a photosensitive layer formed between the anode layer of the OLED and the bias electrode.
1. A display, comprising:
a substrate; and
a plurality of pixels formed on the substrate and arranged in an array, each pixel comprising:
(a) a driving transistor having a gate electrode, a drain electrode and a source electrode, formed on the substrate;
(b) an organic light emitting diode (OLED) having a cathode layer, a anode layer and an emissive layer formed between the cathode layer and the anode layer, and formed over the driving transistor such that the anode layer of the OLED is electrically connected to the source electrode of the driving transistor, wherein the OLED has a light emitting area;
(c) a bias electrode formed over the substrate; and
(d) a photo sensor having a photosensitive layer formed between the anode layer of the OLED and the bias electrode and being in direct contact with the anode layer of the OLED and the bias electrode, wherein the photosensitive layer defines a photo sensing area located in the light emitting area for receiving light emitted from the OLED.
2. The display of claim 1 , wherein the photosensitive layer is formed of a Si-rich dielectric material.
3. The display of claim 1 , wherein the anode layer of the OLED is formed such that at least a portion that overlaps the photosensitive layer of the photo sensor is partially transparent to light emitted from the emissive layer of the OLED.
4. The display of claim 3 , wherein the photo sensor is adapted for measuring brightness of an ambient light that is proportional to light emitted from the OLED and generating a sensing signal corresponding to the measured brightness of the ambient light, wherein the sensing signal is output from the bias electrode and utilized to adjust a driving voltage of the OLED accordingly.
5. The display of claim 4 , wherein the OLED comprises a top-emitting OLED or a bottom-emitting OLED.
6. The display of claim 5 , wherein the photo sensing area is not larger than the light emitting area.
7. The display of claim 1 , wherein the driving transistor comprises an NMOS transistor or PMOS transistor.
8. The display of claim 7 , wherein the driving transistor comprises a back channel etched (BCE) type thin film transistor (TFT), an IS type TFT, a coplanar type TFT, a bottom-gate type TFT, or a top-gate type TFT.
9. A display, comprising:
an active matrix organic light emitting diode (AMOLED) panel having a plurality of pixel arranged in an array, each pixel comprising:
(a) an organic light emitting diode (OLED) having a cathode electrically coupled to a first supply voltage, OVSS, a anode and an emissive layer formed between the cathode and the anode, wherein the OLED has a light emitting area;
(b) a driving circuit having:
(i) a first transistor having a gate, a drain electrically coupled to a second supply voltage, OVDD, and a source electrically coupled to the anode of the OLED;
(ii) a second transistor having a gate electrically coupled to a scan signal, Vscan(N), a drain electrode electrically coupled to the gate of the first transistor, and a source electrode electrically coupled to a data signal, Vdata; and
(iii) a storage capacitor electrically connected between the gate and the drain of the first transistor;
(c) a bias line for outputting a sensing signal, Vbias; and
(d) a photo sensor electrically coupled between the anode of the OLED and the bias line, wherein the photo sensor has a photosensitive layer formed in direct contact with the anode of the OLED, wherein the photo sensor has a photo sensing area located in the light emitting area for receiving light emitted from the OLED.
10. The display of claim 9 , wherein the photo sensor is adapted for measuring brightness of an ambient light that is proportional to light emitted from the OLED and generating the sensing signal Vbias corresponding to the measured brightness of the ambient light, wherein the sensing signal Vbias is output from the bias electrode and utilized to adjust the data signal Vdata.
11. The display of claim 9 , wherein the OLED comprises a top-emitting OLED or a bottom-emitting OLED.
12. The display of claim 9 , wherein the first supply voltage OVSS and the second supply voltage OVDD are a negative supply voltage and a positive supply voltage, respectively.
13. The display of claim 9 , wherein each of the first transistor and the second transistor comprises an NMOS transistor or PMOS transistor.