Organic light emitting diode display

1. An organic light emitting diode (OLED) display comprising:

a substrate;

an organic light emitting element including a first electrode, an organic emission layer, and a second electrode on the substrate;

a driving thin film transistor that turns on/off first power supplied to the first electrode, and including a first active layer including zinc oxide (ZnO);

a photo sensor disposed between the substrate and the organic emission layer, and including a second active layer that senses light emitted from the organic emission layer, the photo sensor including a sensor input end and a sensor output end contacting respective ends of the second active layer,

a sensing thin film transistor connected with the sensor input end of the photo sensor; and

a controller controlling at least one of the first power and a second power supplied to the second electrode according to an intensity of light sensed by the photo sensor.

2. The OLED display as claimed in claim 1 , wherein the second active layer includes amorphous silicon.

3. The OLED display as claimed in claim 2 , further comprising a switching thin film transistor that turns on a third power that controls the driving thin film transistor and including a third active layer.

4. The OLED display as claimed in claim 3 , wherein the third active layer includes the same material as the first active layer.

5. The OLED display as claimed in claim 3 , wherein the third active layer includes the same material as the second active layer.

6. The OLED display as claimed in claim 1 , further comprising a light blocking layer disposed between the second active layer and the substrate.

7. The OLED display as claimed in claim 6 , wherein the light blocking layer contacts the second active layer.

8. The OLED display as claimed in claim 6 , wherein the light blocking layer comprises at least one of titanium nitride (TiN x ) and aluminum nitride (AlN x ).