Organic light-emitting display device including a photo diode

An organic light emitting display device including: a substrate having a pixel region and a non-pixel region; a first buffer layer and a second buffer layer formed over the substrate; a thin film transistor formed over the second buffer layer; an organic light emitting device formed in the pixel region and electrically connected with the thin film transistor; and a photo diode formed in the non-pixel region, for receiving external light of red wavelength at a certain absorption rate, and for controlling brightness of the organic light emitting device. Here, the first buffer layer can be formed to be from 2900 to 3100 in thickness, the second buffer layer can be formed to be from 200 to 400 in thickness, and the photo diode can include: an N-type doping region, a channel region being from 3 to 10 μm in width, and a P-type doping region.