Abstract: The present disclosure describes an embodiment of a thin film transistor based light sensor circuit. The thin film transistor based light sensor circuit includes two thin film transistors, in which a channel region of one of the thin film transistors includes a light sensing area and a channel region of the other thin film transistor has a capping material disposed thereon. The thin film transistor based light sensor circuit further includes a comparator device electrically coupled to the two thin film transistors and configured to detect a current difference between the thin film transistors in response to the thin film transistor with the channel region having the light sensing area being exposed to light.