A photodiode is a semiconductor device that converts light into an electrical current. It is a form of light-weight sensor that converts light energy into electrical voltage or current. Photodiode is a type of semi conducting device with PN junction. Between the p (positive) and n (negative) layers, an intrinsic layer is present. The photo diode accepts light energy as input to generate electric current. Photodiodes are used in consumer electronics devices such as compact disc players, smoke detectors, medical devices.