Low Cost Ambient Light Sensing Device based on Sulphided Cu2 O Thin Film Photo-Sensor

Abstract

A standalone ambient light sensing device was constructed by interfacing a sulphided Cuprous Oxide (Cu2 O) thin film semiconductor based photo-sensor. The photo-sensor was custom fabricated by depositing n-type Cu2 O on a titanium substrate followed by a sulphidation process that formed a Cu2 O/Cux S thin film semiconductor heterojunction. Evaporated gold contacts were placed on top of the film. The photo-sensor was operated in the photovoltaic mode and once interfaced to the device, the sensor photovoltage was further amplified and measured through a 10-bit analog to digital voltage converter embedded in a microcontroller. A liquid crystal display was interfaced to the microcontroller to display measurements. Data logging was done directly to the available microcontroller flash memory or through a RS-232 serial communication link to a PC. The sensor was sensitive to a broad range of intensities (0 – 120,000 lux) with a fast photo-response time on the order of a few hundred milliseconds. The available extra microcontroller ports could be utilized for device control and feedback by interfacing other suitable electronics. The total cost of parts for the device was less than US$25.