Self-Powered UV–Near Infrared Photodetector Based on Reduced Graphene Oxide/n-Si Vertical Heterojunction

A novel self-powered photodetector based on reduced graphene oxide (rGO)/n-Si p-n vertical heterojunction with high sensitivity and fast response time is presented. The photodetector contains a p-n vertical heterojunction between a drop-casted rGO thin film and n-Si. Contacts between the semiconductor layer (rGO, n-Si) and source–drain Ti/Au electrodes allow efficient transfer of photogenerated charge carriers. The self-powered UV–near infrared photodetector shows high sensitivity toward a spectrum of light from 365 to 1200 nm. Under the 600 nm illumination (0.81 mW cm⁻²), the device has a photoresponsivity of 1.52 A W⁻¹, with fast response and recover time (2 ms and 3.7 ms), and the ON/OFF ratios exceed 10⁴ when the power density reaches ≈2.5 mW cm⁻². The high photoresponse primarily arises from the built-in electric field formed at the interface of n-Si and rGO film. The effect of rGO thickness, rGO reduction level, and layout of rGO/n-Si effective contact area on device performance are also systematically investigated.