Mechanistic view on efficient photodetection by solvothermally reduced graphene oxide

Despite of the progress, graphene based photodetectors still suffer from very low responsivity. Tunable optical properties and ease of preparation of has made reduced graphene oxide (RGO) a promising substitute material for graphene in many optoelectronic applications. We have studied solvothermal reduction of graphene oxide in ethylene glycol and photodetection properties of as made RGO based devices. In near infrared region a responsivity value as high as 0.78 A W-1 with an external quantum efficiency of 62% has been achieved at a bias of only 0.5 V. Corresponding values in ultraviolet region are 0.27 A W-1 and 102%. Few layer nature and increased reduction can increase absorption efficiency of RGO. Defects in graphene sheets in RGO create mid-gap states band (MGB). MGB can generate gain in photocurrent by preventing quick recombination of photogenerated charge carriers. Increased absorption and longer carrier lifetime enhances the performance of RGO based devices. Also a linear variation of photocurrent in RGO with temperature indicates its potential as temperature sensor.