Tunable near-infrared photovoltaic and photoconductive properties of reduced graphene oxide thin films by controlling the number of reduced graphene oxide bilayers

Abstract

Reduced graphene oxide (RGO) thin films with 5, 10, 20, 30 and 50 RGO bilayers were prepared via the layer-by-layer assembly of oppositely charged RGO nanosheets. The effects of the number of RGO bilayers on the electrical, optical and photoelectric (including photovoltaic and photoconductive) properties under 850nm near-infrared laser irradiation of RGO thin films were systematically studied. Results showed that in electrical properties aspect, sheet resistance nonlinearly decreased with increasing the number of RGO bilayers; in optical properties aspect, the transmittance decreased linearly with increasing numbers of RGO bilayers; in photovoltaic properties aspect, the position sensitive photocurrent and offset photocurrent increased linearly with increasing the number of RGO bilayers within a certain bilayers range; in photoconductive properties aspect, the photoconductance first increased and then decreased with increasing the number of RGO bilayers and its maximum occurred at 30 bilayers, and photoresponsivity increased linearly with increasing numbers of RGO bilayers within a certain bilayers range. Photoresponse time of RGO thin film first decreased and then increased with increasing the number of RGO bilayers and the fastest photoresponse time occurred at 30 bilayers. These results are important to guide the design of RGO thin film based near-infrared optoelectronic devices in future.