Eco-friendly and simple radiation-based preparation of graphene and its application to organic solar cells

We report the reduction of graphene oxide (GO) through an eco-friendly and simple radiation-based method and the practical application of the resulting radiation-reduced GO (RRGO) as a solution-processable hole-transporting layer (HTL) for organic solar cells. GO dispersed in N, N′-dimethylformamide (DMF) was irradiated by γ-rays at various absorbed doses. The analytical results revealed that GO in DMF was effectively reduced to RRGO by γ-ray irradiation-induced deoxygenation, and that the reduction degree was dependent on the absorbed dose. The electrical conductivity of RRGO increased up to 12.7 S cm^-1 with an increase in the absorbed dose, whereas the work function decreased to 4.34 eV. An organic solar cell device with RRGO prepared at 50 kGy as an HTL exhibited the best performance, with a power conversion efficiency of 2.72%, which is a better cell efficiency than is possible in devices with conventional GO and solvothermally-reduced GO.