Microwave plasma-assisted regeneration of carbon nanosheets with bi- and trilayer of graphene and their application to photovoltaic cells

Vertically aligned carbon nanosheets (CNSs) with bi- and trilayer graphene have been achieved on various metal substrates from solid carbon sources by irradiation with H2 and Ar plasma. The resulting graphene structures have fewer layers, bigger sizes, and higher graphitization compared to previous reports obtained from gas sources, as confirmed by scanning and transmission electron microscopes, Raman and X-ray photoelectron spectroscopes. The results suggest that the interaction between the plasma (of H2 and Ar) and carbon sources favors the formation of bigger and thinner nucleation cites in the initial stage and atomic H etching dominates during the whole thinner CNS growth. The vertically aligned graphene film can be directly transferred on as-patterned SiO2/Si to form a heterojunction photovoltaic cell with a power conversion efficiency of 0.9%.