Thermal annealing effects on graphene/n-Si Schottky junction solar cell: removal of PMMA residues

Thermal annealing is one of the most effective ways to improve the efficiency of a graphene/n-Si Schottky junction solar cell. Here, its underlying mechanism has been investigated by comparative studies in terms of the removal of polymethyl methacrylate (PMMA) residues, using the J – V characteristics and transient photocurrent and photovoltage measurements. The obtained results have revealed that there are trap states that originate from the PMMA residues and cause the large photocurrent leakage as the intensity of the incident light increases. It is also found that the PMMA residues accelerate deterioration and rapidly invalidate hole doping effects. Such undesirable PMMA residues were effectively removed by the thermal annealing treatments, serving to reduce the photocurrent leakage and increase the stability.