Carrier transport mechanisms and photovoltaic characteristics of p-H2Pc/n-Si heterojunctions

Heterojunction cells of p-H₂Pc/n-Si were fabricated by vacuum deposition of p-H₂Pc thin films onto n-Si single crystals. Measurements of the current-voltage (I-V) and the capacitance—voltage (C-V) characteristics have been evaluated to identify the mechanisms of barrier formation and, consequently, current flow. The forward current involves tunneling and could be explained by a multi-step tunneling recombination model due to a high density of interface defects. The C-V characteristics indicate an abrupt heterojunction model. The devices exhibit strong photovoltaic characteristics with an open-circuit voltage of 0.34 V, a short-circuit current density of 17.5 mA/cm² and a power conversion efficiency of 1.5%. These parameters have been estimated at room temperature and under constant illumination of 150 mW/cm².