Organic Schottky barrier photovoltaic cells based on $MoOx/C60$

We report that the performance of indium tin oxide/molybdenum oxide/fullerene $(ITO/MoOx/C60)$ photovoltaic cells is highly sensitive to the method of depositing $MoOx$ film. The highest open-circuit voltage and short-circuit current are obtained using thermally evaporated $MoOx$⁠. In contrast, sputtered $MoOx$ produces lower efficiencies. X-ray and ultraviolet photoemission analyses indicate that pristine thermally evaporated $MoOx$ has a high work function of 6.8 eV and $Mo6+$ oxidation state, whereas argon-sputtered $MoOx$ is characterized by lower work function and coexistence of both $Mo6+$ and $Mo5+$ states. The photovoltaic performance of the $ITO/MoOx/C60$ cells is consistent with $MoOx$ functioning as the Schottky barrier contact.