Organic Schottky barrier photovoltaic cells based on MoOx/C60

We report that the performance of indium tin oxide/molybdenum oxide/fullerene (ITO/MoOx/C-60) 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/C-60 cells is consistent with MoOx functioning as the Schottky barrier contact. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3415497]