Organic semiconductors are crystals or thin films composed of carbon-based molecules bonded together though covalent “π-bonds” that provide conductivity. These organic semiconductors can be used for organic photovoltaic (OPV) devices, which show promise as an alternative to traditional solar cells with possible applications in building integrated photovoltaics. As with conventional semiconductors, such as silicon, doping organic semiconductors with specific impurities is needed to improve the electrical properties. One effective method for doping, using 12-molybdophosphoric acid hydrate (PMA), was discovered recently but requires the use of the unstable solvent nitromethane.