Designing photovoltaic cells for indoor energy harvesting systems

Recent research focuses on developing photovoltaic cells that are optimized for indoor conditions and therefore suitable for photovoltaic energy harvesting in micro systems. The available conditions for indoor photovoltaic cells are investigated and discussed concerning intensity and spectra. The influence of the parallel and series resistances on the efficiency of crystalline and amorphous Silicon devices with decreasing intensity are discussed and compared to simulations with the two diode model. For low intensities as present indoors (< 1 mW cm -2) the parallel resistance restricts the achievable efficiency and needs therefore to be optimized.