Femtosecond-laser photoemission spectroscopy for ultrafast photovoltage dynamics: limitations and possibilities

The possibility of evaluating minority-carrier mobility and lifetime by measuring fast photovoltage dynamics of completed cells via time-resolved photoemission spectroscopy is investigated. A numerical simulation based on drift-diffusion model is performed to investigate how mobility and lifetime can be extracted. A simulation assuming a constant lifetime shows that photovoltage decay reflects carrier lifetime over two orders of magnitude of the photo-injection level while photoluminescence decay does not. The possibility of a detailed analysis on recombination mechanisms is discussed. The discrepancy in the magnitude of photovoltage observed in the previous measurement was investigated. The contribution from surface band-bending is discussed.