The effects of non-uniform lifetime on photoluminescence decay and solar cell performance: A thin-film CdSeTe case study

Carrier lifetime is a key component of polycrystalline thin-film solar cell performance. Lifetime measurement interpretations often rely on simplified one-dimensional models with a singular bulk lifetime. Yet TRPL imaging data here reveals significant grain-to-grain lateral lifetime variation, depth inhomogeneity, and grain boundary recombination in state-of-the-art CdSeTe solar cells. Analysis and computational modeling indicate that short lifetime regions in thin film solar cells have an overweighted impact on device performance. Hence, the standard approach of fitting the latter section of decay curves significantly overestimates the effective device lifetime and corresponding solar cell performance. Lifetime imaging with sub-micron spatial resolution provides a far more realistic assessment of recombination, a means to assess the underlying mechanisms contributing to good and bad regions, and thereby a means to enhance carrier lifetime and thin-film solar cell performance.