Minority carrier lifetime, τB, is one of the key metrics for polycrystalline solar cell absorbers. Based on different spatial carrier-generation profiles obtained using one-photon and two-photon excitation (1PE and 2PE, respectively), we developed a new approach to determine τB in polycrystalline thin films. By comparing time-resolved photoluminescence data measured with 1PE and 2PE, we extract τB and surface recombination velocity S, and resolve charge separation at the pn junction. For coevaporated kesterite (Cu2ZnSnSe4) absorbers, we find S=(0.8-2.1)×104 cm s-1 and τB=7.0±0.5 ns. For corresponding photovoltaic devices, charge separation occurs in 2 ns.
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