Time-resolved recombination analysis in kesterite polycrystalline thin films and photovoltaic devices with one-photon and two-photon excitation

Minority carrier lifetime, tau(B), 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 tau(B) in polycrystalline thin films. By comparing time-resolved photoluminescence data measured with 1PE and 2PE, we extract tau(B) 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) x 10(4) cm s(-1) and tau(B)=7.0 +/- 0.5 ns. For corresponding photovoltaic devices, charge separation occurs in <= 2 ns. (C) 2015 Elsevier B.V. All rights reserved.