Minority Carrier Lifetime Analysis in the Bulk of Thin-Film Absorbers Using Subbandgap (Two-Photon) Excitation

We describe a new time-resolved photoluminescence (TRPL) analysis method for the determination of minority carrier lifetime tau(B). This analysis is based on subbandgap excitation (two-photon excitation, or 2PE) and allows selective lifetime determination at the surface or in the bulk of semiconductor absorbers. We show that for single-crystal CdTe, tau(B) could be determined even if surface recombination velocity is >10(5) cm s(-1). Two-photon excitation TRPL measurements indicate that radiative lifetime in undoped CdTe is >> 66 ns. We also compare one-photon excitation (1PE) and 2PE TRPL data for polycrystalline CdS/CdTe thin films.