Ultrafast terahertz probe of photoexcited free charge carriers in organometal CH 3 NH 3 PbI 3 perovskite thin film

By using optical pump–terahertz probe (OPTP) experiments, we study the free charge carrier dynamics in photoexcited drop-cast CH 3 NH 3 PbI 3 -based perovskite thin film at room temperature. Compared with the pump photon energy at 1.55 eV, the measured OPTP signal following excitation of 3.1 eV shows an additional fast decay channel of the photoconductivity. Our experimental results demonstrate that effective carrier lifetime can be strongly modulated by surface recombination. In addition, the Drude-Smith-like transient terahertz photoconductivity spectra suggest that photogenerated free carriers experience backscattering at grain boundaries in our solution-processed perovskite films studied here.