Highly Mobile Large Polarons in Black Phase CsPbI3

Abstract

We report the band-like transport of photogenerated charge carriers within all-inorganic black γ-phase CsPbI3 (γ-CsPbI3) thin films, with local mobilities up to 270 ± 44 cm2V-1s-1 recorded using terahertz (THz) spectroscopy at room temperature. Temperature-dependent, high-frequency photoconductivity measurements indicate that large polaron formation governs charge carrier transport, following the Feynman polaron model. The mobility values derived using THz spectroscopy are nearly 1 order of magnitude higher than that reported for hybrid organic-inorganic lead halide perovskites and approach the theoretical limit for polarons scattering from longitudinal optical (LO) phonons. Our results identify γ-CsPbI3 as a fascinating all-inorganic perovskite semiconductor with high charge carrier mobility for optoelectronics and reveal the effect of polaron formation on charge transport properties.