Highly Mobile Large Polarons in Black Phase CsPbI<sub>3</sub>
Heng Zhang, Elke Debroye, Julian A. Steele, Maarten B. J. Roeffaers, Johan Hofkens, Hai I. Wang, Mischa Bonn
Abstract
We report the band-like\ntransport of photogenerated charge carriers\nwithin all-inorganic black γ-phase CsPbI<sub>3</sub> (γ-CsPbI<sub>3</sub>) thin films, with local mobilities up to 270 ± 44 cm<sup>2</sup>V<sup>–1</sup>s<sup>–1</sup> recorded using\nterahertz (THz) spectroscopy at room temperature. Temperature-dependent,\nhigh-frequency photoconductivity measurements indicate that large\npolaron formation governs charge carrier transport, following the\nFeynman polaron model. The mobility values derived using THz spectroscopy\nare nearly 1 order of magnitude higher than that reported for hybrid\norganic–inorganic lead halide perovskites and approach the\ntheoretical limit for polarons scattering from longitudinal optical\n(LO) phonons. Our results identify γ-CsPbI<sub>3</sub> as a\nfascinating all-inorganic perovskite semiconductor with high charge\ncarrier mobility for optoelectronics and reveal the effect of polaron\nformation on charge transport properties.