Temperature-Dependent Ambipolar Charge Carrier Mobility in Large-Crystal Hybrid Halide Perovskite Thin Films

Perovskite-based thin-film solar cells today reach power conversion efficiencies of more than 22%. Methylammonium lead iodide (MAPI) is prototypical for this material class of hybrid halide perovskite semiconductors and at the focal point of interest for a growing community in research and engineering. Here, a detailed understanding of the charge carrier transport and its limitations by underlying scattering mechanisms is of great interest to the material's optimization and development. In this article, we present an all-optical study of the charge carrier diffusion properties in large-crystal MAPI thin films in the tetragonal crystal phase from 170 K to room temperature. We probe the local material properties of individual crystal grains within a MAPI thin film and find a steady decrease of the charge carrier diffusion constant with increasing temperature. From the resulting charge carrier mobility, we find a power law dependence of mu proportional to T-m with m = -(1.8 +/- 0.1). We further study the temperature-dependent mobility of the orthorhombic crystal phase from 50 to 140 K and observe a distinctly different exponent of m = -(1.2 +/- 0.1).