Abstract: In past decades, ABX₃ halide perovskites have attracted great interest in solar cells due to excellent optoelectronic properties, such as high carrier mobility. However, instability and toxicity are obstacles on the commercial route for perovskites. Many studies have turned to exploring A₂BX₆ and A₃B₂X₉ for better stability. Unfortunately, the carrier mobilities of these two types are inferior to ABX₃, lower by an order of magnitude. Furthermore, the mobility of ABX₃ is distributed over a large range of 1.78-4500 cm² V^-1 s^-1 in experiments, which contributes to another diversity of mobilities. In this paper, we aim at revealing the physical origin of the above-mentioned diversities by theoretical studies on CsBX₃, Cs₂BX₆, and Cs₃B₂X₉ (B=Sn, Pb, Sb, Bi, X=Br, Cl). The difference in group velocities is the major reason responsible for the variation in these types. The unique three-dimensional connected conductive network of CsBX₃ determines its large group velocity. As for carrier scattering, ionized impurity scattering dominates at low carrier and high ionized impurity concentrations. Detailed analysis reveals that band degeneracy is strongly related to the impurity scattering rate, while dielectric constant is almost immune. Our study provides a better understanding of the relationship between electronic structures and mobilities for potential applications in photovoltaics.

Key words: First-principles calculation, Metal halide perovskite, Electronic structure, Mobility, Ionized impurity scattering