Diverse carrier mobilities in halide perovskites: The role of conductive network and ionized impurity scattering

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.