Band-Like Charge Transport in Cs₂AgBiBr₆ and Mixed Antimony–Bismuth Cs₂AgBi_1–<i>x</i>Sb_<i>x</i>Br₆ Halide Double Perovskites

Recently, halide double perovskites (HDPs), such as Cs2AgBiBr6, have been reported as promising nontoxic alternatives to lead halide perovskites. However, it remains unclear whether the charge-transport properties of these materials are as favorable as for lead-based perovskites. In this work, we study the mobilities of charges in Cs2AgBiBr6 and in mixed antimony–bismuth Cs2AgBi1–xSbxBr6, in which the band gap is tunable from 2.0 to 1.6 eV. Using temperature-dependent time-resolved microwave conductivity techniques, we find that the mobility is proportional to T–p (with p ≈ 1.5). Importantly, this indicates that phonon scattering is the dominant scattering mechanism determining the charge carrier mobility in these HDPs similar to the state-of-the-art lead-based perovskites. Finally, we show that wet chemical processing of Cs2AgBi1–xSbxBr6 powders is a successful route to prepare thin films of these materials, which paves the way toward photovoltaic devices based on nontoxic HDPs with tunable band gaps