B-Site Mixing Effects in Hybrid Perovskites: Phase Transitions and Dielectric Response of MAPb_1–<i>x</i>Sn_<i>x</i>Br₃

Ion-mixing is a highly effective strategy for tuning the performance and stability of photovoltaic devices based on hybrid perovskites. Despite many works concentrating on the A- and X-site mixing effects, a comprehensive study on the effects of B-site mixing on the structural and dynamic properties of MA-based perovskites is still absent. In this work, we investigate the structural and dynamic properties of mixed lead-tin halide perovskites MAPb_1-<i>x</i> Sn _<i>x</i> Br₃ using a multitechnique experimental approach including differential scanning calorimetry, dielectric spectroscopy, and nuclear quadrupole resonance experiments. We map the phase diagram of this system, which reveals that B-site mixing slightly stabilizes the cubic phase and affects the MA cation dynamics and ordering, although the observed effects are less prominent compared with A- and X-site mixing. Our results provide insights into the complex interplay of structural and dynamic properties in mixed-metal perovskites contributing to their potential optimization for photovoltaic applications.