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Negligible ion migration in Tin-based and Tin-doped perovskites.

Ion migration is a notorious phenomena observed in ionic perovskite materials. It causes several severe issues in perovskite optoelectronic devices such as instability, current hysteresis, and phase segregation. Here, we report that, in contrast to lead halide perovskites (LHPs), no ion migration or phase segregation was observed in tin halide perovskites (THPs) under illumination or an electric field. The origin is attributed to a much stronger Sn-halide bond and higher ion migration activation energy (Ea) in THPs, which remain nearly constant under illumination. We further figured out the threshold Ea for the absence of ion migration to be around 0.65 eV using the CsSnyPb1-y(I0.6Br0.4)3 system whose Ea varies with Sn ratios. Our work shows that ion migration does not necessarily exist in all perovskites and suggests metallic doping to be a promising way of stopping ion migration and improving the intrinsic stability of perovskites.