Ion migration is a notorious phenomenon 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 (E a ) in THPs, which remain nearly constant under illumination. We further figured out the threshold E a for the absence of ion migration to be around 0.65 eV using the CsSn y Pb 1-y -(I 0.6 Br 0.4 ) 3 system whose E a 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.
We demonstrate a heterostructure NiS/MoS hybrid with tight interface synthesized via an improved hydrothermal method. As compared to pure MoS, the increased surface area and the shorten charge transport pathway in the layered hybrid significantly promote the photocatalytic efficiency for hydrogen evolution reaction (HER). In particularly, the optimized NiS/MoS hybrid with 20 wt % NiS exhibits the highest photocatalytic activity with HER value of 406 μmolgh, which is enhanced by 70% compared to that of pure MoS nanosheets (285.0 μmolgh). Moreover, the value is 4 times more than the commercial MoS (92.0 μmolgh), indicating the high potential of the hybrid in the catalytic fields.
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