Abstract
Tin is the frontrunner for substituting toxic lead in perovskite solar cells. However, tin suffers the detrimental oxidation of SnII to SnIV. Most of reported strategies employ SnF2 in the perovskite precursor solution to prevent SnIV formation. Nevertheless, the working mechanism of this additive remains debated. To further elucidate it, we investigate the fluoride chemistry in tin halide perovskites by complementary analytical tools. NMR analysis of the precursor solution discloses a strong preferential affinity of fluoride anions for SnIV over SnII, selectively complexing it as SnF4. Hard X‐ray photoelectron spectroscopy on films shows the lower tendency of SnF4 than SnI4 to get included in the perovskite structure, hence preventing the inclusion of SnIV in the film. Finally, small‐angle X‐ray scattering reveals the strong influence of fluoride on the colloidal chemistry of precursor dispersions, directly affecting perovskite crystallization.
Highlights
Metal halide perovskite materials have shown enormous potential for the processing of efficient and stable photovoltaics.[1]
With the help of hard X-ray photoelectron spectroscopy (HAXPES) analysis, we show how SnF2 increases the SnII content in perovskite samples, an indication that SnIV is partially prevented from being incorporated in the perovskite film
Angewandte Chemie International Edition published by Wiley-VCH GmbH Angew
Summary
Metal halide perovskite materials have shown enormous potential for the processing of efficient and stable photovoltaics.[1]. We explain the origin of the beneficial effects of SnF2 in the processing and stability to oxidation of tin halide perovskites by studying the chemistry of fluoride in these solutions.
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