One-Step Synthesis of SnI2•(DMSO)x Adducts for High-Performance Tin Perovskite Solar Cells

Contemporary thin-film photovoltaic (PV) materials contain elements that are scarce (CIGS) or regulated (CdTe and lead-based perovskites), a fact that may limit the widespread impact of these emerging PV technologies. Tin halide perovskites utilize materials less stringently regulated than the lead (Pb) employed in mainstream perovskite solar cells; however, even today's best tin-halide perovskite thin films suffer from limited carrier diffusion length and poor film morphology. We devised a synthetic route to enable in situ reaction between metallic Sn and I-2 in dimethyl sulfoxide (DMSO), a reaction that generates a highly coordinated SnI2 center dot(DMSO)(x) adduct that is well-dispersed in the precursor solution. The adduct directs out-of-plane crystal orientation and achieves a more homogeneous structure in polycrystalline perovskite thin films. This approach improves the electron diffusion length of tin-halide perovskite to 290 +/- 20 nm compared to 210 +/- 20 nm in reference films. We fabricate tin-halide perovskite solar cells with a power conversion efficiency of 14.6% as certified in an independent lab. This represents a similar to 20% increase compared to the previous best-performing certified tin-halide perovskite solar cells. The cells outperform prior earth-abundant and heavy-metal-free inorganic-active-layer-based thin-film solar cells such as those based on amorphous silicon, Cu2ZnSn(S/Se)(4), and Sb-2(S/Se)(3).

Automated summary

This study improved the electron diffusion length and structural homogeneity of tin halide perovskite materials using a synthetic route, resulting in solar cells with a power conversion efficiency of 14.6%.