One-Step Synthesis of SnI<sub>2</sub>·(DMSO)<sub><i>x</i></sub> Adducts for High-Performance Tin Perovskite Solar Cells
Xianyuan Jiang, Hansheng Li, Qi‐Lin Zhou, Qi Wei, Mingyang Wei, Luozhen Jiang, Zhen Wang, Zijian Peng, Fei Wang, Zihao Zang, Kaimin Xu, Yi Hou, Sam Teale, Wenjia Zhou, Rui Si, Xingyu Gao, Edward H. Sargent, Zhijun Ning
Abstract
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 I2 in dimethyl sulfoxide (DMSO), a reaction that generates a highly coordinated SnI2·(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 ∼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 Sb2(S/Se)3.