Hidden Spontaneous Polarisation in the ns^2-Cation Sn2SbS2I3 Chalcohalide Photovoltaic Absorber

Open-access Materials Horizons paper at: https://doi.org/10.1039/D1MH00764E, featured on the front cover! 🤩 Enormous research efforts are currently devoted to the discovery of ‘perovskite-inspired materials’, aiming to replicate the astonishing optoelectronic performance of lead-halide perovskites (LHPs). Recently, chalco halides of group IV/V elements have attracted attention due to the stability provided by stronger metal-chalcogen bonds, alongside compositional flexibility and ns2 cations — a performance-defining feature of LHPs. Following the experimental report of stable, solution-grown tin-antimony sulfoiodide (Sn2SbS2I3) solar cells, with power conversion efficiencies above 4%, we comprehensively characterise the structural and electronic properties of this emerging material. We find that the experimentally-reported centrosymmetric Cmcm crystal structure represents an average over multiple polar Cmc2_1 configurations. This dynamic crystal structure and ferroelectric behaviour could benefit photovoltaic performance. Using state-of-the-art ab initio methods, we assess the efficiency limits of this material, finding maximal solar-conversion efficiencies η_max > 30 %with film thicknesses t > 0.5μm, at the radiative limit. YouTube talks on this and other works here. The AiiDA database and repository for this project is available on the Materials Cloud archive server here: 10.24435/materialscloud:ge-qt.本研究相关的开放获取论文已发表于《Materials Horizons》（材料视野），DOI链接为：https://doi.org/10.1039/D1MH00764E，该论文还被选为当期封面文章！🤩 当前学界投入大量研究精力开发“类钙钛矿材料”，旨在复刻卤化铅钙钛矿（lead-halide perovskites，缩写LHPs）优异的光电子性能。近年来，IV/V族元素的硫族卤化物凭借更强的金属-硫族键所带来的稳定性、组分灵活性以及ns2型阳离子（卤化铅钙钛矿性能的核心决定特征）受到广泛关注。在学界首次报道采用溶液法制备的稳定硫碘化锡锑（Sn2SbS2I3）太阳能电池光电转换效率突破4%之后，本研究对该新兴材料的结构与电子性质开展了全面表征。研究发现，实验中报道的中心对称Cmcm晶体结构，实则为多种极性Cmc2_1构型的平均结构。这种动态晶体结构与铁电特性，有望对光伏性能产生积极影响。本研究采用当前顶尖的从头算（ab initio）方法，评估了该材料的效率极限，结果表明在辐射极限条件下，当薄膜厚度大于0.5μm时，其最大太阳能转换效率η_max可突破30%。相关主题及其他研究的YouTube演讲视频可点击此处获取。本项目的AiiDA数据库与代码仓库已上传至Materials Cloud存档服务器，访问地址为：10.24435/materialscloud:ge-qt。