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.