Perovskite-inspired materials aim to replicate the optoelectronic performance of lead-halide perovskites, while eliminating issues with stability and toxicity. Chalcohalides of group IV/V elements have attracted attention due to enhanced stability provided by stronger metal-chalcogen bonds, alongside compositional flexibility and ns2 lone pair cations-a performance-defining feature of halide perovskites. Following the experimental report of solution-grown tin-antimony sulfoiodide (Sn2SbS2I3) solar cells, with power conversion efficiencies above 4%, we assess the structural and electronic properties of this emerging photovoltaic material. We find that the reported centrosymmetric Cmcm crystal structure represents an average over multiple polar Cmc21 configurations. The instability is confirmed through a combination of lattice dynamics and molecular dynamics simulations. We predict a large spontaneous polarisation of 37 μC cm-2 that could be active for electron-hole separation in operating solar cells. We further assess the radiative efficiency limit of this material, calculating ηmax > 30% for film thicknesses t > 0.5 μm.
Bibliographical noteFunding Information:
Seán R. Kavanagh thanks Dr Bonan Zhu for help with using the AiiDA infrastructure, Gabriel Krenzer for advice regarding molecular dynamics simulations, and Matthew Okenyi for useful discussions regarding Landau theory of hysteresis behaviour. SRK acknowledges the EPSRC Centre for Doctoral Training in the Advanced Characterisation of Materials (CDT-ACM)(EP/ S023259/1) for funding a PhD studentship. CNS is grateful to the Ramsay Memorial Fellowship Trust and UCL Department of Chemistry for the funding of a Ramsay Fellowship. DOS acknowledges support from the EPSRC (EP/N01572X/1) and from the European Research Council, ERC (Grant No. 758345). AW acknowledges support from a National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIT) (2018R1C1B6008728). We acknowledge the use of the UCL Grace High Performance Computing Facility (Grace@UCL), the Imperial College Research Computing Service, and associated support services, in the completion of this work. Via membership of the UK’s HEC Materials Chemistry Consortium, which is funded by the EPSRC (EP/L000202, EP/R029431, EP/T022213), this work used the ARCHER UK National Supercomputing Service (www.archer.ac.uk) and the UK Materials and Molecular Modelling (MMM) Hub (Thomas – EP/P020194 & Young – EP/T022213).
© 2021 The Royal Society of Chemistry.