Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
DOI: https://doi.org/10.29363/nanoge.hopv.2022.014
Publication date: 20th April 2022
The outstanding opto-electronic properties of metal-halide perovskites (MHPs) have contributed several breakthroughs in photovoltaics and optoelectronics. These materials would be ideally exploited also in heterogeneous photocatalysis, but the poor MHPs stability in aqueous environment has for long inhibited their application to this field. In the last two years, however, a growing family of water-stable and photoactive MHPs have been reported, thus paving the way towards the development MHP-based photocatalysts. Surprisingly, tin-halide perovskites (THPs), which are notoriously unstable in photovoltaics, have received a large attention because of their suitable band gap, tunable electronic energy levels, and their low toxicity coupled to a superior stability in water environment compared to their lead counterparts. Here, we present high-level ab initio calculations to unveil the key factors determining the reactivity of THPs towards photocatalytic hydrogen production at the perovskite/water interface. Our results highlight that the occurrence of electron polarons at the surface of THPs is paramount in determining the efficiency of the reaction. The stabilization of localized electrons stems from the energy of the conduction band edge and from the peculiar THP defect chemistry, largely centered on tin. Band edge tuning is governed by the interplay between the A-site cation and nature of the halogen, thus fine-tuning the THPs energy levels can be achieved by varying the chemical composition, providing a successful strategy to boost the photo-reactivity of these materials.