Barium-zirconium-sulfide (BaZrS<sub>3</sub>) based chalcogenide perovskites form an emerging class of promising candidates for photovoltaic applications. They are synthesized from easily available, inexpensive precursor materials, and are more stable and less toxic compared to the conventional hybrid organic-inorganic halide perovskites. Based on the electronic structures, we show transition metal and chalcogenide doping as effective strategies for engineering suitable band gaps in chalcogenide perovskites. Specifically, we study the effects of systematic doping of Ti and Hf for Zr, and O and Se for S in BaZrS<sub>3</sub>. Although the bandgap tuning will furnish improved photo-absorption properties, a smaller bandgap can also favor nonradiative electron-hole recombination, leading to poor photovoltaic performance. We perform detailed, first principles noadiabatic molecular dynamics calculations to unveil the role of various factors affecting the recombination dynamics in them. The bandgap, the magnitude of average nonadiabatic coupling between ground and excited electronic states, and the decoherence effects contribute to the recombination timescales. We illustrate that symmetry (both structural and orbital) and decoherence are critical for improving the photovoltaic properties of chalcogenide perovskites. We also investigate the effects of cation and anion doping on the phonon-induced cooling of hot charge carriers and characterize the vibrational modes associated with them. Our study indicates that tuning both symmetry and decoherence effects may be considered as potential strategies for the rational design of novel perovskite-based photovoltaics.

Criticality of symmetry and decoherence in the photovoltaic properties of chalcogenide perovskites

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.