Optimizing thermoelectric performance of halide perovskite Ca3AsBr3 through strain engineering

Abstract

We investigate structural, dynamical, elastic, electronic, and thermoelectric properties of cubic perovskite halide Ca₃AsBr₃ under the effect of strain using first-principles calculations. It is found to have a direct bandgap of 2.425 eV that further reduces under compressive strain making it an ideal candidate for thermoelectric application. The material satisfies various stability criteria, e.g., dynamical, thermodynamical, and mechanical. The transport calculations show the highest Seebeck coefficient of value -458.227 μVK⁻¹ at 700 K for n-type Ca₃AsBr₃ unstrained structure at carrier concentration 1 × 10²¹ cm⁻³, which is further enhanced to -482.366 μVK⁻¹ for -2 % strain. The lattice thermal conductivity of the material is reduced from 1.243 Wm^-1K^-1 to 0.627 Wm^-1K^-1 at 700 K under 3 % strain. This low thermal conductivity, coupled with positive power factor values, results in increased peak thermoelectric figure of merit from 0.36 (unstrained) to 0.56 (+3 % strain) at 700 K for an n-type doping concentration of 1 × 10²⁰ cm⁻³.