Strain effects on optoelectronic and thermoelectric properties of double perovskite Cs2SnPbI6 for photovoltaic applications: DFT study

Abstract

This paper explores the potential of Cs₂SnPbI₆, a mixed double perovskite, as a promising material for photovoltaic applications. Using density functional theory (DFT), we investigated its crystal structure, optoelectronic properties, and performance under triaxial strain, revealing its tunable direct bandgap. We found that a $6\%$ tensile strain increases the bandgap from $0.97eV$ to $1.444eV$, improving its suitability for solar energy conversion. Under the same strain, the material exhibits a high refractive index of $3.13$ and a strong absorption coefficient of $5.45\times {10}^5{cm}^{-1}$, emphasizing its effective light absorption capabilities. Furthermore, analysis of thermoelectric properties indicates a positive Seebeck coefficient, confirming its P-type nature, as well as an electronic figure of merit exceeding $0.7$ at elevated temperatures with $+6\%$ strain. These findings position Cs₂SnPbI₆ as a promising material for the next-generation photovoltaic and optoelectronic devices, contributing to the advancement of more stable and sustainable solar energy technologies.