Computational study of the fundamental properties of Zr-based chalcogenide perovskites for optoelectronics

Chalcogenide perovskites have recently attracted enormous attention since they show promising optoelectronic properties and high stability for photovoltaic applications. Herein, the relative stability and photoactive properties of chalcogenide perovskites AZrX(3) (A = Ca, Sr, Ba; X = S, Se) including the needle-like (alpha phase) and distorted perovskite (beta phase) structures are first revealed. The results show that the difference in the relative stability is large between the alpha and beta phases for both AZrS(3) and AZrSe(3). The fundamental direct-gap transition is only allowed for the beta phase, which is further confirmed by its optical properties. It is indicated that the suitable direct-gap energy of the alpha phase is not desirable for thin-film solar cells. Therefore, the stability, and mechanical, electronic, and optical properties of the distorted chalcogenide perovskites AZrS(3-x)Se(x) (x = 0, 1, 2, 3) are mainly explored for the first time. The predicted direct band gaps of nine compounds AZrS(3-x)Se(x) (x = 1-3) are in the ideal range of 1.3-1.7 eV. Most compounds have small effective masses, low exciton binding energies, and high optical absorption coefficients in the visible region. Moreover, the mechanical, thermodynamic, and dynamic stabilities are identified for these compounds. Our findings suggest that CaZrSe3, SrZrSe3, and BaZrSe3 are proposed to be the most promising candidates for photovoltaic applications owing to their promising properties.

Automated summary

This study investigates the relative stability and photoactive properties of chalcogenide perovskites AZrX(3) (A = Ca, Sr, Ba; X = S, Se) and reveals the difference in stability between the alpha and beta phases. Only the beta phase exhibits the fundamental direct gap transition, which is confirmed by its optical properties. Moreover, the distorted chalcogenide perovskites AZrS(3-x)Se(x) (x = 0, 1, 2, 3) are found to have suitable direct band gaps and high optical absorption coefficients. CaZrSe3, SrZrSe3, and BaZrSe3 are proposed as the most promising candidates for photovoltaic applications.