Evaluation of stable direct bandgap inorganic double halide perovskites A2MM'X6 for photovoltaic and photocatalysis applications

Abstract

This study employed density functional theory (DFT) calculations to investigate the structural, mechanical and optoelectronic properties of the double halide perovskites, A₂MM'X₆ (A = K, Rb, Cs; M = Ag, Cu; M' = Al, Ga, In; and X = Cl, Br). The stability of twenty-six A₂MM'X₆ was evaluated using the tolerance factor. We then performed a DFT study on the seventeen phase stable materials to predict their thermodynamic stability, mechanical and electronic properties. The phonon dispersion, decomposition energy and effective masses of the materials are computed. The bandgaps of these materials range from 1.35 to 3.66 eV. The band edge positions and optical properties (absorption coefficient, dielectric function, refractive index, reflectivity and loss function) were calculated. Two of these materials are suitable for single junction solar cells applications, three are suitable for tandem solar cells and nine of them materials may act as photocatalysts for water splitting and CO₂ reduction based on their electronic and optical results. Cs₂AgAlBr₆ and Cs₂AgInBr₆ materials are the most stable and appropriate for the application in both photovoltaic and photocatalysis applications.