Exploring inorganic and nontoxic double perovskites Cs2AgInBr6(1−x)Cl6x from material selection to device design in material genome approach

Abstract

Halide double perovskites have recently been proposed as potential environmentally friendly alternatives to organic group and lead-based hybrid halide perovskites. In particular, Cs2BiAgX6 (X = Cl, Br) have been synthesized and found to exhibit tunable band gaps in the visible range. However, the band gaps of these compounds are indirect, not ideal for applications in thin film photovoltaics. Here in this work we have carried out systematic modeling, using a materials genome approach in the framework of the density functional theory (DFT), to formulate a new system of solar absorption layer based on Cs2InAgX6 and its heterojunction device. Through Cl partial substitution on Br in Cs2InAgBr6 to optimize its thermodynamic stability after the calculation of ATAT proportion searching and Gibbs free energy, we have identified a series of stable cubic-structured phases, with the general formula of Cs2AgInBr6(1−x)Cl6x (0 ≤x ≤ 1). The optimized Cs2InAgBr5Cl compound is a marvelous solar absorption layer to enable harvesting the solar energy, with direct 1.92 eV bandgap and high solar absorption ability, consistent with Cs2InAgBr6 at standard room temperature (298 K). Assembling with anatase as n type TCO and Cs6Ag4In4Br18Cl4 as p type TCO fabricated by introducing Cs-Br defect, the heterojunction is integrated into perovskite solar cells (PSCs) based on the standard n-i-p structure (TiO2-Vo/Cs2InAgBr5Cl/Cs6Ag4In4Br18Cl4), the lattice mismatching and band alignment are evaluated for this well-designed device.