Sublattice mixing in Cs₂AgInCl₆ for enhanced optical properties: High-throughput screening from first-principles

A stable and non-toxic double perovskite (Cs₂AgInCl₆) has been reported as an alternative to lead halide perovskites APbX₃ (A = CH₃NH₃⁺, HC(NH₂)₂⁺, Cs⁺, and X = Cl⁻, Br⁻, I⁻) in the field of optoelectronics. However, due to the wide bandgap (3.3 eV), it doesn’t show an optical response in the visible region. Therefore, we report here the tuning of its bandgap via sublattice mixing (partial substitution of several metals M(I), M(II), M(III) at Ag and/or In sites) and enhancing its optical properties. Here we have employed high-throughput screening using a hierarchical first-principles based approach starting from density functional theory (DFT) with appropriate exchange-correlation functionals to beyond DFT methods under the framework of many-body perturbation theory (viz. G₀W₀@HSE06). Our results reveal that substitution of Co²⁺, Ni²⁺, and Cu²⁺ is thermodynamically unstable and these can decompose into ternary compounds. We have also inferred that the sublattices with Cu⁺ and Au⁺ at Ag site, Ir³⁺ at In site, Zn²⁺ and Mn²⁺ at Ag and In site simultaneously, as the most promising candidates for various optoelectronic devices under visible light.