First principle study of the structural and optoelectronic properties of direct bandgap double perovskite Cs2AgInCl6

Abstract

Solar cells incorporating double perovskites as absorber layer are currently showing very remarkable progress as a potential environment friendly substitute for lead based hybrid halide perovskites. In the present work we tried to investigate the structural and opto-electronic properties of lead (Pb) free halide double perovskite Cs2AgInCl6. Density Functional Theory (DFT) is employed to systematically analyze the material. For the electron core exchange correlation interaction, the Perdew-Burke- Ernzerhof functional (PBE) within generalized gradient approximation (GGA) was used. The interactions were also analyzed using Local Density Approximation (LDA) method and Perdew Burke Ernzerhof parameterization of the generalized gradient approximation for solid (PBE-sol). The optimized lattice parameters are obtained as 10.565 Å for the material in face-centered cubic structure (Fm-3 m space group). The optimized density is found to be 3.93 gcm−3. The first-principles calculations have given the energy gaps values as 1.1 eV. This energy is slightly lower as an energy underestimation is expected in DFT based calculations. A remarkable factor to mention is the direct bandgap exhibited by the material at Γ(π/a, π/a, π/a), unlike other double perovskites. It is clear from optical studies that the compound is a good absorber in visible region. The optical properties of Cs2AgInCl6 are comparable to hybrid halide perovskites MAPbI3 and halide double perovskites (like Cs2AgBiCl6). Through proper composition grading this material can be envisaged as a possible absorber layer in solar cells.