Lead-free silver-indium based halide double perovskites for energy harvesting applications

Abstract

Herein, density functional theory (DFT) is utilized to analyze physical characteristics of two novel halide double perovskites (HDPs) Na2AgInBr6 and K2AgInBr6. Exchange and correlation energies were estimated via employing generalized gradient approximation (GGA) along with modified Becke-Johnson (mBJ) potential. Geometry optimization predicted nonmagnetic ground state for both HDPs with cubic structure having Fm3m space group. Computed formation enthalpies (ΔHf) and tolerance factors (τG) revealed the thermodynamically stability of both compounds in cubic phase. Na2AgInBr6 is regarded as brittle while K2AgInBr6 is ductile in nature. Na2AgInBr6 exhibited a band gap (Eg) of 1.39 eV while K2AgInBr6 has a Eg of 1.41 eV. Density of states analysis reveals that 4d of Ag- and 4p of Br states are majorly contributing in the higher valence band while In-5s and 4p of Br states are present in lower conduction band and all these states define the semiconductive nature of these systems. Both HDPs are optically active in visible light region suggesting the suitability for solar cell applications. Thermoelectric efficiency is also computed in terms of figure of merit (ZT(e)) whose values for both compounds are 0.7. Based on these outcomes, both HDPs can be considered as highly suitable candidates for energy harvesting applications.