A comprehensive computational scrutiny of the optoelectronic, thermodynamic, mechanical and structural attributes of Potassium-based K 3 XI 6 (X = In, Ga) double perovskites for optoelectronic applications

Lead-free perovskite halides have attracted significant attention from the scientific community as these materials are environmentally friendly and possess higher optoelectronic performance; however, their structural analysis still requires systematic investigation. The potential for improved stability and efficiency in optoelectronic applications makes potassium-based halide perovskites noteworthy. Potassium-based halide perovskites offer lower toxicity and are a safer option for environmentally friendly technology. In this work, we have assessed in detail the physical attributes of K 3 XI 6 (X[Formula: see text] [Formula: see text] [Formula: see text]In, Ga). For analyzing the electron-ion exchange correlation effects, the modified Becke–Johnsons (mBJ) is used. To check the stability of these halides, several parameters are computed. The second-order stress–strain energy equations are employed for the computation of elastic constants of K 3 XI 6 (X[Formula: see text] [Formula: see text] [Formula: see text]In, Ga). The mechanical stability is checked via Born’s stability criteria. Sound velocities for K 3 XI 6 (X[Formula: see text] [Formula: see text] [Formula: see text]In, Ga) along three crystallographic planes [100], [110] and [111] are also analyzed. Direct bandgaps of 2.12[Formula: see text]eV and 1.72[Formula: see text]eV are attained for K 3 InI 6 and K 3 GaI 6 as revealed via their electronic properties. Both materials report large optical conductivity and polarization in the visible and UV region and computed bandgaps highlight their applicability for advanced optoelectronic technological applications. Thus, the overall findings demonstrate that K 3 XI 6 (X[Formula: see text] [Formula: see text] [Formula: see text]In, Ga) materials are excellent contenders for low-toxicity and energy-related applications.