First principles investigation of bandgap modulation and light matter interaction in cubic X₂ScInI₆ halide double perovskites for emerging energy applications

Abstract

Double perovskites as promising substitutes to address energy deficiencies, potentially serving as sustainable materials for energy production. The ongoing investigations into these compounds are essential for the advancement of optoelectronic devices. In this work, we conducted an inclusive examination of the properties of X₂ScInI₆ (A = K, Rb) double perovskite halides utilizing DFT calculations with the all-electron FP-LAPW+lo technique, particularly focusing on replenish able energy sensors. Our findings demonstrate that the energy of formation and Goldsmith's tolerance factor calculations suggest that these halides retain structural and thermodynamic stability in the cubic phase. The stability was further validated by Phonon Dispersion Spectra through the linear response method using the Material Studio code. An evaluation of the elastic properties indicated that the Pugh’s (B/G) and Poisson ratios suggest a ductile nature. We also computed band-gaps in cooperation with TB-mBJ, along with and without spin-orbit coupling (SOC). The bandgap metrics for K₂ScInI₆ (E_g = 1.965 eV and 1.911 eV) and Rb₂ScInI₆ (E_g = 1.993 eV and 1.940 eV) were derived using Trans and Blaha modified Becke-Johnson (TB-mBJ & TB-mBJ+SOC) potentials. Additionally, we investigated the optical properties of these halides, focusing on their complex dielectric functions. Our results suggest that these X₂ScInI₆ (X = K, Rb) halides DPs can be effectively utilized in optoelectronic equipment due to their capacity to absorb light in the UV spectrum. We anticipate that our findings will aid future experimental studies on X₂ScInI₆ (X = K, Rb) for energy-efficient applications.