A DFT-based insight into the mechanical, structural, thermoelectric and optoelectronic attributes of Cs₂YCuX₆ (X=Br, I) double perovskites for green energies

Abstract Halide perovskite structures have bandgap tunability and are environmentally neutral, making them useful for future studies. In this current manuscript, we have theoretically investigated the physical traits of Cs2YCuX6 (X=Br, I) using the FP-LAPW technique embedded in Wien2K simulations. Both compounds exhibits thermodynamically, dynamic and structural stability confirmed through formation energies, phonon and volume optimization curves. Isotropic nature is reveled for Cs2YCuBr6, while anisotropic behavior is observed for Cs2YCuI6. The mechanical properties further disclose that these materials are ductile. For Cs2YCuBr6 and Cs2YCuI6, the electronic characteristics reveal indirect band gaps of 2.37 eV and 2.16 eV, respectively. The addition SOC effect leads to a small impact on the electronic structure of these halides. The ultraviolet area is where materials absorb most light, indicating their potential for use in UV-based optoelectronic devices. The examined transport characteristics depict the high ZT values of 0.75 and 0.77 for Cs2YCuBr6 and Cs2YCuI6, respectively. This study emphasizes the potential of Cs₂YCuX₆ (X=Br, I) for high-performance ultraviolet optoelectronic devices and thermoelectric applications, rendering them interesting options for renewable energy technology.