First principles insight into Cs₂YZnX₆ (X = Br, I) double perovskite materials for optoelectronic and thermoelectric device applications

In this study, we utilize first-principles calculations based on density functional theory (DFT) to examine the structural, electronic, mechanical, optical, and thermoelectric properties of Cs2YZnX6 (X = Br, I) materials, with a focus on their potential applications in solar cells and thermoelectric devices aimed at advancing environmentally-friendly perovskite materials. The structural integrity of Cs2YZnX6 compounds is confirmed through tolerance factor analysis, which validates their stable cubic perovskite structure. Thermodynamic stability is ensured by calculating the formation energies of both compounds. Dynamic stability is confirmed using the phonon dispersion curve. Electronic property analysis shows that both materials exhibit semiconducting behavior, with Cs2YZnBr6 having a band gap of 2.93 eV and Cs2YZnI6 having a band gap of 2.29 eV. The mechanical stability of these compounds is affirmed by the computed elastic constants, further demonstrating their suitability for practical applications. Optical property evaluation reveals that both materials have good optical absorption in the visible and UV regions, making them promising for optoelectronic applications. In addition, the thermoelectric performance of Cs2YZnX6 is assessed, with both materials displaying a maximum Seebeck coefficient of 1.56 x 10-3 V K-1 at room temperature. These findings emphasize the significant potential of Cs2YZnX6 perovskites for integration into optoelectronic and thermoelectric devices, contributing to the advancement of sustainable materials in energy conversion technologies.