Tuning of band gap by anions (Cl, Br, I) of double perovskites Rb₂AgAsX₆ (Cl, Br, I) for solar cells and thermoelectric applications

The high stability, lead free, environment friendly and excellent performance of double perovskites make them emerging materials for solar cells and thermoelectric generators. Therefore, here optical, electronic, and thermoelectric characteristics of Rb₂AgAsX₆ (X = Cl, Br, I) are studied comprehensively by first principle approach. The thermodynamic stability is ensured through formation energy and structural stability by calculating tolerance factor. The studied DPs band gaps are tuned from 2.21 eV to 1.50 eV, and 0.52 eV by the replacing the anions (Cl to Br, and I). The absorption regions from varies from infrared to visible regions which increase their significance for diverse applications in optoelectronics. The broad absorption band of Rb₂AgAsI₆ in visible region is important for solar cells. Furthermore, the thermoelectric performance has been elaborated by power factor and figure of merit. The ultralow lattice thermal conductivity, and large Seebeck coefficient also increase the figure of merit to realize them for thermoelectric applications.