Exploring the physical properties of Ae₂TlCoF₆ (Ae = Rb, Cs) double perovskites for solar cell applications by first-principles calculations

In this study, we have determined the structural, electronic, optical, mechanical, and thermoelectric properties of Ae₂TlCoF₆ (Ae = Rb, Cs) double perovskite materials using the density functional theory (DFT). The phonon dispersion curves and formation energy shows that both the materials are dynamically stable and experimentally can be synthesized. The electronic band structure exhibits the semiconductor nature of both materials with direct energy band gap values of 1.35 eV and 1.64 eV for Rb₂TlCoF₆ and Cs₂TlCoF₆, respectively. The calculated optical properties of both studied materials exhibit remarkable properties such as high absorption coefficients, low reflectivity, and minimum energy loss function. The calculation of thermoelectric properties shows that Cs₂TlCoF₆ is a potential thermoelectric material with an improved electronic figure of merit of 0.14 at 800 K, which increases with temperature to a value of 0.25 at 1000 K. We have also investigated the efficiency of our perovskite materials by using the spectroscopic limited maximum efficiency (SLME). The computed results strongly suggest that Ae₂TlCoF₆ (Ae = Rb, Cs) compounds hold great promise as potential candidates for solar cell applications.