Abstract
The double perovskite materials are exceptional for energy applications due to their non-toxic, efficient, and eco-friendly nature. Here, we comprehensively addressed the electronic, optical, and thermoelectric characteristics of double perovskites Tl2PtX6 (X = Cl, Br, I). The tolerance factor and formation energy, an important criterion for the existence of structural and thermodynamic stability are computed. The strong p-d hybridization between cations (Pt) and anions (Cl, Br, I) tune the band gaps from 2.83 eV, 2.18 eV, and 1.35 eV. The diminution of band gap due to replacement of Cl to I anions shifts the absorption to visible region. For detailed analysis, the optical behavior is explored from 0-5 eV in terms of absorption, optical loss, dielectric constants, and reflection of light from materials under study. Furthermore, thermoelectric behavior has been examined by power factor, Seebeck coefficient, and figure of merit. The high figure of merit and ultralow lattice thermal conductivity increased their significance for thermoelectric applications.