High performance double perovskites of Cs<sub>2</sub>InAgBr<sub>6</sub> and Cs<sub>2</sub>InAgCl<sub>6</sub> structural electronic optical and thermoelectric properties for next generation photovoltaics.

Abstract

First-principles calculations carried out using the full potential linearized augmented planewave (FPLAPW) method as implemented in the Wien2K code indicate that the ground state volume of Cs₂AgInBr₆ and Cs₂AgInCl₆ is 2400 (a.u)³ and 2050 (a.u)³, which corresponds to a unit cell energy minimum of - 84,842.919545 Ryd and - 59,101.325763 Ryd. The negative formation energy, Goldschmidt tolerance factor closer to unity and octahedral factor greater than 0.41justify their thermodynamic and structural stability of our investigated double perovskites. The reported lattice constant, ground state energy, bulk modulus and its pressure derivative are closer to their available experimental and theoretical data. Optical analysis reveals high absorption in the visible to ultraviolet range, along with enhanced dielectric constants and optical conductivity. Cs₂AgInX₆(X = Cl, Br) double perovskites are promising candidates for solar cells, thermoelectric devices, and energy harvesting applications due to their tunable band gap, high optical absorption, and enhanced thermoelectric performance.