A comprehensive DFT insight on physical features regarding potential applicability of double perovskites K2YCuZ6 (Z = Cl, Br) for energy harvesting applications

The significant absorption in visible as well as ultraviolet region and higher ZT values suggest that K2YCuZ6 (Z=Cl, Br) double perovskites are suitable for solar energy and thermoelectric applications. [Display omitted] •The evaluation of elastic properties confirmed the ductile behavior, anisotropy, and mechanical toughness of K2YCuCl6 and K2YCuBr6 compounds.•Both materials exhibit indirect band gaps of 2.4 and 1.56 eV.•Optical investigations indicate that these materials are capable of absorbing energy within the visible and ultraviolet spectra.•K2YCuCl6 and K2YCuBr6 exhibit greater performance in thermoelectric devices having ZT values of 0.78 and 0.80. Herein, a comprehensive investigation of the structural, mechanical, optoelectronic, and thermoelectric features of K2YCuZ6 (Z = Cl, Br) is presented concerning their potential utilization inphotovoltaic and thermoelectric devices. The observation of formation energy and fitting of the Murnaghan equation of state ensured thermodynamic and structural stability, respectively. The mechanical stability of K2YCuCl6 and K2YCuBr6 is determined by employing Born Huang stability criteria based on their elastic constants. The analysis of elastic parameters further classified these materials as anisotropic as well as ductile. The band gaps of K2YCuCl6 and K2YCuBr6 have been computed using the TB-mBJ potential, resulting in values of 2.4 and 1.56 eV, respectively. An extensive analysis of the optical characteristics of these compounds is carried out in the energy region spanning from 0 to 8 eV. These compounds are discovered to have substantial absorbance and conductive properties in the visible and ultraviolet energy ranges. On the other hand, they exhibit transparency to incoming photons with lower energy levels. Our examination of the optical characteristics indicates that these compounds are very suitable for use in photovoltaic applications. The evaluation of thermoelectric parameters resulted in the p-type semiconducting nature and higher figure of merit of 0.78, and 0.80 at 300 K. Therefore, K2YCuZ6 that has not been verified experimentally has great potential for solar cell and thermoelectric applications, indicating its ability to contribute to the progress of alternative energy sources.