Designing Ni substituted double perovskite oxides Ba₂Zn_1-xNi_xWO₆ (x = 0.00, 0.25, 0.50, 0.75, and 1.00) to explore the enhanced optoelectronic and thermoelectric performance using DFT

Double perovskite oxides hold great promise for the production of renewable energy, especially in thermoelectric generators and solar cells. Nevertheless, their usefulness is limited due to their toxicity, instability, and large band gaps. Here, we applied density functional theory (DFT) to look into the effects of Ni substitution on the structural, mechanical, electronic, optical, and thermoelectric properties of double perovskite oxide Ba₂ZnWO₆. According to our findings, raising the Ni concentration from 0 % to 100 % causes the band gap energies to decrease from 2.50 eV to 1.87 eV. This reduction of band gap energies tailored the optical and thermoelectric performance that is, the key parameters like the absorption coefficient peaks (∼10⁴ cm⁻¹) and the figure of merits (0.90 to 0.99 at T = 300 K) increased with increase of Ni content. These fascinating results coupled with structural stability confirmed from Goldschmidt's factors, mechanical stability from Burn-Haun criterion, and thermodynamic stability from negative formation energies opened new avenues for green energy-related applications particularly in terms of solar cells and thermoelectric generators.