First-principles investigation on optoelectronic, mechanical and thermoelectric properties of CaZrO <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"> <mml:msub> <mml:mspace width="0.1em"/> <mml:mrow> <mml:mn>3</mml:mn> <mml:m

In this work, we investigate the optoelectronic, mechanical and thermoelectric properties of CaZrO 3 − x Se x ( x = 0 , 1 , 2 , 3 ) perovskites using first-principles calculations based on density functional theory as implemented in the WIEN2k code. The compounds undergo a phase transition with increasing selenium content: from cubic in CaZrO 3 , to tetragonal in CaZrO 2 Se and CaZrOSe 2 , and back to cubic in CaZrSe 3 . This transition reflects the impact of selenium substitution on crystal symmetry. The calculated Goldschmidt’s tolerance factor within the ideal range and the negative formation energy confirm that the investigated materials are structurally and thermodynamically stable. Electronic structure analysis indicates semiconducting behavior, with a considerable reduction in the bandgap from 3.44 eV to 0.23 eV as selenium number increases from 0 to 3 , enhancing electronic conductivity. Elastic constants reveal that these materials satisfy Born’s mechanical stability criteria and exhibits ductile nature. Optical studies demonstrate strong light absorption in the visible and ultraviolet regions, along with high optical conductivity and low reflectivity, suggesting their capability in optoelectronics such as photovoltaics and light-emitting devices, due to their efficient light interaction and favorable electronic behavior. Additionally, the obtained thermoelectric properties of CaZrO 3 − x Se x ( x = 0 , 1 , 2 , 3 ) perovskites indicate that these materials are suitable for energy harvesting devices. • DFT study is performed on CaZrO3-xSex (x = 0, 1, 2, 3) mixed-anion perovskites. • Studied compounds maintain structural integrity with stable tolerance factors and thermodynamic viability. • Se substitution narrows the bandgap from 3.44 eV to 0.23 eV, enhancing visible absorption. • A substantial enhancement in visible light absorption is achieved via Se substitution. • Electronic and lattice thermal conductivities display contrasting trends with Se content.