From recent research findings, double halide perovskite compounds have sparked a lot of interest in theoretical research due to their great potential for harvesting and generating energy from multiple sources at a higher power conversion rate. Here, theoretical calculations on the fundamental properties of Cs \(_2\) ScInX \(_6\) (X=Cl, Br, I) are performed using the density functional theory for green energy harvesting applications. The obtained lattice parameters and band gap values are well-agreed with the other’s theoretical predicted results. The resultant band gap 2.75, 2.36 and 1.94 eV (GGA) and 3.17, 1.42 and 2.35 eV (GGA+U) for Cs \(_2\) ScInX \(_6\) (X=Cl, Br, I) respectively) which are within the Vis-UV region with an absorption coefficient \(\alpha\) >10 \(^5\) cm \(^{-1}\) suggested that these materials are highly promising for the development of future optoelectronic devices. For better accuracy, we performed the Hubbard correction in which our findings suggests optimized absorption properties with minimum threshold absorption showcasing a slight blue Shift, which enhances efficiency and stability in various optoelectronic and thermoelectric applications. It also shows improved thermoelectric efficiency with high figure of merit values of 0.96 (GGA), 1.82 (GGA+U) and 1.62 (GGA+U) for X=Cl, Br, I respectively.
