Computational Evaluation of Copper Dimethyl-Bipyridine Based Complex towards Dye Sensitized Solar Cell Performance

The research work based on computational studies of copper dimethyl-bipyridine complexes, a set of computational calculations were computed with orca program using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods for (Cu(bipyridine) ₂ ⁺ & Cu(bipyridine) ₂ ²⁺ ) complexes. The calculation outputs were visualized using Avogadro software and charge decomposition analysis was performed using multwfn software. The results showed that the Highest Occupied Molecular Obital (HOMO) is delocalized over the copper and nitrogen atom on the ligands for Cu(bipyridine) ₂ ⁺ and Cu(bipyridine) ₂ ²⁺ . The Lowest Unoccupied Molecular Orbital (LUMO) is delocalized over the bi-pyridine ligands. Each of the complexes are divided into two fragments: copper ion portion designated as fragment 1 and the dimethyl-bi-pyridine ligand portion designated as fragment 2. The results of intra-fragment analysis shows that all the peaks have hole and electron contributions concentrated on separate fragments for Cu(bipyridine) ₂ ⁺ . While for Cu(bipyridine) ₂ ²⁺ the results shows that peaks 6, 5 & 8 have hole and electron contributions concentrated on separate fragments. The electron excitation analysis revealed that all the first five transitions in Cu(bipyridine) ₂ ⁺ are in the visible region, while Cu(bipyridine) ₂ ²⁺ , the first five transitions are in the infrared region. The calculated LHE value of the Cu(bipyridine) ₂ ⁺ dye at ground state was 0.123, while at the oxidized state (Cu(bipyridine) ₂ ²⁺ ) the LHE was 0.561. Molecular engineering of the complexes towards optimum positioning of its LUMO and HOMO with respect to CB of TiO ₂ and standard potential of the iodide/triiodide redox couple, will enhance its suitability for DSSC application.