Theoretical design of homoleptic Cu(I) complexes with triazine-type ligands and their effect on dye-sensitized solar cells

Abstract

Twelve homoleptic Cu(I) complexes with triazine-type ligands were designed and analyzed theoretically for their possible application in dye-sensitized solar cells (DSSC). This research analyzed the effect of π-conjugation and substitution of different anchoring groups in the triazine ligands. The molecular structures of the compounds were obtained through density functional theory (DFT). A relationship between complex geometry distortion (τ₄) and optoelectronic properties was found. UV–Vis absorption spectra and electronic transitions were studied using time dependent-density functional theory (TD-DFT). The complexes presented absorption bands in the 300–655 nm range, attributed to metal → ligand and ligand-to-ligand transfer. Energy levels of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) meet the requirements to consider molecular proposals as sensitizers. Chemical reactivity parameters of interest were obtained and analyzed, such as chemical hardness (η), electron-donating power (ω⁻), electron-accepting power (ω⁺), and electrophilicity index (ω). For all Cu(I) complexes, a relation was found between chemical hardness and τ₄ values. The free energy electron injection (ΔG_Inject) and light harvesting efficiency (LHE) were determined and discussed. All previous studies indicate that all complexes present interesting properties like dyes in DSSC applications.