Tuning D- π-A Dyes for Peak Performance: A Two-Step Strategy via π-Bridge and Electron Donor Optimization

This study investigates the effects of promising electron donors and modified π-bridge structures in organic dyes on the photoelectronic properties and charge transfer dynamics of solar cells. Using density functional theory (DFT) and time-dependent DFT (TD-DFT), the geometric, electronic structures and optical properties were systematically investigated via a two-step design strategy: initial optimization by π-bridge modification, followed by further refinement through precise electron-donor regulation. Additionally, quantum dynamics simulations were employed to clarify how these two strategies influence charge transfer at the dye/TiO ₂ interface. The calculation results indicate that, compared with B1 (Y123) dye, the addition of a planar-conjugated thiophene to modify the π-bridge effectively broadens the spectral absorption range and enhances the donor-acceptor coupling and charge injection at the dye/TiO ₂ interface. The highly symmetrical heteroaromatic groups, with the excellent electron-donating properties, synergistically improve the electron transport performance of the dye through conjugation effects with the thiophene π-bridge. Overall, these findings significantly deepen our understanding of the effects of structural modifications in organic dyes and provide valuable insights for designing efficient dye sensitizers.