LAUSR

Abstract A series of novel D-A-π-A organic dyes with different π-spacers for dye-sensitized solar cells (DSSCs) are designed based on hetero-tri-arylamine donor-based dye DP2. The key parameters of all the dyes affecting short-circuit current ( J SC ) and open-circuit voltage ( V OC ) are theoretically investigated in detail using density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to reveal structure-property relationships. The theoretical results indicate that extending π-spacer is beneficial to improve light-absorbing capacities with larger responsive range of spectra and molar extinction coefficients ( e ). The designed dyes DP2-1–DP2-5 exhibit a good balance in various important properties including light harvesting efficiency (LHE), electronic injection driving force ( Δ G inject ), regeneration driving force ( Δ G reg ), reorganization energy ( λ total ) and vertical dipole moment ( μ normal ) and number of photoinjected electrons ( n c ) compared to reference dye DP2. Among all the designed dyes, DP2-3–DP2-5 containing π-spacers with branched chain exhibit obvious red shifted absorption band, smaller regeneration driving force ( Δ G reg ) and larger excited state lifetime ( τ 0 ). This study is expected to provide new clues for the experimental synthesis of highly efficient metal-free organic dyes for DSSCs.