Triphenylamine-Based Metal-Free Organic Dyes as Co-Sensitizers: Enhancing Dye-Sensitized Solar Cell Performance Through Innovative Molecular Design.

A series of novel dye-based D-π-A-type metal-free organic dyes was prepared via the Wittig reaction. Dyes SAS-1-5 containing triphenylamine (TPA) as a strong electron donor was linked with an aryl ring as a π-conjugation spacer, cyanoacetamide, 2-(phenylsulfonyl)acetonitrile, and thiazolidine as the electron acceptors. Herein, we confirmed the chemical structures of the co-sensitized triphenylamine sensitizers using spectral analyses. In addition, their optical properties, electrochemical characteristics, and photovoltaic performances were estimated. Theoretical density functional theory (DFT) at the B3LYP/6-311G(d, p) level was used to elucidate the bridged effect on geometry. The SAS-1-5 sensitizers showed absorption bands in a dimethylformamide (DMF) solution in the range of (450-590 nm) which led to an obvious enhancement in the visible harvesting ability. To improve the efficiency of the DSSCs, SAS-1-5 dyes were co-sensitized with the standard dye N-719. The power conversion efficiencies (PCEs) of SAS-1-5 with N-719 ranged from 7.39 to 9.12%. By employing SAS-2 as a co-sensitizer, the DSSC system achieved an impressive 9.12% efficiency, which was 24% higher than that when using the N-719 ruthenium complex dye. Furthermore, all TPA-based co-sensitizers (SAS-1-5) demonstrated considerable promise for improving photovoltaic performance.