Development of high-efficiency D-π-A dye photosensitizers for dye-sensitized solar cells: Substantial influence of electronic properties

To achieve high efficiency dye-sensitized solar cells (DSSCs), some dye photosensitizers were designed with an architecture of donor-π-acceptor (D-π-A) using CH₃ (Me), OCH₃ (OMe), and N(CH₃)₂ (NMe₂) as electron donor groups while F, Cl, and Br as electron acceptors that were attached to the triphenylamine (TPA)-based dye. The electronic effects of substituents were scrutinized on the electronic, optical, charge transfer, stability, and photovoltaic features of dyes used in DSSC devices by density functional theory (DFT) and time-dependent DFT (D-DFT) computations. To systematically determine the best computational method, six different functionals and two basis sets were examined, confirming the M06-D3/6-31G(d,p) computational method afforded the most favorable results. The UV-Vis absorption spectra revealed ${\lambda }_{max}^{abs}$ values within the UV-visible and near-infrared regions, confirming these materials would be exceptional light-responsive photosensitizers for DSSCs. Negative ΔG_injection values of all molecules approved their spontaneous electron injection toward the TiO₂ semiconductor in photoanode. Higher photovoltaic parameters were achieved upon attachment of Me and OMe, NMe₂ substituents on the TPA-H dye. Lastly, the rationally developed molecules could be applied as next-generation dyes in fabrication of high efficiency DSSC photovoltaics, particularly the TPA-NMe₂,Br with the most preferred optoelectronic and photovoltaic properties was chosen as the most ideal dye photosensitizer for DSSCs.