Near-Infrared-Absorbing Indolizine-Porphyrin Push–Pull Dye for Dye-Sensitized Solar Cells

Porphyrins are attractive chromophores for application in dye-sensitized solar cells (DSCs), as judicious tuning of donor–acceptor properties can enable excellent near-infrared (NIR) absorption and exceptional device performance. Here, we report a porphyrin-based dye (SM85) conjugated to the planar strong electron donor indolizine, designed to extend absorption further into the NIR region by inducing π–π interactions such as head-to-tail dye aggregation. The optoelectronic consequences of indolizine incorporation in SM85 include raising the ground-state oxidation potential and broadening and red-shifting UV–Vis–NIR absorptions, along with an increased molar absorptivity when compared to the dye SM315. Density functional theory (DFT) and time-dependent DFT (TD–DFT) calculations confirm the push–pull character of SM85, which features an overlap of frontier occupied and unoccupied orbitals. Steady-state spectrophotometric analyses reveal the presence of solution aggregates via absorption and emission spectro...