%0 Journal Article
%T Near-Infrared-Absorbing Indolizine-Porphyrin Push每Pull Dye for Dye-Sensitized Solar Cells
%J -
%D 2019
%R https://doi.org/10.1021/acsami.8b21414
%X Porphyrins are attractive chromophores for application in dye-sensitized solar cells (DSCs), as judicious tuning of donor每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 羽每羽 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 ultraviolet每visible每NIR absorptions, along with increased molar absorptivity when compared to the dye SM315. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations confirm the push每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 spectroscopies. Aggregate modes were probed by DFT and TD-DFT analyses, and plausible models are presented. SM85-based DSC devices demonstrate a 5.7% power conversion efficiency (PCE) at full sun (7.4% PCE at 10% sun) with an exceptional improvement to the incident photon-to-current conversion onset at ‵850 nm. Current dynamics measurements, time-correlated single photon counting, and computational analyses are used to better understand device performances. This study puts forward a novel intramolecular charge-transfer porphyrin system with a dramatic shift into the NIR region, as is needed for nonprecious metal-based sensitizers, and provides an example of controlled, donor每acceptor-mediated aggregation as a complementary strategy to traditional donor每acceptor modifications to single-molecule 羽-systems in accessing enhancements in long wavelength light harvesting in molecular-based optoelectronic devices
%U https://pubs.acs.org/doi/10.1021/acsami.8b21414