Triarylamine-Substituted Imidazole- and Quinoxaline-Fused PushPull Porphyrins for Dye-Sensitized Solar Cells

We have prepared a pushpull porphyrin with an electron-donating triarylamino group at the ,-edge through a fused imidazole group and an electron-withdrawing carboxyquinoxalino anchoring group at the opposite ,-edge (ZnPQI) and evaluated the effects of the pushpull structure of ZnPQI on optical, electrochemical, and photovoltaic properties. ZnPQI showed red-shifted Soret and Q bands relative to a reference porphyrin with only an electron-withdrawing group (ZnPQ), thus demonstrating the improved light-harvesting property of ZnPQI. The optical HOMOLUMO gap was consistent with that estimated by DFT calculations. The ZnPQI-sensitized solar cell exhibited a relatively high power conversion efficiency () of 6.8%, which is larger than that of the ZnPQ-sensitized solar cell (=6.3%) under optimized conditions. The short-circuit current and fill factor of the ZnPQI-sensitized solar cell are larger than those of the ZnPQ-sensitized solar cell, whereas the open circuit potential of the ZnPQI-sensitized cell is smaller than that of the ZnPQ-sensitized cell, leading to an overall improved cell performance of ZnPQI. Such fundamental information provides a new tool for the rational molecular design of highly efficient dye-sensitized solar cells based on pushpull porphyrins.