Umbrella-Shaped -Terphenyls for Highly π-Extended Planar Dyes toward High-Performance Dye-Sensitized Solar Cells.

Porphyrin dyes with π-extended structures, particularly those with aromatic fused designs, have garnered considerable attention as efficient sensitizers for dye-sensitized solar cells (DCCSs). However, their photovoltaic performance has often been limited due to high aggregation tendencies caused by strong π-π interactions and charge recombination processes. Since -terphenyls can be used as effective sterically protecting groups, the incorporation of umbrella-shaped -terphenyls on the top of porphyrin dyes could provide an effective approach to unlock the full potential of highly π-extended porphyrin dyes. In this study, we report new fused porphyrin dyes, , , , and , introducing -terphenyl groups. This innovative design ensures both blocking effects on dye aggregation on TiO and charge recombination against redox shuttles. Under the optimized conditions, DSSCs using thiophene-fused porphyrins and achieved a remarkable power conversion efficiency (PCE) of 11.5%. This is high compared to those with reference porphyrins, possessing steric hindrance due to the orthogonal orientation of a V-shaped diarylamino group to the porphyrin plane and without the bulky umbrella-shaped -terphenyl, demonstrating the proof of our concept. More importantly, the cosensitized DSSC using and the complementary dye afforded the highest PCE of 12.3% ever reported for DSSCs with fused porphyrin dyes. This demonstrates that the "umbrella-shaped -terphenyl" design is an attractive methodology for enhancing the photovoltaic performance of DSSCs with highly π-extended planar dyes, especially fused porphyrin dyes.