Tuning the Photovoltaic Performance of DSSCs by Appending Various Donor Groups on <i>trans</i>-Dimesityl Porphyrin Backbone

Five cost-effective porphyrin based sensitizers with various donor groups (bisthiophene, <i>N</i>,<i>N</i>-dimethylaminophenyl, triphenylamine, carbazole and phenothiazine) and <i>meso</i>-dimesityl as auxiliary groups have been synthesized through the shortest possible synthetic route for the practical commercialization of these dyes. <i>trans</i>-A₂BC porphyrin dyes show power conversion efficiencies (η) ranging from 5.3% to 7.11% under 1 sun illumination and highly depend on donor strength of appended moiety. Our molecular design incorporates <i>trans</i>-10,20-dimesityl groups, which prevents the π–π aggregation between the porphyrin units onto the TiO₂ surface. The porphyrin dye (<b>RA-200-Zn</b>) bearing phenothiazine as donor unveils the highest photon-to-current conversion efficiency (PCE) of 7.1% and showed butterfly conformation, which can restrict the intermolecular aggregation. Further, this dye shows a broader absorption on TiO₂ surface and significantly increased IPCE values in visible region as compared to the other dyes, which assured better light harvesting ability with high short-circuit current density (<i>J</i>_sc) of 14.2 mA cm<sup>–2