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

Abstract

Five cost-effective porphyrin based sensitizers with various donor groups (bisthiophene, N,N-dimethylaminophenyl, triphenylamine, carbazole and phenothiazine) and meso-dimesityl as auxiliary groups have been synthesized through the shortest possible synthetic route for the practical commercialization of these dyes. trans-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 trans-10,20-dimesityl groups, which prevents the π–π aggregation between the porphyrin units onto the TiO2 surface. The porphyrin dye (RA-200-Zn) 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 (Jsc) of 14.2 mA cm–2.