Optimization of porphyrin dyes with a bulky triphenylamine donor for developing efficient dye-sensitized solar cells

To fabricate efficient dye-sensitized solar cells (DSSCs), three porphyrin dyes XW65-XW67 have been designed and synthesized using a bulky triphenylamine donor. Based on our previously reported dyes with a carbazole donor, a bulky triphenylamine unit was employed as the donor to synthesize XW65 with the aim to enhance the electron donating ability and suppress dye aggregation. As a result, XW65 shows enhanced photocurrent density (J(sc)) and open circuit voltage (V-oc ), affording a high efficiency of 9.02%. On this basis, XW66 was synthesized with a methyl group introduced into the carboxyphenyl acceptor to further suppress dye aggregation and improve the V-oc, achieving an enhanced efficiency of 9.23% with improved V-oc of 849 mV and J(sc) of 14.87 mA cm(-2), which can be ascribed to the further suppressed dye aggregation and enhanced adsorption amount on the TiO2 film induced by the additional methyl group. To further improve the J(sc), a benzothiadiazole (BTD) unit has been introduced as the auxiliary acceptor to afford XW67, which exhibits a strikingly red-shifted monochromatic photon-to-electron conversion efficiency (IPCE) onset wavelength of 830 nm, obtaining the highest J(sc) value of 15.83 mA cm(-2) among the three dyes. Consequently, despite the sacrifice of V-oc caused by the severe dye aggregation associated the extended conjugation framework, XW67 exhibits the highest efficiency of 9.43%. On this basis, cosensitization with WS-5 afforded elevated efficiencies of 10.07%, 10.38% and 10.13% for XW65-XW67, respectively, owing to the simultaneously enhanced J(sc) and V-oc. These results indicate that it is effective to develop efficient DSSCs based on cosensitization of optimized porphyrin dyes containing a bulky triphenylamine donor, a methyl group on the carboxyphenyl acceptor, and an auxiliary electron acceptor.

Automated summary

Three porphyrin dyes were designed and synthesized to fabricate efficient DSSCs, showing enhanced efficiency through optimized donor and acceptor structures, improved electron donating ability, and suppressed dye aggregation. Cosensitization with WS-5 further elevated the efficiencies of the dyes.