Novel zinc porphyrin with phenylenevinylene meso-substituents: Synthesis and application in dye-sensitized solar cells

A novel zinc porphyrin, P, with phenylenevinylene segments at two opposite meso-positions and carboxyphenyl at the other two meso-positions of the porphyrin ring, was synthesized and characterized. The phenylenevinylene substituents were terminated with electron-accepting 4-nitro-alpha-cyanostilbene units. Elongation of the pi-conjugation enhanced the solubility of P as well as broadened and strengthened the absorption spectrum. We have investigated the application of P in quasi solid state dye-sensitized solar cells (DSSCs). Under illumination intensity of 100 mW cm(-2), a power conversion efficiency of 2.90% was obtained for the DSSC based on P as sensitizer, which was significantly improved to 4.22% upon addition of deoxycholic acid (DCA) into the P solution for TiO2 sensitization. Coadsorption of DCA decreased the dye adsorption, but significantly improved both short circuit current (J(SC)) and open circuit voltage (V-OC). The breakup of Tr stacked aggregates might improve the electron injection yield and thus J(SC). The electrochemical impedance data indicate that the electron lifetime was improved by the coadsorption of DCA, which was attributed to the improvement in both V-OC and J(SC). The increase in J(SC) has also been attributed to the reduction of the back reaction i.e., the recombination of electrons with tri-iodide ions. (C) 2011 Elsevier B.V. All rights reserved.