Novel D-pi-A structured porphyrin dyes with diphenylamine derived electron-donating substituents for highly efficient dye-sensitized solar cells

A series of push-pull structured (D-pi-A) porphyrin dyes with an electron-donating group (EDG) attached at the meso-position (HP, EHOP and HOP) were designed and synthesized for use as sensitizers in dye-sensitized solar cells (DSSCs). The nature of the EDG exerts a significant influence on the spectral, electrochemical and photovoltaic properties of these sensitizers. The absorption bands of these porphyrin dyes are broadened and red-shifted upon introduction of alkoxy chains to the electron-donating groups at the meso-position opposite to the anchoring cyanoacrylic acid group. Electrochemical studies showed that the first oxidation occurred at a potential greater than that of the I-/I-3(-) redox couple. Attachment of alkoxy chains to the electron-donating group at the meso-position in the porphyrin sensitizer could prevent electron recombination and induce easy electron injection, resulting in enhanced efficiency of the DSSC. Among the sensitizers, the highest performance of the DSSC fabricated with HOP and PTZ1 as the co-absorbent was 7.6%, which was higher than that of the DSSC with HOP only by a factor of 2.9.