Pyrazole-3-carboxylic acid as a new anchoring group for phthalocyanine-sensitized solar cells

Abstract

We have designed and synthesized an unsymmetrical zinc phthalocyanine (PCA-ZnPc-1) bearing an electron-withdrawing pyrazole-3-carboxylic acid anchoring group and three electron-donating tert-butyl groups as a sensitizer for dye-sensitized solar cells (DSSCs). PCA-ZnPc-1 sensitized solar cell showed a modest power conversion efficiency (1.74%), which may suffer from the flexible and non-conjugated oxygen linker on the sensitizer. However, the obtained efficiency is found to be three to four times higher than that of the unsymmetrical ones bearing only carboxylic acid due to the combination of pyrazole and carboxylic acid moieties within the same anchoring group, which enhances the binding of the dye on the TiO2 surface and results in an increase of electron injection efficiency. Therefore, the pyrazole-3-carboxylic acid is a promising anchoring group for developing new phthalocyanines to build efficient DSSCs.