Property tuning in unsymmetrical alkoxy zinc phthalocyanines by introduction of perfluoro-tert-butoxy end groups

•Synthesis of two octasubstituted AAAAAABB zinc phthalocyanines analogs.•Alkoxy groups (A) and COOH anchoring groups (B) attached in peripheral positions.•A ends with a OC(CF3)3 group in one case, with OC(CH3)3 in the other.•Light absorption properties are similar and both dyes can act as sensitizers in dye-sensitized solar cells.•Power conversion efficiency of the cell is increased by a factor of 2.6 when the fluorous dye is used.

Two peripherally octasubstituted zinc phthalocyanines (ZnPcs) bearing six alkoxy residues and two adjacent carboxylic acid anchoring groups were synthesized in order to assess the benefits deriving from the insertion of fluorocarbon domains at the periphery of ZnPc photosensitizers to be used in dye-sensitized solar cells (DSSCs). To this end the alkoxy substituents were terminated with tert-butoxy groups in one case and with perfluoro-tert-butoxy groups in the other. The two ZnPc analogs showed similar light absorption properties and both dyes were able to inject electrons into the conduction band of TiO2 upon photoexcitation. Interestingly, DSSCs based on the fluorous dye exhibited power conversion efficiency almost three times as high as that of its hydrocarbon analog (0.89% vs 0.34%), thus showing that the performance of devices based on ZnPcs can be significantly improved by coating the dye with an outer fluorous layer.

Graphical abstractThe performance of devices based on ZnPcs can be significantly improved by coating the dye with an outer fluorous layerFigure optionsDownload full-size imageDownload as PowerPoint slide