Theoretical investigation of self-assembled donor–acceptor phthalocyanine complexes and their application in dye-sensitized solar cells

• A theoretical investigation of ZnPca, ZnPcb and ZnPcc has been conducted.
• The photovoltaic performances of the self-assembled complexes were investigated.
• The n-butyoxyl groups bring significant influence on the properties of the complexes.
• The theoretical research and the experiment prove the directional charge transfer.

A theoretical investigation of self-assembled donor–acceptor dyads (ZnPca, ZnPcb and ZnPcc) formed by axial coordination of zinc phthalocyanines appended with 4-carboxyl pyridine has been conducted with the density functional theory (DFT) method and time-dependent DFT (TD-DFT) calculations. A comparison between the molecular structures, atomic charges, molecular orbitals, UV–vis spectra and infrared (IR) spectra has been studied. Further, as sensitizers for the TiO2-based dye-sensitized solar cells, the photovoltaic performances have been investigated. The ZnPcc-sensitized solar cell exhibits a higher conversion efficiency than the ZnPcb and ZnPca-sensitized ones under AM 1.5 G solar irradiation, while the ZnPca-sensitized cell performs the poorest due to the lack of peripheral substituents (n-butyoxyl groups) which can be confirmed by the result of the theoretical research. It shows that the directionality of charge transfer in the self-assembled donor–acceptor dyads is important and benefit for the efficiency of the DSSC.

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