Dye-sensitized solar cells based on zinc(II) phthalocyanines bearing 3-pyridin-3-ylpropoxy anchoring groups

In this study, nonperipherally tetra-substituted (2), peripherally tetra-substituted (3), and peripherally octa-substituted (4) zinc(II) phthalocyanines were synthesized as sensitizers for dye-sensitized solar cells (DSSCs) in which 3-pyridin-3-ylpropoxy substituent acts as anchoring unit to bind TiO2 surface. The optical results indicated that there is an interaction between the dyes and the TiO2 surface. The photovoltaic performances of the DSSCs based on these dyes were found to depend on both the position and number of the substituents. Despite the more red-shifted absorption, the DSSC based on 2 showed the conversion efficiency of 0.68%, which is lower than 1.36% and 0.92% for 3 and 4, respectively, under one sun (AM 1.5G). The vertical orientation of the dye on TiO2 surface could be the main reason for the higher photovoltaic performance of complex 3, which is beneficial for not only injecting the electrons into the conduction band of TiO2 but also reducing the charge recombination. Overall, these results demonstrate that the peripherally tetra-substituted 3-pyridin-3-ylpropoxy zinc(II) phthalocyanine complex (3) as a sensitizer can more efficiently utilize the photons in the red/near-infrared region with respect to the other complexes studied.