Effect of direct linkage of pyrazole carboxylic acid acceptor/anchoring group on the photovoltaic performance for phthalocyanine-sensitized solar cells

An unsymmetrical zinc phthalocyanine dye (PCA-ZnPc-4) containing six electron donating hexylsulfanyl groups and a pyrazole-3-carboxylic acid anchoring group which is directly linked to the macrocycle was synthesized to evaluate the photophysical, electrochemical, and theoretical characteristics as well as photovoltaic properties. Previously studied dye PCA-ZnPc-2 , which contains the same electron donating groups and pyrazole-3-carboxylic acid anchoring group with the bridging oxygen atom, was used as a reference dye. The optimized dye-sensitized solar cell (DSSC) based on PCA-ZnPc-4 exhibited an impressive power conversion efficiency of 2.52% (J(SC) = 6.53 mA cm(-2) , V-OC = 0.584 V, FF = 0.66), exceeding that of the DSSC based on PCA-ZnPc-2 (1.86%) under the same conditions. The better photovoltaic performance of PCA-ZnPc-4 is mainly due to its conjugated anchoring group, leading to efficient electron injection. This work demonstrates that the anchoring groups attached to the macrocycle without oxygen linker may enhance the photovoltaic performance of the phthalocyanine-sensitized solar cells.