Ethynyl thiophene-appended unsymmetrical zinc porphyrin sensitizers for dye-sensitized solar cells

Abstract

Four unsymmetrical porphyrins of A2B donor–π–acceptor type have been designed, synthesized, characterized and their photovoltaic properties explored. Polycyclic aromatic hydrocarbons (PAH), such as pyrene or fluorene, act as a donor, the porphyrin is the π-spacer, appended with an ethynyl thiophene linker, and either cyanoacrylic acid or malonic acid acts as the acceptor. All of the compounds were characterized by ¹H NMR and mass spectrometry. UV-Vis absorption spectra and B or Soret (λ_ex at 440 nm for the four sensitizers reported) band-excited fluorescence emission spectra were also obtained. The electrochemical properties suggest that the first oxidation is ring-centred, which is supported by in situ spectro-electrochemical and DFT computational studies. The synthesized porphyrins were applied in dye-sensitized solar cells (DSSCs). A conversion efficiency of up to 3.14%was realized for PYR–Por–MA under our experimental conditions.