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

Four unsymmetrical porphyrins of A2B donor-pi-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 pi-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 H-1 NMR and mass spectrometry. UV-Vis absorption spectra and B or Soret (lambda(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.