Cyclic free-base porphyrin dimers (H4-C4-CPDPy(TEO) and H4-Ptz-CPDPy(TEO)) linked by butadiyne or phenothiazine bearing four 4-pyridyl groups and their inclusion complexes (C60⊂H4-C4-CPDPy(TEO) and C60⊂H4-Ptz-CPDPy(TEO)) with fullerene C60 have been applied to dye-sensitized solar cells (DSSCs) as a new class of porphyrin dye sensitizers with pyridyl anchoring groups for attachment on a TiO2 electrode. The FTIR spectra of the porphyrin dimers adsorbed on TiO2 nanoparticles demonstrated that these porphyrin dimers are adsorbed on the TiO2 surface through the formation of hydrogen bonding of pyridyl groups and/or pyridinium ions at Brønsted acid sites on the TiO2 surface. The adsorption amount of the porphyrin dimers adsorbed on the TiO2 electrode is 2.0 × 1017 molecules per cm2, that is, the adsorption amount of the porphyrin unit is 4.0 × 1017 cm-2, which is higher than that of dye sensitizers with pyridyl groups reported so far. The photovoltaic performance of DSSCs based on phenothiazine-bridged cyclic porphyrin dimer H4-Ptz-CPDPy(TEO) is higher than that of DSSCs based on butadiyne-linked cyclic porphyrin dimer H4-C4-CPDPy(TEO). Moreover, the photovoltaic performances of DSSCs based on cyclic free-base porphyrin dimers are higher than those of DSSCs based on their C60 inclusion complexes C60⊂H4-C4-CPDPy(TEO) and C60⊂H4-Ptz-CPDPy(TEO). On the basis of the electrochemical measurements (voltammetry and electrochemical impedance spectroscopy) and the transient absorption spectroscopy, the differences in the photovoltaic performances among these cyclic free-base porphyrin dimers are discussed from kinetic and thermodynamic considerations concerning the electron transfer processes in DSSCs.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)