Dye-sensitized solar cell based on an inclusion complex of a cyclic porphyrin dimer bearing four 4-pyridyl groups and fullerene C60. Issue 20 (8th February 2016) - Ooyama, Yousuke
Abstract : Cyclic free-base porphyrin dimers linked by butadiyne or phenothiazine bearing four 4-pyridyl groups and their inclusion complexes with fullerene C60 have been applied to dye-sensitized solar cells as a new class of porphyrin dye sensitizers. Abstract : Cyclic free-base porphyrin dimers (H4 -C4 -CPDPy (TEO) andH4 -Ptz-CPDPy (TEO) ) linked by butadiyne or phenothiazine bearing four 4-pyridyl groups and their inclusion complexes (C60 ⊂H4 -C4 -CPDPy (TEO) andC60 ⊂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 × 10 17 molecules per cm 2, that is, the adsorption amount of the porphyrin unit is 4.0 × 10 17 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 dimerH4 -Ptz-CPDPy (TEO) is higher than that of DSSCs based on butadiyne-linked cyclic porphyrin dimerH4 -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 complexesC60 ⊂H4 -C4 -CPDPy (TEO) andC60 ⊂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.