Effects of Porphyrin Substituents and Adsorption Conditions on Photovoltaic Properties of Porphyrin-Sensitized TiO2 Cells

A series of ineso-tetraphenylzineporphyrins have been prepared to examine the effects of the porphyrin substituents and adsorption conditions on photovoltaic properties of the porphyrin-sensitized TiO2 cells. The cell performance strongly depended on the linking bridge between the porphyrin core and the TiO2 surface, the bulkiness around the porphyrin core, and the immersing solvents and tirnes for the porphyrin adsorption, In particular, the high cell performance of the porphyrin-sensitized TiO2 cells was achieved when protic solvent (i.e., methanol) and short immersing time (0.5-1 h) were used for the conditions of the dye adsorption on TiO2, which is in sharp contrast with Ru dye-sensitized TiO2 cells. The highest cell performance was obtained with 5-(4-carboxyphenyl)-10,15,20-tris(2,4,6-trimethylphenyl)porphyrinatozine(II) as a sensitizer and methanol as an immersing solvent with an immersing time of 1 h: a maximal incident photon-to-current efficiency of 76%, a short circuit photocurrent density of 9.4 mA cm(-2), an open-circuit voltage of 0.76 V, a fill factor of 0.64, and a power conversion efficiency of 4.6% under standard AM 1.5 sunlight. These results will provide basic and valuable information on the development of dye-sensitized solar cells exhibiting a high performance.