Dye-Sensitized Solar Cells Based on a Novel Fluorescent Dye with a Pyridine Ring and a Pyridinium Dye with the Pyridinium Ring Forming Strong Interactions with Nanocrystalline TiO2 Films
As new-type donor-acceptor π-conjugated dyes capable of forming a strong interaction between the electron-acceptor moiety of the sensitizers and a TiO 2 surface, fluorescent dye OH11 and pyridinum dye OH12 with a pyridine and pyridinium ring as the electron-accepting group, respectively, have been designed and synthesized as photosensitizers for use in dye-sensitized solar cells (DSSCs). The fluorescent dye OH11 exhibits an absorption band at around 410 nm and a fluorescence band at around 530 nm. On the other hand, the pyridinum dye OH12 shows an absorption maximum at around 560 nm, assigned to a strong intramolecular charge-transfer excitation from the dibutylamino group to the pyridinium ring. The short-circuit photocurrent densities of the DSSCs prepared by using OH11 and OH12 are 4.33 and 1.74 mA cm -2 , and the solar energy-to-electricity conversion yields are 1.33 and 0.51 %, respectively, under simulated solar light [AM (air mass) 1.5, 100 mW cm -2 ]. The open-circuit photovoltage for OH11 (525 mV) is higher than that of OH12 (444 mV). The effects of the configuration of the dyes on the TiO 2 surface and of their chemical structures on the photovoltaic performances are discussed on the basis of semi-empirical molecular orbital calculations (AM1 and INDO/S), spectral analyses and cyclic voltammetry.