Electrochemical and photoelectrochemical properties of monoaza-15-crown ether linked cyanine dyes: photosensitization of nanocrystalline SnO<SUB>2</SUB> films

Photophysical, electrochemical, and photosensitization properties of newly synthesized crown ether derivatives of cyanine dyes have been investigated. These dyes exhibit strong absorption in the visible (450-550 nm) range with a solvent-dependent fluorescence quantum yield ranging from 0.006 to 0.11 and adsorb strongly on SnO2 nanocrystallites. The singlet excited state is readily quenched when adsorbed on SnO2 nanocrystallites as a result of a charge injection process. The photosensitization properties of these cyanine dyes in extending the photoresponse of SnO2 semiconductor have been investigated by probing the dependence of photocurrent and photovoltage on the wavelength and intensity of excitation. A maximum photon to photocurrent conversion efficiency of ~1% has been observed