Characterization of nanostructured TiO2 electrodes sensitized with CdSe quantum dots using photoacoustic and photoelectrochemical current methods

Two types of nanostructured titanium dioxide (TiO2) electrodes were prepared with anatase TiO2 nanoparticles of different sizes (average diameters of 15 and 27 nm). CdSe quantum dots were adsorbed onto each of the two types of TiO2 electrodes, by a chemical deposition (CD) technique, the average sizes of which increased to 7 nm on increasing the deposition time. Optical absorption and photoelectrochemical properties were characterized by using photoacoustic (PA) and photoelectrochemical (PEC) current methods. Redshift of the PA and PEC current spectra with increasing CdSe sizes was clearly observed, which indicates quantum confinement effects and photosensitization by the CdSe quantum dots. It was found that the PEC current spectra in the visible region were quite different for the two types of TiO2 electrodes for the same deposition time, although the PA spectra were very similar to each other. The correlation of the PEC current spectra with the microstructures of the two types of TiO2 electrodes was discussed, which provided information that could lead to the optimization of dye-sensitized solar cells (DSSC).