Optical absorption, photoelectrochemical, and ultrafast carrier dynamic investigations of TiO2 electrodes composed of nanotubes and nanowires sensitized with CdSe quantum dots

TiO2 electrodes composed of nanotubes and nanowires are prepared from TiO2 gels using a surfactant-assisted self-assembly method reported earlier. CdSe quantum dots (QDs) are adsorbed onto the. TiO2 electrodes by chemical deposition (CD). Their average size increases from 4 to 6nm with increasing deposition time from 3 to 82h. The optical absorption and incident photon-to-current conversion efficiency (IPCE) of the electrodes are studied by photoacoustic (PA) and plIiotoelectrochemical (PEC) methods. The photosensitization of the TiO2 electrodes by CdSe QDs is demonstrated by both PA and IPCE spectra. The ultrafast carrier dynamics of the CdSe-sensitized TiO2 electrodes composed of nanotubes and nanowires is studied using a lens-free heterodyne detection transient grating (LF-HD-TG) technique.,Fast and slow decay processes with lifetimes of about 3 ps and 60-130 ps, respectively, are observed.