Tuning the Charge-Transfer Property of PbS-Quantum Dot/TiO2-Nanobelt Nanohybrids via Quantum Confinement

A newly designed photoactive nanohybrid structure based on the combination of near-infrared PbS quantum dots (QDs) as light harvester and one-dimensional TiO2 nanobelts (NBs) to guide the flow of photogenerated charge carriers is reported. Efficient electron transfer from photoexcited PbS QDs to TiO2 NBs has been demonstrated to occur in the developed PbS-QD/TiO2-NB nanohybrids, and the charge-transfer property can be tuned through the size quantization effect of PbS QDs. Moreover, the use of TiO2 NBs instead of TiO2 NPs permits a larger critical size of PbS QDs capable of injecting electrons into TiO2 NBs, which, in turn, markedly extends the "effective" absorption of the PbS-QD/TiO2-NB nanohybrids to a longer wavelength region up to 1400 nm. Such an extension of the "effective" absorption is a major asset for improving the overall photoconversion efficiency of PbS-QD/TiO2-NB nanohybrids-based photovoltaic devices.