CdTe quantum dots-sensitized TiO₂ nanotube array photoelectrodes

TiO₂ nanotube array films, formed by anodic oxidation, have been shown to yield high efficiency of charge generation and collection in photoelectrochemical (PEC) devices. However, the wide band gap (3.2 eV) of TiO₂ limits the efficiency of these devices in the visible region. In this work, four types of presynthesized CdTe quantum dots (QDs) of different sizes were deposited into the TiO₂ nanotubes to serve as the sensitizers, and the performance of the CdTe QD-sensitized TiO₂ nanotube arrays was measured in a PEC solar cell. It is found that, with decreasing particle size, the driving force for electron injection increases while the visible light response decreases. Maximum photocurrent was obtained for the QDs that have an absorption peak at 536 nm. Under AM 1.5 G illuminations, a 6 mA/cm² short circuit current density is achieved, which presents a 35 times improvement compared to that based on using a plain TiO² nanotube film.