Enhanced photoelectrochemical response of CdSe quantum dot-sensitized p-type NiO photocathodes

CdSe quantum dots (QDs) were deposited on a p-type nanoporous NiO surface by repeating the successive ionic layer adsorption and reaction (SILAR) procedure from 6 to 15 cycles. All of the CdSe QD-assembled NiO films exhibited much better p-type photoelectrochemical (PEC) performances than the bare NiO film. In particular, the NiO film with CdSe QD prepared from the 12 SILAR cycles exhibited a significantly enhanced p-type PEC response, due to an effective light absorption in the long wavelengths and the increased loading amount of the assembled QDs. However, as the SILAR cycles further increased up to 15, the QD-assembled NiO film exhibited the reduced PEC performance, despite better light absorption in the long wavelengths. This was because of the suppressed ion transport, poor charge transfer, and non-active aggregated QDs, facilitating the recombination reaction.