Preparation and Photoeletrochemical Performance of CdS Quantum Dot Sensitized ZnO Nanorod Array Electrodes

We sensitized CdS quantum dots on a ZnO nanorod array electrode by the successive ionic layer adsorption and reaction method. Scanning electron microscopy (SEM), X. ray diffraction (XRD), and transmission electron microscopy (TEM) experiments were performed to characterize the morphology, crystalline phase, and grain size of the CdS quantum dot sensitized ZnO nanorod array electrodes. The effect of CdS deposition cycle number and the precursor concentration were studied by photocurrent-potential characteristics and photocurrent spectra. The results showed that the best photoelectrochemical performance was obtained at 0.1 mol.L-1 for both Cd2+ and S2- after 15 cycles. Meanwhile, the composite films exhibited a remarkably enhanced photoelectric conversion efficiency compared with the ZnO nanorods array films and with CdS quantum dot electrodes. The monochromatic incident photon. to. electron conversion efficiency (IPCE) was as high as 76% at 380 nm. This may be attributed to the broad light harvesting capability of CdS and the efficient separation of photogenerated carriers on its interface. The reason for this enhancement was further confirmed by a photoluminescent experiment. The results showed that sensitization with CdS quantumdots reduced the recombination of electron and hole pairs resulting in an enhancement in the photocurrent.