ZnO/CdS/CdSe core/double shell nanorod arrays derived by a successive ionic layer adsorption and reaction process for quantum dot-sensitized solar cells

Well-aligned one-dimensional ZnO nanorod arrays were grown on transparent conducting glass, and CdS and CdSe quantum dot thin films were then deposited on the nanorod arrays in turn by an effective successive ionic layer adsorption and reaction process to form a ZnO/CdS/CdSe core/double-shell structure electrode. As revealed by the images of filed-emission scanning electron microscopy and transmission electron microscopy, the CdS and CdSe quantum dot thin films were uniformly deposited on the ZnO nanorods and the thickness of the CdS and CdSe shell can be controlled by varying the number of the adsorption and reaction cycles. For a typical sample that was prepared by a 10 times adsorption and reaction cycle, the thickness of the CdS and CdSe shell was about 4.0 and 5.5 nm, respectively. A short circuit density of 12.1 mA cm ^-2 and a power conversion efficiency of 1.72% were obtained for the solar cell based on the optimal ZnO/CdS/CdSe core-shell nanorod array electrode under the illumination of one sun (AM1.5, 100 mW cm^-2).