Arrays of ZnxCd1-xSe/TiO2 nanotubes: fabrication by ion-exchange and photovoltaic applications

Free-standing TiO2 nanotube (NT) array films were prepared by anodization approach as support materials for quantum dots sensitized solar cells (QDSSCs). The ZnxCd1-xSe quantum dots (QDs) layers with tunable compositions have been deposited on the TiO2 NT array film via a simple ion-exchange approach. The optical absorptions of the ZnxCd1-xSe/TiO2 NT can be controllably tuned to cover almost the entire visible region by changing the atomic ratio of Zn to Cd. In the fabricated QDSSCs based on these ZnxCd1-xSe/TiO2 NT array photoanodes, the photovoltaic performance gradually improved as the composition changes from Zn-rich to Cd-rich of ZnxCd1-xSe QDs layers on TiO2 NT arrays. In contrast with other ZnxCd1-xSe/TiO2 NT solar cells, the Zn0.13Cd0.87Se/TiO2 NT solar cell yielded a highest power conversion efficiency of 2.15 %, indicating the most effective band alignment is obtained with Cd-rich ZnxCd1-xSe QDs layers. It can be anticipated that tunable energy band of QDs controlled by the ratio of atoms can contribute to higher efficiency QDSSCs.