The structure and photovoltaic properties of double-shell TiO_2/ZnSe/CdSe nanocable arrays synthesized by using TiO_2/ZnO nanocables template

摘要

A simple method was reported for the first time to synthesize ZnSe/CdSe co-sensitized TiO_2 nanorod arrays. TiO_2/ZnO nanocables were firstly prepared by magnetic sputtering ZnO films on TiO_2 nanorod arrays, and the TiO_2/ZnSe nanocables were synthesized by selenization of TiO_2/ZnO nanocables with Se~(2-) ions. Finally, CdSe quantum dots (QDs) were electrodeposited on the TiO_2/ZnSe nanocables forming a TiO_2/ZnSe/CdSe tri-layer configuration. It is found that the tri-layer photoelectrode has a complementary effect in the light absorption, while the ZnSe shell acts as a blocking layer to retarding the interfacial recombination. Furthermore, a stepwise band alignment structure was constructed in the TiO_2/ZnSe/ CdSe electrode, which greatly speeds up the transfer rate of photoexcited electrons from CdSe to TiO_2. Thus, the TiO_2/ZnSe/CdSe electrode presented better photovoltaic performance than the single shell. Through optimization the thickness of ZnSe layer in the TiO_2/ZnSe/CdSe photoelectrode, a highest power conversion efficiency of 1.33% was obtained.