Strategy for performance enhancement of Cd1-XZnXTe/CdS core/shell quantum dot sensitized solar cells through band adjustment

Novel type-II core/shell structure quantum dos have been synthesized for solar cell photoelectrode material. Cd0.64Zn0.36Te and CdS were chosen as a core and shell, respectively, to generate type-II core/shell structure quantum dos (QDs). Density functional theory was employed to explore the energy structure of Cd1-xZnxTe/CdS core/shell QDs, revealing that introduction of Zn element is a feasible strategy to prepare CdTe/CdS based QDs with type-II core/shell structure. Then, Cd0.64Zn0.36Te/CdS core/shell QDs were synthesized by aqueous phase method. Microscopic measurements showed that Cd0.64Zn0.36Te/CdS core/shell QDs have high crystalline quality. Ultraviolet photoelectron spectroscopy together with optical spectra indicated an upward shift of the Cd0.64Zn0.36Te conduction band edge compared with CdTe, as also evidenced by systematic density functional theory based first principle calculation. Photoluminescence decay measurement also indicated the enhanced electron injection rate and decreased charge recombination of Cd0.64Zn0.36Te/CdS QD sensitized TiO2 films. In addition, by optimizing the deposition cycles of the CdS shell, the power conversion efficiency of Cd0.64Zn0.36Te/CdS QDs sensitized solar cells was enhanced.