Luminescence Enhancement of ZnS:Cu Nanocrystals by Zinc Sulfide Coating with Core/Shell Structure

Abstract

Via wet chemical method with organic assistant, ZnS:Cu/ZnS core/shell structure was prepared. X-ray diffraction measurements showed that ZnS:Cu was formed with zinc blende structure, and ZnS shell growth on the surface was indicated through a red-shift in the UV-Vis absorption spectra with increasing particle size. The emission peak at about 510 nm was observed, which should be assigned to recombination of an electron from the shallow delocalized donor levels at the t₂ level of Cu²⁺ centers. As passivation layer, effect of ZnS shell on luminescence intensity and lifetime of ZnS:Cu were investigated. Comparing with uncoated ZnS:Cu, ZnS shell really enhanced the luminescence intensity and lifetime significantly, which resulted from the reduction of nonradiative recombination sites.

Keywords:

• ZnS:Cu
• core/shell structure
• surface passivation
• luminescence property
• lifetime