Luminescence of ZnS:Cu,Cl Phosphor Powder Excited by Photons, An Electric Field and Cathode rays

摘要

Semiconductor zinc sulfide (ZnS), with bandgap energies of 3.7eV and 3.8eV in zinc-blende and wurtzite structures [1], respectively, has great potential for use in solar cells [2], infrared windows [3], and phosphor materials. These material properties are achieved by doping with transition or rare-earth metals [4,5] and are based on its large bandgap energy, direct recombination and high resistance to electric fields. Additionally, owing to the advantages of its simple manufacturing process, the convenience of being able to print a large area and its high power efficiency, ZnS phosphor powder could be excited by photons, cathode rays or an electric field for back lighting of liquid crystal panels or for flat panel displays. The most widely used form of this phosphor material is ZnS:Cu,Cl, in which Cu and Cl behave as acceptors and donors, respectively, and are both contributing to the emission. The luminescence or emission color of ZnS phosphor powder can be classified into five kinds, depending on the relative concentration of activators (Cu) and co-activators (Cl) [6]. Cu doping can cause phase transformation, Gu_xS precipitation and tensile strain in ZnS by substituting Zn sites or interstitially entering the lattice, which were observed via Raman, transmission electron microscopy (TEM) and x-ray diffraction (XRD) analyses [7-9].