Comparative study on photo and electroluminescence properties of Cu-doped ZnS

Distinct differences observed in the alternating current powder electroluminescence (ACPEL) and photoluminescence (PL) characteristics of lab-made ZnS:Cu(1%) phosphor have been explained based on variation in donor and acceptor traps (levels) assisted electron-hole recombination upon optical and electrical excitations. The results were also compared with that of commercially available ZnS based phosphor. The fabricated display panel using lab-made ZnS:Cu(1%) sample exhibit bright blue colour electroluminescence. On the other hand, device fabricated using commercially available phosphor display bright cyan colour emission under similar biasing conditions. It is confirmed that the commercially available phosphor is composed of both cubic and hexagonal phases of ZnS whereas the lab-made sample is single phase cubic ZnS. The observed variation in spectral profile for commercial sample with increase in frequency of applied AC signal has been explained based on coexistence of hexagonal and cubic phases of ZnS in the sample.