EFFECTS OF CRYSTALLINITY ON THE LUMINESCENCE OF ZNS-TB,P POWDER AND FILM

To investigate the possibility of applying donor (D)-acceptor (A) pair emission in ZnS crystals to electroluminescence (EL) devices, the luminescence properties of ZnS:Tb,P are examined. In the cathodoluminescence spectra of ZnS:Tb,P powder, f-f emission of Tb3+ ions and D-A pair emission related to Tb donors and P accepters are observed. It is found that D-A pair emission decreases more easily than f-f emission with degradation in crystallinity. In the cathodo- and electroluminescence of ZnS:Tb,P film, however, only f-f emissions, not D-A pair emissions, are observed. This is because of the lack of good crystallinity in the film. Based on these findings, it is proposed that not only less distortion but also a critical size are required for the observation of D-A pair emission in ZnS films.