Bright green electroluminescence in thin-film ZnS : TbF3

Abstract
A bright green electroluminescent (EL) thin‐film device for a flat‐type display has been developed. The device is constructed by a ZnS : TbF3 thin‐film sandwiched between two semiconductive Y2O3 layers. A typical brightness of 200 fL and a power conversion efficiency of 4×10−4 W/W, values at least several times higher than reported elsewhere for green‐color thin‐film EL, are stably obtained at an excitation frequency of 5 kHz. This device is also capable of dc excitation with high efficiency (1×10−3 W/W) due to the existence of a semiconductive Y2O3 layer instead of an insulating layer. The semiconductive Y2O3 layer used in this device plays an important role in producing carriers in the ZnS active layer. Technical data on the characterization of the carrier injection mechanism and the device performance are presented and discussed.