Red Electroluminescence and Crystallinity of ZnS:SmF3 Thin Films

Abstract

The dependence of the red emission characteristics (emission efficiency, brightness and emission decay time) and crystallinity of ZnS:SmF₃ thin-film electroluminescent (TFEL) devices upon fabrication parameters such as the SmF₃ concentration and substrate temperature during evaporation, has been investigated. The electroluminescent characteristics are considered to be influenced more by the SmF₃ concentration and the grain height in the film thickness direction, than by the cubic ZnS structure {111} plane orientation and the film uniformity, or by the degree to which the cubic {111} plane is oriented parallel to the substrate. A bright red electroluminescence of 1000 cd/m² under 5 kHz sinusoidal voltage excitation and an emission efficiency of 0.078 lm/W are obtained in these ZnS:SmF₃ TFEL devices.