The Electron Injection Mechanism of the Electroluminescent ZnS: Tb3+Films

The role of interfacial states in the electroluminescence process for Ta-Ta 2 O 5 -ZnS: Tb 3+ -Au and Ta-Ta 2 O 5 -ZnS: Tb 3+ -SiO 2 -Au structures has been studied. A similar electroluminescence has been observed for both types of cells. This indicates that electron injection via tunneling from the Au contact is not necessarily required to produce electroluminescence. The relaxation times of electrons related to the injection process from interfacial states are measured to be 10–100 ms. These values are the same for three interfacial states of interest (ZnS-Au, ZnS-SiO 2 and ZnS-Ta 2 O 5 ). Their temperature and electric field dependences are also presented. It can be concluded that field emission from the interfacial states is essential to the electron injection process for these types of cells.