Luminescence characteristics of SrS:CeF3 thin-film electroluminescent devices

The response of a blue SrS:CeF₃ AC thin-film electroluminescent display device to a pulsed voltage train is marked by a luminescence peak at both the leading and trailing edges of the pulse. The height of the leading peak is less than that of the trailing peak at low (near threshold) voltages but grows much larger than the trailing peak at higher voltages. The spectral content of the luminescence in the two peaks is very close. Areas under the two peaks are sensitive functions of the amplitude and the pulse width of the excitation voltage. The results are interpreted by a model that attributes the trailing peak to the presence of shallower or nonequilibrium states at the phosphor-insulator interface. Also present are the deeper or equilibrium states at the interface and the midgap states in the bulk SrS. Electrons that initiate the leading edge luminescence come from all three of these states. Electrons that initiate the trailing edge luminescence are thought to emanate from the shallower interface states