Electroluminescence kinetics in thin-film ZnS-based devices at ultralow frequencies

The variation of the instantaneous luminance from thin-film electroluminescent structures excited by alternating-sign sawtooth voltage pulses with a pulse rate of 0.1–2.0 Hz is studied. From the solution of the kinetic equation, the time dependences of the instantaneous luminance and the internal quantum yield are obtained. The time dependences of the luminance and the current exhibit two, “fast” and “slow,” rising portions, which correlate with various specific regions in the field and charge dependences of the luminance and other electrophysical parameters. The results are explained by the formation of space charges in the phosphor layer, causing a decrease in its effective thickness, and by a change in the luminescence mechanism.