Effect of strength and frequency of the field on some rare earth activated zinc oxide electroluminors

A series of rare-earth (Dy, Yb, Nd, Sm, Pr, Gd, La and Er) doped ZnO electroluminors have been prepared in vacuum and voltage and frequency dependence of time-averaged electroluminescent brightness of these systems have been investigated. Brightness-voltage relation B = Bsub(o) exp(-b/V/1/4) is satisfied for all the electroluminors with slight deviations at lower and higher frequencies in some of the systems. At lower voltages the electroluminescent brightness is found to increase very slowly with the increase of frequency and a state of saturation is observed at higher frequencies in some of the electroluminors. At higher voltages the frequency dependence is found to be more linear. Further, the electroluminescent spectra consist of three peaks which shift towards the shorter wavelength side with the increase in the frequency of the applied field. All these phenomena have been discussed in the light of existing models. (auth.)