ELECTROLUMINESCENCE AT THE NORMAL-ZNO/ELECTROLYTE INTERFACE - A COMPARATIVE-STUDY OF THE EMISSION PROCESSES UNDER CATHODIC AND ANODIC PULSED POLARIZATION

Electroluminescence (EL) of polycrystalline n-ZnO(N//D equals 5 multiplied by 10** plus **1**8 cm** minus **3) electrodes in aqueous electrolytes is studied (i) under cathodic polarization during reduction of the S//2O//8**2** minus ions and (ii) under strong anodic polarization in a supporting electrolyte. The pulsed technique used here avoids a too rapid electrochemical decomposition of the electodes. Under cathodic conditions (i), the EL onset V//o//n**E**L equals minus 0. 4V vs. SCE (pH 3. 0) is only 0. 3V negative to the flatband potential V//F//B and indicates a hole injection into ZnO. The two-step potential dependence of both emission and current intensities between V//o//n**E**L and minus 4. 0V vs. SCE evidences the direct relationship between the interfacial electrochemical events and the radiative recombinations of e OVER BAR /h** plus pairs inside the material.