Semiconductor electrodes. Part 51: Efficient electroluminescence at ZnS electrode in aqueous electrolytes
Abstract
Electroluminescence (EL) on ZnS was studied in aqueous solutions containing various redox species. For species able to generate strongly oxidizing intermediates, such as peroxydisulfate or hydrogen peroxide, bright blue luminescence was observed during cathodic polarization at potentials near to or negative of flat-band potential (Vfb) of ZnS. For solutions containing supporting electrolyte alone at various pH's, no emission was detectable even at potentials 7 volts negative of Vfb. This suggests that minority-carrier (hole) injection is responsible for the initiation of EL. The peak energy of the EL spectrum was much smaller (by 1 eV) than the bandgap of ZnS, suggesting that the radiative recombination is through intermediate luminescent centers. Under steady state conditions, the EL intensity was proportional to the square of the current, suggesting that EL intensity is dominated by the recombination of electron-hole pairs at luminescent centers. In the early part of a potential pulse (especially the first pulse), the growth behavior of EL intensity was strongly affected by the electron trapping of the empty upper luminescent states. The location of the EL spectra depended on the current density and the EL intensity; with increasing EL intensity, a significant blue shift of the emission peak was observed.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- April 1983
- Bibcode:
- 1983STIN...8331966F
- Keywords:
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- Electrodes;
- Electroluminescence;
- Electrolytic Cells;
- Holes (Electron Deficiencies);
- Oxidation-Reduction Reactions;
- Semiconductors (Materials);
- Zinc Sulfides;
- Display Devices;
- Electric Current;
- Electrochemistry;
- Emission Spectra;
- Hydrogen Peroxide;
- Ionization Potentials;
- Luminescence;
- Photoelectric Emission;
- Electronics and Electrical Engineering