Electroluminescence and spectral shift of CdS nanoparticles on Si wafer

Preparation of CdS nanoparticles, device fabrication, and electroluminescence properties at room temperature of CdS nanoparticles on silicon substrates are reported. 86-meV spectral shift of free exciton transition due to passivation of the p-hydroxyl thiophenol group around nanoparticles is found. Controlled process conditions such as heat treatment and/or with oxygen-rich environment are experimented with and are found to have significant influences on emission spectra. Radiative recombination corresponding to oxygen-impurity level, 273 meV below bandgap energy, presents in samples prepared in oxygen-rich environment. In addition to such a mechanism, coalescence of nanoparticles into bulk form also exists and contributes to enhanced luminescence