Electroluminescence in thin solid films of closely-packed CdS nanocrystals

An all-inorganic structure has been prepared with thin 200-300 nm solid films of closely packed 1.6-1.8 nm CdS nanocrystals sandwiched between ITO and Ag contact layers and electroluminescence behavior has been examined at room temperature. The spectral position of the electroluminescence band is voltage-dependent and exhibits blue shift at increased bias demonstrating the color tunability of electroluminescence output. Voltage-current and bias-intensity curves indicate the hopping conductivity of carriers through the nanogranular semiconductor film. The mechanism of electroluminescence in nanogranular CdS film is suggested to be an impact ionization of deep radiative centers in CdS nanocrystals. (C) 1998 Elsevier Science B.V. All rights reserved.