Morphological and Optical Properties of CdS Quantum Dots Synthesized with different pH values

Quantum dots (QDs) of cadmium sulfide (CdS) was prepared by chemical reaction method with different potential of hydrogen (pH) values. The morphological and optical measurements of cadmium sulfide QDs were considered by atomic force microscopy (AFM), ultraviolet-visible (UV-VIS.) and photoluminescence (PL) spectrometer respectively. The energy gap (Eg) was calculated from photoluminescence spectra were found to be about 2.7, 2.6 and 2.5 eV at pH values 8, 10 and 12 respectively for CdS QDs. The decreasing of energy gaps is rises from the effect the pH solution increases, which in turn leads to the shifted of the PL spectrum toward red shifted, which creates the energy bands at surface states are shallow bands. Fabrication of EL-device from CdS QDs with pH=8 was effective in efficient white light generation and intensity.