ELECTRO- AND PHOTO-LUMINESCENCE STUDIES OF CdS NANOCRYSTALS PREPARED BY ORGENOMETALLIC PRECURSOR

The optical and electrical properties of semiconductor nanoparticles are strongly dependent on their size. Here we report the size dependence of photo- and electro luminescence of CdS nanocrystals prepared by single source orgenometallic precursor. The precursor was prepared by dissolving CdCl2, thiourea and NaOH in ethanol. The mixed solution was kept at 60 degrees C and samples were extracted at different reaction times. The samples were characterized by transmission electron microscopy and x-ray diffraction. For shorter reaction time small CdS nanocrystals are obtained, which exhibit blue-shift in absorption edge. In PL spectra one peak is observed at 528 nm. peak may be attributed to shallow bound exictons. Electroluminescence (EL) studies show that the light emission starts at some threshold voltage and increases rapidly with increasing applied voltage. It is seen that smaller CdS crystals give electroluminescence of higher brightness starting at lower threshold voltage. It seems that the EL in CdS nanoparticles arises due to the high electric field, in which band bending causes release of trapped electrons and their subsequent recombination with holes give rise to the light emissions.