Effect of CdSe Precursor Mol Concentration on the Particle Growth of CdSe Quantum Dots Synthesized at Low Temperature

Abstract

Colloidal semiconductor nanocrystal or quantum dots (QDs), with size-tunable band gaps are applicable in a number of technologies, such as light emitting diodes (LEDs), fluorescence tags for biological molecules, and solar cells. CdSe QDs have become one of the most extensively studied because they exhibit wide band gap, high luminescence efficiency, and narrow full width at half maximum. In this study, CdSe QDs are synthesized at a relatively low temperature of 190 degrees C by using a hot-injection method in a batch type process. The crystallites, band gap, and luminescent behaviors are evaluated to understand effects of CdSe precursor mol concentration and reaction time on the CdSe QD properties. From the red shift of the UV-vis and photoluminescence (PL) results, we estimated the particle size of CdSe QDs to be about 3.66, 3.82, and 4.81 nm for Cd precursor mol concentration of 0.1, 0.3, and 0.5 M, respectively. The CdSe QD size increases with increasing mol concentration of Cd precursor from 0.1 M to 0.5 M and increasing reaction time from 6 to 10 min. The XRD results also confirm the same behavior. The growth mechanism of the CdSe QDs is attributed to more nuclei formation by supersaturation or to nuclei diffusion growth. The QD size is thus tunable by changing the precursor concentration.