Highly Luminescent CdSe/CdxZn1-xS Quantum Dots with Narrow Spectrum and Widely Tunable Wavelength

We exploit the synthesis of CdSe core and CdSe/CdxZn1-xS core shell quantum dots (QDs) with spherical and rod morphologies through a controlled core formation and single coating step by using different growth kinetics of CdS and ZnS. The size and morphology of CdSe cores depended strongly on the injection speed of trioctylphosphine selenium (TOPSe), reaction temperature, and time. The cores with spherical morphology exhibited tunable photoluminescence (PL) wavelength from 544 to 623 nm. CdSe cores with rod morphology and a PL peak wavelength of 623 nm were prepared when TOPSe was injected slowly. The molar ratio of Cd/Zn upon preparation was adjusted for investigating the effect of the CdxZn1-xS shell on the properties of the resulting core shell QDs. The coated QDs exhibited a controlled red shift from the initial PL of CdSe cores with much improved PL efficiency (a maximum value of 89%). CdSe/CdxZn1-xS core shell QDs prepared by using those rod cores exhibited a PL peak wavelength of 652 nm and a PL efficiency of 61%. All resulting core shell QDs exhibited narrow PL spectra (full-width at half-maximum of 23-29 nm). High PL efficiency and narrow PL spectra in the wide visible range make these core shell QDs attractive for applications.