Papers by Keyword: Luminescence Efficiency

Abstract: CdSe cores with larger radius were prepared by means of two-steps injection of the Cd precursor. Efforts were made to avoid the Ostwald ripening process during the quantum dots grown up. The prepared CdSe cores showed zinc-blende structure with size exceeded over 7 nm. The emission efficiency of prepared quantum dots were 15%, while it increased drastically up to 43% after the formation of ZnCdS shells on the CdSe cores. Morphologies and structures of the quantum dots were characterized by HR-TEM and XRD diffraction. The obtained quantum dots with emission wavelengths more than 660 nm were expected to find their applications in bio-imaging and plant illuminations.

Abstract: In this work, YAG: Ce phosphors coated with ZnO nanoparticles were prepared based on the wet chemical method in ethanol solution at low temperature. The surface character was characterized by XPS and SEM. The XPS spectra showed that the peak positions corresponding to the Zn 2p3/2 , Zn 2p1/2 and O 1s are 1022.08 eV, 1044.88 eV and 530. 8 eV, respectively. The SEM images showed that the surface of YAG:Ce were coated with ZnO nanoparticles. The thickness is about 25 nm. The luminescence properties of YAG:Ce phosphors coated with ZnO nanoparticles were studied. It is found that the photoluminescence intensity of coated phoshors increases a maximum at 12% compared with that of the uncoaed YAG: Ce phosphors and the enhancement of photoluminescence intensity depends on the consistency of ZnO nanoparticles. Finally, the YAG: Ce phosphors coated with ZnO nanoparticles were used for LED package. The results show that the luminescent intensity increases 6.8 % and the quantity of phosphors decreases 1 %. It is important for the lighting product to improve the luminescence intensity of white LED and decrease the cost of package.