CdSe/ZnS/CdS core/shell quantum dots for white LEDs

With their excellent photo-electronic properties, quantum dots, especially the II-VI family semiconductor quantum dots, are now widely used to photo- and electro-luminescence device such as inorganic and organic light emitting diodes recently. The quantum dots have many applications in optoelectronic device such as LEDs for its many superior properties resulting from the three-dimensional confinement effect of its carrier. In this paper, White light-emitting diodes (WLEDs) were fabricated by combining blue InGaN chips with luminescent colloidal core/shell CdSe/ZnS/CdS quantum dots (QDs). The core/shell/shell structural CdSe/ZnS/CdS nanocrystals were synthesized in aqueous solution by using mercapto-acetate as stabilizer. The double shell can improve the core/shell interface quality. Photoluminescence of CdSe/ZnS/CdS quantum dots demonstrated high photoluminescence efficiency with a quantum yield more than 45%, and size-tunable emission wavelengths from 490 to 610nm. WLED was successfully assembled by blue InGaN chip plus green and red emitting CdSe/ZnS/CdS QDs. The WLED had the CIE coordinates of (0.33,0.34) and color render index of 91. The InGaN chip white-light-emitting diodes with CdSe/ZnS/CdS quantum dots are potentially useful in general illumination and display applications.