High quality CdS/ZnS:Cu quantum dots (QDs) were first synthesized via a green microwave irradiation route. As-prepared core/shell doped QDs presented a strong absorption in the blue light region and highly efficient red to deep red emission with a maximum quantum yield of 40%. The composite formed by dispersing CdS/ZnS:Cu QDs into silicone resin showed an excellent photostability under blue illumination. Finally, high color rendition white light was generated from the CdS/ZnS:Cu QDs-assisted phosphorconverted white light-emitting diode (WLED) in which there was no reabsorption between quantum dots and phosphors. Under operation of 40 mA forward bias current, the fabricated WLED emitted bright natural white light with a high color rendering index of 90, a luminous efficiency of 46.5 lm/W, and the correlated color temperature of 6591 K. Simultaneously, the good color stability was accompanied by the CIE color coordinates of (0.3155, 0.3041) under different forward bias currents.W hite light-emitting diodes (WLEDs) have drawn considerable attention in recent years due to their long lifetimes, low power consumption, fast response, high luminous efficiency, and so on. 1−5 Currently, the most popular commercial WLEDs are based on a blue LED chip with a yellow-emitting Y 3 Al 15 O 12 :Ce 3+ (YAG:Ce) phosphor, due to their simple structure, high luminous efficiency, and low cost. 6 However, it is difficult for this type of WLEDs to achieve a high color rendering index (Ra) due to the lack of red components in the emission. In order to improve the color rendering properties, red-emitting inorganic phosphors and colloidal quantum dots (QDs) such as Ca 2 SiO 4 :Eu 2+ , Sr 2 Si 5 N 8 :Eu 2+ , CdSe, CdSe/ZnSe, and CuInS 2 with high photoluminescence quantum yield (PLQY) have been developed for WLEDs with excellent Ra. 2,7−15 Nonetheless, the reabsorption between multiple phosphors as well as the intrinsic small Stokes shift of QDs usually induces a strong self-quenching effect, which results in significant color altering and a decrease in the luminous efficiency of WLEDs. 16,17 Recently, transition metal ion doped semiconductor quantum dots (d-QDs) have been widely investigated due to their unique optical properties. 18−23 They not only retain advantages of intrinsic QDs but also have new properties, such as longer lifetimes, improved thermal and photochemical stability, and especially the minimization of the vexing selfabsorption owing to the enlarged Stokes shift. 20,24−27 Therefore, in comparison with intrinsic QDs, d-QDs are more suitable to solve the low Ra problem of YAG:Ce-based WLEDs. Recently, Cu-doping is recognized as a versatile strategy for

High quality cadmium-free Zn-In-S:Ag doped-nanocrystals (d-NCs) were synthesized via a simple one-step noninjection route using silver nitrate, indium acetate, zinc acetate, oleylamine, S powder and 1-dodecanethiol as starting materials in an organic phase. The size and optical properties can be effectively tailored by controlling the reaction time, reaction temperature, Ag+ dopant concentration, and the molar ratio of In to Zn. The photoluminescence wavelength of as-prepared Zn-In-S:Ag NCs covered a broad visible range from 458 nm to 603 nm. After being passivated by protective ZnS shell, the photoluminescence quantum yield (PLQY) of Zn-In-S:Ag+ /ZnS was greatly improved to 43.5%. More importantly, the initial high PLQY of the obtained core/shell d-NCs in organic media can be preserved when being transferred into the aqueous media via ligand exchange. Finally, high quality Zn-In-S:Ag+ /ZnS d-NCs in aqueous phase were applied as bio-imaging agents for identifying living KB cells.

CdSe/CdS/ZnS QDs synthesized by microwave irradiation were first applied to Si solar cells to improve the conversion efficiency by 5.2%.

Abstract