Quantum dots that efficiently emit white light directly or feature a "candle-like" orange photoluminescence with a high Stokes shift are presented. The key to obtaining these unique emission properties is through controlled annealing of the core Cu-In-Ga-S quantum dots in the presence of zinc ions, thus forming Zn-Cu-In-Ga-S solid solutions with different distributions of the substitution and dopant elements. The as-obtained nanocrystals feature excellent quantum yields of up to 82% with limited or even eliminated reabsorption and a color rendering index of bare particles of up to 88, enabling the production of high-quality white LEDs using a single color converter layer. Furthermore, the color properties can be tuned by changing the experimental conditions as well as by varying the excitation wavelength. The multicomponent luminescence mechanism is discussed in detail based on similar literature reports. White LEDs with unparalleled color quality and competitive luminous efficacies are presented herein.
A Facile Synthesis of Alloyed Mn-Doped ZnSeS Nanoparticles Using a ModifiedSelenium/Sulfur Precursor in a One-Pot Approach. -Highly luminescent Mn doped ZnSeS nanoparticles are prepared by adding a modified Se/S-precursor solution consisting of Se powder, NaBH 4, and different amounts of 1-dodecanethiol in oleylamine to a solution of manganese stearate in 1-octadecene at 240 C. The solution then is cooled to 220 C and a zinc stearate solution in MeOH is added and again heated to 240 C (20 min) prior to precipitating the nanoparticles with MeOH. The main challenge of the phosphine-free synthesis of metal selenide nanoparticles is the solubility and reduction of elemental Se in organic solvents without the use of alkylphosphine. The modified Se/S-precursor optimizes the preparation of highly luminescent alloyed nanostructures in view of required time and purification steps. The prepared monodisperse nanoparticles possess an average particle size of 6.8 nm and high quality optical properties with up to 42% photoluminescence quantum yield, the latter being significantly affected by the ratio of S to Se in the precursor solution. -(ZIMDARS*, J.; PILGER, J.; ENTRUP, M.; DEITING, D.; SCHAEFER, A. H.; BREDOL, M.; New J. Chem. 40 (2016) 10, 8465-8470 ; Dep. Chem. Eng., Muenster Univ. Appl. Sci., D-48565 Steinfurt, Germany; Eng.) -J. Schramke 50-007
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