In this study, we present a novel synthesis system for AgInS 2 /ZnS (AIS/ZnS) core/shell quantum dots (QDs) terminated with carboxymethyl chitosan (CMC) as a ligand, which has not been previously documented. By varying the Ag/In ratio, we achieved emission wavelengths ranging from 590 to 697 nm, with the maximum photoluminescence quantum yield (PLQY) of 33.1 %. The synthesized AIS/ZnS QDs powder was mixed with YAG phosphor and combined with a blue gallium nitride (GaN) chip to produce a warm white light-emitting diode (WLED), resulting in the color rendering index (CRI) increase from 74 to 82 and the correlated color temperature (CCT) decrease from 6486 K to 3873 K. Additionally, the AIS/ZnS QDs powder can be directly utilized with a blue GaN chip to create a near-infrared light-emitting diode (NIR-LED) capable of night vision. By adjusting the concentration of CMC in the AIS/ZnS QDs solution, the material can be directly used for writing and screen printing, or dried to obtain a highly transparent and luminescent flexible composite film. This research demonstrates the significant potential of CMC-ligated AIS/ZnS core/shell QDs in display technologies and flexible device applications.
Ternary Ⅰ-Ⅲ-Ⅵ quantum dots (QDs) have become promising color-conversion materials for warm white light-emitting diodes (WLEDs) because of their broad emission, large stokes shift, high luminescence and low-toxicity. In this work, AgInS 2 /ZnS (AIS/ZnS) core/shell QDs were synthesized via a facile microwave-assisted aqueous method. The PL emission can be tuned from 540 to 622 nm by varying the Ag/In ratio and the maximum quantum yield can reach 58.27%. Flexible luminescent films were obtained by embedding AIS/ZnS QDs in polyacrylamide hydrogel, which were combined with blue InGaN chips to fabricate remote-type warm WLEDs. The as-prepared LEDs exhibit a relatively high color rendering index (CRI) of 87.5 and a correlated color temperature (CCT) of 3669 K, indicating that water-soluble AIS/ZnS QDs are competitive color-conversion materials for warm WLEDs.
Xiaojiao Kang,Lijian Huang,Yanchun Yang,Daocheng Pan
Approximately 3 g of water-soluble AgInS2/ZnS core/shell quantum dots (AIS/ZnS QDs) with a maximum photoluminescence quantum yield of up to 39.1% was synthesized in an aqueous solution of gelatin and thioglycolic acid (TGA). The composition of the AIS QDs could be readily adjusted by controlling the molar ratio of the starting Ag/In precursors in the reaction solution, which leads to a tunable emission ranging from 535 to 607 nm. The as-prepared core/shell QDs exhibit excellent photostability and water/buffer stability. More importantly, these cadmium-free hydrophilic AIS/ZnS core/shell QDs are biocompatible and can be directly utilized in cancer cell imaging.
Indium-rich environmentally-friendly quantum dots (QDs) have received widespread attention due to the absence of cadmium. In this paper, AgInS2 (AIS) QDs are synthesized by hot injection method. By adjusting the ratio of indium/silver (In/Ag = 1, 2, 3, 4, 5), the AIS QDs exhibit a blue shift from 868 nm to 603 nm with the indium composition increases. Therein, the AIS QDs with the ratio of In/Ag = 4 show a highest photoluminescent (PL) quantum yields (QYs) up to 57%. AIS QDs are coated with ZnS shell to passivate the surface defects, and the PL QYs of obtained core/shell AIS/ZnS QDs is increased to 72%. By using these AIS/ZnS QDs as light emitters, light emitting diodes are assembled with a stacked multi-layer structure ITO/PEDOT:PSS/Poly-TPD/QDs/ZnO:Mg/Al. The resulted electroluminescent (EL) device exhibits a maximum external quantum efficiency (EQE) of 1.25% and an open circuit voltage of 4.6 V corresponding to a maximum brightness of 1120 cd m−2. Although the performances of the as fabricated AIS/ZnS-based device lag much behind than those of the Cd-based ones, they are expected to be enhanced with much more studies on the synthesis of the QDs and the optimization of device structure.
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