Preparation Of Aqueous CdTe Quantum Dots-based Nanocomposites And White Light-emitting Diodes Application

The ever-increasing demands of energy along with the concerns of global warming and climate change place an enormous emphasis on the exploration of high-efficiency light sources to reduce energy consumption. Energy efficient and environmentally friendly solid-state lighting, such as white light emitting diodes(WLEDs), due to its low power consumption, long life, good luminescent properties, environmental protection, etc. are considered to be the most promising and suitable light source.Most of the current commercial WLEDs, however, use the fluorescencent rare earth materials as color conversion. But the drawbacks of rare earth materials in performance and price have become increasingly prominent, which is currently a bottleneck to the development of the LED light source. In order to solve the above problems, the inventors of a new phosphor material which can be used as color conversion is of significant importance. The Quantum Dots(QDs) show overwhelming promise in meeting this challenge. Compared to the fluorescent rare earth materials, the QDs have strong, narrow and tuneable photoluminescence, good stability and multifunctionality, which could be used in the preparation of photoluminescence type of LED light source.Although semiconductor QDs shows overwhelming promiseusing as LED color conversion, but for the aqueous QDs, how to stabilize these QDs into a matrix is a crucial issue for their practical applications in solid-state devices. In this paper, we aim to explore the synthesis of nanocomposites based on aqueous QDs, to promote the application of the aqueous QDs in LEDs color conversion layer. This context includes two parts:(1) we successfully prepared CdTe QD–PU bulk nanocomposites through the reaction between –OH and –NCO. To achieve this goal, we solve two problems: One is TG-CdTe by traditional reflux method has worse photoluminescence(PL). The fluorescence quantum efficiency is too low, only about 3 %, limiting the applications of TG-stabilized QDs incorporated with polymers. We prepared TG-stabilized CdTe QDs with enhanced PL in water through a N2H4-promoted growth approach, which PLQY is up to 13%. The other is the incompatibility between the aqueous QDs and the PU prepolymer. Finally we get high light-emitting CdTe QD-PU nanocomposites by the introduction of dimethylsulfoxide(DMSO);(2) Highly luminescent nanocomposites are fabricated via intercalation CdTe QDs into a montmorillonite-Na+ clay matrix. The resulting CdTe-MMT nanocomposites display strong photoluminescence, high stability and controllable emission colors, which can be attributed to the uniform distribution of QDs within the layered matrix. Furthermore, not only the emission colors of the nanocomposites are tunable, but also the concentration of QDs in the nanocomposites as well as the type of QDs. That is to say, our method is of universality. The CdTe-MMT nanocomposites may be further processed by mixing them with poly(methyl methacrylate)(PMMA) to use as color conversion layers in commercial LEDs.