Functional branched group design of a ligand to improve the stability of CsPbBr3 quantum dots for phosphor-converted applications

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Boosting the efficiency and lifetime of all inorganic metal halide perovskite nanocrystals (PeNCs) based light‐emitting diodes (PeLEDs) will promote the application of PeNCs in displays and lighting. However, achieving high‐stability CsPbBr3 NCs is still a critical challenge. In this study, a physical adsorption of polymethylmethacrylate (PMMA) on the surface of CsPbBr3 NCs is proven effective to enhance CsPbBr3 NCs stability by reducing the surface energy and preventing the attack of water and oxygen molecules. It also alleviates the energy transfer between neighboring NCs and greatly reduces the thin film roughness by suppressing the agglomeration of the CsPbBr3 NCs within films. Specifically, compared with CsPbBr3 NCs without PMMA adsorption, the photostability under the illumination of continuous ultraviolet light (96 hours) and storage stability under 0 °C (60 days) of the proposed CsPbBr3 NCs with PMMA adsorption are therefore improved by >10 times and four times, respectively. Moreover, since the energy transfer between CsPbBr3 NCs and the agglomeration of CsPbBr3 NCs within films have been suppressed dramatically by the physical absorbed PMMA, the maximum luminance of as‐fabricated LED devices is promoted from 5000 to 13,800 cd m−2 with alleviated roll‐off effect. The operational lifetime of the LED devices is also improved by 5.7 times owing to PMMA preventing the attack of water and oxygen molecules.

A series of microencapsulated phase‐change materials (micro‐PCMs) with binary cores and acrylate‐based copolymer shells were prepared. The micro‐PCMs contained octadecane and butyl stearate as binary‐core materials. Allyl methacrylate, ethylene glycol dimethacrylate, 1,4‐butanediol diacrylate (BDDA), and 1,6‐hexanediol dimethacrylate were respectively introduced to copolymerize with divinylbenzene (DVB) to form different microcapsule shells. In this work, the influence of the types of core and shell materials and core–shell weight ratios on the thermal properties of micro‐PCMs was studied. The chemical structures, morphologies, thermal properties, and thermal insulation properties of the wallboards were all tested and discussed. Scanning electron microscope photographs show that these micro‐PCMs have relatively spherical profiles and compact surfaces with diameters ranging from 10 to 80 μm. Differential scanning calorimetry results indicated that their microencapsulation efficiency ranged from 48 wt % to 80 wt %. A thermogravimetric analysis demonstrated that these micro‐PCMs can ensure their thermal stability below 210°C. Finally, a thermal insulation wallboard fabricated with synthesized P(BDDA‐co‐DVB) micro‐PCMs showed excellent thermal energy storage performance, keeping the temperature fluctuation within 2.5°C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47777.

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