Methylammonium (MA) lead halide (MAPbX3, X = Cl, Br, I) perovskite quantum dots (PQDs) are very sensitive to environment (moisture, oxygen, and temperature), suffering from poor stability. To improve the stability, we synthesized silica-coated PQDs (SPQDs) by an improved ligand-assisted reprecipitation method through simply mixing and stirring under room temperature in air without adding water and catalyst, the whole process took only a few seconds. The photoluminescence (PL) spectra of the SPQDs can be tuned continuously from 460 to 662 nm via adjusting the composition proportion of precursors. The highest PL quantum yields (PLQYs) of blue-, green-, and red-emissive SPQDs are 56, 95, and 70%, respectively. The SPQDs show remarkably improved environmental and thermal stability compared to the naked PQDs because of effective barrier created by the coated silica between the core materials and the ambience. Furthermore, it is found that different light-emitting SPQDs can maintain their original PL properties after mixing of them and anion-exchange reactions have not happened. These attributes were then used to mix green- and yellow-emissive SPQDs with polystyrene (PS) to form color-converting layers for the fabrication of white light-emitting devices (WLEDs). The WLEDs exhibit excellent white light characteristics with CIE 1931 color coordinates of (0.31, 0.34) and color rendering index (CRI) of 85, demonstrating promising applications of SPQDs in lighting and displays.
Keywords: anion-exchange reaction; hydrolysis; silane; silica-coated perovskite quantum dots; stability.