Ionic liquid assisted preparation and modulation photoluminescence kinetics for high efficient CsPbX3 nanocrystals with improved stability
CsPbX3 (X=Cl, Br, I) nanocrystals (NCs) are competitive fluorescent materials for lighting and display owing to their excellent photophysical properties. However, the stability and optoelectronic performance of perovskite NCs are severely limited by the highly dynamic binding feature of present ligand strategy. Herein, a facile approach was performed to synthesize CsPbBr3 NCs with the assistance of ionic liquid (IL) 1-butyl-3-methylimidazolium bromide ([Bmim]Br). By strictly controlling the addition dose of [Bmim]Br (nIL/nPb=0.125) into the reaction precursor, it is possible to obtain desired cube-shaped and monodispersed CsPbBr3 NCs with simultaneous enhancement of the storage and irradiation stability as well as photoluminescence quantum yields (PLQYs, ~91%). Stability tests show that the parent CsPbBr3 NCs drop to 50% of its initial emission intensity after storage in atmosphere for 91 days, while the sample prepared with the assistance of [Bmim]Br can maintain 82% of PL intensity. Meanwhile, the modified CsPbBr3 NCs also present superior photo-stability, which still keeps 81% of original PL intensity after continuous illumination under ultraviolet lamp for 24 h, but the parent CsPbBr3 NCs reduce to 35% of the original intensity. Through the morphology, composition, luminescence kinetics evolution of CsPbBr3 NCs, these benefits were attributed to the modulation by [Bmim]Br, which could effective compensate the Br ions for the formation and growth of NCs, resulting in the reduction of surface traps. Moreover, [Bmim]Br exhibited strong interaction with NCs, and the deprotonation of oleic acid (OA) was inhibited, resulting in the effective passivation of surface defects. Finally, the CsPbX3 NCs with different composition were obtained via a facile anion exchange reaction, leading to the tunable emission in the range of 462~665 nm and wide colour gamut (129.65% NTSC standard). This work opens a new avenue for modulating the surface property of CsPbX3 NCs, which will create opportunities for the application in photoelectric field.