Tunable Luminescence and Enhanced Polar Solvent Resistance of Perovskite Nanocrystals Achieved by Surface-Initiated Photopolymerization.

Colloidal lead halide perovskite nanocrystals (PNCs) have demonstrated great potential as materials of light-emitting diodes if their colloidal and compositional instability could be addressed. Herein, we reported a facile surface-initiated photopolymerization method that introduced polymers on a CsPbBr PNC surface to achieve improved stability and regulated halide exchange of PNCs in polar solvents. Synthetic polymers grafted from the surface of an individual PNC surface stabilized the PNCs, in which the multidentate linkage initiators and the extending polymers were two essential factors. The polymer-grafted PNCs showed composition-dependent colloidal dispersity and structural stability in various polar organic solvents and aqueous condition. It was found that changing the polarity of dispersing solvents effectively switched the swelling and collapsed states of surface polymers on the PNC-polymer nanoparticles, which provided an on-off mechanism to regulate the permeation of halide anions into the PNC cores. Thus, halide exchange of polymer-grafted PNCs in a good solvent for polymers varied the composition of PNCs and their emissive color, while switching the nanoparticles into a poor solvent, for example, ethanol and water, collapsed the surface polymer, prohibited the halide exchange, and consequently retained the color stability. It was demonstrated that different CsPbX PNCs with collapsed surface polymers could coexist into one solvent medium, achieving simultaneous emission with a white display. We believe this work provided insights into the rational functionalization of PNC materials using well-defined synthetic polymers toward tunable emission and outstanding stability in polar media.