Hydroxyl terminated mesoporous silica-assisted dispersion of ligand-free CsPbBr3/Cs4PbBr6 nanocrystals in polymer for stable white LED†
Composite nanocrystals of CsPbBr3/Cs4PbBr6 have gained significant attention because of their high stability and unique photoelectronic property. However, their dispersion within polymers is rather difficult due to the absence of ligands, which limits further enhancement of stability and practical applications. Herein, a feasible, effective, and general method was developed to assist the dispersion of CsPbBr3/Cs4PbBr6 nanocrystals in polymer by using –OH terminated mesoporous silica as a micro-container. The composite film obtained is employed as the light emitter for the fabrication of white LEDs. It was found that silica loaded with composite nanocrystals disperse uniformly in the composite film which shows excellent stability with a half-life of 400 hours under the illumination with optical power density of 1.7 × 103 mW cm−2 and peak wavelength of 457 nm. The inner pore of the micro-container attracts precursors and confines the crystallization, leading to the incorporation of CsPbBr3/Cs4PbBr6 nanocrystals. Meanwhile, the hydrogen bonding of the outer surface with poly(methyl methacrylate) (PMMA) enables good dispersion of the loaded micro-containers in PMMA as evidenced by the optical microscopy characterization and water resistance test. Moreover, this strategy can also be applied to other kinds of polymers since the outside –OH group can react with siliane coupling agents. On the basis of stability tests associated with silica and polymer encapsulation, a possible mechanism is proposed for the enhancement of the stability of composite films under working condition.