Morphological Stabilization of CsPbBr3 Quantum Dot Films Enabled by PVC-g-PMMA Graft Copolymer Encapsulation for Water-Robust Color Conversion.

All-inorganic CsPbBr3 perovskite quantum dots are color-conversion emitters for display and lighting applications because of their high color purity and solution-processability. However, their application remains limited by poor water stability and photoluminescence (PL) degradation. Herein, water-stable CsPbBr3 quantum dot-polymer composite films are prepared from a morphology-stabilizing copolymer, poly(vinyl chloride)-graft-poly(methyl methacrylate) (PVC-g-PMMA), where PMMA provides carbonyl-mediated passivation of CsPbBr3 defects and confers solvent compatibility and PVC endows water and chemical resistance. CsPbBr3 and CsPbBr3/PVC-g-PMMA achieve PL quantum yields of 16.32% and 50.64%, respectively. In water, PL intensity of CsPbBr3/PVC-g-PMMA is >60% of its initial intensity after 28 days, whereas that of CsPbBr3/PMMA is <20% after 7 days. Upon UV irradiation and water exposure, CsPbBr3/PVC-g-PMMA maintains >70% after 12 h. Upon ethanol exposure, CsPbBr3/PVC-g-PMMA and CsPbBr3/PMMA retain >90% and <10%, respectively, after 4 h. Time-dependent ex situ transmission electron microscopy with particle segmentation reveals suppressed particle coalescence and preserved particle-size uniformity. The coefficient of variation of the maximum Feret diameter remains ∼0.25-0.27 for CsPbBr3/PVC-g-PMMA but increases to 0.81 for CsPbBr3/PMMA and CsPbBr3. Leave-one-out cross-validation indicates that this coefficient explains PL-intensity variations. In situ liquid atomic force microscopy reveals persistent regions with relatively high apparent local stiffness under hydration, indicating mechanical constraint.