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

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.