Morphological Stabilization of CsPbBr 3 Quantum Dot Films Enabled by PVC ‐g‐ PMMA Graft Copolymer Encapsulation for Water‐Robust Color Conversion

ABSTRACT All‐inorganic CsPbBr 3 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 CsPbBr 3 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 CsPbBr 3 defects and confers solvent compatibility and PVC endows water and chemical resistance. CsPbBr 3 and CsPbBr 3 /PVC‐ g ‐PMMA achieve PL quantum yields of 16.32% and 50.64%, respectively. In water, PL intensity of CsPbBr 3 /PVC‐ g ‐PMMA is >60% of its initial intensity after 28 days, whereas that of CsPbBr 3 /PMMA is <20% after 7 days. Upon UV irradiation and water exposure, CsPbBr 3 /PVC‐ g ‐PMMA maintains >70% after 12 h. Upon ethanol exposure, CsPbBr 3 /PVC‐ g ‐PMMA and CsPbBr 3 /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 CsPbBr 3 /PVC‐ g ‐PMMA but increases to 0.81 for CsPbBr 3 /PMMA and CsPbBr 3 . 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.