Polymer Network Modified Perovskite for High‐Performance Pure Blue Light‐Emitting Diodes

ABSTRACT Achieving highly efficient and spectrally stable pure‐blue perovskite emission remains the most critical outstanding challenge for completing the full‐color implementation and commercialization of perovskite‐based display technologies. Pure blue perovskites inherently suffer from chloride vacancy defects, crystallization‐induced morphological disorder, interfacial lattice strain, and pronounced halide ion migration, all of which collectively limit their radiative efficiency and spectral stability. Here, we introduce a polymer network wrapping strategy using poly(4‐vinylphenol) (PVPh) that provides an integrated solution to these tightly coupled limitations. The PVPh network forms dual‐site interactions with the perovskite surface, increasing halide vacancy formation energies and suppressing deep trap states; regulates crystallization to form dense, pinhole‐free films; mechanically relaxes interfacial lattice strain; and confines halide migration under electrical bias. Supported by combined DFT calculations, structural analyses, and device‐level diagnostics, this multifunctional approach directly addresses the intrinsic instability pathways of pure‐blue perovskites. As a result, the optimized PeLEDs deliver a record‐high external quantum efficiency of 9.82%, a maximum luminance of 1544 cd m − 2 at 467 nm, representing the highest performance reported for 3D‐based pure‐blue PeLEDs to date. This work establishes a simple, solution‐process‐compatible material design framework for stabilizing wide‐bandgap perovskites and offers a promising pathway toward commercially viable pure‐blue display technologies.