Polymer Network Wrapping for Stable Pure-Blue PeLEDs

Achieving highly efficient and spectrally stable pure-blue emission remains one of the most critical challenges for the full-color implementation and commercialization of perovskite-based display technologies. Pure-blue perovskites intrinsically suffer from chloride vacancy defects, crystallization-induced morphological disorder, interfacial lattice strain, and severe halide ion migration, which collectively limit their radiative efficiency and spectral stability. Here, we introduce a polymer network wrapping strategy using poly(4-vinylphenol) (PVPh) to address these interrelated limitations. The PVPh network forms dual-site interactions with the perovskite surface, increasing the formation energy of halide vacancies and suppressing deep trap states. In addition, PVPh regulates crystallization to produce dense and pinhole-free films, mechanically relieves interfacial lattice strain, and confines halide migration under electrical bias. Supported by density functional theory calculations, structural analyses, and device-level diagnostics, this multifunctional strategy directly mitigates the intrinsic degradation pathways of pure-blue perovskites. As a result, the optimized PeLEDs achieve an external quantum efficiency of 9.82% and a maximum luminance of 1544 cd m⁻² at 467 nm, representing one of the highest performances reported for 3D-based pure-blue PeLEDs to date. This work establishes a simple and solution-process-compatible material design framework for stabilizing wide-bandgap perovskites and provides a promising route toward commercially viable pure-blue display technologies.