Halogen-Bonding-Assisted Synthesis of CsPbI₃ Perovskite Nanocrystal Emission Materials for Stable and Efficient Pure-Red LEDs

Perovskite nanocrystals (NCs) demonstrate exceptional potential as emitters to address Rec. 2020 standards for wide color gamut displays. However, the pure-red-targeted CsPbI₃ NCs generally suffer from imprecise synthetic control over emission wavelength and from structural instabilities that significantly diminish performance. We report a novel halogen engineering framework that addresses the otherwise unfavorable wavelength-efficiency-stability nexus. Our approach leverages surface I^-···I₂ interactions to simultaneously unlock exceptional optical characteristics and the elusive structural robustness needed for application. It achieves: (i) controlled quantum-confinement-tuned emission wavelength, (ii) near-unity photoluminescence (PL) quantum yield through iodide vacancy defect management, and (iii) excellent environmental stability, even under harsh (85°C/85%) temperature and humidity conditions, through lattice-distortion suppression. Rec. 2020 compliant, 638 nm peak light-emitting diodes (LEDs) are then demonstrated with Commission Internationale de l'Éclairage coordinates (X, Y) = (0.703, 0.297), 22% external quantum efficiency, luminance ≥ 11,000 cd m^-2, and long lifetime, establishing a materials-by-design paradigm for advancing next-generation perovskite display technologies.