Hexamethylene Diisocyanate-Modulated Mixed-Halide Perovskite Enables Efficient and Stable Blue Light-Emitting Diodes

Perovskite light-emitting diodes (PeLEDs) have emerged as promising candidates for next-generation displays, yet blue PeLEDs significantly lag behind their green/red counterparts. The inferior performance of blue PeLEDs arises from two principal challenges: trap-assisted nonradiative recombination and halide ion migration. Herein, we introduce a multifunctional additive strategy utilizing hexamethylene diisocyanate (HDI) to synergistically address these limitations in blue mixed-halide PeLEDs. The N═C═O functional group in HDI demonstrates dual functionality: (1) selective coordination with the unsaturated lead sites effectively passivates defects while filling halide vacancies, and (2) reduced halide vacancy suppresses ion migration and ultimately achieves stabilization of the perovskite lattice. This approach obtained blue perovskite films with an enhanced photoluminescence quantum yield (PLQY) and reduced defect density. Comprehensive capacitance-voltage characterization reveals that HDI-optimized blue PeLEDs exhibit enhanced carrier transport efficiency and suppressed interface carrier accumulation. Resulting blue PeLEDs achieve a peak external quantum efficiency of 9.56% and a stable electroluminescence peak at 488 nm, demonstrating a maximum luminance of 3321 cd m^-2. This work establishes an effective strategy for high-quality blue PeLEDs, accelerating advancement toward the practical implementation of high-performance blue PeLEDs.