Despite remarkable progress in sky-blue perovskite light-emitting diodes (PeLEDs), achieving efficient and color stable pure-blue electroluminescence remains challenging due to halide phase segregation, low-dimensional phase-induced non-radiative recombination, and defect-related losses in mixed Cl-Br quasi-2D perovskites. Here, we propose a dual-additive strategy to regulate phase distribution and manage Cl incorporation in quasi-2D perovskites for pure-blue PeLEDs. By introducing EDACl2 to suppress high-n phases and incorporate Cl for bandgap broadening, combined with NaBr to eliminate low-n non-radiative centers and promote small-sized nanocrystals, we optimize radiative recombination toward wide-bandgap phase distribution. This approach enables spectrally stable pure-blue electroluminescence at 474 nm without compromising photoluminescence quantum yield. Further hole-transport-layer engineering yields a peak external quantum efficiency of 4.6%, with spectral stability maintained under extreme bias up to 10.4 V. Our work provides critical insights into phase and halide management for high-performance blue PeLEDs, advancing their potential in full-color displays and lighting technologies.
Owing to outstanding optoelectronic properties, lead halide perovskite nanocrystals (PNCs) are considered promising emitters for next-generation displays. However, the development of pure blue (460-470 nm) perovskite nanocrystal light-emitting diodes (PNC-LEDs), which correspond to the requirements of Rec. 2020 standard, lag far behind that of their green and red counterparts. Here, pure blue CsPb(Br/Cl) 3 nanocrystals with remarkable optical performance are demonstrated by a facile fluorine passivation strategy. Prominently, the fluorine passivation on halide vacancies and strong bonding of Pb–F intensely enhance crystal structure stability and inhibit “particle talking” behaviors under both thermal and electrical conditions. Fluorine-based PNCs with high resistance of luminescence thermal quenching retain 70% of photoluminescent intensity when heated to 343 K, which can be attributed to the elevated activation energy for carrier trapping and unchanged grain size. Fluorine-based PNC-LEDs also exhibit stable pure blue electroluminescence (EL) emission with sevenfold promoted luminance and external quantum efficiencies (EQEs), where the suppression of ion migration is further evidenced by a lateral structure device with applied polarizing potential.
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