Multifunctional Crystal Regulation Enables Efficient and Stable Sky‐Blue Perovskite Light‐Emitting Diodes

Perovskite light‐emitting didoes (PeLEDs) have shown considerable potential in solution‐processable display applications. However, the performance of blue PeLEDs in terms of efficiency and stability hinders their practicality on account of severe trap‐mediated nonradiative recombination losses and halide phase segregation. To ameliorate these issues, mixed‐halide sky‐blue perovskite materials are strategically modulated through crystal defect passivation with a trifurcate isocyanate oligomer, which leads to the synergistical suppression of charge trap density and halide ion migration. The proposed approach enables the performance improvement for sky‐blue PeLEDs, exhibiting a peak external quantum efficiency of 14.82% and spectrally stable emission at 487 nm. In addition, prolonged operational lifetime and enhanced capability of moisture resistance are achieved simultaneously, approaching a half‐lifetime of ≈2900 s at an initial brightness of 178 cd m–2. A trifurcate isocyanate oligomer is proposed for modulating mixed‐halide sky‐blue perovskite materials by passivating crystal defects, suppressing halide ion migration, and resisting moisture simultaneously. Sky‐blue perovskite light‐emitting diodes achieve a high external quantum efficiency of 14.82% and distinctly improved operational stability with a half‐lifetime of ≈3000 s.