• • Weakly space-confined CsPbBr3 films exhibit monocrystalline domains exceeding hundreds of nanometers with no observable grain boundaries, reducing defect density and ion migration pathways, which is critical for achieving high EQE and operational stability in PeLEDs.
• • The use of sacrificial additives HPA and NH4Cl induces controlled nucleation and crystallization, yielding highly oriented films that suppress ion vacancies and lattice distortions, thereby improving carrier mobility and elevating the ion migration energy barrier.
• • Compared to strongly confined systems (~20 nm crystallites with amorphous organic-rich regions), weakly confined perovskites minimize Auger recombination and ion migration, directly addressing EQE roll-off and limited stability that plague conventional PeLEDs.
• • The strategy achieves record-breaking performance in all-inorganic CsPbBr3 PeLEDs, demonstrating a promising route to overcome the limitations of strong confinement and accelerate practical applications in high-brightness displays and lighting.