Air‐Fabrication Perovskite Supercrystal Film Enabled by a Strategy of Nontoxic Calcium Ion Confinement for Bright and Stable Light‐Emitting Diodes

Metal halide perovskites have garnered significant attention in the application of light-emitting diodes (LEDs) due to their excellent optoelectronic properties. However, the traditional solution preparation of perovskite emissive layers (EMLs) is performed in inert atmosphere, which is not economical for mass production. Herein, a calcium ion (Ca²⁺) confinement (CIC) strategy is proposed to fabricate high-quality perovskite films with in situ formed supercrystal in air atmosphere. It is found that the incorporation of substantial Ca²⁺ into perovskite precursors induces self-aggregates of perovskite nanoparticles with strong exciton localization effect and reduce density of trap states, prolonging the photoluminescence lifetime of the air-fabrication perovskite films from nanoseconds to microseconds. Based on this CIC strategy, the air-fabrication supercrystal EMLs present a large enhancement of photoluminescence quantum yields, and the resultant perovskite LEDs (PeLEDs) achieve significantly improved performance with a maximum luminance of approaching 100,000 cd m^-2, setting the record luminance for the air-fabrication PeLEDs. Moreover, the massive Ca²⁺ reduces the toxicity of the perovskite EMLs and increases the operation lifetime of the air-fabrication PeLEDs. This work not only addresses the film-forming challenges of perovskite supercrystal films but also provides a cost-effective and low-toxicity solution-fabrication strategy for fabricating high-performance PeLEDs in air atmosphere.