In Situ Crystallized Nanocuboid Perovskite Light Emitters for High-luminance Light-emitting Devices

Metal halide perovskites (MHPs) have been regarded as highly promising light-emitting materials due to their excellent color purity, adjustable bandgap energy, and ability to be processed from solutions, making them suitable for cost-effective display technologies. However, solution-processed polycrystalline perovskite thin films possess numerous charged defects at the grain boundaries and surfaces. The charged defects create convenient pathways for ion migration, which hastens the deterioration of materials and devices during operation. In this work, we introduce a chemically designed novel in-situ fabrication strategy that forms highly luminous and stable nanocuboid-shaped perovskite crystals in polycrystalline thin films. The in-situ crystallization process is effectively controlled to achieve low defect density and nanosized cubic perovskite crystals by managing crystal growth termination during the formation of the perovskite thin film. The light-emitting diodes that use the <i>in-situ</i> fabricated perovskite nanocube thin films as an emitting layer exhibit high luminance (&gt;100,000 cd/m²), high luminous efficiencies at high luminance, and unparalleled operational stability compared with those of conventionally used MHP light emitter thin film.