Chemically Designed Crystal Growth Termination for High-Luminance and Stable Polycrystalline Perovskite LEDs

Chemically synthesized colloidal metal halide perovskite (MHP) nanocrystals (NCs) have high luminous efficiency, but they have long-chain organic ligands bound perpendicularly to the surface, which impede charge injection and transport, thereby causing charge accumulation and consequent degradation. This work presents an in situ crystallization strategy for polycrystalline MHP light emitters by altering the surface chemistry of MHPs, followed by lateral surface capping with a linear ionic homopolymer. This strategy directs in situ crystal growth termination to achieve nanocuboid grains that have well-terminated surfaces, resulting in enhanced photophysical properties and electrical homogeneity. Consequently, light-emitting diodes with the surface-tailored light emitters exhibit high luminance (>150 000 cd m –2 ), high efficiency at elevated luminance (>102.1 cd A –1 at 100 000 cd m –2 ), low efficiency roll-off (0.58% reduction to emit 100 000 cd m –2 ), and long-term stability ( T 95 ≈ 243 h), simultaneously. This in situ crystallization combines the advantages of colloidal NCs and polycrystalline thin films while eliminating critical drawbacks of each approach.