Metal halide perovskites are attracting great attention as next-generation light emitting materials due to their excellent emission properties with narrowband emission. [1][2][3][4] However, perovskite light-emitting didoes (PeLEDs) irrespective of their material types (polycrystals or nanocrystals) have not realized high luminance, high efficiency and long lifetime simultaneously, as they are influenced by the intrinsic limitations related to the trade-off properties between charge transport and confinement in each type of perovskite materials. [5][6][7][8] Here, we report an ultra-bright, efficient, and stable PeLEDs made of core/shell perovskite nanocrystals with a size of ~10 nm obtained using simple in-situ reaction of benzylphosphonic acid (BPA) additive with 3D polycrystalline perovskite films without separate synthesis process. During the reaction, large 3D crystals are split into nanocrystals and the BPA surrounds the nanocrystals, achieving strong carrier confinement. The BPA shell passivates the undercoordinated lead atoms by forming covalent bonds, and thereby greatly reduces trap density while maintaining good charge-transport properties of 3D perovskites. We demonstrate simultaneously efficient, bright, and stable PeLEDs that have maximum brightness of ~470,000 cd m -2 , maximum external quantum efficiency of 28.9 % (average = 25.2 ± 1.6 % over 40 devices), maximum current efficiency of 151 cd A -1 , and half-lifetime of 520 h at 1,000 cd m -2 (estimated half-lifetime >30,000 h at 100 cd m -2 ). Our work sheds great light on the possibility that PeLEDs can be commercialized in the future display industry.

No abstract