CsPbBr₃ Nanoplatelets via a Room-Temperature Postsynthetic Surface-Mediated Strategy for Blue Light-Emitting Diodes

All-inorganic blue-emissive CsPbBr 3 perovskite nanoplatelets (NPLs) are promising for optoelectronic applications due to excellent optical properties, but their applicability is seriously restricted by a low photoluminescence efficiency and poor stability. Here, we develop a postsynthetic surface-mediated engineering strategy to prepare high-quality blue CsPbBr 3 NPLs at room temperature by using strongly bound polystyrene sulfonic acid (PSS). PSS efficiently passivates the surface trap sites of NPLs via strong coordination bonds, thereby achieving high-efficiency exciton recombination and enhancing photostability. The optimized PSS-NPLs reveal intense blue emission with a central wavelength of ∼466 nm and a high photoluminescence quantum yield of ∼83.2%, indicating a substantial improvement from ∼48.3% of pristine NPLs. Simultaneously, the PSS-treated NPLs exhibit significantly enhanced stability in comparison with pristine NPLs during UV exposure and thermal treatment. Finally, we achieve efficient blue NPL-LEDs (peaked at ∼468 nm) using a PSS-NPL-polymer composite film, corresponding to CIE color coordinates of (0.124, 0.067), which closely approach to the Rec. 2020 blue standard. Hence, our work offers a facile strategy for fabricating high-performance perovskite NPLs and promotes their potential applications in blue-emitting optoelectronic devices.