Efficient and Stable Blue Light Emitting Diodes Based on CsPbBr₃ Nanoplatelets with Surface Passivation by a Multifunctional Organic Sulfate

Abstract Metal halide perovskite nanocrystals (NCs) have emerged as highly promising light emitting materials for various applications, ranging from perovskite light‐emitting diodes (PeLEDs) to lasers and radiation detectors. While remarkable progress has been achieved in highly efficient and stable green, red, and infrared perovskite NCs, obtaining efficient and stable blue‐emitting perovskite NCs remains a great challenge. Here, a facile synthetic approach for the preparation of blue emitting CsPbBr₃ nanoplatelets (NPLs) with treatment by an organic sulfate is reported, 2,2‐(ethylenedioxy) bis(ethylammonium) sulfate (EDBESO₄), which exhibit remarkably enhanced photoluminescence quantum efficiency (PLQE) and stability as compared to pristine CsPbBr₃ NPLs coated with oleylamines. The PLQE is improved from ≈28% for pristine CsPbBr₃ NPLs to 85% for EDBESO₄ treated CsPbBr₃ NPLs. Detailed structural characterizations reveal that EDBESO₄ treatment leads to surface passivation of CsPbBr₃ NPLs by both EDBE²⁺ and SO₄^2– ions, which helps to prevent the coalescence of NPLs and suppress the degradation of NPLs. A simple proof‐of‐concept device with emission peaked at 462 nm exhibits an external quantum efficiency of 1.77% with a luminance of 691 cd m⁻² and a half‐lifetime of 20 min, which represents one of the brightest pure blue PeLEDs based on NPLs reported to date.