Efficient and stable blue light emitting diodes based on CsPbBr${}_3$ nanoplatelets with surface passivation by a multifunctional organic sulfate

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 CsPbBr${}_3$ nanoplatelets (NPLs) with treatment by an organic sulfate is reported, 2,2-(ethylenedioxy) bis(ethylammonium) sulfate (EDBESO${}_4$), which exhibit remarkably enhanced photoluminescence quantum efficiency (PLQE) and stability as compared to pristine CsPbBr${}_3$ NPLs coated with oleylamines. The PLQE is improved from ≈28% for pristine CsPbBr${}_3$ NPLs to 85% for EDBESO${}_4$ treated CsPbBr${}_3$ NPLs. Detailed structural characterizations reveal that EDBESO${}_4$ treatment leads to surface passivation of CsPbBr${}_3$ NPLs by both EDBE${}^{2+}$ and SO${}_4$${}^{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. (© 2022 Wiley‐VCH GmbH)