Efficient and Stable Blue Light Emitting Diodes Based on CsPbBr_3 Nanoplatelets with Surface Passivation by a Multifunctional Organic Sulfate

摘要

Metal halide perovskite nanocrystals (NCs) have emerged as highlypromising light emitting materials for various applications, ranging fromperovskite light-emitting diodes (PeLEDs) to lasers and radiation detectors.While remarkable progress has been achieved in highly efficient andstable green, red, and infrared perovskite NCs, obtaining efficient and stableblue-emitting perovskite NCs remains a great challenge. Here, a facile syntheticapproach 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 enhancedphotoluminescence quantum efficiency (PLQE) and stability as comparedto pristine CsPbBr_3 NPLs coated with oleylamines. The PLQE is improvedfrom ≈28% for pristine CsPbBr_3 NPLs to 85% for EDBESO_4 treated CsPbBr_3NPLs. Detailed structural characterizations reveal that EDBESO4 treatmentleads 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 degradationof NPLs. A simple proof-of-concept device with emission peaked at462 nm exhibits an external quantum efficiency of 1.77% with a luminanceof 691 cd m~(?2) and a half-lifetime of 20 min, which represents one of thebrightest pure blue PeLEDs based on NPLs reported to date.