Enhancement of luminescence and stability of CsPbBr3 quantum dots and their related light-emitting diodes through passivation by guanidine bromide

All-inorganic perovskite CsPbX₃ (X = Cl, Br, I) quantum dots (QDs) have attracted considerable attention in the fields of light-emitting diodes (LEDs) and displays owing to their excellent photoelectric properties. However, the intrinsic defects and poor stability in QDs limit their practical application. In order to address these problems, this study introduced guanidine bromide (GABr) as modifying agent during the synthesis of CsPbBr₃ QDs using the ligand-assisted reprecipitation method. From XRD and TEM studies, the introduction of GABr effectively enhances the crystallinity and adjusts the morphology of QDs without altering the crystal structure. The XPS and FTIR results revealed that the GA group not only fills the halogen vacancy defects by replacing part of the long-chain organic ligand Octanoic acid (OTAc), but also effectively passivate the unsaturated Pb forming a stable CsPbBr₃ QD with tri-ligand and optimized optical property and stability. As the confirmation of the passivation effects, the perovskite LEDs (PeLEDs) devices with CsPbBr₃ QDs as emission layers (EMLs) were fabricated and the maximum EQE and luminance for the passivated EML are nearly two times higher than that of primeval CsPbBr₃ QDs devices, and the spectral stability of electroluminescence is obviously enhanced. This work provides a straightforward passivation strategy for preparing efficient and stable CsPbBr₃ QDs and related optoelectronic devices.