The surface modification of metal halide perovskite nanocrystals (NCs) significantly impacts their optical properties and colloidal stability. This subsequently affects the performance of light-emitting devices (LEDs). Therefore, numerous surface passivation techniques like ligand exchange and metal halide doping have been explored to passivate the surface defects of perovskite NCs and obtain highly efficient LEDs. In this study, we demonstrated the postsynthetic metal halide doping treatment using lead(II) bromide (PbBr2) to passivate the surface defects of the CsPbBr3 NCs at a moderate reaction temperature of 80 °C. The alkyl quaternary ammonium salt, didodecyldimethylammonium bromide (DC12AB), enabled the complete dissolution of PbBr2 in a nonpolar solvent, toluene. Because of surface crystal growth, the particle sizes of the PbBr2-doped CsPbBr3 NCs were higher than those of the as-synthesized CsPbBr3 NCs. The photoluminescence quantum yield of the CsPbBr3 NCs drastically increased from 26.8 to 83.9% after the PbBr2 doping treatment. Moreover, the PbBr2-doped CsPbBr3 NCs possessed long-term colloidal stability of more than 2 months that indicates the strong bonding between the NCs and ligands. We observed that the alkyl chain length of the quaternary alkyl ammonium salts affected the luminance and device stability during operations. In this study, a promising strategy was devised to achieve highly luminescent perovskite NCs with excellent colloidal stability that can enhance the performance of LEDs.
Keywords: PbBr2 doping treatment; alkyl quaternary ammonium bromide; light-emitting devices; nanocrystals; perovskite.