Fluoride Ion Passivation of CsPbBr₃ Nanocrystals at Room Temperature for Highly Efficient and Stable White Light-Emitting Diodes

Inorganic halide perovskite nanocrystals (NCs) are regarded as promising emitters for light-emitting diodes due to their bright and narrow emission. However, surface defects often result in trap states and ion migration, which remains a huge challenge for high-quality perovskite NCs. Herein, fluoride ions are introduced into CsPbBr₃ perovskite NCs at room temperature through the chelation of ligands. Experimental results demonstrate that these fluoride ions from inorganic salts can improve the average lifetime and crystallinity of CsPbBr₃ NCs. Meanwhile, the resulting photoluminescence quantum yield is optimized up to 99.02%, and it has high stability to water, heat, and ultraviolet light. Density functional theory calculations show that fluoride ions have a higher binding energy compared to other ligands, which not only removes the electron trapping center but also increases the halogen ion migration energy. By mixing green-emission CsPbBr₃ NCs and red-emission K₂SiF₆:Mn⁴⁺ phosphors on a blue chip, the fabricated white light emitting diode shows a high luminous efficiency of 147.8 lm/W, a wide color gamut (129% for NTSC), and CIE coordinates of (0.3160, 0.3051). Furthermore, the photoluminescence intensity decreased by only 2.9% after 48 h of continuous operation.