Fluoride Ion Passivation of CsPbBr 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 CsPbBr 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 CsPbBr 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 CsPbBr NCs and red-emission KSiF:Mn 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.