Highly stable deep-blue emitting CsPbBr3 nanoplatelets with modified zwitterionic surface passivation

•Stable deep-blue emitting CsPbBr3 NPLs have been successfully synthesized via the modified zwitterions passivation.•The CsPbBr3 NPLs-BOA/OLA yield PLQYs up to 98.53%.•The CsPbBr3 NPLs-BOA/OLA possess excellent stability under UV irradiation, long-term storage and heat treatment.•Deep-blue light emitting diode with CIE color coordinates of (0.14, 0.05). Two-dimensional CsPbBr3 nanoplatelets (NPLs) with narrow emission line width are one of the most promising materials for lighting and display applications. Nevertheless, it has been difficult to successfully synthesize deep-blue emitting CsPbBr3 NPLs with long-term stability and high photoluminescence quantum yield (PLQY), which prevents their widespread application in the field of lighting. The use of ligands engineering strategy has demonstrated an increase in the PLQY and stability. Herein, a method employing in situ formation of modified zwitterionic surface ligands is proposed to successfully synthesize high-quality CsPbBr3 NPLs. Zwitterionic passivation strategy can produce deep blue emission of CsPbBr3 NPLs at ∼ 461 nm, achieving a near-unity quantum yield and excellent stability for long-term storage at room-temperature, heat treatment, and ultraviolet irradiation. This enhancement can be attributed to the strong chelation between the modified zwitterions and the surface of CsPbBr3 NPLs, which can effectively immobilize surface halide ions and passivate surface defects. This work provides a flexible way to achieve high PLQY and improve the stability issues in perovskite NPLs.