Self‐Assembly of Completely Inorganic Perovskite Nanocrystals with Improved Stability by Anchoring on Kaolinite Lamellae

Abstract Completely inorganic lead halide perovskite (CsPbX₃, X = Cl, Br, I) nanocrystals (NCs) are attracting increasing attention due to their outstanding luminescent properties, but their inherently poor stability is a severe impediment to further practical applications. Here, a facile two‐step synthetic procedure for preparing highly stable CsPbX₃ NCs with the assistance of kaolinite lamellae (KL) is demonstrated. Systematic investigation shows that the cesium ions can be anchored tightly to the KL with the aid of strong Coulombic force interactions. These trigger the efficient growth of orthorhombic phase CsPbX₃ NCs on the KL surfaces in a highly ordered manner. As a benefit of the inhibited aggregation caused by isolation and the anchoring effect of KL, the CsPbBr₃‐KL composites display high luminescent efficiency (up to 73.0%) and excellent stability in air (>240 h). An efficient, stable, white light‐emitting diode device is fabricated by packaging green CsPbBr₃‐KL and red CsPb(Br_0.5I_0.5)₃‐KL composites on a blue GaN chip. These findings demonstrate the first attempt to improve the stability of CsPbX₃ NCs by designing composites with materials having natural layers. This should shed important light on the preparation of high‐efficiency, stable, and color‐tunable perovskite materials for applications requiring high‐performance devices.