Ultra‐Stable CsPbX₃@Pyrophosphate Nanoparticles in Water over One Year

Abstract All‐inorganic lead halide perovskite (CsPbX₃, X = Cl, Br, I, or their mixture) nanocrystals (NCs) have achieved inspiring advancements in optoelectronic fields but still suffer from poor durability when exposed to environmental stimuli such as water, irradiation and heat. Herein, a strategy of employing pyrophosphate as the inert shell for CsPbX₃ NCs is reported. The strong binding between pyrophosphate and CsPbBr₃ surface can stabilize the perovskite structure well. The as‐obtained core@shell CsPbBr₃@NH₄AlP₂O₇ NCs exhibit impressive stability against water and maintain the initial optical properties with negligible change in 400 days. Furthermore, significant improvement of irradiation/thermal resistance is realized due to the protecting role of pyrophosphate. The NCs can retain 100% and ≈90% of the original PL after hundreds of heating/cooling cycles and several hundred hours of UV light irradiation, respectively. As a result, the core@shell products can be directly used for high‐resolution inkjet printing, enabling the printed fluorescent information to be resistant under harsh environmental conditions. This work provides a promising way for the synthesis of highly stable encapsulated perovskite NCs and demonstrates a great potential in practical applications.