Highly Stable Amine-Free CsPbBr₃ Perovskite Nanocrystals for Perovskite-Based Display Applications

Abstract

Colloidally synthesized cesium lead halide (CsPbX3; X = Cl, Br, and I) perovskite nanocrystals (PNCs) often suffer from poor ambient and environmental stability conditions, limiting their practical applications. The commonly used surfactant oleylamine is converted to the oleylammonium cation, which pulls out the halide anion from the PNC surface, thus disrupting the structural integrity and stability of the nanocrystal. We developed a simple, completely amine-free colloidal synthesis with a hot injection method under open-atmospheric conditions and introduced bromooctane as a bromine precursor to overcome the above issues. These as-synthesized amine-free PNCs show a photoluminescence quantum yield (PLQY) of around 60%, and the size of PNCs is ∼25 nm. Moreover, these amine-free PNCs were highly stable in colloidal solutions and thin films for more than 5 months under ambient conditions, with 66% of their initial PLQY. In addition, these PNCs show exceptional stability under different environmental conditions, with 44% of the initial PL even after water treatment under 6 h and 28% of the initial PL under ethanol treatment of 120 min. Furthermore, they exhibit excellent photostability for 96 h and retain 36% of their initial PL under ceaseless UV light irradiation at 365 nm (8 W/cm2). In addition, these PNCs have good stability upon heat treatment and maintain 34% of the initial PL upon heating up to 90 °C. Finally, we fabricated a green-emitting down-conversion light-emitting diode (LED) using these amine-free PNCs. Therefore, we envision that these amine-free CsPbBr3 PNCs are perhaps ideal candidates for perovskite-based display applications.