Stability Improvement of 2D Perovskite by Fluorinated‐Insulator

Abstract In this study, the interface of 2D hybrid organic–inorganic perovskites L₂PbI₄ (here L stands for phenylethylamine, PEA) is engineered by fluorine substitution in its organic insulator layers, and the stability of the perovskite is investigated. For the water‐resistance, the fluorinated‐perovskite maintained 90% photoluminescence intensity of its initial state after 800‐h exposure to relative humidity 75–80%, while it is 47% for that without fluorine, resulting from hydrophobic property of fluorinated insulator. As for the resistance to light illumination, the stability of the fluorinated perovskite is effectively improved for exposure to both continuous‐wave laser and UV lamp, due to chemical and thermal inertness. Furthermore, the effectiveness by the fluorinated‐insulator in combination with polymer encapsulation is also verified. However, the substitution of fluorinated‐insulator (F‐PEA) results more overlap of absorption and photoluminescence, and produces more defects, both of which would lead to the reduction of the photoluminescence quantum yield. This interfacial modification still paves a new way to improve the stability of 2D perovskites by using fluorinated‐insulator and provides new insight to move forward their applications.