Pressure-Induced Ultrawidely Tunable and Ultrapure Photoluminescence in 2D Perovskites via Fluorination of Organic Cations

Alternating organic and inorganic layers of two-dimensional (2D) perovskites provide a feasible route for extending their emission range through external pressure. However, lattice distortion of inorganic layers under pressure significantly impedes narrow-band emission. Herein, we report a simple approach through fluorination of organic cations in 2D (PEA)2PbI4 to improve structural rigidity and sustain tunable narrow-band emission. Most importantly, (4-FPEA)2PbI4 exhibits ultrapure photoluminescence emission with a spectral width of 14–21 nm and an ultrawide tunability range from 520 to 695 nm with excellent linearity and reversibility upon compression to 7 GPa. Our findings demonstrate that fluorine substitution on the para position of the phenyl group in (4-FPEA)2PbI4 can promote the parallel stacking alignment of PEA molecules and enhance the interactions between spacer cations, which maximally release the compression to the inorganic framework under compression. This work could open new pathways for developing 2D perovskites with ultrawide wavelength tuning and high color purity for display applications.