High Quality CsPbI3−xBrx Thin Films Enabled by Synergetic Regulation of Fluorine Polymers and Amino Acid Molecules for Efficient Pure Red Light Emitting Diodes

All-inorganic CsPbX 3 (X = Cl, Br, or I) perovskite thin films are attractive emissive layers for high-performance light-emitting diodes (LEDs) due to their precisely tunable bandgaps, excellent color purities, good stabilities, and solution processabilities. However, the fabrication of high-quality CsPbI 3− x Br x thin films is very challenging because the crystal growth of mixed halide CsPbI 3− x Br x is in low controllability. Herein, a synergetic regulation strategy using fluorine polymer (Poly(vinylidene fluoride-co-hexafluoropropylene)) and a small amino acid molecule (L-Arginine) is developed to fabricate high-quality CsPbI 3− x Br x thin films for efficient pure red perovskite LEDs. In the fabricated CsPbI 3− x Br x thin film, the fluorine polymer plays a crucial role in confining CsPbI 3− x Br x crystal size at the nanoscale and the small amino acid molecule acts as a passivation agent to reduce the trap-state density. Under this synergetic effect, a uniform CsPbI 3− x Br x thin film with a high photoluminescence quantum yield up to 40% can be obtained to fabricate an efficient pure red perovskite LED with a maximum external quantum efficiency of 4.5% and a maximum brightness of 3100 cd m −2 . The reported synergistic regulation strategy will open a new avenue to fabricate efficient pure color CsPbX 3 perovskite LEDs.