Triple Synergistic Stabilization in Zn: CsPbBrxI3–x-PVDF for High-Efficiency Pure Red Emission Films

Mixed halide perovskite CsPbBrxI3-x nanocrystal (NC) films exhibit viable application prospects in pure red perovskite light-emitting diodes (PeLEDs). However, intrinsic environmental instability, defects, and spectral instabilities are always present in pure red perovskites under mixing halide ion exchange processing. In this work, we developed a swelling method for the preparation of stable pure red light emission Zn: CsPbBrxI3-x-PVDF films by post-treatment with CsBr-ZnI2 at room temperature. In this system, PVDF-CsBr-ZnI2 presents triple synergistic effects to control anion exchange, stabilize the crystal structure, and passivate the defects of the red CsPbBrxI3-x-PVDF film, simultaneously. In addition, the Zn: CsPbBrxI3-x-PVDF films' photoluminescence emission can be precisely tuned from 665 to 580 nm with high spectral stability. More importantly, the as-prepared 637 nm emitting Zn: CsPbBrxI3-x-PVDF films present a full width at half-maximum (fwhm) as narrow as 50 nm with a high photoluminescence quantum yield (PLQY) of more than 47.27% after annealing. It was also demonstrated to serve as conversion layers for stable pure red LEDs, achieving the CIE Rec. 2020 standard and sustained electrical stability. The trinity of halide exchange, Zn passivation, and polymer encapsulation provides a novel strategy for obtaining high-quality perovskite lighting flexible thin films.