Halide‐Tunable Bond Engineering for High‐Performance Multi‐Responsive Piezoelectric Sensors via Enhanced Electrostatic Polarization in In Situ Perovskite‐Embedded PVDF Nanofibers

Abstract Developing piezoelectric materials with substantial strain output and large voltage constant, alongside superior piezoelectric performance and mechanical softness remains a long‐standing challenge for promising practical applications. Herein, an in‐situ fabrication strategy is demonstrated to resolve these obstacles by engineering molecular bond angle/length and simultaneously improving electrostatic polarization domain in self‐aligned halide perovskite nanorods (NRs) embedded polyvinylidene fluoride (PVDF) nanofibers (NFs). Introducing large‐size iodine into CsPbBr 3 crystals weakens metal‐halide bonds in CsPbI 2 Br, softening bond strength and enhancing electrostatic polarization in PVDF. The optimized CsPbI 2 Br/PVDF NFs membrane achieves exceptional piezoelectric performance, with a high piezoelectric coefficient ( d 33 ) of 67.5 pC N −1 and a piezoelectric figure of merit of 10.7 × 10 −12 m 2 N −1 , representing 562% and 443% enhancements over the pure PVDF NFs membrane, respectively. Simultaneously, it offers superior mechanical softness, exhibiting a Young's modulus of ≈208 MPa and a strain up to 91.5%. Density functional theory is employed to predict the halide‐tunable latice distortion, which is responsible for the enhanced piezoelectricity. Furthermore, the fabricated sensor demonstrates excellent stability (≈10 000 cycles), detects various mechanical deformations, and powers multiple commercial LEDs through simple daily human activities, highlighting its strong potential as a high‐performance, portable, and wearable energy harvesting device.