Stretchable, Tough, and Luminescent Perovskite Molecular Ferroelectric Composite: Empowering Reliable Self‐Powered Motion Sensing in High Humidity and Subzero Temperatures

Abstract Piezoelectric materials for wearable biomechanical sensing require high flexibility, including the mechanical capacity to endure stretching and bending deformations, etc. However, existing strategies for flexible composites embedding typically brittle piezoelectric crystals into polymer matrices still suffer from limited stretchability and mechanical strength, falling short of dynamic, all‐day wearable scenarios. Herein, we synthesize a new luminescent organic‐inorganic hybrid perovskite ferroelectric molecular crystal, N,N ‐dimethylallylammonium MnCl ₃ (DMAA‐MnCl ₃ ), which exhibits a transverse piezoelectric response of about 36 pC/N and a higher Curie temperature ( T _c = 357 K) than that of its Cd analog (Δ T = +18 K; Wang et al. J. Am. Chem. Soc . 2020, 142, 12857). By in situ growing DMAA‐MnCl ₃ microcrystals within a styrene‐ethylene‐butylene‐styrene/styrene‐isoprene‐styrene (SEBS/SIS) double‐polymer matrix, we fabricated a flexible ferroelectric composite SEBS/SIS/DMAA‐MnCl ₃ that delivers excellent mechanical properties (tensile strength up to 7.54 MPa, tensile strain > 1200%), strong red emission, and reliable piezoelectric sensing for motion monitoring over 10 000 cycles. Notably, it maintains stable sensing responses under harsh conditions such as high humidity (100% RH) and subzero temperatures (as low as −35°C), opening prospects for all‐weather environmental scenes. This work provides a practical design strategy for flexible ferroelectric composites with promising application prospects.