Improved Formation of Polar Phase in P(VDF‐TrFE) Through Adding Piezoelectric Metal Halide TMCM‐CdBrCl ₂

ABSTRACT Piezoelectric fluoropolymers, known for their electromechanical conversion capabilities, hold significant promise for sustainably powering energy harvesters and sensors. However, their widespread application is constrained by inherently low piezoelectric performance originating from the restricted content of polar β ‐phase. Here, we report TMCM‐CdBrCl ₂ /P(VDF‐TrFE) composite nanofibers prepared via an in‐situ growth strategy, in which the piezoelectric metal halide TMCM‐CdBrCl ₂ is uniformly incorporated into the ferroelectric polymer matrix (TMCM = trimethyl chloromethyl ammonium, P(VDF‐TrFE) = polyvinylidene fluoride‐trifluoroethylene). The ordered arrangement of TMCM‐CdBrCl ₂ provides directional polar interfaces that guide P(VDF‐TrFE) chain alignment, thereby facilitating β ‐phase formation. The resulting composite film exhibits a significantly enhanced electromechanical response, achieving a high‐power density of 60.2 µW cm ⁻² for energy harvesting and a sensitivity of 14.32 V kPa ⁻¹ for pressure sensing. Furthermore, the composite devices exhibit prominent capability for detecting ultrasonic waves in underwater environments. This work provides a promising pathway for the development of high‐performance piezoelectric fluoropolymer composites suitable for wearable and flexible electronic devices.