Temperature-Insensitive Ferroelectric Polymer Film for Electrocaloric Refrigeration

Electrocaloric (EC) polymer materials are among the most promising candidates used in solid-state refrigeration with potential applications in electronics and human body thermoregulation. Although current EC polymers exhibit notable EC effects, their poor thermal stability, particularly around the die junction temperature (T_j ∼ 100 °C), poses a major barrier to large-scale applications. Here, we developed a P(VDF-HFP)-based polymer composite film by blending a small amount of P(VDF-TrFE-CFE) and dioctyl phthalate (DOP), followed by uniaxial stretching and fixed-end annealing. These processes, transforming the crystalline structure from spherulites to a fiber-like configuration, further increase the crystallinity and reduce the steric hindrance during dipole orientation, thereby enhancing the EC effect and forming a continuous ferroelectric (FE)-paraelectric (PE) phase transition over a broader temperature range. Direct measurements using an infrared camera show that the adiabatic temperature change remains stable (ΔT ∼ 3 K) from 30 to 100 °C. Moreover, the blend film demonstrates exceptional thermal stability, sustaining over 1400 cycles at 70 and 100 °C. In contrast, the pure P(VDF-TrFE-CFE) film fails after just 16 cycles at 70 °C and suffers dielectric breakdown immediately at 100 °C. Accordingly, these findings address critical challenges in the practical application of low-cost EC polymer films for thermoregulation and offer a pathway toward the commercial development of next-generation cooling devices.