Direct electrocaloric characterization of polyvinylidene fluoride-based co- and terpolymers over a wide temperature range

Abstract

Polyvinylidene fluoride-based polymers have emerged as promising materials for flexible and portable electronics, attracting significant attention as alternatives to electrocaloric ceramics for more energy-efficient cooling. Although many studies report record-high electrocaloric effect values and initial proof-of-concept devices, the lack of comparative temperature-dependent studies and unexplained large discrepancies among various direct electrocaloric characterization methods hinder their full commercial exploitation. In this work, a systematic study of trifluoroethylene-based copolymers and chloro(tri)fluoroethylene-based terpolymers over a broad temperature range from room temperature to 100 °C using infrared imaging shows that commercially available polymers can compete with the best electrocaloric ceramics, exhibiting a large electrocaloric effect of ~4.5 K at 100 V µm−1 in several compositions. Furthermore, distinctly separated electrocaloric-effect peak values enable targeting different temperature regimes, making ferroelectric polymers attractive for a wide range of cooling applications. The established direct electrocaloric characterization method based on fast thermometry captures electrocaloric temperature changes near the adiabatic limit, resulting in lower measurement uncertainty and providing a valuable tool for resolving discrepancies in reported electrocaloric effects and contributing to standardization. In addition, we show that a simplified indirect Landau approach can reasonably estimate the magnitude of the electrocaloric effect, offering an additional method for evaluating different compositions.