UV-A TREATMENT OF P(VDF-TRFE-CFE): A ROUTE TO EFFICIENT SOLID-STATE COOLING SOLUTIONS

Electrocaloric (EC) materials are gaining significant attention as eco-friendly alternatives to traditional gas refrigerants in next-generation cooling technologies due to their outstanding caloric properties and compact design [1]. The EC effect, which is characterized by isothermal entropy change (ΔS) and adiabatic temperature change (ΔTadia) under an applied electric field, has already been demonstrated in several cooling devices [2]. Among the promising candidates, the P(VDF-TrFE-CFE) terpolymer stands out for its large ΔTadia and ease of processing into thin films via solvent casting. However, solvent-cast films typically exhibit insufficient EC responses (1.5 °C at 50 V/μm) and high dielectric losses, limiting their potential in practical applications [3]. In this work, we present a straightforward post-processing method using low-energy UV-A irradiation to enhance the EC effect and minimize dielectric losses in P(VDF-TrFE-CFE) films. After irradiation, the material exhibits new functional groups, thicker crystalline lamellae, and a denser structure. X-ray diffraction under an electric field reveals the appearance of a defective ferroelectric phase alongside the ferroelectric (FE) phase, with the latter occurring at a lower electric field post-irradiation, indicating that UV-induced modifications favor the polar phase. These changes result in a significant improvement in EC performance, with an increase in ΔTadia from 1.76 °C to 2.88 °C at 60 V/μm and reduced dielectric losses. This work highlights a simple yet effective strategy to enhance the performance of P(VDF-TrFE-CFE) terpolymer films, making them more suitable for solid-state refrigeration applications.