Thermally Stimulated Current Study and Relaxation Behaviour of Annealed Copolymer P(VDF-TrFE) Films for Potential Pyroelectric Energy Harvesting

Abstract

The effects of annealing treatment on the polarization of copolymer P(VDF-TrFE) free-standing films were thoroughly studied by the thermally stimulated current (TSC) method using decomposition analysis and first-order kinetic theory. The TSC measurement mainly revealed three depolarization peaks, which are known as the β, α and Curie mode (ρ) peaks in P(VDF-TrFE). The origin of the TSC peaks and their relaxation behaviour were correlated with structural, morphological and electrical properties such as ferroelectricity, dielectricity and pyroelectricity. Spin-coated copolymer thin films with thicknesses of 300 nm were also prepared from 5 wt.% solutions. Both free-standing and thin films were initially annealed in the range of their Curie temperature up to the melting point [80–140°C] to increase their crystallinity. A remnant polarization current of 76.7 mC m−2, which gives a pyroelectric coefficient of 31 μC m−2K−1 and a figure of merit FD of 86 μC m−2K−1 (1 kHz), was obtained from the sample annealed at 100°C, where the percentage of crystallinity was maximum and the phase was about to transition from ferroelectric to paraelectric.