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

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 beta,alpha and Curie mode (rho) 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 degrees C] to increase their crystallinity. A remnant polarization current of 76.7 mC m(-2), which gives a pyroelectric coefficient of 31 mu C m(-2)K(-1)and a figure of meritF(D)of 86 mu C m(-2)K(-1)(1 kHz), was obtained from the sample annealed at 100 degrees C, where the percentage of crystallinity was maximum and the phase was about to transition from ferroelectric to paraelectric.