Purified and porous poly(vinylidene fluoride-trifluoroethylene) thin films for pyroelectric infrared sensing and energy harvesting

This paper aims at improving the performance of the poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer for pyroelectric infrared detection and direct thermal to electrical energy conversion. Three different types of samples were prepared and examined: commercial, purified and porous films. Here, full characterization of the thermophysical and electrical properties relevant to pyroelectric infrared detection and energy conversion of both purified and porous P(VDF-TrFE) thin films is presented. Properties measured include (1) density, (2) ferroelectric to paraelectric phase transition temperature, (3) enthalpy of change of phase, (4) electrical resistivity and (5) ferroelectric hysteresis, as well as (6) specific heat, (7) dielectric constant, (8) loss tangent and (9) pyroelectric coefficient as a function of temperature. The figures of merit for infrared detection F-V, F-I and F-D were improved by 47.0, 59.6 and 51.6%, respectively, for the purified films while the porous films with a porosity of 33% showed an improvement of 52.8, 66.3 and 62.6%, respectively, when compared to those of dense commercial P(VDF-TrFE) films. In addition, figures of merit for energy harvesting, F-E and k(2), indicate that the purified and porous films are attractive for thermal to electrical energy conversion as well.