Micropatterning of flexible and free standing polyvinylidene difluoride (PVDF) films for enhanced pyroelectric energy transformation

In an effort to harvest thermal energy and exploit abundantly available waste heat the pyroelectric effect offers the opportunity to convert temperature fluctuations into useable electrical energy. Here, the micropatterning of the surface of a pyroelectric in order to enhance heat transfer and achieve faster and larger temperature fluctuations, which improve pyroelectric energy transformation, is reported. Methods for the fabrication of partially covered electrodes on polyvinylidene difluoride (PVDF) films are developed to investigate and quantify the benefits of such an electrode structure for pyroelectric energy harvesting. The micropattern consists of an array of holes that are etched into the upper aluminum electrodes of free standing ferroelectric PVDF films using a low cost photolithography and wet etching process. Under the application of infrared radiation heating, it is demonstrated that such microfeatures are able to significantly improve the open circuit voltage by 380% and the closed circuit current by 420% for an electrode area coverage of 45% when compared to a fully covered electrode design. Capacitance measurements show constant electric fields with microfeatures for electrode area coverages as low as 28%. A specific generator performance of 66.9 μJ cm−3 cycle−1 is presented at oscillation temperatures of 2.8 °C.