Fabrication of Multilayered Polyvinylidene Difluoride Films for Dielectric Capacitor, Sensing, and Energy Harvesting Performance

Abstract

In the present work, multilayered polyvinylidene difluoride (PVDF) films were prepared using the spin-coating technique. These films were annealed at 80 degrees C and 100 degrees C temperatures and finally hot-pressed at 150 degrees C to attain phase and strength. The X-ray diffraction (XRD) patterns and Fourier transform infrared spectroscopy (FTIR) data confirmed the presence of a mixture of alpha, beta, and gamma phases for each annealing temperature. The beta phase fraction was greater than 78% for all the films. The field-emission scanning electron micrograph (FESEM) showed an increase in average grain size with increasing annealing temperature. The thickness of the films decreased with the increasing spinning rpm. The dielectric constant, remanent polarization, and saturation polarization also reduced with increasing rpm, confirming the crucial role of thickness on the electrical and mechanical performances of the films. PVDF films annealed at 80 degrees C for 500 r/min showed a maximum output voltage and current of 24.8 V and 325 nA, respectively. The load-dependent open-circuit voltage and short-circuit current were measured by hand tapping the PVDF films. The maximum power density of 10.84 and 3.54 mu W/cm(2) was achieved across 1-M Omega load for P80C-500 and P100C-500 r/min films, respectively. The highest sensitivity of 4.96 V/N was obtained for the P80C-500 r/min film. The piezo voltage generated by hand tapping the PVDF film was stored in a commercial capacitor, which was used to illuminate two red LEDs on discharging. The film was able to generate voltage by detecting human body movement. Fist beating, film bending, and arm folding resulted in 19-, 11-, and 7-V voltage outputs, respectively. The PVDF films possess a higher dielectric constant and low dielectric loss, making them suitable for dielectric capacitor applications. The response of films toward varying human body movements makes them ideal for sensing applications.