P(VDF-TrFE)/BaTiO₃ nanocomposite Langmuir-Schaefer thin film for piezoelectric nanogenerator

In this study, a piezoelectric nanogenerator (PENG) was fabricated based on nanocomposite thin films comprising piezoelectric poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) as a matrix and BaTiO₃ (BTO) nanoparticles (NPs) as a nanofiller. The Langmuir-Schaefer (LS) technique was employed to prepare the films. A mixed solution of the polymer and ceramic NPs was spread on the surface of water subphase at a predetermined surface pressure, and thin films were then prepared by transferring the spread monolayer onto indium tin oxide-coated polyethylene terephthalate (ITO-PET) substrate multiple times at a constant surface pressure. Microstructure, crystallinity, β-phase content, dielectric constant, and piezoelectric coefficient (d₃₃) of the thin films were measured with SEM, XRD, FT-IR, LCR meter, and Quasi-static meter, respectively. Six different PENG devices with different BTO contents were fabricated by arranging the thin film-coated substrates in sandwich structure, and they were subject to measurements of piezoelectric characteristics such as open-circuit output voltage (V_OC) and short-circuit current (I_SC). As results, it was found that the PENG with 4 wt% BTO with ten layers of monolayer deposited at the surface pressure of 15 mN/m yielded the highest V_OC of 71.4 V, which was higher than pristine polymer LS film's 66.2 V at the same conditions, and power density of 35.7 μW/cm² at 2.5 Hz bending-releasing frequency. This optimum piezoelectric performance was explained in terms of the highest crystallinity, β-phase content, and dielectric properties at the specific BTO content. The optimum PENG coupled with a capacitor and several light emitting demonstrated that it is possibly used to supply power with large energy storage capability of 470 µJ with a 1 µF capacitor for 3 min. This PENG of improved performance is promising as a supply power for a self-powered microelectronics because it has additional advantages of facile fabrication and coating a large area.