Strategies for β‐Phase Enhancement in PVDF Toward Advanced Flexible Ferroelectric and Piezoelectric Devices

We report the influence of molecular weight, concentration, poling voltage, and thermal treatment on the ferroelectric and piezoelectric performance of polyvinylidene difluoride (PVDF) fibers and thin membranes. PVDF thin membranes with three different molecular weight ( M w ) (250,000; 1,000,000 and 1,200,000 g/mol) were fabricated using the solvent‐casting technique. The influence of different poling voltages (0, 1, 3, and 5 kV) was applied during the fabrication of membranes at 80°C to examine the ferroelectric response. The enhancement of β‐phase in fibers and thin membranes was confirmed by X‐ray diffraction. The Fourier transform infrared spectroscopy revealed higher β‐phase content in electrospun fibers (89.9%) compared to solvent‐cast membranes (78.9%). Polarization versus applied field hysteresis loops (100 kV) revealed that PVDF membranes of 1,200,000 g/mol poled at 5 kV produced the highest polarization without leakage. The piezoelectric performance of the samples was assessed through a nanogenerator. The highest β‐phase content was observed in PVDF fibers dried at 80 °C. An open‐circuit voltage ( V oc ) of 10.83 V, short‐circuit current ( I sc ) of 3.79 mA, and a power density of 2.112 W/m 2 at 45 MΩ (load resistance) were achieved. These results highlight the critical role of M w and heat treatment in enhancing PVDF for energy‐harvesting applications.