Piezoelectric Nanogenerators Based on Poly(vinylidene fluoride) Doped with High Entropy Oxide Nanoparticles for Sensitive Pressure Sensors

Considering the ecological and environmental challenges associated with conventional energy harvesting methods, piezoelectric nanogenerators (PENGs) offer a viable, lightweight, and environmentally friendly alternative for future energy needs. Here, we propose flexible, low-cost, superior piezoelectric performance poly(vinylidene fluoride) (PVDF)-based PENGs composed of high-entropy oxide nanoparticles, specifically (Bi0.2Na0.2Ba0.2K0.2La0.2)TiO3 (BNBKL) as a controlled filler. The structural, thermal, and electrical, such as dielectric, ferroelectric, and piezoelectric, properties of pure PVDF and all the nanocomposites were comprehensively investigated, demonstrating that the 7 wt % BNBKL nanoparticles incorporated PVDF (PBT-7) nanocomposite stands out as highly promising for nanogenerator applications. Furthermore, piezo-response force microscopy confirmed the high piezoelectric coefficient of the PBT-7 nanocomposite, showing a piezoelectric coefficient (d33) value of 33 pm/V. The inclusion of BNBKL nanofiller promotes the electroactive phase nucleation in PVDF (PBT-7), achieving a greater polar phase fraction [F(β) > 87%] compared to bare PVDF [F(β) > 50%]. Additionally, BNBKL-loaded PVDF nanocomposite-based PENGs demonstrated an exceptional power output of 64 μW under an applied periodic force of 10 N, with a maximum voltage of 34 V and a current of 4 μA. The optimized PENG device shows remarkable durability over 10,000 cycles and is effective for charging capacitors, powering light-emitting diodes, and monitoring real-time human movements. Further, the as-prepared film endowed with exceptional piezoelectric responsiveness was utilized as a highly sensitive self-powered pressure sensor, demonstrating its remarkable pressure sensitivity in the medium pressure range of 1.184 V/kPa, rapid response and recovery times of 9 and 38 ms, respectively, without any additional poling treatment. These findings highlight the significant potential of PVDF@BNBKL composites for diverse applications such as harvesting biomechanical energy, detecting motion, and supplying power to microelectronic devices, thus advancing the development of next-generation self-powered pressure sensors.