High β-crystallinity comprising nitrogenous carbon dot/PVDF nanocomposite decorated self-powered and flexible piezoelectric nanogenerator for harvesting human movement mediated energy and sensing weights

This work reports a flexible and wearable nanocomposite made of nitrogen doped carbon dot (N-CD) modified PVDF (PCD) nanocomposite assisted piezoelectric device (PPNCD) that can harvest different forms of mechanical energy and convert them into electrical energy. The efficacy of this device is dependent upon its ‘sandwiched’ structure made of PCD nanocomposite wrapped with aluminum electrodes on both sides. Herein, N-doped CD has been incorporated into PVDF matrix for obtaining maximum β-crystalline phase (F(β) ∼ 80.4%), which is confirmed by XRD, FTIR and DSC analysis. The polarizability of the PCD nanocomposite has a great contribution to the total output performance of the device. The polarizability of the film has been measured by using a standard density functional approach. The piezoelectric coefficient (d₃₃) has also been calculated, which is found to be 29 pC/N. Such augmented electrical parameters and enhanced piezoelectric coefficient are further utilized to fabricate the PPNCD device, which is capable to detect human body movements efficiently and can act as a weight sensor with a sensitivity of 10.2 V/kPa (up to 0.5 kPa). Moreover, this device provides a power density of 1979.87μWcm⁻³ and exhibits an exceptional output performance (V_OC ∼ 80V) under periodic finger impartations in comparison to other carbon based piezoelectric nanogenerators. The PPNCD device can illuminate 15 blue/white LEDs and charge a 2.2 μF capacitor within a few seconds under continuous finger impartations. Such a multifunctional device could be a promising candidate for both healthcare monitoring systems and their power supplies.