Multifunctional Lead-Free Halide Perovskite Based Poly(vinylidene fluoride) Composites for Biomechanical Energy Harvesting and Self-Powered Piezo-Optoelectronic Applications

Lead-free halide perovskite (LFHP) materials have recently received a lot of attention in optoelectronic applications due to their low toxicity and outstanding optical characteristics. Simultaneously, the increased thrust for flexible, wearable, and lightweight optoelectronic devices is driving improvements in sensor and actuator technology. In this context, flexible piezoelectric polymer composites based on LFHPs are gaining popularity due to their exceptional piezoelectric, pyroelectric, ferroelectric, and optical traits. Thus, this investigation presents long-term stable lead-free rubidium copper chloride (Rb₂CuCl₃)-based poly(vinylidene fluoride) composites. The optimized PVDF/Rb₂CuCl₃ composite yields ∼92.4% of the electroactive phase of the PVDF. Interfacial interactions between PVDF and Rb₂CuCl₃ have played a pivotal role in the electroactive β-phase transformation, resulting in improved long-term stability. A piezoelectric nanogenerator (PENG) has been fabricated employing the PVDF/Rb₂CuCl₃ composite for mechanical energy harvesting and biophysiological motion monitoring, demonstrating potential applications in the healthcare industry. The Piezoelectric Energy Harvester (PEH) with the PRCC_2.5 composite (PVDF composite of 2.5 wt % Rb₂CuCl₃) outperformed other composites, with a maximum open-circuit voltage (V_oc) of ∼51.7 V and a short-circuit current (I_sc) of ∼4.6 μA. The pristine PVDF-based device (PEH 0) had inferior performance, with a V_oc of ∼12 V and an I_sc of ∼0.5 μA. PEH 2.5 device exhibited a charge of ∼126 nC, which is far higher than the PEH 0 for which the corresponding charge was ∼7 nC. Furthermore, during the periodic application of the force of ∼5 N, the stability and durability of the PEH 2.5 device were evaluated. 10,250 compression cycles were used to measure the electrical output of the PEH 2.5 device. Remarkably, following the 10,250 cycles, there was no discernible drop in the output voltage (∼16 V). In addition, a photodetector has been developed to investigate the piezo-phototronic effect, displaying quick photoswitching behavior with rise and decay periods of ∼3.22 and ∼5.48 s, respectively. These findings demonstrate that the flexible PVDF/Rb₂CuCl₃ composites have significant potential as an optical signal-modulated piezoresponsive wearable sensor.