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An environmentally-friendly lead-free methylammonium tin iodide (MASnI3) perovskite is successfully synthesized using a facile approach of an antisolvent-assisted collision technique (ACT) under room ambient conditions, which results stability within 24 h under ambient room conditions. The phase transition of MASnI3from tetragonal to cubic is first observed at ~ 30 °C. Polycrystalline MASnI3films reveal a high dielectric constant of ~ 65 at 100 kHz, a low-leakage current density of 7 × 10−7A cm−2at 50 kV cm−1, well-developed P-E hysteresis loops, and a high piezoelectric coefficient (d33) of 20.8 pm V−1. The MASnI3piezoelectric nanogenerator (PENG) shows an output voltage of ~ 3.8 V and an output current density of 0.35 μA cm−2. To enhance the piezoelectric output performance, the MASnI3films are composited with an environmentally friendly PVDF polymer that had a porous structure. The PVDF-MASnI3composite based-PENG reveals a maximum output voltage of ~ 12.0 V and current density of ~ 4.0 μA cm−2. A green light-emitting diode (LED) using the PVDF-MASnI3PENGs is instantly lighted without need of a storage device, and long-term stability of the composite PENGs is validated for 90 days. This simple and cost-effective solution process is feasible for the fabrication of large-scale, high-performance, and environmental-friendly PENGs based on lead-free organic-inorganic perovskites to extensively implicate in medical and biomechanical applications.

We report a high-performance flexible piezoelectric generator (PEG) that was based on organic-inorganic lead halide perovskite materials and is operated by controlling the dielectric constant via the partial substitution of Pb2+with Fe2+in MAPbI3. The partial replacement of Pb2+with Fe2+improved both the morphology and crystallinity of MAPb1-xFexI3(0.01 ≤ x ≤ 0.50) films that undergo a tetragonal-cubic phase transition above an incorporated concentration of Fe2+(x > 0.07). In addition, the phase transition temperatures of MAPb1-xFexI3(0.01 ≤ x ≤ 0.07) films linearly decreased as a function of incorporated concentration, which resulted in a transition temperature for MAPb1-xFexI3(x = 0.07) of ~ 45.5 ± 1.5 °C. The dielectric properties as a function of incorporated concentration at room temperature suggested that MAPb1-xFexI3(x = 0.07) exhibited a dielectric constant of ~107 and a dissipation factor of 0.02 at 100 kHz. The MAPb1-xFexI3(x = 0.07) films exhibited a low leakage current density of ~ 10−6at a high applied electric field of 40 kV/cm, and the resultant remanent polarization from saturated ferroelectric P-E hysteresis loops was ~ 1.6 µC/cm2. The MAPb1-xFexI3(x = 0.07) flexible PEG improved output performance by ~ 7.29 V and current density by ~ 0.88 µA/cm2after poling at 30 kV/cm. This was sufficient to instantly light a commercial light-emitting diode (LED) without a storage device. This approach provides a framework that enhances the output performance of organic-inorganic metal halide perovskite materials-based piezoelectric energy harvesters, which could help pave the road to viable, self-powered, wearable electronics.

One of the main challenges with implantable biomedical devices is the replacement surgeries of depleted batteries for elderly patients. This not only poses medical risks but also results in financial burdens. Consequently, there is a growing need for self-powered in vivo electronics that can convert the biomechanical movements of organs into usable electric energy. Notably, a previously reported in vivo flexible energy harvester generated relatively low current output from a living porcine heart, restricting its ability to operate self-powered electronic devices. In this study, a high current output implantable flexible energy harvester was demonstrated by adopting a highly piezoelectric single crystal Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3(PIN–PMN–PT) film. The in vivo flexible energy harvester generated a short-circuit output current of 20µA (corresponding to a current density of 3.08µA/mm3) from the contraction and relaxation of a porcine heart. This recorded in vivo output current density was attributed to its outstanding piezoelectric charge coefficient of the single crystal PIN-PMN-PT, optimized Ni stressor assisted exfoliation as well as the implementation of a metal-insulator-metal (MIM) structure. Moreover, the flexible energy harvester was also demonstrated as a self-powered cardiac sensor to monitor irregular heartbeats by observing heart rate variations due to drug administration in a porcine heart. Additionally, output performance evaluation was conducted with the chest closed to further assess the feasibility of practical in vivo harvesting. Finally, the single crystal harvester exhibited biocompatibility, showing no signs of cytotoxicity based on cell viability assessments and histological characterizations. These results underscore the potential of the flexible PIN-PMN-PT energy harvesting device as a sustainable power source for self-powered in vivo biomedical electronics.