High piezoresponse in low-dimensional inorganic halide perovskite for mechanical energy harvesting

The potential use of halide perovskite materials in ferroelectric and piezoelectric devices has recently been unraveled, but for widespread applications, detailed and systematic experiments are essential. We report on a preferentially oriented low dimensional (2D) layered all-inorganic halide perovskite material - CsPb<inf>2</inf>Br<inf>5</inf>, demonstrating piezoelectric and ferroelectric behavior at room temperature. We have further fabricated a composite of preferentially orientated CsPb<inf>2</inf>Br<inf>5</inf> microplates with polyvinylidene fluoride (PVDF) to study its energy harvesting behavior as a nanogenerator. The pristine tetragonal CsPb<inf>2</inf>Br<inf>5</inf> microplates show a piezoelectric coefficient (d<inf>33</inf>) value of ≈72 pm V⁻¹ and a remanent polarization of ≈0.06 μC cm⁻² estimated from piezoelectric force microscopy (PFM) and polarization hysteresis (PE) loop measurement, respectively. Four composite devices with varying weight percentages of perovskite in the PVDF matrix are investigated and compared with a pure PVDF-based nanogenerator to assess their energy harvesting performance. It is observed that the CsPb<inf>2</inf>Br<inf>5</inf>-PVDF hybrid films respond as excellent functional materials for piezoelectric-based mechanical energy harvesters. The incorporation of CsPb<inf>2</inf>Br<inf>5</inf> into the PVDF matrix allows for high crystallinity and electroactive-phase nucleation of approximately 92% in the PVDF, which is greater than pristine PVDF. Under periodic vertical compression, the best device fabricated has an instantaneous output voltage of ≈200 V, a current of ≈2.8 μA, and a power of ≈45 μW across a 5 MΩ resistor. The output voltage is also produced by various human actions like leg pressing, finger bending, and arm bending using the best device. The output AC voltage of the best device is used to charge a capacitor of 2.2 μF capacitance up to ≈3.8 V DC, which is further used to light up some LEDs as a proof of concept. Our findings have the potential to pave the way for high-performance nanogenerators using a layered halide perovskite family of materials.