Lead-free piezoelectric energy harvesting using Potassium Sodium Niobate (KNN) thin film based cantilevers

In the present study, a comprehensive evaluation of the piezoelectric energy harvesting capability of cantilever devices has been carried out using lead-free Potassium Sodium Niobate (KNN) thin films deposited via Radio-Frequency (RF) magnetron sputtering. The fabricated device configuration comprises interdigitated gold electrodes patterned onto the surface of KNN thin film integrated onto a Silicon dioxide/Silicon (SiO 2 /Si) substrate. Finite-element modelling studies are also carried out using COMSOL Multiphysics to estimate its fundamental resonant frequency, which was predicted to be 4.63 kHz. This simulated resonance was subsequently corroborated through experimental measurements using Laser Doppler Vibrometer (LDV), confirming the accuracy of the structural and material modelling. Electrical characterizations revealed that the KNN based cantilever generates a maximum output power density of 8.04 mWcm −3 when connected to an optimal load resistance of 0.1 MΩ, accompanied by a peak open-circuit voltage of 97.5 mV. The obtained performance metrics demonstrated effective vibration-to-electricity conversion, which is particularly relevant for ambient energy harvesting and sensing applications. Hence, the results underscore the strong potential of RF sputtered KNN thin film based cantilevers as environmentally friendly alternatives to conventional lead-based piezoelectric materials.