Self-polarized piezoelectric thin films: preparation, formation mechanism and application

A facile method is introduced for preparation of porous self-polarized piezoelectric thin films (100-300 nm) by depositing polyvinylidene fluoride solution onto the surface of an aqueous solution. A polar beta crystalline phase enhancement is realized with the addition of sodium chloride into the aqueous solution. Fully saturated piezoresponse hysteresis loops and out-of-plane piezoresponse phase images imply the high piezoelectricity and self-polarized property of the as-prepared films. Also, we fabricate a device and evaluate its performance. A high sensitivity of 52.2 pC N-1 and an electric output of over 24 V and 16 mu A are revealed. Therefore, we provide a convenient and low cost approach to obtain self-polarized piezoelectric films with an enhanced polar beta crystalline phase and create a dual functional device for pressure sensing and electricity generation.