A rationally designed output current measurement procedure and comprehensive understanding of the output characteristics for piezoelectric nanogenerators

Highlights: • A theoretical study is performed to prove the existence of the maximum peak current. • The maximum peak current is measured by a rationally designed procedure. • Different influence factors on the output characteristics are elaborated. Scavenging energy by piezoelectric nanogenerators (PENG) has been spotlighted as a promising approach to convert tiny mechanical energy into electricity. Many works have been done to improve the measurement techniques as well as reveal the output characteristics of PENGs. However, for the precise measurement of the output current, there still remains uncertainty stems from the effect of strain rate when applying mechanical impact onto PENGs. Herein, a theoretical derivation is performed to prove the existence of the maximum peak current (MPC) for PENGs, which is not influenced by strain rate but only determined by the magnitude of the applied force and inherent parameters of PENGs. A rationally designed procedure is proposed to measure the MPC with high accuracy and stability, from which an analytical model describing the MPC is established. The influence of device capacitance and the applied force on the output characteristics of PENGs are revealed, from which essential rules pertaining to the characterization and optimization for PENGs are proposed. Through this study, we can get comprehensive insight into the output characteristics of PENGs and acquire new guidelines for purpose design of PENGs and corresponding power management circuits.