Development of porous ZnO thin films for enhancing piezoelectric nanogenerators and force sensors

The applications of piezoelectric nanogenerators (PENGs) as a sustainable power source for portable electronic devices are still limited due to low voltage output ranging from mini- to several volts. In this study, we first develop a porous ZnO structure by annealing (650?950 ?C) sputtered ZnO thin film. The porous ZnO thin film enables a significant enhancement in the output voltage of primitive PENG (up to 3 mV), i.e., by 7.5 times than that of pristine ZnO (0.4 mV). Concurrently, the introduction of pores in ZnO thin films leads to a 6.9-fold enhancement in the sensitivity of piezotronic force sensor compared to the pristine one. These excellent performances are further supported by up to two-fold enhancement in the piezoelectric coefficient (2.62 pm/V) than that of pristine ZnO (1.12 pm/V). Herein, we conducted transmission electron microscopy characterizations and found that this phenomenon can be ascribed to the lattice contraction in the c-direction induced by the pores. The diffusion-controlled pore formation mechanism is elucidated.

Automated summary

This study explores the use of porous ZnO thin films to enhance the output voltage and sensitivity of piezoelectric nanogenerators. The presence of pores leads to lattice contraction in the c-direction, resulting in improved performance. Transmission electron microscopy characterizations confirm the mechanism behind the enhancements.