High Performance and Direct Current Piezoelectric Nanogenerators Using Lithium‐Doped Zinc Oxide Nanosheets

Abstract

The wurtzite structured zinc oxide has been studied extensively because of its unique characteristics, such as transparency, semiconducting properties, and excellent piezoelectricity. However, the defects that are inevitably present in ZnO grown by the aqueous solution method generate excessive free electrons, which reduce the piezoelectric potential by the screening effect, thus reducing the piezoelectric output performance. Herein, direct current high‐performance piezoelectric nanogenerators (PENGs) based on Li‐doped ZnO nanosheets are demonstrated. Doping with the p‐type dopant Li reduces the number of free electrons in ZnO, minimizing the screening effect and improving the piezoelectric output performance. First, Li‐doped ZnO nanosheet is synthesized at various Li concentrations using the aqueous solution method. The doping effect on the morphology and crystal structure of the ZnO nanosheet is investigated via scanning electron microscopy and X‐ray diffraction. X‐ray photoelectron spectroscopy confirmed that the ZnO nanosheet is doped with lithium. The Li‐doped ZnO nanosheet‐based PENG produce an output power of 6.552 mW cm−2, that is, a 16‐fold enhancement in output power compared to that of the undoped ZnO nanosheet‐based PENGs.