Out-of-Plane Polarization in Bent Graphene-Like Zinc Oxide and Nanogenerator Applications

D Tan and M Willatzen and ZL Wang, ADVANCED FUNCTIONAL MATERIALS, 30, 1907885 (2020).

DOI: 10.1002/adfm.201907885

Highly efficient piezoelectric nanogenerator operation is demonstrated based on dynamic bending of graphene-like ZnO nanosheets. Energy is harvested by an external resistor by virtue of a strong time-varying piezoelectric polarization component perpendicular to the graphene-like ZnO plane. It is shown analytically and verified numerically using molecular dynamics simulations that the 6 over bar m2 point group of flat graphene-like ZnO is reduced to monoclinic m symmetry for bent graphene-like ZnO. The latter symmetry allows for a nonzero and large piezoelectric polarization component perpendicular to the plane of the 2D structure. The numerical results confirm that flexoelectric effects are negligible subject to graphene-like ZnO bending operation.

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