Harnessing silicon facet-dependent conductivity to enhance the direct-current produced by a sliding Schottky diode triboelectric nanogenerator

Abstract

Harnessing triboelectricity is a promising form of energy harvesting technology. Unlike conventional triboelectric nanogenerators, which convert friction between insulators into alternating current, a sliding metal‒semiconductor contact converts small movements into direct current (d.c.), which can power electronic circuitry without the need of electrical rectification. The zero-bias d.c. output of a dynamic metal‒semiconductor contact is assumed to increase linearly with its area, posing restrictions on the miniaturization of this new type of power sources. By implementing silicon surfaces that are electrically heterogeneous, it is found that d.c. outputs are not steady-state, but instead peak when the metal contact slides across concave boundaries between highly and poorly rectifying silicon crystal facets. Sharp lateral changes in electrical rectification, coupled to a concave surface curvature, are more important to maximize current densities than applied normal force or surface friction. These findings help alleviating device-wear issues, as well as removing physical constraints to the miniaturization of sliding-diode nanogenerators.