Hierarchical ZnO nanorods on Si micropillar arrays for performance enhancement of piezoelectric nanogenerators.

Enhanced output power from a ZnO nanorod (NR)-based piezoelectric nanogenerator (PNG) is demonstrated by forming a heterojunction with Si micropillar (MP) array. The length of the SiMP array, which was fabricated by electrochemical etching, was increased systematically from 5 to 20 μm by controlling the etching time. Our structural and optical investigations showed that the ZnO NRs were grown hierarchically on the SiMPs, and their crystalline quality was similar regardless of the length of the underlying SiMPs.