Triboelectric nanogenerators (TENGs) based on solution-processed zinc-oxide (ZnO) nanoripples acting as a triboelectric layer were fabricated to enhance their output voltage. Scanning electron microscopy images showed that ZnO nanoripples were uniformly formed on glass substrates coated with indiumtin oxide. The TENG containing ZnO nanoripples and operating in the vertical contact-separation mode exhibited an output voltage of 68 V, which was almost 3 times larger than that of the TENGs with ZnO nanorods. The open-circuit output voltages of TENGs were found to depend significantly on the condition of the ZnO nanoripple precursors. The friction force on the ZnO nanoripple matrix increased with increasing density of ZnO nanoripples due to an increase in the contact area between the ZnO nanoripples and the PI layer, resulting in an enhancement of the output voltage of the TENGs based on nanoripples. (C) 2018 Elsevier B.V. All rights reserved.