We reported a novel metal/semiconductor triboelectric nanogenerator (TENG) based on Au and TiO2 as the
friction layers. Upon illumination, the current polarity rapidly reverses compared to the dark state. The negative
and positive short-circuit current approximately increase by 12 and 2 times, respectively. Particularly, a photocurrent
plateau appears due to the formation of metal-semiconductor Schottky contact in the device. By
carefully analyzing the charge transfer in dark and under illumination, it is found that the accumulation of a
large number of photoelectrons on the surface of TiO2 and the increase of conductivity are the reasons for the
reversal current polarity and significant current increase under illumination. Our work provides a new approach
for improving TENG output and a new understanding about the effect of surface states on the triboelectric
performance especially the polarity of TENG.