The response of a single CdS-nanowire-based nanogenerator to excitation by visible light is investigated. White light reduces the height of the Schottky barrier that existis at the tipnanowire contact, leading to possible barrier breakthrough and a contact-mode change from Schottky to quasi-Ohmic. This work demonstrates the triple coupling among semiconducting, piezoelectric, and optoelectric properties, which may be useful for designing new optopiezotronic devices.