Vertical nanowire arrays are attractive as cell culture substrates, as they can steer the behavior of cells cultured on the array. Hence, the effects of culturing cells on various vertical nanowire arrays have been extensively studied. However, less is known about the effects of culturing cells on nanowires that have optoelectronic properties, such as nanowire solar cells. Here, we study the effects of photovoltaic nanowires on human cancer cells. Human A549 lung cells were cultured on vertical indium phosphide nanowire pn junctions (solar cells), and kept in light or dark conditions. Our results show that cells cultured on the nanowire solar cells exposed to light are present in lower density on the substrate compared to cells kept in the dark. Moreover, we could see a larger fraction of cells in the G0 cell cycle phase among cells cultured on illuminated solar cells. Altogether, this suggests that culturing cells on photovoltaic nanowires exposed to light can induce cell dormancy in a cell population subset. We also observed a recovery in cell proliferation after the illumination was turned off. Chemotherapeutic-induced dormant state has been observed for cancer cells, leading to treatment resistance. Future work will be directed to using photovoltaic nanowire arrays to study and manipulate cancer cell dormancy, in order to possibly use photovoltaic nanowires as a tool in cancer research.