The relation between crystal quality and the properties of indium phosphide nanowires grown on silicon (111) was studied by TEM, photoluminescence spectroscopy, and photoelectrochem. Wires with no defects and with {111} twin boundaries parallel and perpendicular to the growth direction were obtained by OMVPE using liq. indium catalyst. Room temp. photoluminescence from the defect-free nanowires is 7 times more intense than that from the wires with twin boundaries. An open-circuit photovoltage of 100 mV is obsd. for photoelectrochem. cells made with the defect-free nanowires, whereas no photovoltage is recorded for those with twins. [on SciFinder(R)]