The photoresponse of a p-type Cu2O him on copper is presented. The cur
rent-voltage characteristics exhibit a large photocurrent with an onse
t potential at cn. -0.2 V (S.C.E.). The electrode in the Cu2O/Pt biase
d cell shows high quantum efficiency which is approaching 100% for wav
elength lambda approximate to 300 nm. Studies show that even for poten
tials just slightly more negative than V-on, the quantum efficiency is
relatively large. This result may be explained either by a current do
ubling phenomena or could be due to a contribution to additional band
gaps which may er;ist at higher energies. The overall high quantum eff
iciencies, moreover, can be obtained without the use of any external b
ias if a TiO2 counter electrode is used. (C) 1997 Elsevier Science Ltd
.