Photocurrent generation in an indium-tin oxide (ITO)/iodine-doped Ni-phthalocyanine (NiPc-I-x)/C-60/In/Al heterojunction device with x similar to 1 was studied. By keeping the device in air after preparation, the device slowly reached a stationary state in which the sign of the photocurrent is opposite to that of a non-doped ITO/NiPc/C-60/In/Al device although the rectification direction for the dark current is the same. By a simulation of incident photon-to-current conversion efficiency spectra and a measurement of internal electric field by electroabsorption spectroscopy, it was elucidated that, in the doped device, the band bending near the phthalocyanine/C-60 interface is absent and the photocurrent is generated by a weak Schottky barrier at the C-60/In interface. It is also shown that the C-60 film encapsulates the doped iodine into the NiPc-I-x layer to stabilize the doping level and prevent the reaction of iodine with In. (C) 2012 Elsevier B.V. All rights reserved.