Two types of p-n heterojunction devices consisting of thin films of titanyl phthalocyanine (TiOPc) and N,N’-dimethyl-3,4:9,10-peryle nebis(dicarboximide) (MPCI), sandwiched between indium tin oxide (ITO) and gold (Au),have been fabricated, and their performance characteristics investigated. The devices showed a response to light over the whole visible wavelength region from 400 to 900 nm. The cell with a structure of ITO/MPCI/TiOPc/Au (Type A) was superior to the cell with a structure of ITO/TiOPc/MPCI/Au (Type B) in the conversion efficiency. The cell of type A exhibited conversion efficiencies of ca. 0.7% for the monochromatic light of 470 or 720 nm reaching the organic layer through the electrode, and ca. 0.35% for incident white light (8-130 mW cm(-2)).