We succeeded to fabricate p-n heterojunction and bulkheterojunction small-molecular-weight organic thin-film solar cells by combination of dry (p-type = zinc phthalocyanine, n-type = fullerene) and wet (p-type = tetra-tert-butyl zinc phthalocyanine, n-type = [6,6]-phenyl-C61-buteric acid methyl ester) processes. Relationship between morphologies of semiconducting layers and photovoltaic properties was investigated. The p-n heterojunction organic thin-film solar cells based on dry process, where surface roughness was approximately 2 nm, showed the highest power conversion efficiency of 1.3% in this paper.

We fabricated organic p-n heterojunction, p-i-n heterojunction and all-i-layer photovoltaic cells of a zinc phthalocyanine (ZnPc)/1:1 codeposition (ZnPc:C60)/C60 structure with Al cathode. We investigated the effects of the device structure and the cathode material on the photovoltaic properties. The thickness of the i-layer was changed as 0 nm (= p-n heterojunction), 10 nm (= p-i-n heterojunction) or 50 nm (= all-i-layer) with the total thickness of 50 nm. We also changed cathode materials from Al to low-workfunction Mg:Ag electrode. Photovoltaic properties, i.e., short-circuit current density, fill factor and power conversion efficiency, were strongly influenced by the device structure and cathode material. Finally, the power conversion efficiency showed a maximum (1.5%) with the p-i-n structure and a Mg:Ag cathode under Air Mass 1.5 global solar conditions.