Three-layered organic solar cells incorporating a co-deposited interlayer of fullerene and metal-free phthalocyanine, whose nanostructure was optimized by controlling the substrate temperature during co-evaporation, showed a photo-electric conversion efficiency of 2.5% under illumination with simulated solar light. The three-layered cells were concluded to have a p-i-n-like energetic structure. For the long-term operation, cells should be isolated from air to avoid the ingress of oxygen or water.