Solution processing of the small molecule subnaphthalocyanine (SubNc) is carried out for the first time to form an electron-donor layer in efficient planar heterojunction organic photovoltaic cells (OPVs). Due to their unique properties, including high solubility, low tendency to aggregate, and strong light absorption in the visible light region, we are able to prepare amorphous SubNc films with high charge-transporting and light-harvesting properties via simple solution casting. By using SubNc as the donor and C60 as the acceptor, we have demonstrated a planar heterojunction OPV with a power conversion efficiency of 1.5%, which represents one of the highest efficiencies for planar heterojunction OPVs based on solution processable small molecules to date. This work clearly shows that solution processing of light-harvesting small molecules has great potential in low-cost thin-film photovoltaic cells. Also SubNc and its derivatives are promising new-generation materials for OPVs.