We propose that solvent-vapor annealing is an efficient method for fabricating large [6,6]-phenyl C 61 butyric acid methyl (PCBM) single crystals. The morphology and size of PCBM crystals are influenced by different substrates and annealing solvents. Hexagonal PCBM crystals >150 μm in size were obtained when crystallization was performed on bare SiO 2 substrate under the saturated vapor of chloroform for annealing. The proposed method was also applied to a bi-component system, which led to the spontaneous formation of PCBM and dioctylbenzothienobenzothiophene single crystals.