A method of preparing a bulk heterojunction organic photovoltaic cell through combinations of thermal and solvent vapor annealing are described. Bulk heterojunction films may prepared by known methods such as spin coating, and then exposed to one or more vaporized solvents and thermally annealed in an effort to enhance the crystalline nature of the photoactive materials.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
 The subject matter of this application was prepared with U.S. Government support under Contract No. DE-FG36-08GO18022 awarded by U.S. Department of Energy, National Renewable Energy Laboratory. The government has certain rights in the subject matter of this application.