Universal Formation of Com positionally Graded Bulk Heterojunction for Efficiency Enhancement in Organic Photovoltaics

摘要

The discovery of bulk heterojunction (BHJ) structures paved the road for high efficiency energy conversion by organic photovoltaic devices (OPVs) in the last decade. The morphology of BHJ films plays a critical role in charge generation, collection, or recombination in BHJ OPV devices. An ideal BHJ film morphology was suggested to have a bicontinuous interdigi-tated donor and acceptor network with donor and acceptor nan-odomains within the exciton diffusion lengths or the uncertain length of light for efficient charge generation and extrac-tion. However, the actual morphologies of most BHJ films are generally far from ideal due to the random mixing of donor and acceptor in solution. Regular BHJ films fabricated from the blended solution inevitably have many breaks and dead ends.