Universal Morphology Engineering for Organic Bulk Heterojunction: Hot Fluorous Solvent Soaking

The power conversion efficiency of polymer solar cells based on bulk heterojunction is gradually increasing. However, to achieve an ideal donor/acceptor morphology with bicontinuous and interpenetrating network structure is still challenging. Recently, Hongliang Zhong’s group at Shanghai Jiao Tong University and the coworkers developed a new post-treatment strategy, namely hot fluorous solvent soaking (HFSS), to optimize the morphology of the active layer. The treatment of HFSS can anneal the active layer quickly and uniformly. When the selected fluorous solvent is miscible with the residue of processing solvent above upper critical solution temperature, the mixed solvent will further promote the reorganization of the donor/acceptor materials in the film, thereby forming a highly ordered fibrous structure. Consequently, the device shows higher carrier mobility and slightly red-shift absorption spectrum, providing an improved photovoltaic performance. This strategy performed with short processing time at relatively temperature is suitable for various combinations of donor/acceptor materials, including polymer/small-molecule systems, all-polymer and all-small-molecule systems.