Random copolymerization realized high efficient polymer solar cells with a record fill factor near 80%

In this work, we successfully achieved a record fill factor (FF) of near 80% by using random copolymerization strategy to precisely control the morphology of active layer for polymer solar cells (PSCs). A series of random copolymers were synthesized by random copolymerization of a self-assembly third unit into the multithiophene-based polymer matrix. The random copolymers possess excellent room temperature processing performance due to their relatively weaker self-aggregation properties. More importantly, despite the non-irregular sequence of random copolymers, the planarity of the third unit favored by the S...O intramolecular interaction still induced a face-on orientation of the random copolymers and formed a homogeneously fibril-like interpenetrating network structure in the blend films. Ultimately, the random polymer-based device achieved a remarkably high fill factor (FF) near 80% without any treatment, even approaching to the values of the inorganic materials-based solar cells.