Furan-based liquid-crystalline small-molecule donor guest improving the photovoltaic performance of organic solar cells with amorphous packing

Introducing liquid-crystalline small-molecule donors (SMDs) into binary systems based on the strong intermolecular interactions of SMDs is a facile and effective strategy to tune the active layer morphology and improve the performance of organic solar cells (OSCs). Contrary to conventional understanding, this research proposes a new strategy for ternary OSCs implicating that “weakly crystalline materials can also optimize the morphology of the active layer and improve the OSCs performance”. Herein, we designed and synthesized two liquid-crystalline SMDs, Z1 and Z2, based on benzodifuran (BDF) units. The amorphous Z2-incorporated ternary devices present an unexpectedly improved power conversion efficiency (PCE) > 18% with good stability. By contrast, the highly ordered Z1-based ternary devices possess a significantly depressed efficiency. Multiple characterizations reveal that the Z2-based ternary blend films possess improved miscibility and efficient charge transport. This novel strategy for the selection of the third component is significant for the fabrication of high-efficiency ternary OSCs. [Figure not available: see fulltext.]