Solution-processed small-molecule solar cells with power conversion efficiencies of 6.7% are reported online this week in Nature Materials. The performance of these devices rivals that of the best polymer-based solar cells, and they have the potential be mass-produced with better reliability.
Organic bulk heterojunction solar cells, which convert sunlight into electricity, are based on organic semiconductor blends. The possibility to deposit organic semiconductors by solution-based processes such as printing makes these materials potentially attractive for the mass production of flexible large-area photovoltaic devices. The most efficient organic bulk heterojunction solar cells today are fabricated using semiconducting polymers. Owing to the synthesis process, such polymers can show larger batch-to-batch variations in composition and device performance than small molecules.
Through careful molecular design, Guillermo Bazan and colleagues developed a small-molecule semiconductor that can be solution processed into efficient bulk heterojunction solar cells. The performance of these devices approaches that of the best polymer-based solar cells.