Introducing Fluorine and Sulfur Atoms into Quinoxaline-Based p-type Polymers To Gradually Improve the Performance of Fullerene-Free Organic Solar Cells.

Three quinoxaline-based "D-π-A" conjugated polymers, named as PE61 , PE62 , and PE63 , are utilized to investigate the effect of introducing fluorine and sulfur atoms into the thiophene side chains on the photovoltaic performance when paired with a nonfullerene Y6 . The open-circuit voltage ( V OC ) and power conversion efficiency (PCE) can be improved from 0.66 V and 8.61% for PE61 : Y6 to 0.78 V and 12.02% for PE62 : Y6 , and then to 0.83 V and 13.10% for PE63 : Y6 , respectively. The results provide a simple and effective strategy to fine-tune the optoelectronic properties and thus improve the photovoltaic performance.