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-pi-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.