Fluorination strategy on π-bridge of polymer donor for efficient photovoltaic performance

Abstract

Although fluorine-contained polymers have been adopted in efficient polymer solar cells, complicated reaction methods and costly fluorination reagents have impeded large-scale application. Here, a novel fluorinated polymer donor, PM6-F, was designed and synthesized via a newly developed 3-fluoro-2-iodithiophene to simplify synthesis procedures and minimise reaction costs from modest raw materials. Compared with the polymer analogue PM6 without any fluorine substituent on the main chain, it was found that PM6-F with a better configuration exhibited more orderly molecular packing, stronger and broader absorption, a narrower optical band gap, and a lower-lying HOMO energy level. The PM6-F:IT-4F-based PSCs obtained an excellent PCE of 14.90% with a VOC of 0.91 V, a JSC of 23.25 mA cm−2, and an FF of 70.42%. Notably, the value of 14.90% was among the highest recorded in the literature for IT-4F-based PSCs. This research demonstrated that modifying π-bridges with fluorine is a promising strategy for developing high-efficiency polymer donors.