Enhanced Efficiency of Polymer Solar Cells Via Simple Fluorination on the Π-Bridge of Polymer Donors

In this contribution, a novel fluorinated polymer based on the well-known J52, using the newly developed 3-fluorothiophene as pi bridges on the conjugated main chain, named J52-FTh, was synthesized and was used as polymer solar cells (PSCs) donor material. The effects of fluorinated pi bridge on the polymer's thermal stability, light absorption, energy level, molecular configuration and photovoltaic performance were systematically studied. It demonstrated that J52-FTh exhibited an enhanced absorption, a narrower optical band gap, a low-lying the highest occupied molecular orbitals (HOMO) energy level and better coplanar compared with J52 without any fluorine substituent on its pi bridges. The non-fullerene PSCs based on J52-FTh:ITIC (1:0.8, w/w) achieved a high PCE of 13.32% with a V-OC of 0.92 V, a J(SC) of 21.29 mA cm(-2) and an FF of 68%, which was much better than the PSCs based on J52:ITIC with a PCE of 5.51%. The results indicated that fluorination on the polymer's main chain was a simple and efficient strategy toward high efficiency.