Simple Approach for Synthesizing a Fluorinated Polymer Donor Enables Promoted Efficiency in Polymer Solar Cells

Abstract

In this contribution, we used a practical method to synthesize 3-fluorothiophene as π-bridge units on the polymer backbone via constructing 3-fluoro-2-iodothiophene to decrease synthesis steps and lower costs. Fluorine atoms introduced into the polymer backbone can improve polymer planarity, packing, crystallinity, and hole mobility via extensive noncovalent interactions such as F−H, F−Cl, F−S, and F−π. When compared to the analogue PBZ-Cl without any fluorine substituent on the thiophene unit, our fluorinated polymer J52ClF exhibited red-shifted absorption of roughly 42 nm with a narrower band gap (E g opt ) of 1.82 eV, a low-lying highest occupied molecular orbital (HOMO) energy level, and a highly coplanar molecular configuration in the backbone. The optimal device based on J52ClF:IT-4F achieved a desired power conversion efficiency (PCE) of 14.59%, a V OC of 0.93 V, a J SC of 22.67 mA cm −2 , a fill factor (FF) of 69.22%, and an E loss of 0.57 V, all of which were significantly superior to those of PBZ-Cl:IT-4F (PCE = 9.7%). It demonstrated that fluorinating π-conjugated bridges utilizing 3-fluoro-2-iodothiophene is a practical strategy that deserves greater attention for increasing photovoltaic performance.

Fluorinated Polymer Donors for Nonfullerene Organic Solar Cells

“…Xu and coworkers reported polymer J52ClF by employing 3-fluorothiophene as πbridge. [88] The fluorine atoms can improve polymer planarity, crystallinity and hole mobility due to intramolecular and intermolecular noncovalent interactions, such as FÀ H, FÀ Cl, FÀ S, and F-π. The J52ClF : IT-4F device exhibited a decent PCE of 14.59 % due to its enhanced V OC and J SC .…”

“…A PCE of 9.34 % was obtained for PBTZ ‐ C4T : ITIC ‐ Th1 based devices. Xu and coworkers reported polymer J52ClF by employing 3‐fluorothiophene as π‐bridge [88] . The fluorine atoms can improve polymer planarity, crystallinity and hole mobility due to intramolecular and intermolecular noncovalent interactions, such as F−H, F−Cl, F−S, and F‐π.…”