An efficient polymer acceptor with fluorinated linkers enables all polymer solar cells with an efficiency of 15.7%†
*ab
Abstract
Despite the significant progress in all-polymer solar cells (all-PSCs) in recent years, obtaining both high open-circuit voltage (VOC) and short-circuit current density (JSC) simultaneously has been a challenging issue. Herein, a novel polymer acceptor PY-DF was developed by polymerizing small molecule acceptor (SMA) monomers with difluorothiophene linkers. Compared to non-fluorinated PYT, PY-DF exhibits a more coplanar and rigid molecular conformation, which leads to better intra-molecular conjugation and enhanced interchain packing, resulting in improved electron mobility and reduced energetic disorder. Furthermore, PY-DF exhibits a relatively up-shifted lowest unoccupied molecular orbital (LUMO) energy level (−3.76 eV) than PYT (−3.80 eV), which is favorable for improving VOC. In addition, the polymer acceptor demonstrates good miscibility with polymer donor, thus leading to optimized phase segregation for superior exciton dissociation and charge transport. As a result, the PY-DF-based all-PSCs achieved a higher PCE of 15.7% with simultaneously enhanced JSC (23.1 mA cm−2) and VOC (0.97 V) in comparison with PYT-based all-PSCs (PCE = 13.2%, JSC = 21.7 mA cm−2, and VOC = 0.93 V). This work provides a promising polymer acceptor for all-PSCs and shows that fluorination of linkers is a potential strategy to build high-performance polymer acceptors.
- This article is part of the themed collections: Journal of Materials Chemistry A HOT Papers and Honorary themed collection for Thomas P. Russell
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