Temperature‐Dependent and Aggregation‐Breaking Strategy for Benzodifuran‐Constructed Organic Solar Cells

Abstract

Great efforts have been devoted to semiconductive polymers based on the benzo[1,2‐b:4,5‐b’]dithiophene (BDT) unit, and great progress has been achieved in organic solar cells, whereas the analogue core benzo[1,2‐b:4,5‐b’]difuran (BDF) has the similar extended planar structure, and the electronic structure gets less development in the photovoltaic system. Herein, a novel BDF core‐based copolymer PBDFTz‐SBP is synthesized, which decorates with two 2D extended biphenyl side chains and shows a relatively small polymer segments distortion and strong intermolecular π–π interaction in relation to the BDT‐based polymer. Using this polymer, an aggregation‐breaking strategy to suppress the trend of self‐aggregation of polymers’ segment is proposed, which obtains an appropriate phase separation and forms favorable bicontinuous interpenetrating networks for charge transport. It is found that PBDFTz‐SBP:ITIC achieves an excellent power‐conversion efficiency (PCE) of 12.42% with an open‐circuit voltage (VOC) of 0.89 V, a short‐circuit current density (JSC) of 18.56 mA cm−2, and a high fill factor (FF) of 75.19% when the spin‐coating solution is 120 °C, which is higher than that of PBDTTz‐SBP:ITIC‐based devices even under optimized conditions. This proposed strategy may be a good choice for the BDF unit to construct the donor (D)–acceptor (A) type polymers and surpass the counterpart BDT‐based photovoltaic materials and obtain a state‐of‐the‐art PCEs.