A 3‐Fluoropyridine Manipulating the Aggregation and Fibril Network of Donor Polymers for Eco‐Friendly Solution‐Processed Versatile Organic Solar Cells

Abstract The development of eco‐friendly solvent‐processed organic solar cells (OSCs) suitable for industrial‐scale production should be now considered the imperative research. Herein, asymmetric 3‐fluoropyridine (FPy) unit is used to control the aggregation and fibril network of polymer blends. Notably, terpolymer PM6(FPy = 0.2) incorporating 20% FPy in a well‐known donor polymer poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl‐3‐fluoro)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b’]dithiophene))‐alt‐(5,5‐(1’,3’‐di‐2‐thienyl‐5’,7’‐bis(2‐ethylhexyl)benzo[1’,2’‐c:4’,5’‐c’]dithiophene‐4,8‐dione)] (PM6) can reduce the regioregularity of the polymer backbone and endow them with much‐enhanced solubility in eco‐friendly solvents. Accordingly, the excellent adaptability for fabricating versatile devices based on PM6(FPy = 0.2) by toluene processing is demonstrated. The resulting OSCs exhibit a high power conversion efficiency (PCE) of 16.1% (17.0% by processed with chloroform) and low batch‐to‐batch variation. Moreover, by controlling the donor‐to‐acceptor weight ratio at 0.5:1.0 and 0.25:1.0, semi‐transparent OSCs (ST‐OSCs) yield significant light utilization efficiencies of 3.61% and 3.67%, respectively. For large‐area (1.0 cm²) indoor OSC (I‐OSC), a high PCE of 20.6% is achieved with an appropriate energy loss of 0.61 eV under a warm white light‐emitting diode (3,000 K) with the illumination of 958 lux. Finally, the long‐term stability of the devices is evaluated by investigating their structure–performance–stability relationship. This work provides an effective approach to realizing eco‐friendly, efficient, and stable OSCs/ST‐OSCs/I‐OSCs.