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

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.