Pre-aggregation Manipulation of Polymer Donor Using Guest Plasticizers for Developing Nonhalogenated Green Solvent Processed High-performance Organic Solar Cells

Recent advances in non-fullerene acceptors like Y6 have pushed the power conversion efficiencies (PCEs) of organic solar cells (OSCs) above 19%. However, the harsh fabrication conditions, such as the use of the highly volatile chloroform solvent, are not suitable for large-area printing technologies and environmental standards. Here, a third component (guest) BTP-3Si-4F is designed and synthesized with siloxane repeating units in side chains. The guest BTP-3Si-4F could act as a plasticizer, which inhibits the pre-aggregation behavior of PM6 in nonhalogenated (toluene) solution and enables the active layer to form a morphology with suitable phase separation scale. Therefore, BTP-3Si-4F blended with PM6:Y6 and PM6:BTP-eC9 deliver the highest PCEs of 16.92% and 17.64%, respectively. The results demonstrate controlling the pre-aggregation behavior of donor via guest molecules is an effective and universal way to achieve efficient OSCs in non-halogenated solution.