A Fast and Convenient Synthesis of Heterocycle-Based Polymers via Infrared Irradiation-Assisted Direct C–H Bond Arylation Polymerization in Quasi-Solvent-Free Conditions

The first synthesis of π-conjugated polymers for organic solar cells (OSCs) via infrared (IR) irradiation-assisted Pd-catalyzed direct C–H bond arylation polymerization (DArP) is reported. Reactions have been carried out under air and nonanhydrous conditions, in the presence of a very small amount (only 3.0 equiv) of cyclopentyl methyl ether (CPME). Donor–acceptor (D-A) heteroaryl-based π-conjugated polymers having different structures have been obtained in short reaction time. A more detailed investigation has been carried out for the donor polymer PBDB-T: three batches, synthesized via IR irradiation-assisted DArP and, for two of them, subjected to end-capping reactions, were tested in organic solar cells (OSCs), achieving maximum power conversion efficiency (PCE) of 4.8% in non-optimized device, which is comparable to commercially available PBDB-T used as reference (5.9%). Our results confirm that the experimental advantages of DArP reactions combined with the use of IR irradiation and the quasi-solvent-free conditions represent a straightforward and sustainable route to heterocycle-based polymers for organic solar cells.