Hydrogen-bonded polyazomethines for efficient organic solar cells

Abstract

Hydrogen bonded azomethines were studied as building blocks for semiconducting polymers. The single-crystal X-ray diffraction analysis revealed that hydrogen bonds were formed between the carbamate hydrogens of side chains and azomethine nitrogen in building block CTB and CTP. The CTP also had additional weak hydrogen bonds between azomethine hydrogen and imine nitrogen of pyrazine. These hydrogen bonds improved the coplanarity of the building blocks and promoted π-electron delocalization and intermolecular stacking. Two conjugated polymers PBBDT and PPBDT based on the new building blocks were synthesized via a Stille cross-coupling reaction. These conjugated polymers showed broad and strong optical absorption in the visible region. The bulk heterojunction organic solar cells with PBBDT and PPBDT as electron donors and small molecular non-fullerene acceptors were studied. The solar cells based on PBBDT as the electron donor and Y6 as an electron acceptor showed a power conversion efficiency (PCE) of 10.2%.