Synthesis of 2,2′-[2,2′-(arenediyl)bis(anthra[2,3-b]thiophene-5,10-diylidene)] tetrapropanedinitriles and their performance as non-fullerene acceptors in organic photovoltaics

Three novel molecules based on thiophene-fused 11,11,12,12-tetracyano-9,10-anthraquinodimethane (TCAQ) units linked through functionalized pi-conjugated arene bridges are synthesized by three-step sequence of Sonagashira coupling, double thioannulation and Knoevenagel condensation. The energy of their frontier orbitals shows that these molecules are suitable for replacing fullerenes as electron acceptors in composites with conjugated donor polymers used in organic photovoltaics (OPV). The composite of polymer donor PCDTBT with fluorene-linked thiophene-fused TCAQs demonstrates good solubility in organic solvents and bulk heterojunction morphology with characteristic donor and acceptor domain size of several tens of nanometers, favourable for photoelectric conversion. This composite also exhibits prominent light-induced EPR signal indicating efficient photoinduced free charge generation. OPV devices based on this composite were fabricated by vacuum-free method. They show photoelectric conversion with maximum PCE of 0.71%.