Acceptor‐Donor‐Acceptor Systems Based on Indacenodithiophene‐Extended Tetrathiafulvalene

Abstract

Here, we present a series of acceptor‐donor‐acceptor (A‐D‐A) conjugated molecules incorporating an indacenodithiophene‐extended tetrathiafulvalene (IDT‐TTF) as the central electron‐donating moiety, functionalized with various lateral electron acceptors. A key synthetic step was the Vilsmeier‐Haack formylation of the IDT‐TTF, providing the dialdehyde in quantitative yield. This compound was further used for the incorporation of dicyanovinyl and indanedione acceptors. UV‐vis absorption spectroscopy of the A‐D‐A compounds in solution revealed a broad absorption in the visible spectrum which is further red‐shifted when proceeding from solutions to thin films. Their cyclic voltammograms in solution showed a multi‐redox behavior – undergoing both oxidation and reduction events. Notably, the oxidation of these compounds unveiled the formation of intermolecular mixed‐valence and π‐dimer species, especially strong in the case of the indanedione‐containing derivative. Computational calculations helped us to identify the electronic transitions involved in the main absorption bands of these A‐D‐A compounds displaying different behaviors depending on the acceptor attached to the IDT‐TTF core. Finally, the potential of these compounds as donors in organic solar cells was investigated and the best performing solar cell exhibited a modest yet promising power conversion efficiency of 0.87%.