Modulation of band gap and p- versus n-semiconductor character of ADA dyes by core and acceptor group variation

A series of ADA dyes was synthesized by Knoevenagel condensation reactions between dialdehydes of the electron-rich dithienopyrrole (DTP), cyclopentadithiophene (CPDT), carbazole (CAR) and fluorene (FL) moieties and the electron-poor CH-acidic indandione (IND) or 1,1-dicyanomethylene-3-indanone (DCIND) units, respectively. The UV/vis absorption spectra of the dyes cover a wide range of the visible spectrum from 450 to almost 700 nm in solution. Likewise, owing to differently balanced donor and acceptor strengths they may be applicable either as p- or n-type organic semiconductor materials in transistor and solar cell devices. As a proof-of-concept for dye vacuum-deposited organic thin film transistors (OTFTs) with either hole or electron mobilities of ∼0.1 cm2 V−1 s−1 depending on the HOMO/LUMO levels could be demonstrated.