We report a small-molecule electron-acceptor based on 2-vinyl-4,5dicyanoimidazole [VinazeneÔ] for use in solution processed organic solar cells. The material has a favourably located LUMO level of À3.6 eV and absorbs strongly in the visible spectrum up to 520 nmattractive properties compared to the widely used acceptor (6,6)phenyl-C 60 -butyric acid methyl ester (PCBM). The Vinazene derivative was blended with a poly(2,7-carbazole) donor-chosen for its complementary absorption range and comparatively high-lying HOMO level of À5.6 eV-and incorporated into bulk heterojunction devices. The influence of the donor/acceptor composition and annealing temperature on device performance were then investigated. The best performing devices exhibited reasonable power conversion efficiencies of 0.75% and open-circuit voltages of more than 1.3 V, substantially higher than previously reported devices using small molecule acceptors.

The high-yield syntheses of a new class of n-type conjugated materials based on the Heck coupling of 2-vinyl-4,5-dicyanoimidazole with selected dibromoaromatics is reported. The resultant materials have tunable HOMO−LUMO levels and photoluminescence ranging from deep blue to red. Solution-processed organic solar cells with external quantum efficiencies exceeding 14% could be prepared by blending selected novel materials with poly-(3-hexylthiophene) (P3HT).

We report the Heck coupling of 2-vinyl-4,5-dicyanoimidazole (vinazene) with selected di- and trihalo aromatics in an effort to prepare linear and branched electron-accepting conjugated materials for application in organic electronics. By selecting the suitable halo-aromatic moiety, it is possible to tune the HOMO-LUMO energy levels, absorption, and emission properties for a specific application. In this regard, materials with strong photoluminescence from blue --> green --> red are reported that may have potential application in organic light-emitting diodes (OLEDs). Furthermore, derivatives with strong absorption in the visible spectrum, coupled with favorable HOMO-LUMO levels, have been used to prepare promising organic photovoltaic devices (OPVs) when combined with commercially available semiconducting donor polymers.