Thieno[2,3‑b]indole-Based Small Push–Pull Chromophores: Synthesis, Structure, and Electronic Properties

Small push–pull molecules were synthesized in high yields by connecting a N-methyl or N-phenyl substituted thieno­[2,3-b]­indole electron-donating block directly to a 2,2-dicyanovinyl or (1-(dicyanomethylene)-3-oxo-1-inden-2-ylidene)­methyl electron-withdrawing group. The effects of the N-substitution on thieno­[2,3-b]­indole and the nature of the electron-accepting group on the electrochemical, optical, and charge-transport properties were investigated by cyclic voltammetry, UV–vis spectroscopy, and the space-charge-limited current method, respectively. These results, together with the 1% power conversion efficiency of a bilayer solar cell prepared with the smallest compound of the series, show the potential of thieno­[2,3-b]­indole for organic electronics.