An electronic device containing a polythiophene prepared by a metal halide-mediated coupling polymerization in an appropriate solvent, and which polythiophene is comprised of at least one monomer unit selected from the group consisting of 2,5-thienylene (or 2,5-thiophenediyl) (I), 2,5-thienylene (or 2,5-thiophenediyl) (II), and a divalent linkage D ##STR00001## wherein, for example, A is alkyl, alkoxy or derivatives thereof; B is a hydrogen atom, a small substituent like alkyl or alkoxy.