A method for preparing an extended conjugated molecular assembly includes applying onto a surface of a substrate a first molecular compound G1-Molecule1-G2, where G1 includes a first functional group, G2 includes a second functional group, and Molecule1 includes a conjugated organic group bonded to G1 and G2, and reacting the first molecular compound with a second molecular compound G3-Molecule2-G4, where G3 includes a third functional group. G4 includes a fourth function group, and Molecule 2 includes a conjugated organic group bonded to G3 and G4, to form on the substrate an extended conjugated molecule G1-Molecule1-Molecule2-G4.