TUNING THE BANDGAP FOR POLYMERIC SMART WINDOWS AND DISPLAYS

The band gap, and thus the optical properties, of polythiophene can be turned for use in electrochromic applications by attaching substituen ts to the monomers before polymerization. Electron donating substituen ts lower the bandgap, while steric interaction of side groups on adjac ent thiophene rings forces the conjugated backbone to twist and increa ses the band gap. By choosing the right combination, a polymer with sp ecific optical properties can be designed. Properties of interest for electrochromic applications, like oxidation potential, ionic conductiv ity and thermal stability, can also be improved by substitution. Poly( ethylene-dioxythiophene) (PEDOT) has shown to have interesting optical properties, increased ionic conductivity and a high thermal stability .