Optical, Photoelectrochemical and Impedance Studies on Poly 3,3’ Dibromo, 2,2’ Bithiophene: Effect of Bromine as a Substituent at C-3 Position in 2,2’ Bithiophene Molecules
- Kasem K. Kasem
- Houria Sadou
- Anthony W. Jeffers
Thin films of poly 3, 3’ dibromo, 2,2’ biththiophene (PDBrBTh) and poly 2,2’ biththiophene (PBTh) on fluorine doped tin oxide electrode (FTO) were subjected to optical, electrochemical and impedance studies in various aqueous electrolytes. Both polymers showed electrochromic properties, where the neutral film at -1.0 V vs Ag/AgCl shows red color, and the oxidized (doped) film at positive potentials shows blue color. Optical studies indicated that PDBrBTh showed a greater optical band gap than that of PBTh. Our studies also showed that the presence of bromine as a substituent at the C-3 position of the thiophene ring causes a greater ionization potential (IP) than PBTh. PDBrBTh also shows closer values of refractive index(n), and real (εr,) and imaginary (εi) dielectric constants to that of PBTh at photon energies between 2.0eV and 3.0 eV. At lower photon energy PDBrBTh showed lower optical conductivity than Br-free PBTh. Study also indicated that PDBrBTh is much less photoactive that PBTh. Electrochemical impedance spectroscopic studies (EIS) revealed that PDBrBTh possesses less relaxation time, and less double layer capacitance (Cdl) in dark and under illumination.
- Albert JohnEditorial Assistant