Optical, Photoelectrochemical, and Electrochemical Impedance Studies on Photoactive Organic/Inorganic/Interface Assemblies of Poly 2,2 Bithiophene/Poly 3-(2-Thienyl) Aniline (PThA)/TiO<sub>2</sub>

Abstract

Particles of TiO 2 modified with poly 3-(2-thienyl) aniline (PThA) and occluded in poly 2,2 bithiophene (PBTh), were subjected to optical, electrochemical impedance spectroscopic (EIS) and photoelectrochemical (PEC) investigation in aqueous, acetate, citrate, and phosphate electrolytes. EIS studies revealed that the assembly film of TiO 2 /PThA/PBTh possess porous-type structure. They also confirmed the approximate value of E f obtained from electrochemical studies. Both EIS and optical studies indicated that ac conductivity is much greater than dc conductivity. Guided by the properties of PBTh, no large changes in the energy band structure occurred due to occlusion of TiO 2 in PBTh films. Occlusion of TiO 2 /PThA into the network structure of PBTh inhibits the energy dissipation process and impeded charge polarization process of the material. Photoelectrochemical outcome suggested possible band alignments between the organic film and TiO 2 and formation of hybrid sub-bands. Inclusion of TiO 2 in the thiophene-based polymers enhanced the charge separation and consequently charge transfer processes and widen the absorption in visible light range.