Copolymerization of EDOT with Pyrrole on TiO₂ Semiconductor Films by One-Step Reaction, Structure-Dependent Electronic Properties, and Charge Conduction Models of the Composite Films

Abstract

We used the photoexcited TiO₂ films to initiate the copolymerization of 3,4-ethylenedioxythiophene with pyrrole, aiming to develop an organic/inorganic heterojunction. Specular reflection infrared spectroscopy analysis was used to monitor the process of polymerization and indicated that the copolymers directly grew on the TiO₂ substrate. Dissecting the copolymers with ultraviolet photoelectron spectroscopy revealed the evolution of the valence-band electronic structures. Moreover, the resulting copolymer/TiO₂ heterojunctions were investigated using electrochemical impedence and X-ray photoelectron spectroscopy. The Al/poly­(3,4-ethylenedioxythiophene-<i>co</i>-pyrrole)/TiO₂/ITO heterojunction device that was prepared from the hybrid film exhibited a conspicuous rectification. The heterojunction device was also explored with respect to the conduction models