X-ray photoemission spectroscopy and Fourier transform infrared studies of dye molecule doped conducting polymer films

Abstract

Conducting polymer polythiophene (PT) films incorporated with dye molecule brilliant green (BG) were prepared by electrochemical doping and diffuse injection methods. The charge transfer and interaction between the doped molecule and PT polymer chains were investigated by analyzing the core-level energies and spectral profiles of the atomic components. Vibrational states of the doped dye molecule and the polymer backbone were also investigated by Fourier transform infrared (FTIR) RAS and FTIR transmission methods in order to examine the dopant configuration into the polymer chains in the hybrid films. In the case of BG doped films, X-ray photoemission spectroscopy (XPS) core-level analysis of S2p split indicates simultaneous doping of BG cation and HSO4− in the hybrid films prepared by electrochemically reduced and dye diffuse injection methods. The synthesized film samples were categorized into two types by the difference of S2p core-level energy shift. In the cationlike doped sample, the energy shift of the lower peak of S2p suggests the charge transfer between BG molecules and polymer chains creating a n type conducting polymer state. The orientation and configuration of the dopant BG molecule is discussed by assignment of the origin of the peak at 2000cm−1 which appeared only in the FTIR transmission spectrum of the BG-doped sample not observed in the FTIR RAS spectrum. The three possible cases of the origin of the peak are presented: Benzene out-of-plane mode, -NCS, and CCN-. According to those interpretations, three possible models of the BG configuration are suggested.