Analysis of the optical properties of poly(3‐octylthiophene) partially dedoped

Abstract

In this work, poly(3‐octylthiophene) (P3OT) films were synthesized electrochemically in non‐aqueous media through the oxidation of the monomer, (3‐octylthiophene), using a standard three‐electrode cell in acetonitrile with 0.05 mol L−1 LiClO4 or 0.05 mol L−1 Et4NBF4. The polymeric films were deposited on fluorine tin oxide (FTO). The partial dedoping was obtained in NH4OH solution, providing a good chemical stability of the formed material. The films obtained through this method have been characterized by Fourier‐transform infrared spectroscopy (FT‐IR), electron paramagnetic resonance (EPR), UV–Vis absorption, and photoluminescence (PL) spectroscopy. The FT‐IR and EPR spectra together gave the results that led to characterization of two structures (pristine and non‐pristine forms of thiophene rings) while forming the P3OT polymer chain. These results were associated with the stabilization of pristine chains and mixed chains (non‐pristine structures) in the polymeric film. Their bands in the PL spectra are wide and asymmetric and their adjustments by Gaussian functions was necessary; this was the main indication that there are two distinct contributions to the emission spectra. These two contributions are attributed to the emission by mixed chains (Gaussian centered at higher energy) and by pristine chains (Gaussian of lower energy) present in the formed polymeric material. Copyright © 2010 John Wiley & Sons, Ltd.

Electrochemical Deposition of P3AT Films Used as a Probe of Optical Properties in Polymeric System

“…For the EtNBF02 ilm, a well-resolved absorbance band at ~775 nm is also observed. This band is the result of the interaction between the BF 4 -anion and P3DDT polymer chains [8,9,20]. Similar results are observed in diferent P3AT polymers [35][36][37].…”

“…In addition, great E g can be correlated with the high doping of P3DDT chains producing higher polymer quinone form. It was showed by Therézio et al [8,19] studied that the energy gap in doped P3AT ilms increases. Therefore, in our study, we also recommend the P3DDT ilms with lesser deposition cycles and lesser doped or lower gap energy which displays major polymer chains in the pristine form.…”

“…We demonstrated an easy and eicient alternative method to control the processing of organic optoelectronic devices. In that context, Therézio et al in [8] show two distinct structures of the polymer chain morphology shifting the band gap to higher energies, using an optical analysis of P3ATs ilms electrochemically prepared. Moreover, reference [9] also indicated that it is possible to analyze the polarization of the emited light by the supporting electrolyte efects on the emission properties of P3ATs ilms.…”

“…The P3ATs chemically synthesized presented an energy gap of around 1.93 eV (640 nm) [5,6,[8][9][10][11][12]. Interestingly, this energy gap independent of the size of the alkyl lateral chain because it is not conjugated.…”

“…Since the physical-chemistry properties and investigation of organic active layers, such as P3ATs thin solid ilms, can elucidate the development of new optoelectronic devices [16][17][18]. Interface efects cause signiicant quenching of excited carriers and it is commonly investigated by conventional spectroscopic techniques [15,19], such as ultraviolet-visible absorption (UV-Vis), photoluminescence (PL), photoluminescence excitation (PLE), vibrational spectroscopy (FT-IR and RAMAN) [8,12,20,21] and the morphological technique of atomic force microscopy (AFM) [22][23][24]. In the case of energy transfer processes of excited carriers, the analysis of polarization of emited light can be directly correlated with polymeric chain position parallel to the direction of the transition dipole moment [25][26][27].…”