Transições inter e intra-cadeias em filmes de P3OT sintetizados eletroquimicamente

Abstract

In this work, we report the synthesis and an optical study of thin films of poli (3-octiltiophene) (P3OT). Our samples were prepared by the electrochemical technique, cyclic voltammetry. The P3OT films were synthetized on a conductive substrate of fluoride-doped tin oxide (FTO) through the oxidation of the monomer in the electrolytic acetonitrile solution of C8H20NBF4 (Tetra-fluoroborate of Tetraethylammonium). The thickness of the film produced is dependente on the number of voltammetric cycles. The UV-Vis measurements, as expected, demonstrate the dependence of the intensity of absorption on the thickness of the films. The photoluminescence (PL) spectra o four films show the presence of two diferente contributions attributed to the quinone and pristine structures. Furthermore, the PL spectra presente a contribution associated with vibrational modes (nom-radiatives). These optical actives vibrational modes were explained by Raman spectroscopy measurements. Through the atomic force microscopy technique, the thickness of the P3OT films were measured. They were observed through AFM images, clusters on the filmes surfaces that can be related to nucleation and growth processes 2D and 3D. The gap energy was obtained experimentally from absorption spectra, using na empirical method. The HOMO energy was calculated from the cyclic voltamogram. Through deconvolution of the Raman spectra, we observed an important correlation between the behavior of the polarons and bipolarons with the thickness of the films. Clusters that are formed on the surfaces of the films, observed through AFM images, indicate a decrease in molecular ordering and consequently na increase in phonon Generation, due to intra and inter-chain processes, causing na attenuation of photo-excited eléctron transfer and/or transport, providing non-radiative pathways during the relaxation processes, an effect that limits the performance of electrochemically grown P3OT if it is used as an active layer in optoelectronic devices.