Análise fotofísica e morfológica da interface polimérica PAni/P3HT sintetizada eletroquimicamente

Abstract

In this work, we study the Polyaniline(Pani)/Poly(3-hexylthiophene) (P3HT) interface to understand the behavior of carriers and the possibility for future applications in optoelectronic devices. Pani, the emeraldine salt, was electrochemically synthesized by cyclic voltammetry in sulfuric acid as a supporting electrolyte in an aqueous solution on a transparent FTO (fluorine-doped titanium oxide) substrate. Then the P3HT was deposited by chronocoulometry on the PAni, the supporting electrolyte used was LiClO4 at a concentration of 0.3M in acetonitrile. Spectroscopic and morphological characterizations were performed using various techniques such as UV-Vis absorption, Photoluminescence (PL), photoluminescence excitation (PLE), Emission Ellipsometry (EE), Atomic Force Microscopy (AFM), and Electrochemical Impedance Spectroscopy (EIS). A large Stokes shift was observed, which indicates a higher probability of non-radiative transitions. In the PL spectra of the Pani/P3HT interface, there is a greater contribution related to the emission of P3HT pristine chains. EE showed that Pani’s emission is about 50% vertically polarized, which makes it difficult to energy transfer between the polymer chains. This emission polarization is maintained at the Pani/P3HT Interface, and as the emission at the interface is mostly from the P3HT, it is concluded that there is an energy transfer from the photo-excited carriers of the PAni chains to those of the P3HT. In contrast, the AFM shows that the PAni/P3HT interface presents an irregular growth of P3HT over the PAni, forming clusters, which in principle should compromise the energy transfer through the P3HT chains. Finally, the interface shows promise in terms of energy transfer between the PAni and P3HT chains for future applications.