Síntese e caracterização de óxido de grafeno reduzido e sulfonado via sal arildiazônio de ácido sulfanílico para aplicações em eletrônica orgânica

Abstract

Among several existing materials that can be applied in technology, Graphene Oxide (GO) and their derivatives can be applied in many types of devices, for example, Organic Photovoltaic Devices (OPVs). In this context, GO can be used as Hole Transporting Layer (HTL) with the purpose of improving the charge transport and extraction dynamics to the anode. However, due to the GO behaves as an insulator their thin films present a high sheet resistance (RS, causing a strong dependence between the efficiencies of the OPVs and the GOs films thicknesses. To work-around this issue, GOs can be reduced, giving origin to Reduced Graphene Oxides (rGOs), these materials that present typical RS with an order of magnitude around 104 to 105 Ohm/sq. Nonetheless, these procedures tend to decrease the work function (WF) of the rGOs to values that make it impossible to apply them as HTL. In order to guarantee high WFs and low RS, rGOs can be reduced and functionalized/doped with functional groups that present high electronegativity. In this work, colloidal dispersions of rGO were functionalized with sulfonate group (ph-SO3H), giving origin to the sulfonated reduced graphene oxide (SrGO). Carbonyl-rich GO was synthesized according to a modified Hummers method previously develop by Nano group. The S-rGO was prepared by using a chemical route based on the reaction of the aryl diazonium salt of sulfanilic acid with the rGO dispersions. The GO, rGO and S-rGO samples where characterized by a set of spectroscopic techniques that allowed to confirm the introduction of the ph-SO3H groups in rGOs structures. The electrical properties of these materials in thin film were also analysed, and the results showed that the ph-SO3H groups contribute to the increase of the RS. In addition, preliminary studies of the structures involved in this study were carried out by using molecular computational simulation PM3, in collaboration with the group of Simulação Computacional da UFJF. The central idea of this part of the work was to evaluate the changes of the energy levels occurred in the S-rGO. Finally, OPVs were fabricated using S-rGO film as HTL, the preliminary results showed that there is a tendency to eliminate the dependence of the thickness of these films with the OPVs efficiencies.