Energy structure of thin films of carbazole derivatives with metal electrodes

Abstract

Study of charge carrier transport in organic electroluminescent devices, organic photovoltaic devices, and organic field-effect transistors is one of the most important points. In order to realize comparable electron and hole transport in thin organic films with electrodes the energy structure of such devices are of great importance. In this work, we have studied electrical properties and energy structure of two carbazole derivatives. The threshold energy of photoconductivity quantum efficiency is 2.90 eV and optical energy gap is 3.3 eV in thin films is obtained. The values of work function of ITO, Au, Cu and Pd electrodes are energetically close to conductivity level of holes and holes injection dominates from electrodes. In these thin films local trapping states of holes are situated at holes conducting level. When electrode is Al layer the local shallow trapping states for electrons at Et = 0.10 eV for compound 1 and at Et = 0.18 eV for compound 2 are determined.