Influence of the atmosphere control on the performance of thin-film transistors for applications in Flexible/Transparent circuitry

Abstract

This project proposal aims to study the effect of atmosphere control in the performance of thin-film transistors (TFTs) with the active layer comprised by organic semiconductors or by solution-processed metal-oxide semiconductors. The exposure of the active layer of organic field-effect transistors (OFETs) to oxygen and light causes a displacement in the threshold voltage and the off-current which, depending on the polarization condition of the electrodes, severely lowers the device overall performance. This effect is related to the formation of charge-carrier traps due to a reversible photo-oxidation process of the organic semiconductor. On the other hand, metal-oxide semiconducting films used in transparent TFTs show a huge variation in the conductivity and in the charge-carrier mobility on time when stored in inert atmosphere, causing an enormous instability on the operation of this kind of device, which is an undesirable effect for technological applications. The current project proposes a methodology to carry out a thorough study of the electrical behavior of OFETs and semiconducting oxides TFTs as a function of the exposure to the ambient atmosphere, specially to the oxygen concentration. We expect to be able to describe qualitatively and quantitatively the role of oxygen in the device operating mechanism and how the dynamics of the diffusion process in the active layer depends on parameters like temperature and time. (AU)