Optical properties of metal based transparent electrodes on polymer films

摘要

Transparent conducting electrodes on polymer films are important components in various kinds of flexible and mobile devices. Indium-tin oxide is the most important single layer transparent conductor. However, there are technical and economic restrictions for a large scale manufacturing of transparent electrodes below 20 Ω_(sq) based on this material. The main reason is the necessity of keeping a low substrate temperature during the deposition on polymer films. Therefore alternative technologies have been explored in the past. The most matured one is the replacement of ITO by a three layer stack consisting of a thin silver layer and two embedding transparent layers (IMI stack). The paper focuses on the simulation of the optical properties of IMI stacks. The key idea is the introduction of two interlayers into the calculation model. These interlayers represent the special properties of the boundary of the silver layers. The calculations based on this model agree with the measurement in an excellent way. The optical absorption spectra show a qualitative agreement with the behaviour of surface plasmons. Both the roughness of the layers and the dielectric constant of the embedding materials are represented in the model. Thus it is a valuable tool for the prediction of the optical performance in IMI stacks.