The optical analyses of the multilayer transparent electrode and the formation of ITO/Mesh-Ag/ITO multilayers for enhancing an optical transmittance

Abstract

As a highly conductive and transparent electrode, ITO/Ag/ITO multilayers are fabricated using an in-line sputtering method. Optimal thickness conditions have been investigated in terms of optical transmittance and electrical conductance. Considering the optical properties, the experimental characteristics are analyzed based on theoretical phenomena and compared with the simulated results. The simulations are based on the finite-difference-time-domain (FDTD) method in solving linear Maxwell equations. The results showed that ITO/Ag/ITO structures with respective thicknesses of 39.2 nm/10.7 nm/39.2 nm are most suitable with an average transmittance of 87% calculated for wavelengths ranging from 400 to 800 nm and a sheet resistance of about 7.1 Ω∕□. However, even with the optimum thickness conditions of the ‘ITO/Ag/ITO’ multilayers, the transmittances on some ranges of the visible wavelength were much lower than those of a single ITO layer. In order to improve the transmittance, Ag layer was formed with mesh structure. The transmittance and the sheet resistance in the ITO/Mesh-Ag/ITO multilayer structure were analyzed depending on the open ratio. As a result, a trade off in the open ratio was necessary in order to obtain the transmittance as high as possible and the sheet resistance as possible low. By the experiments, we found out that the transmittance was nearly same as the single ITO layer and the sheet resistance was about 30 Ω∕□ when the open ratio was about 85%.