Spectroscopic ellipsometry to precisely estimate the thickness for optimizing the performance of three-layer broadband transparent electrodes

This work utilized the optical properties of indium tin oxide/silver/indium tin oxide electrodes to set up the fitting range for spectroscopic ellipsometry (SE) analysis. Then, the SE fitting on the thickness and optical constants of each layer in several separate stages was investigated. In this way, the results suggest that the SE fitting can be able to converge rapidly and obtain the precise thickness of each layer. Experiment analysis shows that when the silver layer thickness was 8.5–11.5 nm, the sheet resistance of the uniform electrodes was < 8.5 Ω/sq, while the average transmittances were > 82.0% in the visible light region; the related Haacke indexes were > 22.0 × 10⁻³ Ω⁻¹. For photovoltaic application, when the silver layer thickness was 7.5–8.5 nm, the sheet resistance of the three-layer electrodes was < 9.0 Ω/sq, while their average transmittance was > 77.5%; the related Haacke indexes were > 9.0 × 10⁻³ Ω⁻¹. Comparing the SE results with experimental measurements, it is concluded that the uniformity of the silver layer and the stability of the sputtering system were the major factors affecting the optoelectronic performance of the three-layer electrodes.