Performance assessment of TCO/metal/TCO multilayer transparent electrodes: from design concept to optimization

Versatile multilayer designs based on a transparent conductive oxide (TCO)/metal/TCO structure are proposed to overcome the trade-off between their electrical and optical properties. The overall performance of the investigated multilayer designs based on ZnO/metal/ZnO and indium tin oxide (ITO)/metal/ITO structures is compared based on their Haacke figure of merit (FoM) at λ = 550 nm. The influence of both the thickness and position of the inserted silver and gold ultrathin metallic layer (ML) on the electrode FoM is studied. To address the trade-off between transparency and conductivity, a new hybrid approach combining the proposed multilayer designs and particle swarm optimization is conducted. The optimized multilayer design with the ITO/Ag/ITO structure is found to open a new avenue towards the achievement of ultrahigh FoM values of 135 × 10⁻³ Ω⁻¹, superior to those found to date, with a high transmittance above 95% and a reduced sheet resistance of 4.7 Ω × sq⁻¹. This enhancement can be attributed to the dual effects of the enhanced light management induced by effectively modulating the ML geometry and the reduced sheet resistance. The proposed design methodology therefore bridges the gap between high transparency and low sheet resistance, becoming suitable for use in high-performance optoelectronic applications.