Thermal stability enhancement of SnO2/Ag/SnO2 transparent electrodes using Ni-doped Ag

This study aims to optimize the Ni concentration of the Ag–Ni metal layer and the annealing temperature of the SnO2/Ag–Ni/SnO2 multilayer structure required for excellent electrical and optical properties. We sputtered SnO2/Ag–Ni/SnO2 multilayer thin films with various Ni compositions, followed by annealing at 100–300 °C (metal layer) or 400–600 °C (oxide/metal/oxide multilayer). To evaluate changes in the thermal stability associated with various Ni concentrations in the Ag layer, UV-VIS spectroscopy, four-point probe measurements, XPS, and FE-SEM are used, and a cross-section of the multilayer structure is analyzed before and after annealing using XPS. On annealing, the SnO2/Ag–Ni/SnO2 multilayer structure shows improved performance due to defect reduction, but without Ni, the structure is degraded by the Ag and oxygen diffusion into adjacent layers on high-temperature annealing. The SnO2/Ag–Ni (3.2 at%)/SnO2 multilayer structure annealed at 550 °C shows the highest figure of merit of 23.8 × 10−3 Ω−1.