Dependence of optical and electrical properties on Ag thickness in TiO2/Ag/TiO2 multilayer films for photovoltaic devices

Abstract We report on the formation of highly transparent and low conductance TiO 2 /Ag/TiO 2 multilayer films with high figure of merit (FOM). The optical and electrical properties of the multilayer films were investigated as a function of Ag layer thickness. As the Ag thickness increased, the transmission window narrowed and the transmittance was gradually lowered. The TiO 2 /Ag/TiO 2 multilayer films have the highest transmittance of 86.3–97% at 591 nm for different Ag thicknesses. The relationship between transmittance and TiO 2 thickness was simulated using the scattering matrix method to understand the abnormally high transmittance. As the Ag thickness increased from 15 to 25 nm, the carrier concentration of the TiO 2 /Ag/TiO 2 samples gradually increased from 6.18×10 21 to 1.07×10 22 cm −3 and the mobility also increased from 16.7 to 25.2 cm 2 /V-s. Meanwhile, the sheet resistance slightly decreased from 6.17 to 2.27 Ω⧸sq with the Ag thickness. The TiO 2 /Ag/TiO 2 multilayer (with Ag thicknesses of 17–21 nm) had Haacke׳s FOMs of 121×10 −3 –157.2×10 –3 Ω −1 .