Realization of highly transparent and low resistance TiO2/Ag/TiO2 conducting electrode for optoelectronic devices

The effect of TiO2 thickness on the optical and electrical properties of TiO2/Ag/TiO2 multilayer films deposited on glass substrates was investigated. The as-deposited TiO2 samples were found to be amorphous. The transmission window became wider and gradually shifted toward lower energies as the TiO2 thickness increased from 10 to 50 nm. In particular, the TiO2/Ag/TiO2 (40 nm/18.8 nm/40 nm) multilayer film exhibited a transmittance of ~ 95% at 550 nm. Incrementally increasing the TiO2 thickness to 50 nm gradually decreased the carrier concentration to 6.1×1021 cm−3, while the charge mobility varied from 22.3 to 20.4 cm2 V−1 s−1. In addition, when increasing the TiO2 thickness to 50 nm, the samples showed similar sheet resistances of 3.9–4.4 Ω/□, but the resistivity increased by a factor of 3.8. Haacke׳s figure of merit (FOM) was calculated for the samples and plotted as a function of TiO2 thickness; the TiO2 (40 nm)/Ag (18.8 nm)/TiO2 (40 nm) multilayer yielded the highest FOM of 159.9×10−3 Ω−1.