Optimization of oxide materials in oxide-metal-oxide(OMO) electrodes for flexible electrochromic devices

Abstract

The use of the oxide-metal-oxide (OMO) structure is one of the key strategies for enhancing the sheet resistance and flexibility of large-area flexible displays. Various combinations of OMOs with indium-tin oxide (ITO) and zinc-tin oxide (ZTO) for the oxide layer and a metal layer with silver (Ag) are discussed. Four-types of OMO are fabricated and the electrical characteristics of each are confirmed through electrochromic devices. The type of oxide layer affects the electron transfer from the metal layer to the oxide layer. Thus, the position of the oxide layer depends on the band structure and should be considered to achieve better performance. The ITO/Ag/ITO (IAI) type of electrode demonstrated the lowest sheet resistance at an average of 8 Ω sq −1 as well as high transparency above 80% at a wavelength of 650 nm. Electrochromic transparency differences between the bleached and colored states were maintained at 52.1% after 200 cycles, and the times required for coloration and bleaching were 0.5s and 8.1s, respectively. A stable redox reaction was confirmed after storing the devices at −30 °C and 85 °C for 18 h. • Fabrication of various OMO electrodes for flexible electrochromic devices is possible. • Relationship between the top-layer and bottom-layer of OMO electrode are investigated. • Flexible large-area electrochromic devices are tested within long-term cycles and harsh temperature.