Synthesis and characterization of NiO-Ta₂O₅ nanocomposite electrode for electrochromic devices

NiO-Ta₂O₅ nanocomposite electrodes have been synthesized using an RF magnetron co-sputtering system, and their electrochemical and electrochromic properties have been compared with those of single NiO electrodes. Transmission electron microscopy results show that crystalline NiO nano-dots (3-8 nm in size) are embedded in a Ta ₂O₅ matrix. X-ray photoelectron spectroscopy results reveal the formation of Ni oxidized states (NiO) and Ta oxidized states (Ta ₂O₅). Electrochromic devices fabricated with the nanocomposite electrodes produce high optical modulation (41-95%), fast response time (colored: 3-4 s, bleached: 1 s), high coloration efficiency (ca. 30.5 cm² C^-1) and good durability, which are much better than those of ones made with the single NiO electrode.