Enhancing Electrochromic Behavior of Nickel Oxide Thin Films by Optimizing Oxygen Concentration During Room Temperature Reactive Sputtering

Abstract Electrochromic (EC) displays are those that incorporate materials that change color due to an applied potential. For the large‐scale application of these materials, essential factors are high cyclic stability, short response time, high coloration efficiency, and good optical contrast. These factors are influenced by the thin film deposition conditions, especially for inorganic metal oxide‐based EC materials. In this paper, we report on the role of oxygen gas flow rate (9–15 standard cubic centimeters per minute (SCCM)) on the EC behavior of nickel oxide (NiO) thin films deposited by direct current (DC) reactive magnetron sputtering at room temperature. The deposited NiO film is polycrystalline in nature, and Raman spectroscopy confirms the presence of both Ni 2+ and Ni 3+ states. The deposited thin films show an excellent EC performance, where transmittance has increased to 93.2% for the optimized 12 SCCM oxygen flow rate, with a coloration efficiency of 16.5 cm 2 C −1 and with fast‐switching times of 2.5 s and 2.4 s to the colored and bleached states, respectively. The film shows excellent cyclic stability over 1000 chronoamperometry cycles. This work provides a fundamental understanding of the role of oxygen flow rate during deposition on the EC performance of NiO films.