Microstructural Effects on Nickel Oxide Film Properties in an Infrared Electrochromic Window for Shutter-Less Infrared Sensor Application

Infrared electrochromic devices (ECDs) were fabricated and characterized in mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) ranges. They consisted of three layers with two metal electrodes. The layers were an ion storage layer, an ion conducting layer, and an electrochromic layer. As an ion storage layer, NiO film was used. To ensure higher performance of the ECDs, the microstructural and electrochromic properties of NiO films deposited at various sputtering pressures were investigated using SEM, X-ray photoelectron spectroscopy, and cyclic voltammetry. In addition, WO 3 film and Ta 2 O 5 film were used in the two types of fabricated devices as a cathodic electrochromic layer and an ion conducting layer, respectively. The transmittance values in the MWIR and LWIR ECDs were measured in colored and bleached states. The measured transmittance ratios of the colored state relative to the bleached state were 0.66 and 0.72 in the MWIR and LWIR ranges, respectively.