Improved performance of all-thin-film electrochromic devices with two ZrO2 protective layers

Abstract

To improve the overall electrochromic properties of the all-thin-film electrochromic devices (ECDs), the seven-layer-structure ITO/NiOx/ZrO2/ZrO2:H/ZrO2/WO3/ITO were fabricated by DC reactive magnetron sputtering at room temperature. The X-ray diffraction and ultraviolet-visible (UV) optical spectra were characterized to elaborate the effects of ZrO2 protective layers on the optical modulation, cycling stability, and the weather fastness of the electrochromic devices. At the same time, the devices without ZrO2 protective layer were prepared in the same method as comparison. In XRD analysis, the insertion of hydrogen atoms does not bring significant distortion inside the crystalline structure of ZrO2 film which ensures that ZrO2 and ZrO2:H film can match well. The transmittance spectra show that the optical modulation of both ECDs was roughly identical which demonstrates no color effect of ZrO2 film on electrochromic device. After cycling for 1000 cycles, the attenuation rate of optical modulation of devices with protective layer is 31.6% which is far less than that of devices without protective layer (63.7%). After storage for 18 days in natural conditions, the protective layer can guarantee that electrochromic device steadily works with the △T of around 43.0% in the first 100 cycles; whereas, the △T of the device without protective layer decreases rapidly from 51 to 14.7%. Thus, these ZrO2 protective layers show considerable improvements in continuous cyclic stability and the natural self-attenuation performance.