Ion conductor barrier height for the switching time improvement of all-thin-film inorganic complementary electrochromic devices

Abstract

In this study, an all-thin-film inorganic complementary electrochromic device (ECD) with the lithium doping zirconium dioxide (ZrO2:Li) ion conductor layer has demonstrated for the lower cost ECD applications. Even though the ZrO2:Li has demonstrated a lower lithium (Li) ion conductivity of 1.62 × 10−8 S/cm and ion mobility of 8.67 × 10−12 cm2/Vs, the switching characteristic of the ECDs has been improved. According to the refractive index measurement, the ion conductor ZrO2:Li with the higher refractive index value is also indicated a higher energy bandgap material. As a result, the possible mechanism is due to the electron energy barrier height 1.2 eV between the interface of electrochromic layer tungsten oxide (WO3) and ion conductor layer ZrO2:Li. Besides, the induction of an electric field between the WO3 and high bandgap ZrO2:Li material interface also accelerates the Li ion transported through the interface. Furthermore, the ZrO2:Li with the lower ion conductivity and mobility is due to the dense material structure, which is verified by the cross-sectional field emission scanning electron micrograph profile. Additionally, the dense material structure has also provided better surface morphology for thin-film device structures with the layer-by-layer deposition process.