Improved electrochromic devices with an inorganic solid electrolyte protective layer

The durability problem of electrochromic devices (ECD) in Li ion-conducting electrolytes may be due to the degradation of the ECD electrode matrix and irreversibly reacting Li ions during cycling. With this hypothesis, we investigated the performance of WO₃ film with an inorganic solid electrolyte, lithium phosphorous oxynitride (LiPON), protective layer and of the ECD composed of WO₃ and V₂O₅ with a LiPON protective layer prepared by RF magnetron sputtering. WO₃ and ECD (glass/ITO/V₂O₅/LiPON/electrolyte/LiPON/WO₃/ITO/glass) with a protective layer not only showed improved durability with continuous potential cycling, but also demonstrated a good memory effect under voltage-off, good response times and high coloration efficiency (CE). Our results demonstrated that LiPON layers are electrochemically stable, enhance the electrochromic properties in Li ion-conducting electrolytes, and can be used as a protective layer for ECD.