Ionic Storage Materials for Anodic Discoloration in Electrochromic Devices

The ion storage layer in electrochromic devices (ECDs) stores protons or lithium ions to provide electrochemical stability and extend cycle durability. This paper reports on the performance and stability of ECDs paired with various ion storage layers (NiO, V2O5, and IrO2 films). The complementary ECD using a V2O5 ion storage layer presented the fastest response time, but the lowest optical contrast. In addition, the ECD using an IrO2 ion storage layer proved the most effective as an ion storage layer, due to its high optical modulation ability capability and long-term stability. Chronoamperometry analysis revealed that IrO2-based ECD (glass/IZTO/WO3/liquid electrolyte/IrO2/IZTO/glass) can be highly effective in modulating optical transmittance, as indicated by T = 61.5% (from Tbleaching (69.6%) to Tcoloring (8.1%)) and switching times of 5.3 s for coloring and 7.3 s for bleaching at 633 nm.