Eradicating β-trap induced bleached-state degradation in amorphous TiO2 electrochromic films

Titanium dioxide (TiO2) draw great attention in developing electrochromic devices due to its low cost, dual-band optical modulation and wide potential window complementary to other EC films. Akin to other electrochromic oxides, TiO2 suffers from the tradeoff between cycling stability and large optical modulation because of the ion trapping effect. In this paper, we find formation of beta-traps can be prevented through adjusting the applied duration time at high potential, thus beta-traps induced bleached state degradation in amorphous TiO2 films can be eradicated. More importantly, we show the formed beta-traps locate at the TiO2/electrolyte interface, and are in-dependent of the employed electrolyte systems. The TiO2 based full electrochromic devices confirm beta-traps can be suppressed in a full device fashion. This work paves the way to understand the electrochromic performance degradation for oxide films upon square wave cycling and lays the foundation for adaptation in EC devices.