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

Titanium dioxide (TiO 2 ) 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, TiO 2 suffers from the tradeoff between cycling stability and large optical modulation because of the ion trapping effect. In this paper, we find formation of β-traps can be prevented through adjusting the applied duration time at high potential, thus β-traps induced bleached state degradation in amorphous TiO 2 films can be eradicated. More importantly, we show the formed β-traps locate at the TiO 2 /electrolyte interface, and are independent of the employed electrolyte systems. The TiO 2 based full electrochromic devices confirm β-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.