Boosting charge-transfer kinetics and cyclic stability of complementary WO3–NiO electrochromic devices via SnOx interfacial layer

The effect of interfacial layer (SnOx) on the performance of the complementary electrochromic devices (ECDs) was examined, revealing that the SnOx/WO3 bilayer cathodes could enhance the electrochromic performance, such as a superior long-term cycling stability over 10,000 cycles, a high coloration efficiency of 101.61 cm2 C−1 and a maximum transmittance modulation of 49.27%@633 nm. Moreover, compared with the single layer WO3, the SnOx/WO3 bilayer exhibited improved electrochemical activities and reaction kinetics. The probable explanation is that the introduced interfacial layer can boost the double injection of ions and electrons, balance the transport of ions and electrons, and protect the electrode from degradation by serving as a buffer layer during coloration/bleaching cycles. These results further provide a valuable insight for improving the electrochromic properties of the films instead of relying on conventional methods such as nanostructural or compositional control.