Interface engineering of SnO2 to enhance the cycle stability of WO3 and Prussian blue for complementary electrochromic smart windows and energy storage

The interface mismatch between electrochromic materials and conductive layer seriously affects the cycle stability of electrochromic smart windows (ESW). However, it is difficult to improve the interface matching at the same time because of the different physical and chemical properties of anode and cathode materials . In this work, SnO 2 nanosheets are used as the interface modification layer between electrochromic materials and conductive layer. SnO 2 interface engineering significantly can improve the cycle stability of WO 3 film and Prussian blue (PB) film. The WO 3 /SnO 2 -PB/SnO 2 complementary ESW exhibits a high optical modulation of 60.2 % at 633 nm, fast response time (bleached/colored time = 8.5/2.5 s), and coloration efficiency of 91.7 cm 2  C −1 . The WO 3 /SnO 2 -PB/SnO 2 device can still maintain an optical modulation of 45.2 % after 2000 cycles, suggesting excellent long cycle stability. And the device shows the energy storage of 5.06 mF cm −2 at 0.1 mA cm −2 , which can improve energy efficiency. The excellent electrochromic properties and energy storage suggests that SnO 2 interface engineering has a good application prospect in multi-functional ESW with excellent cycle stability.