Affordable Smart Windows with Dual‐Functionality: Electrochromic Color Switching and Charge Storage

Abstract Excessive cost, insufficient optical modulation, and limited functionality are major drawbacks that presently exist in electrochromic smart windows (ECSWs) that are the backbone of zero‐energy buildings. Herein, a solution toward this niche is provided by optimizing various deposition conditions for WO₃ sputtering on crackle lithographically fabricated, cost‐effective Al‐mesh overlayed with SnO₂. Ultra‐high switching contrast of 90% is accomplished by a decisive choice of parameters i.e., deposition power (5 W cm⁻²), oxygen flowrate (46 sccm), pressure (2.7 × 10⁻² mbar), and film thickness (530 nm) that are imperative for achieving enhanced oxygen deficiency and film porosity. The ECSW displays fast switching with response and recovery time of 11 and 5 s, respectively, which are nearly twice as fast as control ITO‐based device. Additionally, the film holds good cyclic stability with an excellent coloration efficiency of 47 cm² C⁻¹. As the state‐of‐the‐art, a large‐area smart window (10 × 10 cm²) operable at 2 V is devised engaging WO₃ coated Al_SnO₂ electrode. The dual‐functionality is demonstrated by employing four series‐connected (5 × 4 cm², charging time ≈1.5 min) devices to operate a display for 70 min. A device with a quasi‐solid electrolyte is also fabricated, exhibiting improved cyclic stability beyond 2000 cycles.