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

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 x 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 cm(2) C-1. As the state-of-the-art, a large-area smart window (10 x 10 cm(2)) operable at 2 V is devised engaging WO3 coated Al_SnO2 electrode. The dual-functionality is demonstrated by employing four series-connected (5 x 4 cm(2), charging time approximate to 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.

Automated summary

The major drawbacks of electrochromic smart windows (ECSWs) for zero-energy buildings include excessive cost, insufficient optical modulation, and limited functionality. A solution to this problem is proposed by optimizing the deposition conditions for WO3 sputtering on a cost-effective Al-mesh overlaid with SnO2. The optimized ECSW exhibits ultra-high switching contrast, fast response and recovery time, good cyclic stability, and excellent coloration efficiency. A large-area smart window with dual-functionality and a device with a quasi-solid electrolyte are also developed.