Scalable Inkjet Printing of Electrochromic Smart Windows for Building Energy Modulation

Electrochromic smart windows are promising for green buildings due to energy efficiency, long optical memory effect, and tunable optical transmission. However, their wide application in buildings is impeded by challenges in scalability, cost-effectiveness, and limited optical contrast. Quantitative field study of energy savings enabled by electrochromic smart windows in buildings is also lacking. Herein, with the established inkjet printing procedures, electrochromic smart windows (900 cm²) are fabricated. With large optical contrast (≈60%), fast switching kinetics (t_c = 43 s, t_b = 70 s), and long optical memory retention (transmittance <10% for 7 h), when installed onto the outdoor testbed, these electrochromic smart windows can effectively reduce the internal temperature, especially in summer tropical weather. The energy savings brought by electrochromic smart windows are found to be higher in sunny days than in rainy days. Specifically in a sunny day, the heat gain reduction can reach 42.3%, and for a comfortable targeted indoor temperature of 25 °C, the cooling load savings can be 28.9% compared to regular double-glazing units-based reference testbed. This study demonstrates the scalability of inkjet printing technique for fabricating large-area electrochromic devices and the substantial energy savings obtained from testbed results.