Color-Neutral Smart Window Enabled by Gradient Reversible Alloy Deposition

Reversible metal electrodeposition (RME)-based smart windows can realize large solar heat gain coefficient (SHGC) modulation, where Zn-RME emerges as an intriguing option with high theoretical coloration efficiency (CE), cost effectiveness, and color neutrality. Herein, Cu2+ was selected as electrolyte additive to lower the activation energy and homogenize the electrical field distribution during metal plating, forming gradient CuZn alloy nanoparticles via reversible alloy electrodeposition (RAE). Compared to Zn-RME, the CuZn-RAE electrode can achieve extremely low transmittance (0.01%) and color neutrality (chroma C* = 5.8) within 2 min, large transmittance modulation (82%), fast switching times (tc = 8 s, tb = 18 s), higher CE, elevated memory effect, and extended cycling stability. Additionally, a tinted CuZn-RAE device can effectively block infrared heat and reduce surface temperature by 7.1 °C, and the insulating glass unit (IGU) modeled with a CuZn-RAE device offers large solar heat modulation with ΔSHGC of 0.448, showing great application potential toward dynamic smart windows.