A Redox‐Mediated Stepwise Reversible Electrodeposition Smart Window

The optical tunability of electrochromic smart windows enables heat regulation, providing a viable route to reduced building energy consumption. Reversible electrodeposition-based systems are advantageous due to the high optical contrast. However, they are often limited by high specular reflectance, insufficient modulation in the near-infrared (NIR) region, and a lack of continuously tunable intermediate states. Therefore, we introduced a redox-mediated strategy that leverages the synergistic interaction between Mn²⁺ and viologens to regulate the MnO₂ deposition kinetics. This cooperative interaction ensures precise optical tunability, enabling the stabilization of continuous intermediate states while simultaneously enhancing NIR modulation in the colored state. The device achieves an ultralow average visible transmittance of 0.1%, a solar modulation efficiency ΔT_sol of 63.3%, low reflectance (∼ 8%) and a coloration time of 10.5 s. This smart window significantly reduces energy demands for building thermal management, lowers carbon emissions, and provides a viable pathway toward energy-efficient green buildings.