Molecular Valve Engineering Enables Uniform and Low‐Emission Electrochromic Smart Windows

ABSTRACT

Electrochromic smart windows hold great promise for energy‐efficient buildings, yet they often suffer from non‐uniform electrochemical doping and undesirable light emission under strong illumination. Here, we report a molecular valve engineering strategy by incorporating photoresponsive side chains into conjugated polymers to regulate both ion transport and excited‐state energy dissipation. Upon activation, the polymer undergoes a structural transformation that modifies the local polarity and ion‐associated microenvironment, while promoting nonradiative decay pathways. As a result, the electrochromic devices exhibit highly uniform coloration behavior and suppressed emission intensity compared to control systems. The optimized devices further demonstrate multicolor modulation and dual‐band optical regulation in the visible and near‐infrared regions. When applied in building simulations, the smart windows enable a temperature reduction of 5.05°C and an energy saving of 15.3 kWh m ⁻² . This work provides a molecular design strategy for achieving uniform and low‐emission electrochromic systems for smart window applications.