Dual‐Band Modulation of Emissivity and Solar Transmittance Through Chemical Composition‐Tuned Asymmetric Layer‐by‐Layer Assembly

ABSTRACT Buildings contribute approximately 40% of global energy consumption, with windows being among the least energy‐efficient and most complex components of building envelopes. Recent advancements in vanadium dioxide (VO 2 )‐based Fabry‐Pérot (F‐P) resonators, which integrate both solar modulation and radiative cooling (RC) regulation into a single, energy‐efficient window, present a significant opportunity for year‐round global energy conservation. However, the effectiveness of this innovation is often limited by inadequate modulation capabilities and low luminous transmittance ( T lum ) resulting from spatial disorder at the nanoscale. In this study, we introduce an unconventional asymmetric Layer‐by‐Layer (LbL) assembly technique that spatially leverages wavelength‐specific functional components to enhance spectral selectivity. This approach achieves a 52.1% improvement in T lum and an 8.6% increase in solar modulation (Δ T sol ) compared to current state‐of‐the‐art technologies, while maintaining a comparable mid‐infrared (MIR) emissivity modulation (Δ ε MIR ) of 0.4. These findings validate the efficacy of the LbL process in fabricating spectrally selective smart devices and underscore its significant potential beyond just energy‐efficient smart windows.