Adaptive and Multicolored Electrochromic Smart Window with Transparent–Opaque Switchable Radiative Cooling

Abstract Transparent radiative-cooling windows can reduce cooling demand while preserving daylighting, yet high solar transmission becomes undesirable under strong solar irradiation. Although existing electrochromic windows can regulate solar transmittance, simultaneously achieving strong solar rejection, radiative heat dissipation, and wide-gamut coloration remains challenging. Here, we develop dynamic colorful radiative cooling windows by integrating planar coupled nanocavities with reversible silver electrodeposition. Electrochemically controlled Ag deposition/stripping reconfigures Fabry–Pérot resonances, enabling reversible switching between colored transparent and highly reflective colored opaque states while retaining high mid-infrared emissivity. The devices can achieve >40% modulation in average visible transmittance and cover 99.5% of the sRGB color gamut. Under outdoor conditions, they exhibit temperature drops of ∼7.0 °C compared to conventional glass and ∼8.7 °C relative to commercial electrochromic glass. This work provides a versatile platform for dynamic optical regulation with diverse requirements, paving the way for next-generation multifunctional smart windows, building envelopes, and smart photonic devices.