Multi-objective inverse design of transparent phase-change photonic windows for solar heat rejection and switchable mid-infrared emission

Adaptive thermal-management windows require coupled spectral control beyond emissivity switching, combining daylight transmission, near-infrared solar rejection, low solar absorption, and temperature-dependent long-wave emission. However, the conventional forward design strategy suffers from low efficiency when realizing multispectral co-optimization across the visible, near-infrared, and mid-infrared wavebands. Here, we develop a multi-objective particle swarm optimization (MOPSO)-based inverse-design workflow to optimize a transparent phase-change photonic window composed of a patterned W-doped VO 2 resonator, a BaF 2 spacer, and a ZnS/Ag/ZnS/Ag/ZnS reflector on glass. The ZnS/Ag multilayer provides admittance-matched visible transmission and admittance-mismatched near-infrared reflection, while also acting as the reflective boundary of the mid-infrared resonator. In the metallic phase, localized resonant loss in patterned VO 2 spectrally overlaps with a Fabry-Pérot-like BaF 2 /reflector response, producing broadband high emissivity; in the insulating phase, reduced VO 2 loss weakens this pathway and restores a reflection-dominated state. The optimized device achieves a spectrally weighted visible transmittance of 47.80%, near-infrared reflectance of 72.99%, solar absorptance of 23.24%, and an 8–13 μm emissivity switch from 0.0067 to 0.9956. Heat-balance calculations using the directly simulated 3–25 μm spectra indicate distinct heat-dissipating and heat-retaining responses for the metallic and insulating states, respectively.