Visible-to-Infrared Invisibility: Degenerately Doped Semiconductor Nanostructures for Flexible, Large-Area...

Multispectral camouflage combining visible (VIS) transparency with controlled optical responses across the short-wave, mid-wave, and long-wave infrared (SWIR-MWIR-LWIR) remains challenging due to intrinsically contradictory spectral requirements. Here, we present an optically transparent low-IR-signature (OTLIS) modular platform based on degenerately doped indium tin oxide (ITO) nanostructures that enables simultaneous VIS transparency, broadband SWIR absorption, and suppressed MWIR-LWIR thermal emission. Strong, angle-insensitive absorption that attenuates solar irradiation and offers a wide-angle countermeasure against active laser-guided tracking systems is enabled by shifting the epsilon-near-zero (ENZ) point into the SWIR range by adjusting the free-carrier concentration through forming-gas annealing (FGA) activation. This degenerate doping increases the plasma frequency, placing the MWIR-LWIR band in the metallic-reflection regime with low thermal emissivities. A trapping nanoscaffold is further developed using oblique angle deposition (OAD) to enhance SWIR light-matter interaction while sustaining reflective metallic behavior in MWIR-LWIR ranges. Extension to flexible platforms using nanoparticle-embedded PDMS enables conformal, mechanically robust implementations while preserving optical functionality. Infrared imaging of coated aerial and wearable systems confirms apparent-temperature reduction under realistic conditions. These results establish a scalable route toward transparent multispectral camouflage and degenerately doped semiconductor nanostructures for adaptive thermophotonic and stealth applications.