A Multilayer Film Based Selective Thermal Emitter for Infrared Stealth Technology

Engineering the radiation characteristics for the design of selective thermal emitters has been a hot topic for decades and is of great value in the fields of thermophotovoltaic systems, radiative cooling, and infrared stealth. In this paper, a Ag/Ge multilayer film based selective emitter for infrared stealth is demonstrated using an ultrathin metal film and impedance matching to tune the radiation characteristics. Herein, a novel approach for infrared stealth that relies on the combination of emissivity (epsilon) reduction in the atmospheric windows (3-5 and 8-14 mu m) and radiative cooling in a nonatmospheric window (5-8 mu m) is proposed. The fabricated selective emitter has low emissivity (epsilon(3-5) (mu m) = 0.18; epsilon(8-14) mu m = 0.31) in the atmospheric windows for infrared "invisibility" and high emissivity (epsilon(5-8 mu m) = 0.82) outside the atmospheric window for radiative cooling and functions from ambient temperature to 200 degrees C. Compared with low- emissivity materials, the selective emitter exhibits higher radiative cooling efficiency in vacuum and practical environments and presents lower apparent temperatures on infrared cameras. Moreover, the proposed selective emitter, with a planar and simple structure, is scalable, allowing flexible large- area fabrication. The work demonstrates that selective emissive materials have promising applications in infrared stealth technology.