Photonic control of thermal radiation for protective windows

Thermal protection and comfort are essential for instruments and humans, especially in high-temperature scenarios such as fires and steelworks.Existing thermal protective windows absorb external radiation and heat when exposed to thermal sources, thereby failing to provide thermal comfort to users.Herein, we present a nanophotonic-engineered thermal protective window (NETPW) strategy that incorporates a visible-light transparent broadband directional thermal emitter and a low-emissivity coating into commercial polycarbonate (PC) windows.In comparison to a PC window exposed to a 700 K thermal source at a half-view angle of 50, the proposed NETPW exhibits remarkable temperature reduction (~77.7 ) by reflecting external radiation and enhancing directional radiative cooling.Simultaneously, the NETPW effectively inhibits heat emissions toward users, resulting in a significant improvement in thermal comfort, with a user's sensible temperature reduction of 57 .Moreover, the NETPW exhibits high visible transparency, high-temperature resistance, scratch resistance, and impact resistance.The seamless integration with existing windows provides a novel approach for controlling thermal emission and optimizing energy exchange.