Ultrathin and broadband mid-infrared metasurface perfect absorbers for transparent radiative cooling

In this study, we propose a design of an ultrathin, visibly transparent, and broadband perfect metasurface absorber for transparent radiative cooling applications. The absorber includes a polymethyl methacrylate (PMMA) layer sandwiched by an indium tin oxide (ITO) bottom layer and an ITO cross-shaped top layer and achieves an excellent average absorption of over 97% in the mid-infrared (MIR) atmospheric window (8–13 µm) and an average transparency of over 81% in the visible. In addition, we develop a transparent radiative cooler by refining the back reflector structure of the designed absorber to increase the average near-infrared (NIR) reflectance to 77% while maintaining transparency in the visible range and high absorption in the MIR, and demonstrate that this modified design enables enhanced cooling performance. These results indicate that the proposed absorber and cooler provide promising solutions for passive thermal management in energy-efficient systems.