Encapsulated High‐Salt but Corrosion‐Resistant Hygroscopic Medium for Long‐Term Passive Solar Cell Cooling

Abstract Cooling the solar panel with hygroscopic materials offers a potential solution to mitigate its thermal damage and photovoltaic efficiency reduction. However, the practical application of this approach is significantly hindered by the limited water storage capacity and the back electrode corrosion. In this study, it is demonstrated that encapsulating LiCl‐loaded carbon felt in a superhydrophobic polytetrafluoroethylene membrane effectively preserves its high absorptivity while preventing the conventional corrosion issue. This approach ensures sustainable and long‐term passive cooling of solar cells. The high‐salt but corrosion‐resistant (HSCR) material has extremely high water adsorption and storage capacities, which is characterized by the ability to absorb more than 5 times its weight of water within 8 h of incubation at 25 °C and 90% relative humidity (RH). Under 1 sun illumination, incorporating HSCR reduces the solar panel temperature by 17.8 °C while increasing the photovoltaic efficiency by 10.7%. More importantly, the salts encapsulated within the membrane remain leak‐proof and the cooling performance can be effectively regenerated after multiple cycles. This work provides a promising solution for sustainable and passive solar panel cooling.