A High-Thermal-Conductivity Composite Film for Encapsulation and Passive Cooling of Solar Modules

Abstract

Encapsulants ensure mechanical integrity and operational stability of photovoltaic (PV) modules, yet conventional polymeric encapsulants exhibit intrinsically low thermal conductivity. Therefore, heat dissipation is severely impeded by the encapsulant and causes heat accumulation within the PV modules, leading to degradation of power conversion efficiency and acceleration of material aging. Herein, we engineer a novel high-performance composite encapsulant for rear-side replacement, enabling efficient multi-mode passive cooling through enhanced thermal conduction, infrared radiation, and light reflection. In this composite, strategically integrated binary networks of hexagonal boron nitride and aluminum oxide fillers are meticulously tailored to establish continuous thermal pathways while simultaneously boosting infrared emissivity to 85.38% and reflectivity to 85.48%. This innovative architectural design achieves exceptional thermal conductivities of 2.71 W/m·K in-plane and 1.01 W/m·K out-of-plane, representing significant enhancement. Under 1 sun illumination, PV modules employing this film as rear encapsulant exhibit a remarkable 2.2°C operational temperature reduction, directly results in an average operating voltage output of 7 mV. Crucially, the composite simultaneously maintains outstanding electrical insulation and robust encapsulation capability, ensuring operational safety and long-term reliability. This work provides a readily integrable material solution that significantly boosts PV efficiency and durability via synergistic conduction, radiation, and reflection.