Dual-anchored interfacial and sheet-sphere hybrid network engineering for thermally conductive, mechanically robust EVA/BN photovoltaic encapsulants

Encapsulation films combining high thermal conductivity, stable electrical insulation, and excellent mechanical properties are urgently needed for photovoltaic modules. However, achieving all these properties simultaneously in conventional ethylene–vinyl acetate copolymer (EVA) encapsulants remains a significant challenge. Herein, a synergistic three-tier strategy integrating EVA matrix crosslinking, a sheet-sphere hybrid filler network, and dual-anchored interfacial engineering is proposed to resolve this conflict. Specifically, 3-aminopropyltriethoxysilane (KH550) is grafted onto both the EVA matrix and the boron nitride (BN) filler surfaces via radical coupling and hydroxylation, respectively, establishing a dual-anchored interface of covalent bonds and hydrogen bonds. Combined with a sheet-sphere hybrid BN architecture (f-BN) constructed from hexagonal boron nitride microplatelets and spherical boron nitride microspheres, and a crosslinked EVA matrix (cEVA), this design enables the as-prepared cEVA/f-BN composite encapsulation film to achieve a high through-plane thermal conductivity‌ of 2.96 W·m⁻ 1 ·K⁻ 1 , representing a 1245% enhancement compared to the pure EVA film. Remarkably, the composite maintains a tensile strength of 8.99 MPa, an elongation of 89.75% at a filler loading of 110 phr, and a volume resistivity exceeding 10 14 Ω·cm. The composite film also exhibits high solar reflectance (91.09%) and infrared emissivity (96.17%), which in synergy with its enhanced thermal conductivity, reduce the photovoltaic module temperature by 5.34 ℃.This study not only demonstrates a good combination of thermal and mechanical properties in EVA encapsulants but also provides a broadly applicable interfacial design reference for the development of polymer composite materials that require both heat dissipation, mechanical strength, and electrical insulation.