Upcycling polycrystalline silicon from waste solar cells for thermally conductive epoxy composites: Anisotropic crystallite growth and tailored microstructure via heat treatment

초록

Effective thermal management has become critical in the electronics industry due to rising power densities and heat generation in modern electronic systems. While polymer-based composites are widely used for electrical components and equipment, their low thermal conductivity (~0.2 W/m·K) limits applicability in high-performance systems. To address this, thermally conductive fillers such as hexagonal boron nitride (h-BN), aluminum nitride (AlN), and alumina (Al<inf>2</inf>O<inf>3</inf>) have been employed, though many involve complex, costly processes and offer limited environmental benefits. This study proposes a sustainable strategy using waste solar cells as thermally conductive fillers. Polycrystalline silicon (p‑silicon), known for its high thermal conductivity (70–100 W/m·K), was recovered from waste solar cells via metal leaching and reduced to the nanoscale by ball milling. Thermal treatment was applied after ball milling to promote anisotropic grain growth along specific crystallographic planes and facilitate tailored microstructure formation via interparticle diffusion and necking. Treated fillers were uniformly blended with epoxy resin and thermally cured. As a result, composites containing 40 vol% of thermally treated p‑silicon achieved thermal conductivity up to 3.411 W/m·K, surpassing that of epoxy systems filled with conventional ceramic fillers at similar loadings. This work advances thermal management and supports environmental sustainability through solar cell waste upcycling. © 2025 Elsevier B.V.

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