Constructing functionalized eco-friendly boron nitride and diatomaceous earth based phase change composite backsheets for thermal management and fire safety of solar modules†

As a clean energy source, photovoltaic (PV) technology has gained widespread global adoption. However, temperature fluctuations and flammability significantly impact PV system efficiency and lifespan, necessitating effective temperature management and flame retardancy. In this study, we introduced an innovative environmentally friendly backsheet for solar modules, combining radiative cooling with phase change materials (PCMs) to achieve superior thermal regulation and fire resistance. Functionalized boron nitride nanosheets (BNNs) were prepared via ionic liquid-assisted ball milling. The biomass-derived diatomaceous earth (DE) and BNNs were then bonded with polyvinyl alcohol (PVA) and freeze-dried to fabricate aerogels. The final DE/BNN phase change materials (PCMs) obtained from vacuum impregnation with methyl stearate (MS) exhibited high thermal conductivity (0.778–1.311 W m⁻¹ K⁻¹), high latent heat (92.7–126.1 J g⁻¹), and flame-retardant properties (total heat and smoke release were reduced by 32.6% and 60.0%). When applied as a backsheet to single-crystal silicon (sc-Si) solar cells, the DE/15BNN PCM significantly reduced the operating temperature by 6.7 °C and enhanced the power conversion efficiency (PCE) by 9.3%. Benefiting from the inherent properties of the matrix and the effective restriction of electron movement by BNNs, the DE/BNN PCM achieved high insulation properties (22.22 kV mm⁻¹), meeting the standards for commercial backsheets. Additionally, the DE/BNN PCM demonstrated excellent UV resistance, maintaining its performance even after prolonged UV exposure. This work introduces an innovative and sustainable approach to improving the efficiency, fire safety, and longevity of solar modules by integrating dual cooling mechanisms, providing a promising solution for solar energy systems.