Experimental investigation of high-performance Ag@SiO2 core-shell nanofluid for spectral beam splitting in photovoltaic/thermal systems

The performance of photovoltaic/thermal systems is often limited by the inefficient utilization of near-infrared photons and the poor spectral compatibility between optical filters and solar cells. Although Ag@SiO2 core-shell nanoparticles below 50 nm show great potential as spectral beam splitting filters, experimental studies on their filtering performance and the systematic optimization of spectral splitting photovoltaic/thermal systems remain scarce. To address this gap, we develop high-performance optical filters. Ag@SiO2 nanoparticles with an average Ag core size of 25 nm and SiO2 shell thickness of 10 nm were synthesized via an improved reduction method. These nanofluids exhibited a blue-shifted localized surface plasmon resonance, increasing transmittance by up to 8.61% for Si cells and 6.37% for GaAs cells. In photovoltaic/thermal testing, electrical efficiencies reached 11.19% (Si) and 16.59% (GaAs), with a thermal efficiency of 68.90%, while the system merit function outperformed that of existing nanofluids. The filters also demonstrated excellent colloidal stability under long-term storage, light irradiation, and thermal cycling. Orthogonal experiments identified the mass flow rate as the most influential performance parameter. This study provides the first experimental insight into sub-50 nm Ag@SiO2 optical filters, and establishes a systematic optimization framework for efficient spectral splitting photovoltaic/thermal systems.