A nondestructive optical method for determining the complex dielectric permittivity ε(ω) of silicon photovoltaic converters (PVC) surfaces modified with silver nanoparticles is developed and experimentally validated. The method is based on backscattered radiation analysis and enables reconstruction of both real and imaginary components without altering the structure of objects under study [Kuric 2022]. Modified PVCs demonstrate a 2–5-fold increase in backscattering intensity and a 9–30% increase in photovoltaic pow er is observed, attributed to localized surface plasmon resonance. Compared to conventional ellipsometric approaches, the proposed method provides a simpler and robust alternative for in-situ diagnostics of plasmonic coatings. The obtained results indicate that the imaginary part of the dielectric permittivity plays a crucial role in determining the efficiency of electromagnetic energy absorption. The experimentally observed increase in photovoltaic power correlates with both the enhancement of the local electromagnetic field and the rise in effective dissipative losses in the near-surface region. Despite the theoretically predicted high absorption of electromagnetic energy, the overall efficiency gain of photovoltaic cells remains limited due to the localized nature of localized surface plasmon resonance, as well as scattering effects and structural inhomogeneity in the nanoparticle distribution.
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