Evaluation of photovoltaic energy availability under extreme atmospheric attenuation through nanofluid spectral modulation pathways

Under aerosol-dominated extreme attenuation, solar irradiance is constrained in both magnitude and spectral distribution, raising questions about the availability of spectral energy for photovoltaic (PV) systems. In this study, nanofluid-based optical media are used as a spectral modulation platform to evaluate photovoltaic energy availability under extreme atmospheric attenuation. Based on measured transmittance spectra, a four-parameter (band-wise) modulation fingerprint is constructed to characterize modulation directionality, strength, and spectral non-uniformity. Using a direction-independent spectral redistribution intensity (SRI), the competition between broadband extinction and inter-band energy redistribution is quantified, showing that increased modulation strength does not necessarily lead to effective spectral restructuring. Representative behaviors include nearly uniform spectral attenuation in ZnO at dilute concentrations and broadband extinction-dominated suppression in TiO₂. By incorporating microphysically defined aerosol perturbations, an environmental tunability function is introduced to identify wavelength-dependent adjustability windows, indicating that stable tunability is primarily confined to wavelengths beyond ∼800 nm (near-infrared). Coupling the modulated spectra with EQE responses of representative silicon PV architectures shows that, under extreme attenuation, spectral modulation induces only limited and gradual changes in photovoltaic response. Its role lies in feasibility screening and spectral–device consistency evaluation rather than performance enhancement. The proposed framework provides a transferable approach for assessing spectral modulation strategies in environmentally constrained PV systems.