Plasmonic Screening Effect of Gold Nanoparticles Array on Light Absorption in Poly(3-hexyl)Thiophene Thin Film.

The localized surface plasmon (LSP) photophysical phenomenon occurring in metal nanostructures is often presented as a way to effectively couple light into sub-wavelength-scale photovoltaic devices, which would otherwise suffer from a weak light absorption. The simultaneous complementary effect of localized optical field depletion receives far less attention. We studied a system consisting of a planar gold nanoparticles array (AuNP) deposited at the surface of a semiconducting polymer thin film (P3HT). By comparing the UV-vis spectra of P3HT with and without the AuNP array, we have estimated that the AuNPs screen the optical absorption in the interfacial layer of about 3.8 nm effective thickness due the near-field depletion effect. It suggests that the AuNP array may be used to practically "hide" a thin semiconductor layer, e.g., in order to tune the perceived color of the photovoltaic cell embedded in architecture, or in wearable devices.