Selective Scatterers Improve Efficiency and Color Neutrality of Semitransparent Photovoltaics

We demonstrate that dielectric Mie scatterers, in the form of silicon nanoparticles (SiNPs), can enhance both the performance and esthetics of semitransparent photovoltaic devices. Unlike plasmonic metal counterparts, dielectric SiNPs exhibit lossless, narrow-band, spectral, and spatially tunable scattering in the visible spectral range. Their effect on a luminescent solar concentrator (LSC) with high visible light transparency is analyzed both theoretically and experimentally as a model system. By selectively reflecting a specific spectral band, SiNPs increase the optical path length of solar photons within the active layer, leading to improved absorption and hence device efficiency. Simultaneously, this light management strategy ensures transmitted color neutrality, an important requirement for wider acceptance of semitransparent photovoltaics. Numerical simulations show that in the regime of individual SiNPs with diameters around 160 nm, a submonolayer surface coverage of ∼10% is sufficient to achieve color neutrality, at the same time enhancing photocurrent by 10-15% for an LSC device. Experimentally, such a dispersed SiNP layer on an LSC substrate is realized by depositing NPs with the surface capped by a sacrificial polymer shell. Subsequent etching of the shell by oxygen plasma leads to an LSC device with a functional selective scattering layer in line with theoretical predictions.