Nanomolded buried light-scattering (BLiS) back-reflectors using dielectric nanoparticles for light harvesting in thin-film silicon solar cells

The article presents a nanoparticle-based buried light-scattering (BLiS) back-reflector designrealized through a simplified nanofabrication technique for the purpose of light-management in solar cells. TheBLiS structure consists of a flat silver back-reflector with an overlying light-scattering bilayer which is made of aTiO2 dielectric nanoparticles layer with micron-sized inverted pyramidal cavities, buried under a flat-toppedsilicon nanoparticles layer. The optical properties of this BLiS back-reflector show high broadband and wideangular distribution of diffuse light-scattering. The efficient light-scattering by the buried inverted pyramidback-reflector is shown to effectively improve the short-circuit-current density and efficiency of the overlying n-ipamorphous silicon solar cells up to 14% and 17.5%, respectively, compared to the reference flat solar cells. Alayer of TiO2 nanoparticles with exposed inverted pyramid microstructures shows equivalent light scatteringbut poor fill factors in the solar cells, indicating that the overlying smooth growth interface in the BLiS backreflectorhelps to maintain a good fill factor. The study demonstrates the advantage of spatial separation of thelight-trapping and the semiconductor growth layers in the photovoltaic back-reflector without sacrificing theoptical benefit.