In collaboration with researchers from UNC-CH Physics and Astronomy Department, investigators in the Samulski Group, and the DeSimone Group report organic solar cells with a photonic crystal nanostructure embossed in the photoactive bulk heterojunction layer, a topography that exhibits a 3-fold enhancement of the absorption in specific regions of the solar spectrum in part through multiple excitation resonances. The photonic crystal geometry is fabricated using a materials-agnostic process called PRINT wherein highly ordered arrays of nanoscale features are readily made in a single processing step over wide areas (4 cm2) that is scalable.
The research show efficiency improvements of 70% that result not only from greater absorption, but also from electrical enhancements. The methodology is generally applicable to organic solar cells and the experimental findings reported in the manuscript corroborate theoretical expectations.
Aggregation of isolated graphene sheets during drying graphene dispersions leads to a loss of its ultrahigh surface area advantage as a two-dimensional nanomaterial. The Samulski Group reports a metal nanoparticle-graphene composite with a partially exfoliated graphene morphology derived from drying aqueous dispersions of platinum nanoparticles adhered to graphene.
Platinum nanoparticles with diameters spanning several nanometers are adhered to graphene by a chemical route involving the reduction of metal precursors in a graphene dispersion. Face-to-face aggregation of graphene sheets is arrested by 3−4 nm fcc Pt crystallites on the graphene surfaces, and in the resulting jammed Pt−graphene composite, the Pt acts as spacers resulting in mechanically exfoliated, high-surface-area material of potential interest for supercapacitors and fuel cells.