CEMS graduate students win awards at Minnesota chapter AVS Symposium

Maya Ramamurthy, a 3rd year chemical engineering PhD candidate, and Bryan Cote, a 5th year chemical engineering PhD candidate, both advised by CEMS Associate Professor Vivian Ferry, won awards at the recent Minnesota chapter AVS Symposium. Both awards included cash certificates and free AVS memberships. Maya claimed the top prize of $750 for "Best Talk” and Bryan was runner-up, winning $500. The theme of the symposium was “Vacuum - the Enabling Science and Technology.”

Maya presented recent work in the Ferry Group on “Chiral Metamaterials for Directional and Polarization Control of Photoluminescence.” Metamaterials, periodic materials made of sub-wavelength particles, are an exciting class of artificial materials whose response to light depends on their geometry and local environment, not just on the properties of their constituent particles. Systems that couple together luminophores and chiral metamaterials can be designed to emit light with a certain polarization and direction, which is useful for a range of applications including sensors, 3D displays, security tagging, and photonic circuits. In this collaborative research, Maya and several other members of the Ferry Group investigated the effect of luminophore placement on the direction and polarization of light emitted from a metamaterial made of gold nanorods. It was revealed that strategic placement of luminophores in specific locations enabled greater degrees of direction and polarization control, compared to when the luminophores uniformly coat the surface of the gold nanorod array. 

Bryan offered a presentation on “Spectrally Selective Mirrors for Light Management in Bifacial Photovoltaics.” In contrast to monofacial photovoltaic modules that can only collect light from their front face, bifacial photovoltaics can convert light incident on both front and rear faces into electricity. In the field, bifacial photovoltaic modules routinely run 10s of degrees above ambient. A major, but often overlooked, source of heat generation within these modules is the parasitic absorption of sub-bandgap light. Light with energies less than 1.1 eV, which accounts for roughly 19% of the solar spectrum, does not have the energy necessary to get converted into electricity and thus only heats the photovoltaic modules. Bryan and his collaborators modelled the performance of a light management strategy consisting of spectrally selective mirrors to passively cool bifacial photovoltaic modules. The photonic mirrors were designed to increase the collection of above-bandgap useful light and simultaneously block sub-bandgap waste height light. Idealized spectrally selective mirrors were found to provide significant levels of module cooling and increases in energy generation. Additionally, realistic mirror designs were optimized that outperform traditional antireflection coatings in both energy generation and module cooling.

The mission of the Minnesota AVS chapter is technical education and outreach centering on the development and analysis of surfaces, thin films, and nanomaterials.