Our research program studies the interaction between light and nanostructured materials, focusing on the emergent optical, electrical, and chemical properties of nanoscale materials. We are especially interested in studying plasmonic materials, colloidal semiconductor nanoparticles, and optical metamaterials. We design nanostructures using a combination of experimental and theoretical techniques, synthesize our structures using both bottom-up and top-down methods, characterize the material properties, and ultimately integrate our designs into functional devices and systems. A few highlights of recent research are discussed below.
Luminescent Solar Concentrators
Luminescent solar concentrators (LSCs) are specialized optical waveguides that harvest direct and diffuse sunlight, and convert it into a spectrally narrow and focused light source for enhanced solar energy conversion. The LSC consists of a luminescent material embedded in a polymer waveguide. Incident sunlight is absorbed by the luminescent material and emitted at a longer wavelength, and the emitted photons are concentrated onto a solar cell mounted on the edge of the LSC.
Research in our group focuses on LSCs incorporating nanocrystal luminophores, and on integrating spectrally-selective mirrors that improve light guiding to the solar cell and decrease escape cone losses. We have recently studied the design of spectrally-selective mirrors for the top face of the concentrator, showing that the balance between transmission of high energy light and trapping of luminescent light varies as the quantum yield and concentration of the luminophore vary, as well as the size of the concentrator. We have also studied the use of metamaterial mirrors to guide light toward the edge of the concentrator.
Photovoltaic Module Thermal Management
Reducing the operating temperature of silicon photovoltaic modules increases both the module energy yield and lifetime. Our research focuses on designing, characterizing, and fabricating nanophotonic structures which reduce module temperature by reducing parasitic absorption of sub-bandgap photons in the module. We consider designs with reflection, transmission, or scattering properties which are controlled over the wavelength range of the solar spectrum. Furthermore, we focus on achieving significant temperature reduction via inexpensive processing techniques to decrease levelized cost of the electricity.
Semiconductor nanocrystals, or quantum dots (QDs), have gained much attention over the past twenty years due to their unique photophysical properties, including emission and absorption wavelength tunability, high color purity, and solution processing ease. Chiral QDs have recently emerged as an important subclass of these materials, in which the nanoparticle becomes non-superimposable with its mirror image through the introduction of chiral organic molecules to its surface. Chiral QDs are predicted to play a central role in many diverse applications, including biological sensors, spin-polarized devices, and document security and anti-counterfeiting technologies. Research in our group has recently studied chiral CdSe bound by chiral carboxylic acid ligands. Small structural changes to the chiral carboxylic acid ligands were shown to have dramatic effects on the chiroptical properties of the resulting chiral CdSe QDs, resulting in high dissymmetry factors.