Solar energy research in Ramki Kalyanaraman's group

If the virtually inexhaustable energy provided by the sun can be harvested, stored, and utilized, it could help move our society towards a more harmonious existence with our surroundings. However, important breakthroughs are needed, such as more efficient and cheaper solar cells.

CHALLENGES: While Si solar cell technology has been around for more then 30 years, the cost per watt of energy solar energy production continues to prohibit its widespread use. Many factors contribute to this, including cost of materials, complexity of fabrication, poor light absorption, poor efficiency at converting photons into energy, etc. Our research on solar energy is primarily focussed on harnessing the energy through innovations in Si ultrathin solar cells (schematized in the adjacent figure), inventing new and better solar cells such as hollow fiber based solar fabric, and improved light trapping coatings.

Si Nanocomposite Solar Hollow Fiber Solar Cells Plasmonic solar coating design

Si Nanocomposite Solar

In this research we are working to realize ultrathin Si solar cells of high efficiency. While thin film multicrystalline Si is an important photovoltaic material, its future use in large-area sustainable energy applications, such as in solar panels, that require low cost and high efficiency is questionable. On the other hand, ultrathin film technology has an inherent disadvantage compared to bulk Si solar cell technology primarily because of the poor absorption of Si at wavelengths larger then 600 nm (Fig. 1). Traditional methods that are used to increase the light trapping efficiency of thick solar cells, such as surface texturing, cannot be used for thin films because surface texturing amplitudes are of the order of few microns. Our approach is to discover nanoparticles to incorporate into ultrathin Si films (~0.1 micron) such that optical trapping is significantly enhanced without degradation to electrical behaviors. We have recently made progress in this area by showing that Ni-Silicides dramatically enhance absorption in Si.

R. Sachan et al NME 2013 or obtain pdf here

Hollow Fiber Solar Cells

Plasmonic Solar Coating Design

In this research we use a computer to design and discover new materials for solar, plasmonic, and other optical applications.The strong optical interaction seen when nanoscale metal-dielectric structures interact with light promise several applications, including optical manipulation well below the diffraction limit, high-speed information processing and integration of Si electronics with optics. The strong interaction is a result of the resonant absorption of electromagnetic radiation by plasmons, which are collective oscillations of large concentrations of nearly free electrons. For nanoscale metallic structures, surface plasmons are primarily responsible for this interaction. Nanocomposites made from metal nanostructures embedded in or placed on dielectrics offer significant potential as materials showing enhanced or tunable light harnessing. For instance, Schaadt and co-workers [SchaadtAPL05] have shown that incorporation of Au nanoparticles on the surface of a Si photodiode results in enhanced photocurrent at specific wavelengths that were correlated to the surface plasmon resonance. However, the fabrication of practically useful devices that utilize plasmonics to achieve a desired optical and/or electronic response requires the careful design and fabrication of nanomaterials with well defined shape, size and metal-dielectric composition. In this research we focussed on a theory-driven design and optimization of metal-dielectric nanocomposites that can show broadband optical absorption via plasmonic effects. (J. Trice et al Proc. SPIE v6648, pp 66480L, 2008)

(Send us an email if you are interested in knowing more about this technology)

Contact us for more information via the email link below!

Back to top