This is a past event.

Rene Lopez from the University of North Carolina at Chapel Hill will be presenting at this week's Physics Colloquium. The seminar will be presented in person at 4 PM, Thursday, October 26 in Fisher 139.

ABSTRACT:

Efficient absorption of photons and effective charge carrier extraction are the key properties that enable good performance in a photovoltaic cell. These two functions depend primarily on material-intensive properties such as optical constants, band alignments, defects, and charge mobilities and lifetimes. Morphology and geometrical factors at a large range of length scales are nevertheless decisive, as light absorption and carrier extraction are frequently found to present their best performances at opposite ends of geometrical variables.

Pulsed laser deposition (PLD) is a physical thin film growing technique that enables the variation of morphology, from compact layers to nanoparticle aggregates, with the continuous degree of structural connectedness and tunability of the electrical charge transport quality. Combined with controlled seeding/patterning of the substrate, geometrical control can be tailored at a larger scale to affect optical absorption and potentially their mechanical properties.

In particular, we have developed a high surface area oxide fabrication that offers a tree-like hierarchical arrangement of nanoparticles that preserves a high surface area while building direct highways to transport the charges toward the bottom contacts for sensitized solar cell configurations. Simple patterning allows for enhancements in their photon-to-electron conversion efficiency.

We will also describe potential and in-progress electro-photonic enhancements utilizing these structural modification approaches to quantum dot photovoltaic systems and also the flexibility of the supporting transparent conductive substrates when designed under this geometrical strategy.

BIO:

Prof. Rene Lopez obtained his Bachelor's degree from the Monterrey Institute of Technology (Mexico) and his Master's and Doctoral degrees from Vanderbilt University (USA). He worked at the Oak Ridge National Laboratory and Vanderbilt University before joining the University of North Carolina Faculty at Chapel Hill (UNC) in 2006. He currently heads a group at UNC that performs research in optical materials and microstructures for photovoltaics, artificial photosynthesis, and 3D printing technologies.