August 13, 2013
Hosted by: Center for Integrated Science and Engineering
Speaker: Prof. Barry P. Rand, (Assistant Professor, Dept. of Electrical Engineering, Princeton University)
Organic-based solar cells are beginning to emerge with the potential to compete with other low-cost thin film photovoltaic technologies, with efficiencies of 12% demonstrated in recent months. While recent enhancements can be attributed mostly to novel materials, parallel routes investigating new device architectures and photonic strategies are necessary for further improvements. Here, I will focus on our recent efforts to template and control film morphology and molecular orientation: working with films and bulk heterojunctions possessing nanocrystalline domains, to those with microcrystalline domains. Optical considerations are also crucial for thin film solar cells, in other words to eliminate parasitic absorption and to exploit optical interference and light trapping strategies such that absorption and photocurrent generation can be optimized. Here, I highlight two approaches for photonic light trapping. In one, we have explored the possibility to use multilayer oxide/metal/oxide (OMO) structures that are compatible with flexible substrates and able to replace costly and brittle indium tin oxide (ITO) transparent anodes. Simultaneously, they assume a photonic light trapping role, capable of producing devices on OMO anodes with performance equal to devices on ITO despite less far-field transmission. In another approach, we explore plasmonic strategies to enhance solar cell performance. By nanostructure the rear electrode, which acts as a back-reflector, we could realize scattering-based enhancement of an otherwise-optimized thin film cell.
Barry P. Rand earned a B.E. in electrical engineering from The Cooper Union in 2001. He then received M.A. and Ph.D. degrees in electrical engineering from Princeton University in 2003 and 2007, respectively. From 2007-2013, he has been a principal scientist at imec in Leuven, Belgium, working on the understanding, optimization, and manufacturability of thin-film solar cells. Since 2013, he has been an Assistant Professor in the Electrical Engineering Department and the Andlinger Center for Energy and the Environment at Princeton University. His research interests highlight the border between electrical engineering, materials science, chemistry, and applied physics, covering electronic and optoelectronic thin films devices composed of nanostructured media, and plasmonics. He has authored more than 50 refereed journal publications and has 10 issued U.S. patents.