Molecular Approach to Photovoltaics
Speaker: Cherie Kagan, University of Pennsylvania
Date & Time: October 20, 2009 - 12:10pm
Location: CCR 201
Molecular and nanoscale electronic materials are being aggressively pursued for a wide range of applications - - from, for example, low-cost, large-area, flexible macroelectronics and optoelectronics to post-CMOS alternatives for high performance nanoelectronics, chemical and biological sensors, and thermoelectrics. In this talk, I will describe the electronic, optical, and chemical properties of solution-processable organic thin films and nanocrystal and nanowire assemblies that make them exciting materials for low-cost, flexible electronics and organic-inorganic hybrid photovoltaics (PVs). I will give examples in which molecular engineering at device interfaces can be used to tailor charge injection and transport in these materials and their devices. In organic transistors, energetic barriers at the metal electrode-molecule interface gives rise to undesirably high contact resistances. We have shown that self-assembly of molecules at the metal-molecule interface dramatically reduces the barrier to charge injection and allows the fabrication, with polymer gate dielectrics, of ambipolar devices and complementary circuits, such as high gain inverters. In chemically synthesized PbSe nanowires, as synthesized nanowires assembled in the channels of transistors show hole conductivity. Exposure to molecular charge-transfer dopants are used to change the carrier type, transforming p-type into n-type transistors. We use synthetic methods to tailor the chemical and physical properties of both organic and nanostructured materials to provide building blocks with attributes engineered for the low-cost fabrication of hybrid PVs.
Cherie Kagan earned both a B.S.E. in Materials Science and Engineering and a B.A. in Mathematics from the University of Pennsylvania in 1991. In 1996, she received her Ph.D. in Electronic Materials from MIT. Her thesis work focused on the self-assembly of close packed solids of semiconductor nanocrystals and the unique electronic and optical properties that arise in nanocrystal assemblies. In 1996, Cherie went to Bell Laboratories as a PostDoctoral Fellow. In 1998 she joined IBM's T.J. Watson Research Center where she most recently managed the "Molecular Assemblies and Devices Group." In January, 2007 Cherie joined the faculty of the University of Pennsylvania's Departments of Electrical and Systems Engineering and Materials Science and Engineering as an associate professor. In addition she assumed the position as the Director of the University's Nanofabrication facility. In 2009, Cherie was named the co-director of Pennergy: Penn's Center for Energy Innovation as well as the University of Pennsylvania's Director of the Energy Commercialization Initiative, a multi-institutional partnership funded by the Commonwealth of Pennsylvania to accelerate commercialization of clean, alternative energy technologies. Cherie's research is focused on studying the chemical and physical properties of molecular and nanostructured assemblies and thin films and their integration in electronic and optoelectronic devices impacting low-cost and flexible macro- and nano-electronics and nano-photonics, solar photovoltaics, and chemical and biological sensors.
Cherie was selected by the American Chemical Society in 2002 as one of the top 12 Women at the Forefront of Chemistry for her work on designing novel molecular materials and devices, featured by the American Physical Society in Physics in Your Future, and in 2000 chosen by the MIT Technology Review TR10. In 2005, she received IBM's Outstanding Technical Achievement award and in April, 2009 gave Stanford University's Distinguished Women in Science Colloquium. She is on the editorial boards of American Chemical Society's journals "Nano Letters" and and "Applied Materials and Interfaces," on the editorial board on "NanoToday," serves on the Materials Research Society's Board of Directors.
Host: Lisa Klein