Peter F. Green
Afternoon Keynote Lecture
12:45 – 1:40 p.m.
Design, Transport Processes and Device Performance of Organic Solar Cells"
The design and synthesis of novel conjugated polymers for organic photovoltaic (OPV) applications continue to attract significant attention due to a real promise for efficient light-to-electricity conversion at low cost, compared to inorganic materials, for some applications. Other characteristics of polymeric materials – lightweight, flexible, semitransparent, solution-processible – confer additional advantages to OPVs with regard to ease of fabrication and diverse applicability. The enhancements of power conversion efficiencies (PCEs) of these devices have largely been due to the introduction of new conjugated polymers. The active material in one of the most commonly investigated OPVs, the bulk-heterojunction (BHJ) solar cell, is composed of a blend of a donor polymeric material and an acceptor, usually a fullerene. In recent years the role of the morphological structure (phase size and purity, interfacial structure) of the active material on device performance has began to receive significant attention, experimentally and theoretically. Consequently our understanding of the role of the morphology on the PCEs continues to evolve, particularly as new experimental tools and processing strategies are exploited. A combination of new materials and morphologies, optimized for the particular active components, will enable the development of future high efficiency OPVs. This presentation will be devoted to a discussion of research on carrier transport processes (carrier mobilities recombination, charge generation) in specific morphologies for the poly(3-hexylthiophene):phenyl-C61 butyric acid methyl ester (P3HT:PCBM) system, engineered to possess different morphologies, and the effect on device performance parameters. Specifically, we will provide insight into interrelations between aspects of the active material morphological characteristics (i.e. domain size, phase purity, conjugation length), the transport properties, and the device efficiencies. In a separate study we investigated the role of an additive, a copolymer, on the morphology of P3HT:indene-C60 bisadduct (ICBA) active layers and hence the device performance. It will be shown how changes to the morphology of the active layer, due to the presence of the copolymer, influence specific transport process (carrier mobilities and charge generation/recombination) leading to enhancements in the device PCEs.
Peter F. Green is the Vincent T. and Gloria M. Gorguze Professor of Engineering and Chair of the Materials Science and Engineering Department at the University of Michigan, Ann Arbor. He's also the Director of the Center for Solar and Thermal Energy Conversion (CSTEC), an DOE sponsored Energy Frontier Research Center (EFRC).He is Editor-in-Chief of MRS Communications (MRS/Cambridge University Press) and he was the 2006 President of the Materials Research Society (MRS). He is a Fellow of the Royal Society of Chemistry (UK), Fellow of the American Physical Society and a Fellow of the American Ceramics Society. Green's research group is interested in developing and understanding the properties of organic materials and organic/inorganic hybrid materials for functional coatings, sensors and energy conversion applications. His specific interests include: transport processes, optical properties, interfacial phenomena, phase transitions, self-assembly and pattern formation. He earned his doctorate in Materials Science and Engineering from Cornell University on 1985, hi MS from Cornell in the same field and his MA and BA (Honors) degrees in Physics from Hunter College, N.Y.