Seminar 3/14/2012 - Bernard Kippelen, Georgia Institute of Technology: Advances in Printed Organic Electronics Through Interface Modification
Abstract: Printed organic electronics, a technology based on organic semiconductors that can be processed into thin films using conventional printing and coating techniques, has been the subject of active research and development over the past decades. A range of solid-state devices, including organic light-emitting diodes (OLEDs), field-effect transistors, photodiodes, and solar cells have been demonstrated with this new class of materials. Due to their ability to be processed at low temperature, over large areas, at low cost, organic semiconductors have experienced an accelerated development in recent years and have the potential to spawn a new generation of products with thin and flexible form factors. However, despite a steady progress in performance, many challenges and concerns about stability and cost remain before this emerging technology can unleash its full potential.
In this talk, we will focus on the role of interfaces in organic solid state-devices. First, we will discuss the limitations of organic solar cells and why the commonly used device architectures present major challenges. In particular, we will show that the widely used indium-tin oxide (ITO) electrodes exhibit variations in the work function that impact device stability. Strategies to control and stabilize the value of the work function will be presented. Another hurdle is in the limited choice of low work function metals and their high chemical reactivity when exposed to ambient conditions. Metals such as Ca are widely used in record-high efficiency organic solar cells but require hermetic packaging. A new method to produce air-stable low work function electrodes as a substitute for Ca will be presented. This method is based on surface modification by water-soluble polymers that physisorb to the surface of various conductors and lead to large surface dipoles that shift the vacuum level (> 1 eV) reducing the injection or collection barrier for electrons. Finally, we will show that these advances in interface modification can be used to design organic solar cells with novel architectures that can overcome some of the economic hurdles of current approaches and accelerate the deployment of these technologies.
Bio: Bernard Kippelen is currently a Professor at the School of Electrical and Computer Engineering at the Georgia Institute of Technology, located in Atlanta, Georgia, USA. His research interests range from the investigation of fundamental physical processes (nonlinear optical activity, charge transport, light harvesting and emission) in organic-based nanostructured thin films, to the design, fabrication and testing of light-weight flexible optoelectronic devices based on hybrid printable materials. He serves as Director of the Center for Organic Photonics and Electronics and as Associate Director of CIS:SEM an Energy Frontier Research Center funded by the Department of Energy (DOE).
Bernard Kippelen was born and raised in Alsace, France, and is a US citizen. He studied at the University Louis Pasteur in Strasbourg where he received a Maitrise in Solid-State Physics in 1985, and a Ph.D. in Nonlinear Optics in 1990. From 1990 to 1997 he was Chargé de Recherches at the French CNRS. In 1994, he joined the Optical Sciences Center at the University of Arizona, where he was promoted Assistant Professor in 1998 and Associate Professor with Tenure in 2001. He joined Georgia Tech in 2003 with the rank of Professor.
He holds 15 patents and has co-authored over 600 scientific communications, including 200 peer-reviewed journal publications and eleven book chapters. His work has received over 7,000 citations and his H-index is 42. He served as chair and co-chair of numerous international conferences on organic optoelectronic materials and devices. He is the co-founder of several spin-off companies and the recipient of an NSF-Career Award (2000), a 3M Corporation Young Faculty Award (2000), and is a Senior Member of IEEE (2005). He was elected a Fellow of the Optical Society of America (2006), and a Fellow of SPIE (2007). He serves as a Deputy Editor for Optics Express (2009) and as the founding Editor of Energy Express (2010).
All seminars are held on Wednesdays from 12:00 noon-1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.
Location: Bowen Hall Auditorium
Date/Time: 03/14/12 at 12:00 pm - 03/14/12 at 1:00 pm
Category: PRISM/PCCM Seminar Series