November 22, Alejandro Briseno, University of Massachusetts, Amherst
Refreshments served at 2:45 PM
Crystal Chemistry, Molecular Order and Charge Transport at Organic Semiconductor Interfaces
Abstract: The exploration and understanding of the crystallization, growth and the orientation of organic molecules on substrates is a very important feature in fundamental as well as applied research in the various fields of organic electronic device research. It is well known that the ordering and orientation of organic molecules significantly affects the electronic structure and transport properties, and the anisotropy of the transport properties in organic semiconductor thin films in particular has to be taken into account. It is, however, not only the orientation of the film as a whole that is important, but the molecular orientation in the few layers near an interface to other device layers that may affect the electronic properties, such as the electronic trap states, contact resistances or interface dipoles.
In this lecture, I will discuss our efforts in investigating charge and photogenerated transport at organic nanocrystalline interfaces. For example, we have synthesized single-crystalline donor-acceptor nanowire devices (i.e. transistors, solar-cells) that have enabled us to demonstrate excitonic charge splitting and ambipolar charge transport at p-n nanointerfaces. The use of organic single-crystalline devices will have a major impact in accelerating the emerging area of organic electronics, as these highly ordered systems will enable one to extract intrinsic charge carrier transport phenomena that cannot be accurately determined from disordered systems common to amorphous and/or polycrystalline films used in mainstream devices.
Figure. An organic single-crystal p-n junction nanowire solar cell.
Biography: Alejandro Briseno was born and raised in Los Angeles, California. He received his B.S from California State University, Los Angeles. While at Cal State LA, he carried out research on conducting polymer vapor sensors in the lab of Professor Nathan S. Lewis at nearby Caltech. In 2006, he completed his Master’s Degree in chemistry at UCLA with Professor Fred Wudl on the synthesis and charge transport of small-molecule conductors. His Ph.D research on organic semiconductor solids was supported by a Bell Labs-Lucent Technologies Fellowship under the supervision of Professor Younan Xia at the University of Washington. Alejandro subsequently did a one-year postdoc at UC Berkeley with Professor Peidong Yang where he focused on inorganic/organic hybrid nanowire solar cells. In 2009, he joined the Department of Polymer Science and Engineering at the University of Massachusetts Amherst, where his research is centered on the synthesis of organic and polymer semiconductors, interfacial crystallization, and fundamental charge transport in organic electronic devices.
Professor Briseno is the recipient of the 3M Non-tenured Award, the Office of Naval Research Young Investigator Program Award, an NSF Polymer Division grant, the UMass Faculty Exceptional Merit Award, and the Presidential Early Career Award for Scientists and Engineers (PECASE). Professor Briseno is also recognized for his nationwide efforts in mentoring underprivileged students. He has over 50 publications and has delivered domestic and international invited lectures on nearly 50 occasions, and joined the editorial board of Materials Today and ACS Applied Materials and Interfaces.
Faculty Host: Ramesh Jasti
Student Host: Constantinos Katevatis