Friday, 17 May 2013 at 11:30am
Room 1400 Biomedical and Physical Sciences Bldg.
Refreshments at 11:30
Speaker: Mark Thompson, Department of Chemistry, University of Southern California
Title: Exciton Management in Organic Solar Cells
Abstract:
The exciton is a critical part of each of the processes leading to photocurrents
in Organic PhotoVoltaics (OPVs), and being able to control the location,
lifetime and energy of the exciton is essential to achieving high efficiency.
We have investigated methods for tuning exciton energies and controlling their
migration paths, both intramolecularly and within a thin film. I will discuss
our most recent work with both organic dyes, such as squaraines and dipyrrins
as well as porphyrinic materials for OPVs. This involves a careful materials
design study that leads to both low energy absorption (into the nearIR) and
the efficient use of multiple absorbers to efficiently harvest photons through
the entire visible spectrum. To that end we have used transient absorption
spectroscopy and measured the rates of singlet and triplet energy transfers
between organic dyes (BODIPY and tetracenes). Both intra- and inter-molecular
energy transfers take place on the picoseconds time scale. Thus, the systems
are fully equilibrated into the lowest energy triplet state(s) before
nonradiative decay. Using this approach we can efficiently harvest energy
across the visible and into the NIR. I will also discuss our latest results
with new singlet fission materials for efficient light harvesting in OPVs.
Our control of singlet and triplet excitons has been important in exploring
the use of singlet fission to enhance the efficiencies of OPVs.
Speaker Bio:
Dr. Mark E. Thompson is Professor of Chemistry and Materials Science at the
University of Southern California. He received his B.S. degree in Chemistry
in 1980 (U.C. Berkeley) and his Ph.D. in chemistry in 1985 (California Institute
of Technology). He spent 2 years as a postdoctoral fellow in the Inorganic
Chemistry laboratory at Oxford University. Prof. Thompson took a position in
the chemistry department at Princeton University in 1987, as an assistant
professor. In 1995 he moved his research team to the University of Southern
California, where he is currently a Professor of Chemistry. He has won a
number of awards, including the MRS Medal in 2006, given by the Materials
Research Society, and the Jan Rachman Prize for Outstanding Achievement in
Flat Panel Displays, also in 2006, given by the Society for Information Display.
In 2011 he was named the 12 of the top 100 most influential chemists in the
world by Thomson-Rueters. In 2012 he was received the Alexander von Humboldt
Research Award. He currently has over 250 papers in print and over 125 US
patents. His research interests involve the optical and optoelectronic
properties of molecular materials and devices, particularly organic LEDs
and solar cells, as well as nanoscale materials, catalysis and biosensors.