Center for Excitonics
Seminar Series Announcement
The Center for Excitonics (
http://www.rle.mit.edu/excitonics) invites you
to join us at the
first seminar of the Fall 2009 series. Please forward this information on
to others who might be interested
in attending this seminar.
Title: The Role of Intermolecular Coupling in
the Photophysics of
Disordered Organic Semiconductors
Presenter: Professor Frank Spano
Organization: Department of Chemistry, Temple University
Date: October 6, 2009
Time: 3:00 - 4:00pm
Place: 36-428
Refreshments: Yes
URL:
http://www.rle.mit.edu/excitonics/spano-100609.html
abstract
Electronic excitations in aggregates, thin films and crystals of
conjugated organic molecules play a fundamental
role in the operation of a wide array of organic-based devices including
solar cells, transistors and light-emitting diodes.
Optical excitations are generally delocalized excitons, the spatial
extents of which are determined by the delocalizing influence
of resonant intermolecular coupling and the localizing influence of static
and dynamic disorder. Due to the “soft” nature of organic
materials the electronic excitations are also accompanied by significant
nuclear relaxation. In this talk we show how a theory based
on the Holstein Hamiltoian represented in a multiparticle basis set can be
used to understand absorption and emission in a range of
organic materials including self-assembled carotenoid aggregates and
poly(3-hexylthiophene) thin films. We discuss the mechanism
whereby the vibronic progression based on the vinyl stretching mode is
distorted away from the usual Poissonian distribution upon
aggregation and show how the distortion can be analyzed to extract the
exciton bandwidth, the exciton coherence length, and parameters
describing the nature of disorder.
bio
Frank Spano got his start at Middlesex County College where in 1980 he
received an Associate in Science Degree. He then transferred
to Lehigh University majoring in Physics, graduating in 1982 with a BS
degree. However, the lure of Chemistry was too strong and in
1982 Spano entered the Graduate Program in Chemistry at Princeton
University where he worked with Prof. Warren S. Warren on theory
and experimentation in the area of Coherent Transient Spectoscopy. After
obtaining a PhD in 1988, Spano went to the University of Rochester
as a post doctoral associate with Prof. Shaul Mukamel working on the
theory of condensed phase nonlinear optics. In 1990 Spano began his
academic career at Temple University where he remains to this day.
n aggregation and show how the distortion can be analyzed to exctact the
exciton bandwidth, the exciton coherence length, and parameters describing
the nature of disorder.