APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016;
Baltimore, Maryland
Session C24: Time-resolved Energy Transfer and Exciton Transport in Nanostructures
2:30 PM–5:30 PM,
Monday, March 14, 2016
Room: 323
Sponsoring
Unit:
DMP
Chair: Maxim Sukharev, Arizona State University
Abstract ID: BAPS.2016.MAR.C24.5
Abstract: C24.00005 : Measuring Exciton Migration in Conjugated Polymer Films with Ultrafast Time Resolved Stimulated Emission Depletion Microscopy
3:42 PM–4:18 PM
Preview Abstract
Abstract
Author:
Samuel Penwell
(UC Berkeley)
Conjugated polymers are highly tunable organic semiconductors, which can be
solution processed to form thin films, making them prime candidates for
organic photovoltaic devices. One of the most important parameters in a
conjugated polymer solar cell is the exciton diffusion length, which depends
on intermolecular couplings, and is typically on the order of 10 nm. This
mean exciton migration can vary dramatically between films and within a
single film due to heterogeneities in morphology on length scales of 10's to
100's nm. To study the variability of exciton diffusion and morphology
within individual conjugated polymer films, we are adapting stimulated
emission depletion (STED) microscopy. STED is typically used in biology with
sparse well-engineered fluorescent labels or on NV-centers in diamond. I
will, however, describe how we have demonstrated the extension of STED to
conjugated polymer films and nanoparticles of MEH-PPV and CN-PPV, despite
the presence of two photon absorption, by taking care to first understand
the material's photophysical properties. We then further adapt this
approach, by introducing a second ultrafast STED pulse at a variable delay.
Excitons that migrate away from the initial subdiffraction excitation volume
during the ps-ns time delay, are preferentially quenched by the second STED
pulse, while those that remain in the initial volume survive. The resulting
effect of the second STED pulse is modulated by the degree of migration over
the ultrafast time delay, thus providing a new method to study exciton
migration. Since this technique utilizes subdiffraction optical excitation
and detection volumes with ultrafast time resolution, it provides a means of
spatially and temporally resolving measurements of exciton migration on the
native length and time scales. In this way, we will obtain a spatiotemporal
map of exciton distributions and migration that will help to correlate the
energetic landscape to film morphology at the nanoscale.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2016.MAR.C24.5