Exciton migration is an important process for light harvesting with organic systems and often the bottleneck. Especially the formation of trap states hinders the mobility considerably. Although excimer excitons are often referred to as traps, their mobility has been demonstrated while their nature is still unclear. Here, we compare the mobility of singlet and excimer excitons in nanoparticles consisting of the same type of perylene bisimide molecules. By changing the preparation conditions, nanoparticles with different intermolecular coupling strengths are prepared. Femtosecond transient absorption spectroscopy reveals the formation of excimer excitons from Frenkel excitons. The mobility of both exciton types is determined by evaluating exciton-exciton annihilation processes. In the lower coupling regime, singlet mobility is observed, whereas for stronger coupling the dynamics is dominated by a 10-fold increased excimer mobility. The excimer mobility can thus even be higher than the singlet mobility and is affected by the intermolecular electronic coupling.
|Number of pages||7|
|Journal||Journal of Physical Chemistry Letters|
|State||Published - May 18 2023|
Bibliographical noteFunding Information:
The authors acknowledge the use of Princeton’s Imaging and Analysis Center, which is partially supported through the Princeton Center for Complex Materials (PCCM), a National Science Foundation (NSF)-MRSEC program (DMR-2011750). Financial support by the Deutsche Forschungsgemeinschaft via SFB 1477 “Light-Matter Interactions at Interfaces”, project number 441234705, is gratefully acknowledged. C.R. is thankful to the Friedrich-Naumann Foundation for a graduate scholarship. The help of Falk-Erik Wiechmann for of the Supporting Information is acknowledged.
© 2023 American Chemical Society.
ASJC Scopus subject areas
- Materials Science (all)
- Physical and Theoretical Chemistry