Evolution of diffusion coefficient of photoexcited species in excimer forming organic thin films

0519233 - ÚMCH 2021 RIV US eng J - Journal Article
Menšík, Miroslav - Rais, David - Pfleger, Jiří - Toman, Petr
Evolution of diffusion coefficient of photoexcited species in excimer forming organic thin films.
Journal of Physical Chemistry C. Roč. 124, č. 1 (2020), s. 52-59. ISSN 1932-7447. E-ISSN 1932-7455
R&D Projects: GA ČR(CZ) GA17-03984S; GA MŠMT(CZ) LO1507
Institutional support: RVO:61389013
Keywords : diffusion coefficient * time resolved spectroscopy * excimer
OECD category: Polymer science
Impact factor: 4.126, year: 2020
Method of publishing: Limited access
https://pubs.acs.org/doi/abs/10.1021/acs.jpcc.9b08953

The diffusion of photogenerated excitons in organic semiconductors represents often a rate-determining process in the exciton population evolution in ultrafast transient absorption experiments, due to an increased mutual exciton interaction probability at typical excitation densities. A simple description of a diffusion process with a time-independent diffusion coefficient often fails to explain the observed kinetics in the highly nonequilibrium system. In this work, we used the concept of time-dependent diffusion and determined the evolution of the diffusion coefficient of photogenerated excited species in thin films of bis(terpyridine-4′-yl)terthiophene from the experimental ultrafast transient absorption spectroscopic data at a subnanosecond time scale. We show that the diffusion coefficient decreases in time more rapidly with increasing intensity of the photoexcitation. We explain the dependences by the planarization of photoexcited molecules and excimer formation.
Permanent Link: http://hdl.handle.net/11104/0306023