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Direct Observation of Ultrafast Singlet Exciton Fission in Three Dimensions

Published version
Peer-reviewed

Type

Article

Change log

Authors

Ashoka, Arjun 
Gauriot, Nicolas 
Schnedermann, Christoph  ORCID logo  https://orcid.org/0000-0002-2841-8586

Abstract

We present quantitative ultrafast interferometric pump-probe microscopy capable of tracking of photoexcitations with sub 10 nm spatial precision in three dimensions with 15 fs temporal reso- lution, through retrieval of the full transient photoinduced complex refractive index. We use this methodology to study the spatiotemporal dynamics of the quantum coherent photophysical process of ultrafast singlet exciton fission. Measurements on microcrystalline pentacene films grown on glass (SiO2) and boron nitride (hBN) reveal a 25 nm, 70 fs expansion of the joint-density-of-states along the crystal a,c-axes accompanied by a 6 nm, 115 fs change in the exciton density along the crystal b-axis. We propose that photogenerated singlet excitons expand along the direction of max- imal orbital π-overlap in the crystal a,c-plane to form correlated triplet pairs, which subsequently electronically decouples into free triplets along the crystal b-axis due to molecular sliding motion of neighbouring pentacene molecules. Our methodology lays the foundation for the study of three dimensional transport on ultrafast timescales.

Description

Keywords

5108 Quantum Physics, 51 Physical Sciences

Journal Title

Nature Communications

Conference Name

Journal ISSN

2041-1723
2041-1723

Volume Title

13

Publisher

Nature Research
Sponsorship
Engineering and Physical Sciences Research Council (EP/M006360/1)
European Research Council (758826)
EPSRC (EP/W017091/1)
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