Direct Observation of Ultrafast Singlet Exciton Fission in Three Dimensions


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
Journal Title
Nature Communications
Conference Name
Journal ISSN
2041-1723
2041-1723
Volume Title
Publisher
Nature Research
Sponsorship
Engineering and Physical Sciences Research Council (EP/M006360/1)
European Research Council (758826)
EPSRC (EP/W017091/1)
Relationships
Is supplemented by: