Experimental Observation of Strong Exciton Effects in Graphene Nanoribbons

Alexander Tries; Silvio Osella; Pengfei Zhang; Fugui Xu; Charusheela Ramanan; Mathias Kläui; Yiyong Mai; David Beljonne; Hai I. Wang

doi:10.1021/acs.nanolett.9b04816

Experimental Observation of Strong Exciton Effects in Graphene Nanoribbons

Alexander Tries
, Silvio Osella
, Pengfei Zhang
, Fugui Xu
, Charusheela Ramanan
, Mathias Kläui
, Yiyong Mai
, David Beljonne
, Hai I. Wang

Research output: Contribution to Journal › Article › Academic › peer-review

Abstract

Graphene nanoribbons (GNRs) with atomically precise width and edge structures are a promising class of nanomaterials for optoelectronics, thanks to their semiconducting nature and high mobility of charge carriers. Understanding the fundamental static optical properties and ultrafast dynamics of charge carrier generation in GNRs is essential for optoelectronic applications. Combining THz spectroscopy and theoretical calculations, we report a strong exciton effect with binding energy up to ∼700 meV in liquid-phase-dispersed GNRs with a width of 1.7 nm and an optical band gap of ∼1.6 eV, illustrating the intrinsically strong Coulomb interactions between photogenerated electrons and holes. By tracking the exciton dynamics, we reveal an ultrafast formation of excitons in GNRs with a long lifetime over 100 ps. Our results not only reveal fundamental aspects of excitons in GNRs (strong binding energy and ultrafast exciton formation etc.) but also highlight promising properties of GNRs for optoelectronic devices.

Original language	English
Pages (from-to)	2993-3002
Number of pages	10
Journal	Nano Letters
Volume	20
Issue number	5
DOIs	https://doi.org/10.1021/acs.nanolett.9b04816
Publication status	Published - 13 May 2020
Externally published	Yes

Funding

This work was financially supported by the DFG (Priority Program Graphene SPP 1459, SFB TRR 173 Spin+X) and the Max Planck Society. The authors thank Ivan Ivanov, Xiaoyu Jia, Paniz Soltani, and Wenhao Zheng for fruitful discussions, Hansjörg Menges and Walter Scholdei for excellent technical support, and Keno Krewer for help with the fitting routines. A.T. is a recipient of a fellowship through the Excellence Initiative by the Graduate School Materials Science in Mainz (GSC 266). Y.M. is grateful for the financial support from the National Natural Science Foundation of China (21774076) and the Program of Shanghai Academic Research Leader (19XD1421700). Y.M. also appreciates the Instrumental Analysis Center at Shanghai Jiao Tong University for some analyses. For the computational time, S.O. thanks the Interdisciplinary Center for Mathematical and Computational Modelling (ICM, University of Warsaw) under the GA53-8, GA73-16, and GA76-5 computational grants. The work in Mons has been supported by the FNRS-FRFC and Consortium des Equipements de Calcul Intensif—CECI. D.B. is a research director of FNRS. This work was financially supported by the DFG (Priority Program Graphene SPP 1459, SFB TRR 173 Spin+X) and the Max Planck Society. The authors thank Ivan Ivanov, Xiaoyu Jia, Paniz Soltani and Wenhao Zheng for fruitful discussions, Hansjorg Menges and Walter Scholdei for excellent technical support, and Keno Krewer for help with the fitting routines. A.T. is a recipient of a fellowship through the Excellence Initiative by the Graduate School Materials Science in Mainz (GSC 266). Y.M. is grateful for the financial support from the National Natural Science Foundation of China (21774076) and the Program of Shanghai Academic Research Leader (19XD1421700). Y.M. also appreciates the Instrumental Analysis Center at Shanghai Jiao Tong University for some analyses. For the computational time, S.O. thanks the Interdisciplinary Center for Mathematical and Computational Modelling (ICM, University of Warsaw) under the GA53-8, GA73-16, and GA76-5 computational grants. The work in Mons has been supported by the FNRS-FRFC and Consortium des Equipements de Calcul Intensif—CECI. D.B. is a research director of FNRS.

Funders	Funder number
CECI
Consortium des Equipements de Calcul Intensif
FNRS-FRFC
Graduate School Materials Science in Mainz	GSC 266
Instrumental Analysis Center at Shanghai Jiao Tong University
Deutsche Forschungsgemeinschaft
National Natural Science Foundation of China	21774076
Fonds De La Recherche Scientifique - FNRS
Max-Planck-Gesellschaft
Uniwersytet Warszawski	GA53-8, GA73-16
Program of Shanghai Academic Research Leader	19XD1421700
Institut de Cardiologie de Montréal
Interdyscyplinarne Centrum Modelowania Matematycznego i Komputerowego UW

Keywords

Exciton binding energy
Exciton formation
Excitons
Graphene nanoribbons
THz spectroscopy

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title = "Experimental Observation of Strong Exciton Effects in Graphene Nanoribbons",

abstract = "Graphene nanoribbons (GNRs) with atomically precise width and edge structures are a promising class of nanomaterials for optoelectronics, thanks to their semiconducting nature and high mobility of charge carriers. Understanding the fundamental static optical properties and ultrafast dynamics of charge carrier generation in GNRs is essential for optoelectronic applications. Combining THz spectroscopy and theoretical calculations, we report a strong exciton effect with binding energy up to ∼700 meV in liquid-phase-dispersed GNRs with a width of 1.7 nm and an optical band gap of ∼1.6 eV, illustrating the intrinsically strong Coulomb interactions between photogenerated electrons and holes. By tracking the exciton dynamics, we reveal an ultrafast formation of excitons in GNRs with a long lifetime over 100 ps. Our results not only reveal fundamental aspects of excitons in GNRs (strong binding energy and ultrafast exciton formation etc.) but also highlight promising properties of GNRs for optoelectronic devices.",

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AU - Tries, Alexander

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AU - Xu, Fugui

AU - Ramanan, Charusheela

AU - Kläui, Mathias

AU - Mai, Yiyong

AU - Beljonne, David

AU - Wang, Hai I.

PY - 2020/5/13

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N2 - Graphene nanoribbons (GNRs) with atomically precise width and edge structures are a promising class of nanomaterials for optoelectronics, thanks to their semiconducting nature and high mobility of charge carriers. Understanding the fundamental static optical properties and ultrafast dynamics of charge carrier generation in GNRs is essential for optoelectronic applications. Combining THz spectroscopy and theoretical calculations, we report a strong exciton effect with binding energy up to ∼700 meV in liquid-phase-dispersed GNRs with a width of 1.7 nm and an optical band gap of ∼1.6 eV, illustrating the intrinsically strong Coulomb interactions between photogenerated electrons and holes. By tracking the exciton dynamics, we reveal an ultrafast formation of excitons in GNRs with a long lifetime over 100 ps. Our results not only reveal fundamental aspects of excitons in GNRs (strong binding energy and ultrafast exciton formation etc.) but also highlight promising properties of GNRs for optoelectronic devices.

AB - Graphene nanoribbons (GNRs) with atomically precise width and edge structures are a promising class of nanomaterials for optoelectronics, thanks to their semiconducting nature and high mobility of charge carriers. Understanding the fundamental static optical properties and ultrafast dynamics of charge carrier generation in GNRs is essential for optoelectronic applications. Combining THz spectroscopy and theoretical calculations, we report a strong exciton effect with binding energy up to ∼700 meV in liquid-phase-dispersed GNRs with a width of 1.7 nm and an optical band gap of ∼1.6 eV, illustrating the intrinsically strong Coulomb interactions between photogenerated electrons and holes. By tracking the exciton dynamics, we reveal an ultrafast formation of excitons in GNRs with a long lifetime over 100 ps. Our results not only reveal fundamental aspects of excitons in GNRs (strong binding energy and ultrafast exciton formation etc.) but also highlight promising properties of GNRs for optoelectronic devices.

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Experimental Observation of Strong Exciton Effects in Graphene Nanoribbons

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