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Disentangling the evolution of electrons and holes in photoexcited ZnO nanoparticles

Lookup NU author(s): Dr Thomas PopeORCiD, Professor Thomas Penfold

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

The evolution of charge carriers in photoexcited room temperature ZnO nanoparticles in solution is investigated using ultrafast ultraviolet photoluminescence spectroscopy, ultrafast Zn K-edge absorption spectroscopy, and ab initio molecular dynamics (MD) simulations. The photoluminescence is excited at 4.66 eV, well above the band edge, and shows that electron cooling in the conduction band and exciton formation occur in <500 fs, in excellent agreement with theoretical predictions. The x-ray absorption measurements, obtained upon excitation close to the band edge at 3.49 eV, are sensitive to the migration and trapping of holes. They reveal that the 2 ps transient largely reproduces the previously reported transient obtained at 100 ps time delay in synchrotron studies. In addition, the x-ray absorption signal is found to rise in ∼1.4 ps, which we attribute to the diffusion of holes through the lattice prior to their trapping at singly charged oxygen vacancies. Indeed, the MD simulations show that impulsive trapping of holes induces an ultrafast expansion of the cage of Zn atoms in <200 fs, followed by an oscillatory response at a frequency of ∼100 cm−1, which corresponds to a phonon mode of the system involving the Zn sub-lattice.


Publication metadata

Author(s): Milne CJ, Nagornova N, Pope T, Chen H-Y, Rossi T, Szlachetko J, Gawelda W, Britz A, van Driel T, Sala L, Ebner S, Katayama T, Southworth SH, Doumy G, March AM, Lehmann CS, Mucke M, Iablonskyi D, Kumagai Y, Knopp G, Motomura K, Togashi T, Owada S, Yabashi M, Nielsen MM, Pajek M, Ueda K, Abela R, Penfold TJ, Chergui M

Publication type: Article

Publication status: Published

Journal: Structural Dynamics

Year: 2023

Volume: 10

Online publication date: 03/11/2023

Acceptance date: 06/10/2023

Date deposited: 06/11/2023

ISSN (electronic): 2329-7778

Publisher: AIP Publishing LLC

URL: https://doi.org/10.1063/4.0000204

DOI: 10.1063/4.0000204

Data Access Statement: The data that support the findings of this study are openly available in Zenodo at https://zenodo.org/record/8150479, Ref. 66.


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Funding

Funder referenceFunder name
Comunidad de Madrid and Universidad Autónoma de Madrid (Grant No. SI2/PBG/2020-00003)
EPSRC
ERC
EP/W008009/1
EP/X035514/1
JSPS KAKENHI (Grant Nos. JP19H05782)
JSPS KAKENHI (Grant Nos. JP21K18944)
Marie Heim-Vögtlin grant
IMDEA-Nanociencia (Grant No. CEX2020-001039-S)
JSPS KAKENHI (Grant Nos. JP21H04974)
National Science Centre in Poland (SONATA BIS 6 Grant No. 2016/22/E/ST4/00543)
Spanish MICIU (Grant No. PID2019-108678GB-I00)
Polish Ministry and Higher Education Project No. 1/SOL/2021/2
U.S. Department of Energy Contract No. DE-AC02-06CH11357
Spanish MIU (Grant No. BEAGAL18/00092)
Swiss SNF

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