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Femtosecond time-resolved two-photon photoemission studies of ultrafast carrier relaxation in Cu_2O photoelectrodes

Borgwardt, Mario and Omelchenko, Stefan T. and Favaro, Marco and Plate, Paul and Höhn, Christian and Abou-Ras, Daniel and Schwarzburg, Klaus and van de Krol, Roel and Atwater, Harry A. and Lewis, Nathan S. and Eichberger, Rainer and Friedrich, Dennis (2019) Femtosecond time-resolved two-photon photoemission studies of ultrafast carrier relaxation in Cu_2O photoelectrodes. Nature Communications, 10 . Art. No. 2106. ISSN 2041-1723. PMCID PMC6506537. doi:10.1038/s41467-019-10143-x.

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Cuprous oxide (Cu_2O) is a promising material for solar-driven water splitting to produce hydrogen. However, the relatively small accessible photovoltage limits the development of efficient Cu_2O based photocathodes. Here, femtosecond time-resolved two-photon photoemission spectroscopy has been used to probe the electronic structure and dynamics of photoexcited charge carriers at the Cu_2O surface as well as the interface between Cu_2O and a platinum (Pt) adlayer. By referencing ultrafast energy-resolved surface sensitive spectroscopy to bulk data we identify the full bulk to surface transport dynamics for excited electrons rapidly localized within an intrinsic deep continuous defect band ranging from the whole crystal volume to the surface. No evidence of bulk electrons reaching the surface at the conduction band level is found resulting into a substantial loss of their energy through ultrafast trapping. Our results uncover main factors limiting the energy conversion processes in Cu_2O and provide guidance for future material development.

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URLURL TypeDescription CentralArticle ItemData
Borgwardt, Mario0000-0002-1693-7047
Omelchenko, Stefan T.0000-0003-1104-9291
Höhn, Christian0000-0002-2043-598X
van de Krol, Roel0000-0003-4399-399X
Atwater, Harry A.0000-0001-9435-0201
Lewis, Nathan S.0000-0001-5245-0538
Eichberger, Rainer0000-0001-9521-0024
Friedrich, Dennis0000-0003-4844-368X
Alternate Title:Femtosecond time-resolved two-photon photoemission studies of ultrafast carrier relaxation in Cu2O photoelectrodes
Additional Information:© 2019 The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit Received 09 November 2018; Accepted 23 April 2019; Published 08 May 2019. Data availability: The source data underlying Figs. 2a–d and 3 are available in Zenodo, The source data for the Supplementary Figures are available from the corresponding author upon reasonable request. M.B., R.E. and D.F. thank P. Sippel for discussions. M.B. acknowledges funding from the Helmholtz Association through the Excellence network UniSysCat (ExNet-0024-1). This work was supported in part (S.T.O., H.A.A. and N.S.L.) through the Office of Science of the U.S. Department of Energy (DOE) under award no. DE-SC0004993 to the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub. D.F. acknowledges support by the German Research Foundation (DFG), project numbers PAK 981/1 and FR 4025/2-1. Author Contributions: M.B., D.F. and R.E. designed the experiments on samples provided by S.T.O, H.A.A., and N.S.L. M.B. and D.F. carried out the laser experiments and analyzed the data with the help of R. vdK and R.E. M.B., M.F., P.P., C.H. and D.F. performed the LEED and XPS measurements and analyzed the data. D.A.-R. performed the SEM/EDX experiments. K.S. performed the AFM measurements. M.B., R.E. and D.F. prepared the paper. All authors discussed the results and commented on the paper. The authors declare no competing interests.
Group:JCAP, Kavli Nanoscience Institute
Funding AgencyGrant Number
Helmholtz AssociationExNet-0029-1
Department of Energy (DOE)DE-SC0004993
Deutsche Forschungsgemeinschaft (DFG)PAK 981/1
Deutsche Forschungsgemeinschaft (DFG)FR 4025/2-1
Subject Keywords:Chemical physics; Energy; Photocatalysis
PubMed Central ID:PMC6506537
Record Number:CaltechAUTHORS:20190513-072232965
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95415
Deposited By: Tony Diaz
Deposited On:13 May 2019 17:16
Last Modified:25 Feb 2022 17:29

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