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Surface and interface physics in hybrid and organic electronics

Participants : Nadine Witkowski, Hervé Cruguel

Collaborations  : Morten Madsen, University of Southern Denmark, Synchrotrons (Soleil, BESSY, Elettra, MAXIV)

The goal of this research activity is to study the electronic structure of interfaces in solar cells based on organic compounds, to understand the mechanisms that promote or limit charge transfer within the device. The interfaces are prepared in-situ under vacuum by thermal evaporation or electrospray deposition of sensitive organic molecules. We are particularly interested in the oxide layers carrying positive or negative charges and their interfaces with active semiconductor organic molecules. The oxide layers are prepared at low temperature in the group of Prof. Morten Madsen and sent to the INSP for study of the physic properties.

JPEG Left : Work function (a, b), valence band (c), 3d core level of Mo as a function of annealing temperature of molybdenum oxide ; right : structural model of the oxide layer [3]

An important part of our activity at INSP is to study the electronic structure of these materials by combining in-situ techniques of optical and electronic spectroscopies. In particular, we carry out photoemission measurements in the laboratory or on synchrotrons to understand the band alignment at the interfaces as well as the electronic coupling between the layers. These spectroscopic studies are linked to structural studies by X-ray diffraction and local probe microscopy to understand how the structure and nature of interfaces can influence the performance of devices.

PhD project

  • Dylan Amelot, 2018-2021
  • Mariam Ahmad, 2020-2023 co-supervision with Southern Denmark University (SMART – Structures of Materials in Real Time, Ministry of Higher Education and Science (UFM))

Publications

[1] Sputter-Deposited Titanium Oxide Layers as Efficient Electron Selective Contacts in Organic Photovoltaic Devices, M. Mirsafaei, P. Bomholt Jensen, M. Ahmadpour, H. Lakhotiya, J. Lundsgaard Hansen, B. Julsgaard, H.-G. Rubahn, R. Lazzari, N. Witkowski, P. Balling, M. Madsen, ACS Appl. Energy Mater. 2020, 3, 1, 253-259 https://doi.org/10.1021/acsaem.9b01454

[2] Crystalline molybdenum oxide layers as efficient and stable hole contacts in organic photovoltaic devices, M. Ahmadpour, A. L. Fernandes Cauduro, C. Méthivier, B. Kunert, R. Resel, V. Turkovic, H.-G. Rubahn, N. Witkowski, A. K. Schmid and M. Madsen, ACS Appl. Energy Mater., (2019), 2 (1), pp 420–427 DOI : 10.1021/acsaem.8b01452

[3] Crystalline Molybdenum Oxide Thin-Films for Application as Interfacial Layers in Optoelectronic Devices, A. L. F. Cauduro, R. dos Reis, G. Chen, A. K. Schmid, C. Méthivier, H.-G. Rubahn, L. Bossard-Giannesini, H. Cruguel, N. Witkowski, and M. Madsen, ACS Appl. Mater. Interfaces, 9, 7717 (2017) DOI : 10.1021/acsami.6b14228