Missions

Realizing photovoltaic devices that achieve the full potential of the active materials requires profound knowledge of their working mechanism. More precisely, it is of paramount importance to understand which physical and chemical processes govern not only the power conversion efficiency but also their long-term stability. The interfaces between the active film and the charge transport layers are among the most important factors in determining these performance indicators. This holds particularly true for the new generation of emerging thin-film photovoltaics (PV) in the application of perovskite solar cells.[1–3] Our key strategy for enhanced stability in this new technology is the introduction of inorganic / hybrid interlayers to protect the photo-active perovskite film from extrinsic species (e.g. moisture, metal atoms from the electrodes, etc.) and to prevent mobile halide species from diffusing into adjacent layers (Figure 1). As a versatile and industry-relevant method to realize functional protective layers, atomic layer deposition (ALD) stands out.[4,5] Oxide layers made by ALD have been implemented as permeation barriers against moisture infiltration.[6] However, the integration of ALD layers in PSCs requires a careful adaption of the process to prevent damage of the perovskite. In order to develop clear guidelines for the selection of materials/processes, even more rigorous testing routines will be needed and a profound understanding of the chemical interaction must be developed.[7] We hence aim to develop a new strategy for the integration of interlayers from ALD and Molecular Layer Deposition (MLD) to control the interface dynamics, i.e. the physical and chemical process critical for charge collection and operational stability. As the most challenging endeavor is to monitor the evolution of these interfaces during device operation we will investigate the interface dynamics in a dedicated analysis approach to track composition and optoelectronic properties.

[1] P. Schulz, ACS Energy Letters 2018, 3, 1287.
[2] P. Schulz, D. Cahen, A. Kahn, Chem. Rev. 2019, 119, 3349.
[3] J. A. Christians, P. Schulz, et al., Nature Energy 2018, 3, 68.
[4] F. J. Ramos, T. Maindron, S. Bechu, A. Rebai, M. Fregnaux, M. Bouttemy, J. Rousset, P. Schulz, N. Schneider, Sustainable Energy & Fuels 2018, DOI 10.1039/C8SE00282G.
[5] K. O. Brinkmann, T. Gahlmann, T. Riedl, Sol. RRL 2020, 4, 1900332.
[6] K. O. Brinkmann, J. Zhao, N. Pourdavoud, T. Becker, T. Hu, S. Olthof, K. Meerholz, L. Hoffmann, T. Gahlmann, R. Heiderhoff, M. F. Oszajca, N. A. Luechinger, D. Rogalla, Y. Chen, B. Cheng, T. Riedl, Nature Communications 2017, 8, 13938.
[7] N. Mallik, J. Hajhemati, M. Frégnaux, D. Coutancier, A. Toby, S.-T. Zhang, C. Hartmann, E. Hüsam, A. Saleh, T. Vincent, O. Fournier, R. G. Wilks, D. Aureau, R. Félix, N. Schneider, M. Bär, P. Schulz, Nano Energy 2024, 109582.

Activities

We are searching an excellent PhD candidate to reinforce the consortium on interlayer development, characterization, and integration into full perovskite solar cells. The focus will be on the layer synthesis and the analysis of the fundamental properties of the interface when paired with the perovskite photoabsorber. In this project, you will pursue the deposition of metal-oxides directly on top the perovskite to eventually produce multi-layered oxides that will allow us to fine tune the optical, electrical and chemical properties. These metal-oxides will serve a reference and benchmark for the new non-oxide ALD materials, specifically sulfides and nitrides, as alternative interlayers. Finally, we will approach the objective of growing inorganic interlayers by MLD. The goal of this PhD project is to grow homogeneous, dense, conformal layers at low temperatures (<150°C) directly on top of the perovskite active layers without inducing detrimental chemical reactions with the adjacent MHP. To meet this scientific challenge, lab-based measurements will be completed by experiments on synchrotron facilities. Insights from these measurements will be accompanied by modeling to facilitate reliable operando and in situ measurement with this coupled measurement system.
Funded by the bilateral French-German ANR project ALSATIAN, the thesis project is hosted at the Institut Photovoltaique d'Ile de France (IPVF) and embedded in a collaboration between the Institut Lavoisier de Versailles (ILV), the University of Rennes as well as the University of Wuppertal and the Helmholtz-Zentrum Berlin (HZB) in Germany. While your main research activities will be at IPVF, you will have access to the infrastructure in the consortium including feature short research stays at the partnering institutes.

Skills

• Master degree in physical chemistry, materials science or related fields
• Solid foundation in experimental methods for thin-film growth and characterization
• Knowledge of optical and photoemission spectroscopy is an asset
• Strong interest in experimentation on vacuum setups and materials characterization
• Good English language and communication skills
• Curious mind to explore the unknown and acquire new experimental skills
• Experience in and the fabrication optoelectronic device and nanomaterials is a plus

Work Context

The “Institut Photovoltaïque d'Île-de-France” IPVF is a global research center in the field of photovoltaic solar energy, constituted by international PV industry partners (EDF, Total, Air Liquide, Horiba and Riber) and academic research teams (CNRS, Ecole Polytechnique). The primary objective of IPVF is to increase the performance and competitiveness of solar cells and develop new breakthrough technologies. This approach is capture in:
• A dedicated research program spanning fundamental aspects of materials science to integrated technological solutions.
• State-of-the-art laboratories for cutting-edge research on PV devices and materials.
• An education program fostering master and PhD students and seminar series.