Function :              Intern

Contract :             CNRS internship agreement

Starting date:      February to April 2026

Duration:               6 months

Workplace:           LPICM (Laboratoire de Physique des Interfaces et des Couches Minces), Palaiseau, France

Education:            Master 2 – 3rd years engineering students

LPICM and IPVF

LPICM (Laboratoire de Physique des Interfaces et des Couches Minces) is a research laboratory under the dual supervision of the CNRS, and the École Polytechnique. Founded in 1986, the LPICM studies a wide range of physics fields, including numerical modeling for medical imaging applications, the study of 2D- structured semiconductors, and plasma processing of semiconductors, among others. In particular, one of the LPICM teams focuses on the fabrication of silicon solar cells, mainly using the PE-CVD (Plasma-Enhanced Chemical Vapor Deposition) method.

https://lpicm.cnrs.fr/

IPVF is a scientific and technical pole dedicated to the research and development of solar technologies. It permanently hosts its own staff, as well as the employees of its partners and external companies. IPVF aims to become one of the world’s leading centers for research, innovation, and training in the field of energy transition.
IPVF primary objective is to improve the performance and competitiveness of photovoltaic cells and develop breakthrough technologies by relying on four levers:

• Ambitious research program.
• The hosting of more than 200 researchers and their laboratories on its Paris-Saclay site.
• A state-of-the-art technology platform (8,000 m²) open to the photovoltaic industry actors, with more than 100 state-of-the-art equipment units located in clean rooms.
• A training program mainly based on a master’s degree, the supervision of PhD students, and continuing education.

CONTEXT

As part of the IOTA project within the PEPR TASE program, the CNRS is working on the development of tandem solar cells. (https://www.pepr-tase.fr/projet/iota/).

Tandem solar cells are an architecture where multiple solar cells, with different band gap absorber materials are connected in series. This configuration allows one to utilize more of the energy of the absorbed photons, therefore to achieve higher efficiencies than single junction solar cells.

This study focuses specifically on silicon-perovskite tandem cells, to combine the well-known and industrialized silicon cell technology with an emerging technology, the metal halide perovskite cells.

One part of the perovskite cell is the Hole Transport Layer (HTL), whose role is to extract the holes from the absorber, being selective to the electrons. This layer has to be transparent below 1,7eV, to be conductive enough, to have a band structure compatible with the perovskite and selective to the electrons, and if possible, to present a passivation effect regarding the perovskite. The material choice therefore requires compromises to be made. Or, and this is the solution explored here, optical and electrical requirements could be decorrelated using innovative bifunctional layers. This means the HTL would be composed of two materials. The first one, locally deposited in small dots, ensuring the electrical requirements, and the other, filling the gap between the small dots, ensuring the transparency and passivation effects needed.

From a fabrication point of view, achieving this structure requires the control of localized metal oxide deposition processes (e.g. Al2O3, ZnO, etc…).

The intern will make use of thin film deposition processes from two techniques, namely Atomic Layer Deposition (ALD) and Plasma-Enhanced Chemical Vapor Deposition (PE-CVD). The expertise in thin film deposition and characterization as well as preliminary studies will serve as a basis to the project.

The intern will join the Silicon team at the LPICM, and will therefore have access to the different equipment of the laboratory. If necessary, the IPVF platform may also be used, particularly for ALD (Atomic Layer Deposition) processes.

MAIN MISSIONS

The main tasks of the internship will be to :

1) Identify the most suitable process for localized metal oxide deposition, taking into account the ease of processing, the available equipment and the tunability of the process, especially the hole size and the hole-to-hole Different strategies have been considered:

– Using Polystyrene (PS) particles as support during an etching step

– Using Polystyrene (PS) particles as mask during a deposition step 

– Using Self Assembled Molecules (SAM’s) to prevent thin film growth

Any other strategies, based on the intern’s bibliographic research, may also be considered.

2) Establish a detailed protocol for the production of these thin films and implement the protocol.

For example, the process to deposit polystyrene particles (or SAM’s) on surfaces is currently mastered by partner laboratories, but is not commonly used at LPICM. The intern will therefore learn how to perform this type of process and adapt it to the laboratory conditions and to the requirements. The choice of deposition method for the metal oxide will also need to be studied by the intern, regarding the temperature, the material, the external constraints, …

3) Characterize the deposited films by a set of thin film characterization techniques to :

– Assess the deposited thickness using ellipsometry of X-ray Fluorescence (XRF)

– Assess the properties and the crystallinity of the material, using X-Ray Diffraction (XRD), UV-Visible Spectrophotometry, X-Ray Reflectometry (XRR)

– Assess the selectivity (the quality) of the selective deposition process, using XRF, Ellipsometry or confocal microscopy.

Sources : 

Garin et al, “Direct etching at the nanoscale through nanoparticle-directed capillary condensation”, Nanoscale, 2020, 12, 9240, 10.1039/c9nr10217e

Chia-Hsun Hsu et al, “Low Cost Local Contact Opening by Using Polystyrene Spheres Spin-Coating Method for PERC Solar Cells”, Materials 2016, 9(7), 549; https://doi.org/10.3390/ma9070549

PROFILE

📖 Knowledge and experience

– Knowledge of thin film deposition processes

– Familiarity with thin film characterization methods

– Understanding of semiconductor physics

CONTACT

CV, academic transcripts and cover letter to be sent to : yann.pinal@cnrs.fr