PhD subjects

Perovskite solar cells (PSCs) have become a trending technology in photovoltaic research due to a rapid increase in efficiency in recent years. In 2020, a record efficiency of 25.5% close from Shockley-Queisser theoretical limit of 30% was reported. Tandem solar cells offer an alternative to go beyond but stability still remains an issue.

In our project, we will bring together our complementary expertise in molecular and macromolecular syntheses, thin film morphology tuning and cell device engineering to improve the stability of highly efficient inverted perovskite cells using new electron transport layers (ETL) with high electron mobility and high stability. We will design and synthesize new n-type fullerene free semiconductors. Introduction of cross-linkable groups will lead to stabilized ETLs by thermally-induced cross-linking after film formation. The efficiency and stability of these ETLs will be finally evaluated through their incorporation in tandem configuration.

This thesis project aims to exfoliate new nanostructured architectures based on two-dimensional inorganic phases. These nanostructures will be designed for filtration devices and tested using our microfluidic platform. The target application is water purification and the selective separation of metal ions. The doctoral student will interact with chemists, physicists and electrochemists in a real multidisciplinary environment, on a fundamental research subject directly connected to application needs. Thus, during his thesis, the student will be exposed to a multidisciplinary environment and brought to carry out experiments in various fields such as inorganic chemistry, physical chemistry, micro / nano-fabrication and nano-characterization methods. In In this context, this project should potentially lead to significant societal benefits.

For the realization of the latter, he will have access to a very wide and varied range of equipment ranging from optical microscopes to the latest generation synchrotron (ESRF), including field effect or electron microscopes and galvanostats.

This thesis is therefore an excellent opportunity for professional growth, both in terms of your knowledge and your skills.

Since the 1950s, the use of petroleum-based plastics has created a modern consumerist world based on the use of disposable products. Global production of plastic waste is therefore considerable, and has almost doubled in just 20 years, now reaching 350 million tonnes a year. This non-biodegradable plastic waste causes a great deal of environmental pollution (disturbance of flora and fauna, water and soil pollution, etc.). Barely 9% of this waste is recycled, the rest being burnt or landfilled. The health, climate and social problems inherent in this linear economy mean that we need to create a circularity for these materials by developing effective and robust recycling routes. While current recycling methods rely mainly on mechanical processes and are limited to specific types of waste (e.g. plastic water bottles), the development of chemical recycling methods seems promising for treating waste for which there are no recycling channels. Such chemical processes make it possible to recover the carbonaceous matter in plastics in order to regenerate new plastics.
Within this objective of material circularity, this doctoral project aims to develop new chemical recycling routes for mixed oxygen/nitrogen plastic waste such as polyurethanes (insulation foam, mattresses, etc.) and polyamides (textile fibres, circuit breaker boxes, etc.), for which recycling routes are virtually non-existent. This project is based on a strategy of depolymerizing these plastics by the selective cleavage of the carbon-oxygen and/or carbon-nitrogen bonds to form the corresponding monomers or their derivatives. To do that, catalytic systems involving metal catalysts coupled with abundant and inexpensive reducing agents, such as alcohols and formic acid, will be developed. The use of dihydrogen, an industrial reducing agent, will also be considered. In order to optimize these catalytic systems, we will seek to understand how they proceed and the mechanisms involved.

With the gradual decarbonization of our economy, only a few isolated sources of CO2 emissions, such as cement plants, will remain. However, our long-term dependence on carbon-based products, such as fuels for aviation and heavy transport, as well as various chemicals and polymers, will persist. To produce these essential molecules, it will be crucial to capture carbon in the form of diluted CO2 from the atmosphere and transform it into useful molecules.

Currently, technologies for the direct capture of CO2 from the air (DAC) are being developed separately from those for CO2 conversion, although their integration could offer significant energy savings, notably by avoiding the energy-intensive thermal desorption stage. The major scientific challenge lies in the development of innovative CO2 conversion methods capable of operating with extremely low CO2 concentrations and/or transforming CO2 directly into its capture medium; for example, in low-reactivity forms such as carbonates or carbamates. The project aims to develop molecular catalysts capable of converting CO2 in very dilute environments, thus producing sustainable molecules and fuels.

Nuclear Nuclear magnetic resonance (NMR) is a robust, non-invasive technique of analysis. It provides valuable information about chemical reactions, which can then be better characterised and optimised. However, NMR is poorly sensitive, and low-concentrated solutes, such as intermediates of reaction, may be unobservable by conventional NMR. One method known to drastically but temporarily increase the sensitivity of NMR is to create a hyperpolarised state in the system of nuclear spins, i.e. a polarisation much greater than that accessible with available magnetic fields. One hyperpolarisation method uses the specific properties of parahydrogen. A catalyst is required to add parahydrogen to a multiple bond or a metal.

The present thesis will investigate the combined contribution of (i) parahydrogen-based hyperpolarisation [1], (ii) the grafting of the appropriate catalyst onto nanoparticles [2], and (iii) a continuous analysis method [3] to detect and identify chemical intermediates, areas in which the laboratory has acquired experience. This subject involves a major investment in instrumentation, as well as skills in synthetic chemistry and NMR.

The thesis will be carried out at NIMBE, a joint CEA/CNRS unit at CEA Saclay. The hyperpolarised NMR and the synthesis will take place under the respective responsibility of Gaspard HUBER, from LSDRM, and Stéphane CAMPIDELLI, from LICSEN. These two NIMBE laboratories are located in nearby buildings.

References:
[1] Barskiy et al, Prog. Nucl. Magn. Reson. Spectrosc. 2019, 33, 114-115,.
[2] Hijazi et al., Org. Biomol. Chem., 2018, 16, 6767-6772.
[3] Carret et al., Anal. Chem. 2018, 90, 11169-11173.

Glycomics involves identifying oligosaccharides (OS) present in a biological fluid as a source of biomarkers for diagnosing various pathologies (cancers, Alzheimer's disease, etc.). To study these OS, sample preparation involves 2 key phases, enzymatic cleavage (breaking the bond between OS and proteins) followed by purification and extraction (separation of OS and proteins). However, the materials currently used in the protocols impose numerous manual and time-consuming steps, incompatible with high-throughput analysis.

In this context, the LEDNA laboratory specialized in materials science has recently developed a sol-gel process for the manufacture of Hierarchical Porosity Monoliths (HPMs) in miniaturized devices. These materials have provided a proof of concept demonstrating their value for the second stage of glycomic analysis, i.e. the purification and extraction of oligosaccharides. The LEDNA is now looking to improve the first step, corresponding to enzymatic cleavage, which has become a limiting factor in the glycomics analysis process. Functionalization of porous materials, in particular HPMs, with enzyme would enable simple sample preparation in just a few hours with a single step.

The aim of this thesis is therefore to show that the use of porous materials with a dual function - catalytic and filtration - applied to the preparation of samples for glycomic analysis is a relevant means of simplifying and accelerating glycomic analysis, as well as employing them in hospital-related studies to identify new biomarkers of pathologies.

The research project will involve developing a device incorporating porous materials with catalytic and filtration functions. Several aspects will be addressed, ranging from the synthesis and shaping of these materials to characterization of their textural and physico-chemical properties. Particular emphasis will be placed on enzyme immobilization. The most promising prototype(s) will be evaluated in a glycomic analysis protocol, verifying the oligosaccharide profiles obtained from human biofluids (plasma, milk). Physico-chemical characterization will involve a variety of techniques (SEM, TEM, etc.), as well as characterization of porosity parameters (nitrogen adsorption, Hg porosimeter). Oligosaccharides will be analyzed by high-resolution mass spectrometry (mainly MALDI-TOF).

For this multidisciplinary thesis project, we are looking for a student chemist or physical chemist, interested in materials chemistry and motivated by the applications of fundamental research in the field of new technologies for health. The thesis will be carried out in two laboratories, LEDNA for the materials part and LI-MS for the use of materials in glycomics analysis. The research activity will be carried out at the Saclay research center (91).

Graphene as a constituent of graphite was close to us for almost 500 years. However, it is only in 2005 that A. Geim and K. Novoselov (Nobel Prize in 2010) reported for the first time the obtaining of a nanostructure composed by a single layer of carbon atom. The exceptional electronic properties of graphene make it a very promising material for applications in electronic and renewable energies.

For many applications, one should be able to modify and control precisely the electronic properties of graphene. In this context, we propose to synthesize chemically graphene nanoparticles and study their absorption and photoluminescence properties. We will focus on their solubilty in water in order to study potential applications in biology. This project will be developed in collaboration with Physicists so the candidate will work in a multidisciplinary environment.

Despite their many positive impacts, PV panels production face threat of sustainability of growth in terms of raw materials, energy, and environment. The PV industry is very dependent on critical raw materials and this dependence is getting worse as the production and consumption of solar panels are increasing considerably.

The main goal of this project is to develop the next generation of transparent/non-transparent conductive layers based on non- critical raw materials. These layers will be used as contact, interconnections in innovative solar panels. Guiding principle of this project is to construct competitive high quality/low-cost conductive line to replace silver contact. Due to these outstanding properties, Graphene could play an essential role in replacing critical material and enhancing electrical conductivity. This Ph-D project will be devoted to the development of low and high temperature conductive graphene inks. These inks will be designed for serigraphy, inkjet, or any suitable low-cost printing deposition techniques to print contact and interconnection. i) Inks properties in terms of composition, viscosity will be tuned. ii) The behavior of printed conductive ink will be investigated after being exposed to different stress (mechanical, temperature, moisture, electrical, light, oxygen….). iii) Finally the focus will be on conductivity characterization as a function of electrode morphology (thickness, porosity, …) and mechanical resistance. The overall aim is to optimize conductivity, mechanical resistance, and durability and finally incorporate these improvement in perovskite solar cells.