Doctoral contract for the synthesis of quaternary quantum dots for photovoltaic cells (M/F)

The Reaction and Process Engineering Laboratory (UMR 7274) is a joint unit of the CNRS and the University of Lorraine created on January 1, 2010 and based in Nancy. Its general scientific objective concerns the study of processes taken as a whole and their complexity. The LRGP develops the scientific and technological knowledge necessary for the design, study, conduct and optimization of complex processes of physico-chemical and biological transformation, matter and energy. The unit has more than 300 people, with nearly 20 CNRS researchers, 80 research teachers, 45 technical and administrative staff and 180 non-permanent staff (contract researchers, 85 PhD students, post-doctoral students, masters).
Host team: Process Engineering Axis

Nowadays, robust solar cells can be constructed, and no fundamental obstacle exists to meet an appreciable portion of our energy needs from solar energy electricity. What is required now is a major advance in engineering. Reducing the cost of solar cells, increasing efficiencies and using environmentally friendly materials are ways to enable the development of the photovoltaic (PV) technology and its important environmental benefits. Achieving high efficiency requires the effective use of the sun's spectrum and especially of the visible and infrared (IR) regions. Among the strategies developed to reach this goal, quantum dots (QDs) constitute one of the leading options. QDs are three-dimensionally confined nanocrystals possessing size-tunable, i.e. controllable, optical and electrical properties, which can be finely designed. Recently, multinary I-III-VI2-based QDs have attracted high interest due to their low toxicity as well as for their light absorption in the visible and in the IR region. These QDs differ from binary ones as a flexible modulation of their band structure is allowed by adjusting their composition. For AgIn(S or Se) QDs, this can be achieved by varying the Ag/In ratio. The optical bandgap can also be tuned by varying the crystallite size. The main objective of this project will be to develop new QD-based PV cells (also called QD-sensitized solar cells (QDSSCs)) using QDs as photoabsorbers for the production of electricity under solar irradiation. Our goal is to achieve power conversion efficiencies (PCEs) above 15%, which constitutes a ground-breaking challenge for heavy metal-free PV cells.
Ag-In-Zn-Se QDs will be prepared via mild aqueous phase based methods. Their composition will be adjusted to span the visible and IR regions (up to 1000 nm). The use of 3-mercaptopropionic acid (MPA) as surface ligand will be privileged as it will favor the adsorption of the QDs on the MO used in PV cells and ensure effective charge transfer injection. Other capping ligands bearing carboxylate and phosphonate functions can be additionally considered. Synthesis methods which allow an easy scale-up of QDs production in the future will also privileged.
After characterization (UV-VIS-NIR absorption, PL and time-resolved PL, TEM, XRD…), Ag-In-Zn-Se and CsSnX3-xYx QDs will be deposited at the surface of TiO2 and their photoconversion behavior and (opto)electronic properties will be characterized in full devices from I-V curves and electrochemical impedance spectroscopy (EIS) measurements.