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PhD contract : Design of wavelength-selective thermal emitters for very low-gap thermophotovoltaic conversion (M/F)

This offer is available in the following languages:
Français - Anglais

Date Limite Candidature : mercredi 6 juillet 2022

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General information

Reference : UPR3346-NADMAA-066
Workplace : POITIERS
Date of publication : Wednesday, June 15, 2022
Scientific Responsible name : Jérémie DREVILLON - Franck ENGUEHARD
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 September 2022
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

The CNRS, at the Pprime Institute, on the Campus site, as part of the ANR LOW-GAP-TPV research project, is recruiting a PhD student who will carry out a thesis on the design of wavelength-selective thermal emitters for very low-gap thermophotovoltaic conversion.

Skills in electromagnetism, radiative heat transfer, numerical calculation and programming will be necessary. The student will be trained to the use of the numerical tools already used in the TNR team.

The thesis work will focus on the realization of numerical simulations in order to calculate and optimize the radiative properties of the thermal emitter, in particular in terms of emission spectrum. The first objective will be to propose new materials and structures for the emitter allowing efficient conversion of TPV energy with emitter temperatures between 700 and 1000°C. The TNR team has several calculation codes to achieve this objective.
Skills in electromagnetism, radiative heat transfer, numerical calculation and programming will be necessary. The student will be trained to the use of the numerical tools already used in the TNR team.
Once the structure(s) of the emitters have been identified, they will be fabricated (thin layer deposition and surface nanostructuration techniques) and the thesis work will then focus on the characterization of the optical and thermal properties of these emitters. For this, the Pprime Institute has a state-of-the-art visible and IR ellipsometry measurement setup with a cryostat and a heating stage (4 - 800 K). The doctoral student will be trained to the use of this measurement setup.

* Scientific purpose :

The objective of the PhD is to study wavelength-selective radiative emitters in order to optimize the thermoelectric conversion by very low gap thermophotovoltaic cells (from 0.36 to 0.17 eV) and based on InAs/InAsSb superlattices. This involves being able to convert thermal energy (lost or stored heat available in radiative form) originating from medium- level heat sources (< 1000°C) into electricity. It will be necessary to propose a thermal emitter whose emission spectrum is adapted to that of conversion of the infrared photovoltaic cell. A large part of the work will relate to the realization of numerical simulations of the radiative properties of metamaterials (stacks of thin layers, surface grating, …) then, after manufacture of these selective radiative emitters, to characterize them optically and thermally (ellipsometry and infrared spectroscopy).

* Scientific context :

To meet the challenges posed by climate change in relation to supplying humanity with usable (e.g. electrical) and carbon-free energy, substantial progress must be made in converting heat directly into electricity. A first reason is that most primary energy conversion processes are inefficient: what is not used is transformed into (so-called) waste heat [Liv-21, ADE]. A second reason comes from the idea of storing energy, directly from the sun - or even the surplus from the electrical network - in high-temperature heat [Dat-16, Amy-19]. Thus, this energy is available and usable at any time, especially when solar and wind energy are inoperative, which in fact solves the problems of intermittency.
In both cases, an essential element of such devices is the conversion of thermal energy into electrical energy. Among the existing options, direct conversion by photovoltaic (PV) effect is a way in full revival [Dat-20, Cha-20]. The cells performing this conversion are called thermophotovoltaic (TPV), in order to avoid any confusion with solar photovoltaic, even if the operating principles are identical.
To date, the best conversion efficiency of a thermophotovoltaic cell, obtained very recently (publication in the journal Nature in December 2020 [Fan-20]), is 32%. This is a remarkable result, considering that the best comparable solar cells, i.e. single-junction cells tested in the laboratory, have a efficiency of 30% [NREL]. With multiple junctions, currently under development, the thresholds of 40 to 50% could be exceeded very soon [Sch-20].
The preferred ways to develop these high-efficiency TPV cells concern configurations where the thermal energy source (called emitter) operates at very high temperatures (> 1200°C, up to about 2100°C). But major problems appear, in particular the stability of these emitters, and the thermal losses to an environment at room temperature (a few tens of °C). Therefore, it should be possible to use emitters with a lower operating temperature (from 700 to 1000°C). It is also necessary that the TPV cells can convert radiation in a range of longer wavelengths in the infrared. In other words, it is necessary to develop new photovoltaic cells with very low gap (gap energy), with materials which are usually used for infrared photodetectors, and which often must be cooled to cryogenic temperature (~ 80 to 150 K).

In this context, the thesis is part of a project (LOW-GAP-TPV) funded by the French National Research Agency aiming at proposing, fabricating and evaluating new materials and structures allowing the thermophotovoltaic conversion to very low gap (0.36 to 0.17 eV) of thermal energy from medium level heat sources (< 1000°C).

This research work will be carried out within the TNR team (Heat Transfer at Nanoscales and Radiation) in collaboration with the PPNa team (Physics and Properties of Nanostructures) of the Pprime Institute. The TNR team has extensive expertise in the design of micro and nanostructured materials with spectrally selective properties, such as emitters for TPV devices (ANR SOURCES-TPV project, 2010-2013 [SOU-13]), and passive radiative coolers (ANR JCJC RADCOOL project 2017-2021 [RAD-21]). The group also has a solid reputation in the modeling of coupled heat transfer in systems with micro-nano sized elements, and is equipped with a state-of-the-art visible and IR ellipsometry setup with a cryostat and heating stage (4 - 800 K), required for the project.

*Références :
[ADE] Canal & Gerbaud, rapport de l'ATEE et de l'ADEME, in French, 2016. La chaleur fatale, ADEME report, in french, 2017.
[Amy-19] Amy et al., Energy & environmental Science, 2019.
[Cha-20] Chapuis et al., Photoniques, 2020.
[Dat-16] Datas et al., Energy, 2016.
[Dat-20] Datas & Vaillon, Thermophotovoltaic energy conversion, book chapter, Elsevier, 2020.
[Fan-20] Fan et al., Nature, 2020.
[NREL] Best Research-Cell Efficiency Chart, NREL.
[RAD-21] ANR Project RADCOOL 2017-2021.
[Sch-20] Schulte et al., Applied Phys., 2020.
[SOU-13] ANR Project SOURCES-TPV.

Work Context

The PhD student will be based at the Pprime Institute at the University of Poitiers.

Constraints and risks

Short-term travel in France and abroad is to be expected.

Additional Information

The candidate must have a Master 2 degree.
Skills in electromagnetism, radiative heat transfer, numerical calculation and programming will be necessary. The student will be trained to the use of the numerical tools already used in the TNR team.
Knowledge in optics and physics of materials will be highly appreciated.

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The doctoral student will be registered to the doctoral school SIMME at the University of Poitiers.

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