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PhD : selection by topics

Technological challenges >> Solar energy for energy transition
3 proposition(s).

Integration in tandem devices of passivated contacts PV cells : Towards a multifunctional and universal interface technology

Département des Technologies Solaires (LITEN)

Laboratoire HoMoJonction

01-10-2020

SL-DRT-20-0758

thibaut.desrues@cea.fr

Solar energy for energy transition (.pdf)

This project aims to develop cristalline (c-Si) silicon PV cell technolologies with passivated contacts for tandem devices applications. To overcome conventional single junction cells limitations, one interesting research topic is about tandem structures which allow conversion efficiencies above 30%. For these tandem devices, it is necessary to optimise c-Si bottom cells fabrication processes to enhance the complementarity between both devices (Top and Bottom cells). The main goal of the PhD is to obtain universal c-Si Bottom cells adapted for all top cells technologies (Perovskite, CGS, III/V,...). These c-Si bottom cells will rely on the poly-Si/SiOx technology which allow to avoid the use of transparent conductive oxide (TCO)layers and also to obtain a great temperature stability of the devices. This last feature enables high temperature steps for the topcell fabrication processes. This project will consist in: 1/ Develop thin films and stacks optimized for bottom c-Si cells used in tandem architecture 2/ Characterize electrical and optical properties of the developed structures 3/ Integrate these structures into a tandem device using potentially different topcell technologies

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Elaboration and characterization of silicon / perovskite tandem solar cells with PIN architecture

Département des Technologies Solaires (LITEN)

Laboratoire Modules Photovoltaïques Organiques

01-09-2020

SL-DRT-20-0823

muriel.matheron@cea.fr

Solar energy for energy transition (.pdf)

Silicon / perovskite solar cells have recently shown major breakthoughs with record efficiencies reaching 28% for 2 terminal tandems (in which both subcells are connected in series). According to literature, best efficiencies are obtained with PIN architecture, due to optimized light management : minimized parasitic absorption from P layer in top cell, possibility to use transparent microcrystalline silicon as tunnel junction, or nanocrystalline silicon oxide with a better index matching property, leading to less parasitic reflection. Such materials (microcrystalline silicon and nanocrystalline silicon oxide) are developed within the frame of a PhD thesis at CEA-Liten, along with optimization of the perovskite single junction PIN architecture performed at CEA-Liten. The aim of the proposed PhD is to combine such developments into PIN tandems. Efforts will be devoted to in-depth characterization of the tunnel / recombination junctions and of the whole device. The goal is to identify charge transport mechanisms occurring at the interconnection layer between both subcells and to detect device limitations. To do so, electrical characterization of tests structures will be conducted, along with variable illumination measurements and photo/electroluminescence imaging of tandems. After a first analysis of PIN structures, new interconnection systems (obtained by chemical modification of interconnection materials) could be proposed and analyzed the same way.

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New High Efficiency DC / DC Converter Technology with Integrated Galvanic Isolation for Medium Voltage DC grids

Département des Technologies Solaires (LITEN)

Laboratoire Systèmes PV

01-06-2020

SL-DRT-20-0833

Stephane.CATELLANI@cea.fr

Solar energy for energy transition (.pdf)

The primary sources of electrical energy used in renewable energy systems are DC. We can indicate below, the main characteristics in tension of the sources in question: -Photovoltaic (1.5 kVDC) -Systems of energy storage (800 V-1.5 kVDC) -Stacks EHT (950 VDC) -Electric Vehicle Batteries (800 VDC) On the other hand, the new power transmission networks are in direct current: -HVDC: 100 kVDC to 1.6 MVDC Some rail power systems are also DC: -Rain: 1.5kVDC, 3kVDC, experimental network project SNCF 10kVDC Architectures with DC collector are planned in the following applications: -Distribution of energy in charging stations for electric vehicles -Nautical ship propulsion systems -Electrical conversion lines of railway traction units -Photovoltaic power generation Stationary storage of electrical energy The objective of this thesis work will be to obtain a modular DC / DC converter brick compatible with the voltage levels delivered by the ENR sources and allowing to inject on the DC medium voltage. Electrical isolation of primary sources will remain unchanged: therefore, to ensure the isolation of sources, very high efficiency transformer technologies (> 99.5%), integrated in the static conversion stages -Injection can be done on a DC 9kV network (experimental network SNCF) -The power electronics will be made with HT SiC semiconductors whose current performance is much higher than Si equivalents. The DTNM will bring its expertise on magnetic materials for the design of the integrated transformer in the conversion stages.

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