Post-doc on 2D numerical simulation of perovskites/silicon heterojunction tandem solar cells

CEA-INES is looking for a post-doc to work on 2D simulation of perovskites/silicon heterojunction tandem solar cells. The candidate will have the responsibility to develop a model of the PK/SHJ tandem cell on the TCAD simulation package Silvaco. A realistic description of the materials will be implemented, based on in-house characterization of actual layers used (potentially performed during the post-doc), or based on literature. Then the focus will be set on the adjustment of the interface between the two sub-cells (so-called recombination junction, or tunnel junction). This model will afterwards be used to improve our understanding of the tandem cell working principle. In particular, inhomogeneity in layer properties, defects and there influence on cell efficiency will be investigated and brought face to face with experimental results. Finally, strategies to mitigate the influence of these defects will be defined to help the development teams to increase the device efficiency on large areas. For this post-doc position, the candidate needs solid background in semi-conductor physics, as well as previous record in working with simulation tools. He/She will need strong organization skills, and be willing to conduct theoretical work. The results will be published in peer-reviewed journals, as well as in conferences.

Modeling of potential induced degradation in medium voltage PV modules

Medium-voltage (MV) PV power plant technology is part of the PV EVERYWHERE strategy. This strategy makes it possible to reduce power plant costs by reducing the number of cables and their cross-sections, and by making the infrastructure easier to operate. To make these savings possible, resistant MV modules up to 9 kV are needed.
The objectives of this project are: (i) to develop a physical model to account for the degradation of PV modules as a function of voltage levels during operation, (ii) to define test protocols for PV module materials to provide input data for the models, (iii) to manufacture a PV module resistant to PID degradation.
The project will start with the development of test protocols to feed the ion transport models that will enable us to describe the expected degradation modes as a function of module composition. The simulation results will be used to test possible solutions and identify suitable materials, leading to the manufacture of a module resistant to MV up to 9 kV.

Next generation PV module packaging design and mechanical testing

Photovoltaic modules are required to last 25- 30 years in harsh outdoor environment. The packaging of PV modules plays an essential role in reaching this target. PV cells are protected by a glass frontsheet, and highly engineered polymeric encapsulants and backsheets. Encapsulants provide moisture, oxygen &UV barrier, electrical isolation and mechanical protection of highly fragile cells while they must ensure optical coupling between the various layers. Current industrial process technology for module manufacturing is lamination that adds additional constraints to the formulation of encapsulants. These numerous requirements lead to ever-involving complex encapsulant composition and behavior.
The aim of this post-doc is to establish the correlation between the material properties of engineered plastics– their processing conditions and thermo-mechanical behavior in high performance PV modules with heterojunction, back-contact or Si/Perovksite tandem cells. Material selection and lamination process development will be guided by detailed material characterization (DSC, DMA, Peel strength, TGA, WVTR, Soxhlet extraction etc.). Moreover, we aim to establish insights in the encapsulant processing conditions and its impact on mechanical stability of PV modules. The selection of the encapsulants to investigate will be strongly guided by eco-design to lower the environmental impact and to increase the recyclability of modules. This postdoc is conducted in the frame of an EU collaboration.

Development of irradiation resistant silicon materials and integration in photovoltaïcs cells for space applications

Historically, photovoltaic (PV) energy was developed together with the rise of space exploration. In the 90’s, multijunction solar cells based on III-V materials progressively replaced silicon (Si) cells, taking advantage of higher efficiency levels and electrons/protons irradiation resistance. Nowadays, the space environment is again looking at Si based PV applications: request of higher PV power, moderated space mission lengths, cost reduction issues (€/W Si ~ III-V/500), higher efficiencies p-type Si PV cells… Solar cells are exposed to cosmic irradiation in space, especially to electrons and protons fluxes. The latter’s affect the cells performances, essentially because of bulk defect formations and charge carrier recombination. In order to use Si based solar cells in space, we need to increase their irradiation resistance, which is the main goal of this post-doc position. To do so, the work will first consist in elaborating new Si materials, with increased irradiation resistance. Compositional aspects of the Si will be modified, particularly by introducing elements limiting the formation of bulk defects under irradiations, developing electrical passivation properties. The electronic properties of the materials will be deeply characterized before and after controlled irradiation. Then, this Si material will be used to fabricate heterojunction solar cells. Their performances will be evaluated again before and after irradiation. Such experimental work could be supported by numerical simulation at the device scale.

High efficiency silicon cell irradiations for space

Historically, photovoltaics was developed in conjunction with the growth of space exploration. During the 90's, III-V multi-junction solar cells were progressively replaced silicon, for their superior performance & radiation hardness. Today, the context is favorable to a revival of space Si: increasing PV power needs, missions with moderate durations & constraints (LEO), very low cost & high performance terrestrial Si cells (p-type > 26% AM1.5g). However, for Si cells, conventional irradiation ageing methods & sequences (ECSS) are less appropriate. As the literature mainly comes from 80s - 90s, it is necessary to revisit the topic for the latest generation of passivated contacts Si cells (developed at CEA INES) and the unique double beam irradiation facilities of JANNuS platform - CEA Saclay.
This work is part of the SiNRJs project, at the interface between two CEA departments, dealing with space photovoltaics & materials irradiation. The scientific & technological approach adopted: 1. fabrication of passivated contact Si cells (HeT and/or Poly-Si) 2. Si cells optoelectronic characterizations before irradiation (IV AM1.5/AM0, EQE, etc.) 3. Cells & samples proton irradiations, in situ characterizations (Raman & El) 4. Ex situ characterizations after irradiations (IV AM1.5/AM0, EQE, etc) 5. Results analysis and synthesis. From a scientific point of view, the key issues to be addressed concern the understanding of the mechanisms/dynamics of defect creation/healing under this double electronic and ballistic excitation.

Decentralized Solar Charging System for Sustainable Mobility in rural Africa

A novel stand-alone solar charging station (SASCS) will be deployed of in Ethiopia. Seeing as 45% of Sub-Saharian Africa’s population lacks direct access to electricity grids and seeing as the the infrastructure necessary to reliably harness other energy sources is largely non-existent for many such populations in Ethiopia, introducing the SASCS among some of the country’s rural communities is a necessary effort. It could ostensibly invigorate communities’ agricultural sector and support those whose employment is rooted in farming. A SASCS could also serve to integrate renewable energy within the country’s existing electricity mix. CEA INES will act as a consulting Partner for the design and implementation of the solution (second life batteries, solar will be investigated). In addition, because of CEA INES’s established expertise in the installation of solar tools within various communities, the initiative will also provide know-how for the installation of the SolChargE in Ethiopia as well as cooperate on workshops for students and technicians employed by the project.