Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

Modelling, Characterization and optimizations of electronic transport at the passivating contact PV cells interfaces

Département des Technologies Solaires (LITEN)

Laboratoire HETerojonction

01-10-2020

SL-DRT-20-1015

wilfried.favre@cea.fr

Solar energy for energy transition (.pdf)

Resistive losses reduction and engineering in PV cells are becoming a major topic for further efficiency increase. The main actors are focused to identify and quantify the different sources of losses at the various interfaces of the passivating contact PV devices. For this purpose there is a need to consider both test structures representative of the final PV cell (similar process) and operando conditions (light and temperature close to outdoor environment), while present methodologies are far away from these requirements (different fabrication process and dark conditions). The work will be divided into two main parts: (i) Participate to the development and validation of a new setup dedicated to characterization of PV cells contact resistance in operando conditions and (ii) evaluate physical models for the interfacial electronic transport using 2D/3D simulation tools together with advanced characterization techniques (EBIC, EPR). The samples will be produced in the CEA PV cells pilot lines at INES campus (24.63% record efficiency demonstrated) and the knowledge produced will allow further single junction and tandem device optmizations.

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Interaction mechanisms of hydrogen with defects of silicon bulk and at the interfaces of passivated contacts in PV cells

Département des Technologies Solaires (LITEN)

Laboratoire HoMoJonction

01-10-2020

SL-DRT-20-1018

raphael.cabal@cea.fr

Solar energy for energy transition (.pdf)

Although fluctuating, the photovoltaic market is still dominated by silicon technologies occupying ~94%. The most promising homo-junction cell architectures systematically integrate a so-called "passivated" contact through a stack of polycrystalline silicon on tunnel oxide. The hydrogenation of such structures makes it possible to achieve very efficient yields >25%. However, the introduction of hydrogen can also lead to layer delamination or resistive losses through accumulation effects at the interfaces, significantly degrading the efficiency of the final device. To avoid its effects and develop this type of structure with associated yields, it is essential to understand the interactions of hydrogen involved and to understand its role in passivation phenomena. However, hydrogen is an extremely difficult element to characterize by its very nature. Its characterization therefore represents a real challenge, to which are added the difficulties related to the textured surface state of solar silicon and the configuration of poly-Si/Si/SiOx/Si interfaces. To meet this challenge, the work proposed here will be to implement and correlate characterization techniques, allowing both to locate and quantify hydrogen in the volume of silicon and at the interfaces of passivated contact structures. The implementation of a characterization methodology will lead to the main objective of the thesis, which is to propose mechanisms of hydrogen interaction with defects and its role in the quality of passivated contacts. This will open up opportunities for the development and optimization of passivated contact structures. This study will benefit from the infrastructure for the realization of samples from CEA-LITEN in INES and the means of characterization of the nano-characterization platform with its expert environment.

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Iterative Computed Tomography reconstruction from prior information for additive mafufactured components

Département Imagerie Simulation pour le Contrôle (LIST)

Laboratoire Méthodes CND

01-10-2018

SL-DRT-20-1025

caroline.vienne@cea.fr

Additive manufacturing, new routes for saving materials (.pdf)

Among the various non-destructive testing (NDT) methods, X-ray computed tomography (CT) is a powerful tool to characterize and localize inner flaws and to verify the geometric conformity of an object. For this reason, micro CT has been established as the most promising way of control for Additive Manufactured specimens in view of its unique capability for the inspection of complex internal structures and geometries without destroying the part. In classical industrial CT systems, X-ray projections are obtained through the rotation of the object, which is put on a turntable placed between the X-ray source and the image detector. However, to increase the flexibility in the acquisition trajectory and therefore a valued adaptability to object and environment constraints, robotized CT inspection is one of the acknowledged new trends in X-ray NDT. In this context, CEA List is developing an advanced X-ray inspection platform, which consists in moving the X-ray source and the detector around a fixed object, thanks to two synchronized robotic arms. In order to perform CT inspection with such equipment, it is essential to develop new reconstruction algorithms and the objective of the thesis consists in optimizing the acquisition trajectory and an existing iterative algorithm by injecting prior information from the additive manufactured object (its material and 3D model).

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Innovative Mixed RF and low power devices integration in view of advanced fdsoi SOC

Département Composants Silicium (LETI)

Laboratoire d'Intégration des Composants pour la Logique

01-10-2020

SL-DRT-20-1027

claire.fenouillet-beranger@cea.fr

Emerging materials and processes for nanotechnologies and microelectronics (.pdf)

Connected mobile devices are becoming a strategic imperative in order to remain attractive, improve efficiency and competitive for advanced electronic applications. The wireless revolution where Laptops, Smartphone's, tablets, TVs, vehicles and enterprises are connected in a cloud style environment makes possible communication anywhere at any time. Recent developments in wireless communications with the emergence of advanced radio-frequency standard such as LTE, LTE-A and 5 G have brought numerous challenges. The most critical challenge is to provide higher levels of integration with more power efficiency and cost-effective solutions on the same-chip. In parallel to the development of nanometer CMOS as well as beyond-CMOS device technologies for switching, memory and analog functions, the increasing need to integrate various (heterogeneous) technologies (e.g. RF communication, power control, passive components, sensors, actuators) helps to migrate from the system board-level into the system-in- package (SiP) or to the system-on- chip (SoC). In fact, mobile System-on-Chip (SoC) with heterogeneous integration of multiple technologies has truly revolutionized the semiconductor industry. Thanks to the trap-rich Silicon-on-Insulator (SOI) substrate invented at UCL and developed in collaboration with SOITEC, RF SOI presents outstanding RF performance. In addition, the presence of the buried oxide layer not only reduces the junction capacitance but also offers the opportunity of using high resistivity substrate to reduce substrate related RF losses and coupling. However in case of SoC integration the trap-rich is not suitable all across the wafer and localized solutions should be envisaged. Fabrication on a 28FDSOI 300mm platform of specific RF stuctures Characterization of the substrate impact (HR, trap rich, etc ?) on the RF figure of merit Imagine and integrate new technological process schemes to implement localized ?trap-rich like' area before or after FDSOI device realization. Integrate some technological modules on new designed structures and electrical caracterization

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Design, fabrication and characterization of subwavelength nanostructured Si photonics devices enabled by advanced immersion lithography

Département d'Optronique (LETI)

Laboratoire d'Intégration Photonique sur Silicium

01-10-2020

SL-DRT-20-1042

cecilia.dupre@cea.fr

Photonics, Imaging and displays (.pdf)

The demand for telecommunications capacity has increased rapidly in recent years. To satisfy this demand, optical transceivers, previously used only for long distance data transfer, are now used for the shorter distances found in datacenters. Photonic integrated circuits based on silicon are particularly relevant for this application as they use establish CMOS technology to achieve high performance and yield at a low cost. Previous work has shown that integrated components based on sub-wavelength structures allow the possibility of new optical functionalities and improved performance, such as reduced insertion losses and significantly increased spectral bandwidth. The CEA-LETI has its own Si photonics platform including an immersion lithography tool that allows reproducible and precise patterning with dimensions as low as 50nm. The objective of this PhD are to design new high spectral bandwidth/low-loss photonic components using sub-wavelength structures, to develop the fabrication technology for this type of component on the CEA-LETI Si photonics platform and to characterise their optical properties. This PhD, based at CEA-LETI (Grenoble), will be in close collaboration with the C2N-CNRS (Paris-Saclay).

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Improvement and understanding of the performance of silicon cell-based solar generators in harsh environments

Département des Technologies Solaires (LITEN)

Laboratoire Photovoltaïque à Concentration

01-09-2020

SL-DRT-20-1061

philippe.voarino@cea.fr

Solar energy for energy transition (.pdf)

The thesis will be carried out at the interface of several laboratories of the Department of Solar Technologies (DTS) of the CEA located in Le Bourget du Lac on the campus of the National Institute for Solar Energy (INES). The objective of this thesis is to improve the resistance to environmental conditions (radiation, e/H+, UV, thermal cycling) of space solar generators based on silicon solar cells, and to better understand the degradation mechanisms of cells/materials associated. By finely controlling the manufacturing of cells (doping, impurity, architecture, etc.) and modules (materials, thickness, architecture, optical trapping, etc.), it is possible to improve the performance of silicon modules at the end of their lifetime while maintaining a competitive price (?/W), 1 to 3 orders of magnitude lower than space III-V modules.

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