Publications by Christophe Ballif

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

Poly (ethylene-co-vinyl acetate) (EVA) is the major polymer used for photovoltaic (PV) modules encapsulation. Its degree of cross-linking (related to its gel content) is taken as a major quality reference. Differential Scanning Calorimetry (DSC) has been proven to be fast and effective but is to determine the gel content, however, destructive for the PV module. With the aim to develop a non-destructive quality assessment tool, a detailed discussion on the DSC thermogram of EVA PV encapsulant is presented he

We present a study of the optical mode structure in metal-dielectric multilayer structures that represent amorphous silicon thin film solar cells with metallic back contact. Knowledge of the modal structure represents a first step toward describing absorpt ...

While perovskite-based photovoltaics (PV) is progressing toward commercialization, it remains an open question which fabrication technology - solution-based, vapor-based, or combinations - will pave the way to faster economic breakthrough. The vast majority of research studies make use of solution-processed perovskite thin films, which benefit from a rapid optimization feedback and inexpensive to procure tools in modern research laboratories, but vapor phase deposition processes dominate today's established

High-efficiency p-i-n microcrystalline silicon single-junction solar cells are fabricated and their longterm stability is investigated. We focus in particular on the stability of the absorber layer after atmospheric storage in absence of light and compare non-encapsulated devices with different cell design and crystalline volume fractions. Furthermore, an innovative stack of transparent conductive oxide is used as front electrode in order to investigate the effect of small surface roughness on the electrica

We introduce a novel degradation effect of the transparent conductive oxide zinc oxide (ZnO). The effect is observed for ZnO layers deposited on commercially available soda-lime glass. When an electric ﬁeld is applied, the potential induced anodic degradation causes a massive sheet resistance increase of the ZnO. We show that the increase in resistance strongly affects the power output of a small non-encapsulated thin-ﬁlm photovoltaic module, in which ZnO was used as the front electrode. For the module, an

Thanks to their unique morphology, nanowires have enabled integration of materials in a way that was not possible before with thin film technology. In turn, this opens new avenues for applications in the areas of energy harvesting, electronics, and optoele ...

Several thin-film solar cell technologies require light-trapping schemes that are predominantly based on depositing the solar cells on rough surfaces. While this approach efficiently increases the density of photo-generated carriers, open-circuit voltage and fill factor generally decrease. Substrates that decouple the growth interface from the light-scattering interface were previously proposed as a solution to this dilemma, and proof-of-concepts were demonstrated in thin film-silicon solar cells. In this c

High efficiency Si heterojunction (HJ) solar cells must exhibit low interface recombination, as it limits the cell open circuit voltage (VOC). The study of the interface recombination of various a-Si:H/c-Si lifetime test samples gives insight into the reco ...

Thin-film-on-ASIC (TFA) detectors are monolithic pixel devices that consist of amorphous silicon detecting diodes directly deposited on readout electronics. This paper presents a characterization of the TFA spatial resolution using the electron-beam-induced current (EBIC) technique, in which pixel pads patterned in microstrips were swept by the beam. We measured the spatial resolution for different configurations and thicknesses of the TFA active layer with different beam energies, currents and sweep speeds

Crystalline silicon wafer (c-Si) can be extremely well passivated by plasma enhanced chemical vapor deposited (PECVD) amorphous silicon (a-Si:H) films. As a result, on flat substrates, solar cells with very high open circuit voltage are readily obtained. O ...

We introduce a limit for the strength of coupling light into the modes of solar cells. This limit depends on both a cell’s thickness and its modal properties. For a cell with refractive index n and thickness d, we obtain a maximal coupling rate of $2c\sqrt ...

In silicon heterojunction solar cells, the passivation of the crystalline silicon wafer surfaces and fabrication of emitter and back surface field are all performed by intrinsic and doped amorphous silicon thin layers, usually deposited by plasma-enhanced chemical vapor deposition (PECVD). By using in-situ diagnostics during PECVD, it is found that the passivation quality of such layers directly relate to the plasma conditions, especially on the silane depletion fraction. Good interface passivation is indee

State-of-the-art solar cells based on thin film silicon make use of random textures for absorption enhancement; in the past, the development of these textures was carried out empirically, and in most applications this is still the case. Attempts to understand light scattering at the internal interfaces rely on quantities like haze and angle resolved scattering that are only measurable in air and need to be extrapolated, normally by means of scalar scattering theory. In this context it is unfortunate that th

This review focuses on monolithic 2-terminal perovskite-silicon tandem solar cells and discusses key scientific and technological challenges to address in view of an industrial implementation of this technology. The authors start by examining the different ...

Optimized transparent conductive oxide front electrodes are vital to further increase the efficiency of thin-film silicon solar devices. We report details on the fabrication of multiscale textured zinc oxide substrates and their implementation in amorphous silicon/microcrystalline silicon tandem (micromorph) devices. Such substrates allow separate optimization of light trapping in the top and bottom cells, and efficient decoupling of transparency and conduction.We show in particular the need for sharp, nano

We derive scaling laws for the Rayleigh-Sommerfeld formulation we recently developed to describe light scattering from nanotextured interfaces. These scaling laws provide precious intuition on how to link scattering from different interfaces. In particular, we answer the question how to obtain a Lambertian scatterer into silicon, starting from a Lambertian scatterer into air relevant to the development of light trapping schemes in thin-film silicon solar cells. We also define a Lambertionality factor which

In this study we present a boron-doped silicon carbide layers as a hole-selective contact which is compatible with short annealing time (typically < 1 minute) as the one used for firing of metal pastes. The application of such layers on symmetrically proce ...

The n-type TOPCon technology is currently the leading approach in the industry. Generally, it involves two high-temperature steps that can result in long cycle times and expensive processes. In this context, we propose a lean manufacturing process based on ...

A new type of micro-channel plate detector based on hydrogenated amorphous silicon is proposed which overcomes the fabrication and performance issues of glass or bulk silicon ones. This new type of detectors consists in 80-100 μm thick layers of amorphous ...

The sawing parameters have an impact on the depth of the defects in the wafers, and hence on their mechanical strength. However, as sawing is a highly complex system, the wafering industry is still relying on a “trial and error” approach to improve the saw ...

Christophe Ballif

Chat with Graph Search

Towards in-line determination of EVA Gel Content during PV modules Lamination Processes

Influence of the ZnO buffer layer on the guided mode structure in Si/ZnO/Ag multilayers

Vapor phase deposition of perovskite photovoltaics: short track to commercialization?

TOWARDS BETTER UNDERSTANDING OF LONG-TERM STABILITY IN THIN FILM MICROCRYSTALLINE SILICON SOLAR CELLS

Anodic degradation of ZnO on soda-lime glass

Plastic and Elastic Strain Fields in GaAs/Si Core-Shell Nanowires

Thin-film silicon triple-junction solar cell with 12.5% stable efficiency on innovative flat light-scattering substrate

Heterojunction solar cell efficiency improvement on various c-Si substrates by interface recombination modelling

High Spatial Resolution of Thin-Film-on-ASIC Particle Detectors

Modification of textured silicon wafer surface morphology for fabrication of heterojunction solar cell with open circuit voltage over 700mV

Limit of light coupling strength in solar cells

Silane plasma diagnostics for high-efficiency silicon heterojunction solar cells

Light scattering at nano-textured surfaces in thin film silicon solar cells

Monolithic Perovskite-Silicon Tandem Solar Cells: From the Lab to Fab?

Nanometer- and Micrometer-Scale Texturing for High-Efficiency Micromorph Thin-Film Silicon Solar Cells

Light trapping in solar cells: When does a Lambertian scatterer scatter Lambertianly?

A passivating contact concept compatible with a short thermal treatment

Boron-emitter development for TOPCon c-Si solar cells based on plasma-deposited boron diffusion source and poly-Si(n) passivating contact

Micro-Channel Plate Detectors Based on Hydrogenated Amorphous Silicon

Influence of abrasive concentration on the qualiy of wire-sawn silicon wafers