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.

In this paper, we report the evolution of silicon heterojunction solar cell properties focusing, in particular, on the indium tin oxide (ITO) layers upon consecutive thermal annealing. We find that the charge carrier density

N_{\rm e}

of the ITO increase ...

Wafers for the PV industry are mainly sawn with a multi-wire slurry saw. This process is slow (it takes almost half a day to complete a cut) and generates a lot of waste: around half the silicon is sawn away and contaminating the slurry, and the wire is wo ...

Nanometer wide silicon filaments embedded in an amorphous silicon oxide matrix are grown at low temperatures over a large area. The optical and electrical properties of these mixed-phase nanomaterials can be tuned independently, allowing for advanced light management in high efficiency thin-film silicon solar cells and for band-gap tuning via quantum confinement in third-generation photovoltaics.

Surface textures in thin-film silicon multi-junction solar cells play an important role in gaining the photocurrent of the devices. In this paper, a design of the textures is carried out for the case of amorphous silicon/micro-crystalline silicon (a-Si:H/m ...

Among the main challenges of our century, the climate change and the need of diversification of the energy sources are of most importance. Renewable energies undoubtedly have an important role to play, photovoltaic (PV) electricity being especially well suited to face these energy challenges. However, the current integration of PV panels often comes without architectural consideration. In this context, the Archinsolar project [1] aims to develop a new generation of photovoltaic elements based on silicon thi

We report on the development of fully flexible microcrystalline and micromorph tandem solar cells directly on low-cost substrates like poly-ethylen-terephtalate (PET) and poly-ethylen-naphtalate (PEN). The cells are deposited in nip or nip/nip configuratio ...

Silicon heterojunction (SHJ) solar cells feature amorphous silicon passivation films, which enable very high voltages. We report how such passivation increases with operating temperature for amorphous silicon stacks involving doped layers and decreases for ...

This contribution presents the status of amorphous and microcrystalline silicon solar cells on glass, and discusses some material/fabrication factors that presently limit their conversion efficiency. Particular attention is focused on recent results and de ...

Thin, light-absorbing films attenuate the Raman signal of underlying substrates. In this article, we exploit this phenomenon to develop a contactless thickness profiling method for thin films deposited on rough substrates. We demonstrate this technique by ...

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding combined with layer transfer enables the replication of arbitrary surface patterns from a master structure onto the functional material. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes. In particular we demonstrate the fabrication of patterned transparent zinc oxide electrode

The introduction of a nc-SiOx:H material as window layer in single junction a-Si:H n-i-p solar cell leads to a Voc enhancement of 80 mV compared to a μc-Si:H p-layer. According to numerical modeling of the Voc, both the higher work function p-layer and the conduction band offset (CBO) at the i/p interface match well with the experimental Voc increase with the oxygen content. Using the differential temperature method, the builtin voltage (Vbi) of the cells with the two different p-layers is measured to be si

RE-BD AR2024, the 2024 Assessment Report on Renewable Energy and Biodiversity, addresses the critical balance between expanding renewable energy (RE) and better protecting biodiversity in Switzerland, with a special focus on the Alpine regions. It is the result of the project “Towards new renewable energy developments in Switzerland that preserve biodiversity”, supported by CLIMACT, the Center for Climate Impact and Action of UNIL & EPFL, conducted between June 2023 and September 2024. The project reviewed

High conversion efficiency for (amorphous/microcrystalline) "micromorph" tandem solar cells requires both a dedicated light management, to keep the absorber layers as thin as possible, and optimized growth conditions of the microcrystalline silicon (μc-Si:H) material. Efficient light trapping is achieved here by use of textured front and back contacts as well as by implementing an intermediate reflecting layer (IRL) between the individual cells of the tandem. This paper discusses the latest developments of

We recently showed that silicon heterojunction solar cell with MoOx-based hole-selective contact could reach 23.5% in efficiency with MoOx layers of 4 nm. Such thin MoOx layer enables a considerable current-density gain of over 1 mA/cm(2) compared to the u ...

We fabricated amorphous silicon n-i-p solar cells with two types of nanopatterned back reflectors using stencil lithography. One reflector type has a plasmonic grating that is embedded in the ZnO layer; the other one has a metallic grating patterned on top ...

Passivating contacts are indispensable for achieving high conversion efficiency in crystalline-silicon solar cells. Their realization and integration into a convenient process flow have become crucial research objectives. Here, we report an alternative pas ...

Nanoindentation and nanoscratching of an indium phosphide (InP) semiconductor surface was investigated via contact mechanics. Plastic deformation in InP is known to be caused by the nucleation, propagation, and multiplication of dislocations. Using selective electrochemical dissolution, which reveals dislocations at the semiconductor surface, the load needed to create the first dislocations in indentation and scratching can be determined. The experimental results showed that the load threshold to generate t

The performance of a tandem solar cell depends on the performance of its constituting subcells. Although this dependency is theoretically straightforward for open-circuit voltage (V-oc) and short-circuit current, it is indirect for fill factor (FF) and thu ...

By controlling the deposition parameters of low pressure chemical vapor deposition (LPCVD) grown ZnO transparent conductive oxide (TCO), we show that it is possible to achieve a switch of crystallographic orientations and to obtain novel surface nanotexture. The new layers are (0 0 0 2) oriented and exhibit light scattering at larger angles than state-of-the-art TCO used in thin film silicon solar cells. This property translates into a strong enhancement of the top amorphous cell current in micromorph tande

This contribution reviews some of the latest achievements and challenges in thin-film silicon photovoltaic (PV) technology based on amorphous and nanocrystalline silicon and their alloys. We address material and device developments, including (i) improved plasma deposition processes to achieve high-quality dense absorber materials; (ii) absorber layers based on silicon tetrafluoride, which lead to enhanced absorption in the near-infrared and yield outstanding short-circuit current densities; (iii) dedicated

Christophe Ballif

Chat with Graph Search

Annealing of Silicon Heterojunction Solar Cells: Interplay of Solar Cell and Indium Tin Oxide Properties

Diamond wire-sawn silicon wafers - from the lab to the cell production

Silicon Filaments in Silicon Oxide for Next-Generation Photovoltaics

Design of periodic nano- and macro-scale textures for high-performance thin-film multi-junction solar cells

Innovative Solution for Building Integrated Photovoltaics

Development of micromorph tandem soalr cells on flexible low cost plastic substrates

Amorphous/Crystalline Silicon Interface Passivation: Ambient-Temperature Dependence and Implications for Solar Cell Performance

Limiting factors in the fabrication of microcrystalline silicon solar cells and microcrystalline/amorphous (‘micromorph’) tandems

Profilometry of thin films on rough substrates by Raman spectroscopy

Nanomoulding of functional materials, a versatile complementary pattern replication method to nanoimprinting

Origin of the Voc enhancement with a p-doped nc-SiOx:H window layer in n-i-p solar cells

RE-BD AR2024 Report - main findings

Realization of high efficiency micromorph tandem silicon solar cells on glass and plastic substrates: Issues and potential

Performance Limitations and Analysis of Silicon Heterojunction Solar Cells Using Ultra-Thin MoOx Hole-Selective Contacts

Stencil-Nanopatterned Back Reflectors for Thin-Film Amorphous Silicon n-i-p Solar Cells

A passivating contact for silicon solar cells formed during a single firing thermal annealing

Analysis of onset of dislocation nucleation during nanoindentation and nanoscratching of InP

Influence of the Subcell Properties on the Fill Factor of Two-Terminal Perovskite-Silicon Tandem Solar Cells

Control of LPCVD ZnO growth modes for improved light trapping in thin film silicon solar cells

Recent advances and remaining challenges in thin-film silicon photovoltaic technology