Publications by Christophe Ballif

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The complex refractive index (dielectric function) of planar CH3NH3PbI3 thin films at room temperature is investigated by variable angle spectroscopic ellipsometry and spectrophotometry. Knowledge of the complex refractive index is essential for designing ...

To study recombination at the amorphous/crystalline Si (a- Si:H/c-Si) heterointerface, the amphoteric nature of silicon (Si) dangling bonds is taken into account. Modeling interface recombination measured on various test structures provides insight into th ...

Recently, it has been shown that it is possible to tune the morphology of zinc oxide films deposited by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) while preserving good electrical conductivity. Here a closer look is taken at films depos ...

Increasing the conductivity of polycrystalline zinc oxide films without impacting the transparency is a key aspect in the race to find affordable and high quality material as replacement of indium-containing oxides. Usually, ZnO film conductivity is provid ...

Mini-module aging tests with differently interconnected heterojunction solar cells having industrially viable copper metallization are presented. The plating process comprises 3 steps: firstly, screen printing of a seed-grid layout using a copper-based paste, followed by deposition of a dielectric layer over the entire wafer surface, and finally, selective copper electrodeposition on grid positions. Modules with Smartwire interconnection, fabricated with M6 half-cells, are stable in extended TC and PID test

The current losses due to parasitic absorption in the indium tin oxide (ITO) and amorphous silicon (a-Si:H) layers at the front of silicon heterojunction solar cells are isolated and quantified. Quantum efficiency spectra of cells in which select layers are omitted reveal that the collection efficiency of carriers generated in the ITO and doped a-Si:H layers is zero, and only 30% of light absorbed in the intrinsic a-Si:H layer contributes to the shortcircuit current. Using the optical constants of each laye

The use of passivating contacts compatible with typical homojunction thermal processes is one of the most promising approaches to realizing high-efficiency silicon solar cells. In this work, we investigate an alternative rear-passivating contact targeting ...

A tracking-integrated hybrid micro-concentrator module is presented that can harvest direct, diffuse, and albedo irradiance components. It uses biconvex 180x lens arrays to concentrate direct light on high-efficiency III-V solar cells (29% module efficienc ...

Crystalline silicon (c-Si) photovoltaics has long been considered energy intensive and costly. Over the past decades, spectacular improvements along the manufacturing chain have made c-Si a low-cost source of electricity that can no longer be ignored. Over ...

In densely populated or mountainous countries where installation of large‐scale solar plants is challenging, photovoltaic (PV) modules in building applications offer a solution by transforming passive surfaces into energy‐generating systems. The need for f ...

The growing integration of photovoltaic (PV) systems into complex environments—such as rooftops, façades, and vehicles—has introduced new shading patterns and the need for accurate performance modeling under these partial shading conditions. In particular, building-integrated photovoltaics (BIPV) are often subject to thin shadows from nearby building components, vegetation, or infrastructure. These shadings can impact only portions of individual cells, leading to inhomogeneous irradiances that are difficult

Glass-free, lightweight, photovoltaic modules have the potential to enable new uses of solar in building integrated and vehicle integrated applications. Glass-free modules have the advantages of reduced weight, lower-cost mounting solutions, and reduced tr ...

Numerous studies have been conducted to evaluate the potential of photovoltaic systems in Switzerland, considering roofs, facades, infrastructure, or free land installations. These studies differ by the datasets used, their methods, the assumptions on the system performance, and the installation details, but more importantly, by the various reduction factors introduced to obtain a realistic estimate of the photovoltaic potential. The present study reviews the critical elements of these studies, especially f

Accurate clear-sky detection (CSD) is essential for reliable data analysis and performance assessments in photovoltaic (PV) systems. However, many advanced machine learning (ML) models function as “black boxes”, limiting their interpretability and trustworthiness. This study presents an interpretable Artificial Intelligence (AI) framework that combines high predictive performance with deep insight into model decision-making. Using a hand-labelled dataset from a fixed-tilt PV system in Golden, Colorado, USA,

Ultra-high dose rate radiation therapy (FLASH) based on proton irradiation is of major interest for cancer treatments but creates new challenges for dose monitoring. Amorphous hydrogenated silicon is known to be one of the most radiation-hard semiconductor ...

Microcrystalline hydrogenated silicon growth with VHF-PECVD was examined in an industrial type parallel plate KAITM reactor. The influence of pressure on material quality was studied in single junction solar cells. Solar cells with their intrinsic layer pr ...

The challenge for all photovoltaic technologies is to maximize light absorption, to convert photons with minimal losses into electric charges, and to efficiently extract them to the electrical circuit. For thin-film solar cells, all these tasks rely heavily on the transparent front electrode. Here we present a multiscale electrode architecture that allows us to achieve efficiencies as high as 14.1% with a thin-film silicon tandem solar cell employing only 3 μm of silicon. Our approach combines the versatili

Bandgap tuning in iodide perovskites for silicon–perovskite tandem applications is commonly achieved through either A-site cation alloying or halide mixing. While halide alloying enables wide bandgap tunability, it suffers from phase segregation and long-term instability. A-site alloying offers a more stable alternative that avoids halide segregation; however, conventional antisolvent-based fabrication methods face severe miscibility constraints, particularly at high cesium concentrations. Although CsPbI₃ p

This work presents a study of p-type passivating contacts based on SiCx formed via a rapid thermal processing (RTP) step, using conditions compatible with the firing used to sinter screen-printed metallization pastes in industry. The contributions of the t ...

As the thin film silicon solar cell technology reaches a pivotal point to keep competing in the photovoltaic industry where crystalline silicon and other technologies currently dominate, it has become an urgent task to revolutionize some of its state-of-th ...

Christophe Ballif

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Complex Refractive Index Spectra of CH3NH3PbI3 Perovskite Thin Films Determined by Spectroscopic Ellipsometry and Spectrophotometry

Properties of interfaces in amorphous/crystalline silicon heterojunctions

c-texture versus a-texture low pressure metalorganic chemical vapor deposition ZnO films: Lower resistivity despite smaller grain size

Relaxing the Conductivity/Transparency Trade-Off in MOCVD ZnO Thin Films by Hydrogen Plasma

Aging tests of mini-modules with copper-plated heterojunction solar cells and pattern-transfer-printing of copper paste

Current Losses at the Front of Silicon Heterojunction Solar Cells

Silicon-Rich Silicon Carbide Hole-Selective Rear Contacts for Crystalline-Silicon-Based Solar Cells

Industrialization of hybrid Si/III-V and translucent planar micro-tracking modules

Status and perspectives of crystalline silicon photovoltaics in research and industry

Characterization of Lightweight Polymeric Honeycomb Structures for Use as Backsides in Glass‐Free PV Modules

Modeling partial shading at the cell level on photovoltaic modules

ETFE and its Role in the Fabrication of Lightweight c-Si Solar Modules

Meta-study of potential for photovoltaic installations in Switzerland

An interpretable AI framework for clear-sky detection in photovoltaics monitoring

Amorphous silicon detectors for proton beam monitoring in FLASH radiotherapy

Influence of ion bombardment on microcrystalline silicon material quality and solar cell performances

Multiscale transparent electrode architecture for efficient light management and carrier collection in solar cells

High-Throughput Screening of Cs-Rich Pure-Iodide Perovskites

Understanding and mitigating resistive losses in fired passivating contacts: role of the interfaces and optimization of the thermal budget

A scalable and inexpensive surface-texturization method for advanced transparent front electrodes in microcrystalline and micromorph thin film silicon solar cells