Publications by Christophe Ballif

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Bright-field (BF) and annular dark-field (ADF) electron tomography in the transmission electron microscope (TEM) are used to characterize elongated porous regions or cracks (simply referred to as cracks thereafter) in micro-crystalline silicon (μc-Si:H) solar cell. The limitations of inferring the 3D geometry of a crack from a tilt series of images acquired from 100-nm-thick focused ion beam (FIB) milled TEM specimen are discussed. In an attempt to maximize the specimen tilt range and to reduce the effects

Perovskite/crystalline silicon tandem solar cells have the potential to reach efficiencies beyond those of silicon single-junction record devices. However, the high-temperature process of 500 °C needed for state-of-the-art mesoscopic perovskite cells has, ...

Silicon heterojunction solar cells have high open-circuit voltages thanks to excellent passivation of the wafer surfaces by thin intrinsic amorphous silicon (a-Si:H) layers deposited by plasma-enhanced chemical vapor deposition (PECVD). By using in-situ plasma diagnostics and ex-situ film characterization, we show that the best a-Si:H films for passivation are produced from deposition regimes close to the amorphous-to-crystalline transition. Based upon this finding, layers deposited in a large-area very hig

Amorphous and microcrystalline silicon have been proven to be very interesting for low cost thin film photovoltaic devices. Usually these two materials are deposited using the same large area plasma-enhanced chemical vapor deposition reactors from silane a ...

This work addresses the task of integrating reflectarray antennas on thin-film solar cell panels, as a means to save real estate, weight or cost of platforms, such as satellites or transportable autonomous antenna systems. Reflectarray unit cell families, ...

We investigate the influence of the oxygen content in boron-doped nanocrystalline silicon oxide films (p-nc-SiOx) and introduce this material as window layer in n-i-p solar cells. The dependence of both, optical and electrical properties on the oxygen cont ...

Ultrathin layers of hydrogenated amorphous silicon (a-Si:H), passivating the surface of crystalline silicon (c-Si), are key enablers for high-efficiency silicon heterojunction solar cells. In this work, the authors apply highly sensitive attenuated total r ...

Hydrogenated amorphous silicon (alpha-Si:H) has been used for decades doped and as intrinsic absorber layers in thin-film silicon solar cells. Whereas their effiency was improved for a long time by the deposition of higher quality absorber layers, recent i ...

Lower absorption, lower refractive index and tunable resistance are three advantages of doped silicon oxide containing nanocrystalline silicon grains (nc-SiOx) compared to doped microcrystalline silicon, for the use as p- and n-type layers in thin-film silicon solar cells. In this study we show how optical, electrical and microstructural properties of nc-SiOx layers depend on precursor gas ratios and we propose a growth model to explain the phase separation in such films into Si-rich and O-rich regions as v

In this work, the effects of luminescent coupling (LC) on the external quantum efficiency (EQE) of perovskite‐silicon tandem (PST) solar cells are quantified by means of monochromatic transient photocurrent measurements and comprehensive optoelectronic simulations that take into account both optical and electrical coupling of the subcells. It is shown that, at short wavelengths, a similar response results from both LC and silicon bottom‐cell shunts. The two contributions can be discriminated and quantified

High-efficiency thin-film silicon triple-junction solar cells in p-i-n configuration have been fabricated using amorphous silicon top cell absorber layers, as well as microcrystalline silicon middle and bottom cell absorbers. The triple-junction cells were ...

Recent advancements in glass-free photovoltaic (PV) module designs have paved the way for lightweight, streamlined structures with versatile designs, all while maintaining high performance and reliability. These innovations are finding broader applications in Integrated Photovoltaics (IPV) domains. Within this context, CSEM has developed specialized encapsulants to ensure the high reliability of lightweight modules. This study will initially introduce newly developed polymeric materials designed to serve as

A high-quality encapsulation process is crucial to ensuring the performance and long-term reliability of photovoltaic (PV) modules. In crystalline Si technology-based modules, poly (ethylene-co-vinyl acetate) (EVA) is the most widely used PV encapsulant. I ...

Executive Summary of RE-BD AR2024, DOI: 10.5075/epfl.20.500.14299/241642 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 & E

Replacing silver metallization with earth-abundant materials in Si solar cells is a critical step towards the sustainable growth of photovoltaics. In this work, we investigate fire-through processes using Al for the metallization of solar cells with p-type ...

Unlocking the full potential of passivating contacts, increasingly popular in the silicon solar cell industry, requires determining the minority carrier lifetime. Minor passivation drops limit the functioning of solar cells; however, they are not detected ...

Lower absorption, lower refractive index, and tunable resistance are three advantages of amorphous silicon oxide containing nanocrystalline silicon grains nc-SiOx compared to microcrystalline silicon c-Si, when used as a p-type layer in c-Si thin-film solar cells. We show that p-nc-SiOx with its particular nanostructure increases c-Si cell efficiency by reducing reflection and parasitic absorption losses depending on the roughness of the front electrode. Furthermore, we demonstrate that the p-nc-SiOx reduce

Hydrogenated microcrystalline silicon (μc-Si:H) growth by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) is studied in an industrial-type parallel plate KAI reactor. Combined plasma and material characterization techniques allow ...

The poor intrinsic perovskite absorber stability is arguably a central limitation challenging the prospect of commercialization for photovoltaic (PV) applications. Understanding the nanoscopic structural features that trigger instabilities in perovskite materials is essential to mitigate device degradation. Using nanostructure characterization techniques, we observe the local degradation to be initiated by material loss at stacking faults, forming inherently in the (011)-faceted perovskite domains in differ

Perovskite-silicon tandem solar cells have now surpassed the 30% efficiency mark, which has led to the acceleration of industrialization efforts. With most research focusing on 2-terminal tandems, we focus our investigation on 3-terminal tandem solar cells, a configuration that promises a higher energy yield under realistic operating conditions. We specifically focus on the simulation of the performance of finite strings of 3-terminal tandem cells interconnected in various voltage-matching configurations. T

Christophe Ballif

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Conventional and 360 degree electron tomography of a micro-crystalline silicon solar cell

Zinc tin oxide as high-temperature stable recombination layer for mesoscopic perovskite/silicon monolithic tandem solar cells

21% efficiency silicon heterojunction solar cells produced with very high frequency PECVD

Study of the microstructure transition width from amorphous to microcrystalline silicon as a function of the input silane concentration

Copper and transparent-conductor reflectarray elements on thin-film solar cell Panels

Window layer with p doped silicon oxide for high V-oc thin-film silicon n-i-p solar cells

Amorphous/Crystalline Silicon Interface Stability: Correlation between Infrared Spectroscopy and Electronic Passivation Properties

Review: Progress in solar cells from hydrogenated amorphous silicon

Mixed phase silicon oxide layers for thin-film silicon solar cells

Impact of Luminescent Coupling on Perovskite‐Silicon Tandem External Quantum Efficiency Quantified by Comprehensive Opto‐Electronic Simulation

Thin-Film Silicon Triple-Junction Solar Cells on Highly Transparent Front Electrodes With Stabilized Efficiencies up to 12.8%

Lightweight Solar Modules Implementing Advanced Polymer Materials and Solar Cells

The effect of cooling press on the encapsulation properties of crystalline photovoltaic modules: residual stress and adhesion

RE-BD AR2024 - Executive Summary. Accelerating renewable energy development while enhancing biodiversity protection in Switzerland

Interactions between aluminium and fired passivating contacts during fire-through metallization

Influence of local surface defects on the minority-carrier lifetime of passivating-contact solar cells

Mixed-phase p-type silicon oxide containing silicon nanocrystals and its role in thin-film silicon solar cells

Microcrystalline and micromorph device improvements through combined plasma and material characterization techniques

Suppression of Stacking Faults for Stable Formamidinium-Rich Perovskite Absorbers

Do all good things really come in threes? The true potential of 3-terminal perovskite-silicon tandem solar cell strings