Publications de Christophe Ballif

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Dual-junction solar cells have the potential for higher conversion efficiencies than single junctions, thanks to a better utilization of the solar spectrum. However, their optimization is more complex because the monolithic interconnection makes the individual subcell electrical measurement difficult or impossible. This study presents a new technique to measure the open-circuit voltage VOC of each individual subcell of a dual-junction device with a method that circumvents the need for completely selective i

Tandem photovoltaic devices based on perovskite and crystalline silicon (PK/c-Si) absorbers have the potential to push commercial silicon single junction devices beyond their current efficiency limit. However, their scale-up to industrially relevant sizes ...

Silicon heterojunction solar cells can employ p-type hydrogenated nanocrystalline silicon nc-Si:H(p) on their front side, since these can provide better transparency and contact resistance compared to hydrogenated p-type amorphous silicon layers. We invest ...

At the front contact of thin film silicon solar cells, the junction between the p-doped window layer and the n-type transparent electrode results in a barrier that must be surmounted by the charge carriers. The barrier height is governed by the work functi ...

The encapsulation of photovoltaic (PV) modules insulates solar cells and internal electrical components, and protects them from environmental stresses. Encapsulant delamination is a common mode of failure, and can appear immediately after manufacturing (quality issues) or it can occur over time (degradation). In both cases, the long-term impact of delamination on module performance is poorly quantified. In this work the causes and effects of delamination were examined in greater detail. Inhomogeneities duri

The role of secondary gas-phase reactions during plasma-enhanced chemical vapor deposition of microcrystalline silicon is a controversial subject. In this paper, we show that the enhancement of such reactions is associated with the improvement of material properties of absorber layers deposited at high constant rate. We detect powder, a product of secondary gas-phase reactions, via infrared laser absorption spectroscopy, laser light scattering, and optical emission spectroscopy. As the powder formation is i

Solar modules are currently characterised at standard test conditions (STC), defined at 1000 W/m2 and 25 °C. However, solar modules in actual outdoor operating conditions typically operate at lower illumination and higher temperature than STC, which signif ...

As the efficiency of commercial crystalline silicon solar cells approaches its maximum theoretical value, tandem architectures are becoming increasingly popular to continue the push to higher photovoltaic performances. Thin-film materials are particularly ...

In this work, we use periodic density functional theory(periodic DFT) to rigorously assign vibrational spectra measured on nanorough wet-processed hydrogenated Si(111) surfaces. We compare Si(111)-(1x1) surfaces etched by dilute HF and NH4F, featuring two ...

We study light scattering and absorption in thin film solar cells, using a model system of a sinusoidally textured silver reflector and dielectric layers of ZnO and amorphous silicon. Experimental results are compared to a theoretical model based on a Rayl ...

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). Since the properties of materials deposited by PEVCD are directly linked to the plasma properties, plasma diagnostics are very useful tools to optimize such devices. A novel diagnostic has been developed to measure in-sit

Substrates with extremely low roughness to allow the growth of good-quality silicon material but that nevertheless present high light trapping properties are presented. In a first application, silver reflectors are used in single and tandem-junction amorphous silicon (a-Si:H) solar cells. High initial (stable) efficiencies of 10.4 % (8.1 %) for single-junction a-Si:H cells on glass and 11.1 % (9.2 %) for tandem-junction a-Si:H/a-Si:H cells on plastic are obtained. A second application better suited to multi

Vapor-based processes are promising options to deposit metal halide perovskite solar cells in an industrial environment due to their ability to deposit uniform layers over large areas in a controlled environment without resorting to the use of (possibly to ...

High reflectivity is essential when a metal is used as back contact and reflector in thin-film silicon solar cells. We show that thermal annealing at 150 °C improves the reflectivity of silver films deposited by sputtering at room temperature on nanotextured substrates. The annealing provokes two interlinked effects: rearrangement of the silver layer with a modification of its morphology and an increase of up to 42% in the grain size of the polycrystalline film for the preferential orientation as measured b

Halide perovskite/crystalline silicon (c-Si) tandem solar cells promise power conversion efficiencies beyond the limits of single-junction cells. However, the local light-matter interactions of the perovskite material embedded in this pyramidal multijuncti ...

Silicon heterojunction (SHJ) solar cells have recently reached power conversion efficiencies above 25% with various device architectures and with industrial size (>200 cm(2)) wafers. Yet, for an accurate assessment of the efficiency potential and further d ...

Ethanol is used as a precursor during the growth of zinc oxide (ZnO) by low-pressure chemical vapor deposition (LPCVD). By adding ethanol, the surface of the deposited ZnO layer is flattened and its roughness is decreased about sevenfold. The layers become ...

High-performance transparent conducting oxides (TCOs) have significance for optimising PV performance. The efficiency of the resulting solar cells is dependent particularly on achieving high light scattering, low resistivity and low absorption (via low fre ...

Microchannel plates (MCPs) fabricated out of hydrogenated amorphous silicon offer a promising alternative to conventional lead glass ones. Progress in the fabrication process has allowed for detectors with higher aspect ratios, which significantly increase ...

In this contribution, we investigate the effect of post-deposition treatments on finished non-encapsulated thin-film microcrystalline silicon solar cells and show that annealing in vacuum leads to improved electrical properties of the solar cells, particul ...

Christophe Ballif

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Measurement of the Open-Circuit Voltage of Individual Subcells in a Dual-Junction Solar Cell

Low-Temperature Screen-Printed Metallization for the Scale-Up of Two-Terminal Perovskite-Silicon Tandems

Influence of the Dopant Gas Precursor in P-Type Nanocrystalline Silicon Layers on the Performance of Front Junction Heterojunction Solar Cells

Improvement of the open circuit voltage by modifying the transparent ITO front electrode in amorphous n-i-p solar cells

Delamination of c-Si Module Encapsulation: Insight into Causes and Long-Term Effects

Impact of secondary gas-phase reactions on microcrystalline silicon solar cells deposited at high rate

Optimized Design of Silicon Heterojunction Solar Cells for Field Operating Conditions

Palliating the efficiency loss due to shunting in perovskite/silicon tandem solar cells through modifying the resistive properties of the recombination junction

Quantitative Analysis of Nanorough Hydrogenated Si(111) Surfaces through Vibrational Spectral Assignment by Periodic DFT Calculations br

Diffraction and absorption enhancement from textured back reflectors of thin film solar cells

Optimization of high efficiency silicon heterojunction solar cells using silane-plasma diagnostics

Electrically flat/optically rough substrates for efficiencies above 10% in n-i-p thin-film silicon solar cells

Vapor Transport Deposition of Methylammonium Iodide for Perovskite Solar Cells

Highly reflective nanotextured sputtered silver back reflector for flexible high-efficiency n–i–p thin-film silicon solar cells

Multimodal Microscale Imaging of Textured Perovskite-Silicon Tandem Solar Cells

Loss Analysis of a 24.4%-Efficient Front-Junction Silicon Heterojunction Solar Cell and Opportunity for Localized Contacts

Ethanol-enriched low-pressure chemical vapor deposition ZnO bilayers: Properties and growth-A potential electrode for thin film solar cells

High-performance tandem silicon solar cells on F:SnO2

Characterization of Amorphous Silicon Based Microchannel Plates with High Aspect Ratio

Post-deposition treatment of microcrystalline silicon solar cells for improved performance on rough superstrates