Publications de Gabriel Christmann

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

Christophe Ballif, Sylvain Nicolay, Gabriel Christmann, Mathieu Gérard Boccard

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 ...

2021

Advanced method for electrical characterization of carrier-selective passivating contacts using transfer-length-method measurements under variable illumination

Christophe Ballif, Antoine Descoeudres, Nicolas Badel, Sylvain Nicolay, Gabriel Christmann, Mathieu Gérard Boccard, Matthieu Despeisse, Jonas Geissbühler, Laurie-Lou Senaud, Bertrand Yves Paul Paviet-Salomon

2021

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

Christophe Ballif, Gabriel Christmann, Mathieu Gérard Boccard, Jean Cattin, Luca Massimiliano Antognini, Vincent Philippe Paratte, Julie Amandine Dreon

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 ...

2021

Lateral transport in silicon solar cells

Christophe Ballif, Gabriel Christmann, Mathieu Gérard Boccard, Jan Haschke

We investigate lateral charge carrier transport in crystalline silicon solar cells. Under typical operation illumination of high-efficiency solar cells, a significant population of electrons and holes exist in the silicon wafer, leading to a non-negligible ...

AIP2020

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

Christophe Ballif, Nicolas Badel, Antonin Faes, Jacques Levrat, Laura Ding, Sylvain Nicolay, Gabriel Christmann, Soo-Jin Moon, Arnaud Walter, Adriana Paracchino, Matthieu Despeisse, Bertrand Yves Paul Paviet-Salomon

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 ...

AMER CHEMICAL SOC2019

Rear-emitter silicon heterojunction solar cells with atomic layer deposited ZnO:Al serving as an alternative transparent conducting oxide to In2O3:Sn

Christophe Ballif, Antoine Descoeudres, Nicolas Badel, Sylvain Nicolay, Gabriel Christmann, Matthieu Despeisse, Loris Barraud

Here high-efficiency (above 21%) large-area silicon heterojunction solar cells with atomic layer deposited ZnO:Al as front- or back-side transparent conducting oxide are demonstrated. Photoconductance decay measurements indicate that the excellent chemical ...

2019

Complex Refractive Indices of Cesium–Formamidinium-Based Mixed-Halide Perovskites with Optical Band Gaps from 1.5 to 1.8 eV

Christophe Ballif, Sylvain Nicolay, Quentin Thomas Jeangros, Gabriel Christmann, Arnaud Walter, Jérémie Werner, Florent Sahli, Björn Niesen, Gizem Nogay, Philipp Friedrich Hermann Löper, Matthias Wolfgang Bräuninger, Peter Joseph Fiala, Chien-Jen Yang

Cesium-formamidinium-based mixed-halide perovskite materials with optical band gaps ranging from 1.5 to 1.8 eV are investigated by variable-angle spectroscopic ellipsometry. The determined complex refractive indices are shown to depend on the fabrication p ...

2018

Piezoelectric and structural properties of c-axis textured aluminium scandium nitride thin films up to high scandium content

Paul Muralt, Sylvain Nicolay, Gabriel Christmann, Stefan Mertin

2018

Interdigitated back contact silicon heterojunction solar cells featuring an interband tunnel junction enabling simplified processing

Christophe Ballif, Antoine Descoeudres, Nicolas Badel, Benjamin Strahm, Antonin Faes, Sylvain Nicolay, Quentin Thomas Jeangros, Gabriel Christmann, Stefaan De Wolf, Matthieu Despeisse, Loris Barraud, Jonas Geissbühler, Johannes Peter Seif, Andrea Tomasi, Bertrand Yves Paul Paviet-Salomon

This paper reports on the development of an innovative back-contacted crystalline silicon solar cell with passivating contacts featuring an interband tunnel junction at its electron-collecting contacts. In this novel architecture, named "tunnel-IBC", both ...

2018

Enhanced piezoelectric properties of c-axis textured aluminium scandium nitride thin films with high scandium content: influence of intrinsic stress and sputtering parameters

Paul Muralt, Silviu Cosmin Sandu, Clemens Benedict Nyffeler, Gabriel Christmann, Stefan Mertin, Mohammad Fazel Parsapour Kolour, Vladimir Pashchenko

Aluminium scandium nitride (ASN) exhibits a largely enhanced piezoelectric response as compared to aluminium nitride (AlN), which makes it an upcoming piezoelectric material for use in next generation RF filters, sensors, actuators and energy harvesting de ...

Ieee2017

Sputter Deposition Technology For Al((1-X))Sc(X)N Films With High Sc Concentration

Paul Muralt, Sylvain Nicolay, Gabriel Christmann, Stefan Mertin

Aluminium scandium nitride (Al1-xScxN) with its strongly enhanced piezoelectric response is the upcoming piezoelectric material of choice in next generation RF filters, sensors, actuators and energy harvesting devices. This paper will concentrate on the de ...

IEEE2017

ITO/MoOx/a-Si:H(i) Hole-Selective Contacts for Silicon Heterojunction Solar Cells: Degradation Mechanisms and Cell Integration

Christophe Ballif, Aïcha Hessler-Wyser, Antoine Descoeudres, Sylvain Nicolay, Quentin Thomas Jeangros, Gabriel Christmann, Davide Sacchetto, Matthieu Despeisse, Loris Barraud, Jonas Geissbühler

Molybdenum oxide is an efficient hole collector for silicon solar cells. However, its optoelectronic properties deteriorate during cell manufacturing. To assess this issue, the optoelectronic properties and microstructure of molybdenum oxide-based hole con ...

2017

Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth

Christophe Ballif, Antoine Descoeudres, Sylvain Nicolay, Quentin Thomas Jeangros, Gabriel Christmann, Stefaan De Wolf, Matthieu Despeisse, Loris Barraud, Johannes Peter Seif, Andrea Tomasi, Bertrand Yves Paul Paviet-Salomon, Jan Haschke

For crystalline-silicon solar cells, voltages close to the theoretical limit are nowadays readily achievable when using passivating contacts. Conversely, maximal current generation requires the integration of the electron and hole contacts at the back of t ...

Nature Publishing Group2017

Light-induced performance increase of silicon heterojunction solar cells

Christophe Ballif, Antoine Descoeudres, Jacques Levrat, Sylvain Nicolay, Gabriel Christmann, Stefaan De Wolf, Matthieu Despeisse, Eiji Kobayashi

Silicon heterojunction solar cells consist of crystalline silicon (c-Si) wafers coated with doped/intrinsic hydrogenated amorphous silicon (a-Si:H) bilayers for passivating-contact formation. Here, we unambiguously demonstrate that carrier injection either ...

American Institute of Physics2016

Impact of biexcitons on the relaxation mechanisms of polaritons in III-nitride based multiple quantum well microcavities

Jean-François Carlin, Benoît Marie Joseph Deveaud, Jean-Daniel Ganière, Jacques Levrat, Nicolas Grandjean, Raphaël Butté, Eric Feltin, Gabriel Christmann, Pierre Michel Corfdir, Georg Rossbach

We report on the direct observation of biexcitons in a III-nitride based multiple quantum well microcavity operating in the strong light-matter coupling regime by means of nonresonant continuous wave and time-resolved photoluminescence at low temperature. ...

2012

III-nitride based microcavities : towards polariton condensation at room temperature

Gabriel Christmann

This PhD thesis work describes the study of III-nitride based planar microcavities operating in the strong coupling regime at room temperature. The aim is to use the nonlinear emission properties of such samples in realistic devices. Furthermore these stud ...

EPFL2009

Tailoring the strong coupling regime in III-nitride based microcavities for room temperature polariton laser applications

Jean-François Carlin, Jacques Levrat, Nicolas Grandjean, Raphaël Butté, Eric Feltin, Gabriel Christmann

We report on the properties of III-nitride based microcavities (MCs) operating in the strong coupling regime (SCR) up to room temperature. We first discuss why this class of materials is well suited to investigate the physics of cavity polaritons, which ar ...

Wiley-Blackwell2009

Phase diagram of a polariton laser from cryogenic to room temperature

Jean-François Carlin, Jacques Levrat, Nicolas Grandjean, Raphaël Butté, Eric Feltin, Gabriel Christmann

The signature of the strong-coupling regime is unambiguously evidenced in a GaN-based microcavity (MC) above the polariton lasing threshold P-thr at room temperature through the observation of the upper polariton branch. The MC system exhibits a renormaliz ...

2009

Towards room temperature electrically pumped blue vertical cavity surface emitting lasers

Jean-François Carlin, Alexei Altoukhov, Gatien Cosendey, Jacques Levrat, Nicolas Grandjean, Raphaël Butté, Eric Feltin, Gabriel Christmann, Antonino Francesco Castiglia

The authors report on strategies to achieve lasing in electrically driven vertical cavity surface emitting lasers at room temperature, namely the improvement of the quality factor of a microcavity suited for electrical injection, the use of a ZnO contact t ...

Ieee2009

Spontaneous polarization buildup in a room-temperature polariton laser

Jean-François Carlin, Nicolas Grandjean, Raphaël Butté, Eric Feltin, Gabriel Christmann

We observe the buildup of strong (similar to 50%) spontaneous vector polarization in emission from a GaN-based polariton laser excited by short optical pulses at room temperature. The Stokes vector of emitted light changes its orientation randomly from one ...

2008