Publications by Gabriel Christmann

Related publications (32)

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

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

Current status of AlInN layers lattice-matched to GaN for photonics and electronics

Jean-François Carlin, Marcel Py, Julien Dorsaz, Nicolas Grandjean, Raphaël Butté, Eric Feltin, Sylvain Nicolay, Gabriel Christmann, Antonino Francesco Castiglia

We report on the current properties of Al1-x InxN (x approximate to 0.18) layers lattice- matched ( LM) to GaN and their specific use to realize nearly strain- free structures for photonic and electronic applications. Following a literature survey of the g ...

2007

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, 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

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

Light-induced performance increase of silicon heterojunction solar cells

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

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

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

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

Christophe Ballif, 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

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

Room-temperature polariton luminescence from a bulk GaN microcavity

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

We report strong exciton-photon coupling at room temperature in a hybrid high quality bulk 3 lambda/2 GaN cavity with a bottom lattice-matched AlInN/AlGaN distributed Bragg reflector through angle-resolved polarized photoluminescence (PL). Coupling of the ...

2006

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, Fazel Parsapour, 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

Room-temperature polariton lasing in semiconductor microcavities

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

We observe a room-temperature low-threshold transition to a coherent polariton state in bulk GaN microcavities in the strong-coupling regime. Nonresonant pulsed optical pumping produces rapid thermalization and yields a clear emission threshold of 1 mW, co ...

2007

Large vacuum Rabi splitting in a multiple quantum well GaN-based microcavity in the strong-coupling regime

Jean-François Carlin, Pierre Stadelmann, Nicolas Grandjean, Raphaël Butté, Eric Feltin, Gabriel Christmann, Antonino Francesco Castiglia, Anas Mouti

An AlInN/AlGaN microcavity (MC) containing a GaN/Al0.2Ga0.8N multiple quantum well (MQW) structure is investigated through room temperature (RT) photoluminescence and reflectivity experiments. A vacuum Rabi splitting as large as 50 meV at RT is reported fo ...

2008

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

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

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

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

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

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

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

Impact of disorder on high quality factor III-V nitride microcavities

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

The authors report on the micron scale characterization of a monolithic GaN microcavity (MC) with lattice matched AlInN/GaN distributed Bragg reflectors by means of a microtransmission setup. This technique allows extracting very high quality factors (Q up ...

2006