Publications by Benjamin Strahm

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

Improved amorphous/crystalline silicon interface passivation by hydrogen plasma treatment

Christophe Ballif, Antoine Descoeudres, Benjamin Strahm, Bénédicte Demaurex, Stefaan De Wolf, Loris Barraud, Jakub Holovsky, Johannes Peter Seif

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. We show a dramatic improvem ...

2011

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

Christophe Ballif, Benjamin Strahm, Andrea Feltrin, Gaetano Parascandolo, Grégory Bugnon

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 ...

Elsevier B.V Amsterdam2011

Input silane concentration effect on the a-Si:H to uc-Si:H transition width

Christophe Ballif, Christoph Hollenstein, Fanny Sculati-Meillaud, Benjamin Strahm, Andrea Feltrin, Grégory Bugnon

In this work the microstructure transition width from amorphous to microcrystalline silicon is discussed. It is shown that the width of the transition depends on the input silane concentration level and indirectly on the silane depletion level. The higher ...

2010

Powder formation in SiH[sub 4]–H[sub 2] discharge in large area capacitively coupled reactors: A study of the combined effect of interelectrode distance and pressure

Christoph Hollenstein, Benjamin Strahm

One of the main challenges for silicon thin film deposition for solar cell applications is to achieve high rate deposition in order to reduce the manufacturing costs. However, when silane and hydrogen are used as precursor gas in parallel plate plasma-enha ...

American Institute of Physics2010

Laser applications in thin-film photovoltaics

Christophe Ballif, Benjamin Strahm, Andrea Feltrin

We review laser applications in thin-film photovoltaics (thin-film Si, CdTe, and Cu(In,Ga)Se2 solar cells). Lasers are applied in this growing field to manufacture modules, to monitor Si deposition processes, and to characterize opto-electrical properties ...

Springer Verlag2009

Optical emission spectroscopy to diagnose powder formation in SiH4-H2 discharges

Christophe Ballif, Benjamin Strahm, Andrea Feltrin

Silane and hydrogen discharges are widely used for the deposition of silicon thin film solar cells in large area plasmaenhanced chemical vapor deposition reactors. In the case of microcrystalline silicon thin film solar cells, it is of crucial importance t ...

2009

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

Christophe Ballif, Christoph Hollenstein, Benjamin Strahm, Andrea Feltrin, Grégory Bugnon

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 ...

2009

Laser-based plasma diagnostics for PECVD of silicon thin films

Christophe Ballif, Benjamin Strahm, Andrea Feltrin

We present two laser systems to monitor plasma conditions in a plasma-enhanced chemical vapor deposition chamber. The first optical system is a high-resolution quantum cascade laser-based infrared absorption spectrometer designed to measure the input silan ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2009

Non-intrusive plasma diagnostics for the deposition of large area thin film silicon

Christoph Hollenstein, Alan Howling, Benjamin Strahm

Plasma diagnostics for large area, industrial RF parallel-plate reactors can be useful for process optimization and monitoring, provided that their implementation is practical and non-intrusive. For instance, Fourier transform infrared (FTIR) absorption sp ...

Elsevier2009

Uniformity of silicon microcrystallinity in large area RF capacitive reactors

Christoph Hollenstein, Alan Howling, Benjamin Strahm

2008

Plasma silane concentration as a determining factor for the transition from amorphous to microcrystalline silicon in SiH4/H-2 discharges

Laurent Fabien Hubert Sansonnens, Christoph Hollenstein, Alan Howling, Benjamin Strahm

In this work, the microstructure transition from amorphous to microcrystalline silicon is defined in terms of the silane concentration in the plasma as opposed to the silane concentration in the input gas flow. In situ Fourier transform infrared absorption ...

2007

Optimization of microcrystaline silicon deposition efficiency

Laurent Fabien Hubert Sansonnens, Christoph Hollenstein, Alan Howling, Benjamin Strahm

2007

Investigations of radio-frequency, capacitively-coupled large area industrial reactor : cost-effective production of thin film microcrystalline silicon for solar cells

Benjamin Strahm

The constant energy consumption and world-wide demography expansion add to the potential risks of ecological and human disaster associated with global warming. This makes it a necessity to develop renewable energy technologies such as photovoltaic energy. ...

EPFL2007

Fast equilibration of silane/hydrogen plasmas in large area RF capacitive reactors monitored by optical emission spectroscopy

Laurent Fabien Hubert Sansonnens, Christoph Hollenstein, Alan Howling, Benjamin Strahm

The optimal plasma parameters for plasma processing, such as deposition of microcrystalline silicon from silane and hydrogen, are generally chosen in steady-state discharge conditions. However, this steady state must be reached in a short time after plasma ...

2007

Optimization of the microcrystalline silicon deposition efficiency

Laurent Fabien Hubert Sansonnens, Christoph Hollenstein, Alan Howling, Benjamin Strahm

Cost reduction constraints for microcrystalline silicon thin film photovoltaic solar cells require high deposition rates and high silane gas utilization efficiencies. If the requirements in deposition rate have sometimes been fulfilled, it is generally not ...

2007

Plasma diagnostics as a tool for process optimization

Christoph Hollenstein, Alan Howling, Benjamin Strahm

2007

Fast growth of microcrystalline silicon solar cells on LP-CVD ZnO in industrial KAI PECVD reactors

Laurent Fabien Hubert Sansonnens, Christoph Hollenstein, Alan Howling, Benjamin Strahm, Cédric Bucher

2006

Measurements and consequences of nonuniform radio frequency plasma potential due to surface asymmetry in large area radio frequency capacitive reactors

Laurent Fabien Hubert Sansonnens, Christoph Hollenstein, Alan Howling, Lukas Derendinger, Benjamin Strahm

In large area reactors, a local asymmetry of the electrode area, due to lateral grounded walls, causes a perturbation in rf plasma potential, due to the redistribution of lateral rf current, which propagates along the resistive plasma between capacitive sh ...

2005