Low-temperature plasma-deposited silicon epitaxial films: Growth and properties

Demaurex, Bénédicte; Bartlomé, R.; Seif, Johannes P.; Geissbühler, Jonas; Alexander, Duncan T. L.; Jeangros, Quentin; Ballif, Christophe; Wolf, Stefaan De

doi:10.1063/1.4892095

Cited by 21 publications

(25 citation statements)

References 57 publications

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“…All the findings presented so far are in line with previous reports [16], [18], [61], [62]. According to these results and our best knowledge, we tested the most promising and simple approaches in devices which will be presented and discussed in the following.…”

Section: E Summary Of Strategies For Nanocrystalline Layerssupporting

confidence: 87%

“…Gas Variation 1) Replacing Silane by Disilane: According to literature, the silane depletion fraction is one of the fundamental factors determining the growth mode of silicon layers, i.e., either μc-Si:H or a-Si:H [18], [61]. Similar conclusions were drawn for the growth of homoepitaxial silicon layers [62]. Therefore, a simple approach to facilitate the nucleation of μc-Si:H layers is the use of Si-precursor gases that are easier to dissociate compared with SiH 4 and, therefore, enable to reach high depletion regimes more easily.…”

Section: Resultsmentioning

confidence: 60%

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Strategies for Doped Nanocrystalline Silicon Integration in Silicon Heterojunction Solar Cells

Seif

Descoeudres

Nogay

et al. 2016

IEEE J. Photovoltaics

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Carrier collection in silicon heterojunction (SHJ) solar cells is usually achieved by doped amorphous silicon layers of a few nanometers, deposited at opposite sides of the crystalline silicon wafer. These layers are often defect-rich, resulting in modest doping efficiencies, parasitic optical absorption when applied at the front of solar cells, and high contact resistivities with the adjacent transparent electrodes. Their substitution by equally thin doped nanocrystalline silicon layers has often been argued to resolve these drawbacks. However, low-temperature deposition of highly crystalline doped layers of such thickness on amorphous surfaces demands sophisticated deposition engineering. In this paper, we review and discuss different strategies to facilitate the nucleation of nanocrystalline silicon layers and assess their compatibility with SHJ solar cell fabrication. We also implement the obtained layers into devices, yielding solar cells with fill factor values of over 79% and efficiencies of over 21.1%, clearly underlining the promise this material holds for SHJ solar cell applications.Index Terms-Microcrystalline silicon, nanocrystalline silicon, silicon heterojunctions (SHJs), solar cells.

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Section: E Summary Of Strategies For Nanocrystalline Layerssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 60%

Strategies for Doped Nanocrystalline Silicon Integration in Silicon Heterojunction Solar Cells

Seif

Descoeudres

Nogay

et al. 2016

IEEE J. Photovoltaics

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“…The collimated infrared beam of the QCL was first modulated with a mechanical chopper at a frequency of 1 kHz, then was split into two beamlets. Similarily, it was found in a separate study that thin films deposited on c-Si substrate yield an epitaxy to a-Si:H transition region situated between 3% and 9% [26]. With this approach, the difference between the SiH 4 consumption efficiency, measured in the pumping line, and the SiH 4 depletion fraction, measured in the reactor volume, could be confirmed experimentally and theoretically.…”

Section: Monitoring Of Pecvd Processes Containing Silanesupporting

confidence: 84%

In Situ Monitoring Capabiities of Quantum Cascade Laser Absorption Spectroscopy in Industrial Plasma Processes

Lang

Macherius

Glitsch

et al. 2015

Contrib. Plasma Phys.

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Plasmas in interaction with surfaces are of key importance in a wide range of applications, which include materials technology, microelectronics, environmental issues, and biomedicine. The intense use of plasma technological processes demands proper plasma diagnostic techniques for monitoring, controlling and optimization purposes in industrial environments. In particular, for the improvement of the efficiency of a production process, in situ diagnostic techniques with online capabilities are favorable. From the middle of the last decade a variety of phenomena in molecular non-equilibrium plasmas in which many short-lived and stable species are produced have been successfully studied with quantum cascade laser absorption spectroscopy (QCLAS) in the mid-infrared spectral range. It has been possible to determine absolute concentrations of species, temperatures, degrees of dissociation, dynamics of reaction processes and phenomena involving plasma-surface interactions using spectroscopy, thereby providing a link with chemical and kinetic modelling of the plasma. Since quantum cascade lasers (QCLs) emit near room temperature, i.e., without the need of cryogenic cooling, very compact and robust spectroscopic instruments can be designed. This has stimulated the adaptation of infrared spectroscopic techniques to industrial requirements. Recent applications of infrared absorption spectroscopy using QCLs for in situ monitoring of plasma processes in industrial environments are reviewed. Examples which emphasize the capabilities of QCLAS as plasma diagnostic technique in industrial plasma processes will be given.

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“…For this, we explored deposition conditions similar to those fostering nanocrystalline silicon thin-film growth [53][54][55] and silicon epitaxy 56 , hence characterized by a considerably lower silane concentration in the deposition plasma than conventional doped a-Si:H layers. Recall that nanocrystalline Si:H thin films typically present a nucleation region where the material is still amorphous, the so-called protocrystalline growth regime 57 , which has a thickness that may vary up to several tens of nanometres, depending on the deposition parameters 58 .…”

Section: Requirements For E Cient Tunnel-ibc Solar Cellsmentioning

confidence: 99%

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

et al. 2017

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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 the solar cell to liberate its front from any shadowing loss. Recently, the world-record e ciency for crystalline-silicon singlejunction solar cells was achieved by merging these two approaches in a single device; however, the complexity of fabricating this class of devices raises concerns about their commercial potential. Here we show a contacting method that substantially simplifies the architecture and fabrication of back-contacted silicon solar cells. We exploit the surface-dependent growth of silicon thin films, deposited by plasma processes, to eliminate the patterning of one of the doped carrier-collecting layers. Then, using only one alignment step for electrode definition, we fabricate a proof-of-concept 9-cm 2 tunnel-interdigitated backcontact solar cell with a certified conversion e ciency >22.5%. I n recent decades, the market of photovoltaics has been consistently growing and the yearly installed photovoltaic capacity has increased from 328 MW peak in 2001 to 50 GW peak in 2015. This resulted in 2016 in a cumulative capacity of 235 GW peak (ref. 1), largely based on crystalline-silicon (c-Si) solar-cell technologies 2 , and contributing to about 1.3% of the global electricity production 3 . To further increase this number, the cost-competitiveness of photovoltaics must surpass that of classic, non-renewable energy sources, and one route towards this goal is to raise the conversion efficiency of industrial c-Si solar cells 4,5 .High power conversion efficiencies require maximizing the solar-cell electrical parameters: open-circuit voltage (V oc ), fillfactor (FF) and short-circuit current density (J sc ). For the V oc and FF, this is possible by using passivating contacts, employing silicon oxide or hydrogenated amorphous silicon (a-Si:H) thin films to minimize charge carrier recombination at the electrical contacts to the c-Si wafer, with demonstrated record efficiencies for two-sidecontacted solar cells of 25.1% (refs 6,7). Maximum J sc values can be achieved using a back-contacted architecture, eliminating front metal electrode shadowing and minimizing optical reflection and absorption losses at the front. Small-sized back-contacted solar cells, based on diffused silicon homo-junctions, were realized at several research institutes (refs 8-11), showing a best conversion efficiency up to 24.4% (ref. 12). Industrially, the back-contacted architecture was pioneered by Sunpower, recently reporting on large-area devices with very high J sc values and efficiencies surpassing 25% (ref. 13). Considering these achievements, integrating passivating contacts in a back-contacted architecture is the obvious c-Si single-junction solar-cell design towards highest conversion efficiencies. Such an approach has increasingly been researched in both academia and indust...

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Low-temperature plasma-deposited silicon epitaxial films: Growth and properties

Cited by 21 publications

References 57 publications

Strategies for Doped Nanocrystalline Silicon Integration in Silicon Heterojunction Solar Cells

Strategies for Doped Nanocrystalline Silicon Integration in Silicon Heterojunction Solar Cells

In Situ Monitoring Capabiities of Quantum Cascade Laser Absorption Spectroscopy in Industrial Plasma Processes

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

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