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Microcrystalline Silicon (microcrystalline + silicon)

Distribution by Scientific Domains

Physics and Astronomy	71%

Selected Abstracts

Amorphous and Microcrystalline Silicon , Materials Science and Devices,

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2004
Norbert H. Nickel
This Special Issue reviews the latest experimental and theoretical studies in the field of amorphous, nano- and microcrystalline silicon covering materials preparation, electrical and optical properties, characterization of defects, the role of hydrogen, device fabrication and characterization, and novel device applications. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

High-efficiency µc-Si solar cells made by very high-frequency plasma-enhanced chemical vapor deposition

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2006
A. Gordijn
Abstract Microcrystalline silicon-based single-junction p,i,n solar cells have been fabricated by very high-frequency plasma enhanced chemical vapor deposition using a showerhead cathode at high pressures and under silane depletion conditions. The i -layers are made near the transition from amorphous to crystalline. It was found that, especially at high crystalline fractions, the open-circuit voltage and fill factor are very sensitive to the morphology of the substrate. At an i -layer deposition rate 0·45,nm/s, we have measured a stabilised efficiency of 10% (Voc,=,0·52,V, FF,=,0·74) for a cell made on texture-etched ZnO:Al. The performance is stable under light soaking. The defect density of the absorber layer is in the 1015,cm,3 range. In spite of the presence of oxygen contamination, good electrical properties and good infrared cell response are obtained. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Structural order on different length scales in amorphous silicon investigated by Raman spectroscopy

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2010
S. Muthmann
Abstract Parameters for the structural short (SRO) and medium range order (MRO) of hydrogenated amorphous silicon (a-Si:H) films on the edge of the microcrystalline silicon (µc-Si:H) phase transition were studied with Raman spectroscopy. The observed samples were deposited using radio frequency plasma enhanced chemical vapor deposition. The studied films were grown with various constant and non-constant silane concentrations (SCs). A substrate dependent correlation of SC to the intensity ratio (IMRO) of the transversal acoustical (TA) and the transversal optical (TO) phonon bands was found. A strong correlation between width and position of the (TO) phonon band was observed. These two easily accessible parameters show an increase of SRO when IMRO decreases. [source]

A new method used to control the structure of high rate microcrystalline silicon thin films

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
X. D. Zhang
Abstract We report a systematic study of plasma heating effect on microcrystalline silicon (,c-Si:H) deposition. Normally, substrate surface temperature increases with time during a high rate deposition of ,c-Si:H thin film, especially under a high power and high pressure condition. We deposited ,c-Si:H films using a very high frequency discharge under the high pressure and high power condition at a fixed heater temperature or a profiled heater temperature. Raman spectra with different wavelength excitations showed that a proper heater temperature profiling during ,c-Si:H deposition is an effective method to modify the structure of ,c-Si:H films, which can control the structure evolution to form a uniform crystallinity along the growth direction and reduce the amorphous incubation layer thickness (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Characterization of microcrystalline Si films deposited at low temperatures with high rates by atmospheric-pressure plasma CVD

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
K. Ouchi
Abstract Low-temperature and high-rate depositions of hydrogenated microcrystalline silicon (,c -Si:H) films are investigated using stable plasma excited at atmospheric pressure (AP) by supplying 150-MHz very high-frequency (VHF) power. VHF power density, H2/SiH4 ratio and plasma gap are varied as parameters under a fixed substrate temperature (Tsub) of 220 ,C. Increasing VHF power density and H2/SiH4 ratio is primarily important for the sufficient decomposition of source gas molecules, improving both deposition rate and film property. In addition, the plasma gap is found to be another crucial parameter in the deposition process using AP-VHF plasma. Numerical analyses on the temperature distribution around the plasma region have revealed that the steady-state surface temperature of the glass substrate becomes approximately 100 ,C higher than the back surface temperature (Tsub), which is caused by the moderate surface heating effect of the AP-VHF plasma. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Variation of the Fermi level in n-type microcrystalline silicon by electron bombardment and successive annealing: ESR and conductivity studies

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
Oleksandr Astakhov
Abstract ESR and conductivity studies have been preformed on ,c-Si:H exposed to 2 MeV electron bombardment and successive annealing in order to investigate the influence of the defect density on the electronic properties of n-type ,c-Si:H. With this approach one can vary the defect density in one and the same sample and directly deduce its influence on the electronic properties. The defect density is varied by 2 orders of magnitude with strong influence on the dark conductivity and electron spin resonance (ESR) properties. The relationship of ESR and conductivity data obtained over the whole defect density range is in agreement with the data obtained on the sets of samples deposited with different doping level. The results indicate that the Fermi level position in ,c-Si:H is defined by a balance of defect and donor states densities regardless of which of these quantities is varied. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The effect of aging on the dark conductivity and 1/f noise in hydrogenated microcrystalline silicon thin films

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
M. Güne
Abstract Aging hydrogenated microcrystalline silicon in air is found to affect both the dark conductivity and the 1/f noise. For a sample with a crystalline volume fraction of 0.39, the conductivity decreased by three orders of magnitude at 20 °C after short-term (10,20 hrs) exposure to air. The conductivity recovered after annealing to 160 °C. Long-term exposure (2 years) resulted in a permanent decrease by a factor of 16 at 20 °C even after annealing. Long-term aging also increased the conductivity activation energy from 0.193 eV to 0.342 eV. After short-term aging and below the annealing temperature, the conductivity prefactor ,0 and the activation energy E, follow a Meyer-Neldel type of relation. Conductance fluctuations measured for annealed and aged states show all the expected characteristics of 1/f noise. The spectra fit a power law with slope -1; the slope is not affected by temperature or aging. The magnitude of the noise decreases with temperature after aging, but by much less after annealing. A simple analysis of the product of conductivity and noise magnitude can be used to estimate the free carrier mobility (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Defects and structure of µc-SiOx:H deposited by PECVD

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
Lihong Xiao
Abstract Electronic transport and paramagnetic defects detected by Electron Spin Resonance (ESR) in both intrinsic and -type silicon oxide prepared by PECVD were investigated. The structure and alloy composition of the material were varied all the way from microcrystalline silicon (µc-Si:H) to amorphous silicon oxide (a-SiOX:H). The transition-phase-mixture material is called "microcrystalline silicon oxide" (µc-SiOX:H). In undoped samples we find a strong reduction of the dark conductivity from 10 -3to 10 -12 S/cm and an increase of the spin density from1017 to 3×1019 cm -3 as the crystallinity decreases from 80% to 0%. The variation of the dark conductivity in phosphorous doped samples was even higher from 101 to 10 -12 S/cm. ESR spectra of intrinsic material consist of a single featureless line with g-values in the range of 2.0043,2.005 depending on the structure and alloying. The spectra of -type material exhibit a broader range of g-values of 1.998,2.0043 due to strong variations of the Fermi level over the entire crystallinity range. The results are discussed within the frame of current understanding of µc-SiOX:H as a phase mixture of µc-Si:H crystallites embedded in a-SiOX:H matrix (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Amorphous and Microcrystalline Silicon , Materials Science and Devices,

Numerical modelling of transient photoconductivity for density-of-states determination in microcrystalline silicon

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2004
R. Brüggemann
Abstract Numerical modelling of transient photoconductivity in microcrystalline silicon allows to identify characteristic features for different models for the density-of-states in microcrystalline silicon. Construction of the density-of-states by Fourier-transform analysis of simulated transient photocurrents identifies discrepancies with the input density-of-states which may be helpful for refining the density-of-states from experimental data. Two scenarios are presented for the effect that the shift of the Fermi level or of n-type doping imposes on the transient photocurrent decay. States, masked and not directly accessible to electrons, may still be identified by the decay analysis. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Deposition of highly efficient microcrystalline silicon solar cells under conditions of low H2 dilution: the role of the transient depletion induced incubation layer

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2007
M. N. van den Donker
Abstract This paper addresses the plasma deposition of highly efficient microcrystalline silicon (,c-Si:H) p-i-n solar cells under conditions of high SiH4 utilization and low H2 dilution. It was established that the transient depletion of the initially present SiH4 source gas induces the formation of an amorphous incubation layer that prevents successful crystallite nucleation in the i-layer and leads to poor solar cell performance. The effect of this transient depletion induced incubation layer on solar cells was made visible through dedicated solar cell deposition series and selected area electron diffraction measurements. Applying a gas flow procedure at plasma ignition it was succeeded to prepare state-of-the-art ,c-Si:H material and solar cells under low hydrogen dilution conditions, highlighted by ,c-Si:H solar cells of up to 9·5% efficiency prepared using an undiluted source gas flow consisting solely of SiH4. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Optical properties of thin-film silicon solar cells with grating couplers

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 7 2006
C. Haase
Abstract The effect of grating couplers on the optical properties of silicon thin-film solar cells was studied by a comparison of experimental results with numerical simulations. The thin-film solar cells studied are based on microcrystalline silicon (,c-Si:H) absorber layers of thickness in the micrometer range. To investigate the light propagation in these cells, especially in the red wavelength region, three-dimensional power loss profiles are simulated. The influence of different grating parametres,such as period size, groove height, and shape of the grating,was studied to gain more insight into the light propagation within thin-film silicon solar cells and to determine an optimized light trapping scheme. The effect of the TCO front and TCO back side layer thickness was investigated. The calculated quantum efficiencies and short-circuit current densities are in good agreement with the experimental data. The simulations predict further optimization criteria. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Thin-film silicon solar cell technology

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2-3 2004
A. V. Shah
Abstract This paper describes the use, within p,i,n - and n,i,p -type solar cells, of hydrogenated amorphous silicon (a-Si:H) and hydrogenated microcrystalline silicon (,c-Si:H) thin films (layers), both deposited at low temperatures (200°C) by plasma-assisted chemical vapour deposition (PECVD), from a mixture of silane and hydrogen. Optical and electrical properties of the i -layers are described. These properties are linked to the microstructure and hence to the i -layer deposition rate, that in turn, affects throughput in production. The importance of contact and reflection layers in achieving low electrical and optical losses is explained, particularly for the superstrate case. Especially the required properties for the transparent conductive oxide (TCO) need to be well balanced in order to provide, at the same time, for high electrical conductivity (preferably by high electron mobility), low optical absorption and surface texture (for low optical losses and pronounced light trapping). Single-junction amorphous and microcrystalline p,i,n -type solar cells, as fabricated so far, are compared in their key parameters (Jsc, FF, Voc) with the [theoretical] limiting values. Tandem and multijunction cells are introduced; the ,c-Si: H/a-Si: H or [micromorph] tandem solar cell concept is explained in detail, and recent results obtained here are listed and commented. Factors governing the mass-production of thin-film silicon modules are determined both by inherent technical reasons, described in detail, and by economic considerations. The cumulative effect of these factors results in distinct efficiency reductions from values of record laboratory cells to statistical averages of production modules. Finally, applications of thin-film silicon PV modules, especially in building-integrated PV (BIPV) are shown. In this context, the energy yields of thin-film silicon modules emerge as a valuable gauge for module performance, and compare very favourably with those of other PV technologies. Copyright © 2004 John Wiley & Sons, Ltd. [source]