Analysis of oxygen incorporation in unidirectionally solidified multicrystalline silicon for solar cells

Matsuo, Hitoshi; Ganesh, R. Bairava; Nakano, Satoshi; Liu, Lijun; Arafune, Koji; Ohshita, Yoshio; Yamaguchi, Masafumi; Kakimoto, Koichi

doi:10.1016/j.jcrysgro.2007.12.017

Cited by 56 publications

(27 citation statements)

References 12 publications

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“…Coating material made of Si 3 N 4 exists between silicon melt and a quartz crucible in the case of the unidirectional solidification method, and it is not clear how oxygen is transferred from the crucible wall through the Si 3 N 4 coating. We concluded from results of Fourier transform infrared spectroscopy (FTIR) in our previous study that oxygen was dissolved from a crucible wall through the Si 3 N 4 coating by showing the existence of a boundary layer of oxygen near a crucible wall [6]. Oxygen was dissolved from a quartz crucible into silicon melt in the case of the Czochralski method.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamical analysis of oxygen incorporation from a quartz crucible during solidification of multicrystalline silicon for solar cell

Matsuo

Ganesh

Nakano

et al. 2008

Journal of Crystal Growth

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Section: Introductionmentioning

confidence: 99%

Thermodynamical analysis of oxygen incorporation from a quartz crucible during solidification of multicrystalline silicon for solar cell

Matsuo

Ganesh

Nakano

et al. 2008

Journal of Crystal Growth

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“…Many simulations of impurity transport have been reported. [11][12][13][14][15][16][17][18][19][20][21][22] Some of these previous investigations included only local simulations [11][12][13][14][15][16][17] that neglected the mass transport of the impurities in the gas phase. In other cases, the reported simulations included results of global simulations, [18][19][20][21] some of which only neglected mass transport of oxygen and carbon in the melt, 18) whereas others neglected carbon transfer for both the gas and the silicon melt.…”

Section: )mentioning

confidence: 99%

“…Contamination with light elements during the DS process is governed by the mass transport of impurities 22) similar in that of the CZ method. Carbon is one of the major impurities in multicrystalline silicon ingots, and it affects the density and electrical activity of dislocations.…”

Section: )mentioning

confidence: 99%

Silicon bulk growth for solar cells: Science and technology

Kakimoto

Gao

Nakano

et al. 2017

Jpn. J. Appl. Phys.

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The photovoltaic industry is in a phase of rapid expansion, growing by more than 30% per annum over the last few decades. Almost all commercial solar cells presently use single-crystalline or multicrystalline silicon wafers similar to those used in microelectronics; meanwhile, thin-film compounds and alloy solar cells are currently under development. The laboratory performance of these cells, at 26% solar energy conversion efficiency, is now approaching thermodynamic limits, with the challenge being to incorporate these improvements into low-cost commercial products. Improvements in the optical design of cells, particularly in their ability to trap weakly absorbed light, have also led to increasing interest in thin-film cells based on polycrystalline silicon; these cells have advantages over other thin-film photovoltaic candidates. This paper provides an overview of silicon-based solar cell research, especially the development of silicon wafers for solar cells, from the viewpoint of growing both singlecrystalline and multicrystalline wafers.

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“…Similar to the Czochralski method, the unidirectional solidification is connected with transport of impurities. 1 Carbon and oxygen are two of the major impurities in multicrystalline silicon. If the carbon concentration exceeds 1 × 10 16 atom/cm 3 , it will markedly influence the precipitation of oxygen during thermal annealing of crystals and during device processing of the wafers cut from these crystals.…”

Section: Introductionmentioning

confidence: 99%

Reducing impurities of multicrystalline silicon in a unidirectional solidification furnace for solar cells

Gao

Nakano

Kakimoto

2011

JOM

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How would you……describe the overall significance of this paper? This paper proposed some methods to reduce the impurities of carbon and oxygen during the production of multicrystalline silicon. Therefore, high-quality and high-efficiency multicrystalline silicon can be obtained by the present solutions.…describe this work to a materials science and engineering professional with no experience in your technical specialty? We theoretically analyzed the incorporation mechanism of impurities of carbon and oxygen, and proposed to use a crucible cover to effectively reduce the carbon and oxygen impurities. Impurities can be further reduced if a reaction between the crucible and the graphite susceptor is prohibited.…describe this work to a layperson? Multicrystalline silicon has now become the main material in the photovoltaic market because of its low production cost and because of the relative high conversion efficiency of solar cells made from this material. The impurities of carbon and oxygen can markedly damage the quality and conversion efficiency of multicrystalline silicon. This paper mainly deals with the purification of carbon and oxygen impurities during production.Multicrystalline silicon has now become the main material in the photovoltaic market because of its low production cost and the relative high conversion efficiency of solar cells made from this material. Effective control of carbon and oxygen impurities in the crystal is required for the production of a high-quality component. In order to reduce impurity levels in a unidirectional solidification furnace, it is proposed to add a crucible cover to the casting process. Results from numerical simulations indicate a marked reduction of carbon impurity in a multicrystalline silicon ingot. The effect of crucible cover material on impurities in multicrystalline silicon was also investigated. These results show that the carbon concentration within the silicon ingot can be reduced by 10 times if the cover is made from carbon and by 1,000 times if the cover is made from tungsten. These results show that an effective and economical method for designing a cover is to use carbon and deposit a thin layer of tungsten on it. Experimental tests have also been carried out by placing a tungsten cover above the crucible. Results indicated that the carbon impurity has significantly decreased; however, the measured carbon concentration in the crystal is larger than the theoretically predicted value, despite the use of a crucible cover. A theoretical analysis has shown that this difference is due to a reaction between the crucible and the graphite susceptor. Furthermore, global simulations have shown that this reaction has a marked effect on carbon and oxygen impurities. When the carbon activity on the surface of the graphite susceptor increases, both oxygen and carbon impurities in crystal increase rapidly. Therefore, the production of high-purity multicrystalline silicon can be improved by designing a crucible cover with a thin layer of tungsten on it and by setting a fr...

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Analysis of oxygen incorporation in unidirectionally solidified multicrystalline silicon for solar cells

Cited by 56 publications

References 12 publications

Thermodynamical analysis of oxygen incorporation from a quartz crucible during solidification of multicrystalline silicon for solar cell

Thermodynamical analysis of oxygen incorporation from a quartz crucible during solidification of multicrystalline silicon for solar cell

Silicon bulk growth for solar cells: Science and technology

Reducing impurities of multicrystalline silicon in a unidirectional solidification furnace for solar cells

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