Solvent refining of silicon for solar cells – some practical aspects

Arnberg, L.; Fredriksson, Hasse; Ekerot, S.; Tadesse, Abel

doi:10.1016/j.jcrysgro.2019.125332

Cited by 3 publications

(5 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…14,15 The essence of the alloy refining method of Si is to use the principle of chemical reconstruction to realize the selective modification and denaturing of metallic and nonmetallic impurities in Si, which can weaken the combination between impurities and the Si matrix and enhance the removal of impurities at the interface. 16 Its connotation mainly includes two aspects: one is the alloy refining process using a large number of metal liquidating agents; 17−21 the other is the process of impurity modification by adding a small amount of impurity modifier on the basis of the molten refining system. 14,15,22−28 Metal liquidating agents and modifiers are collectively referred to as impurity chemical reconstruction medium, which are mainly transition metals such as Cu, Fe, Sn, Ti, and the main group metals such as Al and Zn.…”

Section: Introductionmentioning

confidence: 99%

“…The common characteristics of these metal elements are that they have a very small separation coefficient (10 −4 −10 −8 ) in Si, which is conducive to the efficient separation of the medium. 12,16 The second of these metal elements in the electron configuration are more easy to lose one electron to form a variable valence state and has not filled the valence shell d orbitals. These metals are easy to interact with Si, B, and P impurities or form compounds with characteristic chemical structures (such as coordination bonds) to change the activity or phase structure of impurity elements so as to achieve the purpose of chemical reconstruction of impurities.…”

Section: Introductionmentioning

confidence: 99%

“…The process of Si purification is accompanied by the migration of impurity elements and the transformation of impurity phases. Chemical reconstruction can change the morphology and location of impurities, such as the transformation from elemental elements to compounds and the transformation from the solid solution of the matrix to precipitated phases at grain boundaries or phase boundaries. , The essence of the alloy refining method of Si is to use the principle of chemical reconstruction to realize the selective modification and denaturing of metallic and nonmetallic impurities in Si, which can weaken the combination between impurities and the Si matrix and enhance the removal of impurities at the interface . Its connotation mainly includes two aspects: one is the alloy refining process using a large number of metal liquidating agents; − the other is the process of impurity modification by adding a small amount of impurity modifier on the basis of the molten refining system. ,,− Metal liquidating agents and modifiers are collectively referred to as impurity chemical reconstruction medium, which are mainly transition metals such as Cu, Fe, Sn, Ti, and the main group metals such as Al and Zn.…”

Section: Introductionmentioning

confidence: 99%

“…Its connotation mainly includes two aspects: one is the alloy refining process using a large number of metal liquidating agents; − the other is the process of impurity modification by adding a small amount of impurity modifier on the basis of the molten refining system. ,,− Metal liquidating agents and modifiers are collectively referred to as impurity chemical reconstruction medium, which are mainly transition metals such as Cu, Fe, Sn, Ti, and the main group metals such as Al and Zn. The common characteristics of these metal elements are that they have a very small separation coefficient (10 –4 –10 –8 ) in Si, which is conducive to the efficient separation of the medium. , The second of these metal elements in the electron configuration are more easy to lose one electron to form a variable valence state and has not filled the valence shell d orbitals. These metals are easy to interact with Si, B, and P impurities or form compounds with characteristic chemical structures (such as coordination bonds) to change the activity or phase structure of impurity elements so as to achieve the purpose of chemical reconstruction of impurities …”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Enhanced In Situ Separation of Boron at the Silicon Alloy Solidification Interface through Innovating the Impurity Chemical Reconstruction Approach for SoG-Si

Qian

Zhou

et al. 2021

ACS Sustainable Chem. Eng.

View full text Add to dashboard Cite

Removal of trace impurities such as boron (B) and phosphorus (P) has always been a challenge for the preparation of solar-grade silicon (SoG-Si). Chemical reconstruction has been thought to be an effective way to remove trace impurities by changing the phase structure and location of impurities. The traditional way of the chemical reconstruction of impurities at the grain boundary after solidification inevitably relies on the subsequent separation of crystalline Si and chemical reconstruction medium. Thus, we develop a new method for the chemical reconstruction of B at the front of the solidification interface of the Si alloy, which provides advantages for the in situ separation of the reconstructed impurity phase in the supergravity filtration separation process. The chemical reconstruction of B at the solidification front of the Si alloy has been realized by adding 25–75% of the liquation agent aluminum (Al) and about 10 000 ppm of the impurity modifier agent titanium (Ti) with the help of Thermo-Calc thermodynamic calculation and experimental verification. The influence mechanism of the supergravity field on the precipitation behavior of the chemically reconstructed phase TiB2 is revealed by the derived Maxwell–Stefan (MS) equation under the action of the supergravity field. A special filter-type combined crucible is skillfully designed and strictly controlled to cool the crucible containing the alloy melt at a constant temperature gradient under the supergravity field to achieve in situ separation of impurities at the solid–liquid interface of the Si alloy. The chemical reconstruction phase TiB2 is mainly retained on the surface of crystalline Si during the process of supergravity centrifugal filtration, which is more suitable for the deep removal of the B impurity and B content in Si drops below 1.5 ppm by simple pickling. In addition, the Si–Al–(Ti) alloy with a small amount of impurities obtained after centrifugal filtration separation can be further used for the chemical reconstruction of impurities, and the recycling of chemical reconstruction medium has been achieved. The present work proposes a new idea of chemical reconstruction of impurities at the front of alloy solidification and in situ separation, which expands the way of in situ separation of trace impurities at the solid–liquid interface of the alloy.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Enhanced In Situ Separation of Boron at the Silicon Alloy Solidification Interface through Innovating the Impurity Chemical Reconstruction Approach for SoG-Si

Qian

Zhou

et al. 2021

ACS Sustainable Chem. Eng.

View full text Add to dashboard Cite

show abstract

“…The vacuum refining process can be applied to treat steel, nickel super alloys, aluminum, and copper melts . Solar-grade silicon (SoG-Si) is a special grade of silicon, − which is free of impurities (6 N) and has a maximum limit of phosphorus of about 0.1 ppmw. Vacuum refining is recently used for silicon purification to remove phosphorus and is a candidate process in SoG-Si production, ,,, and it is scaled up in pilot production .…”

Section: Introductionmentioning

confidence: 99%

Selective Vacuum Evaporation by the Control of the Chemistry of Gas Phase in Vacuum Refining of Si

et al. 2021

View full text Add to dashboard Cite

The evaporation of P from liquid Si under vacuum and reduced pressures of H 2 , He, and Ar was studied to evaluate the feasibility of effective P removal with insignificant Si loss. It was found that the introduction of Ar and He inert gases at low pressures reduces the rate of P removal, and their pressure decrease will increase the process rate. Moreover, the kinetics of P removal was higher in He than in Ar, with simultaneous lower Si loss. Under reduced pressures of H 2 gas, however, the P removal rate was higher than that under vacuum conditions with the lowest Si loss. Quantum chemistry and dynamics simulations were applied, and the results indicated that P can maintain its momentum for longer distances in H 2 once it is evaporated from the melt surface and then can travel far away from the surface, while Si atoms lose their momentum in closer distances, yielding less net Si flux to the gas phase. Moreover, this distance is significantly increased with decreasing pressure for H 2 , He, and Ar gases; however, it is the largest for H 2 and the lowest for Ar for a given pressure, while the temperature effect is insignificant. The rate of P evaporation was accelerated by applying an additional vacuum tube close to the melt surface for taking out the hot gas particles before they lose their temperature and velocity. It was shown that this technique contributes to the rate of process by preventing condensing gas stream back to the melt surface.Article pubs.acs.org/Langmuir

show abstract

A Novel Method of Purifying Metallurgical-Grade Silicon Using Mn as an Impurity Trapping Agent

Zhu

Wei

et al. 2021

Metall Mater Trans B

View full text Add to dashboard Cite

Solvent refining of silicon for solar cells – some practical aspects

Cited by 3 publications

References 12 publications

Enhanced In Situ Separation of Boron at the Silicon Alloy Solidification Interface through Innovating the Impurity Chemical Reconstruction Approach for SoG-Si

Enhanced In Situ Separation of Boron at the Silicon Alloy Solidification Interface through Innovating the Impurity Chemical Reconstruction Approach for SoG-Si

Selective Vacuum Evaporation by the Control of the Chemistry of Gas Phase in Vacuum Refining of Si

A Novel Method of Purifying Metallurgical-Grade Silicon Using Mn as an Impurity Trapping Agent

Contact Info

Product

Resources

About