Search

A new approach was proposed to prepare multi-products, high-purity Si powders, bulk Si, and Si/TiSi 2 materials (eutectic Si-Ti), simultaneously using inexpensive low-purity Si (99.3%) and metallurgical waste—Ti-bearing blast furnace slag. TiO 2 in Ti-bearing blast furnace slag was first reduced by Si to form a Si-Ti alloy which was then separated into high-purity bulk Si (99.97%) and Si/TiSi 2 materials (99.4%) using directional solidification. The bulk Si could be repeatedly recycled as a reductant, or further upgraded to prepare super-pure Si powders (99.995%) after acid leaching. The new approach shows many sustainable and economic benefits, such as no carbon gas emission, low acid consumption and Si loss, recyclable Si reductant, widely-used multi-products employing one approach, and rapid consumption of accumulated Ti-bearing blast furnace slag. • A new approach was proposed to clean up the Ti-bearing blast furnace slag. • Multi-products could be prepared simultaneously throughout one approach. • Most of Si could be recycled as reductant repeatedly. • Most of impurities could be removed to obtain high-purity Si and Ti materials. • Si-Ti alloy could be separated into bulk Si and eutectic Si-Ti alloy. [ABSTRACT FROM AUTHOR]

Small amounts of Ti (<2037 ppma) were employed as an additive to enhance B removal from Si in electromagnetic solidification refining with an Al–Si alloy. The B removal process was investigated by varying the initial concentration of Ti, the cooling rate, and the liquidus temperature of the Al–Si alloy. Experimental results show that the small amounts of Ti were primarily responsible for enhancing B removal. This B removal process was more efficient at lower cooling rates combined with the use of Al–Si alloy solvents having lower liquidus temperatures. With the addition of 2037 ppma Ti, the residual B in the refined Si could be controlled to 1.2 ppma, which meets the requirements for manufacturing solar cells. The added Ti could be simultaneously removed because of its extremely low segregation coefficient between solid Si and liquid Al–Si alloy. Although trace amounts of Ti and Al were present in the refined Si, they are expected to be removed in the next processing step, which is directional solidification in vacuum. Finally, the mechanism of this B removal process is discussed. [ABSTRACT FROM AUTHOR]

• A new technology for simultaneous recycle of Al-Si scraps and purification of Si. • Two products, high-purity Si and low-Fe eutectic Al-Si alloy, were prepared simultaneously. • Critical concentrations of Fe in the eutectic Al-Si-Fe-(Mn/Cr) alloy were experimentally determined for the first time. Currently, the elimination of Fe from Al-Si alloy for recycling Al-Si scraps, and the purification of Si using Al-Si solvent for recycling Si wafers in solar cells or production of new Si wafers, are two totally different research technologies and topics. A new approach is proposed in this study to combine the two different technologies into a single one which can not only recycle spent Si wafers but also Al-Si scrap simultaneously. The new approach is promising for cost reduction and environmental conservation, because two widely used products, high-purity Si and low Fe eutectic Al-Si alloys, can be prepared simultaneously via electromagnetic directional crystallization. The Al-Si-Fe-(Mn/Cr) melt was separated into a low-Fe eutectic Al-Si alloy (eutectic Al-Si-Fe-(Mn/Cr) alloy) and agglomerated high-purity Si crystals. The critical concentration of Fe (theoretical minimum value of Fe content) in the eutectic Al-Si-Fe-(Mn/Cr) alloys were determined experimentally for the first time, which decreased and increased slightly after the addition of Mn and Cr, respectively. After removing Fe, the residual Fe-containing impurities in the low-Fe eutectic Al-Si-Fe-(Mn/Cr) alloy were modified from their harmful needle-like shape to less harmful Chinese-script-like, and short platelet-like shapes by adding small amounts of Mn and Cr, respectively. After grinding the agglomerated Si crystals and leaching the main impurities, namely Mn, B, Cr , Ca, Al, P, Fe, and Ni, from the Si powders, the purity of Si was upgraded from 99.34% to 99.96%. This new and promising approach can be used for the purifying Si, recycling Si wafers and Al-Si scraps. [ABSTRACT FROM AUTHOR]

Sb 2 Se 3 is an emerging photovoltaic material. The non-radiative recombination loss at the surface and interface is one of the important reasons limiting the performance of Sb 2 Se 3 solar cells. In this paper, an ultra-thin layer of AlO x was used to physically and chemically passivate the ITO/Sb 2 Se 3 interface. The fixed negative charge in the AlO x layer created an electric field, which can block the diffusion of electrons from Sb 2 Se 3 to the ITO anode, and thus suppress the recombination near the anode. Moreover, the AlO x layer inhibited the chemical reaction between ITO and Sb 2 Se 3 , and thereby reduced the interfacial state. The open-circuit voltage (V oc) was improved from 0.32 V to 0.37 V and the power conversion efficiency (PCE) was enhanced from 3.37 % to 4.33 % by introducing an ultra-thin layer of AlO x. The AlO x layer was prepared by the thermal oxidation of aluminum film deposited by the vacuum evaporation. Sb 2 Se 3 solar cells were prepared by conventional vacuum evaporation. Our study provides a new method for interfacial passivation of Sb 2 Se 3 solar cells. [Display omitted] • An ultra-thin layer of AlO x was used to passivate the ITO/Sb 2 Se 3 interface in the Sb 2 Se 3 solar cell. • The AlOx layer was prepared by the thermal oxidation of aluminum film deposited by the vacuum evaporation. • The power conversion efficiency was enhanced from 3.37 % to 4.33 % by introducing an ultra-thin layer of AlOx. [ABSTRACT FROM AUTHOR]

Impurity removal, the purification process from metallurgical grade silicon (MG-Si) required to obtain solar grade silicon (SoG-Si), is crucial to the preparation of silicon-based solar cells. Some processes for boron removal by metallurgical method were reviewed. Secondary refining techniques, including gas blowing, slag treatment, plasma refining, solvent refining and other refining silicon techniques were summarized. The effects of gas species and slag systems on boron removal efficiency were emphatically discussed. Experimental and theoretical investigations show that a united technique of combining water vapor and oxygen gases blowing with slag treatment containing chloride or fluoride has achieved an amazing improvement for boron removal from molten silicon. Plasma refining and solvent refining also display high efficiency but acid leaching treatments, vacuum volatilization, electron beam and directional solidifications are hardly effective to boron removal. As for the potential industrial application of this united technique, the authors propose that some experimental and theoretical studies in dynamics should be further explored. [ABSTRACT FROM AUTHOR]

The depressing texturation and stubborn directional saw marks on diamond wire sawing (DWS) polysilicon wafers has resulted in severe limitations for the mass application of DWS technology in PV market. Herein, a simple and low-cost copper-assisted chemical etching method was presented to controllably nano-texturing DWS polysilicon wafers. The work firstly reveals the adjustment of anion species in copper salts can readily control the nanostructure during the copper-catalyzed etching process. After etching, the obtained inverted pyramid structure can effectively reduce the reflectivity of the silicon wafer surface, the reflectance can be as low as 5.8% in the wavelength range of 300–1100 nm. Moreover, the surface saw marks are removed after etching, and the novel texture method guarantee the low recombination rates. The effective texturing method shows a promising potential application in the photovoltaic field. [ABSTRACT FROM AUTHOR]

To explore the potential of acid leaching in purification metallurgical grade silicon (MG-Si) for solar cells, the effect of acetic acid on the leaching behavior was investigated in the present work by focusing on the behavior of impurities affected by the addition of acetic acid to a conventional acid mixture composed of hydrochloric acid and hydrofluoric acid. The etching results reveal that the HCl–HF–CH3COOH mixture is a better lixiviant for dissolving impurity inclusions in MG-Si. The extraction yield of impurities in HCl–HF–CH3COOH leaching was found to increase by 7% compared to conventional HCl–HF leaching. [ABSTRACT FROM PUBLISHER]

A simple and low cost MACE method was demonstrated for efficiently texturing commercial mc-Si wafer at room temperature. The effects of fabrication parameters (deposition time, HF concentration, H 2 O 2 concentration, and etching time) on the morphology structure, antireflection property of textured mc-Si were carefully studied. The large scale SiNWs arrays with different structure can be obtained under various fabrication conditions. Meanwhile, the results indicate that the fabricate parameters have important effect on the reflectance of textured mc-Si sample in the order of etching time > deposition time > H 2 O 2 concentration > HF concentration. The comprehensive research results indicate that it is more beneficial for the nanowire arrays with tapering structure and the length of 13 μm to obtain excellent antireflection property. Under these optimization conditions, the textured mc-Si shows an outstanding anti-reflectance ability of ∼5.6%, which indicates that the Ag-catalysis etched mc-Si shows a huge potential application in high-efficiency polysilicon solar cells. [ABSTRACT FROM AUTHOR]

The installed capacity of solar photovoltaic power generation has grown rapidly in the last decades. With the rapid development of the photovoltaic industry, the demand for Si wafers, which are integral to solar cells, has grown dramatically. In the manufacture of Si wafers, the traditional loose abrasive sawing method (LAS) has gradually been replaced by the diamond-wire sawing method (DWS). However, during the diamond-wire wafer sawing process, approximately 35%−40% of the crystalline Si becomes diamond-wire sawing silicon waste (DSSW). Therefore, DSSW represents a resource worth recycling due to its low levels of impurities and high silicon content. Furthermore, recycling prevents DSSW from becoming environmental pollution and eliminates disposal costs. This review provides an overview of the recycling and reutilization of DSSW based on an extensive literature survey. In view of the rapid increase in DSSW production and current purification bottleneck of < 5 N, in-situ utilizations may be more feasible, such as the preparation of silicon containing alloys and functional ceramic materials, which not only frees from the complex purification process, but has a huge demand. Finally, based on the review, future prospects are proposed, aiming to identify research directions with significant potential in the resource utilization of DSSW and other silicon wastes. [Display omitted] ● DSSW with high silicon content represents a resource worth recovery and recycling. ● The proper purification process is a trade-off between cost and purity. ● In-situ utilizations of DSSW may be more feasible strategies. ● Modification facilitates real application of DSSW in lithium-ion batteries. ● DSSW has scalable applications in energy conversion and environmental catalysis. [ABSTRACT FROM AUTHOR]

The installed capacity of solar photovoltaic power generation has grown rapidly in the last decades. With the rapid development of the photovoltaic industry, the demand for Si wafers, which are integral to solar cells, has grown dramatically. In the manufacture of Si wafers, the traditional loose abrasive sawing method (LAS) has gradually been replaced by the diamond-wire sawing method (DWS). However, during the diamond-wire wafer sawing process, approximately 35%−40% of the crystalline Si becomes diamond-wire sawing silicon waste (DSSW). Therefore, DSSW represents a resource worth recycling due to its low levels of impurities and high silicon content. Furthermore, recycling prevents DSSW from becoming environmental pollution and eliminates disposal costs. This review provides an overview of the recycling and reutilization of DSSW based on an extensive literature survey. In view of the rapid increase in DSSW production and current purification bottleneck of < 5 N, in-situ utilizations may be more feasible, such as the preparation of silicon containing alloys and functional ceramic materials, which not only frees from the complex purification process, but has a huge demand. Finally, based on the review, future prospects are proposed, aiming to identify research directions with significant potential in the resource utilization of DSSW and other silicon wastes. [Display omitted] ● DSSW with high silicon content represents a resource worth recovery and recycling. ● The proper purification process is a trade-off between cost and purity. ● In-situ utilizations of DSSW may be more feasible strategies. ● Modification facilitates real application of DSSW in lithium-ion batteries. ● DSSW has scalable applications in energy conversion and environmental catalysis. [ABSTRACT FROM AUTHOR]