Calisolar Inc.

Other

Silicor Materials Inc.

Dieter Linke

Kamel Ounadjela

Fritz Kirscht

Matthias Heuer

Vera Abrosimova

Jean Patrice Rakotoniana

Jean Patrice Rakotoniaina

Martin Kaes

Anis Jouini

Techniques for the formation of a silicon ingot using a low-grade silicon feedstock include forming within a crucible device a molten silicon from a low-grade silicon feedstock and performing a directional solidification of the molten silicon to form a silicon ingot within the crucible device. The directional solidification forms a generally solidified quantity of silicon and a generally molten quantity of silicon. The method and system include removing from the crucible device at least a portion of the generally molten quantity of silicon while retaining within the crucible device the generally solidified quantity of silicon. Controlling the directional solidification of the generally solidified quantity of silicon, while removing the more contaminated molten silicon, results in a silicon ingot possessing a generally higher grade of silicon than the low-grade silicon feedstock.

Method and system for forming a silicon ingot using a low-grade silicon feedstock

Techniques are here disclosed for a solar cell pre-processing method and system for annealing and gettering a solar cell semiconductor wafer having an undesirably high dispersion of transition metals, impurities and other defects. The process forms a surface contaminant layer on the solar cell semiconductor (e.g., silicon) wafer. A surface of the semiconductor wafer receives and holds impurities, as does the surface contaminant layer. The lower-quality semiconductor wafer includes dispersed defects that in an annealing process getter from the semiconductor bulk to form impurity cluster toward the surface contaminant layer. The impurity clusters form within the surface contaminant layer while increasing the purity level in wafer regions from which the dispersed defects gettered. Cooling follows annealing for retaining the impurity clusters and, thereby, maintaining the increased purity level of the semiconductor wafer in regions from which the impurities gettered. Multicrystalline semiconductor wafers having grain boundaries with impurities may also undergo the annealing and gettering of dispersed defects to the grain boundaries, further increasing the semiconductor substrate purity levels.

Semiconductor wafer pre-process annealing and gettering method and system for solar cell formation

Techniques for the formation of silicon ingots and crystals using silicon feedstock of various grades are described. Common feature is adding a predetermined amount of germanium to the melt and performing a crystallization to incorporate germanium into the silicon lattice of respective crystalline silicon materials. Such incorporated germanium results in improvements of respective silicon material characteristics, mainly increased material strength. This leads to positive effects at applying such materials in solar cell manufacturing and at making modules from those solar cells. A silicon material with a germanium concentration in the range (50-200) ppmw demonstrates an increased material strength, where best practical ranges depend on the material quality generated.

Germanium-enriched silicon material for making solar cells

Techniques for controlling resistivity in the formation of a silicon ingot from compensated feedstock silicon material prepares a compensated, upgraded metallurgical silicon feedstock for being melted to form a silicon melt. The compensated, upgraded metallurgical silicon feedstock provides a predominantly p-type semiconductor for which the process assesses the concentrations of boron and phosphorus and adds a predetermined amount of aluminum or/and gallium. The process further melts the silicon feedstock together with a predetermined amount of aluminum or/and gallium to form a molten silicon solution from which to perform directional solidification and, by virtue of adding aluminum or/and gallium, maintains the homogeneity the resistivity of the silicon ingot throughout the silicon ingot. In the case of feedstock silicon leading to low resistivity in respective ingots, typically below 0.4 &#x3a9;cm, a balanced amount of phosphorus can be optionally added to aluminum or/and gallium. Adding phosphorus becomes mandatory at very low resistivity, typically close to 0.2 &#x3a9;cm and slightly below.

Method and system for controlling resistivity in ingots made of compensated feedstock silicon

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Berlin, Germany

Dieter Linke