Abstract: A simplified manufacturing process and the resultant bifacial solar cell (BSC) are provided, the simplified manufacturing process reducing manufacturing costs. The BSC includes a back surface contact grid and an overlaid blanket metal reflector. A doped amorphous silicon layer is interposed between the contact grid and the blanket layer.
Type:
Application
Filed:
June 15, 2009
Publication date:
November 4, 2010
Applicant:
Calisolar, Inc.
Inventors:
Martin Kaes, Peter Borden, Kamel Ounadjela, Andreas Kraenzl, Alain Blosse, Fritz G. Kirscht
Abstract: 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 semiconductor predominantly of a single type (p-type or n-type) for which the process assesses the concentrations of boron and phosphorus and adds a predetermined amount of boron, phosphorus, aluminum and/or gallium. The process further melts the silicon feedstock with the boron, phosphorus, aluminum and/or gallium to form a molten silicon solution from which to perform directional solidification and maintains the homogeneity of the resistivity of the silicon throughout the ingot. A balanced amount of phosphorus can be optionally added to the aluminum and/or gallium. Resistivity may also be measured repeatedly during ingot formation, and additional dopant may be added in response, either repeatedly or continuously.
Type:
Application
Filed:
November 13, 2009
Publication date:
October 14, 2010
Applicant:
CALISOLAR, INC.
Inventors:
Fritz Kirscht, Marcin Walerysiak, Matthias Heuer, Anis Jouini, Kamel Ounadjela
Abstract: 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.
Type:
Application
Filed:
June 16, 2008
Publication date:
December 17, 2009
Applicant:
CALISOLAR, INC.
Inventors:
Fritz Kirscht, Vera Abrosimova, Matthias Heuer, Anis Jouini, Dieter Linke, Martin Kaes, Jean Patrice Rakotoniaina, Kamel Ounadjela
Abstract: Formation of a solar cell device from upgraded metallurgical grade silicon which has received at least one defect engineering process and including a low contact resistance electrical path. An anti-reflective coating is formed on an emitter layer and back contacts are formed on a back surface of the bulk silicon substrate. This photovoltaic device may be fired to form a back surface field at a temperature sufficiently low to avoid reversal of previous defect engineering processes. The process further forms openings in the anti-reflective coating and a low contact resistance metal layer, such as nickel layer, over the openings in the anti-reflective coating. The process may anneal the low contact resistance metal layer to form n-doped portion and complete an electrically conduct path to the n-doped layer. This low temperature metallization (e.g., <700° C.) supports the use of UMG silicon for the solar device formation without the risk of reversing earlier defect engineering processes.
Type:
Application
Filed:
March 10, 2008
Publication date:
September 10, 2009
Applicant:
CaliSolar, Inc.
Inventors:
Kamel Ounadjela, Jean Patrice Rakotoniaina, Martin Kaes, Dirk Zickermann, Alain Blosse, Abdellatif Zerga, Matthias Heuer, Fritz Kirscht
Abstract: Techniques are here disclosed for a solar cell pre-processing. The method and system remove impurities from low-grade crystalline semiconductor wafers and include forming a low-grade semiconductor wafer having a substrate having high impurity content. The process and system damage at least one surface of the semiconductor wafer either in the semiconductor wafer forming step or in a separate step to form a region on the surface that includes a plurality of gettering centers. The gettering centers attract impurities from the substrate during subsequent processing. The subsequent processes include diffusing impurities from the substrate using a phosphorus gettering process that includes impregnating the surface with a phosphorus material for facilitating the formation of impurity clusters associated with the gettering centers.
Type:
Application
Filed:
February 16, 2007
Publication date:
August 21, 2008
Applicant:
CaliSolar, Inc.
Inventors:
Jean Patrice Rakotoniana, Matthias Heuer, Fritz Kirscht, Dieter Linke, Kamel Ounadjela