Abstract: Methods of fabricating metal wrap through solar cells and modules for thin silicon solar cells, including epitaxial silicon solar cells, are described. These metal wrap through solar cells have a planar back contact geometry for the base and emitter contacts. Fabrication of a metal wrap through solar cell may comprise: providing a photovoltaic device attached at the emitter side of the device to a solar glass by an encapsulant, the device including busbars on the device emitter; forming vias through the device base and emitter, the vias terminating in the busbars; depositing a conformal dielectric film over the surface of the vias and the back surface of the base; removing portions of the conformal dielectric film from the ends of the vias for exposing the busbars and from field areas of the base; and forming separate electrical contacts to the busbars and the field areas on the back surface of the solar cell.

Abstract: Passivated emitter rear local epitaxy (PERL-e) thin Si solar cells may be formed with a heavily doped epitaxial back surface field (BSF) layer, which is patterned to form well spaced point contacts to the silicon base on the rear of the solar cell. The back side of the cell may be finished with a dielectric passivation layer and a metallization layer for making electrical contact to the cell. PERL-e thick Si solar cells may be formed with heavily doped epitaxial films as the back point contacts, where the point contacts are defined by the provision of a selectively patterned thermal oxide on the rear wafer surface. Furthermore, absorption of longer wavelength, infrared (IR), light in thin silicon solar cells may be improved by the addition of a dielectric stack on the rear surface of the solar cell (a back reflector), the stack acting to reflect the longer wavelength light back through the active layers of the solar cell.

Abstract: High efficiency silicon solar cells, including IBC cells, may be formed from lightly doped p-n sandwich structures fabricated in-situ by epitaxial growth. For example, the solar cell may comprise: an n-type silicon layer greater than or equal to 20 microns thick, with a dopant concentration between 1E15/cm3 and 5E16/cm3 and a bulk silicon carrier lifetime greater than 50 microseconds; a p-type silicon layer greater than 10 microns thick, with a dopant concentration between 1E16/cm3 and 5E18/cm3, and a bulk silicon carrier lifetime greater than 10 microseconds; wherein the n-type and p-type silicon layers were fabricated by epitaxial deposition, one after the other, on a reusable single crystal silicon substrate. The ideality factor of the silicon solar cell may be approximately 1.0. The epitaxial deposition may be in a reactor with low auto-doping and low oxygen incorporation.

Abstract: An anodic etching system for simultaneously etching a multiplicity of substrates comprises: an etching tank for containing therein an etchant solution; a power supply connected between a first electrode and a second electrode, the first electrode and the second electrode being immersible in the etchant solution and positioned at opposite ends of the tank; and a plurality of support plates serially arranged between the first electrode and the second electrode and sealed to walls of the tank, wherein each of the plurality of support plates is configured to support at least one of the multiplicity of substrates, and wherein any consecutive pair of the plurality of support plates defines an isolated volume of the tank for containing a portion of the etchant solution. The plurality of support plates may be susceptors configured for holding the multiplicity of substrates in a chemical vapor deposition tool.

Abstract: A solar cell comprises an optically transparent handle, wherein the handle includes grooves into which tabs are inserted, enabling the use of high aspect ratio tabs with minimal shading of the front side of the solar cell. Electrical connection of the tabs to busbars on the surface of the layers of the solar cell is through apertures at the bottom of each groove on the handle—the grooves being aligned to the busbars. The apertures may be filled with solder, metal pins, metal spheres, etc, and in embodiments the tabs may be metal wires. The solar cells with optically transparent handles may be formed into solar cell modules. Furthermore, in embodiments the handle with integral tabs simplifies and reduces the cost of solar cell and module fabrication since the top surface of the transparent handle including tabs may be completely flat.

Abstract: Methods of fabricating metal wrap through solar cells and modules for thin silicon solar cells, including epitaxial silicon solar cells, are described. These metal wrap through solar cells have a planar back contact geometry for the base and emitter contacts. Fabrication of a metal wrap through solar cell may comprise: providing a photovoltaic device attached at the emitter side of the device to a solar glass by an encapsulant, the device including busbars on the device emitter; forming vias through the device base and emitter, the vias terminating in the busbars; depositing a conformal dielectric film over the surface of the vias and the back surface of the base; removing portions of the conformal dielectric film from the ends of the vias for exposing the busbars and from field areas of the base; and forming separate electrical contacts to the busbars and the field areas on the back surface of the solar cell.

Abstract: An epitaxial reactor enabling simultaneous deposition of thin films on a multiplicity of wafers is disclosed. During deposition, a number of wafers are contained within a wafer sleeve comprising a number of wafer carrier plates spaced closely apart to minimize the process volume. Process gases flow preferentially into the interior volume of the wafer sleeve, which is heated by one or more lamp modules. Purge gases flow outside the wafer sleeve within a reactor chamber to minimize deposition on the chamber walls. Sequencing of the illumination of the individual lamps in the lamp module may further improve the linearity of variation in deposition rates within the wafer sleeve. To improve uniformity, the direction of process gas flow may be varied in a cross-flow configuration. Combining lamp sequencing with cross-flow processing in a multiple reactor system enables high throughput deposition with good film uniformities and efficient use of process gases.

Abstract: An epitaxial reactor enabling simultaneous deposition of thin films on a multiplicity of wafers is disclosed. During deposition, a number of wafers are contained within a wafer sleeve comprising a number of wafer carrier plates spaced closely apart to minimize the process volume. Process gases flow preferentially into the interior volume of the wafer sleeve, which is heated by one or more lamp modules. Purge gases flow outside the wafer sleeve within a reactor chamber to minimize wall deposition. In addition, sequencing of the illumination of the individual lamps in the lamp module may further improve the linearity of variation in deposition rates within the wafer sleeve. To improve uniformity, the direction of process gas flow may be varied in a cross-flow configuration. Combining lamp sequencing with cross-flow processing in a multiple reactor system enables high throughput deposition with good film uniformities and efficient use of process gases.

Abstract: Passivated emitter rear local epitaxy (PERL-e) thin Si solar cells may be formed with a heavily doped epitaxial back surface field (BSF) layer, which is patterned to form well spaced point contacts to the silicon base on the rear of the solar cell. The back side of the cell may be finished with a dielectric passivation layer and a metallization layer for making electrical contact to the cell. PERL-e thick Si solar cells may be formed with heavily doped epitaxial films as the back point contacts, where the point contacts are defined by the provision of a selectively patterned thermal oxide on the rear wafer surface. Furthermore, absorption of longer wavelength, infrared (IR), light in thin silicon solar cells may be improved by the addition of a dielectric stack on the rear surface of the solar cell (a back reflector).

Abstract: Fabrication of a single crystal silicon solar cell with an insitu epitaxially deposited very highly doped p-type silicon back surface field obviates the need for the conventional aluminum screen printing step, thus enabling a thinner silicon solar cell because of no aluminum induced bow in the cell. Furthermore, fabrication of a single crystal silicon solar cell with insitu epitaxial p-n junction formation and very highly doped n-type silicon front surface field completely avoids the conventional dopant diffusion step and one screen printing step, thus enabling a cheaper manufacturing process.

Abstract: An epitaxial reactor enabling simultaneous deposition of thin films on a multiplicity of wafers is disclosed. During deposition, a number of wafers are contained within a wafer sleeve comprising a number of wafer carrier plates spaced closely apart to minimize the process volume. Process gases flow preferentially into the interior volume of the wafer sleeve, which is heated by one or more lamp modules. Purge gases flow outside the wafer sleeve within a reactor chamber to minimize deposition on the walls of the chamber. In addition, sequencing of the illumination of the individual lamps in the lamp module may further improve the linearity of variation in deposition rates within the wafer sleeve. To improve uniformity, the direction of process gas flow may be varied in a cross-flow configuration. Combining lamp sequencing with cross-flow processing in a multiple reactor system enables high throughput deposition with good film uniformities and efficient use of process gases.

Abstract: An epitaxial reactor enabling simultaneous deposition of thin films on a multiplicity of wafers is disclosed. During deposition, a number of wafers are contained within a wafer sleeve comprising a number of wafer carrier plates spaced closely apart to minimize the process volume. Process gases flow preferentially into the interior volume of the wafer sleeve, which is heated by one or more lamp modules. Purge gases flow outside the wafer sleeve within a reactor chamber to minimize wall deposition. In addition, sequencing of the illumination of the individual lamps in the lamp module may further improve the linearity of variation in deposition rates within the wafer sleeve. To improve uniformity, the direction of process gas flow may be varied in a cross-flow configuration. Combining lamp sequencing with cross-flow processing in a multiple reactor system enables high throughput deposition with good film uniformities and efficient use of process gases.

Abstract: A solar cell may comprise a stack of thin continuous epitaxial single crystal solar cell layers on a single crystal wafer, and a handling layer on the stack, the handling layer having a waffle-shaped structure with an array of either square or circular apertures, wherein the handling layer includes electrical contacts to the stack. The solar cell may comprise a boundary layer between the stack and the handling layer, the boundary layer being attached to both the stack and the handling layer, and the boundary layer being greater than 10 nanometers thick and parallel to the layers in the stack. The waffle-shaped structure may include perpendicular sets of first and second parallel ridges, wherein at least one of the sets is aligned at a small angle to a cleavage plane of the single crystal wafer.

Abstract: Fabrication of a single crystal silicon solar cell with an insitu epitaxially deposited very highly doped p-type silicon back surface field obviates the need for the conventional aluminum screen printing step, thus enabling a thinner silicon solar cell because of no aluminum induced bow in the cell. Furthermore, fabrication of a single crystal silicon solar cell with insitu epitaxial p-n junction formation and very highly doped n-type silicon front surface field completely avoids the conventional dopant diffusion step and one screen printing step, thus enabling a cheaper manufacturing process.

Abstract: A method for fabricating a photovoltaic (PV) cell panel wherein all PV cells are formed simultaneously on a two-dimensional array of monocrystalline silicon mother wafers affixed to a susceptor is disclosed. Porous silicon separation layers are anodized in the surfaces of the mother wafers. The porous film is then smoothed to form a suitable surface for epitaxial film growth. An epitaxial reactor is used to grow n- and p-type films forming the PV cell structures. A glass/ceramic handling layer is then formed on the PV cell structures. The PV cell structures with handling layers are then exfoliated from the mother wafer. The array of mother wafers may be reused multiple times, thereby reducing materials costs for the completed solar panels. The glass/ceramic handling layers provide structural integrity to the thin epitaxial solar cells during the separation process and subsequent handling.

Abstract: Photovoltaic modules including a plurality of solar cells bonded to a module back sheet are described herein, wherein each solar cell includes a superstrate bonded to a front side of a photovoltaic device to facilitate handling of very thin photovoltaic devices during fabrication of the module. Modules may also include module front sheets and the solar cells may include bottom sheets. The modules may be made of flexible materials, and may be foldable. Fabrication processes include tabbing photovoltaic devices prior to attaching the individual superstrates.

Abstract: A system for depositing thin single crystal silicon wafers by epitaxial deposition in a silicon precursor depletion mode with cross-flow deposition may include: a substrate carrier with low total heat capacity, high emissivity and small volume; a lamp module with rapid heat-up, efficient heat production, and spatial control over heating; and a manifold designed for cross-flow processing. Furthermore, the substrate carrier may include heat reflectors to control heat loss from the edges of the carrier and/or heat chokes to thermally isolate the carrier from the manifolds, allowing independent temperature control of the manifolds. The carrier and substrates may be configured for deposition on both sides of the substrates—the substrates having release layers on both sides and the carriers being configured to have equal process gas flow over both surfaces of the substrate. High volume may be addressed by a deposition system comprising multiple mini-batch reactors.

Abstract: Fabrication of a single crystal silicon solar cell with an insitu epitaxially deposited very highly doped p-type silicon back surface field obviates the need for the conventional aluminum screen printing step, thus enabling a thinner silicon solar cell because of no aluminum induced bow in the cell. Furthermore, fabrication of a single crystal silicon solar cell with insitu epitaxial p-n junction formation and very highly doped n-type silicon front surface field completely avoids the conventional dopant diffusion step and one screen printing step, thus enabling a cheaper manufacturing process.

Abstract: An epitaxial reactor enabling simultaneous deposition of thin films on a multiplicity of wafers is disclosed. During deposition, a number of wafers are contained within a wafer sleeve comprising a number of wafer carrier plates spaced closely apart to minimize the process volume. Process gases flow preferentially into the interior volume of the wafer sleeve, which is heated by one or more lamp modules. Purge gases flow outside the wafer sleeve within a reactor chamber to minimize wall deposition. In addition, sequencing of the illumination of the individual lamps in the lamp module may further improve the linearity of variation in deposition rates within the wafer sleeve. To improve uniformity, the direction of process gas flow may be varied in a cross-flow configuration. Combining lamp sequencing with cross-flow processing in a multiple reactor system enables high throughput deposition with good film uniformities and efficient use of process gases.

Abstract: Methods of fabricating metal wrap through solar cells and modules for thin silicon solar cells, including epitaxial silicon solar cells, are described. These metal wrap through solar cells have a planar back contact geometry for the base and emitter contacts. Fabrication of a metal wrap through solar cell may comprise: providing a photovoltaic device attached at the emitter side of the device to a solar glass by an encapsulant, the device including busbars on the device emitter; forming vias through the device base and emitter, the vias terminating in the busbars; depositing a conformal dielectric film over the surface of the vias and the back surface of the base; removing portions of the conformal dielectric film from the ends of the vias for exposing the busbars and from field areas of the base; and forming separate electrical contacts to the busbars and the field areas on the back surface of the solar cell.