Photovoltaic Arrays, Micro-Concentrator Solar Cells and Modules and

Methods of Making

TECHNICAL FIELD

[0001] Embodiments of the present invention relate generally to solar or photovoltaic cells, assemblies and modules. More specifically, embodiments of the present invention relate to photovoltaic array and micro-concentrator solar cell assemblies comprising a plurality of photovoltaic nodes coupled by extendable interconnectors or interconnects, methods of making, and devices and modules formed therefrom.

BACKGROUND

[0002] Electric power generation from solar or photovoltaic cells has experienced significant interest over the years. Widespread adoption of solar cells for power generation however, requires further breakthroughs in both the cost and efficiency of the cells. There is a general belief that solar cells must generate electricity at costs of $1.00/watt or lower in order to compete with traditional forms of electric power generation.

[0003] Solar or photovoltaic cells and modules convert light energy (typically from the

Sun) to electrical energy, using the photovoltaic effect. Solar cells are often electrically connected and encapsulated as a photovoltaic (PV) module. The power output of a solar cell is measured in watts or kilowatts. In order to calculate the typical energy needs of the application, a measurement in watt-hours, kilowatt-hours or kilowatt-hours per day is often used. A common rule of thumb is that average power is equal to 20% of peak power, so that each peak kilowatt of solar array output power corresponds to energy production of 4.8 kWh per day.

[0004] Increasing the efficiency of solar cells is a continual challenge. One technique that has been employed is the use of concentrators. Traditional concentrators utilize large mirrors to concentrate light onto large photovoltaic modules or cells. Such systems can be mechanically complex, and all are expensive and cumbersome to install, as well as being capital intensive.

[0005] More recently, micro-concentrator solar cell systems have been investigated.

While the focus has been to miniaturize the modules and assemblies, such devices have many limitations and are still complicated and expensive to fabricate, often requiring many separate components that must be wire bonded and the like. Additionally, such assemblies are often inflexible, both in terms of mechanical design and adaptability, and are easily damaged. Increasing the power output of micro-concentrator solar cells remains a challenge. Further developments are needed.

SUMMARY

[0006] In some embodiments, a photovoltaic cell is provided comprised of a plurality of nodes, each node coupled to another node by an extendable interconnector or interconnect. At least some of the plurality of nodes are configured to collect photovoltaic energy. The term "interconnector(s)" and "interconnect(s)" are used throughout interchangeably, and such terms are used to generally refer to a connection between nodes wherein the connection is a mechanical connection, and in some embodiments is both a mechanical and electrical connection between nodes.

[0007] In an exemplary embodiment, a photovoltaic array is provided comprising: a plurality of nodes connected by extendable interconnects, said nodes being arranged in a regular, ordered arrangement, and wherein certain of the extendable interconnects are configured to provide electrical connection between certain of the nodes. The electrical connection is configured in parallel in some embodiments. Alternatively, the electrical connection is in series. In yet a further alternative embodiment and of particular advantage, the electrical connection is configured such that certain of the nodes are electrically coupled in series, and certain of the nodes are electrically coupled in parallel, or a combination thereof.

[0008] The photovoltaic array may be configured such that the plurality of nodes and extendable interconnects are formed from a monolithic substrate. In another embodiment the nodes and the extendable interconnects are formed of the same material. In some embodiments, a photovoltaic array is provided wherein at least some of the plurality of nodes are comprised of single or multiple p-n junctions. In other embodiments, at least some of the plurality of nodes are comprised of an electrical switch. In one preferred embodiment the photovoltaic array is monolithic.

[0009] Another aspect of the present invention provides a micro-concentrator solar cell assembly. In an illustrative embodiment the micro-concentrator solar cell assembly comprises a plurality of photovoltaic nodes, wherein a respective first node and second node of the plurality of photovoltaic nodes are coupled by extendable interconnects; and a sheet of material is affixed to at least the first node and the second node, wherein the sheet of material holds the first node and the second node and the extendable interconnects in an extended position.

[0010] Additionally, the micro-concentrator solar cell may further comprise a plurality of lenses, having a respective first lens and second lens coupled to the respective first node and second node.

[0011] In another aspect, a solar cell device is provided comprising a node; and at least two extendable interconnects attached to and extending from the node and coiled around at least a portion of the node at a minimum radius of curvature (R _m1n ) of:

where t is the thickness of the extendable interconnect and ε _ma χ is the maximum strain the extendable interconnects can withstand before fracture. In some embodiments, the at least two interconnects are attached to the node at positions such that no substantial torque is experienced by the device upon substantially full extension of the extendable interconnects. In some instances the node and the at least two interconnects are monolithic. In some embodiments, the node and the at least two interconnects are monolithic and comprised of silicon.

[0012] Any number of extendable interconnects may be used. In one exemplary embodiment at least four extendable interconnects are provided. In another embodiment, at least six extendable interconnects are provided.

[0013] The node may take a variety of shapes. Without limitation, in some embodiments the node is comprised of a clover leaf shape. Alternatively, the node is comprised of a rectangular shape. In yet a further embodiment the node is comprised of a hexagonal shape.

[0014] In another aspect, according to some embodiments a micro-concentrator solar cell assembly is provided, comprising: a plurality of photovoltaic nodes, wherein a respective first node and second node of the plurality of photovoltaic nodes are coupled by extendable interconnects; and a plurality of lenses coupled to the plurality of photovoltaic nodes, where a respective lens of the plurality of lenses is aligned to concentrate light on a respective node of the plurality of nodes.

[0015] In yet a further aspect, according to some embodiments a solar cell assembly, is provided comprising: a plurality of photovoltaic nodes, wherein a respective first node and second node of the plurality of photovoltaic nodes are coupled by an extendable interconnect; and a plurality of reflectors coupled to the plurality of photovoltaic nodes, where a respective reflector of the plurality of reflectors is aligned to concentrate light on a respective node of the plurality of nodes.

[0016] In other embodiments, a micro-concentrator solar cell assembly is provided, comprising: a plurality of photovoltaic nodes, wherein a respective first node and second node of the plurality of photovoltaic nodes are coupled by an extendable interconnect; a plurality of lenses coupled to a first side of the plurality of photovoltaic nodes, where a respective lens of the plurality of lenses is aligned to concentrate light onto a respective node of the plurality of nodes; and a plurality of reflectors coupled to a second side of the plurality of photovoltaic nodes, where a respective reflector of the plurality of reflectors is aligned to concentrate light on a respective node of the plurality of nodes, wherein the second side is opposite to the first side.

[0017] The first and second photovoltaic nodes may be comprised of any suitable photovoltaic material, such as without limitation: one or more of silicon, gallium arsenide, germanium, indium gallium phosphide, or a combination thereof. In some embodiments, at least one of the first and second photovoltaic nodes is comprised of a clover-leaf like shape. In some embodiments, the first and second photovoltaic nodes and the extendable interconnect are formed of the same material. In one preferred embodiment the first and second photovoltaic nodes and extendable interconnects are formed from a monolithic substrate.

[0018] A photovoltaic array comprises a plurality of nodes, wherein each node is coupled to another node by an extendable interconnect, and where at least some of the plurality of nodes are configured to collect photovoltaic energy. In some embodiments certain of the nodes are connected in parallel to accumulate their current output. Alternatively, or additionally, certain of the nodes are connected in series to accumulate their voltage output. Of particular advantage the array architecture according to embodiments of the present invention enables significant flexibility and/or adaptability such that any desired combination of parallel and series electrical connections may be selectively deployed. Additionally, output from the plurality of nodes may be taken from the outermost interconnects at or near the edge of the array, thereby streamlining the module and reducing cost and complexity.

[0019] According to some embodiments a micro-concentrator solar cell assembly comprises a plurality of photovoltaic nodes. A respective first node and second node of the plurality of photovoltaic nodes are coupled by an extendable interconnect. A sheet of material is affixed to at least the first node and the second node. The sheet of material holds the first node and the second node and the extendable interface in an extended position. In some embodiments, the material is a transparent material. In some embodiments, the transparent material further comprises a plurality of lenses, and a respective first lens and second lens of the plurality of lenses are aligned relative to the respective first node and second node.

[0020] The plurality of lenses may be formed in the transparent material. In some embodiments, the transparent material is coupled on a first side of the respective first node and second node, and a reflective material is coupled to a second side of the respective first node and second node opposite to the first side. A plurality of reflectors may be formed in the reflective material. In some embodiments, the sheet of material is aluminum and the aluminum is affixed by an adhesive to at least the first node and the second node and the extendable interconnect.

[0021] According to additional aspects of the present invention, a micro-concentrator solar cell is provided comprising a plurality of photovoltaic nodes, wherein a respective first node and second node of the plurality of photovoltaic nodes are coupled by an extendable interconnect. A plurality of lenses are coupled to the plurality of photovoltaic nodes, where a respective lens of the plurality of lenses is aligned to concentrate light on a respective node of the plurality of nodes.

[0022] In some embodiments, a sheet of material is affixed to at least the first node and the second node, wherein the sheet of material holds the first node and the second node and the extendable interconnects in an extended position. In some embodiments, the sheet of material is configurable to align the first node and the second node with a respective first and second lens of the plurality of lenses. In some embodiments, the material is a transparent material. The plurality of lenses may be formed in the sheet of transparent material. In some embodiments, the transparent material is coupled on a first side of the respective first node and second node, and a reflective material is coupled to a second side of the respective first node and second node. In some embodiments, a plurality of reflectors are formed in the reflective material. In one particular example, the sheet of material is aluminum and the aluminum is affixed by an adhesive to at least the first node and the second node.

[0023] The plurality of lenses may be comprised of any lens useful for concentrating solar energy. For example, without limitation, at least one of the plurality of lenses may be any one or more of: a concave lens, convex lens, parabolic lens, aspheric lens, Fresnel lens, droplet shaped lens, and the like.

[0024] In another aspect embodiments provide a micro-concentrator solar cell comprising a plurality of photovoltaic nodes, wherein a respective first node and second node of the plurality of photovoltaic nodes are coupled by an extendable interconnect. A plurality of reflectors is coupled to the plurality of photovoltaic nodes, where a respective reflector of the plurality of reflectors is aligned to concentrate light on a respective node of the plurality of nodes.

[0025] In some embodiments, a sheet of material is affixed to at least the first node and the second node. The sheet of material may hold the first node and the second node and the extendable interconnects in an extended position. In some embodiments, the sheet of material is configurable to align the first node and the second node with a reflector and a second reflector of the plurality of reflectors. In some embodiments, the sheet of material is a sheet of reflective material. In some embodiments, the respective reflector of the plurality of reflectors is formed in the sheet of reflective material. In one example, the sheet of material is aluminum and the aluminum is affixed by an adhesive to the respective reflector.

[0026] The plurality of reflectors is comprised of any reflector useful for concentrating solar energy. For example, without limitation, at least one of the plurality of reflectors may be any one or more of: a concave reflector, parabolic reflector, aspheric reflector, diffractive reflector, zone plate, and the like.

[0027] Additionally, some embodiments of the present invention provide a micro- concentrator solar cell assembly or module comprising a plurality of photovoltaic nodes, wherein a respective first node and second node of the plurality of photovoltaic nodes are coupled by an extendable interconnect, and coupled to each of the nodes is at least one of a lenses or reflector. In some embodiments, a plurality of lenses is coupled to a first side of the plurality of photovoltaic nodes, where a respective lens of the plurality of lenses is aligned to concentrate light onto a respective node of the plurality of nodes, and a plurality of reflectors is coupled to a second side of the plurality of photovoltaic nodes, where a respective reflector of the plurality of reflectors is aligned to concentrate light on a respective node of the plurality of nodes, and wherein the second side is opposite to the first side.

[0028] In some embodiments, a sheet of material is affixed to at least the first node and the second node, wherein the sheet of material holds the first node and the second node and the extendable interconnect in an extended position. A gap between the plurality of lenses and the plurality of reflectors may be provided. The gap may be filled with a medium. In some embodiments, the gap is filled with air. [0029] In another aspect of the present invention, methods of forming photovoltaic arrays are provided. According to some embodiments, a method of stretching nodes to form an array of nodes is provided, comprising the steps of: locating a respective first node and a respective second node of a plurality of photovoltaic nodes, wherein the first node and second node are coupled by coiled extendable interconnects; placing a first pin or probe on the first node and placing a second pin or probe on the second node; and moving the first pin and second pin apart while retaining contact with the respective first node and second node. In an alternative embodiment, the method of stretching nodes includes engaging two or more tabs instead of the nodes, and moving pins apart while retaining contact with the respective tabs. Tabs may be formed integral to an array of nodes, such as but not necessarily at two or more corners of the array.

[0030] In some embodiments, a lamination sheet is applied to at least a portion of the plurality of nodes and the extendable interconnect. In some embodiments, the lamination sheet fixes the relative position of the portion of the plurality of nodes and to the extendable interconnect. In some embodiments, the first pin and the second pin are removed from the nodes.

[0031] In some embodiments, a locating step is performed to locate the respective first node and the respective second node on a wafer chuck. In some embodiments, the plurality of nodes and the extendable interconnect are temporarily held to the wafer chuck by an electrostatic force.

[0032] Other methods are provided herein. In one exemplary embodiment, a method of making a photovoltaic node and an extendable interconnect is provided, comprising the steps of: fabricating a respective first node and a respective second node of a plurality of photovoltaic nodes on a wafer, wherein the first node and second node are coupled by a coiled or folded interconnect; performing anisotropic etch between portions of the coiled interconnect; and releasing the plurality of nodes and interconnect from the wafer.

[0033] In some embodiments, fabricating the plurality of photovoltaic nodes further comprises forming a p-type junction and an n-type junction, and forming contacts coupled to the p-type junction and the n-type junction respectively, for each node of the plurality of photovoltaic nodes on the wafer. In other embodiments, methods further comprise performing the anisotropic etch to remove portions of the wafer between portions of the coiled interconnect, and wherein releasing the plurality of nodes and interconnect mechanically separates the portions of the coiled interconnect.

[0034] A method of making a photovoltaic node and an extendable interconnect comprises fabricating a respective first node and a respective second node of a plurality of photovoltaic nodes on a wafer. The first node and second node are coupled by a coiled or folded interconnect. An anisotropic ion etch, such as but not limited to deep reactive ion etch, is performed between portions of the coiled interconnect. The plurality of nodes and interconnect are then released from the wafer.

[0035] In some embodiments, fabricating the plurality of photovoltaic nodes further comprises forming a p-type junction and an n-type junction, and forming contacts coupled to the p-type junction and the n-type junction respectively, for each node of the plurality of photovoltaic nodes on the wafer.

[0036] The inventors have discovered that embodiments of the present invention enable devices of particular advantage. In one example, a "smart window" is provided. In some embodiments, a smart window is comprised of a photovoltaic array formed in said window, said array comprising a plurality of nodes connected by extendable interconnects, said nodes being arranged in a regular, ordered arrangement, and wherein certain of the extendable interconnects are configured to provide electrical connection between certain of the nodes.

[0037] In another example of a device enabled by the present innovation, some embodiments provide a photovoltaic array, said array being affixed to a building surface and further comprising: a plurality of nodes connected by extendable interconnects, said nodes being arranged in a regular, ordered arrangement, and wherein certain of the extendable interconnects are configured to provide electrical connection between certain of the nodes.

[0038] In another aspect a system is provided, comprising: one or more processors; memory; and one or more programs stored in the memory, the one or more programs comprising instructions to: locate a respective first node and a respective second node of a plurality of photovoltaic nodes, wherein the first node and second node are coupled by coiled extendable interconnects; place a first pin on the first node and placing a second pin on the second node; and move the first pin and second pin apart while retaining contact with the respective first node and second node.

[0039] In yet a further aspect computer readable storage medium is provided. For example, in an illustrative embodiment, a computer readable storage medium storing one or more programs configured for execution by a computer is provided, the one or more programs comprising instructions to: locate a respective first node and a respective second node of a plurality of photovoltaic nodes, wherein the first node and second node are coupled by coiled extendable interconnects; place a first pin on the first node and placing a second pin on the second node; and move the first pin and second pin apart while retaining contact with the respective first node and second node.

[0040] In another embodiment a computer readable storage medium storing one or more programs configured for execution by a computer is provided, the one or more programs comprising instructions to: fabricate a respective first node and a respective second node of a plurality of photovoltaic nodes on a wafer, wherein the first node and second node are coupled by a coiled or folded interconnect; perform anisotropic etch between portions of the coiled interconnect; and release the plurality of nodes and interconnects from the wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The foregoing and other aspects of the present invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which:

[0042] Figures IA and IB illustrate top views of a plurality of nodes with extendable interconnects, shown a coiled position and in an extended position, respectively, according to some embodiments of the present invention;

[0043] Figure 1C is a schematic diagram illustrating an exemplary sequence of steps used to determine the geometry of a particular node according to some embodiments of the present invention;

[0044] Figure 2 depicts a cross sectional view of a portion of a micro-concentrator solar cell assembly having plurality of reflectors according to some embodiments of the present invention;

[0045] Figure 3 illustrates a cross sectional view of a portion of a micro-concentrator solar cell assembly having a plurality of concentrator lenses according to some embodiments of the present invention;

[0046] Figures 4A and 4B show cross sectional views of a portion of a micro- concentrator solar cell assembly having a reflector and a concentrator lens, respectively, according to some embodiments of the present invention; [0047] Figures 5A - 5D illustrate process sequences for manufacturing a micro- concentrator solar cell assembly having a photovoltaic array made of extendable silicon interconnects according to some embodiments of the present invention;

[0048] Figure 6 is a diagram illustrating an exemplary probe station for extending or stretching a plurality of nodes and extendable interconnects to form a photovoltaic array according to some embodiments of the present invention;

[0049] Figure 7 is a diagram showing pins or probes of the probe station in Figure 6, according to some embodiments of the present invention;

[0050] Figure 8A is a SEM photograph showing pin tips touching photovoltaic nodes, used to extend the coiled interconnects between the nodes to form a photovoltaic array according to some embodiments of the present invention;

[0051] Figure 8B is a schematic illustration of one exemplary node geometry according to some embodiments of the present invention;

[0052] Figure 9A is a SEM photograph showing an array of photovoltaic nodes in an extended position, with extended interconnects between the nodes according to some embodiments of the present invention;

[0053] Figure 9B is a schematic illustration of one exemplary node geometry in an extended position according to some embodiments of the present invention;

[0054] Figure 10 is a flowchart depicting steps for manufacturing a micro-concentrator solar cell assembly according to some embodiments of the present invention;

[0055] Figure 11 illustrates process steps for manufacturing a photovoltaic node and extendable interconnects according to some embodiments of the present invention;

[0056] Figures 12 - 15 show process sequence steps for manufacturing a micro- concentrator solar cell assembly according to some embodiments of the present invention;

[0057] Figure 16 illustrates process sequence steps for attaching a lens to a photovoltaic node according to some embodiments of the present invention;

[0058] Figure 17 depicts a process sequence showing a non-release flow, according to some embodiments of the present invention;

[0059] Figure 18 shows a cross sectional view of a portion of a photovoltaic array having a plurality of optical reflectors according to some embodiments of the present invention; [0060] Figure 19 illustrates a system for manufacturing a photovoltaic array and micro- concentrator solar cell assembly according to some embodiments of the present invention;

[0061] Figures 2OA and 2OB illustrate a flowchart of a method for fabricating a micro- concentrator solar cell assembly having a photovoltaic array according to some embodiments of the present invention;

[0062] Figures 21 A and 2 IB are SEM photographs illustrating a top view of an array or network of nodes with extendable interconnects according to some embodiments of the present invention; and

[0063] Figures 22A and 22B are exemplary SEM photographs showing a top view of a single node with extendable interconnects in a coiled and extended position, respectively, according to some embodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0064] In general, embodiments of the present invention relate to solar or photovoltaic cells, assemblies and modules. Embodiments of the present invention relate to photovoltaic array, micro-concentrator solar cell assemblies and modules comprising a plurality of photovoltaic nodes coupled by extendable interconnects. Method of making the same are provided.

[0065] In some embodiments, a photovoltaic cell is provided comprised of a plurality of nodes, each node coupled to another node by an extendable interconnect. At least some of the plurality of nodes are configured to collect photovoltaic energy.

[0066] In an exemplary embodiment, a photovoltaic array is provided comprising: a plurality of nodes connected by extendable interconnects, said nodes being arranged in a regular, ordered arrangement, and wherein certain of the extendable interconnects are configured to provide electrical connection between certain of the nodes. The electrical connection is configured in parallel in some embodiments. Alternatively, the electrical connection is in series. In yet a further alternative embodiment and of particular advantage, the electrical connection is configured such that certain of the nodes are electrically coupled in series, and certain of the nodes are electrically coupled in parallel, or a combination thereof.

[0067] The photovoltaic array may be configured such that the plurality of nodes and extendable interconnects are formed from a monolithic substrate. In some embodiments, a photovoltaic array is provided wherein at least some of the plurality of nodes are comprised of single or multiple p-n junctions. In other embodiments, at least some of the plurality of nodes are configures as an electrical switch.

[0068] Another aspect of the present invention provides a micro-concentrator solar cell assembly. In an illustrative embodiment the micro-concentrator solar cell assembly comprises a plurality of photovoltaic nodes, wherein a respective first node and second node of the plurality of photovoltaic nodes are coupled by extendable interconnects; and a sheet of material is affixed to at least the first node and the second node, wherein the sheet of material holds the first node and the second node and the extendable interconnects in an extended position.

[0069] Additionally, the micro-concentrator solar cell may further comprise a plurality of lenses, having a respective first lens and second lens coupled to the respective first node and second node.

[0070] According to some embodiments, when forming the node, at least two extendable interconnects are attached to and extend from the node and coiled around at least a portion of the node at a minimum radius of curvature (Rm _1n ) of:

where t is the thickness of the extendable interconnect and ε _ma χ is the maximum strain the extendable interconnects can withstand before fracture. In some embodiments, the at least two interconnects are attached to the node at positions such that no substantial torque is experienced by the device upon substantially full extension of the extendable interconnects. The node and the at least two interconnects are preferably monolithic. In some embodiments, the node and the at least two interconnects are monolithic and comprised of silicon. Any number of extendable interconnects may be used. In one exemplary embodiment at least four extendable interconnects are provided. In another embodiment, at least six extendable interconnects are provided.

[0071] The node may take a variety of shapes. In some embodiments the node is comprised of a clover leaf shape. Alternatively, the node is comprised of a rectangular shape. In yet a further embodiment the node is comprised of a hexagonal shape. While specific examples of the node shape are described and shown in the figures, it is to be understood by those in the art that the node may take any number of shapes given the teaching herein, and that certain shapes may be best suited for certain applications and/or manufacturing techniques.

[0072] In some embodiments, the first and second photovoltaic nodes are comprised of any one or more of silicon, gallium arsenide, germanium, indium gallium phosphide, or a combination thereof. In some embodiments, at least one of the first and second photovoltaic nodes is comprised of a clover- leaf like shape. In some embodiments, the first and second photovoltaic nodes and the extendable interconnect are formed of the same material.

[0073] A photovoltaic cell comprises a plurality of nodes, wherein each node is coupled to another node by an extendable interconnect, and where at least some of the plurality of nodes are configured to collect photovoltaic energy.

[0074] In some embodiments, the plurality of lenses are formed in the transparent material. In some embodiments, the transparent material is coupled on a first side of the respective first node and second node, and a reflective material is coupled to a second side of the respective first node and second node opposite to the first side. In some embodiments, a plurality of reflectors are formed in the reflective material. In some embodiments, the sheet of material is aluminum and the aluminum is affixed by an adhesive to at least the first node and the second node and the extendable interconnect.

[0075] In some embodiments, a sheet of material is affixed to at least the first node and the second node, wherein the sheet of material holds the first node and the second node and the extendable interface in an extended position. In some embodiments, the sheet of material is configurable to align the first node and the second node with a respective first and second lens of the plurality of lenses. In some embodiments, the material is a transparent material. In some embodiments, the plurality of lenses are formed in the sheet of transparent material. In some embodiments, the transparent material is coupled on a first side of the respective first node and second node, and a reflective material is coupled to a second side of the respective first node and second node. In some embodiments, a plurality of reflectors are formed in the reflective material. In some embodiments, the sheet of material is aluminum and the aluminum is affixed by an adhesive to at least the first node and the second node.

[0076] A photovoltaic module comprises a plurality of photovoltaic nodes, wherein a respective first node and second node of the plurality of photovoltaic nodes are coupled by an extendable interconnect. A plurality of reflectors is coupled to the plurality of photovoltaic nodes, where a respective reflector of the plurality of reflectors is aligned to concentrate light on a respective node of the plurality of nodes.

[0077] In some embodiments, a sheet of material is affixed to at least the first node and the second node. In some embodiments, the sheet of material holds the first node and the second node and the extendable interface in an extended position. In some embodiments, the sheet of material is configurable to align the first node and the second node with a reflector and a second reflector of the plurality of reflectors. In some embodiments, the sheet of material is a transparent material. In some embodiments, the sheet of material is a sheet of reflective material. In some embodiments, the respective reflector of the plurality of reflectors is formed in the sheet of reflective material. In some embodiments, the sheet of material is aluminum and the aluminum is affixed by an adhesive to the respective reflector.

[0078] The claims provide a device, method, and system for manufacturing a photovoltaic solar module with extended connector network made of stretchable silicon interconnects. The stretchable silicon interconnects (flexible conductor) serves several purposes. It carries voltage generated in the node/node through the mesh, so the voltage can be accumulated. Thus, the conductor serves as a conduit for the energy generated through the photovoltaic effect.

[0079] In addition, embodiments of the photovoltaic array allow a relatively small piece of photovoltaic material to be formed into a plurality of interconnected nodes, and stretched or extended to cover a large area. Photovoltaic materials are relatively expensive, so the array of nodes and extendable interconnects permits a small (thus less expensive) piece of photovoltaic material to be stretched to cover a relatively large area, instead of having to use a large amount of photovoltaic material (with resulting high cost) to cover the same area. This provides significant cost savings. By attaching concentrator lenses or concentrator reflectors or both to the plurality of nodes, a large solar collection area can be concentrated on each node, thus enhancing efficiency. This further reduces the cost per watt of energy generated in the solar cell assembly, and is of significant advantage.

[0080] Moreover, embodiments of the photovoltaic array and micro-concentrator solar cell assembly of the present invention enables applications not otherwise available. In one illustrative example, a photovoltaic array is integrated into or embedded within a window to form a "smart window" or an "active window" meaning that the window itself acts as a photovoltaic cell and thus is capable of generating electricity. In this embodiment, the individual nodes are small, for example without limitation less than 1.0 mm, such that the photovoltaic array appears as a tint on the window and does not substantially obstruct light or viewing through the window.

[0081] Of particular advantage, embodiments of the present invention provide an adaptive architecture. More specifically, in some embodiments additional circuitry or circuit elements may be formed in the array. For example, certain of the plurality of nodes may be configured as a switch instead of a photovoltaic element. In other embodiments at least a portion of the photovoltaic array is configured as circuitry to convert the node outputs to an AC voltage. In yet a further embodiment, at least of portion of the photovoltaic array is configured as circuitry to convert the node outputs to a higher DC voltage. In an even further aspect, embodiments of the invention provide a plurality of nodes connected in series to produce a voltage output suitable to power an inverter.

[0082] In addition, a photovoltaic array is provided that is configured to form a flexible conductor. In some embodiments, a plurality of nodes coupled by extendable interconnects are configured to permit movement in two or three dimensions and form a flexible photovoltaic device. Such a flexible device promotes better resistance to damage from any one or more of: mechanical warping, twisting, expansion due to heat, contraction due to cold, damage during transport, damage from impact, and the like. The flexible device may be installed at locations where a rigid array is unsuitable, such as on curved surfaces, draped on a side of a building, on outdoor equipment, and the like.

[0083] Of particular advantage, embodiments of the present invention are suitable for building integrated photovoltaic (BIPV) applications. In one embodiment a BIPV module is provided comprised of one or more photovoltaic arrays, said array including a plurality of nodes connected by extendable interconnects, said nodes being arranged in a regular, ordered arrangement, and wherein certain of the extendable interconnects are configured to provide electrical connection between certain of the nodes. In some embodiments, the array is affixed to, or integrated with, roof tiles to provide a BIPV system.

[0084] In other embodiments a photovoltaic array and/or micro-concentrator solar cell assembly is configured to be rigid. The rigid array may be installed like a conventional solar cell assembly on the roofs of buildings, on land, and the like.

[0085] Referring now to the figures, certain embodiments of the invention are described in more detail.

[0086] FIGs. IA and IB are top schematic views of a single node with extendable interconnects shown a coiled position and in an extended position, according to some embodiments of the present invention. [0087] FIG. IA illustrates a photovoltaic device 100 having a node or island 110 in a coiled (e.g., unextended) position. This coiled or unextended state typically corresponds to the state of the node as fabricated. The photovoltaic node 110 is comprised of a photovoltaic material, such as but not limited to silicon. Attached to node 110 is an extendable interconnect 116. In some embodiments, the extendable interconnect 116 is coiled around the node 110. Each interconnect 116 is comprised of a connector member or wire having a respective first end 112 and second end 114, each of which are attached to the node 110 at different locations. The interconnect is comprised of any number of member or wires. In some embodiments the interconnect is comprised of between two and eight wires. In some embodiments, the interconnect comprises at least four wires. In some embodiments, the interconnect comprises at least 6 wires.

[0088] The node can be any shape conducive to manufacture of the node and stretching of the interconnects. In some embodiments, the node and/or interconnects can be formed from one or more photovoltaic materials, such as without limitation: silicon, gallium arsenide, germanium, indium gallium phosphide, CIGS, CdTe, and the like.

[0089] FIG. IB illustrates a photovoltaic device 120 with a node in a partially expanded state. The photovoltaic device 120 comprises a node 132 coupled to an extendable interconnect 136 having a first end 130 and a second end 134. The interconnect 136 is partially expanded (e.g., in response to stretching of the first end and/or of the second end).

[0090] The interconnect can have a relaxed position, as shown in FIG. IA, and can have an extended or partially extended position, as shown in FIG. IB. The interconnect can stretch or extend through a range, including from fully relaxed (coiled) to fully extended (no coils), provided however that the upon extension the interconnect does not experience strain that would exceed the level of strain where fracture or permanent deformation would occur.

[0091] In some embodiments, the interconnect 116 is configured to return from a first extended position to a second relaxed position upon release of a tension or force associated with the first extended position. The interconnect 116 may comprise an elastic spring action. An elastic (or mechanical) spring action means that the interconnect is formed in the shape of a elastic spring, and acts with a spring-stretch behavior.

[0092] To develop a particular node and interconnect geometry, the inventors have developed a process sequence for designing the as illustrated schematically in FIG. 1C. First, the array of nodes is defined by establishing points where the nodes will be positioned at 150. Next, the interconnections are defined at 152 as lines or vectors such that forces on the node and interconnects during extension will be substantially balanced. This will define the location of attachment of the interconnect to the node as well as the number of interconnect members or wires to be used. To form a packed array of nodes that will be extended, at step 154 the interconnect members are coiled around the node. Preferably the members are coiled at the smallest radius possible such that the strain experienced by the node and/or interconnects during extension does not exceed the fracture stain of the material. Next, the area of the node is maximized, meaning that actual shape of the node is selected such that the area of the node is as large as possible being constrained only by the coiled interconnect members as shown at step 156. According to these principles, this results in a cloverleaf shaped node with four member interconnects.

[0093] Embodiments of the photovoltaic array of the present invention may be used to form micro-concentrator solar cell assemblies and modules. FIG. 2 illustrates a cross sectional view of a portion of a solar cell assembly having plurality of reflectors, according to some embodiments of the present invention.

[0094] Solar cell assembly 200 is configured to receive radiation 204 from a source (e.g., the Sun 202) or some other radiating energy source such as bright lights inside a building (for energy recycling, etc.).

[0095] In one exemplary embodiment solar cell assembly 200 is generally comprised of a transparent layer 210 through which incident radiation passes, a substrate or support 214, and a plurality of photovoltaic nodes 218. The transparent layer 210 is formed of any suitable transparent material, such as without limitation: glass, plastic, silicon dioxide and the like. The substrate 214 is comprised of any suitable substrate material, such as without limitation: glass, plastic, metal, ceramic, polymer and the like. The transparent layer 210 is supported by one or more supports or posts 212 and is spaced apart from the substrate 214.

[0096] To concentrate solar radiation onto the photovoltaic nodes 218, the assembly may further comprise a one or more concentrating lenses, reflectors, or a combination of both lenses and reflectors. In the illustrative embodiment shown in FIG. 2, a surface of the transparent layer 210 is shaped (such as by molding, machining, cutting, stamping, etching, and the like) to form a plurality of lenses or concentrators 220 on the surface, for the purpose of focusing light energy. Alternatively, individual lenses or concentrators 220 may be carried on the surface of the transparent layer 210. Preferably, a respective lens is aligned to concentrate light onto a respective photovoltaic node.

[0097] In some embodiments, the lenses or concentrators are positioned on the side of the transparent layer 210 that faces the sun. Alternatively, the lenses or concentrators are positioned on the side of the transparent layer 210 that faces away from the sun.

[0098] Any type of lens or concentrator may be used. For example, and without limitation, the concentrator or lens may be comprised of any one or more of: concave lens, convex lens, parabolic lens, aspheric lens, Fresnel lens, droplet shaped lens, and combinations thereof.

[0099] Photovoltaic nodes 218 are coupled to, or positioned near, the concentrator lenses

220 such that the lenses 220 concentrate light onto the node 218, either directly or indirectly. The node thereby receives more light energy than if it were just receiving direct energy from the sun. Indirect concentration of light may be achieved by reflection of light off of reflectors 216 and onto the nodes 218. In some embodiments, the reflectors 216 are supported by, or carried on, the substrate 214. Alternatively, the reflectors 216 may be formed in a surface of the substrate 214. In some embodiments, the plurality of reflectors 216 are formed a reflective material. For example a sheet of reflective material such as aluminum may be plated on one surface of the substrate 214.

[00100] In some embodiments, the reflectors 216 are configured to focus light on the photovoltaic nodes 218, where a respective reflector is aligned to concentrate light on a respective photovoltaic node.

[00101] Any type of reflector may be used. For example, and without limitation, the reflector may be comprised of any one or more of: concave reflector, convex reflector, parabolic reflector, aspheric reflector, diffractive reflector, zone plate, and combinations thereof.

[00102] The nodes 218 are coupled together by extendable interconnects (not shown in

FIG. 2). In some embodiments, the extendable interconnect and/or node is affixed to a sheet of material, such as but not necessarily the transparent layer 210, and is held in position relative to the lenses by the layer 210. Alternatively, an additional transparent sheet 219 is used to affix the interconnect and/or node. In some embodiments, the sheet 219 has bumps, markers or other alignment mechanisms (e.g., visual, tactile, electronic, mechanical, etc.) formed thereon to align the lens 220 to the node 218.

[00103] A gap 222 may exist between the reflectors 216 and the nodes 218. The gap 222 may be filled with air or with a gas, such as an inert gas. In some embodiments, gap 222 is filled with a transparent material, such as a transparent gel and the like. In some embodiments gap 222 is filed with a transparent gel, such as without limitation silicone.

[00104] Another embodiment is shown in FIG. 3 which illustrates a cross sectional view of a portion of a solar cell assembly 300 having a plurality of concentrator lenses configured to receive solar radiation 304.

[00105] The assembly 300 generally comprises a transparent layer 310 through which incident radiation passes, a substrate or support 314, and a plurality of photovoltaic nodes 318. The transparent layer 310 is formed of any suitable transparent material, such as without limitation: glass, plastic, silicon dioxide, and the like. The substrate 314 is comprised of any suitable substrate material, such as without limitation: glass, plastic, metal, ceramic, polymer and the like. The transparent layer 310 is supported by one or more supports or posts 312 and is spaced apart from the substrate 314. The transparent layer 310 is shaped (e.g., by molding, machining, cutting etc.) to have a plurality of Fresnel lenses 320 or concentrators. In this embodiment light passes through the transparent layer 310 and is refracted from the facets of the Fresnel lens 320 and focused on the nodes 318.

[00106] In the exemplary embodiment shown in FIG. 3, the photovoltaic nodes 318 are positioned beneath the Fresnel lenses 320 such that the lenses concentrate light onto the node 318. In some embodiments, facets of the Fresnel lenses are arranged so that they focus light on the node over a range of angles of incident light (e.g., as the sun moves across the sky, the angle at which sunlight reaches the glass/plastic will change).

[00107] The nodes 318 are connected together by extendable interconnects (not shown in

FIG. 3). In some embodiments, the nodes and extendable interconnect are coupled to a sheet of material 319 (such as a sheet of transparent material) and held in position relative to the lenses or to the substrate by the sheet 319. In some embodiments, the extendable interconnect may flex in response to current, voltage, charge or other electrical stimulus to position the nodes 318 at an optimal position to receive as much sunlight as possible if the point of focus of the Fresnel lens changes due to movement of the sun across the sky. [00108] In some embodiments, a gap 322 exists between the Fresnel lens 320 and the nodes 318. The gap may be filled with air. In some embodiments, the gap is filled with gas, such as an inert gas. In other embodiments, this gap is filled with a transparent material, such as a transparent gel.

[00109] Turning to FIGs. 4A and 4B cross sectional views of a portion of a solar cell having a reflector or having a concentrator lens, respectively, are shown according to some embodiments of the present invention.

[00110] FIG. 4A illustrates a reflector solar cell assembly 400, for converting solar radiation 404 from the sun 402 to electrical energy. The cell comprises a substrate 414 and one or more supports 412, as described above. The cell comprises a reflector 420, such as a parabolic reflector, a concave reflector, and the like, configured to receive the solar radiation and to concentrate it onto a photovoltaic node 418, as described above. The node can receive both direct (straight from the sun) and reflected (from reflector 420) solar energy.

[00111] In some embodiments, the node may be placed proximate to the reflector, with a gap between the node and the glass or plastic layer 410. In some embodiments, there is a gap 422 between the node and the reflector, and the node is coupled proximate to the glass or plastic layer 410. In some embodiments, the gap is filled with air, gas or a transparent material or gel such as without limitation silicone, as described.

[00112] FIG. 4B illustrates a concentrator solar cell assembly 430, for converting solar radiation 434 from the sun 432 to electrical energy. The cell comprises a substrate 444, transparent layer 440, and one or more supports 442, as described. The cell comprises a concentrator 450 configured to receive the solar radiation and to concentrate it onto a photovoltaic node 448, as described. The node can receive both direct (straight from the sun) and focused (by concentrator 450) solar energy. In some embodiments, the concentrator 450 comprises glass, plastic, transparent gel or some other material capable of refracting light.

[00113] In some embodiments, there is a gap 452 between the node and the reflector. In some embodiments, the gap is filled with air, gas or a transparent material or gel, as described.

[00114] The photovoltaic array of the present invention is preferably monolithic, such that the node and interconnect are fabricated from a single substrate material. Accordingly, embodiments of the present invention further provide methods of making photovoltaic arrays and assemblies. Turning to FIGs. 5A - 5D a series of process sequences or operations are schematically illustrated showing a process for manufacturing a solar cell assembly or module having an array of nodes and extendable interconnectors, according to some embodiments of the present invention.

[00115] FIG. 5A illustrates an operation 500, where nodes 502 and interconnect 503 are released or separated from a bulk wafer 504 (on which the nodes and interconnect were initially fabricated by photolithography and processing as described in detail below with reference to FIGs. 11 - 17). In this embodiment, the nodes 502 and interconnects 503 are formed from a monolithic silicon substrate. In this embodiment, release is performed by etching an undercut using an anisotropic etchant such as tetramethylammonium hydroxide (TMAH or TMAOH), a quaternary ammonium salt with the molecular formula (CHs) ₄ NOH. TMAH is applied around the nodes and interconnect and etches the silicon around and underneath the nodes, leaving break-away connection tabs 510. This releases the array structure from the bulk wafer (which now serves as a handle).

[00116] FIG. 5B illustrates an operation 520, where an electrostatic chuck (e-chuck) 526 holds a carrier wafer, such as a quartz wafer having indium tin oxide (ITO), or tin-doped indium oxide. The e-chuck and carrier wafer are electrostatically coupled (chucked) to nodes 522, attached by break-away connection tabs to wafer 524. The e-chuck 526 lifts the nodes and breaks the tabs, releasing the nodes and interconnects from the bulk wafer 524. The e-chuck inverts 530, positioning the nodes 522 and the carrier wafer for passivation. The carrier wafer allows the array to be passivated, as the carrier is processed like a standard wafer. Passivation is the application of a protective layer over a silicon wafer.

[00117] FIG. 5C illustrates an operation 540, where a first electrostatic chuck (e-chuck)

514 holds a carrier wafer with nodes and array 542. A second e-chuck 546 electrostatically picks up (chucks) the nodes and array 542, and rotates in operation 548 to position the nodes for stretching and lamination. The array is then stretched 555 using probe station 600 (see FIG. 6) described below, resulting in a stretched array 542. The second e-chuck 546 may be optimized to facilitate stretching, e.g., via a non-stick or low friction coating or oil, such as without limitation Teflon or hexagonal boron nitride (HBN, also referred to as white graphite).

[00118] FIG. 5D illustrates an operation 560, where the second electric chuck (e-chuck)

546 presents the stretched array 562 for lamination 566. In some embodiments, a lamination sheet comprises a first adhesive layer 568 and a second reflective layer 567 (e.g., aluminum). The laminated array is removed from the e-chuck 570 and positioned for lens attachment. Lenses 574 are coupled to the laminated nodes 562 on sheet 566. This provides a finished cell.

[00119] As initially fabricated, the plurality of nodes and interconnects are in the coiled, or un-extended state (as shown in FIG. 5B prior to stretching). To form the photovoltaic array and then the solar cell assembly, the nodes and coiled interconnects are extended or stretched. FIG. 6 illustrates an exemplary probe station 600 for stretching or extending the plurality of nodes and interconnects, according to some embodiments of the present invention. The probe station 600 utilizes manipulators that allow the precise positioning of pins or thin needles on the surface of the plurality of nodes and interconnects, and movement of the pins (to stretch the mesh) after positioning.

[00120] In general the probe station 600 comprises a platform 602, to which probe controls 610, 612, 614, and 616 are mounted. A probe control typically has an arm to hold a pin or needle, and very fine adjustment controls to direct the pins 620 to a specific point on a node or silicon mesh 622. The probe controls may be manual or may be computer controller. A computer may execute a program to control the probes to automatically stretch the array. The probe station 600 is used to physically contact and stretch nodes in an extended connector network.

[00121] In some embodiments, the probe station 600 includes an optical device 630, such as a microscope for manual control, a camera for automatic control, or a combination of both. The optical device 630 allows a user or computer to see the array to be stretched, and to position the probe needles on elements in the array. The probe needles may then be used to stretch the array and/or to electrically stimulate and/or take measurements from the array.

[00122] In some embodiments, the probe station may also be used to measure electrical properties of the mesh before, during and after the stretching process. For example, properties such as resistance, current, voltage, opens, shorts, and floating nodes may be measured and used to identify potential failures or reliability problems with the stretched mesh.

[00123] FIG. 7 illustrates pins for stretching an extended connector network, according to some embodiments of the present invention. Specifically, probes 710, 712, 714, 716 hold pins 720, 722, 724, 726 respectively. The pins are positioned over the nodes 730. The pins are controlled either manually or automatically, as described. In some embodiments, the pins touch and stretch the nodes, causing the nodes and interconnects to move apart, thus extending the coiled interconnects between the nodes. In other embodiments, the pins touch tabs carried on the mesh as opposed to contacting the nodes.

[00124] FIG. 8A illustrates an SEM photograph 800 of pins touching photovoltaic nodes, to stretch coiled interconnects between the nodes into an extended connector network, according to some embodiments of the present invention. Pin tips 810, 812, 814, 816 make contact with coiled (unstretched) nodes 820, 822, 824, 826, respectively. In some embodiments (as seen in the photograph 800) the nodes have an approximately clover-leaf shape as shown schematically in FIG 8B where nodes 840, 842, 844, 846 are illustrated as close together with interconnects between the nodes in a coiled state.

[00125] While one particular node geometry is shown, those of skill in the field will recognize that based on the teaching herein, the nodes can have a variety of shapes.

[00126] FIG. 9A is a SEM photograph 900 of photovoltaic nodes in an extended array, where the nodes are stretched and the interconnects are extended and visible between the nodes, according to some embodiments of the present invention. FIG. 9B is a schematic illustration of a portion of the array with nodes 910, 912, 914, 916 and interconnects 920, 922, 924, 926 in the extended position.

[00127] As described above in some embodiments, the photovoltaic array with a plurality of nodes and extendable interconnnects is formed in the un-extended state as initially fabricated. FIG. 10 is a flowchart 1000 depicting a method to manufacture and assemble a photovoltaic array according to some embodiments of the present invention. Certain of the operations to process the array and the assemblies may use semiconductor processing steps used in mono- crystalline photovoltaic processing.

[00128] An exemplary method is now described in detail with reference to FIG. 10. In an operation 1010, a foundry photovoltaic processing operation is performed to form a photovoltaic array. A monolithic substrate is provided, such as for example a silicon wafer or substrate. The surface of the may substrate be textured to aid in retaining light inside the node. The desired nodes and interconnect pattern is formed using photolithography techniques know in the art. A P+/N+ junction is formed at one of more of the nodes. In some embodiments, contacts are formed on the front of the node and metallization is formed on the back of the node. Anisotropic ion etching, such as but not limited to deep reactive ion etch (DRIE) step, is performed to physically separate the nodes from the interconnect and allow for stretching of the photovoltaic array. A passivation layer may be grown on the surface of the node and interconnect to act as a protective layer.

[00129] In an operation 1020, the substrate or wafer is etched to prepare for release/separation of the photovoltaic array. In some embodiments, etching is performed as a wet release of silicon using TMAH.

[00130] In an operation 1030, a first chucking operation and node passivation are performed. This first chucking removes the array of nodes and interconnects from the wafer, and allows for further processing of the array.

[00131] In an operation 1040, a second chucking operation and stretch/lamination are performed. The second chucking properly orients the array for stretch and lamination.

[00132] To form a micro-concentrator solar cell assembly, the array is further processed.

In an operation 1050, a lens attach operation is performed. The lenses are positioned such that a respective lens and a respective node are aligned. Then the lenses are attached to the array after the array is transferred to a laminate substrate.

[00133] Another example of methods of the present invention are shown in FIG. 11 for manufacturing a photovoltaic array having a plurality of nodes and extendable interconnects.

[00134] In an operation 1100, a random texture (rantex) is formed on a starting material

(substrate) 1114. A passivation oxide 1112 is grown or deposited on the random texture.

[00135] In an operation 1130, N+/P+ masking, N+/P+ implant, and N+/P+ anneal operations are performed to create N-type 1134 and P-type 1132 junctions at desired nodes.

[00136] In an operation 1150, contacts are formed by metal deposition. The metal is patterned 1152, 1154 and 1156 to isolate the N+ and P+ junctions.

[00137] If a piece of p-type silicon is placed in intimate contact with a piece of n-type silicon, then a diffusion of electrons occurs from the region of high electron concentration (the n-type side of the junction) into the region of low electron concentration (p-type side of the junction). When the electrons diffuse across the p-n junction, they recombine with holes on the p-type side. The diffusion of carriers does not happen indefinitely however, because of an electric field that is created by the imbalance of charge immediately on either side of the junction that this diffusion creates. The electric field established across the p-n junction creates a diode that promotes current to flow in only one direction across the junction. Electrons may pass from the n-type side into the p-type side, and holes may pass from the p-type side to the n- type side, but not the other way around. This region where electrons have diffused across the junction is called the depletion region (or "space charge region") because it no longer contains any mobile charge carriers.

[00138] Ohmic metal-semiconductor contacts are made (by metal deposition, as described) to both the n-type and p-type sides of the solar cell, and the electrodes connected to an external load. Electrons that are created on the n-type side, or have been "collected" by the junction and swept onto the n-type side, may travel through the wire, power the load, and continue through the wire until they reach the p-type semiconductor-metal contact. Here, they recombine with a hole that was either created as an electron-hole pair on the p-type side of the solar cell, or are swept across the junction from the n-type side after being created there.

[00139] FIG. 12 illustrates process steps 1200 for manufacturing a photovoltaic node and extendable interconnect, according to some embodiments of the present invention.

[00140] In an operation 1210, openings 1212 are formed in the substrate using deep reactive-ion etching (DRIE). DRIE is a highly anisotropic etch process used to create deep, steep-sided holes and trenches in wafers, with aspect ratios of 20:1 or more.

[00141] In an operation 1230, sidewalls are passivated 1232 using plasma enhanced chemical vapor deposition (PECVD). PECVD is a process used to deposit thin films from a gas state (vapor) to a solid state on some substrate. There are some chemical reactions involved in the process that occur after creation of a plasma of the reacting gases. An anisotropic plasma etch is used. The passivation layer protects the structure for contamination, physical damage, etc.

[00142] In an operation 1250, tetramethylammonium hydroxide (TMAH or TMAOH) is used to release the structure from the substrate. The TMAH etches a gap 1252 under the structure.

[00143] FIG. 13 illustrates process steps 1300 for a chucking operation, according to some embodiments of the present invention.

[00144] In an operation 1310, the structure 1312 (etched from the substrate handle wafer) is positioned for chucking.

[00145] In an operation 1330, an electrostatic chuck 1332 picks up (by electrostatic force) the structure 1312 and lifts it off (releases it from) the substrate 1314. In an operation 1350, the electrostatic chuck 1332 transports the structure 1312 away from the substrate 1314. [00146] FIG. 14 illustrates process steps 1400 for a chucking operation, according to some embodiments of the present invention.

[00147] In an operation 1410, a chuck 1412 rotates to present a structure for passivation.

The chuck is loaded into a cassette. The chuck functions as a temporary handle wafer.

[00148] In an operation 1430, a passivation layer is deposited by PEVCD on the sunny side of the structure/wafer. In an operation 1450, a second chuck 1452, optionally having a Teflon coating, is positioned proximate to the passivated structure.

[00149] FIG. 15 illustrates process steps 1500 for a chucking operation, according to some embodiments of the present invention.

[00150] In an operation 1510, the second chuck 1512, optionally having a Teflon coating, picks up (by electrostatic force) the passivated structure 1514 from first chuck 1516. The array is now ready for stretching and lamination.

[00151] In an operation 1530, the second chuck 1512, holding the passivated structure

1514, is removed from the first chuck 1516. In an operation 1550, the second chuck 1512, holding the passivated structure 1514, is rotated to present the passivated structure for lamination and stretching.

[00152] FIG. 16 illustrates process steps 1600 for stretching a photovoltaic node and for attaching a lens to the photovoltaic node and stretched interconnect, according to some embodiments of the present invention.

[00153] In an operation 1610, the structure and interconnect are stretched, physically separating the node 1618 from the interconnect. A lamination 1620 having a transparent layer 1624 and a reflective layer 1622 is applied to the node 1618. The structure/array is then pulled away from the chuck. The laminated array is ready for lens alignment and attach. In an operation 1630, a lens 1632 is aligned with and attached to the node 1618.

[00154] FIG. 17 illustrates an alternative non-release flow, according to some embodiments of the invention. In an operation 1710, a substrate material is formed. In some embodiments, the substrate material is approximately 200 um thick. In some embodiments, the substrate is between 150 and 250 um thick. In some embodiments, the substrate is between 50 and 500 um thick. In some embodiments, the substrate is between 10 and 1000 um thick.

[00155] A thermal oxidation operation and low-pressure CVD operation is performed to create silicon nitride Si ₃ N ₄ . Low-pressure CVD (LPCVD) processes are performed at sub atmospheric pressures. These reduced pressures tend to reduce unwanted gas-phase reactions and improve film uniformity across the wafer.

[00156] In an operation 1730, front side removal of SiO ₂ ZSIsN ₄ is performed. Random texturing with KOH RanTex is performed to improve light retention.

[00157] Thermal oxidation is performed, as described, to create silicon nitride Si ₃ N ₄ . P+ and N+ junctions are created in operation 1750, as described.

[00158] FIG. 18 illustrates an optical reflector 1800 for concentrating light on a photovoltaic node, according to some embodiments of the invention.

[00159] An array 1820 of concentrators/reflectors 1822, 1824, 1826 is coupled to nodes

1810, 1812, 1814. The array of concentrators/reflectors receives light 1800, and through a combination of concentrating (e.g., using a concentrator lens, as described) and/or reflecting (e.g., using a reflective mirror, as described) focuses the light on a node. In some embodiments, the concentrator/reflector has a light catchment area 1830 (i.e., a surface area for catching light). In some embodiments, the node has an active surface area (area that converts light to electricity) of 1834. The light catchment area is greater than the active surface area (also referred to as the concentration ratio), so as to concentrate more light on the node than it would receive through direct light alone, and thus is an optical concentrator.

[00160] In some embodiments, the array of concentrators/reflectors 1822, 1824, 1826,

1828 is arranged to minimize a loss of light between them, i.e., to maximize the amount of light received at the concentrators/reflectors that is delivered to a node. This maximizes the efficiency of energy conversion by the nodes.

[00161] In some embodiments the concentrators/reflectors 1820 comprise a refractive focusing lens portion and reflecting mirror portion. In some embodiments the concentrators/reflectors 1820 comprise reflecting mirror portion, without a refractive focusing lens portion.

[00162] In some embodiments, the light catchment area (also referred to as the

"concentration ratio") is at least eight times greater than the active surface area. In some embodiments, the light catchment area is at least four times greater than the active surface area. In some embodiments, the light catchment area is at least twice the active surface area. In other embodiments the concentration ratio, or the light catchment area to the active surface area, is in a range of 2 to 1000. [00163] Fabrication of the nodes, arrays and assemblies according to embodiments on the present invention may be carried out with the aid of computer or other automated control systems. In some embodiments a computer system is provided. FIG. 19 is a block diagram of a system 1900, such as a manufacturing system, production control system, photovoltaic device design system, and the like. The system 1900 generally includes one or more processing units (CPU's) 1902, optionally one or more network or other communications interfaces 1904, memory 1910, and one or more communication buses 1908 for interconnecting these components. The communication buses 1908 may include circuitry (sometimes called a chipset) that interconnects and controls communications between system components. The system 1900 may optionally include a user interface, for instance a display 1906 and an input device 1905. Memory 1910 may include high speed random access memory and may also include nonvolatile memory, such as one or more magnetic disk storage devices. Memory 1910 may include mass storage that is remotely located from the central processing unit(s) 1902.

[00164] Memory 1910, or alternately the non- volatile memory device(s) within memory

1910, comprises a computer readable storage medium. In some embodiments, memory 1910 stores the following programs, modules and data structures, or a subset thereof: (i) an operating system 1911 that includes procedures for handling various basic system services and for performing hardware dependent tasks; (ii) an optional network communication module 1912 that is used for connecting the system 1900 to other computers via the one or more communication network interfaces 1904 (wired or wireless) and one or more communication networks, such as the Internet, other wide area networks, local area networks, metropolitan area networks, and so on; (iii) a fabricate node module 1920 that controls or manages instructions to control semiconductor fabrication equipment, for fabricating the photovoltaic node and extendable interconnect, for performing a deep reactive ion etch (DRIE) for separating the node and interconnect, for chucking the node and interconnect off a wafer, for stretching the node and interconnect, and for laminating the stretched node and interconnect; (iv) an attach lens module 1930, that controls or manages instructions to control optical assembly equipment, for aligning a node (laminated or unlaminated) with a lens, for attaching a lens array to an array of nodes (laminated or unlaminated), and for securing a lens array and node array in a module; (v) an attach mirror module 1940, that controls or manages instructions to control mirror assembly equipment, for attaching a mirror (e.g., a concentrator mirror) to a node, including to a node having a lens, and for securing a mirror array and a node array in a module; (vi) an assemble solar panel module 1950, that controls or manages instructions to control solar panel manufacturing equipment, wherein the solar panels comprise a plurality of nodes and stretched interconnects, wherein the nodes and interconnects are fabricated together; (vii) a node communication module 1960, that controls or manages instructions to communicate between nodes in a solar panel, wherein the solar panels comprise a plurality of communication-enabled nodes and stretched communication-enabled interconnects, including multi-bit and multi-core interconnects; (viii) a process monitor module 1970, that controls or manages instructions to receive process information (e.g., wafer processing parameters) from communication-enabled nodes in a solar panel, allowing variations in process properties and electrical properties to be determined, along with opens, shorts and weak connections; and (ix) auxiliary services module 1990 for managing other services related to photovoltaic nodes or panels.

[00165] Each of the above identified elements may be stored in one or more of the previously mentioned memory devices, and corresponds to a set of instructions for performing a function described above. The above identified modules or programs (i.e., sets of instructions) need not be implemented as separate software programs, procedures or modules, and thus various subsets of these modules may be combined or otherwise re-arranged in various embodiments. In some embodiments, memory 1910 may store a subset of the modules and data structures identified above. Furthermore, memory 1910 may store additional modules and data structures not described above.

[00166] Although FIG. 19 shows a "system," FIG. 19 is intended more as functional description of the various features that may be present in a set of processors (e.g., in clients or in servers) than as a structural schematic of the embodiments described herein. In practice, and as recognized by those of ordinary skill in the art, items shown separately could be combined and some items could be separated. For example, some items shown separately in Figure 19 could be implemented on single servers and single items could be implemented by one or more servers. The actual number of resources used to implement a system and how features are allocated among them will vary from one implementation to another.

[00167] FIG. 2OA is a flowchart representing a method 2000 for fabricating nodes having an extendable interconnect, according to certain embodiments of the invention. Method 2000 may be governed by instructions that are stored in a computer readable storage medium and that are executed by one or more processors of one or more servers. Each of the operations shown in FIG. 2OA and FIG. 2OB may correspond to instructions stored in a computer memory or computer readable storage medium. The computer readable storage medium may include a magnetic or optical disk storage device, solid state storage devices such as Flash memory, or other non- volatile memory device or devices. The computer readable instructions stored on the computer readable storage medium are in source code, assembly language code, object code, or other instruction format that is interpreted by one or more processors.

[00168] A respective first node and a respective second node of a plurality of photovoltaic nodes are located (2002), wherein the first node and second node are coupled by an extendable interconnect. Locating means that positions of nodes (e.g., nodes 820, 822, 824, 828 of FIG. 8) to be used for stretching are determined, e.g., by fabricate node module 1920, as shown in FIG. 19. In some embodiments, the respective first node and the respective second node are located on a wafer chuck (2014). In some embodiments, the plurality of nodes and the extendable interconnect are held to the wafer chuck by an electrostatic force (2016).

[00169] A first pin (e.g. 810, FIG. 8) is placed on the first node and a second pin (e.g.,

814, FIG. 8) is placed on the second node (2004).

[00170] The first pin and second pin are moved apart (2006) while retaining contact with the respective first node and second node, e.g., by fabricate node module 1920, FIG. 19. This causes the interconnect (see 901, FIG. 9) between the nodes to stretch and extend. The nodes are now stretched over a greater area than beforehand.

[00171] In some embodiments, a lamination sheet is applied (2008) to at least a portion of the plurality of nodes and the extendable interconnect. In some embodiments, the lamination sheet (e.g., sheet 219, FIG. 2 or sheet 1620, FIG. 16) fixes (2010) the relative position of the portion of the plurality of nodes and the extendable interconnect. In some embodiments, the first probe and the second probe are removed (2012).

[00172] In some embodiments, the laminated sheet is aligned with an array of lenses, and a respective lens of the array of lenses is attached to a respective node of the plurality of nodes (2014). In some embodiments, concentrating mirrors are aligned with the array of lenses and the plurality of nodes, forming a solar cell array (2016). In some embodiments, the solar cell array is secured in a solar module (2018).

[00173] FIG. 2OB is a flowchart representing a method 2020 for fabricating nodes having an extendable interconnect, according to certain embodiments of the invention. [00174] A respective first node and a respective second node of a plurality of photovoltaic nodes are fabricated (2022) on a wafer, wherein the first node and second node are coupled by a coiled interconnect (e.g., nodes 840, 844 in FIG. 8B). In some embodiments, a p-type junction and an n-type junction (e.g., junctions 1132, 1134, FIG. 11) are formed (2024), and contacts are formed coupled to the p-type junction and an n-type junction respectively, for each node of the plurality of photovoltaic nodes on the wafer.

[00175] Anisotropic etching, such as deep reactive ion etch (e.g., etch 1212, FIG. 12) is performed (2026) between portions of the coiled interconnect. Portions of the wafer between portions of the coiled interconnect are removed (2028) by etching. In other embodiments, the etching could be replaced by some other step that removes material (i.e., cuts trenches) between the coils of the interconnect, such as by laser cutting, etc.

[00176] The plurality of nodes and interconnect are released (e.g., release 1252, FIG. 12) from the wafer (2030). Releasing the plurality of nodes and interconnect mechanically separates the portions of the coiled interconnect. In some embodiments, this allows the coiled interconnect to extend.

[00177] FIGs. 21 A and 21B illustrate exemplary photographs of top view of a network of nodes with expandable interconnects, according to some embodiments of the present invention.

[00178] FIG. 21 A illustrates 2100 a plurality of nodes 2110, each having a coiled interconnect 2112. Lines of the coiled interconnects are coupled to the nodes at points 2116. The coiled interconnects are coupled together (forming a mesh) at connection points 2114. The nodes 2110, interconnect 2116 and connection points 2116 form a stretchable photovoltaic array.

[00179] FIG. 21B illustrates 2120 a close-up view of a node 2128, having attachments

2124 for coiled interconnect 2126.

[00180] FIGs. 22A and 22B illustrate exemplary photographs of top view of a node with expandable interconnect, according to some embodiments of the present invention.

[00181] FIG. 22A illustrates 2200 a close-up view of a coiled node 2214, having a coiled interconnect 2212, with a first end 2216 and second end 2218. When the first and second end are stretched apart, the interconnect uncoils. [00182] FIG. 22B illustrates 2220 a close-up view of an uncoiled node 2214, showing a first portion 2226 and second portion 2228 of a stretched (uncoiled) interconnect.

[00183] The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.