CN112349794A

CN112349794A - Single step formation of metal bonds and contacts for solar cells

Info

Publication number: CN112349794A
Application number: CN202011083025.4A
Authority: CN
Inventors: 金泰锡; 林承笵; 马蒂厄·穆尔斯
Original assignee: Total Marketing Services SA; SOLAR ENERGY Co
Current assignee: TotalEnergies Marketing Services SA; SOLAR ENERGY Co
Priority date: 2013-12-20
Filing date: 2014-12-19
Publication date: 2021-02-09
Anticipated expiration: 2034-12-19
Also published as: TWI645575B; WO2015095820A1; CN105830234A; CN112349794B; CN105830234B; TW201530795A

Abstract

The invention discloses a method for manufacturing a solar cell. The method can include forming a dielectric region on a surface of a solar cell structure and forming a first metal layer on the dielectric region. The method may also include forming a second metal layer on the first metal layer and locally heating a particular region of the second metal layer, wherein heating includes forming a metal bond between the first metal layer and the second metal layer and forming a contact between the first metal layer and the solar cell structure. The method can include forming an adhesive layer on the first metal layer and forming a second metal layer on the adhesive layer, wherein the adhesive layer mechanically couples the second metal layer to the first metal layer and allows for an electrical connection between the second metal layer and the first metal layer.

Description

Single step formation of metal bonds and contacts for solar cells

This application is a divisional application based on chinese patent application having application date 2014, 12/19, application number 2014800687727 (international application number PCT/US2014/071718), entitled "single step formation of metal bonds and contacts of solar cells".

Technical Field

Embodiments of the subject matter described herein relate generally to solar cells. More particularly, embodiments of the subject matter relate to solar cell fabrication processes and structures.

Background

Solar cells are well known devices for converting solar radiation into electrical energy. The solar cell has a front side, which faces the sun during normal operation to collect solar radiation, and a back side opposite the front side. Solar radiation impinging on the solar cell produces an electrical charge that can be used to power an external circuit, such as a load. The external circuit may receive current from the solar cell through metal fingers connected to the doped regions of the solar cell.

Disclosure of Invention

In an embodiment, a method for fabricating a solar cell is disclosed. The method can include forming a dielectric region on a surface of a solar cell structure. The method may also include forming a first metal layer on the dielectric region. The method may include forming a second metal layer on the first metal layer and locally heating a particular region of the second metal layer, wherein heating includes forming a metal bond between the first metal layer and the second metal layer and forming a contact region between the first metal layer and the solar cell structure.

In an embodiment, a method for fabricating a solar cell is disclosed. The method can include forming a dielectric region on a surface of a solar cell structure. The method may also include forming a first metal layer on the dielectric region. The method may include forming an adhesive layer on the first metal layer and forming a second metal layer on the adhesive layer, wherein the adhesive layer mechanically couples the second metal layer to the first metal layer and allows for electrical connection between the second metal layer and the first metal layer.

In an embodiment, a solar cell fabricated using any of the above methods is disclosed.

These and other features of the present disclosure will be apparent to those of ordinary skill in the art upon review of the entire disclosure, including the drawings and claims.

Drawings

The subject matter may be more completely understood by reference to the following detailed description and claims when considered in connection with the following drawings, in which like reference numerals refer to like elements throughout.

Fig. 1 is a schematic flow diagram of an exemplary method of fabricating a solar cell according to some embodiments;

FIG. 2 is a cross-section of a first metal layer and a second metal layer on a solar cell structure;

FIG. 3 is a cross section of locally heating a second metal layer according to some embodiments;

FIG. 4 is a cross-section of forming a metal bond according to some embodiments;

FIG. 5 is a cross-section of forming a contact according to some embodiments;

FIG. 6 is a cross-section of an exemplary solar cell fabricated in accordance with the disclosed technique;

FIG. 7 is a schematic plan view of an example of a metal layer according to some embodiments;

FIG. 8 is a schematic flow diagram of another exemplary method of fabricating a solar cell according to some embodiments;

FIG. 9 is a cross-section of an adhesive layer formed on a first metal layer according to some embodiments;

FIG. 10 is a cross-section of a second metal layer formed on an adhesive layer according to some embodiments;

FIG. 11 is a cross-section of another exemplary solar cell fabricated in accordance with the disclosed technique;

FIG. 12 is a cross-section of yet another exemplary solar cell fabricated in accordance with the disclosed technique;

FIG. 13 is a schematic flow diagram of yet another exemplary method of fabricating a solar cell according to some embodiments;

FIG. 14 is a cross-section of an adhesive layer formed on a first metal layer according to some embodiments;

FIG. 15 is a cross-section of a second metal layer formed on an adhesive layer according to some embodiments;

fig. 16 is a cross section of a metal bond, a contact, and a cured adhesive layer according to some embodiments;

FIG. 17 is a cross-section of a patterned metal layer according to some embodiments;

FIG. 18 is a cross-section of an exemplary solar cell fabricated in accordance with the disclosed technique; and is

Fig. 19 is a cross-section of yet another exemplary solar cell fabricated in accordance with the disclosed technique.

Detailed Description

The following detailed description is merely exemplary in nature and is not intended to limit the embodiments of the subject matter or the application and uses of such embodiments. As used herein, the word "exemplary" means "serving as an example, instance, or illustration. Any implementation described herein as exemplary is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.

This specification includes references to "one embodiment" or "an embodiment". The appearances of the phrase "in one embodiment" or "in an embodiment" are not necessarily referring to the same embodiment. The particular features, structures, or characteristics may be combined in any suitable manner consistent with the present disclosure.

Terminology. The following paragraphs provide definitions and/or background for terms present in this disclosure (including the appended claims):

"comprises". The term is open ended. As used in the appended claims, the term does not exclude additional structures or steps.

"configured to". Various units or components may be described or claimed as "configured to" perform one or more tasks. In such a context, "configured to" is used to connote structure by indicating that the unit/component includes structure to perform one or more of those tasks during operation. Thus, a given unit/component may be said to be configured to perform a task even when the unit/component is not currently operating (e.g., not turned on/active). Detailed description a unit/circuit/component "configured to" perform one or more tasks is expressly intended to mean that 35u.s.c. § 112, sixth paragraph, is not applied to that unit/component.

As used herein, the terms "first," "second," and the like are used as labels to follow a noun without implying any type of order (e.g., spatial, temporal, logical, etc.). For example, reference to a "first" solar cell does not necessarily imply that the solar cell is the first solar cell in a sequence; rather, the term "first" is used to distinguish the solar cell from another solar cell (e.g., a "second" solar cell).

"coupled" — the following description refers to elements or nodes or features being "coupled" together. As used herein, unless expressly stated otherwise, "coupled" means that one element/node/feature is directly or indirectly connected to (or directly or indirectly communicates with) another element/node/feature, and not necessarily mechanically.

Furthermore, certain terminology is also used in the following description for the purpose of reference only, and thus, is not intended to be limiting. For example, terms such as "upper," "lower," "above," or "below" refer to the orientation in which reference is made in the drawings. Terms such as "front," "back," "rear," "side," "outboard," and "inboard" describe the orientation and/or position of certain parts of the component within a consistent but arbitrary frame of reference as may be clearly understood by reference to the text and associated drawings describing the component in question. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import.

Although much of the disclosure is described in terms of solar cells for ease of understanding, the techniques and structures disclosed herein are equally applicable to other semiconductor structures (e.g., silicon wafers in general).

The formation of metal regions, such as the formation of positive and negative bus bars and contact fingers to doped regions on a solar cell, can be a challenging process. The techniques and structures disclosed herein improve the accuracy, throughput, and cost of the associated manufacturing processes.

In the present disclosure, numerous specific details are provided, such as examples of structures and methods, to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the embodiments can be practiced without one or more of the specific details. In other instances, well-known details are not shown or described to avoid obscuring aspects of the embodiments.

Fig. 1 shows a flow chart of an embodiment of an exemplary method of manufacturing a solar cell. In various embodiments, the method of fig. 1 may include additional (or fewer) blocks than shown. For example, in one embodiment, a partial removal of the dielectric region on a particular region, block 104, may not be performed. The method of fig. 1 may also be performed on a solar cell structure having N-type and P-type doped regions. It is noted that the method of fig. 1 may be performed at the unit level during solar cell manufacturing, or at the module level when the solar cell is connected or packaged with other solar cells.

As shown at 102, a dielectric region, which may also be referred to as a dielectric layer, may be formed on a surface of the solar cell structure. In an embodiment, a dielectric region may be formed over an N-type doped region and a P-type doped region of a solar cell structure. In one embodiment, the dielectric region is a continuous conformal layer formed by blanket deposition. In embodiments, the dielectric region may be formed by, for example, screen printing, spin coating, or by deposition and patterning such that the dielectric region is discontinuous. In embodiments, the dielectric region may comprise silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, amorphous silicon, or polysilicon.

At 104, the dielectric region may be partially removed to expose/form the contact region. In an embodiment, the contact region may allow for the formation of a contact (such as an ohmic contact). In an embodiment, the dielectric region is partially removed on a specific region, wherein the specific region is aligned over an N-type doped region or a P-type doped region of the solar cell structure. As noted above, in some embodiments, block 104 may not be performed, and thus the dielectric region may not be partially removed.

At 106, a first metal layer may be formed on the dielectric region. In one embodiment, the first metal layer is a continuous conformal layer formed by blanket deposition. In another embodiment, the first metal layer is non-continuous (e.g., printed or deposited in a particular pattern and subsequently etched into the particular pattern). In an embodiment, forming the metal layer may include performing a physical vapor deposition, screen printing, sintering, plating, or laser transfer process. In an embodiment, the first metal layer may also be referred to as a seed metal layer. In an embodiment, forming the first metal layer may include depositing a seed metal layer on the dielectric region. In an embodiment, the first metal layer may include a metal such as, but not limited to, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, or platinum, and alloys thereof. In an embodiment, the first metal layer may be a patterned metal layer, such as a first patterned metal layer. In an embodiment, the first patterned metal layer may be disposed, deposited, or aligned on the dielectric region.

A second metal layer may be formed on the first metal layer, as shown at 108. In one embodiment, the second metal layer is a continuous conformal layer formed by blanket deposition. In an embodiment, the second metal layer may comprise a metal foil. In an embodiment, the second metal layer may include a metal such as, but not limited to, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, or platinum, and alloys thereof. In an embodiment, the second metal layer may be a patterned metal layer, such as a second patterned metal layer (e.g., a patterned metal foil). In embodiments, a second patterned metal layer may be disposed, deposited, or aligned on the dielectric region.

At 110, the metal bond and the contact may be formed in a single process. In an embodiment, forming the metal bond and the contact in a single process includes locally heating a particular region of the second metal layer. In an embodiment, locally heating a specific region of the second metal layer allows heat transfer from the second metal layer to the specific region between both the first metal layer and the second metal layer, and subsequently, the heat is further transferred through the first metal layer to the specific region between the first metal layer and the dielectric region, thereby forming a contact. In an embodiment, the formed metal bond may electrically and mechanically couple the second metal layer to the first metal layer. In an embodiment, the contact may electrically and mechanically couple the first metal layer to the solar cell structure.

In one embodiment, locally heating includes directing a laser beam onto the second metal layer. In an embodiment, directing a laser beam onto the second metal layer may weld the second metal layer to the first metal layer. In an embodiment, the laser beam may have a pulse duration in a range of 1 nanosecond to 10 milliseconds. In an embodiment, the laser beam may be generated using a Continuous Wave (CW) laser or a pulsed laser. In an embodiment, the laser beam has a wavelength in a range of 100 nanometers to 12 micrometers. In an embodiment, a laser beam may be directed onto the metal foil to form a metal bond with a seed metal layer, and further to form an ohmic contact between the seed metal layer and the solar cell structure. In an embodiment, the metal bond and the ohmic contact are aligned with a specific region of the solar cell structure. In embodiments, a specific region of the solar cell may be aligned to a P-type doped region or an N-type doped region. In an embodiment, the second metal layer or metal foil may be a patterned metal foil (e.g., in a finger pattern, such as an interdigitated finger pattern). In an embodiment, a patterned metal foil may be disposed on the seed metal layer. It is noted that in some embodiments, the metal bond and the contact may be formed in a single process using a welding technique that is not laser based. In an embodiment, portions of the first and second metal layers may be removed in a criss-cross pattern prior to the local heating.

The above embodiments may be performed for a plurality of solar cells. For example, in one embodiment, a metal foil (e.g., a finger corresponding to and/or including a plurality of cells) can be aligned and placed over the first solar cell and the second solar cell. The metal foil may then be coupled to both the first and second solar cells according to the method of fig. 1.

Fig. 2 to 7 are cross-sectional views schematically illustrating a method of manufacturing a solar cell according to an embodiment of the present disclosure.

Referring to fig. 2, a solar cell is shown during a manufacturing process, the solar cell comprising a second metal layer 232 disposed on a first metal layer 230, wherein the first metal layer 230 is disposed on a solar cell structure 200. In an embodiment, first metal layer 230 may have a thickness in a range of 1 to 5 microns, for example first metal layer 230 may be in a range of approximately 1 to 2 microns. In an embodiment, the second metal layer 232 may have a thickness in a range of 1 to 100 microns (e.g., metal foil), for example the second metal layer 232 may be about 50 microns. As shown, solar cell structure 200 can include silicon substrate 208, first doped region 210 or second doped region 212, and dielectric region 220. The solar cell of fig. 2 may also include a front side 204 configured to face the sun during normal operation of the solar cell and a back side 202 opposite the front side 204. As described above, the first metal layer 230 or the second metal layer 232 may include a metal such as, but not limited to, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, or platinum, and alloys thereof. In an embodiment, the dielectric region 220 may comprise silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, amorphous silicon, or polysilicon. In an embodiment, first doped region 210 or second doped region 212 can comprise a P-type doped region or an N-type doped region of silicon substrate 208.

Fig. 3 illustrates the localized heating of the second metal layer 232. In an embodiment, a laser beam 262 from a laser source 260 may be used to perform localized heating of a particular region of the second metal layer 232. In an embodiment, the electron beam may be used to perform local heating on a specific region of the second metal layer 232. Subsequently, heat 264 from the laser beam 262 is transferred to the second metal layer 232. In embodiments, laser beam 262 may be directed to second metal layer 232 using a galvanometer, a scanning stage, or using conventional optical interfacing and control equipment, systems, and processes.

Referring to fig. 4, the formation of a metal bond 242 is shown. In an embodiment, heat 264 from the laser beam 262 is transferred through the second metal layer 232 to the region between the first metal layer 230 and the second metal layer 232, thereby forming the metal bond 242, wherein the metal bond 242 allows for electrical connection between the first metal layer 230 and the second metal layer 232. In an embodiment, the second metal layer may be partially removed or melted due to the heat 264, as shown in fig. 4. In an embodiment, the metal bond 242 may mechanically couple the second metal layer 232 to the first metal layer 230.

Fig. 5 illustrates the formation of contacts 240. In an embodiment, heat 264 from the laser beam 262 is further transferred through the first metal layer 230 to the region between the first metal layer 230 and the doped

regions

210, 212, wherein the heat 264 forms the contact 240, thereby allowing electrical connection between the first metal layer 230 and the doped

regions

210, 212. As described above, the contact 240 may be an ohmic contact. In an embodiment, during the above-described process, the dielectric region 220 may not separate, allowing the electrical connection between the first metal layer 230 and the doped

regions

210, 212 to be substantially complete (e.g., continuous), with the dielectric region 220 between the first metal layer 230 and the doped

regions

210, 212. In an embodiment, the contact 240 may mechanically couple the first metal layer 230 to the solar cell structure 200.

In an embodiment, the steps shown in fig. 3, 4, and 5 may all be performed in a single process. Changing the characteristics of the tool (e.g., laser) used to perform the process may be included in a single process. For example, the initial laser pulse may be a higher power pulse to perform one of the bonds, and then changed to a lower power pulse to form another bond. Laser characteristics/configuration changes other than power may include pulse duration, pulse shape, wavelength, and the like. When the steps of fig. 3-5 are performed in a single process, multiple fabrication steps may be removed, i.e., to separately form the metal bond and ohmic contact, thereby improving solar cell fabrication efficiency and reducing cost.

Referring to fig. 6, a solar cell is shown after the single-step process performed in fig. 3-5. The solar cell of fig. 6 may include a front side 204 configured to face the sun during normal operation of the solar cell and a back side 202 opposite the front side. As shown, the solar cell may include a solar cell structure 200. Solar cell structure 200 can include a silicon substrate 208, first and second

doped regions

210 and 212, and a dielectric region 220. In an embodiment, the dielectric region 220 may be formed between two contacts 240. The solar cell structure 200 is coupled to the first metal layer 230 through a contact 240, such as an ohmic contact. In an embodiment, the contact 240 may mechanically couple the first metal layer 230 to the solar cell structure 200. The first metal layer 230 is coupled to the second metal layer 232 by a metal bond 242. In an embodiment, the metal bond 242 may mechanically couple the second metal layer 232 to the first metal layer 230. The fingers formed by first metal layer 230 and second metal layer 232 are separated by a spacing 234. Note that electrical connections at pitch 234 can allow for electrical shorts and can be detrimental to the performance of the solar cell. The gaps or spaces 234 may be formed by a laser ablation process or an etching process to remove excess metal from the first and

second metal layers

230 and 232. In an embodiment, the first doped region and the second doped region may be a P-type doped region and an N-type doped region, respectively. In an embodiment, the dielectric region 220 may be patterned such that some regions do not have a dielectric region under the first metal layer 230. In an embodiment, first metal layer 230 may have a thickness in a range of 1 to 5 microns, for example first metal layer 230 may be in a range of approximately 1 to 2 microns. In an embodiment, the second metal layer 232 may have a thickness in a range of 1 to 100 microns (e.g., metal foil), for example the second metal layer 232 may be about 50 microns.

Fig. 7 shows

exemplary metal layers

250, 252. In an embodiment, the metal layers 230, 232 (from fig. 2-6 above) may be formed as metal strips 250, as shown. In an embodiment, a plurality of metal strips 250 may be used to form a crisscross pattern. In an embodiment, the crossing pattern may include positive contact fingers, negative contact fingers, positive bus bars, and negative bus bars. In an embodiment, the metal layers 230, 232 may be formed in a circular or dot pattern 252. There is no limitation on the patterns that the metal layers 230, 232 may be formed in, and fig. 7 illustrates only some of the possible patterns that may be used. The front 204 and back 202 sides of the solar cell are shown for reference.

Referring to fig. 8, a flow diagram of an embodiment of another exemplary method of manufacturing a solar cell is shown. In various embodiments, the method of fig. 8 may include additional (or fewer) blocks than shown. The method of fig. 8 may also be performed on a solar cell structure having N-type and P-type doped regions. Similar to the above, the method of fig. 8 may be performed at the unit level during solar cell manufacturing, or at the module level when solar cells are connected or packaged together with other solar cells.

As shown at 302, a dielectric region, which may also be referred to as a dielectric layer, may be formed on a surface of the solar cell structure. In an embodiment, a dielectric region may be formed over an N-type doped region and a P-type doped region of a solar cell structure. In one embodiment, the dielectric region is a continuous conformal layer formed by blanket deposition. The dielectric regions may be formed, for example, by screen printing, spin coating, or by deposition and patterning such that the dielectric regions are discontinuous. In embodiments, the dielectric region may comprise silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, amorphous silicon, or polysilicon. In an embodiment, the dielectric region may be partially removed to expose/form the contact region. In an embodiment, the contact region may allow for the formation of a contact (such as an ohmic contact). In an embodiment, the dielectric region is partially removed on a specific region, wherein the specific region is aligned over an N-type doped region or a P-type doped region of the solar cell structure. As noted above, in some embodiments, the dielectric region may not be partially removed.

At 304, a first metal layer may be formed on the dielectric region. In one embodiment, the first metal layer is a continuous conformal layer formed by blanket deposition. In another embodiment, the first metal layer is non-continuous (e.g., printed or deposited in a particular pattern and subsequently etched into the particular pattern). In an embodiment, forming the metal layer may include performing a physical vapor deposition, screen printing, sintering, plating, or laser transfer process. In an embodiment, the first metal layer may also be referred to as a seed metal layer. In an embodiment, the first metal layer may comprise a metal foil. In an embodiment, forming the first metal layer may include depositing a seed metal layer on the dielectric region. In an embodiment, the first metal layer may include a metal such as, but not limited to, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, or platinum, and alloys thereof. In an embodiment, the first metal layer may comprise a patterned metal layer, such as a first patterned metal layer. In an embodiment, the first patterned metal layer may be disposed, deposited, or aligned on the dielectric region.

At 306, an adhesive layer may be formed on the first metal layer, and in some embodiments, additionally on the dielectric region (e.g., filling gaps between patterned first metal layers). In embodiments, the adhesive layer may be formed by, for example, screen printing, ink jet printing, spin coating, casting, lamination, or by deposition and patterning. In an embodiment, the adhesive layer may be formed by a Chemical Vapor Deposition (CVD) or Physical Vapor Deposition (PVD) method. In an embodiment, the adhesive layer may be an insulating adhesive layer. In an embodiment, the adhesive layer may be a uniform, low viscosity adhesive layer. In embodiments, the adhesive layer may be patterned, either as it is formed or formed and then patterned (e.g., etched). In an embodiment, forming the adhesive layer may include forming a conductive adhesive layer. In an embodiment, forming the adhesive layer may include forming an anisotropic conductive adhesive layer.

A second metal layer may be formed on the adhesive layer, as shown at 308. In one embodiment, the second metal layer is a continuous conformal layer formed by blanket deposition. In an embodiment, the adhesive layer may provide structural support, mechanically coupling the second metal layer to the first metal layer, and may also allow the second metal layer to be electrically connected with the first metal layer. In an embodiment, the second metal layer may comprise a metal foil. In an embodiment, the second metal layer may include a metal such as, but not limited to, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, or platinum, and alloys thereof. In an embodiment, the second metal layer may comprise a patterned metal layer, such as a second patterned metal layer (e.g., a patterned metal foil). Note that in embodiments, forming the first metal layer may include any of the blocks described above. The use of a patterned adhesive layer may allow the second metal layer to be formed using a direct Physical Vapor Deposition (PVD) process. In an embodiment, the adhesive layer may be cured after the formation of the second metal layer. In an embodiment, forming the second metal layer may include forming a metal foil on the adhesive layer. In an embodiment, the direct contact between the first metal layer and the second metal layer may be performed by applying pressure to the second metal layer (e.g., by vacuum, roller, squeegee, etc.).

Similar to the above, metal bonds and contacts may be formed. In embodiments, the metal bond and the contact may be formed separately or in a single step process as described above.

The above embodiments may be performed for a plurality of solar cells. For example, in one embodiment, a metal foil (e.g., a finger comprising a plurality of cells) can be aligned and disposed on a first solar cell and a second solar cell. The metal foil may then be coupled to both the first solar cell and the second solar cell. In addition, the above may be performed for various types of solar cells, such as front-contact solar cells and back-contact solar cells.

Fig. 9 to 12 are cross-sectional views schematically illustrating a method of manufacturing a solar cell according to an embodiment of the present disclosure. Unless otherwise indicated below, the numerical designations used to refer to components in fig. 9-12 are similar to the numerical designations used to refer to components or features in fig. 2-7 above, except that the reference numerals are increased by 200.

Fig. 9 shows the solar cell during the above-described manufacturing process. The solar cell of fig. 9 includes an adhesive layer 470 formed on the first metal layer 430, wherein the first metal layer 430 is disposed on the solar cell structure 400. In embodiments, adhesive layer 470 may be formed by screen printing, ink jet printing, spin coating, casting, lamination, or by deposition (CVD or PVD) and patterning. As shown, the solar cell structure 400 can include a silicon substrate 408, a first doped region 410 or a second doped region 412, and a dielectric region 420. In an embodiment, the first metal layer 430 may also be referred to as a seed metal layer. In an embodiment, forming first metal layer 430 may include depositing a seed metal layer on dielectric region 420. In an embodiment, first metal layer 430 may include a metal such as, but not limited to, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, or platinum, and alloys thereof. In an embodiment, the first metal layer 430 may include a patterned metal layer, such as a first patterned metal layer (e.g., a patterned metal foil). In an embodiment, forming the first metal layer 430 may include disposing a patterned metal layer on the dielectric region 420, the metal layer 430 separated by a gap 474, wherein the gap 474 may separate the positive and negative contact fingers. In an embodiment, a laser ablation process may be performed to form the patterned metal layer. In an embodiment, the gap 474 may be formed by laser ablation or etching. In embodiments, the dielectric region 420 may comprise silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, amorphous silicon, or polysilicon. In an embodiment, the first doped region 410 or the second doped region 412 can comprise a P-type doped region or an N-type doped region of the silicon substrate 408. As described above, the adhesive layer 470 may be an insulating adhesive layer. In an embodiment, the adhesive layer 470 may be a uniform, low viscosity adhesive layer. In an embodiment, the adhesive layer 470 may be a patterned adhesive layer. In an embodiment, forming the adhesive layer 470 may include forming an anisotropic conductive adhesive layer.

Fig. 10 shows a second metal layer 432 disposed on an adhesive layer 470. In an embodiment, adhesive layer 470 may provide structural support, mechanically coupling second metal layer 432 to first metal layer 430. In an embodiment, the second metal layer 432 may comprise a metal foil. In an embodiment, the second metal layer 432 may include a metal such as, but not limited to, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, or platinum, and alloys thereof. In an embodiment, the second metal layer 432 may comprise a patterned metal layer, such as a second patterned metal layer. In an embodiment, forming the second metal layer 432 may include disposing a patterned metal layer on the adhesive layer 470. In an embodiment, the adhesive layer 470 may be cured after the second metal layer 432 is formed. In an embodiment, forming the second metal layer 432 may include forming a metal foil on the adhesive layer 470. If a patterned adhesive layer is provided, such as shown at 470 in fig. 10, embodiments may include curing the patterned adhesive layer prior to forming the second metal layer 432. In an embodiment, forming a patterned adhesive layer may allow second metal layer 432 to be formed using a direct Physical Vapor Deposition (PVD) process. In an embodiment, the patterned adhesive layer may be formed such that openings may be allowed within the patterned adhesive layer so that second metal layer 432 contacts first metal layer 430, further allowing embodiments similar to the PVD process described to form second metal layer 432 on first metal layer 430. In addition, patterning the adhesive layer may allow the second metal layer 432 to be electrically connected with the first metal layer 430. In an embodiment, the adhesive layer 470 may be cured to form a cured adhesive layer. In an embodiment, forming the second metal layer 432 may include forming a metal foil on the adhesive layer 470. In an embodiment, direct contact between the first metal layer 430 and the second metal layer 432 may be performed by applying pressure to the second metal layer 432.

Referring to fig. 11, the solar cell is shown after the process performed in fig. 9 and 10. The solar cell of fig. 11 may include a front side 404 configured to face the sun during normal operation of the solar cell and a back side 402 opposite the front side. As shown, the solar cell of fig. 11 includes a solar cell structure 400. The solar cell structure 400 can include a silicon substrate 408, first and second

doped regions

410, 412, and a dielectric region 420. The solar cell structure 400 is coupled to the first metal layer 430 by a contact 440, such as an ohmic contact. In an embodiment, the contact 440 may mechanically couple the first metal layer 430 to the solar cell structure 400. The first metal layer 430 is coupled to the second metal layer 432 through a metal bond 442. In an embodiment, the metal bond 442 may mechanically couple the second metal layer 432 to the first metal layer 430. The fingers formed by the first metal layer 430 and the second metal layer 432 are separated 474. Any electrical connection at spacing 474 may allow for an electrical short and be detrimental to the performance of the solar cell. The gaps or spaces 474 may be formed by an etching process or via a laser ablation process, wherein excess metal may be removed from the first and second metal layers 430, 432. In an embodiment, the first and second

doped regions

410 and 412 may be P-type and N-type doped regions. The solar cell of fig. 11 includes a metal bond 442 and a contact 440. In an embodiment, the metal bond 442 and the contact 440 may be formed separately using a laser welding process or in a single step process as described above. In an embodiment, the contact 440 may be an ohmic contact. In an embodiment, the metal bonds 442 and contacts 440 may be formed using any of the methods described above. In an embodiment, the dielectric region 420 may be patterned such that some regions do not have a dielectric region under the first metal layer 430. In an embodiment, first metal layer 430 may have a thickness in a range of 1 to 5 microns, for example first metal layer 430 may be in a range of approximately 1 to 2 microns. In an embodiment, the second metal layer 432 may have a thickness in a range of 1 to 100 microns (e.g., metal foil), for example the second metal layer 432 may be about 50 microns.

Fig. 12 shows another solar cell after the process performed in fig. 9 and 10. The solar cell of fig. 12 may include a front side 404 configured to face the sun during normal operation of the solar cell and a back side 402 opposite the front side. As shown, the solar cell may include a solar cell structure 400. The solar cell structure 400 can include a silicon substrate 408, first and second

doped regions

410, 412, and a dielectric region 420. In one embodiment, the first metal layer 431 is composed of a plurality of metal particles. In an embodiment, the plurality of metal particles comprises aluminum particles. In an embodiment, the solar cell structure 400 may be coupled to the first metal layer 431 through a contact 440, such as an ohmic contact. In an embodiment, the contact 440 may mechanically couple the first metal layer 431 to the solar cell structure 400. In one embodiment, the first metal layer 431 is electrically connected with the second metal layer 432, wherein an adhesive layer, such as a cured adhesive layer 472, allows for electrical connection without a metal bond or solder. In an embodiment, adhesive layer 472 may mechanically couple second metal layer 432 to first metal layer 430. The fingers formed by the first metal layer 430 and the second metal layer 432 are separated 474. Any electrical connection at spacing 474 may allow for an electrical short and be detrimental to the performance of the solar cell. Gaps or spaces 474 may be formed by a laser ablation process or by etching, removing excess metal from first metal layer 430 and second metal layer 432. In an embodiment, the first doped region 410 and the second doped region 412 may be a P-type doped region and an N-type doped region, respectively. In an embodiment, the dielectric region 420 may be patterned such that some regions do not have a dielectric region under the first metal layer 430. In an embodiment, the first metal layer 431 may have a thickness in a range of 1 to 5 microns, for example, the first metal layer 431 may be in a range of about 1 to 2 microns. In an embodiment, the second metal layer 432 may have a thickness in a range of 1 to 100 microns (e.g., metal foil), for example the second metal layer 432 may be about 50 microns.

Note that while the examples of fig. 9-12 show the first metal layer being patterned before the adhesive layer and the second metal layer are formed on top of the first metal layer, in other embodiments, the second metal layer may be formed on top of the adhesive layer and the first metal layer. In various embodiments, the patterning can occur after the first metal layer is formed, after the first metal layer and the adhesive layer are formed, after all three layers are formed, or at various stages in the process (e.g., after the first metal layer is formed, and then also after the adhesive layer and the second metal layer are formed).

Referring to fig. 13, a flow diagram of an embodiment of yet another exemplary method of manufacturing a solar cell is shown. In various embodiments, the method of FIG. 13 may include additional (or fewer) blocks than shown. For example, in one embodiment, partial removal of the dielectric region need not be performed, block 504. The method of fig. 13 may also be performed on a solar cell structure having N-type and P-type doped regions. Similar to the above, the method of fig. 13 may be performed at the unit level during solar cell manufacturing, or at the module level when solar cells are connected or packaged together with other solar cells.

As shown at 502, a dielectric region, which may also be referred to as a dielectric layer, may be formed on a surface of a solar cell structure. In an embodiment, a dielectric region may be formed over an N-type doped region and a P-type doped region of a solar cell structure. In one embodiment, the dielectric region is a continuous conformal layer formed by blanket deposition. The dielectric region may be formed by any of the methods described above, such as screen printing, spin coating, or by deposition and patterning, such that the dielectric region is discontinuous. In embodiments, the dielectric region may comprise silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, amorphous silicon, or polysilicon. In an embodiment, the dielectric region may be partially removed from the dielectric region, thereby forming a contact region. In an embodiment, the contact region may allow for the formation of a contact (such as an ohmic contact).

At 504, the dielectric region may be partially removed to expose/form the contact region. In an embodiment, the contact region may allow for the formation of a contact (such as an ohmic contact). In an embodiment, the dielectric region is partially removed on a specific region, wherein the specific region is aligned over an N-type doped region or a P-type doped region of the solar cell structure. As noted above, in some embodiments, block 504 may not be performed, and thus the dielectric region may not be partially removed.

At 506, a first metal layer may be formed on the dielectric region. In an embodiment, the first metal layer is a first patterned metal layer, and the first patterned metal layer may be disposed on the dielectric region. It is noted that in one embodiment, the metal layer may be patterned after its application/formation, while in other embodiments, the metal layer may be applied in a particular pattern. In one embodiment, the first metal layer is a continuous conformal layer formed by blanket deposition. In an embodiment, forming the metal layer may include performing a physical vapor deposition, screen printing, sintering, plating, or laser transfer process. In an embodiment, the first metal layer may also be referred to as a seed metal layer. In an embodiment, forming the first metal layer may include depositing a seed metal layer on the dielectric region. In an embodiment, the first metal layer may include a metal such as, but not limited to, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, or platinum, and alloys thereof. In an embodiment, a laser ablation process or etch may be performed to form the first patterned metal layer.

At 508, an adhesive layer may be formed on the first metal layer and on the dielectric region. In an embodiment, the adhesive layer may be an insulating adhesive layer. In embodiments, the adhesive layer may be formed by, for example, screen printing, ink jet printing, spin coating, casting, lamination, or by deposition and patterning. In an embodiment, the adhesive layer may be formed by a Chemical Vapor Deposition (CVD) or Physical Vapor Deposition (PVD) method. In an embodiment, the adhesive layer may be a uniform, low viscosity adhesive layer. In an embodiment, the adhesive layer may be a patterned adhesive layer. In an embodiment, forming the adhesive layer may include forming a conductive adhesive layer. In an embodiment, forming the adhesive layer may include forming an anisotropic conductive adhesive layer. In embodiments, the adhesive layer may provide additional structural support, such as mechanically coupling the second metal layer to the first metal layer.

As shown at 510, a second metal layer may be formed on the adhesive layer. In an embodiment, the adhesive layer may provide structural support, mechanically coupling the second metal layer to the first metal layer. In one embodiment, the second metal layer is a continuous conformal layer formed by blanket deposition. In an embodiment, the second metal layer may comprise a metal foil. In an embodiment, the second metal layer may include a metal such as, but not limited to, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, or platinum, and alloys thereof. In an embodiment, the adhesive layer may be cured after the formation of the second metal layer. In an embodiment, forming the second metal layer may include forming a metal foil on the adhesive layer.

At 512, metal bonds and contacts may be formed by localized heating of particular areas on the second metal layer. In an embodiment, locally heating a specific region of the second metal layer allows heat transfer from the second metal layer to the specific region between both the first metal layer and the second metal layer, thereby forming a metal bond. Subsequently, the heat may be further transferred through the first metal layer to a specific region between the first metal layer and the dielectric region, thereby forming a contact. In an embodiment, locally heating comprises directing a laser beam onto the second metal layer. In embodiments, the metal bond and the contact may be formed using any of the methods described above, either individually or in a single step process. In an embodiment, the formed metal bond may electrically and mechanically couple the second metal layer to the first metal layer. In an embodiment, the contact may electrically and mechanically couple the first metal layer to the solar cell structure.

At 514, metal from the second metal layer may be partially removed to form a second patterned metal layer. In an embodiment, the adhesive layer, or insulating adhesive layer, protects the solar cell structure from damage during the partial removal process. In an embodiment, the excess metal may be removed from the second metal layer using a laser ablation process. In an embodiment, the adhesive layer absorbs excess laser radiation from the laser beam, thereby protecting the dielectric region and the solar cell structure from damage. In an embodiment, the adhesive layer may be a thermal insulating layer that is not damaged by the laser, and an electrically insulating layer between the first metal layer and the second metal layer. In an embodiment, the excess metal may be removed using an etching process.

Fig. 14 to 19 are cross-sectional views schematically illustrating a method of manufacturing a solar cell according to an embodiment of the present disclosure. Unless otherwise indicated below, the numerical designations used to refer to components in fig. 14-19 are similar to the numerical designations used to refer to components or features in fig. 9-12 above, except that the reference numerals are increased by 200.

Fig. 14 shows the solar cell during the above-described manufacturing process. The solar cell of fig. 14 includes an adhesive layer 670 formed on the first metal layer 630 and the dielectric region 620, wherein the first metal layer 630 is disposed on the solar cell structure 600. In embodiments, adhesive layer 670 may be formed by screen printing, ink jet printing, spin coating, casting, lamination, or by deposition (CVD or PVD) and patterning. As shown, the solar cell structure 600 can include a silicon substrate 608, a first doped region 610 or a second doped region 612, and a dielectric region 620. In an embodiment, the first metal layer 630 may also be referred to as a seed metal layer. In an embodiment, forming the first metal layer 630 may include depositing a seed metal layer on the dielectric region 620. In an embodiment, the first metal layer 630 may include a metal such as, but not limited to, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, or platinum, and alloys thereof. In an embodiment, the first metal layer 630 may include a patterned metal layer, such as a first patterned metal layer. In an embodiment, forming the first metal layer 630 may include disposing a patterned metal layer on the dielectric region 620. In an embodiment, a laser ablation process may be performed to form the patterned metal layer. In an embodiment, the dielectric region 620 may comprise silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, amorphous silicon, or polysilicon. In an embodiment, the first doped region 610 or the second doped region 612 can comprise a P-type doped region or an N-type doped region of the silicon substrate 608. As described above, the adhesive layer 670 may be an insulating adhesive layer. In an embodiment, the adhesive layer 670 may be a uniform low viscosity adhesive layer. In an embodiment, forming the adhesive layer 670 may include forming an anisotropic conductive adhesive layer.

Referring to fig. 15, a second metal layer 632 is shown disposed on an adhesive layer 670. In an embodiment, the adhesive layer 670 may provide structural support, mechanically coupling the second metal layer 632 to the first metal layer 630. In an embodiment, the second metal layer 632 may comprise a metal foil. In an embodiment, the second metal layer 632 may include a metal such as, but not limited to, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, or platinum, and alloys thereof. In an embodiment, the adhesive layer 670 may be cured 680 after the second metal layer 632 is formed. In an embodiment, curing may include heating the adhesive layer 670. In an embodiment, curing may form a cured adhesive layer 672, as shown in fig. 16. In an embodiment, forming the second metal layer 632 may include forming a metal foil on the adhesive layer 670. In an embodiment, direct contact between the first metal layer 630 and the second metal layer 632 may be performed by applying pressure to the second metal layer 632.

Fig. 16 shows cured adhesive layer 672, metal bond 642, and contact 640. In embodiments, the metal bond 642 and the contact 640 may be formed separately or in a single step process as described above.

Referring to fig. 17, metal from the second metal layer 632 may be partially removed to form a second patterned metallization layer. In an embodiment, the adhesive layer, cured adhesive layer 672, or insulating adhesive layer protects the solar cell structure 600 from damage during the process of partially removing the second metal layer 632. In an embodiment, the excess metal may be removed from the second metal layer 632 using a laser ablation process. In an embodiment, the adhesive layer or cured adhesive layer 672 absorbs excess laser radiation from the laser beam 662 of the laser source 660, thereby protecting the dielectric region 620 and the solar cell structure 600 from damage. In an embodiment, the adhesive layer may be a thermal barrier layer (i.e., not damaged by the laser, as shown), as well as an electrically insulating layer.

Fig. 18 shows the solar cell after the processes performed in fig. 14 to 17. The solar cell of fig. 18 can include a front side 604 configured to face the sun during normal operation of the solar cell and a back side 602 opposite the front side. As shown, the solar cell of fig. 18 includes a solar cell structure 600. The solar cell structure 600 can include a silicon substrate 608, first and second

doped regions

610, 612, and a dielectric region 620. The solar cell structure 600 is coupled to the first metal layer 630 through a contact 640, such as an ohmic contact. In an embodiment, the contact 640 may mechanically couple the first metal layer 630 to the solar cell structure 600. First metal layer 630 is coupled to second metal layer 632 by metal bond 642. In an embodiment, metal bond 642 may mechanically couple second metal layer 632 to first metal layer 630. The fingers formed by the first metal layer 630 and the second metal layer 632 are separated. An adhesive layer, such as cured adhesive layer 672, may be interposed between the fingers and the electrically insulative fingers of opposite polarity. In an embodiment, the first doped region 610 and the second doped region 612 may be a P-type doped region and an N-type doped region. The solar cell of fig. 18 includes a metal bond 642 and a contact 640. In an embodiment, metal bond 642 and contact 440 may be formed separately using a laser welding process or in a single step process as described above. In an embodiment, the contact 640 may be an ohmic contact. In an embodiment, the dielectric regions 620 may be patterned such that some regions do not have dielectric regions under the first metal layer 630. In an embodiment, the first metal layer 630 may have a thickness in a range of 1 to 5 microns, for example, the first metal layer 630 may be in a range of about 1 to 2 microns. In an embodiment, the second metal layer 632 may have a thickness in a range of 1 to 100 microns (e.g., metal foil), for example the second metal layer 632 may be about 50 microns.

Referring to fig. 19, another solar cell is shown after the process performed in fig. 14-17. The solar cell of fig. 19 can include a front side 604 configured to face the sun during normal operation of the solar cell and a back side 602 opposite the front side. As shown, the solar cell may include a solar cell structure 600. The solar cell structure 600 can include a silicon substrate 608, first and second

doped regions

610, 612, and a dielectric region 620. In one embodiment, the first metal layer 631 is composed of a plurality of metal particles. In an embodiment, the plurality of metal particles may include aluminum particles. In an embodiment, the solar cell structure 600 may be coupled to the first metal layer 631 by a contact 640, such as an ohmic contact. In an embodiment, the contact 640 may mechanically couple the first metal layer 630 to the solar cell structure 600. In one embodiment, the first metal layer 631 is electrically connected with the second metal layer 632, wherein an adhesive layer, such as cured adhesive layer 672, allows electrical connection without metal bonding or soldering. In an embodiment, an adhesive layer may mechanically couple the second metal layer 632 to the first metal layer 630. The fingers formed by the first metal layer 630 and the second metal layer 632 are separated. An adhesive layer, such as cured adhesive layer 672, may be an electrically insulating finger of opposite polarity. In an embodiment, the first doped region 610 and the second doped region 612 may be a P-type doped region and an N-type doped region. In an embodiment, the dielectric region 620 may be patterned such that some regions do not have a dielectric region under the first metal layer 631. In an embodiment, the first metal layer 631 may have a thickness in a range of 1 to 5 micrometers, for example, the first metal layer 631 may be in a range of about 1 to 2 micrometers. In an embodiment, the second metal layer 632 may have a thickness in a range of 1 to 100 microns (e.g., metal foil), for example the second metal layer 632 may be about 50 microns.

The above embodiments may be performed for a plurality of solar cells (e.g., a finger including a plurality of cells). In addition, the above may be performed for various types of solar cells, such as front-contact solar cells and back-contact solar cells.

While the foregoing detailed description has set forth at least one exemplary embodiment, it should be understood that numerous variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments described herein are not intended to limit the scope, applicability, or configuration of the claimed subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope as defined in the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application.

In an embodiment, a method of fabricating a solar cell involves forming a dielectric region on a surface of a solar cell structure, forming a first metal layer on the dielectric region, forming a second metal layer on the first metal layer, and locally heating a particular region of the second metal layer, wherein heating includes forming a metal bond between the first metal layer and the second metal layer and forming a contact between the first metal layer and the solar cell structure.

In one embodiment, the localized heating package directs a laser beam onto the second metal layer.

In one embodiment, directing the laser beam includes directing the laser beam with a pulse duration in a range of 1 nanosecond to 10 milliseconds.

In one embodiment, directing the laser beam includes using a laser selected from a Continuous Wave (CW) laser and a pulsed laser.

In one embodiment, the laser beam comprises a wavelength in a range of 100 nanometers to 12 micrometers.

In one embodiment, the method involves partially removing the dielectric region in the region corresponding to the contact between the first metal layer and the solar cell structure prior to forming the first metal layer.

In one embodiment, partially removing the dielectric region includes performing a laser ablation process.

In one embodiment, forming the contact includes forming an ohmic contact between the first metal layer and the solar cell structure.

In one embodiment, forming the first metal layer includes performing a method selected from the group consisting of physical vapor deposition, screen printing, plating, sintering, and laser transfer.

In one embodiment, forming the first metal layer includes depositing a seed metal layer on the dielectric region.

In one embodiment, forming the second metal layer includes disposing a patterned metal layer on the first metal layer.

In one embodiment, forming the second metal layer includes disposing a metal foil on the first metal layer.

In one embodiment, the method further involves partially removing portions of the first metal layer and the second metal layer in an interdigitated pattern prior to locally heating the particular region of the second metal layer.

In an embodiment, a method of fabricating a solar cell involves forming a dielectric region on a surface of a solar cell structure, forming a first metal layer on the dielectric region, an N-type doped region, and a P-type doped region, forming a second metal layer on the first metal layer, and directing a laser beam onto a particular region of the second metal layer, wherein directing the laser beam includes forming a metal bond between the first metal layer and the second metal layer and forming an ohmic contact between the first metal layer and the solar cell structure.

In one embodiment, the method involves partially removing the dielectric region in a region corresponding to an ohmic contact between the first metal layer and the solar cell structure prior to forming the first metal layer.

In an embodiment, a method of fabricating a solar cell involves forming a dielectric region on a surface of a solar cell structure, partially removing the dielectric region on a particular region of the solar cell structure, forming a second metal layer on the dielectric region, disposing a metal foil on a seed metal layer, and directing a laser beam onto the metal foil, wherein directing the laser beam includes forming a metal bond between the seed metal layer and the metal foil and forming an ohmic contact between the seed metal layer and the solar cell structure, the metal bond and the ohmic contact being aligned with the particular region of the solar cell structure.

In one embodiment, disposing the metal foil includes disposing a patterned metal foil on the seed metal layer.

In an embodiment, a method of fabricating a solar cell involves forming a dielectric region on a surface of a solar cell structure, forming a first metal layer on the dielectric region, forming an adhesive layer on the first metal layer, and forming a second metal layer on the adhesive layer; wherein the adhesive layer mechanically couples the second metal layer to the first metal layer and allows electrical connection between the second metal layer and the first metal layer.

In one embodiment, the method further involves partially removing the dielectric region to form a contact region prior to forming the first metal layer.

In one embodiment, forming the first metal layer includes performing a method selected from the group consisting of physical vapor deposition, screen printing, sintering, plating, and laser transfer.

In one embodiment, forming the adhesive layer includes forming an insulating adhesive layer.

In one embodiment, forming the adhesive layer includes forming a low viscosity adhesive layer.

In one embodiment, forming the adhesive layer includes forming a patterned adhesive layer.

In one embodiment, forming the patterned adhesive layer includes curing the patterned adhesive layer.

In one embodiment, forming the second metal layer includes forming the second metal layer on the first metal layer using a direct Physical Vapor Deposition (PVD) process.

In one embodiment, forming the adhesive layer includes forming a conductive adhesive layer.

In one embodiment, forming the adhesive layer includes curing the adhesive layer.

In one embodiment, forming the second metal layer includes disposing a metal foil on the adhesive layer.

In one embodiment, the method further involves applying pressure on the second metal layer, wherein the applied pressure allows direct contact between the first metal layer and the second metal layer.

In one embodiment, the method further involves locally heating a particular region of the second metal layer, wherein heating includes forming a metal bond between the second metal layer and the first metal layer.

In one embodiment, locally heating includes performing a laser welding process.

In one embodiment, forming a first metal layer on the dielectric region includes forming a first patterned metal layer.

In one embodiment, the method further involves partially removing metal from the second metal layer, wherein the adhesive layer protects the solar cell structure from damage during said partial removal.

In one embodiment, partially removing metal from the second metal layer includes performing a laser ablation process.

In an embodiment, a method of fabricating a solar cell involves forming a dielectric region on a surface of a solar cell structure, forming a first patterned metal layer on the dielectric region, forming an insulating adhesive layer on the first patterned metal layer, forming a second patterned metal layer on the insulating adhesive layer, wherein the insulating adhesive layer mechanically couples the second patterned metal layer to the first patterned metal layer, and locally heating a particular region of the second patterned metal layer, wherein heating includes forming a metallic bond between the second patterned metal layer and the first patterned metal layer.

In an embodiment, a method of fabricating a solar cell involves forming a dielectric region on a surface of a solar cell structure, partially removing the dielectric region to form a contact region, forming a first patterned metal layer on the dielectric region, forming an insulating adhesive layer on the first patterned metal layer and the dielectric region, forming a second metal layer on the insulating adhesive layer, wherein the insulating adhesive layer mechanically couples the second metal layer to the first patterned metal layer. The method further involves locally heating a specific region of the second metal layer, wherein the heating includes forming a metal bond between the second metal layer and the first patterned metal layer and forming an ohmic contact in a contact region between the first metal layer and the solar cell structure, and partially removing metal from the second metal layer, wherein the removing metal forms the second patterned metal layer, and the insulating adhesive layer protects the solar cell structure from damage during said partially removing.

Claims

1. A solar cell, comprising:

a dielectric region on a surface of the solar cell structure;

a first metal layer on the dielectric region;

a second metal layer on the first metal layer;

a local metal bond between a portion of the first metal layer and a portion of the second metal layer, wherein the first metal layer is electrically connected to the solar cell structure at a location directly below and aligned with the local metal bond, the first metal layer, the second metal layer, and the local metal bond forming a conductive contact for positioning of the solar cell, and wherein the conductive contact is separated from an adjacent second conductive contact by a gap extending to the dielectric region.

2. The solar cell of claim 1, wherein the first metal layer is electrically connected to the solar cell structure underlying the local metal bond through an opening in the dielectric region.

3. The solar cell of claim 1, wherein the first metal layer is electrically connected to the solar cell structure through an ohmic contact between the first metal layer and the solar cell structure.

4. The solar cell of claim 1, wherein the second metal layer is a metal foil.

5. The solar cell of claim 4, wherein the metal foil comprises a metal selected from the group consisting of copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, and platinum.

6. The solar cell of claim 1, wherein the first metal layer is a metal seed layer.

7. The solar cell of claim 6, wherein the metal seed layer comprises a metal selected from the group consisting of copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, and platinum.

8. The solar cell of claim 1, wherein the first and second metal layers have the same inter-digitated pattern.

9. The solar cell of claim 1, wherein the solar cell structure is an N-type doped region.

10. The solar cell of claim 1, wherein the solar cell structure is a P-type doped region.

11. A solar cell, comprising:

a polysilicon region on a surface of the solar cell structure;

a first metal layer on the polysilicon region;

a second metal layer on the first metal layer;

a local metal bond between a portion of the first metal layer and a portion of the second metal layer, wherein the first metal layer is electrically connected to the solar cell structure at a location directly below and aligned with the local metal bond, the first metal layer, the second metal layer, and the local metal bond forming a conductive contact for positioning of the solar cell, and wherein the conductive contact is separated from an adjacent second conductive contact by a gap extending to the polysilicon region.

12. The solar cell of claim 11, wherein the first metal layer is electrically connected to the solar cell structure through an ohmic contact between the first metal layer and the solar cell structure.

13. The solar cell of claim 11, wherein the second metal layer is a metal foil.

14. The solar cell of claim 13, wherein the metal foil comprises a metal selected from the group consisting of copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, and platinum.

15. The solar cell of claim 11, wherein the first metal layer is a metal seed layer.

16. The solar cell of claim 15, wherein the metal seed layer comprises a metal selected from the group consisting of copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, and platinum.

17. A solar cell, comprising:

a dielectric region on the doped region of the solar cell;

a first metal layer on the dielectric region, wherein the dielectric region is continuous between the first metal layer and the doped region;

a contact in the dielectric region directly below, aligned with, and above the doped region, wherein the contact electrically connects the first metal layer to the doped region.

18. The solar cell of claim 17, wherein the contact comprises an ohmic contact.

19. The solar cell of claim 17, wherein the first metal layer is a metal seed layer.

20. The solar cell of claim 17, wherein the first metal layer comprises a metal selected from the group consisting of copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, and platinum.

21. The solar cell of claim 17, further comprising a metal foil on the first metal layer.

22. The solar cell of claim 21, further comprising a local metal bond between the first metal layer and the metal foil, the local metal bond being directly over and aligned with the contact.