WO2022047057A1 - A solar energy absorbing device and module implementing metallic copper grid lines with a black coating on its surface - Google Patents

A solar energy absorbing device and module implementing metallic copper grid lines with a black coating on its surface Download PDF

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Publication number
WO2022047057A1
WO2022047057A1 PCT/US2021/047787 US2021047787W WO2022047057A1 WO 2022047057 A1 WO2022047057 A1 WO 2022047057A1 US 2021047787 W US2021047787 W US 2021047787W WO 2022047057 A1 WO2022047057 A1 WO 2022047057A1
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Prior art keywords
photovoltaic device
surface coating
darkening
conductive traces
metal layer
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PCT/US2021/047787
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French (fr)
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Jason Tolentino
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Utica Leaseco, Llc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0216—Coatings
    • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/02167—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/544—Solar cells from Group III-V materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/547—Monocrystalline silicon PV cells

Definitions

  • This disclosure relates to the fabrication of photovoltaic devices, and in particular, to using black coating on metallic copper grid lines.
  • Solar cells made of semiconductor materials such as silicon (Si) and gallium arsenide (GaAs) convert sunlight into electrical energy.
  • ARC anti-reflection coating
  • a two dimensional front electrode grid called the front contact typically makes connection to the n-side of the p- n junction. These contacts, including a back p-contact are connected to an external load to extract useful electrical current.
  • the present disclosure details several approaches to improve the appearance of a solar cell device by achieving a blackened coating on copper contacts used in solar cell devices without compromising device performance.
  • FIGS. 1A and 1 B illustrate an example of solar modules with and without aesthetics improvements.
  • FIG. 2 illustrates another example of a solar cell with and without aesthetics improvements.
  • FIG. 3 illustrates a top view of a solar cell.
  • FIG. 4 illustrates a cross sectional view of a solar cell with a patterned resist, in accordance with aspects of this disclosure.
  • FIG. 5 illustrates a cross sectional view of a solar cell with the patterned resist removed, in accordance with aspects of this disclosure.
  • FIG. 6 illustrates an example of a flow diagram of a process or method for making a solar energy absorbing device and/or module consisting of metallic copper grid lines with a black coating on its surface, in accordance with aspects of this disclosure.
  • a method for providing a darkening surface coating includes patterning a resist deposited over a surface of a photovoltaic device, the surface of having one or more conductive traces accessible through openings in the patterned resist; depositing a metal layer over the one or more conductive traces through the openings in the patterned resist; depositing the darkening surface coating over the metal layer through the openings in the patterned resist; heating the darkening surface coating deposited over the metal layer while the patterned resist is still on the surface of the photovoltaic device to remove water content from the darkening surface coating; an removing the patterned resist from the surface of the photovoltaic device.
  • a photovoltaic device having a darkening surface coating includes a surface with one or more conductive traces; a metal layer deposited over the one or more conductive traces; and a darkening surface deposited over the metal layer, the darkening surface coating being treated with a heating process to remove water content from the darkening surface coating, the darkening surface coating being made of a material with a color substantially similar to that of the surface of the photovoltaic device.
  • This disclosure describes various aspects related to a solar energy absorbing device and module consisting of metallic copper grid lines with a black coating on its surface.
  • photovoltaics photovoltaic structures
  • TVs TV cells
  • solar cells may be used interchangeably to refer to one or more portions of an optoelectronic component or module that produce voltage and/or electric current when exposed to light.
  • FIG. 1A shows a diagram 100a that illustrates an example of a conventional solar module for a solar cell that shows inactive area losses 110, series sub-string losses 120, and bus bar losses 130. These are losses that occur by having part of the surface of the solar cell not being used to capture light.
  • FIG. 1B shows a diagram 100b that illustrates an example of a modified solar module where there are no bus bars, inactive areas have been removed, and parallel sub-strings are being used to improve upon the performance of the solar module. These improvements also result in a more aesthetically attractive module as the solar module looks more uniform (see e.g., https://www.solaria.com/rooftops- utility/).
  • FIG. 2 shows a diagram 200 that illustrates another example of a solar cell with and without aesthetics improvements.
  • a solar module 210 to the left shows the traditional lines that appear when arranging multiple solar cells into a module.
  • a solar module 220 to the right shows a more aesthetically pleasing solution that uses a matte black frame and a complementary black back sheet to make the solar module more uniform.
  • the solar cells in each of the solar module 210 and the solar module 220 may use thin electrodes to make them also more aesthetically pleasing (see e.g., https://www.lg.com/global/business/solar/neon-2/neon-2-black).
  • FIG. 3 shows a diagram 300 that illustrates a top view of a solar cell that may be used alone or as part of a module.
  • the solar cell includes an absorbing structure or PV layer 310 and conductive traces on top of a surface of the absorbing structure 310.
  • the structure or PV layer 310 may be referred to as a solar cell.
  • These conductive traces can be in the form of finger electrodes 330, bus bars 320, and also solar cell interconnects (not shown).
  • FIG. 4 shows a diagram 400 that illustrates a cross sectional view of a solar cell with a patterned resist 410, in accordance with aspects of this disclosure.
  • the patterned resist 410 is used to define conductive traces that are formed from a metal layer 420 (e.g., copper) and a dark coating 430, details of which are provided below.
  • the patterned resist 410 may be kept until the dark coating 430 is properly thermally processed, at which point the patterned resist 410 may be removed such that the conductive traces on the structure 310 are now covered with the dark coating 430 to provide a more aesthetically attractive solution without reducing the performance of the solar cell.
  • FIG. 5 shows a diagram 500 that illustrates a cross sectional view of the solar cell in FIG. 4 with the patterned resist removed, in accordance with aspects of this disclosure.
  • the material for the metal layer 420 can be a metallic copper or a copper alloy.
  • copper alloys include zinc, phosphorus, nickel, tin, silicon, beryllium, or cobalt.
  • the treating solutions for making or forming the dark coating 430 can include any one of Copper Selenide (CuSe), Copper Oxide (CuO), Black Electroless Nickel (EN), Sulfur based copper chelators and/or copper inhibitors, and/or NiMo alloy.
  • CuSe Copper Selenide
  • CuO Copper Oxide
  • EN Black Electroless Nickel
  • Sulfur based copper chelators and/or copper inhibitors and/or NiMo alloy.
  • the general process or method to produce a dark surface is described in more detail below in connection with FIG. 6.
  • the method involves first forming the metal layer (e.g., the metal layer 420) and then forming the dark coating (e.g., the dark coating 430), which is baked at a low temperature (e.g., less than 190 degrees Celsius).
  • a low temperature e.g., less than 190 degrees Celsius
  • the deposition may involve a combination of materials as described in the following table: [0025]
  • all the chemicals may be mixed at room temperature with typical ratios of 1 HsPO4:1 Cu2SO4:1 SeO2:2 (NH4)2MoO4:1 surfactant.
  • the process temperature can be in the range from 10C-40C and for a process time from 2 minutes to 30 minutes depending on desired adhesion and color. Preferred temperature and time is 30C for 5 minutes.
  • the deposition of CuSe can either be done by dipping the substrate and/or by electroplating (i.e. with a bias).
  • CuO Copper Oxide
  • a sodium hydroxide solution ⁇ 10M
  • an oxidizer(0.1-1 M) is added.
  • the oxidizer with a redox potential more positive than copper such as hydrogen peroxide, sodium persulfate, manganese permanganate, etc. would be sufficient enough to deposit the correct stoichiometry of Cu(ll)O.
  • the preferred oxidizer is hydrogen peroxide and sodium persulfate due to its larger redox potential. Generally, a smaller redox potential differences between copper and the oxidizer gives slower deposition rates.
  • the process may involve 1-100 mM dithiooxamide in 0.5-1.0 M KOH and/or DI water only. In some instances, the preferred concentrations may be 40-100 mM in order to achieve a darker patina. The process time may involve a 3 minutes - 10 minutes immersion.
  • a sulfur based chelator With respect to sulfur-based chelators/corrosion inhibitors, in addition to creating a darker surface, a sulfur based chelator also acts an alkaline corrosion inhibitor. Previous data shows that during resist strip (see e.g., FIG. 6) after electroplating, copper plates on a GaAs solar cell surface. Copper is one of GaAs killer elements which can decrease device performance.
  • a sulfur-based chelator specifically dithiooxamide may be used to prevent alkaline corrosion of copper while creating a dark patina on the copper surface.
  • sulfur-based chelators/corrosion inhibitors may include pyrazole, cupferron, and/or dithiooxamide.
  • the deposition may involve a combination of materials as described in the following table:
  • pH is controlled to deposit correct molybdenum species.
  • the pH range may be between 1.5-6, with a preferred value about 4.88.
  • the applied bias may be between 25 - 200 mA, with a preferred current of about 100 mA
  • the process temperature may be between 40 - 80C, with a preferred temperature of about 70C, and a process time between 10-60 minutes, with a preferred time of about 30 minutes.
  • FIG. 6 illustrates an example of a flow diagram of a process or method 600 for making a solar energy absorbing device and/or module consisting of metallic copper grid lines with a black coating on its surface, in accordance with aspects of this disclosure.
  • the method 600 includes patterning a resist deposited over a surface of a photovoltaic device, the surface of having one or more conductive traces accessible through openings in the patterned resist. [0035] At 610, the method 600 includes depositing a metal layer over the one or more conductive traces through the openings in the patterned resist.
  • the method 600 includes depositing the darkening surface coating over the metal layer through the openings in the patterned resist.
  • the method 600 includes heating the darkening surface coating deposited over the metal layer while the patterned resist is still on the surface of the photovoltaic device to remove water content from the darkening surface coating.
  • the method 600 includes removing the patterned resist from the surface of the photovoltaic device.
  • depositing the metal layer over the one or more conductive traces includes electroplating copper over the one or more conductive traces.
  • the one or more conductive traces include at least one of one or more finger electrodes, one or more bus bars, or one or more interconnects.
  • the photovoltaic device is a solar cell or a solar module having multiple solar cells.
  • the photovoltaic device includes a silicon- based solar cell or a solar module having multiple silicon-based solar cells.
  • the photovoltaic device includes a solar cell based on a group lll-V compound semiconductor or a solar module having multiple solar cells based on a group lll-V compound semiconductor.
  • heating the darkening surface coating includes heating the darkening surface coating to a temperature equal to or less than 190 degrees Celsius.
  • the darkening surface coating comprises a material with a color substantially similar to that of the surface of the photovoltaic device.
  • the darkening surface coating comprises at least one of copper selenide (CuSe), copper oxide (CuO), nickel molybdenum (NiMo), sulfur-based chelators, or electroless nickel (Ni).
  • the one or more conductive traces include a bus bar, the method further comprising removing a portion of the darkening surface coating over the bus bar to enable an electrical connection between the bus bar of the photovoltaic device and another photovoltaic device.

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Abstract

Various aspects of this disclosure relate to a solar or photovoltaic device consisting of metallic copper grid lines with a black coating on its surface. In an aspect, a method is described that includes patterning a resist deposited over a surface of a photovoltaic device, the surface of having one or more conductive traces accessible through openings in the patterned resist; depositing a metal layer over the one or more conductive traces through the openings in the patterned resist; depositing the darkening surface coating over the metal layer through the openings in the patterned resist; heating the darkening surface coating deposited over the metal layer while the patterned resist is still on the surface of the photovoltaic device to remove water content from the darkening surface coating; and removing the patterned resist from the surface of the photovoltaic device.

Description

A SOLAR ENERGY ABSORBING DEVICE AND MODULE IMPLEMENTING METALLIC COPPER GRID LINES WITH A BLACK COATING ON ITS SURFACE
CROSS REFERENCE TO RELATED APPLICATIONS
[001] This application claims priority to U.S. Patent Provisional Application No. 63/071 ,757, filed August 28, 2020, the entire contents of which are hereby incorporated by reference.
TECHNICAL FIELD
[002] This disclosure relates to the fabrication of photovoltaic devices, and in particular, to using black coating on metallic copper grid lines.
BACKGROUND
[003] Solar cells made of semiconductor materials such as silicon (Si) and gallium arsenide (GaAs) convert sunlight into electrical energy. The side of the semiconductor in which incident light is generally coated with an anti-reflection coating (ARC) to reduce reflective losses of sunlight which results in an increase the efficiency of the solar cell and a device that can appear black. In addition, a two dimensional front electrode grid called the front contact typically makes connection to the n-side of the p- n junction. These contacts, including a back p-contact are connected to an external load to extract useful electrical current.
[004] Conventional materials for solar cell front contacts include silver and copper. The inclusion of metallic gridlines aid in helping extract useful current. However, its presence introduces some shading losses affecting device performance. There exist technologies that address this such as finding the optimal finger geometry balanced with front side sheet resistance to reduce shading losses, moving the n/p contacts to the back, or using transparent contacts. While the intention of these technologies has been to improve device performance, they also seem to improve the appearance from an aesthetics point of view even though that may not have been the original intention. Additional techniques the also improve the appearance of solar cells may also be desirable.
[005] The present disclosure details several approaches to improve the appearance of a solar cell device by achieving a blackened coating on copper contacts used in solar cell devices without compromising device performance.
BRIEF DESCRIPTION OF THE DRAWINGS
[006] FIGS. 1A and 1 B illustrate an example of solar modules with and without aesthetics improvements.
[007] FIG. 2 illustrates another example of a solar cell with and without aesthetics improvements.
[008] FIG. 3 illustrates a top view of a solar cell.
[009] FIG. 4 illustrates a cross sectional view of a solar cell with a patterned resist, in accordance with aspects of this disclosure.
[0010] FIG. 5 illustrates a cross sectional view of a solar cell with the patterned resist removed, in accordance with aspects of this disclosure.
[0011] FIG. 6 illustrates an example of a flow diagram of a process or method for making a solar energy absorbing device and/or module consisting of metallic copper grid lines with a black coating on its surface, in accordance with aspects of this disclosure.
SUMMARY OF THE DISCLOSURE
[0012] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later. [0013] In an aspect, a method for providing a darkening surface coating is described that includes patterning a resist deposited over a surface of a photovoltaic device, the surface of having one or more conductive traces accessible through openings in the patterned resist; depositing a metal layer over the one or more conductive traces through the openings in the patterned resist; depositing the darkening surface coating over the metal layer through the openings in the patterned resist; heating the darkening surface coating deposited over the metal layer while the patterned resist is still on the surface of the photovoltaic device to remove water content from the darkening surface coating; an removing the patterned resist from the surface of the photovoltaic device.
[0014] In another aspect, a photovoltaic device having a darkening surface coating is described that includes a surface with one or more conductive traces; a metal layer deposited over the one or more conductive traces; and a darkening surface deposited over the metal layer, the darkening surface coating being treated with a heating process to remove water content from the darkening surface coating, the darkening surface coating being made of a material with a color substantially similar to that of the surface of the photovoltaic device.
DETAILED DESCRIPTION
[0015] This disclosure describes various aspects related to a solar energy absorbing device and module consisting of metallic copper grid lines with a black coating on its surface. As used herein the terms “photovoltaics,” “photovoltaic structures,” TVs,” TV cells,” and “solar cells” may be used interchangeably to refer to one or more portions of an optoelectronic component or module that produce voltage and/or electric current when exposed to light.
[0016] FIG. 1A shows a diagram 100a that illustrates an example of a conventional solar module for a solar cell that shows inactive area losses 110, series sub-string losses 120, and bus bar losses 130. These are losses that occur by having part of the surface of the solar cell not being used to capture light. [0017] FIG. 1B shows a diagram 100b that illustrates an example of a modified solar module where there are no bus bars, inactive areas have been removed, and parallel sub-strings are being used to improve upon the performance of the solar module. These improvements also result in a more aesthetically attractive module as the solar module looks more uniform (see e.g., https://www.solaria.com/rooftops- utility/).
[0018] FIG. 2 shows a diagram 200 that illustrates another example of a solar cell with and without aesthetics improvements. In this example, a solar module 210 to the left shows the traditional lines that appear when arranging multiple solar cells into a module. A solar module 220 to the right shows a more aesthetically pleasing solution that uses a matte black frame and a complementary black back sheet to make the solar module more uniform. The solar cells in each of the solar module 210 and the solar module 220 may use thin electrodes to make them also more aesthetically pleasing (see e.g., https://www.lg.com/global/business/solar/neon-2/neon-2-black).
[0019] FIG. 3 shows a diagram 300 that illustrates a top view of a solar cell that may be used alone or as part of a module. The solar cell includes an absorbing structure or PV layer 310 and conductive traces on top of a surface of the absorbing structure 310. In some instances, the structure or PV layer 310 may be referred to as a solar cell. These conductive traces can be in the form of finger electrodes 330, bus bars 320, and also solar cell interconnects (not shown).
[0020] FIG. 4 shows a diagram 400 that illustrates a cross sectional view of a solar cell with a patterned resist 410, in accordance with aspects of this disclosure. In this example, the patterned resist 410 is used to define conductive traces that are formed from a metal layer 420 (e.g., copper) and a dark coating 430, details of which are provided below. The patterned resist 410 may be kept until the dark coating 430 is properly thermally processed, at which point the patterned resist 410 may be removed such that the conductive traces on the structure 310 are now covered with the dark coating 430 to provide a more aesthetically attractive solution without reducing the performance of the solar cell. [0021] FIG. 5 shows a diagram 500 that illustrates a cross sectional view of the solar cell in FIG. 4 with the patterned resist removed, in accordance with aspects of this disclosure.
[0022] In connection with this disclosure, the material for the metal layer 420 can be a metallic copper or a copper alloy. Examples of copper alloys include zinc, phosphorus, nickel, tin, silicon, beryllium, or cobalt. The treating solutions for making or forming the dark coating 430 (e.g., the blackening process) can include any one of Copper Selenide (CuSe), Copper Oxide (CuO), Black Electroless Nickel (EN), Sulfur based copper chelators and/or copper inhibitors, and/or NiMo alloy. In alternative embodiments, it is possible to obtain electrical conductive, black metals similar to black EN, for example, black copper can also be achieved the same way black nickel through surface roughening.
[0023] The general process or method to produce a dark surface is described in more detail below in connection with FIG. 6. The method involves first forming the metal layer (e.g., the metal layer 420) and then forming the dark coating (e.g., the dark coating 430), which is baked at a low temperature (e.g., less than 190 degrees Celsius).
[0024] In the case of Copper Selenide (CuSe) as the dark coating, the deposition may involve a combination of materials as described in the following table:
Figure imgf000006_0001
[0025] For the deposition process in the general process flow (see e.g., FIG. 6), all the chemicals may be mixed at room temperature with typical ratios of 1 HsPO4:1 Cu2SO4:1 SeO2:2 (NH4)2MoO4:1 surfactant. The process temperature can be in the range from 10C-40C and for a process time from 2 minutes to 30 minutes depending on desired adhesion and color. Preferred temperature and time is 30C for 5 minutes. Based on the range of concentrations used here, the deposition of CuSe can either be done by dipping the substrate and/or by electroplating (i.e. with a bias).
[0026] In the case of Copper Oxide (CuO) as the dark coating, making and controlling black CuO requires oxidizing copper at high pH. In this embodiment, a sodium hydroxide solution (~10M) is made and an oxidizer(0.1-1 M) is added. The oxidizer with a redox potential more positive than copper such as hydrogen peroxide, sodium persulfate, manganese permanganate, etc. would be sufficient enough to deposit the correct stoichiometry of Cu(ll)O. The preferred oxidizer is hydrogen peroxide and sodium persulfate due to its larger redox potential. Generally, a smaller redox potential differences between copper and the oxidizer gives slower deposition rates.
[0027] In the case of Black Electroless Nickel as the dark coating, the following table provides a guide of the various steps that may need to be performed.
Figure imgf000007_0001
Figure imgf000008_0001
[0028] For Black Electroless Nickel, while this chemistry already exists, modifications in chemistry and processing to make it compatible with various products may be needed as it relates to darkening of the copper, provide excellent adhesion, and maintain film flatness after the baking process.
[0029] In the case of Sulfur Based Chelators as the dark coating, the process may involve 1-100 mM dithiooxamide in 0.5-1.0 M KOH and/or DI water only. In some instances, the preferred concentrations may be 40-100 mM in order to achieve a darker patina. The process time may involve a 3 minutes - 10 minutes immersion. [0030] With respect to sulfur-based chelators/corrosion inhibitors, in addition to creating a darker surface, a sulfur based chelator also acts an alkaline corrosion inhibitor. Previous data shows that during resist strip (see e.g., FIG. 6) after electroplating, copper plates on a GaAs solar cell surface. Copper is one of GaAs killer elements which can decrease device performance. To prevent plating of copper onto GaAs, a sulfur-based chelator, specifically dithiooxamide may be used to prevent alkaline corrosion of copper while creating a dark patina on the copper surface. Some examples of sulfur-based chelators/corrosion inhibitors may include pyrazole, cupferron, and/or dithiooxamide.
[0031] In the case of Copper Selenide (CuSe) as the dark coating, the deposition may involve a combination of materials as described in the following table:
Figure imgf000009_0001
[0032] For the deposition process in the general process flow (see e.g., FIG. 6), pH is controlled to deposit correct molybdenum species. The pH range may be between 1.5-6, with a preferred value about 4.88. Also as part of the process, the applied bias may be between 25 - 200 mA, with a preferred current of about 100 mA, the process temperature may be between 40 - 80C, with a preferred temperature of about 70C, and a process time between 10-60 minutes, with a preferred time of about 30 minutes.
[0033] FIG. 6 illustrates an example of a flow diagram of a process or method 600 for making a solar energy absorbing device and/or module consisting of metallic copper grid lines with a black coating on its surface, in accordance with aspects of this disclosure.
[0034] At 605, the method 600 includes patterning a resist deposited over a surface of a photovoltaic device, the surface of having one or more conductive traces accessible through openings in the patterned resist. [0035] At 610, the method 600 includes depositing a metal layer over the one or more conductive traces through the openings in the patterned resist.
[0036] At 615, the method 600 includes depositing the darkening surface coating over the metal layer through the openings in the patterned resist.
[0037] At 620, the method 600 includes heating the darkening surface coating deposited over the metal layer while the patterned resist is still on the surface of the photovoltaic device to remove water content from the darkening surface coating.
[0038] At 625, the method 600 includes removing the patterned resist from the surface of the photovoltaic device.
[0039] In an aspect of the method 600, depositing the metal layer over the one or more conductive traces includes electroplating copper over the one or more conductive traces.
[0040] In an aspect of the method 600, the one or more conductive traces include at least one of one or more finger electrodes, one or more bus bars, or one or more interconnects.
[0041] In an aspect of the method 600, the photovoltaic device is a solar cell or a solar module having multiple solar cells.
[0042] In an aspect of the method 600, the photovoltaic device includes a silicon- based solar cell or a solar module having multiple silicon-based solar cells.
[0043] In an aspect of the method 600, the photovoltaic device includes a solar cell based on a group lll-V compound semiconductor or a solar module having multiple solar cells based on a group lll-V compound semiconductor.
[0044] In an aspect of the method 600, heating the darkening surface coating includes heating the darkening surface coating to a temperature equal to or less than 190 degrees Celsius.
[0045] In an aspect of the method 600, the darkening surface coating comprises a material with a color substantially similar to that of the surface of the photovoltaic device. [0046] In an aspect of the method 600, the darkening surface coating comprises at least one of copper selenide (CuSe), copper oxide (CuO), nickel molybdenum (NiMo), sulfur-based chelators, or electroless nickel (Ni).
[0047] In an aspect of the method 600, the one or more conductive traces include a bus bar, the method further comprising removing a portion of the darkening surface coating over the bus bar to enable an electrical connection between the bus bar of the photovoltaic device and another photovoltaic device.
[0048] As noted above, in conventional solar cells with front contacts, a non- negligible fraction of the active area is covered with a reflective metal. For non-space applications such as consumer electronics and automotive industry, the presence of the reflective metal is one of the most common criticisms regarding the appearance of solar modules. By coating products as described in this disclosure with a material to reduce the reflectivity of the metal to make it appear darker in color, it would make implementation easier since it does not require optimizing other aspects of the device to achieve high efficiency. Moreover, since some of the materials deposited to darken the metal use in solar cells or modules tend to be powdery and have poor adhesion after the deposition and after subsequent processing, the processes described in this disclosure also improve the adhesion of the coating. In addition, many materials that have a black coating deposits are not electrically conductive, however, using black EN allows for a black coating that is electrically conductive. As such, this chemistry can be extended not only to front metal, but also interconnects as well.
[0049] The above description of various embodiments of the claimed subject matter has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the claimed subject matter to the precise forms disclosed. Many modifications and variations will be apparent to one skilled in the art. Embodiments were chosen and described in order to best describe certain principles and practical applications, thereby enabling others skilled in the relevant art to understand the subject matter, the various embodiments and the various modifications that are suited to the particular uses contemplated.

Claims

CLAIMS What is claimed is:
1 . A method for providing a darkening surface coating, comprising: patterning a resist deposited over a surface of a photovoltaic device that has one or more conductive traces accessible through openings in the patterned resist; depositing a metal layer over the one or more conductive traces through the openings in the patterned resist; depositing the darkening surface coating over the metal layer through the openings in the patterned resist; heating the darkening surface coating that is deposited over the metal layer while the patterned resist is still on the surface of the photovoltaic device to remove water content from the darkening surface coating; and removing the patterned resist from the surface of the photovoltaic device.
2. The method of claim 1 , wherein depositing the metal layer over the one or more conductive traces includes electroplating copper over the one or more conductive traces.
3. The method of claim 1 , wherein the one or more conductive traces include at least one of one or more finger electrodes, one or more bus bars, or one or more interconnects.
4. The method of claim 1 , wherein the photovoltaic device is a solar cell or a solar module having multiple solar cells.
5. The method of claim 1 , wherein the photovoltaic device includes a silicon- based solar cell or a solar module having multiple silicon-based solar cells.
6. The method of claim 1 , wherein the photovoltaic device includes a solar cell based on a group lll-V compound semiconductor or a solar module having multiple solar cells based on a group lll-V compound semiconductor.
7. The method of claim 1 , wherein heating the darkening surface coating includes heating the darkening surface coating to a temperature equal to or less than 190 degrees Celsius.
8. The method of claim 1 , wherein the darkening surface coating comprises a material with a color substantially similar to that of the surface of the photovoltaic device.
9. The method of claim 1 , wherein the darkening surface coating comprises at least one of copper selenide (CuSe), copper oxide (CuO), nickel molybdenum (NiMo), sulfur-based chelators, and electroless nickel (Ni).
10. The method of claim 1 , wherein the one or more conductive traces include a bus bar, the method further comprising removing a portion of the darkening surface coating over the bus bar to enable an electrical connection between the bus bar of the photovoltaic device and another photovoltaic device.
11. A photovoltaic device having a darkening surface coating, comprising: a surface with one or more conductive traces; a metal layer deposited over the one or more conductive traces; and a darkening surface deposited over the metal layer, the darkening surface coating being treated with a heating process to remove water content from the darkening surface coating, the darkening surface coating being made of a material with a color substantially similar to that of the surface of the photovoltaic device.
12. The photovoltaic device of claim 11 , wherein the metal layer includes electroplated copper deposited over the one or more conductive traces.
13. The photovoltaic device of claim 11 , wherein the one or more conductive traces include at least one of one or more finger electrodes, one or more bus bars, or one or more interconnects.
14. The photovoltaic device of claim 1 , wherein the photovoltaic device is a solar cell or a solar module having multiple solar cells.
15. The photovoltaic device of claim 1 , wherein the photovoltaic device includes a silicon-based solar cell or a solar module having multiple silicon-based solar cells.
16. The photovoltaic device of claim 1 , wherein the photovoltaic device includes a solar cell based on a group lll-V compound semiconductor or a solar module having multiple solar cells based on a group lll-V compound semiconductor.
17. The photovoltaic device of claim 1 , wherein the darkening surface coating comprises at least one of copper selenide (CuSe), copper oxide (CuO), nickel molybdenum (NiMo), sulfur-based chelators, or electroless nickel (Ni).
18. The photovoltaic device of claim 1 , wherein the one or more conductive traces include a bus bar, and a portion of the darkening surface coating over the bus bar is removed to enable an electrical connection between the bus bar of the photovoltaic device and another photovoltaic device.
PCT/US2021/047787 2020-08-28 2021-08-26 A solar energy absorbing device and module implementing metallic copper grid lines with a black coating on its surface WO2022047057A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150349152A1 (en) * 2012-09-14 2015-12-03 Atotech Deutschland Gmbh Method for metallization of solar cell substrates
US9983705B2 (en) * 2013-11-20 2018-05-29 Lg Chem, Ltd. Conductive structure and manufacturing method therefor
US20190237592A1 (en) * 2018-01-31 2019-08-01 Solaria Corporation Photovoltaic system and components
US20200135942A1 (en) * 2018-10-31 2020-04-30 The Solaria Corporation Methods of forming a colored conductive ribbon for integration in a solar module

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150349152A1 (en) * 2012-09-14 2015-12-03 Atotech Deutschland Gmbh Method for metallization of solar cell substrates
US9983705B2 (en) * 2013-11-20 2018-05-29 Lg Chem, Ltd. Conductive structure and manufacturing method therefor
US20190237592A1 (en) * 2018-01-31 2019-08-01 Solaria Corporation Photovoltaic system and components
US20200135942A1 (en) * 2018-10-31 2020-04-30 The Solaria Corporation Methods of forming a colored conductive ribbon for integration in a solar module

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