WO2011109904A1 - Photovoltaic nanoparticle-coated product and method of manufacturing same - Google Patents

Photovoltaic nanoparticle-coated product and method of manufacturing same Download PDF

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Publication number
WO2011109904A1
WO2011109904A1 PCT/CA2011/000266 CA2011000266W WO2011109904A1 WO 2011109904 A1 WO2011109904 A1 WO 2011109904A1 CA 2011000266 W CA2011000266 W CA 2011000266W WO 2011109904 A1 WO2011109904 A1 WO 2011109904A1
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Prior art keywords
photovoltaic
layer
electrode layer
product
artificial
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Application number
PCT/CA2011/000266
Other languages
French (fr)
Inventor
Stephen Poh Chew Kong
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Thinkeco Power Inc.
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Publication date
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Publication of WO2011109904A1 publication Critical patent/WO2011109904A1/en

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    • A—HUMAN NECESSITIES
    • A41—WEARING APPAREL
    • A41G—ARTIFICIAL FLOWERS; WIGS; MASKS; FEATHERS
    • A41G1/00—Artificial flowers, fruit, leaves, or trees; Garlands
    • A41G1/001—Artificial flowers, fruit, leaves, or trees; Garlands characterised by their special functions
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02367—Substrates
    • H01L21/0237—Materials
    • H01L21/02422—Non-crystalline insulating materials, e.g. glass, polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
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    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02436—Intermediate layers between substrates and deposited layers
    • H01L21/02439—Materials
    • H01L21/02491—Conductive materials
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    • H01L21/02518—Deposited layers
    • H01L21/02521—Materials
    • H01L21/02568—Chalcogenide semiconducting materials not being oxides, e.g. ternary compounds
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    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02587—Structure
    • H01L21/0259—Microstructure
    • H01L21/02601—Nanoparticles
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    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
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    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02612—Formation types
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    • H01L21/02623—Liquid deposition
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    • H01L31/0392—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
    • H01L31/03926—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate comprising a flexible substrate
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    • H01L31/0248—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 characterised by their semiconductor bodies
    • H01L31/036—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
    • H01L31/0392—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
    • H01L31/03926—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate comprising a flexible substrate
    • H01L31/03928—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate comprising a flexible substrate including AIBIIICVI compound, e.g. CIS, CIGS deposited on metal or polymer foils
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    • H01L31/042—PV modules or arrays of single PV cells
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    • H01L31/06—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 adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/072—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 adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN heterojunction type
    • H01L31/0749—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 adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN heterojunction type including a AIBIIICVI compound, e.g. CdS/CulnSe2 [CIS] heterojunction solar cells
    • H—ELECTRICITY
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    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
    • 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
    • Y02E10/541—CuInSe2 material PV 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
    • Y02E10/547—Monocrystalline silicon PV 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • This invention relates generally to a photovoltaic nanoparticle-coated product such as artificial vegetation, and a method of manufacturing same.
  • Newer solar collector technologies such as thin-film photovoltaic cells show promise.
  • Such thin-film cells are made by depositing one or more thin layers of photovoltaic material onto a substrate.
  • Such thin film photovoltaic cells are commercially available for installation onto the roofs of buildings, and semitransparent thin film photovoltaic cells are being proposed as glazing for windows.
  • Such applications still are very specialized and thus require significant capital cost to implement, which serves as a continued barrier to wide adoption.
  • the product can be artificial vegetation such as a tree, lawn, flowers, and shrubbery and the other function can be to provide an aesthetic substitute for natural vegetation.
  • the product can be outdoor furniture, and the other function is to furnish a habitat.
  • the method comprises the steps of forming a solar collector and combining the solar collector with other components of the product so that the product performs the at least one other function and harvests solar energy.
  • the step of forming the solar collector comprises: selecting a component of the product to serve as a base
  • V83878WOWAN LAW ⁇ 757017 ⁇ 1 1 substrate the selected component being suitable to withstand a photovoltaic nanoparticle coating application step; coupling an electrically conductive base electrode layer to the base substrate; applying at least one coating of photovoltaic nanoparticles onto the base electrode layer to form a photovoltaic absorber layer; coupling a junction partner layer to the photovoltaic absorber layer; and coupling an electrically conductive transparent electrode layer to the junction partner layer, such that the photovoltaic absorber layer is in electrical communication with the base electrode layer and transparent electrode layer.
  • a product for harvesting solar energy and for at least one other function such as the aforementioned artificial vegetation and outdoor furniture.
  • the product comprises a solar collector and at least one other component that when combined form the product and enables the product to serve the at least one other function.
  • the solar collector comprises: a component of the product selected to serve as the base substrate; an electrically conductive base electrode layer coupled to the base substrate; a photovoltaic absorber layer coupled to the base electrode layer comprising at least one coating of photovoltaic nanoparticles; a junction partner layer coupled to the photovoltaic absorber layer; and an electrically conductive transparent electrode layer coupled to the junction partner layer; wherein the absorber layer is in electrical communication with the base electrode layer and the transparent electrode layer.
  • the component selected to be the base substrate must be suitable to withstand a photovoltaic nanoparticle coating application.
  • Examples of products for solar energy harvesting according to the above aspect of the invention include artificial vegetation such as trees or shrubbery that can be manufactured inexpensively by integrating the photovoltaic nanoparticles coating application step into a conventional process for manufacturing the artificial vegetation.
  • artificial vegetation can be used outdoors to harvest solar energy.
  • Such trees and shrubbery can be relatively inexpensive to manufacture and are aesthetically pleasing. Additionally, such
  • V83878WO ⁇ VAN_LAW ⁇ 757017 ⁇ 1 2 nanotechnology in the form of thin films can also be embedded on other conventional outdoor objects, such as but not limited to walls and windows of a building; in contrast to existing techniques for attaching thin film solar collectors to walls or windows of buildings, the products according to aspects of the invention utilize components of the walls or windows as the base substrate.
  • Other products include patio furniture, leisure goods, and toys; one specific example of such products is wicker furniture in which the wicker serves as the base substrate, and the solar collector is in the form of strips which are wrapped around a frame of the wicker furniture.
  • aspects of the present invention can make use of and be implemented with either new or existing production equipment and technology that are already commercially available.
  • existing artificial tree manufacturing equipment can be used to make much of the solar energy harvesting artificial tree according to an aspect of the invention.
  • the solar energy harvesting product includes a photovoltaic nanoparticle absorber layer that can be inkjet coated or spray-painted onto a substrate assembly to make very thin solar collectors.
  • the nanoparticles can in one aspect include a specialized ink made up of silicon nanocrystals.
  • aspects of the present invention can use a photovoltaic nanoparticle coating process having a much lower melting temperatures, between 300°C and 900°C, for melting everything but the silicon molecules compared with bulk silicon which is typically over 1400°C. This can significantly reduce the cost of heating, which is a substantial cost in the production of traditional crystalline silicon solar cells.
  • the photovoltaic nanoparticles can be selected from a group of materials that belong to periodic table group IB, IIIA, IV or VIA.
  • the photovoltaic absorber layer composition can be based on copper indium gallium selenide or "CI(G)S(S)".
  • CI(G)S(S) is particularly advantageous since it is a direct band gap semiconductor, which needs much less material to make a solar cell.
  • CI(G)S(S) inks typically are semi-transparent.
  • Another aspect of this invention includes applying the photovoltaic nanoparticles onto the substrate assembly by an inkjet application or printing process.
  • This inkjet printing technique can produce a leaf-shaped solar collector that mimics the natural colors of real tree leaves by depositing the active layer of the solar cell devices using a conventional and commercially available process that is similar to those that are being used in the production of electronic devices, magnetic media and photographic film, among other products.
  • a suitable dye, or semi-transparent materials such as CI(G)S(S)
  • the upper layer can maintain the true color and texture of natural tree leaves.
  • the systems and methods of the present invention can be inexpensive since it makes use of and can be implemented with either new or
  • Figure 1 depicts an outdoor artificial solar energy harvesting tree according to one embodiment of the present invention.
  • Figure 2 depicts an outdoor artificial solar energy harvesting tree according to another embodiment of the present invention.
  • Figure 3 shows a portion of leaves, branches and trunk, and electrical and physical connections of the solar energy harvesting tree of Figure 2.
  • Figure 4 depicts a sectional view of a solar collector leaf of the solar energy harvesting trees shown in Figures 1 and 2.
  • Figure 5 depicts a connection diagram for connecting the solar energy harvesting tree to a power grid according to an embodiment of the present invention.
  • Figures 6 depicts a flow diagram of a method for manufacturing the solar energy harvesting tree according to an embodiment of the present invention.
  • Figure 7 depicts a method for forming a substrate assembly of the solar collector leaf.
  • Figure 8 depicts a method for forming a photovoltaic absorber layer of the solar collector leaf.
  • Figure 9 depicts a method for forming a solar collector sheet from a compound film sheet and an encapsulant sheet.
  • Figure 10 depicts a method for forming each solar collector leaf from the sheet shown in Figure 9.
  • Figure 11 depicts a perspective view of multiple solar collector leaves mounted to a branch of the solar energy harvesting tree shown in Figure 2.
  • Figures 12(a) to (e) depicts various steps in forming a trunk of the solar energy harvesting tree.
  • Figure 13 depicts a flow diagram of a method for operating an artificial solar energy harvesting tree according to an embodiment of the present invention.
  • Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about,” it will be understood that the particular value forms another embodiment.
  • the embodiments described herein relate to products coated with photovoltaic nanoparticles and a method of manufacturing such products to transform such products into solar energy harvesting means.
  • Such products coated with photovoltaic nanoparticles and a method of manufacturing such products to transform such products into solar energy harvesting means.
  • V83878WO ⁇ VAN_LAW ⁇ 757017 ⁇ l 6 have components that can serve as a coatable substrate layer and that can withstand a photovoltaic nanoparticle coating process; and in particular include consumer products such as artificial trees, artificial grass, artificial flowers and other artificial vegetation. While the embodiments described herein are artificial trees with photovoltaic nanoparticle coated leaves, it will be understood to one skilled in the art that the photovoltaic nanoparticle coating can be applied to other consumer products with similarly coatable components, such as the wicker strips of wicker chairs and other wicker products.
  • the solar energy harvesting tree 10 shown in Figure 1 mimics a ficus tree ("artificial solar energy harvesting ficus tree")
  • the tree 12 shown in Figure 2 mimics an evergreen (“artificial solar energy harvesting evergreen tree”).
  • the artificial ficus tree 10 can be produced by forming a thin layer of plastic foam on the surface of plastic tubing and serving as a tree limb, including a tree trunk 14 and vines and branches and then exposing the foam to a blast of flame or concentrated heat to cause the foam to partially melt and collapse forming a rough surface that resembles the rough surface of the limbs of a real ficus tree.
  • the artificial evergreen tree 12 has a plastic tubing that forms limbs including a tree trunk 14 and branches 20 connected to the trunk 14.
  • Both the artificial solar energy harvesting ficus tree 10 and the artificial solar energy harvesting evergreen tree 2 are provided with leaf-shaped thin-film solar collectors connected to a branch 20. Electrical conductors 16 extend through the hollow trunk 14, through the branches 20 and to each solar collecting leaf 22, thereby electrically connecting each solar collecting leaf 22 to an electrical cable 26 extending from the base 30 of the solar energy harvesting tree 10, 12.
  • FIG. 3 shows a part of the trunk 14, one branch 20 and six leaves 22 of the artificial evegreen tree 12.
  • the solar energy harvesting tree 12 has a hollow trunk 14 with the inner electrically conductive core 16 extending therethrough and with multiple branch mounting receptacles 15 in the trunk 14.
  • the solar energy harvesting tree 12 also has a plurality of hollow braches 20 each with an electrically conductive core 17 extending therethrough and with multiple leaf mounting receptacles 18 in each branch 20 (one leaf 22 in Figure 3 is shown unattached to the branch 20 to better illustrate the leaf mounting receptacle 18).
  • Each branch 20 has one end physically connectable to the trunk 14 at the branch mounting receptacle 15, such that the branch's electrically conductive core 17 is electrically coupled to the trunk's electrically conductive core 16.
  • the solar energy harvesting tree 12 also comprises multiple solar collector leaves 22 each physically coupled to a respective branch 20 at the branch mounting receptacle 18.
  • An electrical conductor extends from the leaf 18 through the branch mounting receptacle and contacts the branch's electrically conductive core 7, thereby electrically coupling each leaf 22 to the branch and trunk electrically conductive cores 14, 17.
  • the branches 20 are attachable electrically to the trunk 14 via wiring terminal plugs 19 fitted within the ends of the hollow branches 20 and adapted to be received a female electrical socket (not shown) within the branch mounting receptacles 15 of the tree trunk 14.
  • a key (not shown) on the end of each branch 16 can be received within a slot (not shown) in the corresponding branch mounting receptacle 15 to physically anchor the branch 16 in proper angularity.
  • the plug 19 can have two male electrical terminals that mate with and be
  • V83878WO ⁇ VAN_LAW ⁇ 757017 ⁇ I 8 received in the female electrical socket to establish a series electrical connection with the wiring in adjacent branches 20 and with the conductor 16 in the trunk 14.
  • each solar collector leaf 22 is a multi-layered structure that together functions as a thin film solar collector.
  • each solar collector leaf 22 comprises a base substrate 32, an optional adhesion layer 34, a base electrode 36, a photovoltaic absorber layer 38 incorporating a compound film or ink as will be described in detail below, a junction partner layer 40 and a transparent electrode 42.
  • the electrode layers 36 and 42 are electrically conductive, and a pair of conductors 44 extend from the base electrode 36 and transparent electrode 42 respectively to a plug 46, which electrically couples the solar collector leaf 22 to a socket (not shown) in the branch 20.
  • the base substrate 32 is made of a flexible polymer that is durable enough to withstand the steps of applying the thin-film solar cell layers 34-42 onto the substrate 32.
  • the base substrate 32 can be a heat- durable polymer such as silicones, polyamides (e.g. Nylon) and aromatic flourene-containing polyarylates (e.g. RTP) that are capable of withstanding temperatures of 200-300°C and pressures of 166 MPa to 570 Mpa.
  • the base substrate 32 can also be composed be a flexible polymer substrate or an aluminum foil substrate. Alternatively, the substrate 32 can be made from aluminum foil that is available in rolls of material.
  • the base substrate 32 in one embodiment has a thickness of about 1000 nm to about 5000 nm, and is the same polymer sheet that is used to product conventional artificial leaves. Using the same polymer sheet used to make conventional (non-solar collecting)
  • V83878WO ⁇ VAN_LAW ⁇ 757017U 9 artificial leaves is expected to maintain manufacturing simplicity and reduce the costs of manufacturing the solar collector leaves 22, as much of the same equipment used to make conventional artificial leaves can be used to manufacture the solar collector leaves 22.
  • Adhesive Layer Depending on the material of the substrate 32, it may be useful to coat a surface of the base substrate 32 with an adhesive layer 34 to promote electrical contact between the substrate 32 and the absorber layer 38.
  • the adhesive layer 34 could be a layer of molybdenum.
  • the adhesive layer 34 can also act as a diffusion barrier layer to prevent diffusion of material between the substrate 32 and the electrode 36.
  • the diffusion barrier adhesive layer 34 in this case can be electrically conductive or nonconductive.
  • the adhesive layer may be made out of a variety of materials, including chromium, vanadium, tungsten, and glass, or compounds such as nitrides (including tantalum nitride, tungsten nitride, titanium nitride, silicon nitride, zirconium nitride, and/or hafnium nitride), oxides, carbides, and/or any single or multiple combination of the foregoing.
  • the thickness of this layer can range from 100 nm to 500 nm. This may be deposited using any of a variety of means including sputtering, evaporation, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD)
  • the base electrode layer 36 is an electrically conductive layer suitable for use in thin film solar collectors and can be suitably made of molybdenum.
  • Photovoltaic Absorber Layer After the base electrode layer 36 has been applied to the substrate 32 (with or without the optional adhesive layer 34), a photovoltaic absorber layer 38 is deposited on the base electrode layer 36.
  • the photovoltaic absorber layer is a thin-film type of solar collector which converts sunlight into electricity, and is made of thin-film, light-absorbing semiconductor materials such as copper-indium- gallium-sulfo-di-selenide, Cu(ln, Ga)(S, Se)2,
  • V83878WO ⁇ VAN_LAW ⁇ 757017 ⁇ l 10 also termed CI(G)S(S).
  • This class of solar cells typically has a p-type absorber layer sandwiched between a back electrode layer and an n-type junction partner layer, which in this embodiment are the base electrode layer 36 and the window layer 40.
  • the photovoltaic absorber layer 38 can be composed of silicon nanocrystal particles. Such silicon nanparticles can be applied by a deposition process such as chemical vapour deposition.
  • the photovoltaic absorber layer 38 is formed by applying photovoltaic nanoparticles selected from Group 1 B, IIIA or VIA semiconductor thin films onto the base electrode layer 36 by an inkjet printing process and alternatively by a spray coating process.
  • photovoltaic nanoparticles from Group IV semiconductor thin film materials can be used which can offer higher effectiveness.
  • the substrate 32 should be composed of heat-durable polymers such as polyamides and aromatic flourene-containing polyarylates, to withstand the higher temperature and pressure required to manufacture solar cells from such materials.
  • junction Partner Layer The junction partner layer (otherwise known as a "window layer") 40 serves as a junction partner between the absorber layer 38 and the transparent electrode 42
  • the window layer 40 (sometimes referred to as a junction partner layer) can include inorganic materials such as cadmium sulfide (CdS), zinc sulfide (ZnS), zinc hydroxide, zinc selenide (ZnSe), and n-type organic materials.
  • the transparent electrode 42 is a conductive layer and may be composed of a conductive inorganic material.
  • a transparent conductive oxide such as indium tin oxide (ITO), fluorinated indium tin oxide, zinc oxide (ZnO) or aluminum doped zinc oxide, or a related material.
  • TCO transparent conductive oxide
  • ITO indium tin oxide
  • ZnO zinc oxide
  • aluminum doped zinc oxide or a related material.
  • This material can be deposited using any of a variety of means known in the art including sputtering, evaporation, chemical
  • CVD chemical vapor deposition
  • PVD physical vapor deposition
  • ALD atomic layer deposition
  • Encapsulant The base substrate 32, adhesive layer 34, base electrode layer 36, absorber layer 38, window layer and 40, and transparent electrode layer 42 collectively form a functional solar collector (also known as a "compound film"). All or part of this compound film can be coated with a protective encapsulant to withstand physical abuse and environmental effects.
  • a suitable such encapsulant is DuPont's TM PV5300 Series photovoltaic encapsulant sheets, which are an ionomer based laminating sheet used in the photovoltaic industry.
  • the finished solar collector leaf 22 will comprise both the compound film and an encapsulant skin.
  • the encapsulant comprises a front sheet and a back sheet which envelope the compound film; in another embodiment, the encapsulant comprises only a front sheet which covers only the top of the compound film, which can reduce materials cost.
  • FIG. 6 to 12 illustrate a method 50 of manufacturing the solar energy harvesting tree 10, 12.
  • this method closely resembles a method of manufacturing a conventional artificial tree, except for the steps of applying the layers of the thin film solar collector onto an artificial leaf substrate, and in particular, the step of applying the photovoltaic nanoparticle absorber layer onto the artificial leaf substrate.
  • certain manufacturing processes such as artificial leaf, artificial grass and artificial flower manufacturing lend themselves particularly well to being modified to receiving the thin-film solar collector coatings, thereby transforming the artificial leaf, grass blade, or flower petal into an appropriately-shaped solar collector in a very cost-effective manner.
  • Other manufacturing processes which similarly can be easily modified to receive thin-
  • V83878WO ⁇ VAN ⁇ LAW ⁇ 757017U 12 film solar collector coating including products made of wicker strips, such as wicker furniture, and other vegetation such as artificial lawns.
  • a substrate assembly 53 is prepared by applying the base electrode layer 36 onto the base substrate 32 by using any of a variety of vacuum-based deposition techniques, including sputtering, evaporation, chemical vapor deposition, physical vapor deposition, and electron-beam evaporation.
  • the base substrate can be the same polymer sheet used to produce conventional artificial leaves, provided that such polymer sheet can withstand the heat and pressures encountered during the thin-film solar collector manufacturing process described herein.
  • the adhesive layer 34 can be applied to the base substrate 32 before the base electrode layer 36 is applied.
  • the substrate assembly 53 is wound into a supply roll 68 and is ready to receive the photovoltaic absorber layer 38.
  • an photovoltaic absorber layer application machine 70 is provided to apply the photovoltaic absorber layer 38 onto the substrate assembly 53 by an inkjet application process.
  • the aforementioned photovoltaic nanoparticulate compositions are mixed with known solvents, carriers, dispersants etc. to prepare an ink or a paste that can be applied directly onto the substrate assembly 53.
  • the liquid ink may be made using one or more liquid metals. For example, when forming a CI(G)S(S) based solar collector, an ink may be made starting with a liquid and/or molten mixture of Gallium and/or Indium.
  • Copper nanoparticles may then be added to the mixture, which may then be used as the ink/paste. Copper nanoparticles are available commercially. Alternatively, the temperature of the Cu-Ga-ln mixture may be adjusted (e.g. cooled) until a solid forms. The solid may be ground at that temperature until small nanoparticles (e.g., less than 5 nm) are present. Selenium may be added
  • V83878WO ⁇ VAN_LAW ⁇ 757017 ⁇ 1 13 to the ink and/or a film formed from the ink by exposure to selenium vapor, e.g., before, during, or after annealing.
  • the exposure to selenium vapor may occur in a non-vacuum environment and at atmospheric pressure.
  • the substrate assembly 53 is unwound from the supply roll 68 and extends through a series of inkjet applicators 72 and roller and heater units 74 and onto a take up roll 76.
  • Each inkjet applicator 72 applies or "prints" an ink sub-layer onto the substrate assembly 53; the ink sub-layers collectively form the photovoltaic absorber layer 38.
  • the roller and heater units 76 are used to anneal the different ink sub-layers.
  • Each roller and heater unit 76 anneals the ink sub-layer applied by the adjacent upstream applicator 72 before the next ink sub-layer is deposited by the adjacent downstream applicator 72.
  • the last applicator 72 can apply a layer of chalcogen particles and the last heater unit 76 heats the chalcogen layer and sub-layer as described above.
  • the photovoltaic nanoparticle layer can be applied to the substrate assembly 53 by spray coating photovoltaic nanoparticles in a manner well known in the art.
  • the photovoltaic nano-particular composition, or "nano-powder” may be mixed with a carrier which may typically be a water-based or organic solvent, e.g., water, alcohols, ethylene glycol, etc.
  • a carrier which may typically be a water-based or organic solvent, e.g., water, alcohols, ethylene glycol, etc.
  • This carrier and other agents in this formulation will be evaporated away to form a micro-layer on the substrate.
  • This micro-layer is subsequently be annealed by the roller and heater units 74 to form the sub-layer.
  • the annealing process may involve furnace-annealing, RTP or laser-annealing, microwave annealing, among others, at temperatures of between about 350°C to about 600°C - and preferably between about 400 °C to
  • V83878WO ⁇ VAN_LAW ⁇ 757017 ⁇ 1 14 about 550°C
  • the annealing atmosphere may be inert, e.g., nitrogen or argon). This annealing process may also be done in an environment containing vapour from a Group VIA element (e.g., Se, S, or Te) to reach the desired level of Group VIA elements in the absorber layer.
  • a Group VIA element e.g., Se, S, or Te
  • the total number of printing steps can be modified to construct an absorber layer with bandgaps of differential gradation (not shown).
  • additional sub-layers can be printed (and optionally annealed between printing steps) to create an even more finely-graded bandgap within the absorber layer 38.
  • fewer films e.g. double printing
  • the coating step 54 can occur at room temperature and at atmospheric pressure, or it can be accelerated in various manners, such as but not limited to, through thermal processing, exposure to a laser beam, or heating via IR lamps.
  • the processing occurs at a temperature greater than 375°C but less than the melting temperature of the substrate for a period of 1 minute or less.
  • the atmosphere can be changed to accelerate the processing.
  • the substrate 32 can be at a different temperature during the coating of the raw ink precursor system, so as to enable a variety of substrate materials to be used, such as materials that will either melt or become unstable when the coating material is being deposited.
  • the nanoparticles can be joined by heating them until their edges melt before the naonparticles can fuse, normally at
  • the aforementioned inkjet application process is a process which achieves precise stoichiometric composition over relatively large substrate areas, which can be difficult using traditional vacuum-based deposition processes.
  • Such precise control can be important in cost-effectively constructing a large- area CI(G)S(S)-based solar cell or module, since the elements of the CI(G)S(S) layer must be within a narrow stoichiometric ratio on nano-, meso-, and macroscopic length scale in all three dimensions in order for the resulting cell or module to be highly efficient.
  • the junction partner layer 40 is applied to the absorber layer 38.
  • the junction layer 40 serves as a junction partner between the photovoltaic absorber layer and the transparent electrode layer 42.
  • the junction partner layer 40 may include inorganic materials such as cadmium sulfide (CdS), zinc sulfide (ZnS), zinc hydroxide, zinc selenide (ZnSe), n-type organic materials, or some combination of two or more of these or similar materials, or organic materials such as n-type polymers and/or small molecules.
  • Layers of these materials may be deposited by chemical bath deposition (CBD) or chemical surface deposition, to a thickness ranging from about 2 nm to about 1000 nm, more preferably from about 5 nm to about 500 nm, and preferably from about 10 nm to about 300nm.
  • CBD chemical bath deposition
  • chemical surface deposition to a thickness ranging from about 2 nm to about 1000 nm, more preferably from about 5 nm to about 500 nm, and preferably from about 10 nm to about 300nm.
  • the transparent electrode layer 42 is applied to the junction partner layer 40, to form a multi-layered structure herein referred to as a "compound film" 80.
  • the transparent electrode layer 42 may be inorganic, e.g., a transparent conductive oxide (TCO) such as indium tin oxide (ITO), fluorinated indium tin oxide, zinc oxide (ZnO) or aluminum doped zinc oxide which can be deposited using any of a variety of means including sputtering, evaporation, chemical vapor deposition (CVD).
  • TCO transparent conductive oxide
  • ITO indium tin oxide
  • ZnO zinc oxide
  • aluminum doped zinc oxide aluminum doped zinc oxide
  • the compound film 80 is combined with a encapsulant 82 used as a skin for the artificial foliage, thereby completing the solar collector leaf 22.
  • the encapsulant 82 in this embodiment is made of a copolymer EVA and serves to protect and weather seal the compound film 80.
  • the encapsulant 82 can be made of a thermoplastic polymer PVB or a silicon polymer which are inherently stable to ultraviolet light and do not break down over time.
  • Figure 9 shows the encapsulant sheet 82 or the "skin" that is being combined or laminated with the compound film 80 to form the solar collector leaf 22.
  • a roller 84 applies pressure onto skin 82 and the compound film 80 during the lamination process.
  • the solar collecting leaf 22 can be made more life-like by joining two layers of plastic together under pressure at a predetermined temperature before coating the outer layer with the nanoparticle film.
  • Encapsulant sheets can come in various colors and such a colored sheet can serve as an optional back-skin that is also made of the same material of the front skin 82 to make the leaf appear more lifelike.
  • one layer can be dyed with a color resembling that of a natural tree
  • the other layer (second layer) can be formed using a lighter green color (to mimic a natural tree leaf having an underside that is less exposed to natural sunlight).
  • the fist layer can also include a grain resembling the texture and feel of a natural tree leaf.
  • the grain can also provide the leaf additional strength so that it is resistant to deformation.
  • the first and second layers of plastic skin can be stacked together between a molding tool and an ultrasonic shaker which pre-heats the plastic sheet before the molding takes place. Upon completion of the molding process, the product can be cooled by air through a cooling fan.
  • step 58 in Figure 6 and Figure 10 generally, the combined compound film 80 and plastic skin 92 form a broad sheet or ribbon that is stamped or cut into shapes resembling leaves; each of these shapes serve as the solar collector leaves 22 (Figure 10 shows a plurality of broad leaves being formed; however leaves resembling the needle-like evergreen leaves shown in
  • V83878WO ⁇ VAN_LAW ⁇ 757017M 17 Figure 3 can be easily formed by this technique as well).
  • a string of solar collecting leaves 22 can be very easily cut from continuously running sheet of the compound film 80 and plastic skin 92.
  • the conductive wires extending from each electrode 36, 42 can be soldered in place at this step or other means known in the art to electrical couple the electrodes 36, 42 of the leaves to the conductors in the branches 20 can be provided as known to one skilled in the art.
  • this technique can also be applied to other floras such as plants, flowers, bushes and the like.
  • various plastic pipes and joints can be utilized and modified to make the tree more elegant and lifelike by coating these pipes with a thin layer of foam and then heating it briefly with a blast of flame. These coatings can also help to improve the ruggedness of the underlying pipes and protect them from any damages during shipping.
  • the technique may involve a greater number of pipes and additional vines for decorative purposes.
  • the techniques of attaching the leaves and allowing the current from the artificial leaves can remain the same.
  • this stamping / cutting technique can be used to fabricate various shapes, which can be used to form other solar collecting products.
  • the ribbon / sheet can be cut into thin strips, which can then be woven over a frame to form a solar collecting wicker-type furniture product, such as a chair or a table. Therefore, the aforementioned method can be used to manufacture not just solar energy harvesting artificial trees but also anything which can be fabricated from the compound film + plastic skin ribbon of material.
  • products which include the manufacture of a component that has a substrate which can withstand the photovoltaic nanoparticle coating process described above can be a suitable candidate for being converted into a solar energy harvesting product.
  • step 60 in Figure 6 and Figure 11 a plurality of leaves 22 is assembled together onto the branch 20. As noted above, the end of each leaf 22
  • V83878WO ⁇ VANJ_AW ⁇ 757017 ⁇ 1 18 has an electrical plug 46 which electrically couples to a socket on the branch 22, and the end of each leaf 22 has a key shape which matches a slot shape leaf receptacle in the branch 20, thereby enabling each leaf 22 to be physically and electrically coupled to the branch 20.
  • the trunk 14 and trunk base 30 are manufactured.
  • the rough bark on an artificial tree is created by coating the artificial tree surface with a thin layer of plastic foam.
  • the foam is exposed to a blast of concentrated heat sufficient to collapse part of the foam structure.
  • This partially collapsed foam structure is than coated, either sprayed or painted with a brush ( Figure 12(d) and 12(e) respectively), with a colored paint, such as a brown paint to simulate the color of the tree bark, and used to complete the product ( Figure 12(e)).
  • thermoplastic foams such as thermoplastic foams, thermosetting foams and mixtures thereof.
  • Thermosetting foams are generally preferred because once they become set after partial collapsing with the blast of concentrated heat, they are rather impervious to further deformation notwithstanding later heat from a warm office or home environment.
  • Thermoplastic foams have a tendency to further deform with heat which makes them poor candidates albeit still somewhat useful in certain instance.
  • polyurethane foam which is a thermosetting foam product of a polyester resin and an isocyanate such as toluene diisocyanate or an amide such azodicarbonamide.
  • the foaming formulation consist of at least one fire-retardant compound such as antimony trioxide, stannous oxide, aluminum oxide trihydrate, and zinc borate. These materials, when used in appropriate quantities to render the assembly of parts non-flammable, do not degrade the foam formulation.
  • fire-retardant compound such as antimony trioxide, stannous oxide, aluminum oxide trihydrate, and zinc borate.
  • Figure 12(a) shows a plurality of tubing to be wrapped about a rigid tube, usually by hand.
  • the flexible plastic tubing simulates vines and branches growing up and about the Ficus tree central trunk.
  • the plurality of flexible plastic tubing may be comprised of tubing of many different nominal diameters, from very small or thin to a thickness approaching one-third to one-half the nominal diameter of central Ficus tree trunk-pipe.
  • the wrapping is usually done by hand and the flexible tubes are usually tied tightly to the trunk tube at both distal ends thereof, and then one end of the tree trunk acts as the bottom of the tree and the other end represents the top of the tree.
  • the step of exposing the foam to a blast of concentrated heat shown in Figure 12(c) to collapse part of the foam structure is done by exposing the foam to a continuous blast of flame-generated heat that is passed back and forth across the foam. This can be accomplished by having a person sweep a flame of burning propane or natural gas across the foam much the same as a painter would do with a brush.
  • FIG. 12(d) shows the assembly laid on a table and the operator applying colored paint to simulate the brown color of the bark. It has been found that applying the paint with a paint brush creates areas of light color and areas of deep color to be developed in the surface further adding to the texture simulating real bark.
  • FIG. 12(e) shows assembly fully built, coated with foam, the foam textured and the paint applied and dried.
  • the lower end of the trunk 14 can be coupled to a rotating base stand 30 to allow the tree 10, 12 to freely rotate both in a clockwise and counterclockwise direction at a desired speed using an electrical motor (not shown) coupled thereto.
  • the motor can cause the tree to rotate about its
  • the rotating base 30 can rotate in a single direction only (either clockwise or counterclockwise) or it can rotate in both the clockwise and counterclockwise directions. Rotating bases are generally well known in the industry, and thus they will not be described in more detail herein.
  • Contacts are available to direct the current collected from the solar collecting leaves 22, either fed directly into an inverter (not shown) for "grid tied” or “off grid” applications - or collected using a storage device such as a battery or an ultra capacitor. Users can vary the speed and direction of the rotating base 30 to increase the solar energy collected and track it using a user friendly GUI or digital dashboard (not shown) communicatively coupled to the tree. The GUI can also be helpful to diagnose and detect any fault or incident in the system. Alternatively, users can also track the solar energy harvesting tree output in real time through the internet when connected to a suitable smartgrid platform (such as describe above).
  • the branches 20 are attached physically and electrically to the trunk 14 in the manner noted above.
  • the lower end of the trunk 14 can be optionally inserted in a stand 30 for providing vertical stability.
  • the stand 30 can be rotatable.
  • the solar energy harvesting tree 10, 12 allows for modular construction and compact packaging by manufacturers for ease of shipment, storage, and consumer marketing. It is easy to install, disassemble and store by the end user. But for those who do not wish to disassemble, limbs and branches are formed with cutson their underneath sides to permit upward and inward folding of the limbs and branches about the trunk to form a compact storage arrangement.
  • branches 20 are not hollow, but instead are solid with the conductors molded inside.
  • a solar energy harvesting tree can be
  • V83878WO ⁇ VAN_LAW ⁇ 757017 ⁇ ! 21 manufactured by manufacturing the solar collector leaves 22 in the manner described, and attaching such leaves 22 to an existing artificial tree having electrical wiring, such as an artificial Christmas tree with integrated LED lighting.
  • an artificial Christmas tree some or all of the leaves are embedded with LED lights, which are electrically coupled to electrical conductors in the branch and trunk of the Christmas tree; such a Christmas tree, for example can be modified into a solar energy harvesting tree by replacing the LED equipped leaves with the solar collector leaves 22.
  • the electrical circuitry of such an artificial Christmas tree can be modified to transmit electricity collected by the solar collecting leaves 22 and out of the tree, instead of transmitting electricity to LED lights integrated into branches of the Christmas tree.
  • these LED lights are replaced by the solar connecting leaves 22.
  • One of these wires is connected in series with one of the wires of an adjacent set of parallel wires connecting the solar leaves 22 in parallel.
  • the other of this second set of parallel wires is connected in series with one of wires of another adjacent set of parallel wires connecting the solar leaves 22 in parallel.
  • twelve sets of parallel circuits each connecting forty solar leaves in parallel would be incorporated in this artificial solar tree, with the other wires of the first set of parallel wires and the twelfth set of parallel wires being connected across an inexpensive power conditioner in a control box .
  • Such a power conditioner may be adjusted to vary the voltage level.
  • the improved tree of this invention would be constructed in parts, and the parts packaged in a compact container.
  • An end user can open the package, place the rotating stand 30 on the floor, secure the control box to the stand, and place the lower end of the trunk 14 in the control box, thereby also establishing electrical connection between the trunk wires and the power conditioner.
  • the various limbs 20 would be attached to the tree by inserting their wiring terminal plugs in the receptacles of the trunk 14, thereby also establishing electrical connections for the lights on the limb's branches .
  • the upper portion of the tree would be put in place physically and electrically by connecting the lower end of the trunk portion with the upper end of
  • All of the solar collecting leaves 22 could now be connected in groups between the wires of various sets of parallel wires, which wires are each connected in series with a wire of a different electrically adjacent set of parallel wires or one of the contacts of the power conditioner, through the trunk wires . If the cord and plug are now inserted into an device or mains, and the power conditioner will feed the power into the mains.
  • the solar collector leaves 22 of the solar energy harvesting tree 10, 12 captures sunlight, as shown in step 82 of the flow diagram 80 of Figure 7.
  • the different layers of the leaf's substrate assembly create a potential difference.
  • the electrons flow towards the electrodes 36, 42 embedded in each leaf 22.
  • the current flows at step 88 from the electrodes 36, 42 in each leaf 22, through the conductor wires and plug 46 into the branches 20 and trunk 14 of the artificial tree 10. 12.
  • the electrons are captured by a battery storage unit.
  • the battery storage unit stores the charge and releases the power back to the owner or to the grid through a power conditioning unit or system.
  • the power conditioning system can include a plurality of power conditioning devices having technology and hardware which are well known in the art.
  • the power conditioning device can optionally include electrical relaying, fault isolation protection, voltage regulation equipment, and metering.
  • This power conditioning system can also include a safety and security system that provides a plurality of fail-safe features (such as sensors coupled to switches) that detects a failure in the system and effectively shuts down the distributed generator or a portion thereof in an emergency situation.
  • a failure in the system can occur when current flows in the opposite direction where the reach of the relay is shortened, thereby leaving high impedance faults undetected. For example, when a utility breaker is opened, a portion of the utility system remains energized even though it may be isolated from the remainder of the utility system. Such energized system can cause injuries to the users, utility personnel, and the system operator.
  • V83878WO ⁇ VAN_LAW ⁇ 757017M 23 security system thus would detect this failure and shut down the appropriate portion of the system.
  • a docking station (not shown) can serve as a conduit to an urban energy farm whereby the solar energy harvesting tree 10, 12 can offer new sources of income.
  • the harvested energy generated from the solar energy harvesting trees 10, 12 can be stored, bidded and sold to various interested parties through the docking system and managed and sold through a web 2.0 meta-exchange centre.
  • owners of these solar energy harvesting trees 10, 12 can subscribe to various levels of microfarming options - and at the very basic tier, it can be provided to them as a freebie or a low cost if they agree on a longer term fixed subscription plan.
  • owners of solar trees can take on a long term farming contract with a power grid at a fixed futures price.
  • a digital dashboard and power monitoring system includes a programmable microcontroller to manage power consumption and storage in the distributed power grid.
  • An exemplary and suitable digital dashboard and power monitoring system is described in U.S. Patent Application Serial No. 12/618,697 (commonly owned by the assignee of the present application), which is hereby incorporated by reference.
  • measurements are received from a plurality of geographically distributed energy management controllers coupled to the renewable energy devices, and these measurements are processed and displayed on a graphical user interface (e.g., a demand response dashboard), such as on the user communication device (or black box).
  • the digital dashboard and power monitoring software system gives commands to either discharge (or conversely charge) each renewable energy device's stored energy into the power grid in accordance with user defined rules and requirements (such as economics, during routine backups, load balancing, load shedding, and limits).
  • the power delivery and demand response dashboard i.e., graphical interface
  • the power delivery and demand response dashboard is available online (i.e., accessible via the communications network) to each user and system operator for decision-making and for diagnosis and detection of any fault or incident in the system.
  • the digital dashboard and power monitoring system provides inputs to the intelligent
  • V83878WO ⁇ VAN_LAW ⁇ 757017 ⁇ 1 24 management system through communicating with a plurality of building automation and metering systems to collect, archive, analyze and communicate energy information and storing this in a database.
  • the graphical user interface can also display information to (or educate) building managers on energy use and demand charges.

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Abstract

A method for manufacturing a product for harvesting solar energy and for at least one other function, such as artificial vegetation, comprises the steps of forming a solar collector and combining the solar collector with other components of the product so that the product performs the at least one other function and harvests solar energy. The step of forming the solar collector comprises: selecting a component of the product to serve as a base substrate, the selected component being suitable to withstand a photovoltaic nanoparticle coating application step; coupling an electrically conductive base electrode layer to the base substrate; applying at least one coating of photovoltaic nanoparticles onto the base electrode layer to form a photovoltaic absorber layer; coupling a junction partner layer to the photovoltaic absorber layer; and coupling an electrically conductive transparent electrode layer to the junction partner layer, such that the photovoltaic absorber layer is in electrical communication with the base electrode layer and transparent electrode layer.

Description

PHOTOVOLTAIC NANOPARTICLE-COATED PRODUCT AND METHOD OF
MANUFACTURING SAME
Field of the Invention
[001] This invention relates generally to a photovoltaic nanoparticle-coated product such as artificial vegetation, and a method of manufacturing same.
Background of the Invention
[002] The sun provides nearly unlimited energy. However, traditional solar panel products are relatively expensive and have not been widely adopted.
[003] Newer solar collector technologies such as thin-film photovoltaic cells show promise. Such thin-film cells are made by depositing one or more thin layers of photovoltaic material onto a substrate. Such thin film photovoltaic cells are commercially available for installation onto the roofs of buildings, and semitransparent thin film photovoltaic cells are being proposed as glazing for windows. However, such applications still are very specialized and thus require significant capital cost to implement, which serves as a continued barrier to wide adoption.
Summary of the Invention
[004] According to one aspect of the invention there is provided a method for manufacturing a product for harvesting solar energy and for at least one other function. For example, the product can be artificial vegetation such as a tree, lawn, flowers, and shrubbery and the other function can be to provide an aesthetic substitute for natural vegetation. In another example, the product can be outdoor furniture, and the other function is to furnish a habitat. The method comprises the steps of forming a solar collector and combining the solar collector with other components of the product so that the product performs the at least one other function and harvests solar energy. The step of forming the solar collector comprises: selecting a component of the product to serve as a base
V83878WOWAN LAW\ 757017\1 1 substrate, the selected component being suitable to withstand a photovoltaic nanoparticle coating application step; coupling an electrically conductive base electrode layer to the base substrate; applying at least one coating of photovoltaic nanoparticles onto the base electrode layer to form a photovoltaic absorber layer; coupling a junction partner layer to the photovoltaic absorber layer; and coupling an electrically conductive transparent electrode layer to the junction partner layer, such that the photovoltaic absorber layer is in electrical communication with the base electrode layer and transparent electrode layer.
[005] According to another aspect of the invention there is provided a product for harvesting solar energy and for at least one other function, such as the aforementioned artificial vegetation and outdoor furniture. The product comprises a solar collector and at least one other component that when combined form the product and enables the product to serve the at least one other function. The solar collector comprises: a component of the product selected to serve as the base substrate; an electrically conductive base electrode layer coupled to the base substrate; a photovoltaic absorber layer coupled to the base electrode layer comprising at least one coating of photovoltaic nanoparticles; a junction partner layer coupled to the photovoltaic absorber layer; and an electrically conductive transparent electrode layer coupled to the junction partner layer; wherein the absorber layer is in electrical communication with the base electrode layer and the transparent electrode layer. The component selected to be the base substrate must be suitable to withstand a photovoltaic nanoparticle coating application.
[006] Examples of products for solar energy harvesting according to the above aspect of the invention include artificial vegetation such as trees or shrubbery that can be manufactured inexpensively by integrating the photovoltaic nanoparticles coating application step into a conventional process for manufacturing the artificial vegetation. Such artificial vegetation can be used outdoors to harvest solar energy. Such trees and shrubbery can be relatively inexpensive to manufacture and are aesthetically pleasing. Additionally, such
V83878WO\VAN_LAW\ 757017\1 2 nanotechnology in the form of thin films can also be embedded on other conventional outdoor objects, such as but not limited to walls and windows of a building; in contrast to existing techniques for attaching thin film solar collectors to walls or windows of buildings, the products according to aspects of the invention utilize components of the walls or windows as the base substrate. Other products include patio furniture, leisure goods, and toys; one specific example of such products is wicker furniture in which the wicker serves as the base substrate, and the solar collector is in the form of strips which are wrapped around a frame of the wicker furniture.
[007] By incorporating a thin solar film coating into aesthetically beautiful and natural artificial trees and other products, clunky silicon-based solar panels mounted on a roof will not be needed. Since the installation cost of a conventional solar cell panel is currently about twice the cost of the solar cell panels, objects manufactured according to aspects of the present invention can help significantly reduce the overall cost of harvesting solar energy.
[008] Advantageously, aspects of the present invention can make use of and be implemented with either new or existing production equipment and technology that are already commercially available. For example, existing artificial tree manufacturing equipment can be used to make much of the solar energy harvesting artificial tree according to an aspect of the invention. The solar energy harvesting product includes a photovoltaic nanoparticle absorber layer that can be inkjet coated or spray-painted onto a substrate assembly to make very thin solar collectors. By shaping such solar collectors into a leaf shape, there is the potential to mass-produce the solar energy harvesting artificial tree with leaves doped with the photovoltaic nanoparticles by using large printing presses (similar to those used by newspapers). The nanoparticles can in one aspect include a specialized ink made up of silicon nanocrystals. These nanoparticles can be made in a variety of ways, and in one typical commercial embodiment, obtained through assembling a group of molecules that contain silicon and then burning off everything except the silicon. This process involves blasting silicon rich
V83878WO\VAN_LAW\ 757017\1 3 molecules with an electromagnetic field (at a radio frequency), which gives off a gas in which some of the molecules have lost an electrical charge. Whilst charged, the molecules are extremely reactive and, with a bit of careful chemistry, can be coerced into forming nanoparticles. Therefore, by suspending these nanoparticles in a solvent to make ink, silicon films can be printed using a commercially available silkscreen printer or an inkjet printer.
[009] Additionally, aspects of the present invention can use a photovoltaic nanoparticle coating process having a much lower melting temperatures, between 300°C and 900°C, for melting everything but the silicon molecules compared with bulk silicon which is typically over 1400°C. This can significantly reduce the cost of heating, which is a substantial cost in the production of traditional crystalline silicon solar cells.
[0010] Alternatively, the photovoltaic nanoparticles can be selected from a group of materials that belong to periodic table group IB, IIIA, IV or VIA. In particular, the photovoltaic absorber layer composition can be based on copper indium gallium selenide or "CI(G)S(S)". CI(G)S(S) is particularly advantageous since it is a direct band gap semiconductor, which needs much less material to make a solar cell. Also, CI(G)S(S) inks typically are semi-transparent.
[0011] Another aspect of this invention includes applying the photovoltaic nanoparticles onto the substrate assembly by an inkjet application or printing process. This inkjet printing technique can produce a leaf-shaped solar collector that mimics the natural colors of real tree leaves by depositing the active layer of the solar cell devices using a conventional and commercially available process that is similar to those that are being used in the production of electronic devices, magnetic media and photographic film, among other products. This way, using a suitable dye, or semi-transparent materials such as CI(G)S(S) , the upper layer can maintain the true color and texture of natural tree leaves.
[0012] Advantageously, the systems and methods of the present invention can be inexpensive since it makes use of and can be implemented with either new or
V83878WO\VAN_LAW\ 757017\ 1 4 existing artificial tree production equipment and coating technologies that are already commercially in use.
Brief Description of the Drawings
[0013] Figure 1 depicts an outdoor artificial solar energy harvesting tree according to one embodiment of the present invention.
[0014] Figure 2 depicts an outdoor artificial solar energy harvesting tree according to another embodiment of the present invention.
[0015] Figure 3 shows a portion of leaves, branches and trunk, and electrical and physical connections of the solar energy harvesting tree of Figure 2.
[0016] Figure 4 depicts a sectional view of a solar collector leaf of the solar energy harvesting trees shown in Figures 1 and 2.
[0017] Figure 5 depicts a connection diagram for connecting the solar energy harvesting tree to a power grid according to an embodiment of the present invention.
[0018] Figures 6 depicts a flow diagram of a method for manufacturing the solar energy harvesting tree according to an embodiment of the present invention.
[0019] Figure 7 depicts a method for forming a substrate assembly of the solar collector leaf.
[0020] Figure 8 depicts a method for forming a photovoltaic absorber layer of the solar collector leaf.
[0021] Figure 9 depicts a method for forming a solar collector sheet from a compound film sheet and an encapsulant sheet.
[0022] Figure 10 depicts a method for forming each solar collector leaf from the sheet shown in Figure 9.
V83878WO\VAN_LAW\ 757017\I 5 [0023] Figure 11 depicts a perspective view of multiple solar collector leaves mounted to a branch of the solar energy harvesting tree shown in Figure 2.
[0024] Figures 12(a) to (e) depicts various steps in forming a trunk of the solar energy harvesting tree.
[0025] Figure 13 depicts a flow diagram of a method for operating an artificial solar energy harvesting tree according to an embodiment of the present invention.
Detailed Description of Exemplary Embodiments
Apparatus
[0026] The present invention may be understood more readily by reference to the following detailed description of the invention taken in connection with the accompanying drawing figures, which form a part of this disclosure. It is to be understood that this invention is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed invention. Also, as used in the specification including the appended claims, the singular forms "a," "an," and "the" include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" or "approximately" one particular value and/or to "about" or "approximately" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment.
[0027] The embodiments described herein relate to products coated with photovoltaic nanoparticles and a method of manufacturing such products to transform such products into solar energy harvesting means. Such products
V83878WO\VAN_LAW\ 757017\ l 6 have components that can serve as a coatable substrate layer and that can withstand a photovoltaic nanoparticle coating process; and in particular include consumer products such as artificial trees, artificial grass, artificial flowers and other artificial vegetation. While the embodiments described herein are artificial trees with photovoltaic nanoparticle coated leaves, it will be understood to one skilled in the art that the photovoltaic nanoparticle coating can be applied to other consumer products with similarly coatable components, such as the wicker strips of wicker chairs and other wicker products.
[0028] Referring now to Figures 1 and 2, two artificial solar energy harvesting trees according to embodiments of the invention are shown. The solar energy harvesting tree 10 shown in Figure 1 mimics a ficus tree ("artificial solar energy harvesting ficus tree"), and the tree 12 shown in Figure 2 mimics an evergreen ("artificial solar energy harvesting evergreen tree"). Generally, the artificial ficus tree 10 can be produced by forming a thin layer of plastic foam on the surface of plastic tubing and serving as a tree limb, including a tree trunk 14 and vines and branches and then exposing the foam to a blast of flame or concentrated heat to cause the foam to partially melt and collapse forming a rough surface that resembles the rough surface of the limbs of a real ficus tree. In addition, metal wires can be inserted into the vines and branches to make them more life like in arrangement. The foam can include fire retardants to render the artificial ficus tree 10 flame retardant. Similarly, the artificial evergreen tree 12 has a plastic tubing that forms limbs including a tree trunk 14 and branches 20 connected to the trunk 14.
[0029] Both the artificial solar energy harvesting ficus tree 10 and the artificial solar energy harvesting evergreen tree 2 are provided with leaf-shaped thin-film solar collectors connected to a branch 20. Electrical conductors 16 extend through the hollow trunk 14, through the branches 20 and to each solar collecting leaf 22, thereby electrically connecting each solar collecting leaf 22 to an electrical cable 26 extending from the base 30 of the solar energy harvesting tree 10, 12.
V83878WO\VAN_LAW\ 757017\1 7 [0030] The manufacture and structure of the solar collecting leaves 22 will now be described with reference to the solar energy harvesting evergreen tree 12; however, one skilled in the art can readily apply this description to the manufacture of the solar collecting ficus tree 10 or of another type of artificial tree or similar product.
[0031] Figure 3 shows a part of the trunk 14, one branch 20 and six leaves 22 of the artificial evegreen tree 12. The solar energy harvesting tree 12 has a hollow trunk 14 with the inner electrically conductive core 16 extending therethrough and with multiple branch mounting receptacles 15 in the trunk 14. The solar energy harvesting tree 12 also has a plurality of hollow braches 20 each with an electrically conductive core 17 extending therethrough and with multiple leaf mounting receptacles 18 in each branch 20 (one leaf 22 in Figure 3 is shown unattached to the branch 20 to better illustrate the leaf mounting receptacle 18). Each branch 20 has one end physically connectable to the trunk 14 at the branch mounting receptacle 15, such that the branch's electrically conductive core 17 is electrically coupled to the trunk's electrically conductive core 16.
[0032] The solar energy harvesting tree 12 also comprises multiple solar collector leaves 22 each physically coupled to a respective branch 20 at the branch mounting receptacle 18. An electrical conductor extends from the leaf 18 through the branch mounting receptacle and contacts the branch's electrically conductive core 7, thereby electrically coupling each leaf 22 to the branch and trunk electrically conductive cores 14, 17.
[0033] The branches 20 are attachable electrically to the trunk 14 via wiring terminal plugs 19 fitted within the ends of the hollow branches 20 and adapted to be received a female electrical socket (not shown) within the branch mounting receptacles 15 of the tree trunk 14. A key (not shown) on the end of each branch 16 can be received within a slot (not shown) in the corresponding branch mounting receptacle 15 to physically anchor the branch 16 in proper angularity. The plug 19 can have two male electrical terminals that mate with and be
V83878WO\VAN_LAW\ 757017\ I 8 received in the female electrical socket to establish a series electrical connection with the wiring in adjacent branches 20 and with the conductor 16 in the trunk 14.
[0034] Some or all of the leaves are solar collectors which can collect light and convert the light into electricity for transmission through the conductive cores 16, 17 and out of the solar energy harvesting tree 12 via cable 26. The non-solar collecting leaves simply comprises a plastic substrate that has been dyed and molded to resemble a real leaf, in a manner well known in the art. In contrast, each solar collector leaf 22 is a multi-layered structure that together functions as a thin film solar collector.
[0035] Referring now to Figure 4, each solar collector leaf 22 comprises a base substrate 32, an optional adhesion layer 34, a base electrode 36, a photovoltaic absorber layer 38 incorporating a compound film or ink as will be described in detail below, a junction partner layer 40 and a transparent electrode 42. The electrode layers 36 and 42 are electrically conductive, and a pair of conductors 44 extend from the base electrode 36 and transparent electrode 42 respectively to a plug 46, which electrically couples the solar collector leaf 22 to a socket (not shown) in the branch 20.
[0036] Base Substrate. The base substrate 32 is made of a flexible polymer that is durable enough to withstand the steps of applying the thin-film solar cell layers 34-42 onto the substrate 32. The base substrate 32 can be a heat- durable polymer such as silicones, polyamides (e.g. Nylon) and aromatic flourene-containing polyarylates (e.g. RTP) that are capable of withstanding temperatures of 200-300°C and pressures of 166 MPa to 570 Mpa. The base substrate 32 can also be composed be a flexible polymer substrate or an aluminum foil substrate. Alternatively, the substrate 32 can be made from aluminum foil that is available in rolls of material. The base substrate 32 in one embodiment has a thickness of about 1000 nm to about 5000 nm, and is the same polymer sheet that is used to product conventional artificial leaves. Using the same polymer sheet used to make conventional (non-solar collecting)
V83878WO\VAN_LAW\ 757017U 9 artificial leaves is expected to maintain manufacturing simplicity and reduce the costs of manufacturing the solar collector leaves 22, as much of the same equipment used to make conventional artificial leaves can be used to manufacture the solar collector leaves 22.
[0037] Adhesive Layer Depending on the material of the substrate 32, it may be useful to coat a surface of the base substrate 32 with an adhesive layer 34 to promote electrical contact between the substrate 32 and the absorber layer 38. For example, when the substrate 32 is made of aluminum the adhesive layer 34 could be a layer of molybdenum.
[0038] The adhesive layer 34 can also act as a diffusion barrier layer to prevent diffusion of material between the substrate 32 and the electrode 36. The diffusion barrier adhesive layer 34 in this case can be electrically conductive or nonconductive. In this case, the adhesive layer may be made out of a variety of materials, including chromium, vanadium, tungsten, and glass, or compounds such as nitrides (including tantalum nitride, tungsten nitride, titanium nitride, silicon nitride, zirconium nitride, and/or hafnium nitride), oxides, carbides, and/or any single or multiple combination of the foregoing. The thickness of this layer can range from 100 nm to 500 nm. This may be deposited using any of a variety of means including sputtering, evaporation, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD)
[0039] Base Electrode Layer. The base electrode layer 36 is an electrically conductive layer suitable for use in thin film solar collectors and can be suitably made of molybdenum.
[0040] Photovoltaic Absorber Layer After the base electrode layer 36 has been applied to the substrate 32 (with or without the optional adhesive layer 34), a photovoltaic absorber layer 38 is deposited on the base electrode layer 36. The photovoltaic absorber layer is a thin-film type of solar collector which converts sunlight into electricity, and is made of thin-film, light-absorbing semiconductor materials such as copper-indium- gallium-sulfo-di-selenide, Cu(ln, Ga)(S, Se)2,
V83878WO\VAN_LAW\ 757017\l 10 also termed CI(G)S(S). This class of solar cells typically has a p-type absorber layer sandwiched between a back electrode layer and an n-type junction partner layer, which in this embodiment are the base electrode layer 36 and the window layer 40. Alternatively, the photovoltaic absorber layer 38 can be composed of silicon nanocrystal particles. Such silicon nanparticles can be applied by a deposition process such as chemical vapour deposition.
[0041] As will be discussed in more detail below, the photovoltaic absorber layer 38 is formed by applying photovoltaic nanoparticles selected from Group 1 B, IIIA or VIA semiconductor thin films onto the base electrode layer 36 by an inkjet printing process and alternatively by a spray coating process. In another embodiment, photovoltaic nanoparticles from Group IV semiconductor thin film materials can be used which can offer higher effectiveness. When using Group IV nanoparticles, the substrate 32 should be composed of heat-durable polymers such as polyamides and aromatic flourene-containing polyarylates, to withstand the higher temperature and pressure required to manufacture solar cells from such materials.
[0042] Junction Partner Layer. The junction partner layer (otherwise known as a "window layer") 40 serves as a junction partner between the absorber layer 38 and the transparent electrode 42 The window layer 40 (sometimes referred to as a junction partner layer) can include inorganic materials such as cadmium sulfide (CdS), zinc sulfide (ZnS), zinc hydroxide, zinc selenide (ZnSe), and n-type organic materials.
[0043] Transparent Electrode Layer. The transparent electrode 42 is a conductive layer and may be composed of a conductive inorganic material. One suitable such material is a transparent conductive oxide (TCO) such as indium tin oxide (ITO), fluorinated indium tin oxide, zinc oxide (ZnO) or aluminum doped zinc oxide, or a related material. This material can be deposited using any of a variety of means known in the art including sputtering, evaporation, chemical
V83878WO\VAN LAW\ 757017\1 1 1 vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD).
[0044] Encapsulant The base substrate 32, adhesive layer 34, base electrode layer 36, absorber layer 38, window layer and 40, and transparent electrode layer 42 collectively form a functional solar collector (also known as a "compound film"). All or part of this compound film can be coated with a protective encapsulant to withstand physical abuse and environmental effects. A suitable such encapsulant is DuPont's ™ PV5300 Series photovoltaic encapsulant sheets, which are an ionomer based laminating sheet used in the photovoltaic industry. As will be discussed below, the finished solar collector leaf 22 will comprise both the compound film and an encapsulant skin. In one embodiment, the encapsulant comprises a front sheet and a back sheet which envelope the compound film; in another embodiment, the encapsulant comprises only a front sheet which covers only the top of the compound film, which can reduce materials cost.
Method Of Manufacture
[0045] Figures 6 to 12 illustrate a method 50 of manufacturing the solar energy harvesting tree 10, 12. By way of general comment, it can be seen from this description that this method closely resembles a method of manufacturing a conventional artificial tree, except for the steps of applying the layers of the thin film solar collector onto an artificial leaf substrate, and in particular, the step of applying the photovoltaic nanoparticle absorber layer onto the artificial leaf substrate. It will also be seen that certain manufacturing processes such as artificial leaf, artificial grass and artificial flower manufacturing lend themselves particularly well to being modified to receiving the thin-film solar collector coatings, thereby transforming the artificial leaf, grass blade, or flower petal into an appropriately-shaped solar collector in a very cost-effective manner. Other manufacturing processes which similarly can be easily modified to receive thin-
V83878WO\VAN^LAW\ 757017U 12 film solar collector coating including products made of wicker strips, such as wicker furniture, and other vegetation such as artificial lawns.
[0046] Referring to step 52 in Figure 6 and Figure 7 generally, a substrate assembly 53 is prepared by applying the base electrode layer 36 onto the base substrate 32 by using any of a variety of vacuum-based deposition techniques, including sputtering, evaporation, chemical vapor deposition, physical vapor deposition, and electron-beam evaporation. As noted above, the base substrate can be the same polymer sheet used to produce conventional artificial leaves, provided that such polymer sheet can withstand the heat and pressures encountered during the thin-film solar collector manufacturing process described herein.
[0047] Optionally, the adhesive layer 34 can be applied to the base substrate 32 before the base electrode layer 36 is applied.
[0048] Once the substrate assembly 53 has been prepared, it is wound into a supply roll 68 and is ready to receive the photovoltaic absorber layer 38.
[0049] Referring now to step 54 in Figure 6 and Figure 8 generally, an photovoltaic absorber layer application machine 70 is provided to apply the photovoltaic absorber layer 38 onto the substrate assembly 53 by an inkjet application process. In the inkjet application process, the aforementioned photovoltaic nanoparticulate compositions are mixed with known solvents, carriers, dispersants etc. to prepare an ink or a paste that can be applied directly onto the substrate assembly 53. The liquid ink may be made using one or more liquid metals. For example, when forming a CI(G)S(S) based solar collector, an ink may be made starting with a liquid and/or molten mixture of Gallium and/or Indium. Copper nanoparticles may then be added to the mixture, which may then be used as the ink/paste. Copper nanoparticles are available commercially. Alternatively, the temperature of the Cu-Ga-ln mixture may be adjusted (e.g. cooled) until a solid forms. The solid may be ground at that temperature until small nanoparticles (e.g., less than 5 nm) are present. Selenium may be added
V83878WO\VAN_LAW\ 757017\1 13 to the ink and/or a film formed from the ink by exposure to selenium vapor, e.g., before, during, or after annealing. The exposure to selenium vapor may occur in a non-vacuum environment and at atmospheric pressure.
[0050] ] In the photovoltaic absorber layer application machine 70, the substrate assembly 53 is unwound from the supply roll 68 and extends through a series of inkjet applicators 72 and roller and heater units 74 and onto a take up roll 76. Each inkjet applicator 72 applies or "prints" an ink sub-layer onto the substrate assembly 53; the ink sub-layers collectively form the photovoltaic absorber layer 38. The roller and heater units 76 are used to anneal the different ink sub-layers. Each roller and heater unit 76 anneals the ink sub-layer applied by the adjacent upstream applicator 72 before the next ink sub-layer is deposited by the adjacent downstream applicator 72. As shown in Fig 8, the last applicator 72 can apply a layer of chalcogen particles and the last heater unit 76 heats the chalcogen layer and sub-layer as described above.
[0051] Alternatively, it is possible to deposit the entire film through an ink-jet process and then deposit the chalcogen-containing layer as shown in fig 8 and then heat all the different layers together to form the IB-IIIA-chalcogenide compound film used for the photovoltaic absorber layer.
[0052] Instead of inkjet printing, the photovoltaic nanoparticle layer can be applied to the substrate assembly 53 by spray coating photovoltaic nanoparticles in a manner well known in the art.
[0053] The photovoltaic nano-particular composition, or "nano-powder" may be mixed with a carrier which may typically be a water-based or organic solvent, e.g., water, alcohols, ethylene glycol, etc. This carrier and other agents in this formulation will be evaporated away to form a micro-layer on the substrate. This micro-layer is subsequently be annealed by the roller and heater units 74 to form the sub-layer. The annealing process may involve furnace-annealing, RTP or laser-annealing, microwave annealing, among others, at temperatures of between about 350°C to about 600°C - and preferably between about 400 °C to
V83878WO\VAN_LAW\ 757017\1 14 about 550°C (The annealing atmosphere may be inert, e.g., nitrogen or argon). This annealing process may also be done in an environment containing vapour from a Group VIA element (e.g., Se, S, or Te) to reach the desired level of Group VIA elements in the absorber layer.
[0054] While in this embodiment there are shown three applicators 72 and three roller and heater units 74, a different number of applicators 72 and roller and heater units 74 can be provided depending on the number of sub-layers of the absorber layer 38 that are desired. Further, the total number of printing steps can be modified to construct an absorber layer with bandgaps of differential gradation (not shown). For example, additional sub-layers can be printed (and optionally annealed between printing steps) to create an even more finely-graded bandgap within the absorber layer 38. Alternatively, fewer films (e.g. double printing) can also be printed to create a less finely-graded bandgap. It is even possible to form the photovoltaic absorber layer 38 from a single photovoltaic nanoparticle coating by a single inkjet applicator 72 and annealed by a single roller and heater unit 76._
[0055] The coating step 54 can occur at room temperature and at atmospheric pressure, or it can be accelerated in various manners, such as but not limited to, through thermal processing, exposure to a laser beam, or heating via IR lamps. Preferably, the processing occurs at a temperature greater than 375°C but less than the melting temperature of the substrate for a period of 1 minute or less. In another embodiment, the atmosphere can be changed to accelerate the processing. The substrate 32 can be at a different temperature during the coating of the raw ink precursor system, so as to enable a variety of substrate materials to be used, such as materials that will either melt or become unstable when the coating material is being deposited.
[0056] In order to overcome the high electrical resistance that arises when the nanoparticles are not interconnected, the nanoparticles can be joined by heating them until their edges melt before the naonparticles can fuse, normally at
V83878WOYVAN_LAW\ 757017\l 15 temperatures of between 300 and 900°C under high pressure from between 5 minutes and 10 hours.
[0057] The aforementioned inkjet application process is a process which achieves precise stoichiometric composition over relatively large substrate areas, which can be difficult using traditional vacuum-based deposition processes. Such precise control can be important in cost-effectively constructing a large- area CI(G)S(S)-based solar cell or module, since the elements of the CI(G)S(S) layer must be within a narrow stoichiometric ratio on nano-, meso-, and macroscopic length scale in all three dimensions in order for the resulting cell or module to be highly efficient.
[0058] After the absorber layer 38 has been applied to the substrate assembly 53, the junction partner layer 40 is applied to the absorber layer 38. The junction layer 40 serves as a junction partner between the photovoltaic absorber layer and the transparent electrode layer 42. The junction partner layer 40 may include inorganic materials such as cadmium sulfide (CdS), zinc sulfide (ZnS), zinc hydroxide, zinc selenide (ZnSe), n-type organic materials, or some combination of two or more of these or similar materials, or organic materials such as n-type polymers and/or small molecules. Layers of these materials may be deposited by chemical bath deposition (CBD) or chemical surface deposition, to a thickness ranging from about 2 nm to about 1000 nm, more preferably from about 5 nm to about 500 nm, and preferably from about 10 nm to about 300nm.
[0059] After the junction partner layer 40 has been applied to the absorber layer 38, the transparent electrode layer 42 is applied to the junction partner layer 40, to form a multi-layered structure herein referred to as a "compound film" 80. The transparent electrode layer 42 may be inorganic, e.g., a transparent conductive oxide (TCO) such as indium tin oxide (ITO), fluorinated indium tin oxide, zinc oxide (ZnO) or aluminum doped zinc oxide which can be deposited using any of a variety of means including sputtering, evaporation, chemical vapor deposition (CVD).
V83878WO\VAN_LAW\ 757017M 16 [0060] Referring now to step 56 in Figure 6 and Figure 9 generally, the compound film 80 is combined with a encapsulant 82 used as a skin for the artificial foliage, thereby completing the solar collector leaf 22. The encapsulant 82 in this embodiment is made of a copolymer EVA and serves to protect and weather seal the compound film 80. Alternatively, the encapsulant 82 can be made of a thermoplastic polymer PVB or a silicon polymer which are inherently stable to ultraviolet light and do not break down over time. Figure 9 shows the encapsulant sheet 82 or the "skin" that is being combined or laminated with the compound film 80 to form the solar collector leaf 22. A roller 84 applies pressure onto skin 82 and the compound film 80 during the lamination process.
[0061] Optionally, the solar collecting leaf 22 can be made more life-like by joining two layers of plastic together under pressure at a predetermined temperature before coating the outer layer with the nanoparticle film. Encapsulant sheets can come in various colors and such a colored sheet can serve as an optional back-skin that is also made of the same material of the front skin 82 to make the leaf appear more lifelike. For example, one layer (first layer) can be dyed with a color resembling that of a natural tree, and the other layer (second layer) can be formed using a lighter green color (to mimic a natural tree leaf having an underside that is less exposed to natural sunlight). The fist layer can also include a grain resembling the texture and feel of a natural tree leaf. The grain can also provide the leaf additional strength so that it is resistant to deformation. The first and second layers of plastic skin can be stacked together between a molding tool and an ultrasonic shaker which pre-heats the plastic sheet before the molding takes place. Upon completion of the molding process, the product can be cooled by air through a cooling fan.
[0062] Referring to step 58 in Figure 6 and Figure 10 generally, the combined compound film 80 and plastic skin 92 form a broad sheet or ribbon that is stamped or cut into shapes resembling leaves; each of these shapes serve as the solar collector leaves 22 (Figure 10 shows a plurality of broad leaves being formed; however leaves resembling the needle-like evergreen leaves shown in
V83878WO\VAN_LAW\ 757017M 17 Figure 3 can be easily formed by this technique as well). Advantageously, a string of solar collecting leaves 22 can be very easily cut from continuously running sheet of the compound film 80 and plastic skin 92. The conductive wires extending from each electrode 36, 42 can be soldered in place at this step or other means known in the art to electrical couple the electrodes 36, 42 of the leaves to the conductors in the branches 20 can be provided as known to one skilled in the art.
[0063] Optionally, this technique can also be applied to other floras such as plants, flowers, bushes and the like. Also optionally, various plastic pipes and joints can be utilized and modified to make the tree more elegant and lifelike by coating these pipes with a thin layer of foam and then heating it briefly with a blast of flame. These coatings can also help to improve the ruggedness of the underlying pipes and protect them from any damages during shipping. In this embodiment, the technique may involve a greater number of pipes and additional vines for decorative purposes. However, the techniques of attaching the leaves and allowing the current from the artificial leaves can remain the same.
[0064] Further optionally, this stamping / cutting technique can be used to fabricate various shapes, which can be used to form other solar collecting products. For examples, the ribbon / sheet can be cut into thin strips, which can then be woven over a frame to form a solar collecting wicker-type furniture product, such as a chair or a table. Therefore, the aforementioned method can be used to manufacture not just solar energy harvesting artificial trees but also anything which can be fabricated from the compound film + plastic skin ribbon of material. In other words, products which include the manufacture of a component that has a substrate which can withstand the photovoltaic nanoparticle coating process described above can be a suitable candidate for being converted into a solar energy harvesting product.,
[0065] Referring to step 60 in Figure 6 and Figure 11 , a plurality of leaves 22 is assembled together onto the branch 20. As noted above, the end of each leaf 22
V83878WO\VANJ_AW\ 757017\1 18 has an electrical plug 46 which electrically couples to a socket on the branch 22, and the end of each leaf 22 has a key shape which matches a slot shape leaf receptacle in the branch 20, thereby enabling each leaf 22 to be physically and electrically coupled to the branch 20.
[0066] Referring to Step 62 in Figure 6 and Figures 12(a) to (e) generally, the trunk 14 and trunk base 30 are manufactured. In Figures 12(a) and (b), the rough bark on an artificial tree is created by coating the artificial tree surface with a thin layer of plastic foam. Then in Figure 12(c), the foam is exposed to a blast of concentrated heat sufficient to collapse part of the foam structure. This partially collapsed foam structure is than coated, either sprayed or painted with a brush (Figure 12(d) and 12(e) respectively), with a colored paint, such as a brown paint to simulate the color of the tree bark, and used to complete the product (Figure 12(e)). A wide range of plastic foams are usable herein such as thermoplastic foams, thermosetting foams and mixtures thereof. Thermosetting foams are generally preferred because once they become set after partial collapsing with the blast of concentrated heat, they are rather impervious to further deformation notwithstanding later heat from a warm office or home environment. Thermoplastic foams have a tendency to further deform with heat which makes them poor candidates albeit still somewhat useful in certain instance. One of the best foams useful herein is polyurethane foam which is a thermosetting foam product of a polyester resin and an isocyanate such as toluene diisocyanate or an amide such azodicarbonamide.
[0067] The products of this process are rendered non-flammable to comply with various state and federal fire codes. As such the foaming formulation consist of at least one fire-retardant compound such as antimony trioxide, stannous oxide, aluminum oxide trihydrate, and zinc borate. These materials, when used in appropriate quantities to render the assembly of parts non-flammable, do not degrade the foam formulation.
V83878WO\VAN_LAW\ 757017M 19 [0068] Figure 12(a) shows a plurality of tubing to be wrapped about a rigid tube, usually by hand. The flexible plastic tubing simulates vines and branches growing up and about the Ficus tree central trunk. The plurality of flexible plastic tubing may be comprised of tubing of many different nominal diameters, from very small or thin to a thickness approaching one-third to one-half the nominal diameter of central Ficus tree trunk-pipe. The wrapping is usually done by hand and the flexible tubes are usually tied tightly to the trunk tube at both distal ends thereof, and then one end of the tree trunk acts as the bottom of the tree and the other end represents the top of the tree.
[0069] The exterior surfaces of an assembly shown in Figure 12(b), comprising rigid pipe and interwoven flexible tubing, is then coated by a nozzle with a liquid foaming mixture that coats all of the surface area of assembly and thereafter generates a thin film of foam.
[0070] The step of exposing the foam to a blast of concentrated heat shown in Figure 12(c) to collapse part of the foam structure is done by exposing the foam to a continuous blast of flame-generated heat that is passed back and forth across the foam. This can be accomplished by having a person sweep a flame of burning propane or natural gas across the foam much the same as a painter would do with a brush.
[0071] The assembly is then painted. FIG. 12(d) shows the assembly laid on a table and the operator applying colored paint to simulate the brown color of the bark. It has been found that applying the paint with a paint brush creates areas of light color and areas of deep color to be developed in the surface further adding to the texture simulating real bark. FIG. 12(e) shows assembly fully built, coated with foam, the foam textured and the paint applied and dried.
[0072] Optionally, the lower end of the trunk 14 can be coupled to a rotating base stand 30 to allow the tree 10, 12 to freely rotate both in a clockwise and counterclockwise direction at a desired speed using an electrical motor (not shown) coupled thereto. The motor can cause the tree to rotate about its
V83878WO\VAN_LAW\ 757017M 20 longitudinal axis to thereby capture more sun rays by exposing more of the solar collecting leaves 22 to sunlight. The rotating base 30 can rotate in a single direction only (either clockwise or counterclockwise) or it can rotate in both the clockwise and counterclockwise directions. Rotating bases are generally well known in the industry, and thus they will not be described in more detail herein.
[0073] Contacts are available to direct the current collected from the solar collecting leaves 22, either fed directly into an inverter (not shown) for "grid tied" or "off grid" applications - or collected using a storage device such as a battery or an ultra capacitor. Users can vary the speed and direction of the rotating base 30 to increase the solar energy collected and track it using a user friendly GUI or digital dashboard (not shown) communicatively coupled to the tree. The GUI can also be helpful to diagnose and detect any fault or incident in the system. Alternatively, users can also track the solar energy harvesting tree output in real time through the internet when connected to a suitable smartgrid platform (such as describe above).
[0074] Referring now to step 64 in Figure 6, the branches 20 are attached physically and electrically to the trunk 14 in the manner noted above. The lower end of the trunk 14 can be optionally inserted in a stand 30 for providing vertical stability. The stand 30 can be rotatable.
[0075] The solar energy harvesting tree 10, 12 allows for modular construction and compact packaging by manufacturers for ease of shipment, storage, and consumer marketing. It is easy to install, disassemble and store by the end user. But for those who do not wish to disassemble, limbs and branches are formed with cutson their underneath sides to permit upward and inward folding of the limbs and branches about the trunk to form a compact storage arrangement.
[0076] In an alternative embodiment, the branches 20 are not hollow, but instead are solid with the conductors molded inside.
[0077] In an alternative embodiment to manufacturing an artificial trunk and branches in the manner described above, a solar energy harvesting tree can be
V83878WO\VAN_LAW\ 757017\! 21 manufactured by manufacturing the solar collector leaves 22 in the manner described, and attaching such leaves 22 to an existing artificial tree having electrical wiring, such as an artificial Christmas tree with integrated LED lighting. In such a Christmas tree, some or all of the leaves are embedded with LED lights, which are electrically coupled to electrical conductors in the branch and trunk of the Christmas tree; such a Christmas tree, for example can be modified into a solar energy harvesting tree by replacing the LED equipped leaves with the solar collector leaves 22. The electrical circuitry of such an artificial Christmas tree can be modified to transmit electricity collected by the solar collecting leaves 22 and out of the tree, instead of transmitting electricity to LED lights integrated into branches of the Christmas tree. More particularly, instead of the sets of LED lights that are connected in parallel across a set of limb and branch wires, these LED lights are replaced by the solar connecting leaves 22. One of these wires is connected in series with one of the wires of an adjacent set of parallel wires connecting the solar leaves 22 in parallel. The other of this second set of parallel wires is connected in series with one of wires of another adjacent set of parallel wires connecting the solar leaves 22 in parallel. Typically twelve sets of parallel circuits each connecting forty solar leaves in parallel would be incorporated in this artificial solar tree, with the other wires of the first set of parallel wires and the twelfth set of parallel wires being connected across an inexpensive power conditioner in a control box . Such a power conditioner may be adjusted to vary the voltage level. In manufacturing, the improved tree of this invention would be constructed in parts, and the parts packaged in a compact container. An end user can open the package, place the rotating stand 30 on the floor, secure the control box to the stand, and place the lower end of the trunk 14 in the control box, thereby also establishing electrical connection between the trunk wires and the power conditioner. The various limbs 20 would be attached to the tree by inserting their wiring terminal plugs in the receptacles of the trunk 14, thereby also establishing electrical connections for the lights on the limb's branches . Finally, the upper portion of the tree would be put in place physically and electrically by connecting the lower end of the trunk portion with the upper end of
V83878WO\VAN_LAW\ 757017U 22 the trunk 14. All of the solar collecting leaves 22 could now be connected in groups between the wires of various sets of parallel wires, which wires are each connected in series with a wire of a different electrically adjacent set of parallel wires or one of the contacts of the power conditioner, through the trunk wires . If the cord and plug are now inserted into an device or mains, and the power conditioner will feed the power into the mains.
Operation
[0078] In operation, the solar collector leaves 22 of the solar energy harvesting tree 10, 12 captures sunlight, as shown in step 82 of the flow diagram 80 of Figure 7. At step 84, the different layers of the leaf's substrate assembly create a potential difference. At step 86, the electrons flow towards the electrodes 36, 42 embedded in each leaf 22. The current flows at step 88 from the electrodes 36, 42 in each leaf 22, through the conductor wires and plug 46 into the branches 20 and trunk 14 of the artificial tree 10. 12. At step 90, the electrons are captured by a battery storage unit. At step 92 and as shown generally in Figure 5, the battery storage unit stores the charge and releases the power back to the owner or to the grid through a power conditioning unit or system. The power conditioning system can include a plurality of power conditioning devices having technology and hardware which are well known in the art. The power conditioning device can optionally include electrical relaying, fault isolation protection, voltage regulation equipment, and metering. This power conditioning system can also include a safety and security system that provides a plurality of fail-safe features (such as sensors coupled to switches) that detects a failure in the system and effectively shuts down the distributed generator or a portion thereof in an emergency situation. A failure in the system can occur when current flows in the opposite direction where the reach of the relay is shortened, thereby leaving high impedance faults undetected. For example, when a utility breaker is opened, a portion of the utility system remains energized even though it may be isolated from the remainder of the utility system. Such energized system can cause injuries to the users, utility personnel, and the system operator. The safety and
V83878WO\VAN_LAW\ 757017M 23 security system thus would detect this failure and shut down the appropriate portion of the system.
[0079] In this embodiment, a docking station (not shown) can serve as a conduit to an urban energy farm whereby the solar energy harvesting tree 10, 12 can offer new sources of income. The harvested energy generated from the solar energy harvesting trees 10, 12 can be stored, bidded and sold to various interested parties through the docking system and managed and sold through a web 2.0 meta-exchange centre. As such, owners of these solar energy harvesting trees 10, 12 can subscribe to various levels of microfarming options - and at the very basic tier, it can be provided to them as a freebie or a low cost if they agree on a longer term fixed subscription plan. In an alternative embodiment, owners of solar trees can take on a long term farming contract with a power grid at a fixed futures price. A digital dashboard and power monitoring system includes a programmable microcontroller to manage power consumption and storage in the distributed power grid. An exemplary and suitable digital dashboard and power monitoring system is described in U.S. Patent Application Serial No. 12/618,697 (commonly owned by the assignee of the present application), which is hereby incorporated by reference. Preferably, measurements are received from a plurality of geographically distributed energy management controllers coupled to the renewable energy devices, and these measurements are processed and displayed on a graphical user interface (e.g., a demand response dashboard), such as on the user communication device (or black box). The digital dashboard and power monitoring software system gives commands to either discharge (or conversely charge) each renewable energy device's stored energy into the power grid in accordance with user defined rules and requirements (such as economics, during routine backups, load balancing, load shedding, and limits). Preferably, the power delivery and demand response dashboard (i.e., graphical interface) is available online (i.e., accessible via the communications network) to each user and system operator for decision-making and for diagnosis and detection of any fault or incident in the system. The digital dashboard and power monitoring system provides inputs to the intelligent
V83878WO\VAN_LAW\ 757017\1 24 management system through communicating with a plurality of building automation and metering systems to collect, archive, analyze and communicate energy information and storing this in a database. By aggregating the management of building-level energy consumption and production, the graphical user interface can also display information to (or educate) building managers on energy use and demand charges.
[0080] While the invention has been shown and described in preferred forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein. These and other changes can be made without departing from the spirit and scope of the invention as set forth in the following claims.
V83878WO\VAN_LAW\ 757017M 25

Claims

Claims What is claimed is:
1. A method for manufacturing a product for harvesting solar energy and for at least one other function, comprising:
(a) forming a solar collector by: selecting a component of the product to serve as a base substrate, the selected component being suitable to withstand a photovoltaic nanoparticle coating application step; coupling an electrically conductive base electrode layer to the base substrate; applying at least one coating of photovoltaic nanoparticles onto the base electrode layer to form a photovoltaic absorber layer; coupling a junction partner layer to the photovoltaic absorber layer; and coupling an electrically conductive transparent electrode layer to the junction partner layer; such that the photovoltaic absorber layer is in electrical communication with the base electrode layer and transparent electrode layer; and
(b) combining the solar collector with other components of the product so that the product performs the at least one other function and harvests solar energy.
V83878WO\VAN_LAW\ 7570I 7M 26
2. A method as claimed in claim 1 wherein the step of applying at least one coating of photovoltaic nanoparticles comprises preparing an ink comprising the photovoltaic particles, and applying the ink onto the base electrode layer by an inkjet printing process.
3. A method as claimed in claim 2 wherein the inkjet printing process comprises applying an ink sub-layer onto the base electrode layer, then annealing the ink sub-layer.
4. A method as claimed in claim 3 wherein the inkjet printing process comprises applying and annealing multiple ink sub-layers onto the base electrode layer.
5. A method as claimed in claim 1 wherein the step of applying at least one coating of photovoltaic nanoparticles comprises spray coating the photovoltaic particles onto the base electrode layer.
6. A method as claimed in claim 5 wherein the photovoltaic nanoparticles are selected from a group consisting of Group IB, IIIA, IV, and VIA semiconductor thin film materials.
7. A method as claimed in claim 1 wherein the photovoltaic nanoparticles are copper-indium-gallium-sulfo-di-selenide ("CI(G)S(S)").
8. A method as claimed in claim 1 wherein the photovoltaic nanoparticles are silicon nano-crystals and the step of applying at least one coating of photovoltaic nanoparticles comprises chemical vapour depositing the silicon nano-crystals onto the base electrode layer.
9. A method as claimed in claim 1 further comprising the step of applying an adhesive layer on the base substrate before the base electrode layer is coupled to the base substrate.
V83878WO\VAN_LAW\ 757017M 27
10. A method as claimed in claim 1 wherein the product is artificial vegetation selected from the group consisting of artificial trees, artificial grass, artificial flowers, and artificial shrubbery and the other function is to provide an aesthetic substitute for natural vegetation.
11. A method as claimed in claim 1 wherein the artificial vegetation is an artificial tree and the selected component serving as a base electrode layer is an artificial leaf, and the other components include an artificial trunk and at least one artificial branch.
12. A method as claimed in claim 11 wherein the base substrate, base electrode layer, photovoltaic absorber layer, junction partner layer, and transparent electrode layer together form a compound film sheet, and the method further comprises after the compound film sheet is formed: cutting leaf shapes from the compound film sheet.
13. A method as claimed in claim 1 wherein the product is wicker furniture and the other function is to furnish a habitat, and wherein the base substrate is wicker material, and wherein the wicker material, base electrode layer, photovoltaic absorber layer, junction partner layer, and transparent electrode layer together form a compound film sheet, and the method further comprises after the compound film sheet is formed: cutting strips from the compound film sheet and forming wicker furniture from the strips.
14. A product for harvesting solar energy and for at least one other function comprising:
(a) at least one solar collector comprising:
a component of the product serving as the base substrate and being suitable to withstand a photovoltaic nanoparticle coating application step;
an electrically conductive base electrode layer coupled to the base substrate;
V83878WO\VAN_LAW\ 757017U 28 a photovoltaic absorber layer coupled to the base electrode layer comprising at least one coating of photovoltaic nanoparticles;
a junction partner layer coupled to the photovoltaic absorber layer; and
an electrically conductive transparent electrode layer coupled to the junction partner layer;
wherein the absorber layer is in electrical communication with the base electrode layer and the transparent electrode layer; and
(b) at least one other component that when combined with the solar collector forms the product and enables the performance of the at least one other function and harvests solar energy.
15. An artificial vegetation product for harvesting solar energy comprising:
(a) an artificial limb;
(b) at least one leaf-shaped solar collector attachable to the artificial limb, and comprising:
a base substrate;
an electrically conductive base electrode layer coupled to the base substrate;
a photovoltaic absorber layer coupled to the base electrode layer comprising at least one coating of photovoltaic nanoparticles;
a junction partner layer coupled to the photovoltaic absorber layer; and
an electrically conductive transparent electrode layer coupled to the junction partner layer;
wherein the absorber layer is in electrical communication with the base electrode layer and the transparent electrode layer.
16. A product as claimed in claim 15 wherein the vegetation is a tree and the artificial limb comprises a trunk and at least one branch attached to the trunk, and wherein the leaf shaped solar collector is attached to the branch.
V83878WO\VAN_LAW\ 757017\1 29
17. A product as claimed in claim 16 wherein the trunk and branch are electrically conductive and the leaf shaped solar collector is physically and electrically connected to the branch, and the branch is physically and electrically connected to the trunk.
18. A product as claimed in claim 17 wherein the base substrate, base electrode layer, photovoltaic absorber layer, junction partner layer, and transparent electrode layer together form a compound film, and the leaf shaped solar collector further comprises an encapsulant covering at least part of the compound film.
19. A product as claimed in claim 18 wherein the encapsulant comprises a coloured backskin sheet joined with the base substrate.
20. A product as claimed in claim 15 wherein the photovoltaic absorber layer comprises at least one inkjet coating of photovoltaic nanoparticles.
21. A product as claimed in claim 20 wherein the photovoltaic absorber layer comprises multiple coatings of photovoltaic nanoparticles.
22. A product as claimed in claim 15 wherein the photovoltaic nanoparticles are selected from a group consisting of Group IB, IIIA, IV, and VIA semiconductor thin film materials.
23. A method as claimed in claim 15 wherein the photovoltaic nanoparticles are copper-indium-gallium-sulfo-di-selenide ("CI(G)S(S)").
24. A method as claimed in claim 15 wherein the photovoltaic nanoparticles are silicon nano-crystals.
V83878WO\VAN_LAW\ 757017\l 30
PCT/CA2011/000266 2010-03-12 2011-03-11 Photovoltaic nanoparticle-coated product and method of manufacturing same WO2011109904A1 (en)

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