WO2009117083A2 - Dispositif photovoltaïque et procédé - Google Patents
Dispositif photovoltaïque et procédé Download PDFInfo
- Publication number
- WO2009117083A2 WO2009117083A2 PCT/US2009/001664 US2009001664W WO2009117083A2 WO 2009117083 A2 WO2009117083 A2 WO 2009117083A2 US 2009001664 W US2009001664 W US 2009001664W WO 2009117083 A2 WO2009117083 A2 WO 2009117083A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- coating
- gas
- layer
- thin
- silicon
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 123
- 239000007789 gas Substances 0.000 claims abstract description 108
- 239000000758 substrate Substances 0.000 claims abstract description 79
- 230000008569 process Effects 0.000 claims abstract description 77
- 239000010409 thin film Substances 0.000 claims abstract description 66
- 238000004544 sputter deposition Methods 0.000 claims abstract description 43
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 33
- 239000001257 hydrogen Substances 0.000 claims abstract description 33
- 238000009501 film coating Methods 0.000 claims abstract description 32
- 229910021423 nanocrystalline silicon Inorganic materials 0.000 claims abstract description 32
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 28
- 229910021417 amorphous silicon Inorganic materials 0.000 claims abstract description 27
- 239000000203 mixture Substances 0.000 claims abstract description 26
- 238000004519 manufacturing process Methods 0.000 claims abstract description 22
- 229910000077 silane Inorganic materials 0.000 claims abstract description 20
- 238000009826 distribution Methods 0.000 claims abstract description 11
- 229910021424 microcrystalline silicon Inorganic materials 0.000 claims abstract description 11
- 239000011159 matrix material Substances 0.000 claims abstract description 9
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical group [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 109
- 238000000576 coating method Methods 0.000 claims description 70
- 239000011248 coating agent Substances 0.000 claims description 61
- 239000011521 glass Substances 0.000 claims description 58
- 239000011787 zinc oxide Substances 0.000 claims description 56
- 229910052710 silicon Inorganic materials 0.000 claims description 38
- 239000010703 silicon Substances 0.000 claims description 38
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 37
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 30
- 238000005530 etching Methods 0.000 claims description 27
- 239000000463 material Substances 0.000 claims description 24
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 19
- 229910052782 aluminium Inorganic materials 0.000 claims description 19
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 19
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 15
- 229910052786 argon Inorganic materials 0.000 claims description 15
- 230000005670 electromagnetic radiation Effects 0.000 claims description 15
- 229910052751 metal Inorganic materials 0.000 claims description 13
- 239000002184 metal Substances 0.000 claims description 13
- 229910044991 metal oxide Inorganic materials 0.000 claims description 13
- 238000006243 chemical reaction Methods 0.000 claims description 9
- 239000002253 acid Substances 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 150000002431 hydrogen Chemical class 0.000 claims description 6
- 150000002500 ions Chemical class 0.000 claims description 6
- 230000004044 response Effects 0.000 claims description 6
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 6
- 229910001887 tin oxide Inorganic materials 0.000 claims description 6
- 239000002019 doping agent Substances 0.000 claims description 5
- 238000001552 radio frequency sputter deposition Methods 0.000 claims description 5
- 239000012298 atmosphere Substances 0.000 claims description 4
- 230000007423 decrease Effects 0.000 claims description 4
- 238000000151 deposition Methods 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 4
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 3
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims description 3
- 229910052796 boron Inorganic materials 0.000 claims description 3
- 239000000835 fiber Substances 0.000 claims description 3
- 229910052733 gallium Inorganic materials 0.000 claims description 3
- 229910052738 indium Inorganic materials 0.000 claims description 3
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims description 3
- 239000004065 semiconductor Substances 0.000 claims description 3
- 239000005361 soda-lime glass Substances 0.000 claims description 3
- 239000006117 anti-reflective coating Substances 0.000 claims description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 239000012799 electrically-conductive coating Substances 0.000 claims 6
- 238000009472 formulation Methods 0.000 claims 6
- 150000004706 metal oxides Chemical class 0.000 claims 6
- 230000015572 biosynthetic process Effects 0.000 claims 3
- 238000007740 vapor deposition Methods 0.000 claims 2
- 230000003667 anti-reflective effect Effects 0.000 claims 1
- 239000004020 conductor Substances 0.000 claims 1
- 230000008021 deposition Effects 0.000 claims 1
- 229910052814 silicon oxide Inorganic materials 0.000 claims 1
- 239000007787 solid Substances 0.000 claims 1
- 238000005477 sputtering target Methods 0.000 claims 1
- 238000005229 chemical vapour deposition Methods 0.000 abstract description 15
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 abstract 1
- 210000004027 cell Anatomy 0.000 description 35
- 239000002707 nanocrystalline material Substances 0.000 description 16
- 230000008901 benefit Effects 0.000 description 11
- 230000005540 biological transmission Effects 0.000 description 11
- 239000002131 composite material Substances 0.000 description 9
- 210000002381 plasma Anatomy 0.000 description 9
- 235000012239 silicon dioxide Nutrition 0.000 description 7
- 239000000377 silicon dioxide Substances 0.000 description 7
- 239000013078 crystal Substances 0.000 description 6
- 230000006872 improvement Effects 0.000 description 5
- 239000013081 microcrystal Substances 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 230000015556 catabolic process Effects 0.000 description 4
- 230000008859 change Effects 0.000 description 4
- 238000006731 degradation reaction Methods 0.000 description 4
- XYFCBTPGUUZFHI-UHFFFAOYSA-N Phosphine Chemical compound P XYFCBTPGUUZFHI-UHFFFAOYSA-N 0.000 description 3
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 3
- 230000002411 adverse Effects 0.000 description 3
- 230000004888 barrier function Effects 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 239000002159 nanocrystal Substances 0.000 description 3
- 230000006798 recombination Effects 0.000 description 3
- 238000005215 recombination Methods 0.000 description 3
- 229910052725 zinc Inorganic materials 0.000 description 3
- 239000011701 zinc Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000004566 IR spectroscopy Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 229920002313 fluoropolymer Polymers 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 230000001788 irregular Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000003595 spectral effect Effects 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- YZCKVEUIGOORGS-UHFFFAOYSA-N Hydrogen atom Chemical compound [H] YZCKVEUIGOORGS-UHFFFAOYSA-N 0.000 description 1
- 238000006124 Pilkington process Methods 0.000 description 1
- 238000001069 Raman spectroscopy Methods 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 238000000149 argon plasma sintering Methods 0.000 description 1
- 238000010420 art technique Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000002800 charge carrier Substances 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000003467 diminishing effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
- 238000010218 electron microscopic analysis Methods 0.000 description 1
- 239000004811 fluoropolymer Substances 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 238000010849 ion bombardment Methods 0.000 description 1
- 238000001755 magnetron sputter deposition Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000013080 microcrystalline material Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 229910000073 phosphorus hydride Inorganic materials 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- WXRGABKACDFXMG-UHFFFAOYSA-N trimethylborane Chemical compound CB(C)C WXRGABKACDFXMG-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022466—Electrodes made of transparent conductive layers, e.g. TCO, ITO layers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022466—Electrodes made of transparent conductive layers, e.g. TCO, ITO layers
- H01L31/022483—Electrodes made of transparent conductive layers, e.g. TCO, ITO layers composed of zinc oxide [ZnO]
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—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
- H01L31/0368—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 polycrystalline semiconductors
- H01L31/03682—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 polycrystalline semiconductors including only elements of Group IV of the Periodic Table
- H01L31/03685—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 polycrystalline semiconductors including only elements of Group IV of the Periodic Table including microcrystalline silicon, uc-Si
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—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
- H01L31/0384—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 other non-monocrystalline materials, e.g. semiconductor particles embedded in an insulating material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—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
- H01L31/03921—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 including 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
- Y02E10/545—Microcrystalline 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
- 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
- Y02E10/548—Amorphous silicon PV cells
Definitions
- This invention relates to photovoltaic devices and methods of making them. More particularly, this invention relates to thin-film polycrystalline photovoltaic devices and methods. More particularly, this invention relates to transparent conductive layers in thin-film photovoltaic devices, and to methods of making such layers. More particularly, this invention relates to methods of making thin-film nanocrystalline photovoltaic devices. More particularly, this invention relates to chemical vapor deposition reactors and methods of using them for making thin-film photovoltaic devices.
- Another object of the invention is to provide photovoltaic devices whose output remains relatively high, even under such adverse conditions.
- a further problem which has adversely affected the manufacturing cost of prior devices is the relatively slow speed at which the devices can be manufactured.
- amorphous silicon is a relatively low cost material, it has certain shortcomings.
- Other thin-film devices also have shortcomings. It is an object of the present invention to provide a photovoltaic device in which as many of those shortcomings are eliminated as possible.
- amorphous thin-film devices suffer severely from lack of stability. In particular, the energy conversion efficiency of such devices decreases markedly starting shortly after its first use in intense light. The efficiency continues to decrease with use until, after a time, the efficiency stabilizes at a much lower level than it had when it was first manufactured.
- amorphous silicon photovoltaic devices Another problem with amorphous silicon photovoltaic devices is that their spectral response is relatively poor. That is, the amount of current output in response to components of sunlight of longer wavelengths is much lower than to those having shorter wavelengths, with the result that substantially less than the full spectral range of available solar energy is used to produce electrical power.
- TCO transparent conductive
- the transparent conductive layer often consists of doped tin oxide which is applied to the surface of the glass support member.
- Doped tin oxide has certain disadvantages, including relatively high cost, due to its tin content, and has been replaced, in many cases, by doped zinc oxide.
- the surface of the tin oxide or the zinc oxide usually is etched in order to roughen the surface of the coating and perform "light-trapping".
- microcrystalline silicon with a predominance of microcrystals in the silicon.
- Another proposal has been to produce nanocrystalline silicon devices.
- commercially successful devices of either type have not yet been developed.
- One problem has been that the process of making microcrystalline or nanocrystalline materials in the past has been exceedingly slow and expensive.
- a suitable composite structure incorporating nanocrystalline silicon has not previously been known. [0024] Therefore, it is a further object of the present invention to provide a relatively high-speed manufacturing method for manufacturing nanocrystalline devices.
- a new nanocrystalline photovoltaic device in which the active layer has an effective amount of nanocrystalline silicon which is embedded in a matrix of silicon having another form.
- the matrix consists of amorphous silicon or a combination of amorphous and microcrystalline silicon.
- the nanocrystalline thin-film layer is the only active layer in the device.
- the nanocrystalline layer is used in tandem with a layer of amorphous silicon to form a composite photovoltaic device with improved characteristics .
- TCO layer Transparent Conducting Light-Trapping Oxide
- This layer consists of two components; a first, relatively thick layer of a metallic oxide, such as zinc oxide in its pure form, and a preferably much thinner doped metallic oxide layer on top of it, such as zinc oxide doped with a small percentage of a metal such as aluminum.
- the thin doped oxide serves as an electrically conducting layer, and the pure zinc oxide serves as an improved light-trapping layer which is more transmissive to light in the long wavelengths than doped zinc oxide .
- the TCLO layer also can be used to separate the nanocrystalline and amorphous layers in the tandem device described above.
- the nanocrystalline layer can be formed by several different methods. However, a preferred method is a chemical vapor deposition ("CVD") method in which a substantial number of glass panels can be processed in a single reactor simultaneously .
- CVD chemical vapor deposition
- the silane and hydrogen mixture used as the process gas is significantly altered by greatly increasing the hydrogen content relative to the silane content.
- a plasma is used to enhance the process. The plasma is developed by radio frequency (“RF”) electrical energy, and the concentration of energy per unit area of the panels being coated is increased greatly over the maximum levels used in the past. Other process variables also are increased substantially.
- RF radio frequency
- the process gas is delivered to the surfaces of the multiple panels in the reactor evenly and rapidly by the use of a manifold distributing gas to a plurality of hollow, conduits, each with multiple evenly-spaced fine holes in the sides so as to deliver the gas to the panel surfaces in small jets at many locations distributed over the surface of the panels ..
- the result of the method is a significant increase in speed in the process of forming the nanocrystalline material, and a corresponding reduction of manufacturing cost.
- the result of the various features of the invention is the production of an improved high-performance, low cost photovoltaic module which promises to significantly lower the cost of converting light into electrical power.
- FIGURE 1 is a front perspective view of a photovoltaic panel or module constructed in accordance with the present invention.
- FIGURE 2 is a rear perspective view of the panel shown in FIGURE 1;
- FIGURE 3 is an enlarged, partially schematic cross sectional view of one embodiment of a thin-film photovoltaic cell constructed in accordance with the invention;
- FIGURE 4 is a view like that in FIGURE 3 of another embodiment of a photovoltaic cell constructed in accordance with the invention.
- FIGURES 5 and 6 are graphs illustrating features of the photovoltaic devices of the invention.
- FIGURES 7A and 7B are cross-sectional, enlarged schematic views illustrating the crystalline structure of a portion of the active thin-film layer of a photovoltaic cell consisting primarily of microcrystalline silicon (FIGURE. 7A) and nanocrystalline silicon (FIGURE 7B) ;
- FIGURE 8 is a photomicrograph of a cross section cut through a layer of nanocrystalline material made in accordance with the present invention.
- FIGURE 9 is a photomicrograph, similar to that in FIGURE 8, of the nanocrystalline material shown there, but at a lower magnification;
- FIGURE 10 is a perspective, partially schematic view of a chemical vapor deposition reactor constructed in accordance with the present invention.
- FIGURE 11 is an enlarged end elevation view, partially schematic, of a portion of the structure shown in FIGURE 10;
- FIGURE 12 is a view similar to that in FIGURE 11 of a prior art reactor construction which also can be used in performing the process of the present invention;
- FIGURE 13 is an enlarged, schematic cross-sectional view of a conductively-coated glass panel which is useful as a building block for thin-firm photovoltaic devices, including those described elsewhere herein; and [0050]
- FIGURE 14 is a graph showing a comparison of characteristic features of various layers of the device shown in FIGURE 13.
- FIGURE 1 is a front perspective view of a photovoltaic panel or module constructed in accordance with the present invention.
- the panel 30 is of a standard size, approximately 26 inches in width and 55 inches in length (.666 meter by 1.40 meters) which is useful for mounting on rooftops, surfacing the sides of buildings, positioning in fields as the active elements in solar energy farms, and the like.
- Each panel 30 has a front glass plate 32, and a rear glass plate 34 (see figure 2) secured to it. Each glass plate has a border area 36 which can fit into a frame for use in mounting the panel.
- the rear glass plate 34 serves the purpose of protecting the metalized rear surface of the front glass plate 32, and adds structural strength to the panel.
- the panel has a pair of electrical leads 38 and 40 for use in connecting the panel 32 to other panels, or to equipment such as DC-to-AC converters, storage batteries, or other utilization devices.
- the panel 30 includes a thin-film photovoltaic structure formed on the inner surface of the front glass plate 32. That thin-film structure is separated by the well known process of "scribing", into 50 parallel interconnected strips 42.
- each strip when in full, direct sunlight, produces approximately 600 milivolts, the total voltage produced by the panel is approximately 30 volts.
- the voltage output will depend on the number of cells connected together, and the type of cells used.
- One contact of the edge side of the series-connected strips is connected electrically by an aluminum foil strip 44 to a junction box 48, and another aluminum strip 46 connects the opposite edge of the cells to the same junction box. Those contacts are connected in the junction box to the electrical leads 38 and 40.
- the electrical current output from the panel 30 when in full, direct sunlight will depend on the type of cells used, as well as the total surface area of the panel.
- the panel 30 typically will produce more than 100 watts of electrical power in direct sunlight.
- the panel 30 is black in color. However, the panel can be given colors other than black by use of techniques well known in the art.
- the panel 30 can be made so that it transmits no light through the panel, or it can be made to transmit a portion of the light it receives so as to allow some light into the interior of a building in which it might be used as an outside window or decorative panel.
- FIGURE 3 is a greatly enlarged, broken-away schematic cross sectional view of a thin-film photovoltaic cell 50 constructed in accordance with the present invention.
- the cell 50 shown in FIGURE 3 consists of a glass substrate 52 designed to receive light in the direction indicated by the arrows 56 and transmit it to the thin-film layers on the upper surface of the glass substrate, where it is converted to electrical energy.
- the bottom surface of the glass plate 52 usually is smooth, as it would come from a manufacturing facility using the float glass process.
- the glass can be ordinary soda-lime glass, but preferably is low-iron- content glass, both of which are readily available and of moderate cost.
- the upper surface 59 of the glass be "textured", as by etching, so as to maximize the amount of light retained within the cell and used to generate electrical energy.
- the bottom or front surface 53 of the glass has a coating 54 of silicon dioxide (SiO2).
- the front surface 53 of the glass usually is smooth and needs the coating to minimize reflection and maximize the absorption of sunlight into the glass through the front surface.
- FIGURE 3 Various layers of materials deposited on the upper surface of the glass shown in FIGURE 3 are defined by wavy lines.
- the wavy shape of these lines indicates schematically that the surface is roughened, although the recesses in the surface preferably would be so very small that they could not be seen by the naked eye and would not be visible in the drawings.
- the first layer 58 on the upper textured surface of the glass substrate 52 is another layer of silicon dioxide, which, as it is well known, serves as a diffusion barrier.
- TCO Transparent Conductive Oxide
- a composite layer consisting of a first layer of pure or "intrinsic" Zinc Oxide ("iZnO") with an etched upper surface and a substantially thinner layer 62 on top of the Zinc Oxide.
- the layer 62 consists of Zinc Oxide doped with from 1.5% to 5% of a known metallic doping material to make the layer 62 electrically conductive.
- the Zinc Oxide can be doped with aluminum, gallium, indium or boron, as it is well known. However, aluminum is preferred.
- the composite layer consisting of intrinsic Zinc Oxide with conductive Zinc Oxide will be referred to herein as the "TCLO" layer. It is highly advantageous in that it provides the electrically conductive layer needed to form the front contact of the photovoltaic cell, but significantly improves the transmission of light, especially in the longer wavelengths and is significantly more stable than substances such as tin oxide (SbO2), which often loses some of its transmissiveness when subjected to a hydrogen atmosphere used in CVD reactor manufacturing .
- TCLO tin oxide
- the TCLO layer not only improves the transmission of direct light, but it also improves the transmission of diffuse light.
- the use of such a TCLO composite layer is highly advantageous. A cell using it produces a significant increase in the output current density as compared with prior TCO coatings .
- the layer 64 formed on top of the layer 62 is the active layer of the cell, and it utilizes another novel feature of the invention, that is, the layer 64 contains an effective amount of nanocrystalline silicon.
- Layer 64 is shown much thicker than the other layers, simply for the ease of showing its internal structure.
- the lower portion of the layer 64 is p-type nanocrystalline silicon, the upper portion is n-type nanocrystalline silicon, and the intermediate section is "i" or intrinsic (undoped) nanocrystalline silicon.
- FIGURE 7A shows layer 64 schematically as it might look at a high degree of magnification if it were made of microcrystalline silicon. Long, thin microcrystals 94 are embedded in a matrix 96 consisting primarily of amorphous silicon.
- FIGURE 7B shows the same layer 64 if made primarily of nanocrystalline silicon.
- the crystal structures are made of "grains" which have a width similar to the width of the microcrystals, but are considerably shorter in height.
- Silicon "nanocrystals” are defined herein as being individual crystals between one half of a nanometer (0.5 nm) to approximately ten nanometers (10 nm) in width, and from ten to one hundred nanometers (10 nm to 100 nm) in length.
- Microcrystallines are defined as crystals of silicon between around the same width or wider, up to one hundred nanometers (100 nm) and from one hundred to four hundred nanometers (100 nm to 400 nm) in length. [0079] Amorphous silicon is, of course, non-crystalline.
- the matrix in which the nanocrystals are formed is predominantly amorphous, but as noted above, some microcrystals might be present in addition.
- An “effective" amount of nanocrystalline material is at least 30% by weight of the material in the active layer.
- a “predominance” of nanocrystalline material is in excess of 50%. Although there is no upper limit, at amounts above about 70%, further increases may give diminishing returns. Therefore, a preferred range is 30% to 70% nanocrystalline material.
- nanocrystalline material for the active layer 64 of the device 50 is highly advantageous.
- the presence of the nanocrystalline material is believed to significantly improve the quantum efficiency ("QE") of the solar cell.
- QE quantum efficiency
- the nanocrystalline layers can be deposited to form a commercially acceptable device at a substantially faster rate than in prior thin film silicon devices.
- nanocrystalline silicon cells made as described herein offer a significant improvement in efficiency. As it is well-known, the efficiency of amorphous silicon devices becomes degraded with time. This serious defect is substantially eliminated by the present invention.
- the next layer 66 on top of the active layer 64 is another layer of doped zinc oxide which is conductive. It is used as a diffusion barrier and an anti- reflection coating.
- the final coating is a coating of aluminum 68 which serves as the back electrode for the photovoltaic cell.
- FIGURES 5 and 6 show graphs illustrating the improved characteristics of nanocrystalline and microcrystalline silicon devices as compared with amorphous silicon devices.
- the dashed-line curve 80 in FIGURE 5 is a plot showing the Quantum Efficiency ("QE") of typical amorphous cells plotted against the wavelength of the light received.
- QE Quantum Efficiency
- the plot covers the region of the electromagnetic spectrum from four hundred to eleven hundred nanometers (400 nm to 1,100 nm) .
- the nanocrystalline response curve 82 gives a much greater Quantum Efficiency and conversion of light into electrical energy in the area 84 between the curves 80 and 82.
- the QE of curve 82 is over 0.2 while that for curve 80 is near zero. This represents a significant increase in current and voltage output for the crystalline devices over the amorphous device.
- FIGURE 6 shows the percent degradation in electrical output by the nanocrystalline material at 90, and the curve 88 shows the degradation of an amorphous device over time, both under exposure to very intense artificial light equivalent to 55 times the intensity of direct sunlight.
- the amorphous device In actual use in sunlight, the amorphous device usually stabilizes in 30 to 80 days, and then does not deteriorate further during its remaining life.
- the nanocrystalline device of the invention shows little, if any, deterioration.
- microcrystalline silicon exhibits some of the same advantages of nanocrystalline material, the time required to manufacture it is very significantly greater than the time using the novel process of the present patent application to make the nanocrystalline material, as it will be described in greater detail below.
- the nanocrystalline devices will supply a higher voltage output per cell (550 to 600 milivolts, as compared with the prior 400 to 500 milivolts) and a higher current output (e.g., over 20 and up to 26 miliamps per square centimeter of cell surface area compared with less than 20 miliamps previously) .
- FIGURES 8 and 9 are photomicrographs made by a Transmission Electron Microscope of a nanocrystalline silicon layer in cross section.
- FIGURE 9 shows that the crystals are aligned in the direction of the arrow, which is substantially perpendicular to the substrate which is below and to the right.
- FIGURE 8 which is enlarged even more than the photograph of FIGURE 9, shows a portion of the same surface of the material at approximately the atomic level.
- Every black dot in Figure 8 represents an atom.
- a regular line of atoms represents a crystalline lattice. It can be seen in both figures that there are nanocrystalline grains.
- Crystalline domains of the size of several nanometers to a couple of tens of nanometers are seen. They are surrounded by irregular grain boundaries, which are amorphous in nature.
- FIG. 9 shows the nanocrystalline silicon grains grown one over the other. At the bottom of the grains is the glass substrate. Such a structure increases the internal light scattering and absorption of the light inside the thin-film. This feature increases the short circuit current density of the cell.
- the presence and quantities of nanocrystalline silicon in a layer can be detected by known techniques such as Raman spectroscopy, X-ray diffraction analysis, High-Resolution Transmission Electron Microscopic analysis and/or infrared spectroscopy .
- FIGURE 4 shows a tandem photovoltaic device 70 similar to the device 50 shown in FIGURE 3, except that an amorphous silicon layer is formed first on the substrate, and then a nanocrystalline layer is formed on top of the amorphous layer.
- the amorphous silicon layer 72 is formed on the conducting zinc oxide layer 62.
- another TCLO composite layer is formed on top of the amorphous silicon layer.
- the TCLO composite consists of iZnO layer 74 with a doped ZnO (cZno) layer 76 on top.
- the composite layer 74, 76 serves the same purpose as the first TCLO layer.
- the nanocrystalline silicon layer 64 is built on top of the TCLO structure 74, 76.
- the tandem device 70 takes advantage of the different band gaps of the amorphous and nanocrystalline materials to provide higher output voltage and power levels than a nanocrystalline device such as the device 50 shown in FIGURE 3.
- the nanocrystalline layer can produce a voltage of 600 milivolts per cell, and the amorphous layer can produce 900 millivolts.
- the total voltage of the cell is the sum of the individual voltages, or 1.5 volts.
- the current output usually will be somewhat lower, e.g. 16 to 17 per square centimeter versus 20 to 26 ma/cm 2 , but the power output will be significantly greater.
- the tandem device does not suffer from as much conversion efficiency degradation as a solely amorphous silicon device.
- the devices shown in FIGURES 3 and 4 above can be manufactured in at least two different ways; one is by the use of chemical vapor deposition ("CVD") , and the other is by sputtering .
- CVD chemical vapor deposition
- FIG 10 is perspective view of a Chemical Vapor Deposition ("CVD") reactor 100 which can be used to great advantage in manufacturing the photovoltaic devices of the invention .
- the reactor 100 includes insulated side walls 102 and 104, a top wall 106 and a bottom wall 108.
- a rear wall also is provided but is not shown in FIGURE 10 because the rearwardly extending portion of the reactor has been broken away to enhance the visibility of the device in the drawings.
- a hinged door 110 is provided. It is shut tightly when the reactor is in use, and has an air-tight seal to help maintain a very low pressure in the reactor chamber when it is in operation.
- FIGURES 10-12 show two different structural arrangements for delivering gas to the glass substrates to be coated in the reactor.
- FIGURES 10 and 11 show schematically a structure improved by a feature of the invention, and
- FIGURE 12 shows schematically the gas delivery system of a conventional reactor.
- FIGURE 12 is cross-sectional end elevation view showing five pairs such as the pair 132, 134.
- the glass plates are arranged with their front surfaces contacting a very flat aluminum plate 136, 138, 140, 142 or 144, and a lower support angle member 145, and an upper channel member 143.
- the members 145 and 143 preferably, are made of a non-conductive plastic material which will maintain its shape at high temperatures, such as fluropolymers like DuPont "Teflon".
- Each aluminum plate support structure 136, 143, 145 also provides an electrically conductive frame for application of RF signals to the glass plates to form a plasma, as it will be described below.
- process gas is delivered to a manifold 140 which has numerous very small holes in its bottom wall. Process gas is fed, under a slight positive pressure, into the manifold 140 to deliver the gas downwardly through the small holes to form many small gas jets 141.
- the gas flows downwardly towards the vacuum pump 112 and makes contact with the exposed surfaces of the glass plates on the way.
- the glass plates are very closely spaced, typically by a distance of 6 to 32 mm from one another.
- RF radio frequency
- the glass plates upon which the active silicon layer is to be formed preferable already is coated with a silicon dioxide anti-reflective coating on the front surfaces, and a TCO coating on the opposite surface, the one to be coated. These coatings usually are formed by sputtering equipment.
- a RF signal of a suitable frequency such as 13.56 megahertz, or a multiple of that frequency, is generated by the RF generators to develop a plasma in the argon-silane-hydrogen gas mixture. This causes the silane to become dissociated into silicon and hydrogen, the resulting materials having the formula Si+2H2.
- First 3% or so of trimethylboron is used in the gas to make the p layer of silicon, after which the undoped or intrinsic layer of silicon is formed, and then phosphine (PH 3 ) at a rate of about 3% by weight is mixed in with the starting gases to form the layer of n-type silicon.
- the resulting product preferably is sent to a sputtering line to lay down the transparent conductive oxide (TCO) and the metal electrode layer to finish the device.
- TCO transparent conductive oxide
- intermediate scribing steps may be performed at various points in the process in order to form the individual cells 42 (FIGURE 1) and interconnect the cells in series as described above. These steps are well known and will not be described in detail here.
- FIGURE 12 may be used to manufacture the photovoltaic structures of the invention, the preferred reactor is shown in FIGURES 10 and 11.
- FIGURES 10 and 11 interspersed between adjacent pairs of glass plates such as plates 119, 120 supported by the metal plates 115, 113, 111 and 109, and fluoropolymer channels 121, 125, 127, 129, etc and angles 105, are descending hollow gas distribution conduits 118, 122, 126, 130, etc. These conduits are shaped like and are approximately of the same area as the glass plates. Each of the conduits has a plurality of very small holes 142 (FIGURE 10) in both side walls, except for the conduit 118 which has holes in only one side wall, the wall facing the left surface of the glass plate 120.
- a distribution conduit at the opposite end of the reactor has holes in only the surface facing towards the nearest glass plate.
- each of the small holes in the conduit walls produces a tiny jet of gas which is directed toward one of the glass plate surfaces to be coated.
- gas is distributed substantially evenly across the entire surface of each of the glass plates so as to assure fresh gas reaching substantially all areas of each glass plate in approximately equal concentrations. This is believed to allow for the use of a much higher flow rate of gas than otherwise would be possible due to the fact that, without the conduits 118, 122, etc., the gas concentration likely would change materially as the gas flows from the top to the bottom of the reactor.
- the gas is delivered from a manifold 114 through an inlet pipe 116 which can enter the housing through the rear wall, for example, with suitable vacuum-tight seals around the entrance. If the entrance 116 is in the rear wall of the reactor 100, it would be facing away from the paper on which FIGURE 11 appears. However, it is shown entering from the left, for the sake of convenience in the drawings. [00128] By means of such a construction, the entire manifold 114 and all of the distribution conduits 118, 122, etc. can be removed as a unit from the reactor housing by disconnecting the coupling 116 and sliding the unit in metal support tracks 107 through the front opening of the reactor so that the entire unit can be removed and replaced for cleaning.
- the manifold 114 and the other components are all made of a metal which is resistant to corrosion by the gases and plasmas used in the reactor, and can maintain its strength and shape at the temperatures used in the reactor.
- Stainless steel is a desirable material for this purpose, but aluminum also can be used.
- FIGURE 11 As it is shown in FIGURE 11, the electrical connections of the metal frames and the distribution conduits is different from that shown in FIGURE 12.
- a RF generator 131, 133, 138 or 137 is connected to each of the glass frames and the distribution conduits are grounded. It is possible to reverse the connections, with the distribution conduits plates connected to the generators and the glass plates grounded. The object of this is to assure that there is no barrier between a distribution conduit and the glass plate to prevent a plasma from forming between the two to assist in the deposition process.
- a signal supply unit 139 is provided for supplying a negative 3 volt DC bias and a low-frequency modulating signal to each RF source, for purposes to be described below.
- the ratio of the quantity of hydrogen to the quantity of silane in the process gas should be from approximately ten to around five hundred. This is in contrast to prior practices used in making amorphous or microcrystalline silicon where the ratio of hydrogen to silane is believed to be less than ten.
- the power level is to be increased to the range of from approximately one to ten kilowatts per square meter .
- the process gas input flow rate should be increased up to fifty standard liters per minute. This is in contrast to much lower flow rates which are believed to have been used in the past.
- the temperature range should be increased from the usual range of 200 0 C to 400 0 C to a range from less than 200 0 C to 450°C.
- the working pressure should range up to a maximum of approximately of ten torr.
- the vacuum pump is used to evacuate the reactor to a very low pressure of 10 "6 militorr. This clears all of the excess gases from the reactor before the start of the process.
- the working pressure in the reactor should be maintained in the range from 10 torr down to 10 "3 torr.
- the RF signals delivered to the reactor from the RF supplies are modified by supplying from the source 139 a negative three volt DC (-3V DC) bias signal to the input of each generator.
- a negative three volt DC (-3V DC) bias signal to the input of each generator.
- each RF source should be pulsed to turn it off and on at the rate of about one hundred cycles per second or so .
- the negative three volt DC bias for each source is provided in order to slow down ions as they bombard the glass surfaces being coated so as to prevent damage to the coatings from the excess bombardment.
- the pulsing of each of the RF sources at a low rate of around one hundred cycles per second provides gaps in the power delivery which is believed to help the nanocrystals to develop and also helps prevent damage due to constant ion bombardment of the crystalline layers being formed.
- the great increase in the ratio of hydrogen to silane in the process gas mixture is believed to be highly advantageous .
- the manufacturing process is believed to be much faster than the prior processes useful in production processing of photovoltaic cells.
- the highest rate believed to be actually achieved for forming amorphous and microcrystalline silicon to produce acceptable commercial products is around one angstrom per second, it is believed that the present process will produce the nanocrystalline material at the rate up to thirty five angstroms per second.
- the glass substrate has a coating of silicon dioxide anti-reflecting material on the front surface, and a TCLO coating as described above on the opposite surface .
- the plate is placed in the first sputtering chamber on a metal (aluminum or silver) support plate.
- An RF source is attached to the plate and the chamber is evacuated and the substrate is heated.
- the substrate then is moved to a second chamber in which to grow the nanocrystalline silicon layer.
- the target used is pure silicon.
- the sputtering gas in the chamber is hydrogen, argon and, in sequence, polymethylboron or diborane with nitrogen.
- a doped silicon target can be used with a mixture of argon plus hydrogen as the sputtering gas .
- the third and fourth chambers contain a pure silicon target with hydrogen and argon as the sputtering gas to form the intrinsic layer.
- the fifth chamber contains a silicon target with phosphine gas mixed with the hydrogen plus argon sputtering gas or a phosphorus-doped silicon target with hydrogen plus argon.
- the sixth chamber is used to anneal and heat treat the plate up to 250 degrees centigrade.
- FIGURE 13 is a cross-section, broken-away view of a TCLO coated substrate 150 which forms the foundation for thin- film photovoltaic devices like those shown in FIGURES 2 and 3 above .
- the layers of silicon dioxide used in those devices have been omitted from FIGURE 13 for the sake of simplicity in the drawings .
- the TCLO substrate includes a glass substrate member 152, with a layer of pure zinc oxide (iZnO) 154 and a layer of conductive zinc oxide 15b (cZnOrAl) on top.
- iZnO pure zinc oxide
- cZnOrAl conductive zinc oxide 15b
- Substrate 150 preferably with the addition of silicon dioxide layers as shown in FIGURES 2 and 3, forms a distinct product which can be made and supplied to photovoltaic cell manufacturers as a highly desirable building block. It also can be made by such manufacturers as a part of the cell fabrication process .
- the glass substrate 152 preferably is low-iron glass, but may be soda-lime glass, or another material that is transparent to electromagnetic radiation including visible light, and can withstand temperatures up to approximately 450 0 C and has a low reactivity to hydrogen plasma.
- the upper surface 160 of the glass should be roughened, as by etching. The sizes of the resulting surface irregularities ideally would be of the same order of magnitude as the wavelengths of light being transmitted, or as close to that size as is available at a reasonable cost.
- the various layers that are formed on the substrate 152 preferably are formed by a series of sputtering steps in an inline sputtering system consisting of several sputtering chambers in series, akin an assembly line.
- the sputtering process used in any given sputtering chamber may be a DC sputtering process, an rf-sputtering process, a magnetron sputtering process, or any other suitable sputtering process.
- LAYER OF PURE ZINC OXIDE a layer 154 of substantially pure, undoped zinc oxide (ZnO) , known as intrinsic zinc oxide, or i-ZnO, is deposited on the textured upper surface 160 of the glass substrate 152.
- ZnO undoped zinc oxide
- i-ZnO intrinsic zinc oxide
- the sputtering process used is a rf-sputtering process with an overlaid DC bias.
- Substrate 152 is placed in a RF sputtering chamber.
- the substrate 152 is, for example, a glass plate approximately 26 inches wide by 55 inches long, and approximately 3-lOmm thick.
- the chamber is approximately 32 inches wide by 60 inches long by 10 inches tall.
- a target of ZnO of 99.999% or better purity, formed into a rectangular block, is attached to an electrode within the chamber.
- the chamber wall is grounded, whereas the electrode is coupled to an RF generator.
- the chamber then is substantially evacuated.
- An inert gas, preferably argon, is introduced to bring the pressure in the chamber up to approximately 0.01-0.03 millibars.
- the entire chamber is heated to approximately 200 0 C.
- Radio-frequency waves are then generated by the RF generator, and applied to the back surface of the target electrode.
- the radio-frequency waves are of a power density of approximately 300 watts per five inch-square, and preferably of a frequency of 13.56 MHz or integral multiples thereof, though may be selected from a broad spectrum of frequencies.
- the argon gas is converted into a plasma state.
- a DC-bias of approximately negative 3 volts is applied to the electrode. This strongly attracts and accelerates the positively charged argon nuclei.
- the argon nuclei are accelerated towards the electrode, and impact the surface of the ZnO target. This impact knocks loose individual ZnO molecules which are deposited onto the glass plate 152 to form a thin film.
- the iZnO layer 154 grows at approximately 1-5 angstroms per second.
- the desired thickness is 500nm-750nm (5000 angstroms - 7500 angstroms) .
- Layer 154 may be thicker or thinner than this range, as desired.
- the ZnO molecules naturally form hexagonal crystals, perpendicular to the upper surface 160 of the substrate 152. This regular structure is known as a "fiber texture". Generally, a fiber texture exists when a crystallographic axis is aligned along some preferred direction of a crystalline aggregate.
- SURFACE ETCHING For improved light-trapping characteristics, it is greatly desired to etch the top surface 162 of the iZnO layer.
- known processes such as etching by dipping the surface in a bath can be used. Etching produces a regularly-textured surface with facets with sizes in the range of 2 to 300 microns.
- the layer 162 can be etched while it grows during the sputtering process.
- One major advantage is that it will achieve the same textured result as an acid bath but in less time, by eliminating a specific step dedicated to etching. This eliminates not just the time of the acid etching itself, but all of the time and energy associated with removing the device 150 from the sputtering chamber, performing the acid etch, placing the device into the same or a different sputtering chamber for the next step, and recreating a high vacuum.
- Another advantage is that exposing the iZnO layer 154 to an etching agent, as is done in the prior art acid bath, leaves an inherently dirty surface; residual chemicals from the etching agent will remain behind, requiring an additional cleaning process. By eliminating the post-growth etching step and its etching agent, there will be less chemical residue to remove .
- a small modification is made in the sputtering step. Instead of inserting only an inert gas such as Argon into the sputtering chamber, a small amount of water vapor also is injected periodically.
- the water vapor initially exists as molecules of H 2 O in a gaseous state.
- a thin layer 156 of ZnO lightly doped with an impurity is deposited by sputtering.
- the impurity used preferably is aluminum, but may be gallium, indium, or boron.
- This layer 154 is known as conductive zinc oxide or "c-ZnO".
- Layer 154 preferably is approximately 250nm thick and is from one half to one-third the thickness of the iZnO layer.
- Prior art techniques usually provide for the c-ZnO to be doped at roughly 2-5% by weight with impurities. In the present invention, the rate is approximately 1.5%. By thus only lightly doping the zinc oxide, the c-ZnO transmits light of longer wavelengths more readily than does 2-5% doped zinc oxide, as shown in FIGURE 14, while retaining the desired conductive characteristics of 2-5% doped zinc oxide.
- the target will be a substance containing zinc and aluminum in the exact ratio desired.
- layer being deposited will have the constituents in the same ratio as the target.
- the target may be of pure zinc, as was the target used to sputter the i-ZnO layer.
- a gas containing the doping agent is injected into the sputtering chamber during the sputtering process.
- the doping agent will be incorporated into the new layer being formed. This has the advantage of enabling a change of the doping ratio for subsequent operations in a single chamber without having to mechanically change the target. Furthermore, it also is possible to change the percentage of doping agent at different times throughout the growth of the layer 156.
- FIGURE 14 shows the light transmission characteristics of 2-5% doped zinc oxide by dashed-line curve 164.
- 2-5% doped zinc oxide transmits approximately 85% of the light.
- the curve 168 shows the light transmission characteristics of lightly-doped (1.5%) zinc oxide.
- the transmission curve is substantially identical to that for 2-5% doped zinc oxide.
- lightly-doped zinc oxide continues to transmit a large percentage of light at wavelengths in the 800-1100nm region. It is only for light of wavelengths greater than approximately llOOnm that lightly doped zinc oxide begins to attenuate significant portions of the light.
- section 165 of the conducting layer 156 is made thinner or in spots removed entirely, forming holes or pits extending through or partially through layer 156. These holes are believed to allow the transmission of more light without significantly reducing the electrical current-carrying capacity of the layer 156.
- the holes 165 will cover roughly 30-50% of the surface area of the layer 156. The net result is believed to be an increase in the current output of the photovoltaic device for a given amount of light received.
- Etching can be used to make the holes 165, such as by dipping into an acid bath.
- Another process is to simultaneously grow layer 156 while etching with OH " ions from disassociated water vapor during the sputtering process, as described above for simultaneously growing and etching layer 154.
- the location of the resulting holes 165 will be random, and the shape of the holes may be irregular. Generally, the random locations and shapes are acceptable.
- the etching process should be controlled so as to not etch away more than 50% of the surface area, and so as not to produce islands at doped ZnO which are isolated from the rest of layer 156.
- photolithograph etching which is known and used in the semiconductor manufacturing art, may be used. This has the advantage of providing exact control over the location of the holes and the ability to ensure that islands are not developed.
- the simultaneous etching should be used, as it is more controllable than an acid bath, and cheaper and easier than photolithographic etching.
- the layer of pure zinc oxide preferably is between 2 and 3 times as thick as the conductive zinc oxide layer 156.
- This structure takes advantage of the fact that the "haze factor" of pure zinc oxide is very similar to that of doped zinc oxide, but pure zinc oxide has a considerably better transmission characteristic, as it is shown in FIGURE 14.
- "light trapping" retaining photons in the active layer 154
- a higher "haze factor” is kept at a high level while improving the current density output of the device.
- this improvement can produce a current density improvement in any thin-film photovoltaic device. The magnitude of the possible improvement is as much as 30% or more.
Landscapes
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Photovoltaic Devices (AREA)
Abstract
L'invention porte sur une structure photovoltaïque qui comporte un revêtement en couche mince sur un substrat transparent, la couche mince comportant une quantité efficace de silicium nanocristallin incorporé dans une matrice de silicium amorphe et/ou microcristallin. Une couche d'oxyde conducteur transparent sur une couche d'oxyde transparent non conducteur fournit une capacité de piégeage de la lumière ainsi qu'une conductivité électrique là où c’est nécessaire. Un réacteur de dépôt chimique en phase vapeur (« CVD ») fournit une distribution de gaz améliorée aux substrats qui sont revêtus dans le réacteur. L'invention porte également sur un procédé de pulvérisation cathodique amélioré et sur un procédé de fabrication par CVD assisté par plasma RF amélioré utilisant, tous deux, des taux élevés d'hydrogène dans le mélange hydrogène-silane et des niveaux de puissance électrique élevés pour le plasma afin d'augmenter la vitesse et de diminuer le coût de fabrication.
Applications Claiming Priority (8)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/077,273 | 2008-03-17 | ||
US12/077,271 | 2008-03-17 | ||
US12/077,275 | 2008-03-17 | ||
US12/077,275 US20090233007A1 (en) | 2008-03-17 | 2008-03-17 | Chemical vapor deposition reactor and method |
US12/077,273 US20090229664A1 (en) | 2008-03-17 | 2008-03-17 | Method of manufacturing nanocrystalline photovoltaic devices |
US12/077,272 US7993752B2 (en) | 2008-03-17 | 2008-03-17 | Transparent conductive layer and method |
US12/077,272 | 2008-03-17 | ||
US12/077,271 US20090229663A1 (en) | 2008-03-17 | 2008-03-17 | Nanocrystalline photovoltaic device |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2009117083A2 true WO2009117083A2 (fr) | 2009-09-24 |
WO2009117083A3 WO2009117083A3 (fr) | 2010-01-14 |
Family
ID=41091440
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2009/001664 WO2009117083A2 (fr) | 2008-03-17 | 2009-03-17 | Dispositif photovoltaïque et procédé |
Country Status (2)
Country | Link |
---|---|
TW (1) | TW201001728A (fr) |
WO (1) | WO2009117083A2 (fr) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2314732A1 (fr) * | 2009-10-21 | 2011-04-27 | Von Ardenne Anlagentechnik GmbH | Procédé de revêtement d'un substrat doté d'une couche de TCO et cellule solaire en couche fine |
US8114702B2 (en) | 2010-06-07 | 2012-02-14 | Boris Gilman | Method of manufacturing a monolithic thin-film photovoltaic device with enhanced output voltage |
CN114792744A (zh) * | 2022-05-07 | 2022-07-26 | 通威太阳能(眉山)有限公司 | 太阳电池及其制备方法和应用 |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2011109227A1 (fr) * | 2010-03-01 | 2011-09-09 | First Solar, Inc. | Fabrication d'un panneau photovoltaïque |
EP2666188A1 (fr) * | 2011-01-19 | 2013-11-27 | TEL Solar AG | Procédé de fabrication d'une multicouche d'un oxyde conducteur transparent |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5078803A (en) * | 1989-09-22 | 1992-01-07 | Siemens Solar Industries L.P. | Solar cells incorporating transparent electrodes comprising hazy zinc oxide |
US6200680B1 (en) * | 1994-06-06 | 2001-03-13 | Nippon Shokubai Co., Ltd. | Fine zinc oxide particles, process for producing the same, and use thereof |
US6261694B1 (en) * | 1999-03-17 | 2001-07-17 | General Electric Company | Infrared reflecting coatings |
US6331672B1 (en) * | 1996-03-01 | 2001-12-18 | Canon Kabushiki Kaisha | Photovoltaic cell and method for manufacturing the same |
US6896981B2 (en) * | 2001-07-24 | 2005-05-24 | Bridgestone Corporation | Transparent conductive film and touch panel |
US20060118406A1 (en) * | 2004-12-08 | 2006-06-08 | Energy Photovoltaics, Inc. | Sputtered transparent conductive films |
-
2009
- 2009-03-17 TW TW098108571A patent/TW201001728A/zh unknown
- 2009-03-17 WO PCT/US2009/001664 patent/WO2009117083A2/fr active Application Filing
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5078803A (en) * | 1989-09-22 | 1992-01-07 | Siemens Solar Industries L.P. | Solar cells incorporating transparent electrodes comprising hazy zinc oxide |
US6200680B1 (en) * | 1994-06-06 | 2001-03-13 | Nippon Shokubai Co., Ltd. | Fine zinc oxide particles, process for producing the same, and use thereof |
US6331672B1 (en) * | 1996-03-01 | 2001-12-18 | Canon Kabushiki Kaisha | Photovoltaic cell and method for manufacturing the same |
US6261694B1 (en) * | 1999-03-17 | 2001-07-17 | General Electric Company | Infrared reflecting coatings |
US6896981B2 (en) * | 2001-07-24 | 2005-05-24 | Bridgestone Corporation | Transparent conductive film and touch panel |
US20060118406A1 (en) * | 2004-12-08 | 2006-06-08 | Energy Photovoltaics, Inc. | Sputtered transparent conductive films |
Non-Patent Citations (1)
Title |
---|
'Photovoltaic Specialists Conference, Conference Record of the Thirty-first IEEE', 2005 article LI ET AL.: 'Some observations on seeding and stability of nc-Si solar cells.', pages 1420 - 1423 * |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2314732A1 (fr) * | 2009-10-21 | 2011-04-27 | Von Ardenne Anlagentechnik GmbH | Procédé de revêtement d'un substrat doté d'une couche de TCO et cellule solaire en couche fine |
US8669463B2 (en) | 2009-10-21 | 2014-03-11 | Von Ardenne Anlagentechnik Gmbh | Method for depositing a transparent conductive oxide (TCO) film on a substrate and thin-film solar cell |
EP2314732B2 (fr) † | 2009-10-21 | 2016-08-03 | VON ARDENNE GmbH | Procédé de revêtement d'un substrat doté d'une couche de TCO et cellule solaire en couche fine |
US8114702B2 (en) | 2010-06-07 | 2012-02-14 | Boris Gilman | Method of manufacturing a monolithic thin-film photovoltaic device with enhanced output voltage |
CN114792744A (zh) * | 2022-05-07 | 2022-07-26 | 通威太阳能(眉山)有限公司 | 太阳电池及其制备方法和应用 |
CN114792744B (zh) * | 2022-05-07 | 2024-04-02 | 通威太阳能(成都)有限公司 | 太阳电池及其制备方法和应用 |
Also Published As
Publication number | Publication date |
---|---|
WO2009117083A3 (fr) | 2010-01-14 |
TW201001728A (en) | 2010-01-01 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US7993752B2 (en) | Transparent conductive layer and method | |
US20090229663A1 (en) | Nanocrystalline photovoltaic device | |
US20090229664A1 (en) | Method of manufacturing nanocrystalline photovoltaic devices | |
US7074641B2 (en) | Method of forming silicon-based thin film, silicon-based thin film, and photovoltaic element | |
US6855621B2 (en) | Method of forming silicon-based thin film, method of forming silicon-based semiconductor layer, and photovoltaic element | |
US6166319A (en) | Multi-junction photovoltaic device with microcrystalline I-layer | |
KR20090031492A (ko) | 광전 소자용 미정질 실리콘 막을 증착하기 위한 방법 및장치 | |
EP1553637A2 (fr) | Dispositif photovoltaique | |
US20080188062A1 (en) | Method of forming microcrystalline silicon film | |
US6488995B1 (en) | Method of forming microcrystalline silicon film, method of fabricating photovoltaic cell using said method, and photovoltaic device fabricated thereby | |
JPH11243218A (ja) | 積層型光起電力素子 | |
JPH11243219A (ja) | 積層型光起電力素子 | |
JP2002343993A (ja) | 薄膜多結晶太陽電池及びその形成方法 | |
US20090233007A1 (en) | Chemical vapor deposition reactor and method | |
WO2009117083A2 (fr) | Dispositif photovoltaïque et procédé | |
Takano et al. | Light-weight and large-area solar cell production technology | |
US20090101201A1 (en) | Nip-nip thin-film photovoltaic structure | |
WO2010023947A1 (fr) | Procédé de fabrication d'un dispositif de conversion photoélectrique, dispositif de conversion photoélectrique, et système de fabrication d'un dispositif de conversion photoélectrique | |
US4799968A (en) | Photovoltaic device | |
Rech et al. | Amorphous and microcrystalline silicon based solar cells and modules on textured zinc oxide coated glass substrates | |
US6706335B2 (en) | Method of forming silicon-based thin film | |
JP2004363580A (ja) | 光電変換装置および光発電装置 | |
CN102021538A (zh) | 薄膜沉积方法 | |
Schropp | Amorphous and microcrystalline silicon solar cells | |
JP2004363579A (ja) | 光電変換装置および光発電装置 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 09721908 Country of ref document: EP Kind code of ref document: A2 |
|
NENP | Non-entry into the national phase in: |
Ref country code: DE |
|
WWE | Wipo information: entry into national phase |
Ref document number: 6617/CHENP/2010 Country of ref document: IN |
|
122 | Ep: pct application non-entry in european phase |
Ref document number: 09721908 Country of ref document: EP Kind code of ref document: A2 |