EP1998902A2 - Formation a haut rendement de couche semi-condutrice en utilisant un materiau chalcogene et intermetalique - Google Patents

Formation a haut rendement de couche semi-condutrice en utilisant un materiau chalcogene et intermetalique

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Publication number
EP1998902A2
EP1998902A2 EP07757446A EP07757446A EP1998902A2 EP 1998902 A2 EP1998902 A2 EP 1998902A2 EP 07757446 A EP07757446 A EP 07757446A EP 07757446 A EP07757446 A EP 07757446A EP 1998902 A2 EP1998902 A2 EP 1998902A2
Authority
EP
European Patent Office
Prior art keywords
particles
chalcogen
group
chalcogenide
iiia
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07757446A
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German (de)
English (en)
Inventor
Matthew R. Robinson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Leidholm Craig R
Van Duren Jeroen KJ
Original Assignee
Leidholm Craig R
Van Duren Jeroen KJ
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US11/361,433 external-priority patent/US7700464B2/en
Priority claimed from US11/361,515 external-priority patent/US20070163640A1/en
Priority claimed from US11/361,522 external-priority patent/US20070166453A1/en
Priority claimed from US11/361,498 external-priority patent/US20070163639A1/en
Priority claimed from US11/361,103 external-priority patent/US20070169809A1/en
Priority claimed from US11/361,464 external-priority patent/US20070169810A1/en
Priority claimed from US11/361,523 external-priority patent/US20070169811A1/en
Priority claimed from US11/395,668 external-priority patent/US8309163B2/en
Priority claimed from US11/394,849 external-priority patent/US20070163641A1/en
Priority claimed from US11/395,438 external-priority patent/US20070163643A1/en
Application filed by Leidholm Craig R, Van Duren Jeroen KJ filed Critical Leidholm Craig R
Publication of EP1998902A2 publication Critical patent/EP1998902A2/fr
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—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
    • H01L31/0256—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 the material
    • H01L31/0264—Inorganic materials
    • H01L31/032—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312
    • H01L31/0322—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312 comprising only AIBIIICVI chalcopyrite compounds, e.g. Cu In Se2, Cu Ga Se2, Cu In Ga Se2
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/11—Making amorphous alloys
    • 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
    • H01L31/04—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
    • 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
    • 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
    • H01L31/04—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
    • 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
    • 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
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • 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
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/1876—Particular processes or apparatus for batch treatment of the devices
    • 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
    • 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 to semiconductor thin films and more specifically to fabrication of solar cells that use active layers based on IB-IIIA-VIA compounds.
  • Solar cells and solar modules convert sunlight into electricity. These electronic devices have been traditionally fabricated using silicon (Si) as a light-absorbing, semiconducting material in a relatively expensive production process. To make solar cells more economically viable, solar cell device architectures have been developed that can inexpensively make use of thin-film, light-absorbing semiconductor materials such as copper-indium-gallium-sulfo-di-selenide, Cu(In, Ga)(S, Se) 2 , 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. The back electrode layer is often Mo, while the junction partner is often CdS.
  • a transparent conductive oxide (TCO) such as zinc oxide (ZnO x ) is formed on the junction partner layer and is typically used as a transparent electrode.
  • CIS-based solar cells have been demonstrated to have power conversion efficiencies exceeding 19%.
  • a central challenge in cost-effectively constructing a large-area CIGS-based solar cell or module is that the elements of the CIGS 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.
  • Achieving precise stoichiometric composition over relatively large substrate areas is, however, difficult using traditional vacuum-based deposition processes. For example, it is difficult to deposit compounds and/or alloys containing more than one element by sputtering or evaporation. Both techniques rely on deposition approaches that are limited to line-of-sight and limited-area sources, tending to result in poor surface coverage.
  • Line-of-sight trajectories and limited-area sources can result in non-uniform distribution of the elements in all three dimensions and/or poor film-thickness uniformity over large areas. These non-uniformities can occur over the nano-, meso-, and/or macroscopic scales. Such non-uniformity also alters the local stoichiometric ratios of the absorber layer, decreasing the potential power conversion efficiency of the complete cell or module.
  • chalcogenide powders as precursor material, e.g. micron-sized CIS powders deposited via screen-printing, amorphous quarternary selenide nanopowder or a mixture of amorphous binary selenide nanopowders deposited via spraying on a hot substrate, and other examples [(1) Vervaet, A. et al., E. C. Photovoltaic Sol. Energy Conf, Proc. Int. Conf, 10th (1991), 900-3.; (2) Journal of Electronic Materials, Vol. 27, No. 5, 1998, p. 433; Ginley et al.; (3) WO 99,378,32; Ginley et al.; (4) US 6,126,740]. So far, no promising results have been obtained when using chalcogenide powders for fast processing to form CIGS thin-films suitable for solar cells.
  • IB-IIIA-chalcogenide compound film suitable for thin- film solar cells Due to high temperatures and/or long processing times required for sintering, formation of a IB-IIIA-chalcogenide compound film suitable for thin- film solar cells is challenging when starting from IB-IIIA-chalcogenide powders where each individual particle contains appreciable amounts of all IB, IIIA, and VIA elements involved, typically close to the stoichiometry of the final IB-IIIA-chalcogenide compound film.
  • temperature-sensitive substrates limit the maximum temperature that can be used for processing a precursor layer into CIS or CIGS to a level that is typically well below the melting point of the ternary or quarternary selenide (>900°C). A fast and high-temperature process, therefore, is less preferred. Both time and temperature restrictions, therefore, have not yet resulted in promising results on suitable substrates using multinary selenides as starting materials.
  • starting materials may be based on a mixture of binary selenides, which at a temperature above 500 0 C or lower would result in the formation of a liquid phase that would enlarge the contact area between the initially solid powders and, thereby, accelerate the sintering process as compared to an all-solid process.
  • a temperature above 500 0 C or lower would result in the formation of a liquid phase that would enlarge the contact area between the initially solid powders and, thereby, accelerate the sintering process as compared to an all-solid process.
  • Unfortunately for most binary selenide compositions, below 500 0 C hardly any liquid phase is created.
  • the present invention provides for high throughput processes for formation of high quality precursor layers which are processed into dense films.
  • the resulting dense films may be useful in a variety of industries and applications, including but not limited to, the manufacture of photovoltaic devices and solar cells. More specifically, the present invention has particular application in the formation of precursor layers for thin film solar cells.
  • the present invention provides for more efficient and simplified creation of a dispersion, and the resulting coating thereof. At least some of these and other objectives described herein will be met by various embodiments of the present invention.
  • the present involves the introduction of IB and IDA elements in the form of chalcogenide nanopowders and combining these chalcogenide nanopowders with an additional source of chalcogen such as selenium or sulfur, tellurium or a mixture of two or more of these, to form a group IB-IIIA-chalcogenide compound.
  • a compound film may be formed from a mixture of binary selenides, sulfides, or tellurides and selenium, sulfur or tellurium.
  • the compound film may be formed using core-shell nanoparticles having core nanoparticles containing group IB and/or group IIIA elements coated with a non-oxygen chalcogen material.
  • the method comprises forming a precursor material comprising group IB and/or group IIIA particles of any shape.
  • the method may include forming a precursor layer of the precursor material over a surface of a substrate.
  • the method may further include heating the particle precursor material in a substantially oxygen-free chalcogen atmosphere to a processing temperature sufficient to react the particles and to release chalcogen from the chalcogenide particles, wherein the chalcogen assumes a liquid form and acts as a flux to improve intermixing of elements to form a group IB-IIIA-chalcogenide film at a desired stoichiometric ratio.
  • the chalcogen atmosphere may provide a partial pressure greater than or equal to the vapor pressure of liquid chalcogen in the precursor layer at the processing temperature.
  • the method comprises forming a precursor material comprising group IB and/or group IIIA and/or group VIA particles of any shape.
  • the method may include forming a precursor layer of the precursor material over a surface of a substrate.
  • the method may further include heating the particle precursor material in a substantially oxygen-free chalcogen atmosphere to a processing temperature sufficient to react the particles and to release chalcogen from the chalcogenide particles, wherein the chalcogen assumes a liquid form and acts as a flux to improve intermixing of elements to form a group IB- IIIA-chalcogenide film at a desired stoichiometric ratio.
  • the suitable atmosphere may be a selenium atmosphere.
  • the suitable atmosphere may comprise of a selenium atmosphere providing a partial pressure greater than or equal to vapor pressure of selenium in the precursor layer.
  • the suitable atmosphere may comprise of a non-oxygen atmosphere containing chalcogen vapor at a partial pressure of the chalcogen greater than or equal to a vapor pressure of the chalcogen at the processing temperature and processing pressure to minimize loss of chalcogen from the precursor layer, wherein the processing pressure is a non-vacuum pressure.
  • the suitable atmosphere may comprises of a non-oxygen atmosphere containing chalcogen vapor at a partial pressure of the chalcogen greater than or equal to a vapor pressure of the chalcogen at the processing temperature and processing pressure to minimize loss of chalcogen from the precursor layer, wherein the processing pressure is a non-vacuum pressure and wherein the particles are one or more types of binary chalcogenides.
  • the method comprises forming a precursor material comprising group IB-chalcogenide and/or group IIIA-chalcogenide particles, wherein an overall amount of chalcogen in the particles relative to an overall amount of chalcogen in a group IB-IIIA-chalcogenide film created from the precursor material, is at a ratio that provides an excess amount of chalcogen in the precursor material.
  • the method also includes using the precursor material to form a precursor layer over a surface of a substrate.
  • the particle precursor material is heated in a suitable atmosphere to a temperature sufficient to melt the particles and to release at least the excess amount of chalcogen from the chalcogenide particles, wherein the excess amount of chalcogen assumes a liquid form and acts as a flux to improve intermixing of elements to form the group IB-IIIA-chalcogenide film at a desired stoichiometric ratio.
  • the overall amount of chalcogen in the precursor material is an amount greater than or equal to a stoichiometric amount found in the IB-IIIA-chalcogenide film.
  • the overall amount of chalcogen may be greater than a minimum amount necessary to form the final IB-IIIA-chalcogenide at the desired stoichiometric ratio.
  • the overall amount of chalcogen in the precursor material may be an amount greater than or equal to the sum of: 1) the stoichiometric amount found in the IB-IIIA- chalcogenide film and 2) a minimum amount of chalcogen necessary to account for chalcogen lost during processing to form the group IB-IIIA-chalcogenide film having the desired stoichiometric ratio.
  • the overall amount may be about 2 times greater than a minimum amount necessary to form the IB-IIIA-chalcogenide film at the desired stoichiometric ratio.
  • the particles may be chalcogen-rich particles and/or selenium-rich particles and/or sulfur- rich particles and/or tellurium-rich particles.
  • the overall amount of chalcogen in the group IB-chalcogenide particles is greater than an overall amount of chalcogen in the group IIIA particles.
  • the overall amount of chalcogen in the group IB-chalcogenide particles may be less than an overall amount of chalcogen in the group IIIA particles.
  • the group IB-chalcogenide particles may include a mix of particles, wherein some particles are chalcogen-rich and some are not, and wherein the chalcogen-rich particles outnumber the particles that are not.
  • the group IIIA-chalcogenide particles may include a mix of particles, wherein some particles are chalcogen-rich and some are not, and wherein the chalcogen-rich particles outnumber the particles that are not.
  • the particles may be IBxVIAy and/or IHAaVIAb particles, wherein x ⁇ y and a ⁇ b.
  • the resulting group IB-IIIA-chalcogenide film may be CuzIn(l-x)GaxSe 2, wherein 0.5 ⁇ z ⁇ 1.5 and 0 ⁇ x ⁇ 1.
  • the amount of chalcogen in the particles may be above the stoichiometric ratio required to form the film.
  • the particles may be substantially oxygen-free particles.
  • the particles may be particles that do not contain oxygen above about 5.0 weight-percentage.
  • the group IB element may be copper.
  • the group IIIA element may be comprised of gallium and/or indium and/or aluminum.
  • the chalcogen may be selenium or sulfur or tellurium.
  • the particles may be alloy particles.
  • the particles may be binary alloy particles and/or ternary alloy particles and/or multi-nary alloy particles and/or compound particles and/or solid-solution particles.
  • the precursor material may include group IB-chalcogenide particles containing a chalcogenide material in the form of an alloy of a chalcogen and an element of group IB and/or wherein the particle precursor material includes group IIIA-chalcogenide particles containing a chalcogenide material in the form of an alloy of a chalcogen and one or more elements of group IIIA.
  • the group IB-chalcogenide may be comprised of CGS and the group IIIA-chalcogenide may be comprised of CIS.
  • the method may include adding an additional source of chalcogen prior to heating the precursor material.
  • the method may include adding an additional source of chalcogen during heating of the precursor material.
  • the method may further include adding an additional source of chalcogen before, simultaneously with, or after forming the precursor layer.
  • the method may include adding an additional source of chalcogen by forming a layer of the additional source over the precursor layer.
  • the method may include adding an additional source of chalcogen on the substrate prior to forming the precursor layer.
  • a vacuum-based process may be used to add an additional source of chalcogen in contact with the precursor layer.
  • the amounts of the group IB element and amounts of chalcogen in the particles may be selected to be at a stoichiometric ratio for the group IB chalcogenide that provides a melting temperature less than a highest melting temperature found on a phase diagram for any stoichiometric ratio of elements for the group IB chalcogenide.
  • the method may include using a source of extra chalcogen that includes particles of an elemental chalcogen.
  • the extra source of chalcogen may be a chalcogenide.
  • the amounts of the group IIIA element and amounts of chalcogen in the particles may be selected to be at a stoichiometric ratio for the group IIIA chalcogenide that provides a melting temperature less than a highest melting temperature found on a phase diagram for any stoichiometric ratio of elements for the group IIIA chalcogenide.
  • the group IB-chalcogenide particles may be CuxSey, wherein the values for x and y are selected to create a material with a reduced melting temperature as determined by reference to the highest melting temperature on a phase diagram for Cu-Se.
  • the group IB- chalcogenide particles may be CuxSey, wherein x is in the range of about 2 to about 1 and y is in the range of about 1 to about 2.
  • the group IIIA-chalcogenide particles may be InxSey, wherein the values for x and y are selected to create a material with a reduced melting temperature as determined by reference to the highest melting temperature on a phase diagram for In-Se.
  • the group IIIA-chalcogenide particles may be InxSey, wherein x is in the range of about 1 to about 6 and y is in the range of about 0 to about 7.
  • the group IIIA-chalcogenide particles may be GaxSey, wherein the values for x and y are selected to create a material with a reduced melting temperature as determined by reference to the highest melting temperature on a phase diagram for Ga-Se.
  • the group IIIA-chalcogenide particles may be GaxSey, wherein x is in the range of about 1 to about 2 and y is in the range of about 1 to about 3.
  • the melting temperature may be at a eutectic temperature for the material as indicated on the phase diagram.
  • the group IB or IIIA chalcogenide may have a stoichiometric ratio that results in the group IB or IIIA chalcogenide being less thermodynamically stable than the group IB-IIIA-chalcogenide compound.
  • the method may further include forming at least a second layer of a second precursor material over the precursor layer, wherein the second precursor material comprises group IB-chalcogenide and/or group IIIA-chalcogenide particles and wherein the second precursor material has particles with a different IB-to-chalcogen ratio and/or particles with a different IIIA-to-chalcogen ratio than the particles of the precursor material of the first precursor layer.
  • the group IB-chalcogenide in the first precursor layer may be comprised of CuxSey and the group IB-chalcogenide in the second precursor layer comprises CuzSey, wherein x > z.
  • the CIlJG ratios may be the same for each layer and only the chalcogen amount varies.
  • the method may include depositing a thin group IB-IIIA chalcogenide layer on the substrate to serve as a nucleation plane for film growth from the precursor layer which is deposited on top of the thin group IB-IIIA chalcogenide layer.
  • a planar nucleation layer of a group IB-IIIA chalcogenide may be deposited prior to forming the precursor layer.
  • the method may include depositing a thin CIGS layer on the substrate to serve as a nucleation field for CIGS growth from the precursor layer which is printed on top of the thin CIGS layer.
  • the film is formed from a precursor layer of the particles and a layer of a sodium containing material in contact with the precursor layer.
  • the film is formed from a precursor layer of the particles and a layer in contact with the precursor layer and containing at least one of the following materials: a group IB element, a group IIIA element, a group VIA element, a group IA element, a binary and/or multinary alloy of any of the preceding elements, a solid solution of any of the preceding elements, copper, indium, gallium, selenium, copper indium, copper gallium, indium gallium, sodium, a sodium compound, sodium fluoride, sodium indium sulfide, copper selenide, copper sulfide, indium selenide, indium sulfide, gallium selenide, gallium sulfide, copper indium selenide, copper indium sulfide, copper gallium selenide, copper gallium sulfide, indium gallium
  • the particles may contain sodium.
  • the particles may be doped to contain sodium at about 1 at% or less.
  • the particles may contain at least one of the following materials: Cu-Na, In-Na, Ga-Na, Cu-In-Na, Cu-In-Ga-Na, Cu-Ga-Na, In-Ga-Na, Na-Se, Cu-Se-Na, In-Se- Na, Ga-Se-Na, Cu-In-Se-Na, Cu-Ga-Se-Na, In-Ga-Se-Na, Cu-In-Ga-Se-Na, Na-S, Cu-S-Na, In- S-Na, Ga-S-Na, Cu-In-S-Na, Cu-Ga-S-Na, In-Ga-S-Na, or Cu-In-Ga-S-Na.
  • the film may be formed from a precursor layer of the particles and an ink containing a sodium compound with an organic counter-ion or a sodium compound with an inorganic counter-ion.
  • the film may be formed from a precursor layer of the particles and a layer of a sodium containing material in contact with the precursor layer and/or particles containing at least one of the following materials: Cu-Na, In-Na, Ga-Na, Cu-In-Na, Cu-Ga-Na, In-Ga-Na, Na-Se, Cu-Se-Na, In-Se-Na, Ga-Se-Na, Cu-In-Se-Na, Cu-In-Ga-Na, Cu-Ga-Se-Na, In-Ga-Se-Na, Cu-In-Ga-Se-Na, Na-S, Cu-S-Na, In-S-Na, Ga-S-Na, Cu-In-S-Na, Cu-In-S-N
  • a precursor material is provided that is comprised of group IB-chalcogenide particles containing a substantially oxygen- free chalcogenide material in the form of an alloy of a chalcogen with an element of group IB; and/or group IIIA-chalcogenide particles containing a substantially oxygen- free chalcogenide material in the form of an alloy of a chalcogen with one or more elements of group IIIA.
  • the group IB- chalcogenide particles and/or the group IIIA-chalcogenide particles may have a stoichiometric ratio that provides a source of surplus chalcogen, wherein the overall amount of chalcogen in the precursor material is an amount greater than or equal to a stoichiometric amount found in the IB- IIIA-chalcogenide film.
  • the overall amount of chalcogen in the precursor material is an amount greater than or equal to the sum of: 1) the stoichiometric amount found in the IB-IIIA- chalcogenide film and 2) a minimum amount of chalcogen necessary to account for chalcogen lost during processing to form the group IB-IIIA-chalcogenide film having the desired stoichiometric ratio.
  • the overall amount may be greater than a minimum amount necessary to form the IB-IIIA-chalcogenide film at the desired stoichiometric ratio.
  • the overall amount may be about 2 times greater than a minimum amount necessary to form the IB-IIIA-chalcogenide film at the desired stoichiometric ratio.
  • a liquid ink may be made using one or more liquid metals.
  • 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.
  • the temperature of the Cu-Ga-In 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 to the ink and/or a film formed from the ink by exposure to selenium vapor, e.g., before, during, or after annealing.
  • a process comprising of formulating a dispersion of solid and/or liquid particles comprising group IB and/or IIIA elements, and, optionally, at least one group VIA element.
  • the process includes depositing the dispersion onto a substrate to form a layer on the substrate and reacting the layer in a suitable atmosphere to form a film.
  • at least one set of the particles are inter-metallic particles containing at least one group IB-IIIA inter- metallic phase.
  • the particles may contain an inter-metallic phase and is not limited to only group IB-IIIA phases.
  • composition comprised of a plurality of particles comprising group IB and/or IIIA elements, and, optionally, at least one group VIA element. At least one set of the particles contains at least one group IB-IIIA inter- metallic alloy phase.
  • the method may include formulating a dispersion of particles comprising group IB and/or IIIA elements, and, optionally, at least one group VIA element.
  • the method may include depositing the dispersion onto a substrate to form a layer on the substrate and reacting the layer in a suitable atmosphere to form a film.
  • At least one set of the particles contain a group IB-poor, group IB-IIIA alloy phase.
  • group IB-poor particles contribute less than about 50 molar percent of group IB elements found in all of the particles.
  • the group IB-poor, group IB-IIIA alloy phase particles may be a sole source of one of the group IIIA elements.
  • the group IB-poor, group IB-IIIA alloy phase particles may contain an inter-metallic phase and may be a sole source of one of the group IIIA elements.
  • the group IB-poor, group IB-IIIA alloy phase particles may contain an inter- metallic phase and are a sole source of one of the group IIIA elements.
  • the group IB-poor, group IB-IIIA alloy phase particles may be Cuiln 2 particles and are a sole source of indium in the material.
  • the film and/or final compound may include a group IB-IIIA-VIA compound.
  • the reacting step may comprise of heating the layer in the suitable atmosphere.
  • the depositing step may include coating the substrate with the dispersion. At least one set of the particles in the dispersion may be in the form of nanoglobules. At least one set of the particles in the dispersion may be in the form of nanoglobules and contain at least one group IIIA element. At least one set of the particles in the dispersion may be in the form of nanoglobules comprising of a group IIIA element in elemental form.
  • the inter-metallic phase is not a terminal solid solution phase.
  • the inter-metallic phase is not a solid solution phase.
  • the inter-metallic particles may contribute less than about 50 molar percent of group IB elements found in all of the particles.
  • the inter-metallic particles may contribute less than about 50 molar percent of group IIIA elements found in all of the particles.
  • the inter- metallic particles may contribute less than about 50 molar percent of the group IB elements and less than about 50 molar percent of the group IIIA elements in the dispersion deposited on the substrate.
  • the inter-metallic particles may contribute less than about 50 molar percent of the group IB elements and more than about 50 molar percent of the group IIIA elements in the dispersion deposited on the substrate.
  • the inter-metallic particles may contribute more than about 50 molar percent of the group IB elements and less than about 50 molar percent of the group IIIA elements in the dispersion deposited on the substrate.
  • the molar percent for any of the foregoing may be based on a total molar mass of the elements in all particles present in the dispersion.
  • at least some of the particles have a platelet shape.
  • a majority of the particles have a platelet shape.
  • substantially all of the particles have a platelet shape.
  • an inter-metallic material for use with the present invention is a binary material.
  • the inter-metallic material may be a ternary material.
  • the inter- metallic material may comprise of CUiIn 2 .
  • the inter-metallic material may be comprised of a composition in a ⁇ phase Of CUiIn 2 .
  • the inter-metallic material may be comprised of a composition in between a ⁇ phase of CUiIn 2 and a phase defined by Cul6In9.
  • the inter-metallic material may be comprised of CUiGa 2 .
  • the inter-metallic material may be comprised of an intermediate solid-solution of CUiGa 2 .
  • the inter-metallic material may be comprised of Cu68Ga38.
  • the inter-metallic material may be comprised of Cu7oGa3o.
  • the inter-metallic material may be comprised of Cu75Ga 25 .
  • the inter-metallic material may be comprised of a composition of Cu-Ga of a phase in between the terminal solid-solution and an intermediate solid-solution next to it.
  • the inter-metallic may be comprised of a composition of Cu-Ga in a ⁇ l phase (about 31.8 to about 39.8 wt % Ga).
  • the inter-metallic may be comprised of a composition of Cu-Ga in a ⁇ 2 phase (about 36.0 to about 39.9 wt % Ga).
  • the inter-metallic may be comprised of a composition of Cu-Ga in a ⁇ 3 phase (about 39.7 to about -44.9 wt % Ga).
  • the inter-metallic may be comprised of a composition of Cu-Ga in a phase between ⁇ 2 and ⁇ 3.
  • the inter-metallic may be comprised of a composition of Cu-Ga in a phase between the terminal solid solution and ⁇ l .
  • the inter-metallic may be comprised of a composition of Cu-Ga in a ⁇ phase (about 66.7 to about 68.7 wt % Ga).
  • the inter-metallic material may be comprised of Cu- rich Cu-Ga.
  • Gallium may be incorporated as a group IIIA element in the form of a suspension of nanoglobules.
  • Nanoglobules of gallium may be formed by creating an emulsion of liquid gallium in a solution.
  • Gallium nanoglobules may be created by being quenched below room temperature.
  • a process according to the any of the embodiments hereins of the present invention may include maintaining or enhancing a dispersion of liquid gallium in solution by stirring, mechanical means, electromagnetic means, ultrasonic means, and/or the addition of dispersants and/or emulsifiers.
  • the process may include adding a mixture of one or more elemental particles selected from: aluminum, tellurium, or sulfur.
  • the suitable atmosphere may contain selenium, sulfur, tellurium, H 2 , CO, H 2 Se, H 2 S, Ar, N 2 or combinations or mixture thereof.
  • the suitable atmosphere may contain at least one of the following: H 2 , CO, Ar, and N 2 .
  • One or more classes of the particles may be doped with one or more inorganic materials.
  • one or more classes of the particles are doped with one or more inorganic materials chosen from the group of aluminum (Al), sulfur (S), sodium (Na), potassium (K), or lithium (Li).
  • embodiments of the present invention may include having a copper source that does not immediately alloy with In, and/or Ga.
  • a copper source that does not immediately alloy with In, and/or Ga.
  • One option would be to use (slightly) oxidized copper.
  • the other option would be to use CuxSey.
  • a reducing step may be desired. Basically, if elemental copper is used in liquid In and/or Ga, speed of the process between ink preparation and coating should be sufficient so that the particles have not grown to a size that will result in thickness non-uniform coatings.
  • the temperature range may that of the substrate only since that is typically the only one that should not be heated above its melting point. This holds for the lowest melting material in the substrate, being Al and other suitable substrates.
  • the method comprises forming a precursor material comprising group IB and/or group IDA particles of any shape.
  • the method may include forming a precursor layer of the precursor material over a surface of a substrate.
  • the method may further include heating the particle precursor material in a substantially oxygen-free chalcogen atmosphere to a processing temperature sufficient to react the particles and to release chalcogen from the chalcogenide particles, wherein the chalcogen assumes a liquid form and acts as a flux to improve intermixing of elements to form a group IB-IIIA-chalcogenide film at a desired stoichiometric ratio.
  • the chalcogen atmosphere may provide a partial pressure greater than or equal to the vapor pressure of liquid chalcogen in the precursor layer at the processing temperature.
  • the method comprises forming a precursor material comprising group IB and/or group IIIA and/or group VIA particles of any shape.
  • the method may include forming a precursor layer of the precursor material over a surface of a substrate.
  • the method may further include heating the particle precursor material in a substantially oxygen-free chalcogen atmosphere to a processing temperature sufficient to react the particles and to release chalcogen from the chalcogenide particles, wherein the chalcogen assumes a liquid form and acts as a flux to improve intermixing of elements to form a group IB- IIIA-chalcogenide film at a desired stoichiometric ratio.
  • the suitable atmosphere may be a selenium atmosphere.
  • the suitable atmosphere may comprise of a selenium atmosphere providing a partial pressure greater than or equal to vapor pressure of selenium in the precursor layer.
  • the suitable atmosphere may comprise of a non-oxygen atmosphere containing chalcogen vapor at a partial pressure of the chalcogen greater than or equal to a vapor pressure of the chalcogen at the processing temperature and processing pressure to minimize loss of chalcogen from the precursor layer, wherein the processing pressure is a non-vacuum pressure.
  • the suitable atmosphere may comprises of a non-oxygen atmosphere containing chalcogen vapor at a partial pressure of the chalcogen greater than or equal to a vapor pressure of the chalcogen at the processing temperature and processing pressure to minimize loss of chalcogen from the precursor layer, wherein the processing pressure is a non-vacuum pressure and wherein the particles are one or more types of binary chalcogenides.
  • the method includes forming a first layer of a first precursor material over a surface of a substrate, wherein the precursor material comprises group IB-chalcogenide and/or group IIIA-chalcogenide particles.
  • the method may include forming at least a second layer of a second precursor material over the first layer, wherein the second precursor material comprises group IB-chalcogenide and/or group IIIA-chalcogenide particles and wherein the second precursor material has a chalcogen content greater than that of the first material.
  • the method may also include heating the first layer and the second layer in a suitable atmosphere to a temperature sufficient to react the particles and to release at least the surplus amount of chalcogen from the chalcogenide particles, wherein the surplus amount of chalcogen assumes a liquid form and acts as a flux to improve intermixing of elements to form the group IB-IIIA-chalcogenide film at a desired stoichiometric ratio.
  • the method may include at least partially melting the particles to react the particles.
  • the group IB-chalcogenide in the precursor layer may be comprised of CuxSey and the group IB-chalcogenide in the precursor layer comprises CuzSey, wherein x > z.
  • the C/I/G ratios are the same for each layer and only the chalcogen amount varies.
  • the method comprises forming a precursor material comprising group IB and/or group IDA particles of any shape.
  • the method may include forming a precursor layer of the precursor material over a surface of a substrate.
  • the method may further include heating the particle precursor material in a substantially oxygen-free chalcogen atmosphere to a processing temperature sufficient to react the particles and to release chalcogen from the chalcogenide particles, wherein the chalcogen assumes a liquid form and acts as a flux to improve intermixing of elements to form a group IB-IIIA-chalcogenide film at a desired stoichiometric ratio.
  • the chalcogen atmosphere provides a partial pressure greater than or equal to the vapor pressure of liquid chalcogen in the precursor layer at the processing temperature.
  • the method comprises forming a precursor material comprising group IB and/or group IIIA and/or group VIA particles of any shape.
  • the method may include forming a precursor layer of the precursor material over a surface of a substrate.
  • the method may further include heating the particle precursor material in a substantially oxygen-free chalcogen atmosphere to a processing temperature sufficient to react the particles and to release chalcogen from the chalcogenide particles, wherein the chalcogen assumes a liquid form and acts as a flux to improve intermixing of elements to form a group IB- IIIA-chalcogenide film at a desired stoichiometric ratio.
  • the suitable atmosphere may be a selenium atmosphere.
  • the suitable atmosphere may comprise of a selenium atmosphere providing a partial pressure greater than or equal to vapor pressure of selenium in the precursor layer.
  • the suitable atmosphere may comprise of a non-oxygen atmosphere containing chalcogen vapor at a partial pressure of the chalcogen greater than or equal to a vapor pressure of the chalcogen at the processing temperature and processing pressure to minimize loss of chalcogen from the precursor layer, wherein the processing pressure is a non-vacuum pressure.
  • the suitable atmosphere may comprises of a non-oxygen atmosphere containing chalcogen vapor at a partial pressure of the chalcogen greater than or equal to a vapor pressure of the chalcogen at the processing temperature and processing pressure to minimize loss of chalcogen from the precursor layer, wherein the processing pressure is a non-vacuum pressure and wherein the particles are one or more types of binary chalcogenides.
  • a method comprises of forming a precursor material comprising group IB-chalcogenide and/or group IIIA-chalcogenide particles, wherein amounts of the group IB or IIIA element and amounts of chalcogen in the particles are selected to be at a desired stoichiometric ratio for the group IB or IIIA chalcogenide that provides a melting temperature less than a highest melting temperature found on a phase diagram for any stoichiometric ratio of elements for the group IB or IIIA chalcogenide.
  • the group IB-chalcogenide particles may be CuxSey, wherein the values for x and y are selected to create a material with a reduced melting temperature as determined by reference to the highest melting temperature on a phase diagram for CuSe.
  • the group IB- chalcogenide particles may be CuxSey, wherein x is in the range of about 2 to about 1 and y is in the range of about 1 to about 2.
  • the group IIIA-chalcogenide particles are InxSey, the values for x and y are selected to create a material with a reduced melting temperature as determined by reference to the highest melting temperature on a phase diagram for InSe.
  • the group IIIA- chalcogenide particles may be InxSey, wherein x is in the range of about 1 to about 6 and y is in the range of about 0 to about 7.
  • the group IIIA-chalcogenide particles may be GaxSey, the values for x and y are selected to create a material with a reduced melting temperature as determined by reference to the highest melting temperature on a phase diagram for GaSe.
  • the group IIIA-chalcogenide particles are GaxSey, wherein x is in the range of about 1 to about 2 and y is in the range of about 1 to about 3.
  • the melting temperature may be at a eutectic temperature.
  • the group IB or IIIA chalcogenide may have a stoichiometric ratio that results in the group IB or IIIA chalcogenide being less thermodynamically stable than the group IB-IIIA- chalcogenide compound.
  • a precursor material comprises of group IB-chalcogenide particles containing an oxygen-free chalcogenide material in the form of an alloy of a chalcogen with an element of group IB; and/or group IIIA- chalcogenide particles containing an oxygen-free chalcogenide material in the form of an alloy of a chalcogen with one or more elements of group IIIA.
  • the group IB-chalcogenide particles and/or the group IIIA-chalcogenide particles may have a stoichiometric ratio that provides a melting temperature less than a melting temperature of at least one other stoichiometric ratio of elements as found on a phase diagram for the group IB or IIIA chalcogenide.
  • the method comprises forming a precursor material comprising group IB and/or group IIIA particles of any shape.
  • the method may include forming a precursor layer of the precursor material over a surface of a substrate.
  • the method may further include heating the particle precursor material in a substantially oxygen-free chalcogen atmosphere to a processing temperature sufficient to react the particles and to release chalcogen from the chalcogenide particles, wherein the chalcogen assumes a liquid form and acts as a flux to improve intermixing of elements to form a group IB-IIIA-chalcogenide film at a desired stoichiometric ratio.
  • the chalcogen atmosphere provides a partial pressure greater than or equal to the vapor pressure of liquid chalcogen in the precursor layer at the processing temperature.
  • the method comprises forming a precursor material comprising group IB and/or group IIIA and/or group VIA particles of any shape.
  • the method may include forming a precursor layer of the precursor material over a surface of a substrate.
  • the method may further include heating the particle precursor material in a substantially oxygen-free chalcogen atmosphere to a processing temperature sufficient to react the particles and to release chalcogen from the chalcogenide particles, wherein the chalcogen assumes a liquid form and acts as a flux to improve intermixing of elements to form a group IB- IIIA-chalcogenide film at a desired stoichiometric ratio.
  • the suitable atmosphere may be a selenium atmosphere.
  • the suitable atmosphere may comprise of a selenium atmosphere providing a partial pressure greater than or equal to vapor pressure of selenium in the precursor layer.
  • the suitable atmosphere may comprise of a non-oxygen atmosphere containing chalcogen vapor at a partial pressure of the chalcogen greater than or equal to a vapor pressure of the chalcogen at the processing temperature and processing pressure to minimize loss of chalcogen from the precursor layer, wherein the processing pressure is a non-vacuum pressure.
  • the suitable atmosphere may comprises of a non-oxygen atmosphere containing chalcogen vapor at a partial pressure of the chalcogen greater than or equal to a vapor pressure of the chalcogen at the processing temperature and processing pressure to minimize loss of chalcogen from the precursor layer, wherein the processing pressure is a non-vacuum pressure and wherein the particles are one or more types of binary chalcogenides.
  • FIGs. 1A-1C are a sequence of schematic diagrams illustrating the formation of chalcogenide film from binary nanoparticles and chalcogen particles according to an embodiment of the present invention.
  • FIGs. 2A-2C are a sequence of schematic diagrams illustrating the formation of chalcogenide film from coated nanoparticles according to an alternative embodiment of the present invention.
  • FIG. 3 is a flow diagram illustrating the fabrication of a chalcogenide layer using inks formed from nanoparticles according to an embodiment of the present invention.
  • FIG. 4 is a schematic diagram of a photovoltaic cell according to an embodiment of the present invention.
  • Figures 5A-5C shows the use of chalcogenide planar particles according to one embodiment of the present invention.
  • Figures 6A-6C show a nucleation layer according to one embodiment of the present invention.
  • Figures 7A-7C show schematics of devices which may be used to create a nucleation layer through a thermal gradient.
  • Figures 8A-8F shows the use of a chemical gradient according to one embodiment of the present invention.
  • Figure 9 shows a roll-to-roll system according to the present invention.
  • Figure 1OA shows a schematic of a system using a chalcogen vapor environment according to one embodiment of the present invention.
  • Figure 1OB shows a schematic of a system using a chalcogen vapor environment according to one embodiment of the present invention.
  • Figure 1OC shows a schematic of a system using a chalcogen vapor environment according to one embodiment of the present invention.
  • Figure 1 IA shows one embodiment of a system for use with rigid substrates according to one embodiment of the present invention.
  • Figure 1 IB shows one embodiment of a system for use with rigid substrates according to one embodiment of the present invention.
  • FIGs. 12-14 show the use of inter-metallic material to form a film according to embodiments of the present invention.
  • FIG. 15 is a cross-sectional view showing the use of multiple layers to form a film according to embodiments of the present invention.
  • FIG. 16 shows feedstock material being processed according to embodiments of the present invention.
  • Embodiments of the present invention take advantage of the chemistry and phase behavior of mixtures of group IB, IDA and chalcogen materials.
  • IB-IIIA-VIA compounds such as CuIn(Se, S) compounds starting from precursors containing a mixture of these elements the mixture goes through a complicated sequence of phases before forming the final compound. It is noted that for several different routes to form these IB-IIIA-VIA compounds just before forming the desired CuIn(Se,S) compound the mixture passes through one or more stages of multinary phases where the binary alloys copper chalcogenide, indium chalcogenide, gallium chalcogenide and the chalcogen are present. In addition, it is noted that a disadvantage of prior techniques is that they either tended to produce a small contact area between the chalcogen (e.g., Se or S) and the other elements or not used a separate source of chalcogen at all.
  • the chalcogen e.g., Se or S
  • the precursor material contains binary chalcogenide nanopowders, e.g., copper selenide, and/or indium selenide and/or gallium selenide and/or a source of extra chalcogen, e.g., Se or S nanoparticles less than about 200 nanometers in size.
  • binary chalcogenide nanopowders e.g., copper selenide, and/or indium selenide and/or gallium selenide and/or a source of extra chalcogen, e.g., Se or S nanoparticles less than about 200 nanometers in size.
  • a relatively low temperature e.g., 220 0 C for Se, 120° C for S
  • the chalcogen is already in a liquid state and makes good contact with the nanoparticles.
  • the nanoparticles and chalcogen are then heated sufficiently (e.g., at about 375°C) the chalcogen reacts with the chalcogenides to form the desired I
  • group IB, IDA, and VIA elements other than Cu, In, Ga, Se, and S may be included in the description of the IB-IIIA-VIA alloys described herein, and that the use of a hyphen ("-"e.g., in Cu-Se or Cu-In-Se) does not indicate a compound, but rather indicates a coexisting mixture of the elements joined by the hyphen.
  • a hyphen e.g., in Cu-Se or Cu-In-Se
  • Group IB elements suitable for use in the method of this invention include copper (Cu), silver (Ag), and gold (Au).
  • the group IB element is copper (Cu).
  • Group IDA elements suitable for use in the method of this invention include gallium (Ga), indium (In), aluminum (Al), and thallium (Tl).
  • the group IDA element is gallium (Ga) and/or indium (In).
  • Group VIA elements of interest include selenium (Se), sulfur (S), and tellurium (Te), and preferably the group VIA element is either Se and/or S.
  • the resulting group IB-IIIA-VIA compound is preferably a compound of Cu, In, Ga and selenium (Se) or sulfur S of the form CuIn ( i_ X )Ga x S 2( i- y )Se 2y , where 0 ⁇ x ⁇ 1 and 0 ⁇ y ⁇ 1.
  • the resulting group IB-IIIA-VIA compound may be a compound of Cu, In, Ga and selenium (Se) or sulfur S of the form Cu z In ( i_ X )Ga x S 2( i- y )Se 2y , where 0.5 ⁇ z ⁇ 1.5, 0 ⁇ x ⁇ 1.0 and 0 ⁇ y ⁇ 1.0.
  • An alternative way to take advantage of the low melting points of chalcogens such as Se and S is to form core-shell nanoparticles in which the core is an elemental or binary nanoparticle and the shell is a chalcogen coating.
  • the chalcogen melts and quickly reacts with the material of the core nanoparticles.
  • a film of a group IB-IIIA-chalcogenide compound is formed on a substrate 101 from binary alloy chalcogenide nanoparticles 102 and a source of extra chalcogen, e.g., in the form of a powder containing chalcogen particles 104 as shown in FIG. IA.
  • the binary alloy chalcogenide nanoparticles 102 include group IB-binary chalcogenide nanoparticles (e.g.
  • group IB non-oxide chalcogenides such as CuSe, CuS or CuTe
  • group IIIA-chalcogenide nanoparticles e.g., group IIIA non-oxide chalcogenides, such as Ga(Se, S, Te), In(Se, S, Te) and Al(Se, S, Te).
  • the binary chalcogenide nanoparticles 102 may be less than about 500 nm in size, preferably less than about 200 nm in size.
  • the chalcogen particles may be micron- or submicron-sized non-oxygen chalcogen (e.g., Se, S or Te) particles, e.g., a few hundred nanometers or less to a few microns in size.
  • the mixture of binary alloy chalcogenide nanoparticles 102 and chalcogen particles 104 is placed on the substrate 101 and heated to a temperature sufficient to melt the extra chalcogen particles 104 to form a liquid chalcogen 106 as shown in FIG. IB.
  • the liquid chalcogen 106 and binary nanoparticles 102 are heated to a temperature sufficient to react the liquid chalcogen 106 with the binary chalcogenide nanoparticles 102 to form a dense film of a group IB-IIIA- chalcogenide compound 108 as shown in FIG. 1C.
  • the dense film of group IB-IIIA- chalcogenide compound is then cooled down.
  • the binary chalcogenide particles 102 may be obtained starting from a binary chalcogenide feedstock material, e.g., micron size particles or larger. Examples of chalcogenide materials available commercially are listed in Table I below.
  • Aluminum telluride A12Te3 99.5 Copper selenide Cu-Se 99.5 Copper selenide Cu2Se 99.5 Gallium selenide Ga2Se3 99.999
  • the binary chalcogenide feedstock may be ball milled to produce particles of the desired size.
  • Binary alloy chalcogenide particles such as GaSe may alternatively be formed by pyrometallurgy.
  • InSe nanoparticles may be formed by melting In and Se together (or InSe feedstock) and spraying the melt to form droplets that solidify into nanoparticles.
  • the chalcogen particles 104 may be larger than the binary chalcogenide nanoparticles 102 since chalcogen particles 104 melt before the binary nanoparticles 102 and provide good contact with the material of the binary nanoparticles 102.
  • the chalcogen particles 104 are smaller than the thickness of the IB-IIIA-chalcogenide film 108 that is to be formed.
  • the chalcogen particles 104 may be formed in several different ways.
  • Se or S particles may be formed starting with a commercially available fine mesh powder (e.g., 200 mesh/75 micron) and ball milling the powder to a desirable size.
  • a commercially available fine mesh powder e.g. 200 mesh/75 micron
  • Examples of chalcogen powders and other feedstocks commercially available are listed in Table II below.
  • Se or S particles may alternatively be formed using an evaporation-condensation method.
  • Se or S feedstock may be melted and sprayed ("atomization") to form droplets that solidify into nanoparticles.
  • the chalcogen particles 104 may also be formed using a solution-based technique, which also is called a “Top-Down” method (Nano Letters, 2004 Vol. 4, No. 10 2047-2050 "Bottom-Up and Top-Down Approaches to Synthesis of Monodispersed Spherical Colloids of low Melting- Point Metals"-Yuliang Wang and Younan Xia).
  • This technique allows processing of elements with melting points below 400 0 C as monodispersed spherical colloids, with a diameter controllable from 100 nm to 600 nm, and in copious quantities.
  • a film of a group IB-IIIA- chalcogenide compound may be formed on a substrate 201 using core-shell nanoparticles 200 as shown in FIGs. 2A-2C.
  • Each core-shell nanoparticle 200 has a core nanoparticle covered by a coating 204.
  • the core nanoparticles 202 may be a mix of elemental particles of groups IB (e.g., Cu) and IDA (e.g., Ga and In), which may be obtained by ball milling of elemental feedstock to a desired size. Examples of elemental feedstock materials available are listed in Table III below.
  • Copper metal Cu (O 2 typ. 2-10%)
  • Copper metal Cu 99.99 Copper metal Cu 99.997 Copper metal Cu 99.99 Gallium metal Ga 99.999999 Gallium metal Ga 99.99999 Gallium metal Ga 99.9999 Gallium metal Ga 99.999 Indium metal In 99.9999 Indium metal In 99.999 Indium metal In 99.999 Indium metal In 99.99 Indium metal In 99.999 Indium metal In 99.99 Indium metal In 99.999 Indium metal In 99.99 Indium metal In 99.999 Indium metal In 99.99 Indium metal In 99.999 Indium metal In 99.99 Indium metal In 99.999 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal In 99.99 Indium metal
  • the core elemental nanoparticles 202 also may be obtained by evaporation-condensation, electro-explosion of wires and other techniques.
  • the core nanoparticles 202 may be binary nanoparticles containing group IB and/or IIIA (e.g. CuSe, GaSe and InSe) as described above with respect to FIGs. 1A-1C.
  • the core nanoparticles 202 may be ternary nanoparticles containing two different group IIIA elements (e.g. In and Ga) and a chalcogen (Se or S) or a group IB element.
  • Combinations of binary, ternary and elemental nanoparticles may also be used as the core nanoparticles 202.
  • the coating 204 on the core nanoparticle 202 contains elemental non-oxygen chalcogen material (e.g. Se or S) as a source of extra chalcogen.
  • the size of the core nanoparticles 202 is generally less than about 500 nm, preferably less than about 200 nm.
  • the core-shell nanoparticles 200 are heated to a temperature sufficient to melt the extra chalcogen coating 204 to form a liquid chalcogen 206 as shown in FIG. 2B.
  • the liquid chalcogen 206 and core nanoparticles 202 are heated to a temperature sufficient to react the liquid chalcogen 206 with the core nanoparticles 202 to form a dense film of group IB-IIIA- chalcogenide compound 208 as shown in FIG. 2C.
  • the dense film of group IB-IIIA- chalcogenide is cooled down.
  • Chalcogen shell 204 may be formed by agitating the core nanoparticles 202 into an airborne form, e.g. in an inert atmosphere of nitrogen or argon, and coating the core nanoparticles 202 by atomic layer deposition (ALD).
  • the core nanoparticles 202 may be agitated into an airborne form, e.g., by placing them on a support and ultrasonically vibrating the support.
  • ALD-based synthesis of coated nanoparticles may (optionally) use a metal organic precursor containing selenium such as dimethyl selenide, dimethyl diselenide, or diethyl diselenide or a sulfur-containing metal organic precursor, or H 2 Se or H 2 S, or other selenium- or sulfur-containing compounds, and combinations or mixtures of the above.
  • a metal organic precursor containing selenium such as dimethyl selenide, dimethyl diselenide, or diethyl diselenide or a sulfur-containing metal organic precursor, or H 2 Se or H 2 S, or other selenium- or sulfur-containing compounds, and combinations or mixtures of the above.
  • the coating 204 may be formed by agitating the core nanoparticles 202 into an airborne form, e.g. in an inert atmosphere of nitrogen or argon, and exposing the airborne core nanoparticles to a vaporized chalcogen Se or S.
  • Binary chalcogenide particles and extra chalcogen as described above with respect to FIG. IA or core-shell nanoparticles as described above with respect to FIG. 2A may be mixed with solvents and other components to form an ink for solution deposition onto a substrate.
  • the flow diagram of FIG. 3 illustrates a method 300 for forming a IB-IIIA-chalcogenide layer using inks formed from nanoparticle-based precursors. The method begins at step 302 by mixing the nanoparticles, e.g., binary chalcogenide particles and source of extra chalcogen, core-shell nanoparticles or some combination of both.
  • a dispersion e.g., an ink, paint or paste
  • an ink may be formed by dispersing the nanoparticles in a dispersant (e.g., a surfactant or polymer) along with (optionally) some combination of other components commonly used in making inks.
  • Solvents can be aqueous (water-based) or non-aqueous (organic).
  • Other components include, without limitation, binders, emulsifiers, anti-foaming agents, dryers, solvents, fillers, extenders, thickening agents, film conditioners, anti-oxidants, flow and leveling agents, plasticizers and preservatives.
  • nanoparticulate dispersion can be added in various combinations to improve the film quality and optimize the coating properties of the nanoparticulate dispersion.
  • An alternative method to mixing nanoparticles and subsequently preparing a dispersion from these mixed nanoparticles would be to prepare separate dispersions for each individual type of nanoparticle and subsequently mixing these dispersions.
  • a thin precursor film of the dispersion is then formed on a substrate by any of a variety of solution-based coating techniques including but not limited to wet coating, spray coating, spin coating, doctor blade coating, contact printing, top feed reverse printing, bottom feed reverse printing, nozzle feed reverse printing, gravure printing, microgravure printing, reverse microgravure printing, comma direct printing, roller coating, slot die coating, meyerbar coating, lip direct coating, dual lip direct coating, capillary coating, ink-jet printing, jet deposition, spray deposition, and the like.
  • solution-based coating techniques including but not limited to wet coating, spray coating, spin coating, doctor blade coating, contact printing, top feed reverse printing, bottom feed reverse printing, nozzle feed reverse printing, gravure printing, microgravure printing, reverse microgravure printing, comma direct printing, roller coating, slot die coating, meyerbar coating, lip direct coating, dual lip direct coating, capillary coating, ink-jet printing, jet deposition, spray deposition, and the like.
  • the use of these and related coating and/or printing techniques in the non-vacuum based deposition of an ink, paste, or paint is not limited to ink, paste, and/or paints formed from nanoparticulates derived by the methods described above, but also using nanoparticles formed through a wide variety of other nanoparticles synthesis techniques, including but not limited to those described, e.g., in Published PCT Application WO 2002/084708 or commonly assigned US Patent Application 10/782,017.
  • the substrate may be an aluminum foil substrate or a polymer substrate, which is a flexible substrate in a roll-to-roll manner (either continuous or segmented or batch) using a commercially available web coating system. Aluminum foil is preferred since it is readily available and inexpensive.
  • the extra chalcogen e.g., micron- or sub-micron-sized chalcogen powder is mixed into the dispersion containing the metal chalcogenides (in binary selenide or core-shell form) so that the nanoparticles and extra chalcogen are deposited at the same time.
  • the chalcogen powder may be deposited on the substrate in a separate solution- based coating step before or after depositing the dispersion containing the metal chalcogenides.
  • the dispersion may include additional group IIIA elements, e.g., gallium in metallic form, e.g., as nanoparticles and/or nanoglobules and/or nanodroplets.
  • the thin precursor film is heated to a temperature sufficient to melt the chalcogen source.
  • the dispersion is further heated to react the chalcogen with other components.
  • the temperature is preferably between 375°C (temperature for reaction) and 500 0 C (a safe temperature range for processing on aluminum foil or high-melting-temperature polymer substrates).
  • the at least partially molten thin film and substrate are cooled down.
  • step 306 may be performed by sequentially depositing nanoparticulate dispersions having different compositions of IB-, IIIA- and chalcogen-based particulates in two or more steps. For example would be to first deposit a dispersion containing an indium selenide nanopowder (e.g. with an In-to-Se ratio of ⁇ 1), and subsequently deposit a dispersion of a copper selenide nanopowder (e.g. with a Cu-to-Se ratio of ⁇ 1) and a gallium selenide nanopowder (e.g.
  • an indium selenide nanopowder e.g. with an In-to-Se ratio of ⁇ 1
  • a dispersion of a copper selenide nanopowder e.g. with a Cu-to-Se ratio of ⁇ 1
  • a gallium selenide nanopowder e.g.
  • a layer of In x Ga y Se z with x > 0 (larger than or equal to zero), y > 0 (larger than or equal to zero), and z > 0 (larger than or equal to zero) may be formed as described above on top of a uniform, dense layer of Cu w In x Ga y with w > 0 (larger than or equal to zero), x > 0 (larger than or equal to zero), and y > 0 (larger than or equal to zero), and subsequently converting (sintering) the two layers into CIGS.
  • a layer of Cu w In x Ga y may be formed on top of a uniform, dense layer of In x Ga y Se z and subsequently converting (sintering) the two layers into CIGS.
  • nanoparticulate-based dispersions as described above may further include elemental IB, and/or IIIA nanoparticles (e.g., in metallic form).
  • elemental IB, and/or IIIA nanoparticles e.g., in metallic form.
  • Cu x In y Ga z Se u nanopowders with u > 0 (larger than zero), with x > 0 (larger than or equal to zero), y > 0 (larger than or equal to zero), and z > 0 (larger than or equal to zero), may be combined with an additional source of selenium (or other chalcogen) and metallic gallium into a dispersion that is formed into a film on the substrate and sintered.
  • Metallic gallium nanoparticles and/or nanoglobules and/or nanodroplets may be formed, e.g., by initially creating an emulsion of liquid gallium in a solution.
  • Gallium metal or gallium metal in a solvent with or without emulsifier may be heated to liquefy the metal, which is then sonicated and/or otherwise mechanically agitated in the presence of a solvent.
  • Agitation may be carried out either mechanically, electromagnetically, or acoustically in the presence of a solvent with or without a surfactant, dispersant, and/or emulsifier.
  • the gallium nanoglobules and/or nanodroplets can then be manipulated in the form of a solid-particulate, by quenching in an environment either at or below room temperature to convert the liquid gallium nanoglobules into solid gallium nanoparticles.
  • This technique is described in detail in commonly-assigned US Patent Application 11/081,163 to Matthew R. Robinson and Martin R. Roscheisen entitled “Metallic Dispersion", the entire disclosures of which are incorporated herein by reference.
  • the method 300 may be optimized by using, prior to, during, or after the solution deposition and/or sintering of one or more of the precursor layers, any combination of (1) any chalcogen source that can be solution-deposited, e.g. a Se or S nanopowder mixed into the precursor layers or deposited as a separate layer, (2) chalcogen (e.g., Se or S) evaporation, (3) an H 2 Se (H 2 S) atmosphere, (4) a chalcogen (e.g., Se or S) atmosphere, (5), an organo-selenium containing atmosphere, e.g. diethylselenide (6) an H 2 atmosphere, (7) another reducing atmosphere, e.g. CO, (8) a wet chemical reduction step, and a (9) heat treatment.
  • any chalcogen source that can be solution-deposited, e.g. a Se or S nanopowder mixed into the precursor layers or deposited as a separate layer
  • chalcogen e.g.,
  • FIG. 4 depicts an example of a photovoltaic cell 400 that uses a combination of a IB-IIIA-chalcogenide film as components of an absorber layer.
  • the cell 400 generally includes a substrate or base layer 402, an optional adhesion and/or barrier layer 403, a base electrode 404, a IB-IIIA-chalcogenide absorber layer 406, a window layer 408, and a transparent electrode 410.
  • the base layer 402 may be made from a thin flexible material suitable for roll-to-roll processing.
  • the base layer may be made of a metal foil, such as titanium, aluminum, stainless steel, molybdenum, or a plastic or polymer, such as polyimides (PI), polyamides, polyetheretherketone (PEEK), Polyethersulfone (PES), polyetherimide (PEI), polyethylene naphtalate (PEN), Polyester (e.g. PET), or a metallized plastic.
  • the base electrode 404 is made of an electrically conductive material.
  • the base electrode 404 may be a layer of Al foil, e.g., about 10 microns to about 100 microns thick.
  • An optional intermediate layer 403 may be incorporated between the electrode 404 and the substrate 402.
  • the layer 403 may be a diffusion barrier layer to prevent diffusion of material between the substrate 402 and the electrode 404.
  • the diffusion barrier layer 403 may be a conductive layer or it may be an electrically nonconductive layer.
  • the layer 403 may be composed of any of a variety of materials, including but not limited to 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. In some embodiments, the layer may be from 100 nm to 300 nm. Optionally, the thickness may be in the range of about 150 nm to about 250 nm. Optionally, the thickness may be about 200 nm. In some embodiments, two barrier layers may be used, one on each side of the substrate 402.
  • an interfacial layer may be located above the electrode 404 and be comprised of a material such as including but not limited to 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.
  • a material such as including but not limited to 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 IB-IIIA-chalcogenide absorber layer 406 may be about 0.5 micron to about 5 microns thick after annealing, more preferably from about 0.5 microns to about 2 microns thick after annealing.
  • the window layer 408 is typically used as a junction partner for the IB-IIIA-chalcogenide absorber layer 406.
  • the window layer may include cadmium sulfide (CdS), zinc sulfide (ZnS), or zinc selenide (ZnSe), or n-type organic materials (e.g. polymers or small molecules), or some combination of two or more of these or similar materials. Layers of these materials may be deposited, e.g., by chemical bath deposition, to a thickness of about 1 nm to about 500 nm.
  • the transparent electrode 410 may include a transparent conductive organic (polymeric or a mixed polymeric-molecular), or a hybrid (organic-inorganic) layer 409, e.g. a transparent layer of doped PEDOT (Poly-3,4-Ethylenedioxythiophene), which can be deposited using spin, dip, or spray coating, and the like.
  • PEDOT Poly-3,4-Ethylenedioxythiophene
  • PSS:PEDOT is a doped conducting polymer based on a heterocyclic thiophene ring bridged by a diether.
  • a water dispersion of PEDOT doped with poly(styrenesulfonate) (PSS) is available from H.C. Starck of Newton, Massachussetts under the trade name of Baytron ® P.
  • Baytron ® is a registered trademark of Bayer Aktiengesellschaft (hereinafter Bayer) of Leverkusen, Germany.
  • PSS:PEDOT can be used as a planarizing layer, which can improve device performance.
  • a potential disadvantage in the use of PEDOT is the acidic character of typical coatings, which may serve as a source through which the PEDOT chemically may attack, react with, or otherwise degrade the other materials in the solar cell. Removal of acidic components in PEDOT can be carried out by anion exchange procedures.
  • Non-acidic PEDOT can be purchased commercially. Alternatively, similar materials can be purchased from TDA materials of Wheat Ridge, Colorado, e.g. OligotronTM and AedotronTM.
  • the transparent electrode 410 may further include a layer of metal (e.g., Ni, Al or Ag) fingers 411 to reduce the overall sheet resistance.
  • An optional encapsulant layer (not shown) provides environmental resistance, e.g., protection against exposure to water or air.
  • the encapsulant may also absorb UV-light to protect the underlying layers.
  • suitable encapsulant materials include one or more layers of polymers such as THZ, Tefzel® (DuPont), tefdel, thermoplastics, polyimides (PI), polyamides, polyetheretherketone (PEEK), Polyethersulfone (PES), polyetherimide (PEI), polyethylene naphtalate (PEN), Polyester (PET), nanolaminate composites of plastics and glasses (e.g. barrier films such as those described in commonly-assigned, co-pending U.S.
  • the purpose of providing an extra source of chalcogen is to first create liquid to enlarge the contact area between the initial solid particles and the liquid. Secondly, when working with chalcogen-poor films, the extra source adds chalcogen to get to the stoichiometric desired chalcogen amount. Third, chalcogens such as Se are volatile and inevitably some of the chalcogen is lost during processing. So, the main purpose is to create liquid. There are also a variety of other routes to increase the amount of liquid when the precursor layer is processed.
  • These routes include but are not limited to: 1) Cu-Se more Se-rich than Cu2-xSe (>377C, even more liquid above >523C); 2) Cu-Se equal to or more Se-rich than Cu2Se when adding additional Se (>220C); 3) In-Se of composition In4Se3, or in between In4Se3 and InI SeI (> 550C); 4) In-Se equal to or more Se-rich than In4Se3 when adding additional Se (>220C); 5) In- Se in between In and In4Se3 (>156C, preferably in an oxygen-free environment since In is created 6) Ga-emulsion (>29C, preferably oxygen-free); and hardly (but possible) for Ga-Se.
  • the extra source of chalcogen is not limited to only elemental chalcogen, but in some embodiments, may be an alloy and/or solution of one or more chalcogens.
  • the extra source of chalcogen may be mixed with and/or deposited within the precursor layer, instead of as a discrete layer.
  • oxygen-free particles or substantially oxygen free particles of chalcogen could be used. If the chalcogen is used with flakes and/or plate shaped precursor materials, densification might not end up an issue due to the higher density achieved by using planar particles, so there is no reason to exclude printing Se and/or other source of chalcogen within the precursor layer as opposed to a discrete layer. Flakes may include both microflakes and/or nanoflakes.
  • multiple layers of material may be printed and reacted with chalcogen before deposition of the next layer.
  • One nonlimiting example would be to deposit a Cu-In-Ga layer, anneal it, then deposit an Se layer then treat that with RTA, follow that up by depositing another precursor layer rich in Ga, followed by another deposition of Se, and finished by a second RTA treatment.
  • this may include forming a precursor layer (either heat or not) then coating a layer of the extra source of chalcogen (then heat or not) then form another layer of more precursor (heat or not) and then for another layer of the extra source of chalcogen (then heat or not) and repeat as many times as desired to grade the composition or nucleating desired crystal sizes.
  • this may be used to grade the gallium concentration.
  • this may be used to grade the copper concentration.
  • this may be used to grade the indium concentration.
  • this may be used to grade the selenium concentration.
  • this may be used to grade the selenium concentration.
  • this embodiment can combined to allow the chalcogen to be deposited in the precursor layer for any of the steps involved.
  • the ink may contain multiple types of particles.
  • the particles 504 are a first type of particle and the particles 506 are a second type of particle.
  • the ink may have multiple types of particles wherein only one type of particle is a chalcogenide and is also chalcogen-rich.
  • the ink may have particles wherein at least two types of chalcogenides in the ink are chalcogen-rich.
  • the ink may have Cu x Se y (wherein x ⁇ y) and In a Seb (wherein a ⁇ b).
  • the ink may have particles 504, 506, and 508 (shown in phantom) wherein at least three types of chalcogenide particles are in the ink.
  • the chalcogen-rich chalcogenide particles may be Cu-Se, In-Se, and/or Ga-Se. All three may be chalcogen-rich. A variety of combinations are possible to obtain the desired excess amount of chalcogen. If the ink has three types of particles, it should be understood that not all of the particles need to be chalcogenides or chalcogen rich. Even within an ink with only one type of particle, e.g.
  • Cu-Se there may be a mixture of chalcogen-rich particles, e.g. Cu x Se y with x ⁇ y, and non-chalcogen-rich particles, e.g. Cu x Se y with x > y.
  • a mixture may contain particles of copper selenide that may have the following compositions: CuiSei and CuiSe 2 .
  • an additional layer 510 may be also printed or coated on to the ink to provide an excess source of chalcogen as described previously.
  • the material in this layer may be a pure chalcogen, a chalcogenide, or a compound that contains chalcogen.
  • the additional layer 510 (shown in phantom) may also be printed onto the resulting film if further processing with chalcogen is desired.
  • heat may be applied to the particles 504 and 506 to begin converting them. Due to the various melting temperatures of the materials in the particles, some may start to assume a liquid form sooner than others. In the present invention, this is particularly advantageous if the materials assuming liquid form also release the excess chalcogen as a liquid 512 which may surround the other materials and/or elements such as 514 and 516 in the layer.
  • Figure 1OB includes a view with an enlarged view of the liquid 512 and materials and/or elements 514 and 516.
  • the excess amount of chalcogen comprises an amount greater than the sum of 1) a stoichiometric amount found in the final IB-IIIA-chalcogenide film and 2) a minimum amount of chalcogen necessary to account for losses during processing to form the final IB-IIIA-chalcogenide having the desired stoichiometric ratio.
  • the excess chalcogen may act as a flux that will liquefy at the processing temperature and promote greater atomic intermixing of particles provided by the liquefied excess chalcogen.
  • the liquefied excess chalcogen may also ensure that sufficient chalcogen is present to react with the group IB and IDA elements.
  • the excess chalcogen helps to "digest” or “solubilize” the particles and/or flakes.
  • the excess chalcogen will escape from the layer before the desired film is fully formed.
  • heat may continue to be applied until the group IB-IIIA chalcogenide film 520 is formed.
  • Another layer 522 (shown in phantom) may be applied for further processing of the film 520 if particular features are desired.
  • an extra source of gallium may be added to the top layer and further reacted with the film 520.
  • Others sources may provide additional selenium to improve selenization at the top surface of the film 520.
  • chalcogenide particles may also be combined with non-chalcogenide particles to arrive at the desired excess supply of chalcogen in the precursor layer.
  • Table IV provides a non-limiting matrix of some of the possible combinations between chalcogenide particles listed in the rows and the non- chalcogenide particles listed in the columns.
  • the present invention may combine a variety of chalcogenide particles with other chalcogenide particles.
  • Table V provides a nonlimiting matrix of some of the possible combinations between chalcogenide particles listed for the rows and chalcogenide particles listed for the columns.
  • This embodiment provides a method for improving crystal growth on the substrate by depositing a thin IB-IIIA chalcogenide layer on the substrate to serve as a nucleation plane for film growth for the precursor layer which is formed on top of the thin group IB-IIIA chalcogenide layer.
  • This nucleation layer of a group IB-IIIA chalcogenide may be deposited, coated, or formed prior to forming the precursor layer.
  • the nucleation layer may be formed using vacuum or non-vacuum techniques.
  • the precursor layer formed on top of the nucleation layer may be formed by a variety of techniques including but not limited to using an ink containing a plurality of flakes or particles as described in this application.
  • the nucleation layer may be viewed as being a layer where an initial IB-IIIA-VIA compound crystal growth is preferred over crystal growth in another location of the precursor layer and/or stacks of precursor layers.
  • a nucleation layer 816 is formed on the substrate 812.
  • This nucleation layer may comprise of a group IB-IIIA chalcogenide and may be deposited, coated, or formed prior to forming the precursor layer.
  • this may be a CIGS layer, a Ga-Se layer, any other high-melting IB-IIIA-chalcogenide layer, or even a thin layer of gallium.
  • FIG. 6C it should also be understood that the structure of the alternating nucleation layer and precursor layer may be repeated in the stack.
  • Figure 6C show that, optionally, another nucleation layer 820 (shown in phantom) may be formed over the precursor layer 818 to continue the structure of alternating nucleation layer and precursor layer.
  • Another precursor layer 822 may then be formed over the nucleation layer 820 to continue the layering, which may be repeated as desired.
  • the each set may have different materials or amounts of materials as compared to other sets in the stack.
  • the alternating layers may be solution deposited, vacuum deposited or the like.
  • Different layers may be deposited by different techniques. In one embodiment, this may involve solution depositing (or vacuum depositing) a precursor layer (optionally with a desired Cu-to-In-to-Ga ratio), subsequently adding chalcogen (solution-based, vacuum-based, or otherwise such as but not limited to vapor or H2Se, ec...), optionally heat treating this stack (during or after introduction of the chalcogen source), subsequently depositing an additional precursor layer (optionally with a desired Cu-to-In-to-Ga ratio), and finally heat treating the final stack (during or after the introduction of additional chalcogen).
  • the goal is to create planar nucleation so that there are no holes or areas where the substrate will not be covered by subsequent film formation and/or crystal growth.
  • the chalcogen source may also be introduced before adding the first precursor layer containing Cu+In+Ga.
  • a nucleation layer for use with a particle or flake based precursor material, or any other precursor material may also be formed by creating a thermal gradient in the precursor layer 850.
  • the nucleation layer 852 may be formed at the upper portion of the precursor layer or optionally by forming the nucleation layer 854 at a lower portion of the precursor layer.
  • the nucleation layer 852 or 854 is formed by creating a thermal gradient in the precursor layer such that one portion of the layer reaches a temperature sufficient to begin crystal growth.
  • the nucleation layer may be in the form of a nucleation plane having a substantially planar configuration to promote a more even crystal growth across the substrate while minimizing the formation of pinholes and other anomalies.
  • the thermal gradient used to form the nucleation layer 852 may be created by using a laser 856 to increase only an upper portion of the precursor layer 850 to a processing temperature.
  • the laser 856 may be pulsed or otherwise controlled to not heat the entire thickness of the precursor layer to a processing temperature.
  • the backside 858 of the precursor layer and the substrate 860 supporting it may be in contact with cooled rollers 862, cooled planar contact surface, or cooled drums which provide an external source of cooling to prevent lower portions of the layer from reaching processing temperature.
  • Cooled gas 864 may also be provided on one side of the substrate and adjacent portion of the precursor layer to lower the temperature of the precursor layer below a processing temperature where nucleation to the final IB-IIIA-chalcogenide compound begins. It should be understood that other devices may be used to heat the upper portion of the precursor layer such as but not limited to pulsed thermal processing, plasma heating, or heating via IR lamps.
  • pulsed thermal processing remains generally promising, certain implementations of the pulsed thermal processing such as a directed plasma arc system, face numerous challenges.
  • a directed plasma arc system sufficient to provide pulsed thermal processing is an inherently cumbersome system with high operational costs.
  • the direct plasma arc system requires power at a level that makes the entire system energetically expensive and adds significant cost to the manufacturing process.
  • the directed plasma arc also exhibits long lag time between pulses and thus makes the system difficult to mate and synchronize with a continuous, roll-to-roll system. The time it takes for such a system to recharge between pulses also creates a very slow system or one that uses more than directed plasma arc, which rapidly increase system costs.
  • other devices suitable for rapid thermal processing may be used and they include pulsed layers used in adiabatic mode for annealing (Shtyrokov E I, 5Ov. Phys. - Semicond. 9 1309), continuous wave lasers (10-30W typically) (Ferris S D 1979 Laser-Solid Interactions and Laser Processing (New York: AIP)), pulsed electron beam devices (Kamins T I 1979 Appl. Phys. Leti. 35 282-5), scanning electron beam systems (McMahon R A 1979 J. Vac. ScL Techno. 16 1840-2) (Regolini J L 1979 Appl. Phys. Lett. 34 410), other beam systems (Hodgson R T 1980 Appl.
  • Patents 3,950,187 Metal and apparatus involving pulsed electron beam processing of semiconductor devices
  • 4,082,958 Apparatus involving pulsed electron beam processing of semiconductor devices
  • U.S. Patents 4,729,962 also describes another known method for rapid thermal processing of solar cells. The above may be applied singly or in single or multiple combinations with other similar processing techniques with various embodiments of the present invention.
  • the nucleation layer 854 may be formed on a lower portion of the precursor layer 850 using techniques similar to those described above. Since the substrate 860 used with the present invention may be selected to be thermally conductive, underside heating of the substrate will also cause heating of a lower portion of the precursor layer. The nucleation plane will then form along the bottom portion of the lower portion.
  • the upper portion of the precursor layer may be cooled by a variety of techniques such as, but not limited to, cooled gas, cooled rollers, or other cooling device.
  • the entire precursor layer preferably consisting of material identical or close to the final IB-IIIA-chalcogenide compound
  • the entire precursor layer or optionally only those portions of the precursor layer that remain more or less unprocessed, will be heated to the processing temperature so that the remaining material will begin to convert into the final IB- IIIA-chalcogenide compound in contact with the nucleation layer.
  • the nucleation layer guides the crystal formation and minimizes the possibility of areas of the substrate forming pinhole or having other abnormalities due to uneven crystal formation.
  • the temperature may also vary over different time periods of precursor layer processing.
  • the heating may occur at a first temperature over an initial processing time period and proceed to other temperatures for subsequent time periods of the processing.
  • the method may include intentionally creating one or more temperature dips so that, as a nonlimiting example, the method comprises heating, cooling, heating, and subsequent cooling.
  • the composition of the deposited layers of precursor material may be selected so that crystal formation begins sooner in some layers than in other layers.
  • the various methods of forming a nucleation layer may be combined together to facilitate layer formation.
  • the thermal gradient and chemical gradient methods may be combined to facilitate nucleation layer formation. It is imagined that single or multiple combinations of using a thermal gradient, chemical gradient, and/or thin film nucleation layer may be combined.
  • the absorber layer may be formed on a substrate 912, as shown in Figure 8A.
  • a surface of the substrate 912 may be coated with a contact layer 914 to promote electrical contact between the substrate 912 and the absorber layer that is to be formed on it.
  • an aluminum substrate 912 may be coated with a contact layer 914 of molybdenum.
  • forming or disposing a material or layer of material on the substrate 912 includes disposing or forming such material or layer on the contact layer 914, if one is used.
  • a layer 915 may also be formed on top of contact layer 914 and/or directly on substrate 912.
  • This layer may be solution coated, evaporated, and/or deposited using vacuum based techniques.
  • the layer 915 may have a thickness less than that of the precursor layer 916. In one nonlimiting example, the layer may be between about 1 to about 100 nm in thickness.
  • the layer 915 may be comprised of various materials including but not limited to at least one of the following: a group IB element, a group IIIA element, a group VIA element, a group IA element (new style: group 1), a binary and/or multinary alloy of any of the preceding elements, a solid solution of any of the preceding elements, copper, indium, gallium, selenium, copper indium, copper gallium, indium gallium, sodium, a sodium compound, sodium fluoride, sodium indium sulfide, copper selenide, copper sulfide, indium selenide, indium sulfide, gallium selenide, gallium sulfide, copper indium selenide, copper indium sulfide, copper gallium selenide, copper gallium selenide, copper gallium sulfide, indium gallium selenide, indium gallium sulfide, copper indium gallium selenide, and/or copper indium gallium sulfide.
  • a precursor layer 916 is formed on the substrate.
  • the precursor layer 916 contains one or more group IB elements and one or more group IIIA elements.
  • the one or more group IB elements include copper.
  • the one or more group IIIA elements may include indium and/or gallium.
  • the precursor layer may be formed using any of the techniques described above.
  • the precursor layer contains no oxygen other than those unavoidably present as impurities or incidentally present in components of the film other than the particles or microflakes themselves.
  • the precursor layer 916 is preferably formed using non-vacuum methods, it should be understood that it may optionally be formed by other means, such as evaporation, sputtering, ALD, etc.
  • the precursor layer 916 may be an oxygen- free compound containing copper, indium and gallium.
  • the non-vacuum system operates at pressures above about 3.2 kPa (24 Torr).
  • a layer 917 may also be formed on top of precursor layer 916. It should be understood that the stack may have both layers 915 and 917, only one of the layers, or none of the layers.
  • the layer 917 may have a thickness less than that of the precursor layer 916. In one nonlimiting example, the layer may be between about 1 to about 100 nm in thickness.
  • the layer 917 may be comprised of various materials including but not limited to at least one of the following: a group IB element, a group IIIA element, a group VIA element, a group IA element (new style: group 1), a binary and/or multinary alloy of any of the preceding elements, a solid solution of any of the preceding elements, copper, indium, gallium, selenium, copper indium, copper gallium, indium gallium, sodium, a sodium compound, sodium fluoride, sodium indium sulfide, copper selenide, copper sulfide, indium selenide, indium sulfide, gallium selenide, gallium sulfide, copper indium selenide, copper indium sulfide, copper gallium selenide, copper gallium selenide, copper gallium sulfide, indium gallium selenide, indium gallium sulfide, copper indium gallium selenide, and/or copper indium gallium sulfide.
  • a second precursor layer 918 of a second precursor material may optionally be applied on top of the first precursor layer.
  • the second precursor material may have an overall composition that is more chalcogen-rich than the first precursor material in precursor layer 916.
  • this allows for creating a gradient of available Se by doing two coatings (preferably with only one heating process of the stack after depositing both precursor layer coatings) where the first coating contains selenides with relatively less selenium in it (but still enough) than the second.
  • the precursor for the first coating can contain Cu x Se y where the x is larger than in the second coating.
  • each layer may contain a mix of Cu x Se y particles wherein there is a larger concentration (by weight) of the selenide particles with the large x.
  • each layer has preferably the targeted stoichiometry because the C/I/G ratios are kept the same for each precursor layer.
  • this second precursor layer 918 is preferably formed using non-vacuum methods, it should be understood that it may optionally be formed by other means, such as evaporation, sputtering, ALD, etc...
  • chalcogen grading or more general a grading in melting temperature from bottom to top, is to control the relative rate of crystallization in depth and to have the crystallization happen e.g. faster at the bottom portion of the stack of precursor layers than at the top of the stack of precursor layers.
  • the additional rationale is that the common grain structure in typical efficient solution-deposited CIGS cells where the cells have large grains at the top of the photoactive film, which is the part of the photoactive film that is mainly photoactive, and small grains at the back, still have appreciable power conversion efficiencies.
  • a plurality of many layers of different precursor materials may be used to build up a desired gradient of chalcogen, or more general, a desired gradient in melting temperature and/or subsequent solidification into the final IB-IIIA- chalcogenide compound, or even more general, a desired gradient in melting and/or subsequent solidification into the final IB-IIIA-chalcogenide compound, either due to creating a chemical (compositional) gradient, and/or a thermal gradient, in the resulting film.
  • the present invention may use particles with different melting points such as but not limited to lower melting materials Se, IruSes, Ga, and CuiSei, compared to higher melting materials In 2 Se3, Cu 2 Se.
  • heat 920 is applied to sinter the first precursor layer 916 and the second precursor layer 918 into a IB-IIIA-chalcogenide compound film 922.
  • the heat 920 may be supplied in a rapid thermal annealing process, e.g., as described above.
  • the substrate 912 and precursor layer(s) 916 and/or 918 may be heated from an ambient temperature to a plateau temperature range of between about 200 0 C and about 600 0 C.
  • Processing comprises annealing with a ramp-rate of l-5°C/sec, preferably over 5°C/sec, to a temperature of about 200 0 C and about 600 0 C.
  • processing further comprise selenizing this annealed layer with a ramp-rate of 1- 5°C/sec, preferably over 5°C/sec, to a temperature of about 225 to 575°C for a time period of about 60 seconds to about 10 minutes in Se vapor, where the plateau temperature is not necessarily kept constant in time, to form the thin-film containing one or more chalcogenide compounds containing Cu, In, Ga, and Se.
  • processing comprises selenizing without the separate annealing step in an atmosphere containing hydrogen gas, but may be densified and selenized in one step with a ramp-rate of 1-5 C/sec, preferably over 5°C/sec, to a temperature of 225 to 575°C for a time period of about 120 seconds to about 20 minutes in an atmosphere containing either H 2 Se or a mixture Of H 2 and Se vapor.
  • the annealing temperature could be modulated to oscillate within a temperature range without being maintained at a particular plateau temperature.
  • This technique (referred to herein as rapid thermal annealing or RTA) is particularly suitable for forming photovoltaic active layers (sometimes called "absorber" layers) on metal foil substrates, such as but not limited to aluminum foil.
  • suitable substrates include but are not limited to other metals such as Stainless Steel, Copper, Titanium, or Molybdenum, metallized plastic foils, glass, ceramic films, and mixtures, alloys, and blends of these and similar or related materials.
  • the substrate may be flexible, such as the form of a foil, or rigid, such as the form of a plate, or combinations of these forms. Additional details of this technique are described in US Patent Application 10/943,685, which is incorporated herein by reference.
  • a layer 924 containing elemental chalcogen particles may be applied over the precursor layers 916 and/or 918 prior to heating.
  • the layer 924 is formed over the precursor layer 916.
  • the chalcogen particles may be particles of selenium, sulfur or tellurium. Such particles may be fabricated as described above.
  • the chalcogen particles in the layer 924 may be between about 1 nanometer and about 25 microns in size, preferably between 50 nm and 500 nm
  • the chalcogen particles may be mixed with solvents, carriers, dispersants etc.
  • the chalcogen particles may be prepared for deposition on a substrate through dry processes to form the layer 924.
  • a layer 926 containing an additional chalcogen source, and/or an atmosphere containing a chalcogen source may optionally be applied to layer 922, particularly if layer 924 was not applied in Figure 8D.
  • Heat 928 may optionally be applied to layer 922 and the layer 926 and/or atmosphere containing the chalcogen source to heat them to a temperature sufficient to melt the chalcogen source and to react the chalcogen source with the group IB element and group IIIA elements in the precursor layer 922.
  • the heat 928 may be applied in a rapid thermal annealing process, e.g., as described above.
  • the reaction of the chalcogen source with the group IB and IIIA elements forms a compound film 930 of a group IB-IIIA-chalcogenide compound as shown in FIG. 8D
  • the group IB-IIIA- chalcogenide compound is of the form Cu z Ini_ x Ga x Se2(i- y )S2 y , where O ⁇ x ⁇ l, O ⁇ y ⁇ l, and 0.5 ⁇ y ⁇ 1.5.
  • sodium may also be used with the precursor material to improve the qualities of the resulting film.
  • a sodium containing material may be formed above and/or below the precursor layer 916.
  • the formation may occur by solution coating and/or other techniques such as but not limited to sputtering, evaporation, CBD, electroplating, sol-gel based coating, spray coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), and the like.
  • sodium may also be introduced into the stack by sodium doping the microflakes and/or particles in the precursor layer 916.
  • the microflakes and/or other particles in the precursor layer 916 may be a sodium containing material such as, but not limited to, Cu-Na, In-Na, Ga-Na, Cu-In-Na, Cu-Ga-Na, In-Ga-Na, Na- Se, Cu-Se-Na, In-Se-Na, Ga-Se-Na, Cu-In-Se-Na, Cu-Ga-Se-Na, In-Ga-Se-Na, Cu-In-Ga-Se-Na, Na-S, Cu-S-Na, In-S-Na, Ga-S-Na, Cu-In-S-Na, Cu-Ga-S-Na, In-Ga-S-Na, and/or Cu-In-Ga-S- Na.
  • the amount of sodium in the microflakes and/or other particles may be about 1 at.% or less. In another embodiment, the amount of sodium may be about 0.5 at.% or less. In yet another embodiment, the amount of sodium may be about 0.1 at.% or less. It should be understood that the doped particles and/or flakes may be made by a variety of methods including milling feedstock material with the sodium containing material and/or elemental sodium.
  • sodium may be incorporated into the ink itself, regardless of the type of particle, nanoparticle, microflake, and/or nanoflakes dispersed in the ink.
  • the ink may include microflakes (Na doped or undoped) and a sodium compound with an organic counter-ion (such as but not limited to sodium acetate) and/or a sodium compound with an inorganic counter-ion (such as but not limited to sodium sulfide).
  • an organic counter-ion such as but not limited to sodium acetate
  • sodium compound with an inorganic counter-ion such as but not limited to sodium sulfide
  • sodium compounds added into the ink might be present as particles (e.g. nanoparticles), or dissolved.
  • the sodium may be in "aggregate" form of the sodium compound (e.g. dispersed particles), and the "molecularly dissolved” form.
  • None of the three aforementioned methods are mutually exclusive and may be applied singly or in any single or multiple combination to provide the desired amount of sodium to the stack containing the precursor material. Additionally, sodium and/or a sodium containing compound may also be added to the substrate (e.g. into the molybdenum target). Also, sodium- containing layers may be formed in between one or more precursor layers if multiple precursor layers (using the same or different materials) are used. It should also be understood that the source of the sodium is not limited to those materials previously listed.
  • any deprotonated alcohol where the proton is replaced by sodium any deprotonated organic and inorganic acid, the sodium salt of the (deprotonated) acid, sodium hydroxide, sodium acetate, and the sodium salts of the following acids: butanoic acid, hexanoic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, 9- hexadecenoic acid, octadecanoic acid, 9-octadecanoic acid, 11-octadecenoic acid, 9,12- octadecadienoic acid, 9,12,15-octadecatrienoic acid, and/or 6,9,12-octadecatrienoic acid.
  • sodium and/or a sodium compound may be added to the processed chalcogenide film after the precursor layer has been sintered or otherwise processed.
  • This embodiment of the present invention thus modifies the film after CIGS formation. With sodium, carrier trap levels associated with the grain boundaries are reduced, permitting improved electronic properties in the film.
  • a variety of sodium containing materials such as those listed above may be deposited as layer 932 onto the processed film and then annealed to treat the CIGS film.
  • the sodium material may be combined with other elements that can provide a bandgap widening effect. Two elements which would achieve this include gallium and sulfur. The use of one or more of these elements, in addition to sodium, may further improve the quality of the absorber layer.
  • a sodium compound such as but not limited to Na 2 S, NaInS 2 , or the like provides both Na and S to the film and could be driven in with an anneal such as but not limited to an RTA step to provide a layer with a bandgap different from the bandgap of the unmodified CIGS layer or film.
  • a flexible substrate 1001 e.g., aluminum foil travels from a supply roll 1002 to a take-up roll 1004.
  • the substrate 1001 passes a number of applicators 1006A, 1006B, 1006C, e.g. microgravure rollers and heater units 1008A, 1008B, 1008C.
  • Each applicator deposits a different layer or sub-layer of a photovoltaic device active layer, e.g., as described above.
  • the heater units are used to anneal the different sub-layers.
  • applicators 1006A and 1006B may applied different sub-layers of a precursor layer (such as precursor layer 106, precursor layer 916, or precursor layer 918). Heater units 1008A and 1008B may anneal each sub-layer before the next sub-layer is deposited. Alternatively, both sub-layers may be annealed at the same time. Applicator 1006C may apply a layer of material containing chalcogen particles as described above. Heater unit 1008C heats the chalcogen layer and precursor layer as described above. Note that it is also possible to deposit the precursor layer (or sub-layers) then deposit the chalcogen-containing layer and then heat all three layers together to form the IB-IIIA-chalcogenide compound film used for the photovoltaic absorber layer.
  • the total number of printing steps can be modified to construct absorber layers with bandgaps of differential gradation.
  • additional layers fourth, fifth, sixth, and so forth
  • additional layers can be printed (and optionally annealed between printing steps) to create an even more finely-graded bandgap within the absorber layer.
  • fewer films e.g. double printing
  • the ratio of elements within a particle or flake may be varied to produce more desired material properties.
  • this embodiment comprises using desired stoichiometric ratios of elements so that the particles used in the ink have a reduced melting temperature.
  • the amount of the group IB element and the amount of the chalcogen is controlled to move the resulting material to a portion of the phase diagram that has a reduced melting temperature.
  • the values for x and y are selected to create a material with reduced melting temperature as determined by reference to a phase diagram for the material.
  • Phase diagrams for the following materials may be found in ASM Handbook, Volume 3 Alloy Phase Diagrams (1992) by ASM International and fully incorporated herein by reference for all purposes. Some specific examples may be found on pages 2-168, 2-170, 2-176, 2-178, 2- 208, 2-214, 2-257, and/or 2-259.
  • copper selenide has multiple melting temperatures depending on the ratio of copper to selenium in the material. Everything more Se-rich (i.e. right on the binary phase diagram with pure Cu on the left and pure Se on the right) of the solid-solution O1 2 - xSe will create liquid selenium.
  • the melting temperature may be as low as 221 0 C (more Se rich than CuiSe 2 ), as low as 332 0 C (for compositions between CuiSei & CuiSe 2 ), and as low as 377 0 C (for compositions between Cu 2 -xSe and CuiSei).
  • the material is all liquid for Cu-Se that is more Se-rich than the eutectic (-57.9 wt.-% Se).
  • the material is all liquid for Cu-Se that is more Se-rich than the eutectic (-57.9 wt.-% Se).
  • gallium selenide which may have multiple melting temperatures depending on the ratio of gallium to selenium in the material. Everything more Se- rich (i.e. right on the binary phase diagram with pure Ga on the left and pure Se on the right) than Ga 2 Se3 will create liquid above 220 0 C, which is mainly pure Se.
  • Making Ga-Se more Se-rich than GaiSei is possible by making e.g. the compound Ga 2 Se3 (or anything more Se-rich than GaiSei), but only when adding other sources of selenium when working with a composition in between or equal to GaiSei and Ga 2 Se3 (being an additional source of selenium or Se-rich Cu- Se) will liquefy the Ga-Se at processing temperature.
  • an additional source of Se may be provided to facilitate the creation of a liquid involving gallium selenide.
  • indium selenide which may have multiple melting temperatures depending on the ratio of indium to selenium in the material. Everything more Se-rich (i.e. right on the binary phase diagram with pure In on the left and pure Se on the right) than In 2 Se3 will create liquid above 220 0 C, which is mainly pure Se. Making In-Se more Se-rich than IniSei would create liquid for In2Se3 and also for In ⁇ Se?
  • pure liquid In can be created at 156°C and even more liquid at 520 0 C (or at a higher temperature when going more Se-rich moving from the eutectic point of -24.0 wt.-% Se up to IniSei).
  • a bulk composition less Se-rich than the In-Se eutectic (-24.0 wt.-% Se)
  • all the In-Se will turn into a liquid at 520 0 C.
  • one of the other particles such as but not limited to CuiSe 2 and/or Se
  • one of the other particles such as but not limited to CuiSe 2 and/or Se
  • liquid may be created at our processing temperature by: 1) adding a separate source of selenium, 2) using Cu-Se more Se-rich than Cu 2 -xSe, 3) using Ga-emulsion (or In-Ga emulsion), or In (in an air free environment), or 4) using In-Se less Se-rich than InI SeI though this may also require an air free environment.
  • the composition may be Cu x Se y , wherein x is in the range of about 2 to about 1 and y is in the range of about 1 to about 2.
  • the composition When indium selenide is used, the composition may be In x Se y , wherein x is in the range of about 1 to about 6 and y is in the range of about 0 to about 7.
  • the composition When gallium selenide is used, the composition may be Ga x Sey, wherein x is in the range of about 1 to about 2 and y is in the range of about 1 to about 3.
  • FIG. 1OA yet another embodiment of the present invention will now be described.
  • overpressure from chalcogen vapor is used to provide a chalcogen atmosphere to improve processing of the film and crystal growth.
  • Figure 1OA shows a chamber 1050 with a substrate 1052 having a contact layer 1054 and a precursor layer 1056.
  • Extra sources 1058 of chalcogen are included in the chamber and are brought to a temperature to generate chalcogen vapor as indicated by lines 1060.
  • the chalcogen vapor is provided to have a partial pressure of the chalcogen present in the atmosphere greater than or equal to the vapor pressure of chalcogen that would be required to maintain a partial chalcogen pressure at the processing temperature and processing pressure to minimize loss of chalcogen from the precursor layer, and if desired, provide the precursor layer with additional chalcogen.
  • this chalcogen vapor may be provided by using a partially or fully enclosed chamber with a chalcogen source 1062 therein or coupled to the chamber.
  • the chalcogen atmosphere may be provided by supplying a source producing a chalcogen vapor.
  • the chalcogen vapor may serve to help keep the chalcogen in the film or to provide the chalcogen to covert the precursor layer.
  • the chalcogen vapor may or may not be used to provide excess chalcogen. In some embodiments, this may serve more to keep the chalcogen present in the film than to provide more chalcogen into the film.
  • this maybe used as a chalcogen that is introduced into an otherwise chalcogen free or selenium free precursor layer.
  • the exposure to chalcogen vapor may occur in a non-vacuum environment.
  • the exposure to chalcogen vapor may occur at atmospheric pressure.
  • the chalcogen may be carried into the chamber by a carrier gas.
  • the carrier gas may be an inert gas such as nitrogen, argon, or the like.
  • This chalcogen atmosphere system may be adapted for use in a roll-to-roll system.
  • the present invention may be adopted for use with a roll-to-roll system where the substrate 1070 carrying the precursor layer may be flexible and configured as rolls 1072 and 1074.
  • the chamber 1076 may be at vacuum or non-vacuum pressures.
  • the chamber 1076 may be designed to incorporate a differential valve design to minimize the loss of chalcogen vapor at the chamber entry and chamber exit points of the roll-to- roll substrate 1070.
  • yet another embodiment of the present invention uses a chamber 1090 of sufficient size to hold the entire substrate, including any rolls 1072 or 1074 associated with using a roll-to-roll configuration.
  • the embodiments of the present invention may also be used on a rigid substrate 1100.
  • the rigid substrate 1100 may be glass, solar glass, low- iron glass, soda-lime glass, steel, stainless steel, aluminum, polymer, ceramic, coated polymer, plates, metallized ceramic plates, metallized polymer plates, metallized glass plates, or other rigid material suitable for use as a solar cell substrate and/or any single or multiple combination of the aforementioned.
  • a high speed pick- and-place robot 1102 may be used to move rigid substrates 1100 onto a processing area from a stack or other storage area.
  • the substrates 1100 are placed on a conveyor belt which then moves them through the various processing chambers.
  • the substrates 1100 may have already undergone some processing by the time and may already include a precursor layer on the substrate 1100.
  • Other embodiments of the invention may form the precursor layer as the substrate 1100 passes through the chamber 1106.
  • Figure 1 IB shows another embodiment of the present system where a pick-and-place robot 1110 is used to position a plurality of rigid substrates on a carrier device 1112 which may then be moved to a processing area as indicated by arrow 1114. This allows for multiple substrates 1100 to be loaded before they are all moved together to undergo processing.
  • the particles used to form a precursor layer 1500 may include particles that are inter-metallic particles 1502.
  • an inter-metallic material is a material containing at least two elements, wherein the amount of one element in the inter- metallic material is less than about 50 molar percent of the total molar amount of the inter- metallic material and/or the total molar amount of that one element in a precursor material.
  • the amount of the second element is variable and may range from less than about 50 molar percent to about 50 or more molar percent of the inter-metallic material and/or the total molar amount of that one element in a precursor material.
  • inter-metallic phase materials may be comprised of two or more metals where the materials are admixed in a ratio between the upper bound of the terminal solid solution and an alloy comprised of about 50% of one of the elements in the inter-metallic material.
  • the particle distribution shown in the enlarged view of Figure 12 is purely exemplary and is nonlimiting. It should be understood that some embodiments may have particles that all contain inter-metallic materials, mixture of metallic and inter-metallic materials, metallic particles and inter-metallic particles, or combinations thereof.
  • inter-metallic phase materials are compounds and/or intermediate solid solutions containing two or more metals, which have characteristic properties and crystal structures different from those of either the pure metals or the terminal solid solutions.
  • Inter-metallic phase materials arise from the diffusion of one material into another via crystal lattice vacancies made available by defects, contamination, impurities, grain boundaries, and mechanical stress. Upon two or more metals diffusing into one another, intermediate metallic species are created that are combinations of the two materials.
  • Sub-types of inter- metallic compounds include both electron and interstitial compounds.
  • Electron compounds arise if two or more mixed metals are of different crystal structure, valency, or electropositivity relative to one another; examples include but are not limited to copper selenide, gallium selenide, indium selenide, copper telluride, gallium telluride, indium telluride, and similar and/or related materials and/or blends or mixtures of these materials.
  • Interstitial compounds arise from the admixture of metals or metals and non-metallic elements, with atomic sizes that are similar enough to allow the formation of interstitial crystal structures, where the atoms of one material fit into the spaces between the atoms of another material.
  • inter-metallic materials where each material is of a single crystal phase, two materials typically exhibit two diffraction peaks, each representative of each individual material, superimposed onto the same spectra.
  • inter-metallic compounds typically contain the crystal structures of both materials contained within the same volume.
  • Examples include but are not limited to Cu-Ga, Cu-In, and similar and/or related materials and/or blends or mixtures of these materials, where the compositional ratio of each element to the other places that material in a region of its phase diagram other than that of the terminal solid solution.
  • Inter-metallic materials are useful in the formation of precursor materials for CIGS photovoltaic devices in that metals interspersed in a highly homogenous and uniform manner amongst one another, and where each material is present in a substantially similar amount relative to the other, thus allowing for rapid reaction kinetics leading to high quality absorber films that are substantially uniform in all three dimensions and at the nano-, micro, and meso- scales.
  • terminal solid solutions may have mechanical properties that differ from those of inter-metallic materials and/or intermediate solid solutions (solid solutions between a terminal solid solution and/or element). As a nonlimiting example, some terminal solid solutions are not brittle enough to be milled for size reduction. Other embodiments may be too hard to be milled. The use of inter-metallic materials and/or intermediate solid solutions can address some of these drawbacks.
  • a precursor material suitable for use in a thin film solar cell may contain group IB and group IDA elements such as copper and indium, respectively. If an inter-metallic phase of Cu-In is used such as CuJn 2 , then Indium is part of an In-rich Cu material and not added as pure indium. Adding pure indium as a metallic particle is challenging due to the difficulty in achieving In particle synthesis with high yield, small and narrow nanoparticle size distribution, and requiring particle size discrimination, which adds further cost. Using inter- metallic In-rich Cu particles avoids pure elemental In as a precursor material.
  • the inter-metallic material is Cu poor, this also advantageously allows Cu to be added separately to achieve precisely the amount of Cu desired in the precursor material.
  • the Cu is not tied to the ratio fixed in alloys or solid solutions that can be created by Cu and In.
  • the inter- metallic material and the amount of Cu can be fine tuned as desired to reach a desired stoichiometric ratio. Ball milling of these particles results in no need for particle size discrimination, which decreases cost and improves the throughput of the material production process.
  • having an inter-metallic material provides a broader range of flexibility. Since economically manufacturing elemental indium particles is difficult, it would be advantageous to have an indium-source that is more economically interesting. Additionally, it would be advantageous if this indium source still allows varying both the Cu/(In+Ga) and Ga/(In+Ga) in the layer independently of each other. As one nonlimiting example, a distinction can be made between CUnIn 9 and CuJn 2 with an inter- metallic phase. This particularly true if only one layer of precursor material is used.
  • the final compound may be created with stoichiometric ratios that more broadly explore the bounds of Cu/(In+Ga) with a compositional range of about 0.7 to about 1.0, and Ga/(In+Ga) with a compositional range of about 0.05 to about 0.3
  • Cu/(In + Ga) compositional range may be about 0.01 to about 1.0.
  • the Cu/(In+Ga) compositional range may be about 0.01 to about 1.1.
  • the Cu/(In+Ga) compositional range may be about 0.01 to about 1.5. This typically results in additional Cu x Se y which we might be able to remove afterwards if it is at the top surface. It should be understood that these ratios may apply to any of the above embodiments described herein.
  • an intermetallic material may create more liquid than other compounds.
  • CuJn 2 will form more liquid when heated during processing than CuI Hn9. More liquid promotes more atomic intermixing since it easier for material to move and mix while in a liquid stage.
  • CuJn 2 is a material that is metastable.
  • the material is more prone to decomposition, which advantageously for the present invention, will increase the rate of reaction (kinetically). Further, the material is less prone to oxidation (e.g. compared to pure In) and this further simplifies processing.
  • This material may also be single-phase, which would make it more uniform as a precursor material, resulting in better yield.
  • the layer 1500 may then be heated in a suitable atmosphere to react the layer 1500 in Figure 13 and form film 1510 shown in Figure 14.
  • the layer 915 may be comprised of various materials including but not limited at least one of the following: a group IB element, a group IIIA element, a group VIA element, a group IA element (new style: group 1), a binary and/or multinary alloy of any of the preceding elements, a solid solution of any of the preceding elements.
  • sodium or a sodium- based material such as but not limited to sodium, a sodium compound, sodium fluoride, and/or sodium indium sulfide, may also be used in layer 915 with the precursor material to improve the qualities of the resulting film.
  • Figure 14 shows that a layer 932 may also be used as described with regards to Figure 8F. Any of the method suggested previously with regards to sodium content may also be adapted for use with the embodiments shown in Figures 13-14.
  • embodiments of the present invention also disclose material comprised of at least two elements wherein the amount of at least one element in the material is less than about 50 molar percent of the total molar amount of that element in the precursor material.
  • this may include other group IB poor, group IB-IIIA materials such as Cu-poor Cu x ln y particles (where x ⁇ y).
  • the amount of group IIIA material may be in any range as desired (more than about 50 molar percent of the element in the precursor material or less than 50 molar percent).
  • CUiGa 2 may be used with elemental Cu and elemental In.
  • this material is not an inter-metallic material, this material is a intermediate solid solution and is different from a terminal solid solution. All solid particles are created based on a CUiGa 2 precursor. In this embodiment, no emulsions are used.
  • other viable precursor materials may be formed using a group IB rich, group IB-IIIA material.
  • a variety of intermediate solid-solutions may be used.
  • Cu-Ga 38 at % Ga
  • Cu-Ga (30 at % Ga) may be used in precursor layer 1500 with elemental copper and elemental indium. Both of these embodiments describe Cu-rich materials with the Group IIIA element being less than about 50 molar percent of that element in the precursor material.
  • Cu-Ga multiphasic, 25 at % Ga
  • nanoparticles of these materials may be created by mechanical milling or other size reduction methods.
  • these particles may be made by electroexplosive wire (EEW) processing, evaporation condensation (EC), pulsed plasma processing, or other methods.
  • EW electroexplosive wire
  • EC evaporation condensation
  • pulsed plasma processing or other methods.
  • the particles sizes may be in the range of about IOnm to about 1 micron. They may be of any shape as described herein.
  • two or more layers of materials may be coated, printed, or otherwise formed to provide a precursor layer with the desired stoichiometric ratio.
  • layer 1530 may contain a precursor material having Cu ⁇ ln 9 and a Ga source such as elemental Ga and/or Ga x Se y .
  • a copper rich precursor layer 1532 containing Cu 7 sln 28 (solid-solution) and elemental indium or In x Se y may be printed over layer 1530.
  • the film may have a stoichiometric ratio of Cu/(In+Ga) with a compositional range of about 0.7 to about 1.0 and Ga/(In+Ga) with a compositional range of about 0.05 to about 0.3.
  • the inter-metallic material is used as a feedstock or starting material from which particles and/or nanoparticles may be formed.
  • Figure 21 shows one inter-metallic feedstock particle 1550 being processed to form other particles. Any method used for size reduction and/or shape change may be suitable including but not limited to milling, EEW, EC, pulsed plasma processing, or combinations thereof. Particles 552, 554, 556, and 558 may be formed. These particles may be of varying shapes and some may contain only the inter- metallic phase while others may contain that phase and other material phases.
  • Still other embodiments of the present invention may use a Cu-In precursor material wherein Cu-In contribute less than about 50 percent of both Cu and In found in the precursor material. The remaining amount is incorporated by elemental form or by non IB-IIIA alloys. Thus, a Cu ⁇ ln 9 may be used with elemental Cu, In, and Ga to form a resulting film.
  • the IB source may be any particle that contains Cu without being alloyed with In and Ga (Cu, Cu-Se).
  • the IIIA source may be any particle that contains In without Cu (In-Se, In-Ga-Se) or any particle that contains Ga without Cu (Ga, Ga-Se, or In-Ga-Se).
  • Other embodiments may have these combinations of the IB material in a nitride or oxide form.
  • Still other embodiments may have these combinations of the IIIA material in a nitride or oxide form.
  • the present invention may use any combination of elements and/or selenides (binary, ternary, or multinary) may be used.
  • some other embodiments may use oxides such as In 2 ⁇ 3 to add the desired amounts of materials.
  • more than one solid solution may be used, multi-phasic alloys, and/or more general alloys may also be used.
  • the annealing process may also involve exposure of the compound film to a gas such as H 2 , CO, N 2 , Ar, H 2 Se, or Se vapor.
  • a composition in the ⁇ phase for Cu-In (about 42.52 to about 44.3 wt % In) and/or a composition between the ⁇ phase for Cu-In and Cubing may be suitable inter-metallic materials for use with the present invention to form a group IB-IIIA-VIA compound.
  • these inter-metallic materials may be mixed with elemental or other materials such as Cu-Se, In-Se, and/or Ga-Se to provide sources of the group IB or IIIA material to reach the desired stoichiometric ratios in the final compound.
  • inter-metallic material examples include compositions of Cu-Ga containing the following phases: ⁇ i (about 31.8 to about 39.8 wt % Ga), ⁇ 2 (about 36.0 to about 39.9 wt % Ga), ⁇ 3 (about 39.7 to about -44.9 wt % Ga), the phase between ⁇ 2 and 7 3, the phase between the terminal solid solution and ⁇ i, and ⁇ (about 66.7 to about 68.7 wt % Ga).
  • ⁇ i about 31.8 to about 39.8 wt % Ga
  • ⁇ 2 about 36.0 to about 39.9 wt % Ga
  • ⁇ 3 about 39.7 to about -44.9 wt % Ga
  • the phase between ⁇ 2 and 7 3 the phase between the terminal solid solution and ⁇ i
  • ⁇ about 66.7 to about 68.7 wt % Ga
  • inter-metallic materials may be multi-phasic which are more likely to lead to brittle materials that can be mechanically milled.
  • Phase diagrams for the following materials may be found in ASM Handbook, Volume 3 Alloy Phase Diagrams (1992) by ASM International and fully incorporated herein by reference for all purposes. Some specific examples (fully incorporated herein by reference) may be found on pages 2-168, 2-170, 2-176, 2-178, 2-208, 2-214, 2-257, and/or 2- 259.
  • any of the above particles may be spherical, spheroidal, or other shaped.
  • the use of core-shell particles and printed layers of a chalcogen source may be combined as desired to provide excess amounts of chalcogen.
  • the layer of the chalcogen source may be above, below, or mixed with the layer containing the core- shell particles.
  • the temperature may also vary over different time periods of precursor layer processing. As a nonlimiting example, the heating may occur at a first temperature over an initial processing time period and proceed to other temperatures for subsequent time periods of the processing.
  • the method may include intentionally creating one or more temperature dips so that, as a nonlimiting example, the method comprises heating, cooling, heating, and subsequent cooling.
  • the dip may be between about 50 to 200 degrees C from the initial processing temperature.
  • some embodiments of the present invention may provide sufficient chalcogen vapor pressure so that particles leaving the liquid in the precursor layer during processing is replaced by particles in the surrounding atmosphere.
  • there is sufficient vapor pressure so that the loss from the liquid chalcogen in the precursor layer is less than about 1 wt% of the total amount of chalcogen in the precursor layer.
  • the suitable atmosphere may contain selenium, sulfur, tellurium, H 2 , CO, H 2 Se, H 2 S, Ar, N 2 , and/or combinations or blends of these. It should be understood that evaporation or printing may also be used to add Se to the stack of layers for processing.
  • some embodiments of the present invention may provide sufficient chalcogen vapor pressure so that particles leaving the liquid in the precursor layer during processing is replaced by particles in the surrounding atmosphere.
  • there is sufficient vapor pressure so that the loss from the liquid chalcogen in the precursor layer is less than about 1 wt% of the total amount of chalcogen in the precursor layer.
  • there is sufficient vapor pressure so that the loss from the liquid chalcogen in the precursor layer is less than about 5 wt% of the total amount of chalcogen in the precursor layer.
  • there is sufficient vapor pressure so that the loss from the liquid chalcogen in the precursor layer is less than about 10 wt% of the total amount of chalcogen in the precursor layer.

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Abstract

L'invention concerne un procédé de formation à haut rendement d'une couche précurseur semi-conductrice en utilisant une vapeur contenant un matériau chalcogène. Selon un mode de réalisation, le procédé consiste à former un matériau précurseur comprenant des particules de groupe IB et/ou de groupe IDA de toute forme. Le procédé peut consister à former une couche précurseur du matériau précurseur sur une surface d'un substrat. Le procédé peut également consister à chauffer le matériau précurseur de particules dans une atmosphère chalcogène sensiblement exempte d'oxygène à une température de traitement suffisante pour mettre en réaction les particules et pour libérer le chalcogène des particules de chalcogénure, le chalcogène prenant une forme liquide et agissant comme un flux pour améliorer le mélange intime des éléments pour constituer un film de chalcogénure de groupe IB-IIIA selon un rapport stœchiométrique désiré. L'atmosphère chalcogène peut créer une pression partielle supérieure ou égale à la pression de vapeur de chalcogène liquide dans la couche précurseur à la température de traitement.
EP07757446A 2006-02-23 2007-02-23 Formation a haut rendement de couche semi-condutrice en utilisant un materiau chalcogene et intermetalique Withdrawn EP1998902A2 (fr)

Applications Claiming Priority (12)

Application Number Priority Date Filing Date Title
US11/361,515 US20070163640A1 (en) 2004-02-19 2006-02-23 High-throughput printing of semiconductor precursor layer by use of chalcogen-rich chalcogenides
US11/361,522 US20070166453A1 (en) 2004-02-19 2006-02-23 High-throughput printing of chalcogen layer
US11/361,498 US20070163639A1 (en) 2004-02-19 2006-02-23 High-throughput printing of semiconductor precursor layer from microflake particles
US11/361,103 US20070169809A1 (en) 2004-02-19 2006-02-23 High-throughput printing of semiconductor precursor layer by use of low-melting chalcogenides
US11/361,433 US7700464B2 (en) 2004-02-19 2006-02-23 High-throughput printing of semiconductor precursor layer from nanoflake particles
US11/361,464 US20070169810A1 (en) 2004-02-19 2006-02-23 High-throughput printing of semiconductor precursor layer by use of chalcogen-containing vapor
US11/361,523 US20070169811A1 (en) 2004-02-19 2006-02-23 High-throughput printing of semiconductor precursor layer by use of thermal and chemical gradients
US39619906A 2006-03-30 2006-03-30
US11/395,668 US8309163B2 (en) 2004-02-19 2006-03-30 High-throughput printing of semiconductor precursor layer by use of chalcogen-containing vapor and inter-metallic material
US11/394,849 US20070163641A1 (en) 2004-02-19 2006-03-30 High-throughput printing of semiconductor precursor layer from inter-metallic nanoflake particles
US11/395,438 US20070163643A1 (en) 2004-02-19 2006-03-30 High-throughput printing of chalcogen layer and the use of an inter-metallic material
PCT/US2007/062764 WO2007101136A2 (fr) 2006-02-23 2007-02-23 formation à haut rendement de couche semi-conductrice en utilisant un matériau chalcogène et intermétallique

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CN101471394A (zh) * 2007-12-29 2009-07-01 中国科学院上海硅酸盐研究所 铜铟镓硫硒薄膜太阳电池光吸收层的制备方法
JP5185171B2 (ja) * 2009-03-24 2013-04-17 本田技研工業株式会社 薄膜太陽電池の光吸収層の形成方法
JP5213777B2 (ja) * 2009-03-26 2013-06-19 京セラ株式会社 薄膜太陽電池の製法
WO2011063209A1 (fr) * 2009-11-20 2011-05-26 E. I. Du Pont De Nemours And Company Compositions de transistor à couches minces et procédés correspondants
JP2011138837A (ja) * 2009-12-26 2011-07-14 Kyocera Corp 半導体層の製造方法および光電変換装置の製造方法
JP5495849B2 (ja) * 2010-02-25 2014-05-21 京セラ株式会社 半導体層の製造方法および光電変換装置の製造方法
KR101749137B1 (ko) * 2010-06-22 2017-06-21 영남대학교 산학협력단 태양광 전지용 나노결정질 구리 인듐 디셀레니드 (cis) 및 잉크-기반 합금 흡수재층
JP2012114250A (ja) * 2010-11-25 2012-06-14 Kyocera Corp 光電変換装置の製造方法
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