WO2022138385A1 - Composition for forming electrode, solar cell element, and aluminum/silver stacked electrode - Google Patents

Composition for forming electrode, solar cell element, and aluminum/silver stacked electrode Download PDF

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WO2022138385A1
WO2022138385A1 PCT/JP2021/046334 JP2021046334W WO2022138385A1 WO 2022138385 A1 WO2022138385 A1 WO 2022138385A1 JP 2021046334 W JP2021046334 W JP 2021046334W WO 2022138385 A1 WO2022138385 A1 WO 2022138385A1
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electrode
silver
particles
aluminum
bismuth
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PCT/JP2021/046334
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French (fr)
Japanese (ja)
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琢磨 鈴木
祐樹 中村
卓也 今井
鉄也 佐藤
雄太 原田
絢香 黒田
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昭和電工マテリアルズ株式会社
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Publication of WO2022138385A1 publication Critical patent/WO2022138385A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/28—Manufacture of electrodes on semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/268
    • H01L21/283—Deposition of conductive or insulating materials for electrodes conducting electric current
    • H01L21/288—Deposition of conductive or insulating materials for electrodes conducting electric current from a liquid, e.g. electrolytic deposition
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes

Definitions

  • the present disclosure relates to an electrode forming composition, a solar cell element, and an aluminum / silver laminated electrode.
  • renewable energy examples include solar power, geothermal power, wind power, wave power, tidal power, and biomass.
  • photovoltaic power generation is expected to be an effective solution to the growing energy problem, attracting attention as a clean natural energy that does not emit carbon dioxide during power generation while utilizing inexhaustible solar energy.
  • a crystalline silicon solar cell using a silicon (Si) substrate as a semiconductor substrate is generally used.
  • a current collecting electrode for collecting carriers and a carrier for taking out as an output are used.
  • An output take-out electrode (bus bar electrode) is formed.
  • the current collecting electrode on the light receiving surface is particularly called a finger electrode.
  • a composition for forming a silver (Ag) electrode is used for forming the light receiving surface electrode, and printing of the finger electrode and the bus bar electrode portion is performed individually or collectively.
  • a composition for forming a silver electrode is used for forming the bus bar electrode, and a composition for forming an aluminum (Al) electrode is used for the electrode for collecting current.
  • Each electrode-forming composition contains conductive metal particles, glass particles, various additives and the like.
  • Silver particles are generally used as the conductive metal particles in the composition for forming a silver electrode for forming the light receiving surface electrode and the back surface bus bar electrode.
  • the reasons for this are that the volumetric resistance of silver is low (1.47 ⁇ 10-6 ⁇ cm), the silver particles are self-reduced and sintered under the above heat treatment conditions, and the silver particles and the silicon substrate have good ohmic contact.
  • the electrode formed from the silver particles has excellent wettability of the solder material, and the wiring material (tab wire or the like) for electrically connecting the solar cell elements can be suitably bonded.
  • the aluminum in the composition for forming an aluminum electrode undergoes a eutectic reaction with silicon and a high concentration diffusion layer (p + ) is formed on the front surface of the back surface.
  • p + high concentration diffusion layer
  • -Si layer, Back Surface Field; BSF Back Surface Field
  • the minority carrier recombination rate on the back surface is as fast as about 3 ⁇ 10 3 cm / s, which is a factor that lowers the power generation performance of the solar cell element. Can be.
  • a PERC (Passivated Emitter, Real Cell) structure has attracted attention as a measure for reducing backside recombination loss (see, for example, Patent Document 1).
  • the PERC structure is characterized in that the ohmic contact portion between the back surface electrode and the Si substrate, which is one of the causes of the back surface recombination, is restricted to a point shape or a line shape, and all parts other than the contact portion of the back surface electrode are covered with a passivation film. It has been.
  • the back surface passivation film that can be used for the PERC structure include an amorphous aluminum oxide ( AlOX ) film obtained by an atomic layer deposition method (ALD) or a CVD method (Chemical Vapor Deposition). It is known that the AlOX film obtained by the ALD method or the CVD method has a large negative fixed charge, and the PERC structure solar cell element to which this is applied is known to exhibit high power generation performance.
  • a double-sided light receiving (biaxial) type solar cell element can be realized.
  • One of the advantages of the biological-PERC structure is that the light inserted into the back surface can be utilized.
  • an electrode forming composition containing silver and an electrode forming containing aluminum are formed.
  • the composition for use is printed on a predetermined area of the substrate, dried, and then heat-treated collectively.
  • the aluminum oxide (Al 2 O 3 ) film formed on the surface of the aluminum electrode and the solder covering the wiring material have poor wettability, so that the wiring material cannot be directly bonded to the aluminum electrode.
  • the composition for forming a silver electrode is applied.
  • the connection failure of the wiring material may occur due to the step (difference in thickness) between the aluminum electrode and the silver electrode as the back surface output extraction electrode, or as a solar cell. Reliability may be compromised.
  • the silver electrode as the output take-out electrode is not continuously formed along the connection direction of the wiring material from the viewpoint of reducing the amount of the composition for forming the silver electrode, and is not formed continuously along the connection direction of the wiring material.
  • an aluminum electrode may be formed between the silver electrode and the silver electrode.
  • the thickness of the aluminum electrode after heat treatment (after firing) is generally 20 ⁇ m to 40 ⁇ m
  • the thickness of the silver electrode as the back surface output take-out electrode is generally 2 ⁇ m to 5 ⁇ m.
  • the aluminum electrode formed on the substrate and the silver electrode formed on the aluminum electrode are laminated. It is considered effective to form an electrode (hereinafter, also referred to as an aluminum / silver laminated electrode).
  • an electrode forming composition containing aluminum particles is applied to the back surface of a substrate in a desired pattern to form an aluminum particle-containing film, and then an electrode containing silver is formed. It is conceivable to print the composition on an aluminum particle-containing film in a desired pattern and heat the composition all at once.
  • the aluminum / silver laminated electrodes have sufficient reliability because they are less likely to deteriorate even when placed in a high temperature and high humidity environment.
  • the present disclosure also relates to the provision of a solar cell element and an aluminum / silver laminated electrode obtained by using this electrode forming composition.
  • Means for carrying out the above tasks include the following embodiments.
  • Silver-containing particles, bismuth-containing particles, and glass particles are included.
  • the glass particles contain phosphorus-containing glass particles, and the volume average particle diameter of the phosphorus-containing glass particles is 10.0 ⁇ m to 50.
  • a composition for forming an electrode which is 0.0 ⁇ m.
  • ⁇ 3> The electrode-forming composition according to ⁇ 1> or ⁇ 2>, wherein the phosphorus-containing glass particles have a phosphorus oxide content of 20.0% by mass or more as a whole.
  • ⁇ 4> The electrode-forming composition according to ⁇ 2>, wherein the boron oxide-containing glass particles have a boron oxide content of 3.0% by mass or more as a whole.
  • ⁇ 5> The electrode-forming composition according to ⁇ 2> or ⁇ 4>, wherein the boron-containing glass particles contain bismuth oxide.
  • ⁇ 6> The electrode-forming composition according to any one of ⁇ 1> to ⁇ 5>, wherein the bismuth-containing particles contain at least one selected from the group consisting of metal bismuth, bismuth alloy, and bismuth oxide.
  • ⁇ 7> Any one of ⁇ 1> to ⁇ 6>, wherein the mass ratio (Bi / Ag ratio) of the content of the bismuth-containing particles to the content of the silver-containing particles is 0.30 to 1.40.
  • the composition for forming an electrode according to. ⁇ 8> In any one of ⁇ 1> to ⁇ 7>, the mass ratio (Bi / G ratio) of the content of the bismuth-containing particles to the content of the glass particles is 0.5 to 15.0.
  • the electrode-forming composition according to the above. ⁇ 9> The electrode forming device according to any one of ⁇ 1> to ⁇ 8>, wherein the content of the glass particles is 1.0% by mass to 15.0% by mass of the entire electrode forming composition. Composition.
  • the electrode forming composition according to any one of ⁇ 1> to ⁇ 9> which comprises at least one selected from the group consisting of a solvent and a resin.
  • the semiconductor substrate, the passivation film provided on the semiconductor substrate, and the heat-treated product of the electrode forming composition according to any one of ⁇ 1> to ⁇ 11> provided on the passivation film are included.
  • the first electrode is an aluminum / silver laminated electrode further comprising a bismuth oxide phase and a glass phase containing phosphorus.
  • an electrode forming composition capable of forming an aluminum / silver laminated electrode having excellent reliability in a high temperature and high humidity environment. According to the present disclosure, a solar cell element and an aluminum / silver laminated electrode obtained by using this electrode forming composition are provided.
  • the term "process” is included in this term not only as an independent process but also as long as the purpose of the process is achieved even if it cannot be clearly distinguished from other processes.
  • the numerical range indicated by using "-" in the present disclosure indicates a range including the numerical values before and after "-" as the minimum value and the maximum value, respectively.
  • the content of each component in the composition is the sum of the plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition. Means quantity.
  • equivalent components are designated by the same reference numerals.
  • the term “laminated” refers to stacking layers, and two or more layers may be bonded or the two or more layers may be removable.
  • the term “cross section” means a surface obtained by cutting a solar cell element perpendicular to the surface direction of the semiconductor substrate.
  • heat treatment includes heating (firing, etc.) performed under the condition that the particles contained in the object to be heat-treated are sintered or melted.
  • the electrode-forming composition according to an embodiment of the present disclosure includes silver-containing particles, bismuth-containing particles, and glass particles, and the glass particles include phosphorus-containing glass particles and the phosphorus-containing glass.
  • the electrode-forming composition containing silver-containing particles, bismuth-containing particles, and glass particles containing phosphorus as glass particles contains silver-containing particles and bismuth-containing particles, and does not contain phosphorus-containing glass particles.
  • the electrode forming composition it is possible to form an aluminum / silver laminated electrode having excellent reliability in a high temperature and high humidity environment.
  • the volume average particle diameter of the phosphorus-containing glass particles is 10.0 ⁇ m to 50.0 ⁇ m, it is possible to form an aluminum / silver laminated electrode having higher reliability in a high temperature and high humidity environment. The reason is not always clear, but it can be considered as follows.
  • the electrode-forming composition containing the silver-containing particles and the bismuth-containing particles is applied to a desired region on the aluminum particle-containing film formed on the substrate, dried if necessary, and then heat-treated.
  • the silver-containing particles contained in the electrode-forming composition are sintered to form a silver electrode
  • the aluminum particles contained in the aluminum particle-containing film are sintered to form an aluminum electrode.
  • the bismuth oxide phase formed by oxidizing the bismuth contained in the bismuth-containing particles exhibits a property of suppressing mutual diffusion at the interface between the silver electrode and the aluminum electrode (hereinafter, also referred to as diffusion barrier property). Therefore, the concentration of aluminum in the silver electrode is suppressed to a low level, and the wettability to the wiring material is maintained well.
  • the bismuth-containing particles is transferred to the aluminum particle-containing film by heat treatment to form a bismuth oxide phase between the aluminum particles or between the aluminum particles and the substrate.
  • This improves the bulk strength of the formed aluminum electrode and the adhesion to the substrate.
  • the aluminum / silver laminated electrode is placed in a high temperature and high humidity environment, a part of the bismuth oxide phase is reduced to metal bismuth at the interface between the aluminum electrode and the silver electrode, and a volume change occurs. As a result, cracks or the like occur at the interface between the aluminum electrode and the silver electrode, which causes the reliability of the electrode to deteriorate.
  • the melt of the phosphorus-containing glass particles reacts with the bismuth oxide phase at the interface between the aluminum electrode and the silver electrode by heat treatment to reduce bismuth oxide. Acts to suppress. As a result, it is considered that the state of the interface between the aluminum electrode and the silver electrode is maintained well, and the reliability in a high temperature and high humidity environment is improved.
  • the volume average particle size of the phosphorus-containing glass particles is 10.0 ⁇ m or more, so that the temperature is higher than that when the volume average particle size of the phosphorus-containing glass particles is smaller than 10.0 ⁇ m. Greater reliability in moist environments. It is considered that this is because the uneven shape due to the phosphorus-containing glass particles is formed on the surface of the silver electrode obtained by the heat treatment of the electrode forming composition. As a result, it is considered that the stress accumulated between the wiring material and the silver electrode is relaxed and the generation of cracks and the like is suppressed.
  • the volume average particle diameter of the phosphorus-containing glass particles is 50.0 ⁇ m or less, the phosphorus-containing glass particles in the electrode forming composition have good dispersibility and are formed on the surface of the silver electrode. It is considered that the stress accumulated between the wiring material and the silver electrode is effectively alleviated by suppressing the uneven distribution of the uneven shape.
  • the electrode forming composition contains silver-containing particles.
  • the silver-containing particles contained in the electrode forming composition may be only one kind or two or more kinds.
  • the silver-containing particles are not particularly limited as long as they are silver-containing particles. Among them, at least one selected from silver particles and silver alloy particles is preferable, and at least one selected from silver particles and silver alloy particles having a silver content of 50.0% by mass or more is preferable.
  • the silver content in the silver particles is not particularly limited. For example, it can be 95.0% by mass or more of the whole silver particles, preferably 97.0% by mass or more, and more preferably 99.0% by mass or more.
  • the silver alloy particles are not particularly limited as long as they are alloy particles containing silver. Above all, from the viewpoint of the melting point and sinterability of the silver alloy particles, the silver content is preferably 50.0% by mass or more, more preferably 60.0% by mass or more, and 70. It is more preferably 0% by mass or more, and particularly preferably 80.0% by mass or more. The content may be 95.0% by mass or less.
  • silver alloys include Ag-Pd-based alloys, Ag-Pd-Au-based alloys, Ag-Pd-Cu-based alloys, Ag-Pd-In-based alloys, Ag-In-based alloys, Ag-Sn-based alloys, and Ag-Zn.
  • system alloys and Ag-Sn-Zn system alloys include system alloys and Ag-Sn-Zn system alloys.
  • the silver-containing particles may or may not contain components that do not correspond to silver and silver alloys. When the silver-containing particles contain a component that does not correspond to silver or a silver alloy, the content thereof can be 3.0% by mass or less in the silver-containing particles, preferably 1.0% by mass or less. ..
  • the particle size of the silver-containing particles is not particularly limited, but the particle size (volume average particle size, hereinafter "D50%") when the accumulation from the small diameter side is 50% in the volume-based particle size distribution obtained by the laser diffraction / scattering method. It is preferably 0.1 ⁇ m to 50.0 ⁇ m, more preferably 0.15 ⁇ m to 40.0 ⁇ m, and even more preferably 0.2 ⁇ m to 30.0 ⁇ m.
  • the volume average particle diameter of the silver-containing particles is 0.1 ⁇ m or more, the concentration of silver on the surface of the aluminum / silver laminated electrode can be sufficiently increased, and the connection strength of the wiring material is improved.
  • the volume average particle diameter of the silver-containing particles is 50.0 ⁇ m or less, the resistance in the aluminum / silver laminated electrode tends to decrease.
  • the particle size of the silver-containing particles is measured by a laser diffraction type particle size distribution meter (for example, Beckman Coulter Co., Ltd., LS13 320 type laser scattering diffraction method particle size distribution measuring device). Specifically, silver-containing particles are added to 125 g of a solvent (terpineol) in the range of 0.01% by mass to 0.3% by mass to prepare a dispersion. About 100 ml of this dispersion is injected into the cell and measured at 25 ° C. The particle size distribution is measured with the refractive index of the solvent as 1.48.
  • a laser diffraction type particle size distribution meter for example, Beckman Coulter Co., Ltd., LS13 320 type laser scattering diffraction method particle size distribution measuring device. Specifically, silver-containing particles are added to 125 g of a solvent (terpineol) in the range of 0.01% by mass to 0.3% by mass to prepare a dispersion. About 100 ml of this dis
  • the shape of the silver-containing particles is not particularly limited, and may be substantially spherical, flat, block-shaped, plate-shaped, scale-shaped, or the like. From the viewpoint of sinterability between silver-containing particles, it is preferably substantially spherical, flat or plate-shaped.
  • the electrode forming composition contains bismuth-containing particles.
  • the bismuth-containing particles contained in the electrode forming composition may be only one kind or two or more kinds.
  • the bismuth-containing particles are not particularly limited as long as they are particles containing bismuth. Among them, at least one selected from metal bismuth particles, bismuth alloy particles and oxide bismuth particles is preferable, and metal bismuth particles, bismuth alloy particles having a bismuth content of 40.0% by mass or more and bismuth oxide particles are selected. It is preferable that the amount is at least one. In the present disclosure, when the bismuth-containing particles are glassy (glass particles containing bismuth), they are not considered to be bismuth-containing particles.
  • the content of bismuth in the metal bismuth particles is not particularly limited. For example, it can be 95.0% by mass or more of the total metal bismuth particles, preferably 97.0% by mass or more, and more preferably 99.0% by mass or more.
  • the bismuth alloy particles are not particularly limited as long as they are alloy particles containing bismuth.
  • the bismuth content of the bismuth alloy particles is preferably 40.0% by mass or more, and more preferably 50.0% by mass or more. It is more preferably 60.0% by mass or more, and particularly preferably 70.0% by mass or more.
  • the content of bismuth in the bismuth alloy particles may be 95.0% by mass or less.
  • bismuth alloy examples include Bi-Sn-based alloys, Bi-Sn-Cu-based alloys, Bi-Pb-Sn-based alloys, Bi-Cd-based alloys, and the like.
  • the bismuth oxide particles include bismuth trioxide (Bi 2 O 3 ) particles.
  • the bismuth oxide particles are preferably used in combination with the metal bismuth particles from the viewpoint of exhibiting sufficient diffusion barrier properties and lowering the resistance of the aluminum / laminated electrode itself.
  • the bismuth-containing particles may or may not contain components that do not correspond to metal bismuth, bismuth alloy, and bismuth oxide.
  • the content of the bismuth-containing particles is 3.0 in the bismuth-containing particles from the viewpoint of the formation of the bismuth oxide phase and the barrier property of aluminum / silver. It can be mass% or less, preferably 1.0 mass% or less.
  • the particle size of the bismuth-containing particles is not particularly limited, but the volume average particle size is preferably 0.1 ⁇ m to 50.0 ⁇ m, more preferably 0.15 ⁇ m to 40.0 ⁇ m, and 0.2 ⁇ m to 30. It is more preferably 0 ⁇ m.
  • the particle size of the bismuth-containing particles is 0.1 ⁇ m or more, the migration to the aluminum particle-containing film and the formation of the bismuth oxide phase are promoted.
  • the particle size of the bismuth-containing particles is 50.0 ⁇ m or less, the diffusion barrier property is effectively exhibited.
  • the volume average particle size of the bismuth-containing particles is measured in the same manner as the volume average particle size of the silver-containing particles.
  • the shape of the bismuth-containing particles is not particularly limited, and may be substantially spherical, flat, block-shaped, plate-shaped, scale-shaped, or the like. From the viewpoint of diffusion barrier property, it is preferably substantially spherical, flat or plate-shaped.
  • the mass ratio (Bi / Ag ratio) of the content of the bismuth-containing particles to the content of the silver-containing particles in the electrode forming composition is preferably 0.30 to 1.40. It is more preferably 0.35 to 1.30, further preferably 0.40 to 1.20, and even more preferably 0.45 to 1.10.
  • the composition for forming an electrode contains glass particles, and contains glass particles containing phosphorus as glass particles (hereinafter, also referred to as phosphorus-containing glass particles).
  • the phosphorus-containing glass include glass particles containing phosphorus oxide ( P2O 5 )
  • phosphate glass is preferable.
  • the phosphate glass means a glass containing phosphorus oxide ( P2O 5 ) as a network-forming oxide.
  • the content of phosphorus oxide is preferably 20.0% by mass or more, preferably 30.0% by mass or more, from the viewpoint of the function of the glass. Is more preferable, and 35.0% by mass or more is further preferable.
  • the content of phosphorus oxide (P 2 O 5 ) is preferably 50.0% by mass or less, more preferably 45.0% by mass or less, and further preferably 40.0% by mass or less. preferable.
  • the phosphorus-containing glass particles may contain phosphorus oxide and an oxide other than phosphorus oxide.
  • oxides other than phosphorus oxide contained in the glass constituting the phosphorus-containing glass particles include silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), boron oxide (B 2 O 3 ), and vanadium oxide (B 2 O 3).
  • V 2 O 5 potassium oxide (K 2 O), bismuth oxide (Bi 2 O 3 ), sodium oxide (Na 2 O), lithium oxide (Li 2 O), barium oxide (BaO), strontium oxide (SrO) , Calcium oxide (CaO), magnesium oxide (MgO), beryllium oxide (BeO), zinc oxide (ZnO), cadmium oxide (CdO), tin oxide (SnO), zirconium oxide (ZrO 2 ), tungsten oxide (WO 3 ) , Molybdenum oxide (MoO 3 ), Lantern oxide (La 2 O 3 ), Niobide oxide (Nb 2 O 3 ), Tantal oxide (Ta 2 O 5 ), Yttrium oxide (Y 2 O 3 ), Titanium oxide (TIO 2 ) , Germanium oxide (GeO 2 ), tellurium oxide (TeO 2 ), yttrium oxide (Lu 2 O 3 ), antimony oxide (Sb 2 O 3 ), copper oxide (CuO), iron
  • the phosphorus-containing glass particles preferably contain at least one selected from vanadium oxide, aluminum oxide, tin oxide and zinc oxide, more preferably tin oxide, and tin-containing phosphate glass (P 2 O 5 ⁇ . SnO system) and the like are given as preferable examples.
  • glass having such a composition the reliability of the aluminum / silver laminated electrode in a high temperature and high humidity environment tends to be further improved.
  • the tin oxide content is preferably 20.0% by mass or more, more preferably 30.0% by mass or more, and 40.0% by mass or more. Is more preferable.
  • the content of tin oxide is preferably 80.0% by mass or less, more preferably 70.0% by mass or less, and further preferably 60.0% by mass or less. It is preferable that the phosphorus-containing glass particles do not contain boron oxide, or the content of boron oxide is lower than the content of phosphorus oxide.
  • the phosphorus-containing glass particles have a volume average particle diameter of 10.0 ⁇ m to 50.0 ⁇ m, preferably 15.0.0 ⁇ m to 40.0 ⁇ m, and more preferably 15.0 ⁇ m to 35.0 ⁇ m. It is more preferably 15.0 ⁇ m to 25.0 ⁇ m.
  • the volume average particle diameter of the phosphorus-containing glass particles is 10.0 ⁇ m or more, an uneven shape due to the phosphorus-containing glass particles is formed on the surface of the silver electrode obtained by heat-treating the electrode-forming composition. As a result, the contact between the wiring material and the silver electrode becomes a point contact, so that the stress is relaxed and the reliability in a high temperature and high humidity environment is improved.
  • the volume average particle diameter of the phosphorus-containing glass particles is 50.0 ⁇ m or less, the dispersibility of the phosphorus-containing glass particles in the electrode forming composition is good, and the uneven shape formed on the surface of the silver electrode is formed. The bias of the distribution is suppressed.
  • the volume average particle size of the phosphorus-containing glass particles is measured in the same manner as the volume average particle size of the silver-containing particles.
  • the electrode forming composition preferably further contains boron-containing glass particles (hereinafter, also referred to as boron-containing glass particles), and more preferably contains borate glass.
  • the borate glass means a glass containing boron oxide (B 2 O 3 ) as a network-forming oxide.
  • the electrode forming composition further contains boron-containing glass particles
  • the electrode forming composition contains phosphorus-containing glass particles and boron-containing glass particles, respectively, and the electrode forming composition contains phosphorus and boron.
  • the case where the glass particles are contained is included.
  • the composition for forming an electrode contains phosphorus-containing glass particles and boron-containing glass particles, respectively, and a phosphate salt. It is more preferable to contain glass particles and borate glass particles, respectively.
  • the reason why the power generation performance of the solar cell element is improved by containing the boron-containing glass particles in the electrode forming composition is not necessarily clear, but it is considered as follows.
  • the bismuth oxide phase formed by the bismuth-containing particles may dissolve the SiNX film for protecting the passivation film on the surface of the substrate on which the aluminum particle-containing film is formed, thereby reducing the passivation effect.
  • the composition for forming an electrode contains boron-containing glass particles, the boron-containing glass particles are melted by heat treatment, and a part of the melt reaches the surface of the substrate on which the aluminum particle-containing film is arranged.
  • the bismuth concentration of the bismuth oxide phase near the surface of the substrate is lowered, the dissolution of the SiNX film by the bismuth oxide phase is suppressed, and the power generation performance is maintained well.
  • the content of the phosphorus-containing glass particles with respect to the total of the phosphorus-containing glass particles and the boron-containing glass particles is 3.0% by mass to 50. It is preferably 0% by mass, more preferably 3.5% by mass to 45.0% by mass, still more preferably 4.0% by mass to 40.0% by mass.
  • the content of the phosphorus-containing glass particles is 3.0% by mass or more with respect to the total of the phosphorus-containing glass particles and the boron-containing glass particles.
  • the reliability of the aluminum / silver laminated electrode in a high temperature and high humidity environment is more effective. It tends to improve.
  • the content of the phosphorus-containing glass particles to 50.0% by mass or less, the dissolution of the SiNX film by the bismuth oxide phase is more effectively suppressed, and the power generation performance is maintained well.
  • the content of boron oxide as an oxide is preferably 3.0% by mass or more, preferably 5.0% by mass, from the viewpoint of the function of the glass. The above is more preferable, and 10.0% by mass or more is further preferable.
  • the content of boron oxide is preferably 25.0% by mass or less, more preferably 20.0% by mass or less, and further preferably 15.0% by mass or less.
  • the boron-containing glass particles may contain boron oxide and an oxide other than boron oxide.
  • the oxide other than boron oxide contained in the glass constituting the boron-containing glass particles include oxides exemplified as oxides that may be contained in the glass constituting the phosphorus-containing glass particles. It is preferable that the boron-containing glass particles do not contain phosphorus oxide or the content of phosphorus oxide is lower than the content of boron oxide.
  • the boron-containing glass particles preferably contain at least one selected from silicon oxide, aluminum oxide, zinc oxide, bismuth oxide, copper oxide and lithium oxide, more preferably bismuth oxide-containing borate glass. (B 2 O 3 -Bi 2 O 3 system) and the like are given as preferable examples. Glass having such a composition has a low softening point, and the adhesion of the electrode obtained after the heat treatment to the substrate tends to be further improved.
  • the content of bismuth oxide is preferably 75.0% by mass or more, more preferably 80.0% by mass or more, and 85.0% by mass or more. Is more preferable.
  • the content of bismuth oxide is preferably 97.0% by mass or less, more preferably 95.0% by mass or less, and further preferably 90.0% by mass or less.
  • the particle size of the boron-containing glass particles is not particularly limited, but the volume average particle size is preferably 0.2 ⁇ m to 10.0 ⁇ m, and more preferably 0.5 ⁇ m to 8.0 ⁇ m.
  • the volume average particle diameter of the boron-containing glass particles is 0.2 ⁇ m or more, the workability at the time of producing the electrode electrode forming composition is improved.
  • the volume average particle diameter of the boron-containing glass particles is 10.0 ⁇ m or less, the dispersibility in the electrode forming composition is improved, and the uniformity of the distribution of boron in the aluminum / silver laminated electrode is improved.
  • the volume average particle size of the boron-containing glass particles is measured in the same manner as the volume average particle size of the silver-containing particles.
  • the glass particles contained in the electrode forming composition may be only one kind or two or more kinds.
  • all of the glass particles may contain phosphorus, or at least one of the glass particles may contain phosphorus.
  • lead-free glass containing substantially no lead examples include lead-free glass described in paragraphs 0024 to 0025 of JP-A-2006-313744, lead-free glass described in JP-A-2009-188281, and the like.
  • the softening point of the glass particles is not particularly limited, but is preferably 650 ° C or lower, and more preferably 500 ° C or lower.
  • the softening point of the glass particles is measured by a conventional method using a thermomechanical analyzer (TMA).
  • the shape of the glass particles is not particularly limited, and may be substantially spherical, flat, block-shaped, plate-shaped, scale-shaped, or the like. From the viewpoint of wettability with silver-containing particles and bismuth-containing particles, the shape of the glass particles is preferably substantially spherical, flat or plate-shaped.
  • the content of the glass particles contained in the electrode forming composition (the total content of the phosphorus-containing glass particles and the phosphorus-free glass particles when they are contained) is 1.0% by mass of the entire electrode forming composition. It is preferably from 15.0% by mass, more preferably from 3.5% by mass to 14.0% by mass, and even more preferably from 4.0% by mass to 12.0% by mass.
  • the content of the glass particles is 1.0% by mass of the entire electrode forming composition. It is preferably from 15.0% by mass, more preferably from 3.5% by mass to 14.0% by mass, and even more preferably from 4.0% by mass to 12.0% by mass.
  • the mass ratio (Bi / G ratio) of the content of the bismuth-containing particles to the content of the glass particles contained in the electrode forming composition is preferably 0.5 to 15.0, preferably 1.0 to 12. It is more preferably 0, and even more preferably 1.5 to 10.0.
  • the electrode forming composition may contain at least one of a solvent and a resin.
  • a solvent and a resin By containing at least one of a solvent and a resin in the electrode forming composition, the liquidity (viscosity, surface tension, etc.) of the electrode forming composition is adjusted within a range suitable for the application method when applied to a substrate or the like. can do.
  • the solvent or resin contained in the electrode forming composition may be only one type or two or more types, respectively.
  • the solvent examples include hydrocarbon solvents such as hexane, cyclohexane and toluene, halogenated hydrocarbon solvents such as dichloroethylene, dichloroethane and dichlorobenzene, and cyclic compounds such as tetrahydrofuran, furan, tetrahydropyran, pyran, dioxane, 1,3-dioxolane and trioxane.
  • hydrocarbon solvents such as hexane, cyclohexane and toluene
  • halogenated hydrocarbon solvents such as dichloroethylene, dichloroethane and dichlorobenzene
  • cyclic compounds such as tetrahydrofuran, furan, tetrahydropyran, pyran, dioxane, 1,3-dioxolane and trioxane.
  • Ether solvent amide solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, sulfoxide solvent such as dimethylsulfoxide and diethylsulfoxide, ketone solvent such as acetone, methylethylketone, diethylketone, cyclohexanone, ethanol, 2-propanol, Alcohol solvents such as 1-butanol and diacetone alcohol, 2,2,4-trimethyl-1,3-pentanediol monoacetate, 2,2,4-trimethyl-1,3 pentanediol monopropionate, 2,2 , 4-trimethyl-1,3-pentanediol monobutylate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate and other polyvalent alcohol ester solvents, butyl cell solve, diethylene glycol monobutyl ether, diethylene glycol diethyl ether and other polyvalent alcohols.
  • Examples thereof include ether solvents, ⁇ -terpineol, ⁇ -terpineol, milsen, aloosimene, limonene, dipentene, ⁇ -pinene, ⁇ -pinene, tarpineol, carboxylic, osimene, ferlandren and the like.
  • the solvent is selected from the group consisting of an ester solvent of a polyhydric alcohol, a terpene solvent and an ether solvent of a polyhydric alcohol from the viewpoint of imparting property (for example, coatability or printability) of the composition for forming an electrode. It is preferable to contain at least one kind, and it is more preferable to contain at least one kind selected from the group consisting of an ester solvent of a polyhydric alcohol and a terpene solvent.
  • the resin is not particularly limited as long as it is a resin that can be thermally decomposed by heat treatment, and may be a natural polymer or a synthetic polymer.
  • cellulose resins such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose and nitrocellulose, polyvinyl alcohol compounds, polyvinyl pyrrolidone compounds, acrylic resins, vinyl acetate-acrylic acid ester copolymers, butyral resins such as polyvinyl butyral, and phenol-modified alkyds.
  • examples thereof include resins, alkyd resins such as castor oil fatty acid-modified alkyd resins, epoxy resins, phenolic resins, and rosin ester resins.
  • the resin contains at least one selected from the group consisting of cellulose resin and acrylic resin.
  • the weight average molecular weight of the resin is not particularly limited. Among them, the weight average molecular weight of the resin is preferably 5,000 to 500,000, more preferably 10,000 to 300,000. When the weight average molecular weight of the resin is 5,000 or more, the increase in the viscosity of the electrode forming composition tends to be suppressed. It can be considered that this is because, for example, the three-dimensional repulsive action when the resin is adsorbed on the particles is sufficient, and the aggregation of these resins is suppressed.
  • the weight average molecular weight of the resin is 500,000 or less
  • the resins are suppressed from aggregating with each other in the solvent, and the increase in the viscosity of the electrode forming composition tends to be suppressed.
  • the weight average molecular weight of the resin is 500,000 or less
  • the combustion temperature of the resin is too high and it is suppressed that the composition for forming the electrode is not burned and remains as a foreign substance when the composition is heat-treated, and the resistance is lower. There is a tendency to be able to form various electrodes.
  • the weight average molecular weight is obtained by converting the molecular weight distribution measured by GPC (gel permeation chromatography) using a standard polystyrene calibration curve.
  • the calibration curve is approximated in three dimensions using a 5-sample set of standard polystyrene (PStQuick MP-H, PStQuick B, Tosoh Corporation).
  • PStQuick MP-H standard polystyrene
  • the content of the solvent and the resin can be selected according to the desired liquid physical characteristics of the electrode forming composition, the type of the solvent and the resin to be used, and the like.
  • the total content of the solvent and the resin is preferably 3.0% by mass to 70.0% by mass, and preferably 20.0% by mass to 55.0% by mass, based on the entire composition for forming an electrode. More preferably, it is 30.0% by mass to 50.0% by mass.
  • the total content of the solvent and the resin is within the above range, the aptitude for applying the electrode-forming composition to the substrate becomes good, and an electrode having a desired width and height can be more easily formed. Tend to be able to.
  • the content ratio of the solvent and the resin shall be appropriately selected according to the type of the solvent and the resin used so that the electrode forming composition has the desired liquid physical characteristics. Can be done.
  • the electrode-forming composition includes silver-containing particles, bis-mass-containing particles, and glass from the viewpoints of the sintering property of silver-containing particles, the diffusion barrier property of bismuth-containing particles, and the effect of improving the strength and adhesion of aluminum electrodes by glass particles.
  • the total content of the particles is preferably 30.0% by mass or more and 97.0% by mass or less, and more preferably 45.0% by mass or more and 80.0% by mass or less of the entire composition for forming an electrode. It is more preferably 50.0% by mass or more and 70.0% by mass or less.
  • the electrode-forming composition may further contain other components usually used in the art.
  • other components include plasticizers, dispersants, surfactants, thickeners, inorganic binders, metal oxides (excluding bismuth oxide), ceramics, organic metal compounds and the like.
  • the method for producing the electrode-forming composition is not particularly limited. For example, it can be produced by dispersing and mixing silver-containing particles, bismuth-containing particles, glass particles and other components used as necessary.
  • the method of dispersion and kneading is not particularly limited, and can be selected and applied from commonly used methods.
  • the aluminum / silver laminated electrode according to the embodiment of the present disclosure contains the heat-treated product of the above-mentioned electrode forming composition, and contains a first electrode containing aluminum and silver arranged on the first electrode.
  • the first electrode is an aluminum / silver laminated electrode including a second electrode containing a bismuth oxide phase and a glass phase containing phosphorus.
  • the first electrode contains the bismuth oxide phase and the glass phase can be confirmed by using a transmission electron microscope.
  • the presence of the bismuth oxide phase can be confirmed by the presence of lattice stripes (atomic arrangement) of the crystal Bi 2 O 3
  • the presence of the glass phase can be confirmed by the presence of a structure peculiar to amorphous.
  • the magnification of the transmission electron microscope is set to, for example, several hundred thousand times.
  • the glass phase contained in the first electrode further contains boron.
  • the aluminum / silver laminated electrode having the above configuration is preferably arranged on the substrate constituting the solar cell element, and more preferably arranged on the side corresponding to the back surface of the solar cell element.
  • “on the substrate” also includes a film such as a passivation film formed on the surface of the substrate and a protective film of the passivation film.
  • the thickness of the first electrode containing aluminum (or the minimum thickness if the thickness is not constant) may be, for example, in the range of 0.5 ⁇ m to 50.0 ⁇ m.
  • the thickness of the second electrode containing silver (or the minimum thickness if the thickness is not constant) may be, for example, in the range of 0.5 ⁇ m to 30.0 ⁇ m.
  • FIG. 1 is a schematic cross-sectional view of a back surface electrode of a solar cell element having a PERC structure produced by using an electrode forming composition. As shown in FIG.
  • a passivation film 18 and a protective film 19 are formed on the surface of the semiconductor substrate 1 in this order, and an aluminum electrode (also referred to as an aluminum particle sintered portion) 5 and aluminum are formed on the passivation film 18 and the protective film 19 (SiN X) in this order.
  • the silver laminated electrode 8 is formed.
  • the aluminum / silver laminated electrode 8 includes a portion where the aluminum electrode and the silver electrode (also referred to as a silver particle sintered portion) are laminated.
  • a silver particle sintered portion may be formed on the outermost surface of the aluminum / silver laminated electrode 8.
  • the aluminum electrode 5 and the aluminum electrode constituting the aluminum / silver laminated electrode 8 may be formed at the same time.
  • the method for producing an aluminum / silver laminated electrode using the electrode forming composition is not particularly limited. For example, a step of forming an aluminum particle-containing film on a semiconductor substrate, a step of applying an electrode-forming composition onto the aluminum particle-containing film and drying it as necessary, and forming an aluminum particle-containing film and an electrode. Examples thereof include a step of heat-treating the composition for use and a method of carrying out the steps in this order.
  • the aluminum particle-containing film may be formed on a semiconductor substrate on which a passivation film and a protective film (SiN X ) are formed. Further, the aluminum particle-containing film may be formed by drying the aluminum electrode forming composition applied on the semiconductor substrate.
  • the semiconductor substrate may be a silicon (Si) substrate.
  • Examples of the method for applying the aluminum electrode forming composition when the aluminum particle-containing film is formed on the semiconductor substrate by using the aluminum electrode forming composition include a screen printing method, an inkjet method, a dispenser method and the like. The screen printing method is preferable from the viewpoint of productivity.
  • heat treatment conditions usually used in the art can be applied.
  • Examples of the method for applying the electrode forming composition onto the aluminum particle-containing film include a screen printing method, an inkjet method, a dispenser method, and the like, and the screen printing method is preferable from the viewpoint of productivity.
  • the electrode forming composition When the electrode forming composition is applied onto the aluminum particle-containing film by a screen printing method, the electrode forming composition is preferably in the form of a paste.
  • the paste-like electrode-forming composition preferably has a viscosity in the range of 20 Pa ⁇ s to 1000 Pa ⁇ s. The viscosity of the electrode forming composition is measured at 25 ° C. using a Brookfield HBT viscometer.
  • the amount of the electrode-forming composition applied to the aluminum particle-containing film can be appropriately selected according to the size of the electrode to be formed.
  • the amount of the electrode-forming composition applied can be 1.0 mg / cm 2 to 20.0 mg / cm 2 , preferably 2.0 mg / cm 2 to 15.0 mg / cm 2 . ..
  • the heat treatment conditions for forming the aluminum / silver laminated electrode using the electrode forming composition the heat treatment conditions usually used in the art can be applied.
  • the heat treatment temperature a range of 700 ° C. to 900 ° C., which is used when manufacturing a general crystalline silicon solar cell element, can be preferably used.
  • the heat treatment time can be appropriately selected according to the heat treatment temperature, and can be, for example, 1 second to 20 seconds.
  • any one that can be heated to the above temperature can be appropriately adopted, and examples thereof include an infrared heating furnace, a tunnel furnace, and the like.
  • the infrared heating furnace is highly efficient because electric energy is input to the heating material in the form of electromagnetic waves and converted into heat energy, and rapid heating in a shorter time is possible. Furthermore, since there are few products due to combustion and non-contact heating is used, it is possible to suppress contamination of the generated electrodes.
  • the tunnel furnace automatically and continuously transports the sample from the inlet to the outlet and heat-treats it, it is possible to heat-treat more uniformly by classifying the furnace body and controlling the transport speed. From the viewpoint of the power generation performance of the solar cell element, it is preferable to heat-treat in a tunnel furnace.
  • FIGS. 2A to 2C An example of a typical method for manufacturing an aluminum / silver laminated electrode is shown in FIGS. 2A to 2C.
  • the paste-like aluminum electrode forming composition 2 is applied to one surface of the semiconductor substrate 1 on which the passivation film 18 and the protective film (SiN X ) 19 are formed by a screen printing method. do. This is heated at a temperature of about 150 ° C. to remove the solvent in the composition 2 for forming an aluminum electrode.
  • the aluminum particle-containing film 3 is formed on the semiconductor substrate 1 on which the passivation film 18 and the protective film ( SiNX ) 19 are formed.
  • the electrode-forming composition 4 is applied to a desired region on the aluminum particle-containing film 3, heated at a temperature of about 150 ° C., and dried.
  • the electrode forming composition 4 When the electrode forming composition 4 is in the form of a paste, it is applied by a screen printing method in the same manner as the aluminum electrode forming composition 2. Then, this is heat-treated under the above-mentioned conditions. As a result, as shown in FIG. 2C, the aluminum / silver laminated electrode 8 is formed on the semiconductor substrate 1 on which the passivation film 18 and the protective film (SiN X ) 19 are formed.
  • the aluminum / silver laminated electrode 8 has a silver particle sintered portion 7 arranged on the outermost surface, and is between the silver particle sintered portion 7 and the semiconductor substrate 1 on which the passion film 18 and the protective film (SiN X ) 19 are formed.
  • the aluminum particle sintered portion / bismuth oxide phase mixing portion 6 is arranged in the room.
  • FIG. 3 is an enlarged view of the formed portion of the aluminum / silver laminated electrode in FIG. 2C.
  • the aluminum particle sintered portion / bismuth oxide phase mixing portion 6 includes an aluminum particle sintered portion 5 and a bismuth oxide phase 9 filled in a void portion of the aluminum particle sintered portion 5.
  • the reason why the aluminum particle sintered portion / bismuth oxide phase mixing portion 6 has such a configuration is that, as described above, a part or the whole of the bismuth-containing particles in the electrode forming composition 4 is heat-treated to form an aluminum particle-containing film. This is to move to 3.
  • the bismuth oxide phase 9 may be arranged so as to separate the silver particle sintered portion 7 and the aluminum particle sintered portion 5, and the aluminum particles in the aluminum particle sintered portion 5 and the silver particle sintered portion 7 May be partially formed where the particles are in contact with each other.
  • the bismuth oxide phase 9 is arranged so as to separate the silver particle sintered portion 7 and the aluminum particle sintered portion 5 to the extent that excessive mutual diffusion between the aluminum particles and the silver particles is suppressed. preferable.
  • the solar cell element according to the embodiment of the present disclosure is aluminum / silver including a semiconductor substrate, a passivation film provided on the semiconductor substrate, and a heat-treated product of the above-mentioned electrode forming composition provided on the passivation film. It is a solar cell element having a laminated electrode.
  • the solar cell element may be provided with a protective film for protecting the passivation film provided on the semiconductor substrate, if necessary.
  • the aluminum / silver laminated electrode of the solar cell element may be provided on the back surface of the semiconductor substrate. Further, the solar cell element may have a PERC structure.
  • FIGS. 4, 5A, 5B, 6A, 6B and 6C An example of a typical solar cell element is shown in FIGS. 4, 5A, 5B, 6A, 6B and 6C.
  • FIG. 4 is a schematic plan view of the light receiving surface side of the solar cell element.
  • the light receiving surface electrode 14 shown in FIG. 4 is generally formed by using a silver electrode paste. Specifically, a silver electrode paste is applied onto the antireflection film 13 in a desired pattern, dried, and then heat-treated at about 700 ° C. to 900 ° C. in the atmosphere to form the paste.
  • FIG. 5A is a schematic plan view of the back surface of the solar cell element.
  • An aluminum electrode 5 is formed on the entire surface of the back surface of the solar cell element shown in FIG. 5A.
  • FIG. 5B is a schematic plan view of the back surface of the solar cell element when the aluminum finger electrode 20 and the aluminum bus bar electrode 21 are formed on a part of the back surface.
  • the electrode forming composition is applied in a desired pattern and dried. Next, this is heat-treated at about 700 ° C. to 900 ° C. in the atmosphere to form an aluminum / silver laminated electrode. The heat treatment may be performed collectively with the heat treatment for forming the light receiving surface electrode 14 described above.
  • an n + type diffusion layer 12 is formed near the surface of one surface of the semiconductor substrate 1, and an output extraction electrode 14 and reflection are formed on the n + type diffusion layer 12.
  • the prevention film 13 is formed.
  • FIG. 6A is a cut surface of the AA'part in FIG. 5A.
  • the back surface has the structure shown in FIG. 6A.
  • FIG. 6B is a cut surface of the BB'part in FIG. 5B. If the BB'cross section does not cross the opening of the backside passivation membrane, the backside has the structure shown in FIG. 6B.
  • FIG. 6C is a cut surface of the CC'part in FIG. 5B. When the CC'cross section crosses the opening of the back surface passivation film (aluminum finger electrode 20), the back surface has the structure shown in FIG. 6C.
  • the glass particles contained in the silver electrode paste forming the light receiving surface electrode 14 by heat treatment react (fire through) with the antireflection film 13 to cause a light receiving surface.
  • the electrode 14 and the n + type diffusion layer 12 are electrically connected (omic contact).
  • the aluminum in the aluminum electrode 5, the aluminum finger electrode 20, or the aluminum bus bar electrode 21 is diffused to a part of the back surface of the semiconductor substrate 1 (the portion where the back surface passivation film film-forming portion is removed by a laser or the like) by heat treatment.
  • the p + type diffusion layer 15 an ohmic contact is partially formed between the semiconductor substrate 1 and the aluminum electrode 15.
  • the shape of the glass particles was determined by observing using a scanning electron microscope (Hitachi High-Technologies Corporation, TM-1000).
  • the volume average particle diameter (D50%) of the glass particles was calculated using a laser scattering diffraction method particle size distribution measuring device (Beckman Coulter, LS 13, 320 type, measuring wavelength: 632 nm).
  • the softening point of the glass particles was determined from a differential thermal (DTA) curve measured using a differential thermal / thermogravimetric simultaneous measuring device (Shimadzu Seisakusho Co., Ltd., DT-60H). Specifically, in the DTA curve, the softening point can be estimated from the endothermic portion.
  • Example 1 (1) Preparation of Phosphate Glass Particles Phosphorus oxide (P 2 O 5 ) 38.0% by mass, tin oxide (SnO) 57.9% by mass, zinc oxide (ZnO) 3.5% by mass and aluminum oxide (Al). 2 O 3 ) Phosphate glass composed of 1.5% by mass was obtained. The softening point of the obtained phosphate glass was 340 ° C. Using phosphate glass, phosphate glass particles having a volume average particle diameter of 15.0 ⁇ m were obtained. The shape of the particles was substantially spherical.
  • composition for forming electrodes The following components were mixed using a roll mill (IMEX Co., Ltd., BR-150HCV) to prepare a paste-like electrode-forming composition.
  • Silver particles (volume average particle diameter: 0.6 ⁇ m, silver content: 99.9 mass%): 29.4 parts by mass Metal bismuth particles (volume average particle diameter: 1.5 ⁇ m, bismus content: 99.5 mass%) ): 29.1 parts by mass Phosphorate glass particles: 0.5 parts by mass Borate glass particles: 2.5 parts by mass Terpineol: 30.0 parts by mass Ethylcellulose (Nisshin Kasei Co., Ltd., STD-10): 5 .0 parts by mass
  • n + type diffusion layer, texture and antireflection (SiN X ) film are formed on the light receiving surface, and a passivation film is formed on the surface opposite to the light receiving surface (hereinafter, also referred to as “back surface”).
  • a 160 ⁇ m-thick p-type silicon single crystal substrate in which an aluminum oxide (AlO X ) film and a protective film (SiN X ) film were formed in this order was prepared and cut into a size of 158.75 mm ⁇ 158.75 mm. ..
  • the portion of the passivation film / protective film on the back surface where the aluminum finger electrode was formed was removed by a laser to expose the silicon substrate.
  • a composition for forming a silver electrode (manufactured by DuPont, PV20) containing silver particles and lead glass particles is arranged on the light receiving surface so as to have an electrode pattern as shown in FIG. 4 (actually, the light receiving surface output extraction electrode 14).
  • the number of the particles was set to 9), and the particles were given by screen printing. This was heated in a tunnel furnace (Despatch) heated under the conditions of a set temperature of 250 ° C. and a transport speed of 240 inches / minute, and the solvent was removed by evaporation.
  • the aluminum electrode forming composition (Ruxing, RX8401) and the electrode forming composition obtained above are subjected to screen printing to form an electrode pattern as shown in FIG. 5B.
  • the number of aluminum bus bar electrodes 21 was set to 9, and the aluminum / silver laminated electrodes were formed at 6 positions per aluminum bus bar electrode 21).
  • the composition for forming an aluminum electrode was printed in the shape of a fine line pattern of the aluminum finger electrode 20 and the aluminum bus bar electrode 21 and dried to form an aluminum particle-containing film. Then, the composition for forming an electrode was printed on the aluminum particle-containing film. The formed portion of the aluminum finger electrode was aligned with the exposed portion of the silicon substrate.
  • the printing conditions of the composition for forming an aluminum electrode were adjusted so that the thickness of the aluminum electrode after the heat treatment was 30 ⁇ m.
  • the electrode-forming composition was printed using a pattern in which pad shapes having a size of 1.6 mm ⁇ 8.0 mm were arranged so that the coating amount was 8.0 mg / cm 2 .
  • the mixture is heated in a tunnel furnace (Despatch) under the conditions of a set temperature of 250 ° C. and a transport speed of 240 inches / minute, and the solvent is evaporated. Removed.
  • Example 2 a composition for forming an electrode was prepared in the same manner as in Example 1 except that the volume average particle diameter of the phosphate glass particles was 25.0 ⁇ m, and a solar cell element was produced.
  • Example 3 a composition for forming an electrode was prepared in the same manner as in Example 1 except that the volume average particle diameter of the phosphate glass particles was 35.0 ⁇ m, and a solar cell element was produced.
  • Example 4 a composition for forming an electrode was prepared in the same manner as in Example 1 except that the volume average particle diameter of the phosphate glass particles was 10.0 ⁇ m, and a solar cell element was produced.
  • Example 5 a composition for forming an electrode was prepared in the same manner as in Example 1 except that the volume average particle diameter of the phosphate glass particles was 50.0 ⁇ m, and a solar cell element was produced.
  • Example 1 a composition for forming an electrode was prepared in the same manner as in Example 1 except that the volume average particle diameter of the phosphate glass particles was 5.0 ⁇ m, and a solar cell element was produced.
  • Example 2 a composition for forming an electrode was prepared in the same manner as in Example 1 except that the volume average particle diameter of the phosphate glass particles was 60.0 ⁇ m, and a solar cell element was produced.
  • FIG. 7 An image of the cross section of the aluminum / silver laminated electrode produced in Example 1 taken with a scanning electron microscope is shown in FIG. 7, and the EDX analysis result of this image is shown in FIG. 8, respectively.
  • a silver particle sintered portion is arranged on the aluminum particle sintered portion as shown in FIG. 7 on the back surface of the solar cell elements manufactured in Examples 1 to 5 and Comparative Examples 1 and 2.
  • the aluminum / silver laminated electrode was formed.
  • a silver particle sintered portion was formed on the outermost surface of the aluminum / silver laminated electrode, and the void portion of the aluminum particle sintered portion was formed.
  • the bismuth oxide phase was formed respectively. Further, a part of the bismuth oxide phase reached the surface of the substrate in contact with the aluminum / silver laminated electrode.
  • the one in which the wiring material is connected to the backside output take-out electrode is used to change the resistance value of the electrode part in the high temperature and high humidity environment.
  • a wiring material (Ulbrich, Multi-Tabbing wire, Sn-Pb-based eutectic solder coating, Cu core material having a diameter of 0.4 mm) is placed on the back surface output take-out electrode and placed on the wiring material. It was connected by pressing a soldering iron from the soldering iron to melt the solder.
  • the volume average particle diameter of the phosphorus-containing glass particles is 10.0 ⁇ m or more.
  • Comparative Examples 1 and 2 which are outside the range of 50.0 ⁇ m or less, the rate of increase in the resistance value in a high temperature and high humidity environment was small, and excellent reliability was shown.

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Abstract

A composition for forming an electrode, said composition containing silver-containing particles, bismuth-containing particles and glass particles, wherein: the glass particles include phosphorus-containing glass particles; and the volume average particle diameter of the phosphorus-containing glass particles is from 10.0 μm to 50.0 μm.

Description

電極形成用組成物、太陽電池素子及びアルミニウム／銀積層電極Electrode forming compositions, solar cell elements and aluminum / silver laminated electrodes
　本開示は、電極形成用組成物、太陽電池素子及びアルミニウム／銀積層電極に関する。 The present disclosure relates to an electrode forming composition, a solar cell element, and an aluminum / silver laminated electrode.
　近年、地球温暖化、大気汚染等をはじめとする環境問題への関心が高まっている。中でも地球温暖化問題の対策としては、化石燃料に替わる再生可能エネルギーの需要が高まっている。再生可能エネルギーとしては、太陽光、地熱、風力、波力、潮力、バイオマス等が挙げられる。特に太陽光発電は、無尽蔵な太陽光エネルギーを活用すると同時に、発電の際に二酸化炭素を排出しないクリーンな自然エネルギーとして注目を集め、深刻化するエネルギー問題の有効な解決策として期待されている。 In recent years, there has been increasing interest in environmental issues such as global warming and air pollution. Above all, as a countermeasure against the global warming problem, the demand for renewable energy to replace fossil fuels is increasing. Examples of renewable energy include solar power, geothermal power, wind power, wave power, tidal power, and biomass. In particular, photovoltaic power generation is expected to be an effective solution to the growing energy problem, attracting attention as a clean natural energy that does not emit carbon dioxide during power generation while utilizing inexhaustible solar energy.
　太陽電池としては、半導体基板としてシリコン（Ｓｉ）基板を用いた結晶シリコン系太陽電池が一般的である。Ｓｉ基板を用いた太陽電池セル（太陽電池素子）の受光面及び裏面（受光面と逆の面）のそれぞれには、キャリアを回収するための集電用電極と、キャリアを出力として取り出すための出力取出し電極（バスバー電極）とが形成される。受光面の集電用電極は特に、フィンガー電極と呼ばれる。受光面電極の形成には、銀（Ａｇ）電極形成用組成物が用いられ、フィンガー電極及びバスバー電極部の印刷は、個別又は一括で行われる。裏面については、バスバー電極の形成は銀電極形成用組成物が、集電用電極にはアルミニウム（Ａｌ）電極形成用組成物がそれぞれ用いられる。各電極形成用組成物には、導電性金属粒子、ガラス粒子及び種々の添加剤等が含有される。 As a solar cell, a crystalline silicon solar cell using a silicon (Si) substrate as a semiconductor substrate is generally used. On each of the light receiving surface and the back surface (the surface opposite to the light receiving surface) of the solar cell (solar cell element) using the Si substrate, a current collecting electrode for collecting carriers and a carrier for taking out as an output are used. An output take-out electrode (bus bar electrode) is formed. The current collecting electrode on the light receiving surface is particularly called a finger electrode. A composition for forming a silver (Ag) electrode is used for forming the light receiving surface electrode, and printing of the finger electrode and the bus bar electrode portion is performed individually or collectively. On the back surface, a composition for forming a silver electrode is used for forming the bus bar electrode, and a composition for forming an aluminum (Al) electrode is used for the electrode for collecting current. Each electrode-forming composition contains conductive metal particles, glass particles, various additives and the like.
　受光面電極及び裏面バスバー電極を形成するための銀電極形成用組成物には、前記導電性金属粒子として、銀粒子が一般的に用いられている。この理由として、銀の体積抵抗率が低い（１．４７×１０－６Ωｃｍ）こと、上記熱処理条件において銀粒子が自己還元して焼結すること、銀粒子とシリコン基板が良好なオーミックコンタクトを形成すること及び銀粒子から形成された電極がはんだ材料の濡れ性に優れ、太陽電池素子間を電気的に接続する配線材料（タブ線等）を好適に接着可能であることが挙げられる。 Silver particles are generally used as the conductive metal particles in the composition for forming a silver electrode for forming the light receiving surface electrode and the back surface bus bar electrode. The reasons for this are that the volumetric resistance of silver is low (1.47 × 10-6 Ωcm), the silver particles are self-reduced and sintered under the above heat treatment conditions, and the silver particles and the silicon substrate have good ohmic contact. It is mentioned that the electrode formed from the silver particles has excellent wettability of the solder material, and the wiring material (tab wire or the like) for electrically connecting the solar cell elements can be suitably bonded.
　アルミニウム電極形成用組成物を用いて裏面の集電用電極を形成する際、アルミニウム電極形成用組成物中のアルミニウムが、シリコンとの共晶反応を経て裏面の表面に高濃度拡散層（ｐ＋－Ｓｉ層、Ｂａｃｋ　Ｓｕｒｆａｃｅ　Ｆｉｅｌｄ；ＢＳＦ）を形成する。これにより、ｐ型シリコン基板中の少数キャリアである電子を受光面側に追い返す構造が付与され、キャリア再結合の確率を低減することができる。
　しかしながら、従来のアルミニウム電極形成用組成物を用いた裏面電極／ＢＳＦ構造では、裏面の少数キャリア再結合速度は３×１０３ｃｍ／ｓ程度と速く、太陽電池素子の発電性能を低下させる要因になり得る。 When the electrode for collecting current on the back surface is formed using the composition for forming an aluminum electrode, the aluminum in the composition for forming an aluminum electrode undergoes a eutectic reaction with silicon and a high concentration diffusion layer (p + ) is formed on the front surface of the back surface. -Si layer, Back Surface Field; BSF) is formed. As a result, a structure is provided in which electrons, which are minority carriers in the p-type silicon substrate, are repelled to the light receiving surface side, and the probability of carrier recombination can be reduced.
However, in the back surface electrode / BSF structure using the conventional aluminum electrode forming composition, the minority carrier recombination rate on the back surface is as fast as about 3 × 10 3 cm / s, which is a factor that lowers the power generation performance of the solar cell element. Can be.
　裏面再結合損失の低減策として、ＰＥＲＣ（Ｐａｓｓｉｖａｔｅｄ　Ｅｍｉｔｔｅｒ, Ｒｅａｒ Ｃｅｌｌ）構造が注目されている（例えば、特許文献１参照）。ＰＥＲＣ構造は、裏面再結合の一因である裏面電極とＳｉ基板間のオーミックコンタクト部をポイント状又はライン状に制限しているのが特徴で、裏面電極のコンタクト部以外はすべてパッシベーション膜で覆われている。ＰＥＲＣ構造に用いることができる裏面パッシベーション膜としては、原子層堆積法（Ａｔｏｍｉｃ　Ｌａｙｅｒ　Ｄｅｐｏｓｉｔｉｏｎ；ＡＬＤ）又はＣＶＤ法（Ｃｈｅｍｉｃａｌ　Ｖａｐｏｒ　Ｄｅｐｏｓｉｔｉｏｎ）によるアモルファス酸化アルミニウム（ＡｌＯＸ）膜が挙げられる。ＡＬＤ法やＣＶＤ法によるＡｌＯＸ膜は、大きな負の固定電荷をもつことが知られ、これを適用したＰＥＲＣ構造太陽電池素子は高い発電性能を示すことが知られている。 A PERC (Passivated Emitter, Real Cell) structure has attracted attention as a measure for reducing backside recombination loss (see, for example, Patent Document 1). The PERC structure is characterized in that the ohmic contact portion between the back surface electrode and the Si substrate, which is one of the causes of the back surface recombination, is restricted to a point shape or a line shape, and all parts other than the contact portion of the back surface electrode are covered with a passivation film. It has been. Examples of the back surface passivation film that can be used for the PERC structure include an amorphous aluminum oxide ( AlOX ) film obtained by an atomic layer deposition method (ALD) or a CVD method (Chemical Vapor Deposition). It is known that the AlOX film obtained by the ALD method or the CVD method has a large negative fixed charge, and the PERC structure solar cell element to which this is applied is known to exhibit high power generation performance.
　ＰＥＲＣ構造では、裏面電極とシリコン基板のコンタクト部が限られていることから、両面受光（ｂｉｆａｃｉａｌ）型の太陽電池素子が実現できる。ｂｉｆａｃｉａｌ－ＰＥＲＣ構造の利点として、裏面に差し込んだ光を活用できること等が挙げられる。 In the PERC structure, since the contact portion between the back surface electrode and the silicon substrate is limited, a double-sided light receiving (biaxial) type solar cell element can be realized. One of the advantages of the biological-PERC structure is that the light inserted into the back surface can be utilized.
　上述したＰＥＲＣ構造（ｂｉｆａｃｉａｌ－ＰＥＲＣ及びＭＢＢ（Ｍｕｌｔｉ　Ｂｕｓｂａｒ）－ｂｉｆａｃｉａｌ－ＰＥＲＣ構造を含む）において、裏面電極を形成する際は、一般的に銀を含む電極形成用組成物と、アルミニウムを含む電極形成用組成物とを、基板の所定の領域にそれぞれ印刷し、乾燥した後、一括して熱処理する。
　上記構造では、アルミニウム電極の表面に形成されている酸化アルミニウム（Ａｌ２Ｏ３）皮膜と配線材料を被覆しているはんだとの濡れ性が悪いため、アルミニウム電極には配線材料を直接接合できない。また、裏面においては、受光面側と同様、配線材料を接続する箇所には出力取出し電極としての銀電極を形成する必要があるため、裏面電極プロセスにおいては、成膜したパッシベーション膜の上にまず銀電極形成用組成物を塗布する。このとき、従来のプロセスで形成された裏面電極では、アルミニウム電極と、裏面出力取出し電極としての銀電極との段差（厚さの差）によって、配線材料の接続不良が生じたり、太陽電池としての信頼性が損なわれる可能性がある。 When forming a back surface electrode in the above-mentioned PERC structure (including a biological-PERC and MBB (Multi Busbar) -bifacial-PERC structure), generally, an electrode forming composition containing silver and an electrode forming containing aluminum are formed. The composition for use is printed on a predetermined area of the substrate, dried, and then heat-treated collectively.
In the above structure, the aluminum oxide (Al 2 O 3 ) film formed on the surface of the aluminum electrode and the solder covering the wiring material have poor wettability, so that the wiring material cannot be directly bonded to the aluminum electrode. Further, on the back surface, as in the case of the light receiving surface side, it is necessary to form a silver electrode as an output extraction electrode at the place where the wiring material is connected. The composition for forming a silver electrode is applied. At this time, in the back surface electrode formed by the conventional process, the connection failure of the wiring material may occur due to the step (difference in thickness) between the aluminum electrode and the silver electrode as the back surface output extraction electrode, or as a solar cell. Reliability may be compromised.
　これは、例えば、以下のようにして考えることができる。裏面電極のうち、出力取出し電極としての銀電極は、銀電極形成用組成物の使用量低減等の観点から、配線材料の接続方向に沿って連続的に形成されず、配線材料の接続方向に沿って、銀電極と銀電極との間にアルミニウム電極が形成されることがある。熱処理（焼成後）のアルミニウム電極の厚さは一般的に２０μｍ～４０μｍであり、裏面出力取出し電極としての銀電極の厚さは一般的に２μｍ～５μｍである。このような場合、配線材料の一部がアルミニウム電極上に配置されることになるが、アルミニウム電極と銀電極との段差が大きいと、配線材料の変形が段差に追従できず、銀電極での配線材料の接続が不十分になることが考えられる。また、銀電極において配線材料の接続ができたとしても、配線材料が段差に応じて凹凸を形成しながら変形するため、熱による内部応力以外の応力が加わると考えられる。このような中で、太陽電池部材に温度変化が与えられるような試験又は環境（例えば、温度サイクル試験）中に、接続部に亀裂等が生じることで、発電性能の低下率が大きくなってしまう。 This can be considered, for example, as follows. Of the backside electrodes, the silver electrode as the output take-out electrode is not continuously formed along the connection direction of the wiring material from the viewpoint of reducing the amount of the composition for forming the silver electrode, and is not formed continuously along the connection direction of the wiring material. Along the way, an aluminum electrode may be formed between the silver electrode and the silver electrode. The thickness of the aluminum electrode after heat treatment (after firing) is generally 20 μm to 40 μm, and the thickness of the silver electrode as the back surface output take-out electrode is generally 2 μm to 5 μm. In such a case, a part of the wiring material is arranged on the aluminum electrode, but if the step between the aluminum electrode and the silver electrode is large, the deformation of the wiring material cannot follow the step, and the silver electrode cannot follow the step. It is conceivable that the connection of wiring materials will be insufficient. Further, even if the wiring material can be connected to the silver electrode, it is considered that stress other than the internal stress due to heat is applied because the wiring material is deformed while forming unevenness according to the step. Under such circumstances, cracks or the like occur in the connection portion during a test or environment (for example, a temperature cycle test) in which the temperature of the solar cell member is changed, so that the rate of deterioration of power generation performance becomes large. ..
　上述したような課題を解決する方法として、アルミニウム電極と銀電極とをそれぞれ基板上に形成するのではなく、基板上に形成したアルミニウム電極と、その上に形成される銀電極とが積層した状態の電極（以下、アルミニウム／銀積層電極ともいう）を形成することが有効と考えられる。
　アルミニウム／銀積層電極を形成する方法としては、例えば、アルミニウム粒子を含む電極形成用組成物を所望のパターンで基板の裏面に塗布し、アルミニウム粒子含有膜を形成した後に、銀を含む電極形成用組成物を所望のパターンでアルミニウム粒子含有膜の上に印刷し、一括して熱処理することが考えられる。 As a method for solving the above-mentioned problems, instead of forming the aluminum electrode and the silver electrode on the substrate respectively, the aluminum electrode formed on the substrate and the silver electrode formed on the aluminum electrode are laminated. It is considered effective to form an electrode (hereinafter, also referred to as an aluminum / silver laminated electrode).
As a method for forming an aluminum / silver laminated electrode, for example, an electrode forming composition containing aluminum particles is applied to the back surface of a substrate in a desired pattern to form an aluminum particle-containing film, and then an electrode containing silver is formed. It is conceivable to print the composition on an aluminum particle-containing film in a desired pattern and heat the composition all at once.
特許第６２０３９９０号公報Japanese Patent No. 6203990
　太陽電池は一般に屋外で使用されるため、アルミニウム／銀積層電極は高温高湿環境下におかれても劣化等が生じにくく、充分な信頼性を有していることが望まれる。
　上記事情に鑑み、本開示は、高温高湿環境下における信頼性に優れるアルミニウム／銀積層電極を形成可能な電極形成用組成物の提供を課題とする。本開示はまた、この電極形成用組成物を用いて得られる太陽電池素子及びアルミニウム／銀積層電極の提供を課題とする。 Since solar cells are generally used outdoors, it is desirable that the aluminum / silver laminated electrodes have sufficient reliability because they are less likely to deteriorate even when placed in a high temperature and high humidity environment.
In view of the above circumstances, it is an object of the present disclosure to provide an electrode forming composition capable of forming an aluminum / silver laminated electrode having excellent reliability in a high temperature and high humidity environment. The present disclosure also relates to the provision of a solar cell element and an aluminum / silver laminated electrode obtained by using this electrode forming composition.
　上記課題を実施するための手段には、以下の実施形態が含まれる。
＜１＞銀含有粒子と、ビスマス含有粒子と、ガラス粒子とを含み、前記ガラス粒子はリンを含有するガラス粒子を含み、前記リンを含有するガラス粒子の体積平均粒子径が１０．０μｍ～５０．０μｍである、電極形成用組成物。
＜２＞前記ガラス粒子はホウ素を含有するガラス粒子を更に含む、＜１＞に記載の電極形成用組成物。
＜３＞前記リンを含有するガラス粒子において、酸化リンの含有率が全体の２０．０質量％以上である、＜１＞又は＜２＞に記載の電極形成用組成物。
＜４＞前記ホウ素を含有するガラス粒子において、酸化ホウ素の含有率が全体の３．０質量％以上である、＜２＞に記載の電極形成用組成物。
＜５＞前記ホウ素を含有するガラス粒子が酸化ビスマスを含む、＜２＞又は＜４＞に記載の電極形成用組成物。
＜６＞前記ビスマス含有粒子が金属ビスマス、ビスマス合金及び酸化ビスマスからなる群より選択される少なくとも１種を含む、＜１＞～＜５＞のいずれか１項に記載の電極形成用組成物。
＜７＞前記銀含有粒子の含有量に対する前記ビスマス含有粒子の含有量の質量比（Ｂｉ／Ａｇ比）が０．３０～１．４０である、＜１＞～＜６＞のいずれか１項に記載の電極形成用組成物。
＜８＞前記ガラス粒子の含有量に対する前記ビスマス含有粒子の含有量の質量比（Ｂｉ／Ｇ比）が０．５～１５．０である、＜１＞～＜７＞のいずれか１項に記載の電極形成用組成物。
＜９＞前記ガラス粒子の含有率が前記電極形成用組成物全体の１．０質量％～１５．０質量％である、＜１＞～＜８＞のいずれか１項に記載の電極形成用組成物。
＜１０＞溶剤及び樹脂からなる群より選択される少なくとも１つを含む、＜１＞～＜９＞のいずれか１項に記載の電極形成用組成物。
＜１１＞アルミニウム電極の上に銀電極を形成するための、＜１＞～＜１０＞のいずれか１項に記載の電極形成用組成物。
＜１２＞半導体基板と、前記半導体基板上に設けられるパッシベーション膜と、前記パッシベーション膜上に設けられる＜１＞～＜１１＞のいずれか１項に記載の電極形成用組成物の熱処理物を含むアルミニウム／銀積層電極と、を有する太陽電池素子。
＜１３＞＜１＞～＜１１＞のいずれか１項に記載の電極形成用組成物の熱処理物を含み、かつ、アルミニウムを含む第１電極と、前記第１電極の上に配置される銀を含む第２電極とを備え、前記第１電極は酸化ビスマス相及びリンを含有するガラス相を更に含む、アルミニウム／銀積層電極。 Means for carrying out the above tasks include the following embodiments.
<1> Silver-containing particles, bismuth-containing particles, and glass particles are included. The glass particles contain phosphorus-containing glass particles, and the volume average particle diameter of the phosphorus-containing glass particles is 10.0 μm to 50. A composition for forming an electrode, which is 0.0 μm.
<2> The electrode-forming composition according to <1>, wherein the glass particles further contain boron-containing glass particles.
<3> The electrode-forming composition according to <1> or <2>, wherein the phosphorus-containing glass particles have a phosphorus oxide content of 20.0% by mass or more as a whole.
<4> The electrode-forming composition according to <2>, wherein the boron oxide-containing glass particles have a boron oxide content of 3.0% by mass or more as a whole.
<5> The electrode-forming composition according to <2> or <4>, wherein the boron-containing glass particles contain bismuth oxide.
<6> The electrode-forming composition according to any one of <1> to <5>, wherein the bismuth-containing particles contain at least one selected from the group consisting of metal bismuth, bismuth alloy, and bismuth oxide.
<7> Any one of <1> to <6>, wherein the mass ratio (Bi / Ag ratio) of the content of the bismuth-containing particles to the content of the silver-containing particles is 0.30 to 1.40. The composition for forming an electrode according to.
<8> In any one of <1> to <7>, the mass ratio (Bi / G ratio) of the content of the bismuth-containing particles to the content of the glass particles is 0.5 to 15.0. The electrode-forming composition according to the above.
<9> The electrode forming device according to any one of <1> to <8>, wherein the content of the glass particles is 1.0% by mass to 15.0% by mass of the entire electrode forming composition. Composition.
<10> The electrode forming composition according to any one of <1> to <9>, which comprises at least one selected from the group consisting of a solvent and a resin.
<11> The electrode forming composition according to any one of <1> to <10> for forming a silver electrode on an aluminum electrode.
<12> The semiconductor substrate, the passivation film provided on the semiconductor substrate, and the heat-treated product of the electrode forming composition according to any one of <1> to <11> provided on the passivation film are included. A solar cell element having an aluminum / silver laminated electrode.
<13> A first electrode containing the heat-treated electrode-forming composition according to any one of <1> to <11> and containing aluminum, and silver arranged on the first electrode. The first electrode is an aluminum / silver laminated electrode further comprising a bismuth oxide phase and a glass phase containing phosphorus.
　本開示によれば、高温高湿環境下における信頼性に優れるアルミニウム／銀積層電極を形成可能な電極形成用組成物が提供される。本開示によれば、この電極形成用組成物を用いて得られる太陽電池素子及びアルミニウム／銀積層電極が提供される。 According to the present disclosure, there is provided an electrode forming composition capable of forming an aluminum / silver laminated electrode having excellent reliability in a high temperature and high humidity environment. According to the present disclosure, a solar cell element and an aluminum / silver laminated electrode obtained by using this electrode forming composition are provided.
太陽電池素子の裏面におけるアルミニウム電極及びアルミニウム／銀積層電極の断面の一例を示す図である。It is a figure which shows an example of the cross section of the aluminum electrode and the aluminum / silver laminated electrode on the back surface of a solar cell element. アルミニウム／銀積層電極の製造方法の一例を示す断面模式図である。It is sectional drawing which shows an example of the manufacturing method of the aluminum / silver laminated electrode. アルミニウム／銀積層電極の製造方法の一例を示す断面模式図である。It is sectional drawing which shows an example of the manufacturing method of the aluminum / silver laminated electrode. アルミニウム／銀積層電極の製造方法の一例を示す断面模式図である。It is sectional drawing which shows an example of the manufacturing method of the aluminum / silver laminated electrode. アルミニウム／銀積層電極の断面模式図である。It is sectional drawing of the aluminum / silver laminated electrode. 太陽電池素子の受光面の一例を示す概略平面図である。It is a schematic plan view which shows an example of the light receiving surface of a solar cell element. 太陽電池素子の裏面の一例を示す概略平面図である。It is a schematic plan view which shows an example of the back surface of a solar cell element. 太陽電池素子の裏面の一例を示す概略平面図である。It is a schematic plan view which shows an example of the back surface of a solar cell element. 太陽電池素子の一例を示す断面模式図（図５ＡのＡ－Ａ´部の切断面）である。It is sectional drawing (the cut surface of the part AA' part of FIG. 5A which shows an example of a solar cell element. 太陽電池素子の一例を示す断面模式図（図５ＢのＢ－Ｂ´部の切断面）である。It is sectional drawing (the cut surface of the BB'part of FIG. 5B) which shows an example of the solar cell element. 太陽電池素子の一例を示す断面模式図（図５ＢのＣ－Ｃ´部の切断面）である。It is sectional drawing (the cut surface of the CC'part of FIG. 5B) which shows an example of the solar cell element. 実施例で作製した太陽電池素子の裏面電極の断面組織構造を示す走査型電子顕微鏡（ＳＥＭ）で撮影された画像である。It is an image taken by a scanning electron microscope (SEM) which shows the cross-sectional structure structure of the back electrode of a solar cell element produced in an Example. 図７に示す画像のＥＤＸ分析結果である。It is the EDX analysis result of the image shown in FIG.
　以下、本開示の実施形態について詳細に説明する。ただし、本発明は下記実施形態に限られるものではない。
　本開示において「工程」との語は、独立した工程だけではなく、他の工程と明確に区別できない場合であっても、その工程の目的が達成されれば、本用語に含まれる。
　本開示において「～」を用いて示された数値範囲は、「～」の前後に記載される数値をそれぞれ最小値及び最大値として含む範囲を示す。
　本開示において、組成物中の各成分の含有量は、組成物中に各成分に該当する物質が複数存在する場合には、特に断らない限り、組成物中に存在する当該複数の物質の合計量を意味する。
　図面において、同等の構成要素には同一の符号を付す。
　本開示において「積層」との語は、層を積み重ねることを示し、二以上の層が結合されてもよく、二以上の層が着脱可能であってもよい。
　本開示において「断面」との語は、太陽電池素子を半導体基板の面方向に対して垂直に切断して得られる面を意味する。
　本開示において「熱処理」との語には、熱処理の対象物に含まれる粒子が焼結又は溶融する条件で行う加熱（焼成等）を含む。 Hereinafter, embodiments of the present disclosure will be described in detail. However, the present invention is not limited to the following embodiments.
In the present disclosure, the term "process" is included in this term not only as an independent process but also as long as the purpose of the process is achieved even if it cannot be clearly distinguished from other processes.
The numerical range indicated by using "-" in the present disclosure indicates a range including the numerical values before and after "-" as the minimum value and the maximum value, respectively.
In the present disclosure, the content of each component in the composition is the sum of the plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition. Means quantity.
In the drawings, equivalent components are designated by the same reference numerals.
In the present disclosure, the term "laminated" refers to stacking layers, and two or more layers may be bonded or the two or more layers may be removable.
In the present disclosure, the term "cross section" means a surface obtained by cutting a solar cell element perpendicular to the surface direction of the semiconductor substrate.
In the present disclosure, the term "heat treatment" includes heating (firing, etc.) performed under the condition that the particles contained in the object to be heat-treated are sintered or melted.
＜電極形成用組成物＞
　本開示の一実施形態に係る電極形成用組成物は、銀含有粒子と、ビスマス含有粒子と、ガラス粒子とを含み、前記ガラス粒子はリンを含有するガラス粒子を含み、前記リンを含有するガラス粒子の体積平均粒子径が１０．０μｍ～５０．０μｍである、電極形成用組成物である。 <Composition for forming electrodes>
The electrode-forming composition according to an embodiment of the present disclosure includes silver-containing particles, bismuth-containing particles, and glass particles, and the glass particles include phosphorus-containing glass particles and the phosphorus-containing glass. A composition for forming an electrode having a volume average particle diameter of particles of 10.0 μm to 50.0 μm.
　銀含有粒子と、ビスマス含有粒子と、ガラス粒子としてリンを含有するガラス粒子とを含む電極形成用組成物は、銀含有粒子と、ビスマス含有粒子とを含み、リンを含有するガラス粒子を含まない電極形成用組成物に比べ、高温高湿環境下における信頼性に優れるアルミニウム／銀積層電極を形成することができる。更に、リンを含有するガラス粒子の体積平均粒子径が１０．０μｍ～５０．０μｍであることで、高温高湿環境下における信頼性により優れるアルミニウム／銀積層電極を形成することができる。その理由は必ずしも明らかではないが、下記のように考えられる。 The electrode-forming composition containing silver-containing particles, bismuth-containing particles, and glass particles containing phosphorus as glass particles contains silver-containing particles and bismuth-containing particles, and does not contain phosphorus-containing glass particles. Compared with the electrode forming composition, it is possible to form an aluminum / silver laminated electrode having excellent reliability in a high temperature and high humidity environment. Further, since the volume average particle diameter of the phosphorus-containing glass particles is 10.0 μm to 50.0 μm, it is possible to form an aluminum / silver laminated electrode having higher reliability in a high temperature and high humidity environment. The reason is not always clear, but it can be considered as follows.
　銀含有粒子と、ビスマス含有粒子とを含む電極形成用組成物は、基板上に形成されたアルミニウム粒子含有膜上の所望の領域に付与され、必要に応じて乾燥した後に、熱処理される。
　熱処理により、電極形成用組成物に含まれる銀含有粒子は焼結して銀電極を、アルミニウム粒子含有膜に含まれるアルミニウム粒子は焼結してアルミニウム電極をそれぞれ形成する。このとき、ビスマス含有粒子に含まれるビスマスが酸化して形成する酸化ビスマス相が、銀電極とアルミニウム電極との界面における相互拡散を抑制する性質（以下、拡散バリア性ともいう）を発現する。このため、銀電極中のアルミニウム濃度が低く抑えられ、配線材料への濡れ性が良好に維持される。 The electrode-forming composition containing the silver-containing particles and the bismuth-containing particles is applied to a desired region on the aluminum particle-containing film formed on the substrate, dried if necessary, and then heat-treated.
By the heat treatment, the silver-containing particles contained in the electrode-forming composition are sintered to form a silver electrode, and the aluminum particles contained in the aluminum particle-containing film are sintered to form an aluminum electrode. At this time, the bismuth oxide phase formed by oxidizing the bismuth contained in the bismuth-containing particles exhibits a property of suppressing mutual diffusion at the interface between the silver electrode and the aluminum electrode (hereinafter, also referred to as diffusion barrier property). Therefore, the concentration of aluminum in the silver electrode is suppressed to a low level, and the wettability to the wiring material is maintained well.
　更に、ビスマス含有粒子の少なくとも一部が熱処理によってアルミニウム粒子含有膜に移行し、アルミニウム粒子の間又はアルミニウム粒子と基板との間に酸化ビスマス相を形成する。これにより、形成されるアルミニウム電極のバルク強度及び基板に対する密着性が向上する。
　一方、アルミニウム／銀積層電極が高温高湿環境下におかれると、アルミニウム電極と銀電極との界面において酸化ビスマス相の一部が金属ビスマスに還元して、体積変化が生じる。その結果、アルミニウム電極と銀電極との界面に亀裂等が生じて電極の信頼性が低下する原因となる。電極形成用組成物がリンを含有するガラス粒子を含んでいると、熱処理によってリンを含有するガラス粒子の溶融物がアルミニウム電極と銀電極との界面において酸化ビスマス相と反応し、酸化ビスマスの還元を抑制するように作用する。その結果、アルミニウム電極と銀電極との界面の状態が良好に維持されて、高温高湿環境下での信頼性が向上すると考えられる。 Further, at least a part of the bismuth-containing particles is transferred to the aluminum particle-containing film by heat treatment to form a bismuth oxide phase between the aluminum particles or between the aluminum particles and the substrate. This improves the bulk strength of the formed aluminum electrode and the adhesion to the substrate.
On the other hand, when the aluminum / silver laminated electrode is placed in a high temperature and high humidity environment, a part of the bismuth oxide phase is reduced to metal bismuth at the interface between the aluminum electrode and the silver electrode, and a volume change occurs. As a result, cracks or the like occur at the interface between the aluminum electrode and the silver electrode, which causes the reliability of the electrode to deteriorate. When the electrode-forming composition contains phosphorus-containing glass particles, the melt of the phosphorus-containing glass particles reacts with the bismuth oxide phase at the interface between the aluminum electrode and the silver electrode by heat treatment to reduce bismuth oxide. Acts to suppress. As a result, it is considered that the state of the interface between the aluminum electrode and the silver electrode is maintained well, and the reliability in a high temperature and high humidity environment is improved.
　上記の作用に加え、リンを含有するガラス粒子の体積平均粒子径が１０．０μｍ以上であることで、リンを含有するガラス粒子の体積平均粒子径が１０．０μｍより小さい場合に比べて高温高湿環境下での信頼性がより向上する。これは、電極形成用組成物の熱処理によって得られる銀電極の表面に、リンを含有するガラス粒子に起因する凹凸形状が形成されるためと考えられる。その結果、配線材料と銀電極との間に滞留する応力が緩和されて亀裂等の発生が抑制されると考えられる。
　更に、リンを含有するガラス粒子の体積平均粒子径が５０．０μｍ以下であるために電極形成用組成物中のリンを含有するガラス粒子の分散性が良好であり、銀電極の表面に形成される凹凸形状の分布の偏りが抑制されることで、配線材料と銀電極との間に滞留する応力が効果的に緩和されると考えられる。 In addition to the above action, the volume average particle size of the phosphorus-containing glass particles is 10.0 μm or more, so that the temperature is higher than that when the volume average particle size of the phosphorus-containing glass particles is smaller than 10.0 μm. Greater reliability in moist environments. It is considered that this is because the uneven shape due to the phosphorus-containing glass particles is formed on the surface of the silver electrode obtained by the heat treatment of the electrode forming composition. As a result, it is considered that the stress accumulated between the wiring material and the silver electrode is relaxed and the generation of cracks and the like is suppressed.
Further, since the volume average particle diameter of the phosphorus-containing glass particles is 50.0 μm or less, the phosphorus-containing glass particles in the electrode forming composition have good dispersibility and are formed on the surface of the silver electrode. It is considered that the stress accumulated between the wiring material and the silver electrode is effectively alleviated by suppressing the uneven distribution of the uneven shape.
（銀含有粒子）
　電極形成用組成物は、銀含有粒子を含む。電極形成用組成物に含まれる銀含有粒子は、１種のみでも２種以上であってもよい。 (Silver-containing particles)
The electrode forming composition contains silver-containing particles. The silver-containing particles contained in the electrode forming composition may be only one kind or two or more kinds.
　銀含有粒子は、銀を含む粒子であれば特に制限されない。中でも、銀粒子及び銀合金粒子から選ばれる少なくとも１種であることが好ましく、銀粒子及び銀含有率が５０．０質量％以上である銀合金粒子から選ばれる少なくとも１種であることが好ましい。 The silver-containing particles are not particularly limited as long as they are silver-containing particles. Among them, at least one selected from silver particles and silver alloy particles is preferable, and at least one selected from silver particles and silver alloy particles having a silver content of 50.0% by mass or more is preferable.
　銀粒子における銀の含有率は特に制限されない。例えば、銀粒子全体の９５．０質量％以上とすることができ、９７．０質量％以上であることが好ましく、９９．０質量％以上であることがより好ましい。 The silver content in the silver particles is not particularly limited. For example, it can be 95.0% by mass or more of the whole silver particles, preferably 97.0% by mass or more, and more preferably 99.0% by mass or more.
　銀合金粒子は、銀を含む合金の粒子であれば特に制限されない。中でも、銀合金粒子の融点及び焼結性の観点から、銀の含有率は粒子全体の５０．０質量％以上であることが好ましく、６０．０質量％以上であることがより好ましく、７０．０質量％以上であることが更に好ましく、８０．０質量％以上であることが特に好ましい。上記含有率は、９５．０質量％以下であってもよい。 The silver alloy particles are not particularly limited as long as they are alloy particles containing silver. Above all, from the viewpoint of the melting point and sinterability of the silver alloy particles, the silver content is preferably 50.0% by mass or more, more preferably 60.0% by mass or more, and 70. It is more preferably 0% by mass or more, and particularly preferably 80.0% by mass or more. The content may be 95.0% by mass or less.
　銀合金としては、Ａｇ－Ｐｄ系合金、Ａｇ－Ｐｄ－Ａｕ系合金、Ａｇ－Ｐｄ－Ｃｕ系合金、Ａｇ－Ｐｄ－Ｉｎ系合金、Ａｇ－Ｉｎ系合金、Ａｇ－Ｓｎ系合金、Ａｇ－Ｚｎ系合金、Ａｇ－Ｓｎ－Ｚｎ系合金等が挙げられる。
　銀含有粒子は、銀及び銀合金に該当しない成分を含まなくても、含んでいてもよい。
　銀含有粒子は、銀及び銀合金に該当しない成分を含む場合、その含有率は、銀含有粒子中に３．０質量％以下とすることができ、１．０質量％以下であることが好ましい。 Examples of silver alloys include Ag-Pd-based alloys, Ag-Pd-Au-based alloys, Ag-Pd-Cu-based alloys, Ag-Pd-In-based alloys, Ag-In-based alloys, Ag-Sn-based alloys, and Ag-Zn. Examples include system alloys and Ag-Sn-Zn system alloys.
The silver-containing particles may or may not contain components that do not correspond to silver and silver alloys.
When the silver-containing particles contain a component that does not correspond to silver or a silver alloy, the content thereof can be 3.0% by mass or less in the silver-containing particles, preferably 1.0% by mass or less. ..
　銀含有粒子の粒子径は特に制限されないが、レーザー回折・散乱法により得られる体積基準の粒度分布において小径側からの累積が５０％となるときの粒子径（体積平均粒子径、以下「Ｄ５０％」と略記することがある）として０．１μｍ～５０．０μｍであることが好ましく、０．１５μｍ～４０．０μｍであることがより好ましく、０．２μｍ～３０．０μｍであることが更に好ましい。銀含有粒子の体積平均粒子径が０．１μｍ以上であると、アルミニウム／銀積層電極の表面における銀の濃度を充分に高くでき、配線材料の接続強度が向上する。銀含有粒子の体積平均粒子径が５０．０μｍ以下であると、アルミニウム／銀積層電極内の抵抗が低減する傾向にある。 The particle size of the silver-containing particles is not particularly limited, but the particle size (volume average particle size, hereinafter "D50%") when the accumulation from the small diameter side is 50% in the volume-based particle size distribution obtained by the laser diffraction / scattering method. It is preferably 0.1 μm to 50.0 μm, more preferably 0.15 μm to 40.0 μm, and even more preferably 0.2 μm to 30.0 μm. When the volume average particle diameter of the silver-containing particles is 0.1 μm or more, the concentration of silver on the surface of the aluminum / silver laminated electrode can be sufficiently increased, and the connection strength of the wiring material is improved. When the volume average particle diameter of the silver-containing particles is 50.0 μm or less, the resistance in the aluminum / silver laminated electrode tends to decrease.
　銀含有粒子の粒子径は、レーザー回折式粒度分布計（例えば、ベックマン・コールター（株）、ＬＳ　１３　３２０型レーザー散乱回折法粒度分布測定装置）によって測定される。具体的には、溶剤（テルピネオール）１２５ｇに、銀含有粒子を０．０１質量％～０．３質量％の範囲内で添加し、分散液を調製する。この分散液の約１００ｍｌ程度をセルに注入して２５℃で測定する。粒度分布は溶媒の屈折率を１．４８として測定する。 The particle size of the silver-containing particles is measured by a laser diffraction type particle size distribution meter (for example, Beckman Coulter Co., Ltd., LS13 320 type laser scattering diffraction method particle size distribution measuring device). Specifically, silver-containing particles are added to 125 g of a solvent (terpineol) in the range of 0.01% by mass to 0.3% by mass to prepare a dispersion. About 100 ml of this dispersion is injected into the cell and measured at 25 ° C. The particle size distribution is measured with the refractive index of the solvent as 1.48.
　銀含有粒子の形状は特に制限はなく、略球状、扁平状、ブロック状、板状、鱗片状等であってもよい。銀含有粒子同士の焼結性の観点からは、略球状、扁平状又は板状であることが好ましい。 The shape of the silver-containing particles is not particularly limited, and may be substantially spherical, flat, block-shaped, plate-shaped, scale-shaped, or the like. From the viewpoint of sinterability between silver-containing particles, it is preferably substantially spherical, flat or plate-shaped.
（ビスマス含有粒子）
　電極形成用組成物は、ビスマス含有粒子を含む。電極形成用組成物に含まれるビスマス含有粒子は、１種のみでも２種以上であってもよい。 (Particles containing bismuth)
The electrode forming composition contains bismuth-containing particles. The bismuth-containing particles contained in the electrode forming composition may be only one kind or two or more kinds.
　ビスマス含有粒子は、ビスマスを含む粒子であれば特に制限はない。中でも、金属ビスマス粒子、ビスマス合金粒子及び酸化ビスマス粒子から選ばれる少なくとも１種であることが好ましく、金属ビスマス粒子、ビスマス含有率が４０．０質量％以上であるビスマス合金粒子及び酸化ビスマス粒子から選ばれる少なくとも１種であることが好ましい。
　本開示において、ビスマス含有粒子がガラス状である場合（ビスマスを含むガラス粒子）は、ビスマス含有粒子に該当しないものとする。 The bismuth-containing particles are not particularly limited as long as they are particles containing bismuth. Among them, at least one selected from metal bismuth particles, bismuth alloy particles and oxide bismuth particles is preferable, and metal bismuth particles, bismuth alloy particles having a bismuth content of 40.0% by mass or more and bismuth oxide particles are selected. It is preferable that the amount is at least one.
In the present disclosure, when the bismuth-containing particles are glassy (glass particles containing bismuth), they are not considered to be bismuth-containing particles.
　金属ビスマス粒子におけるビスマスの含有率は特に制限されない。例えば、金属ビスマス粒子全体の９５．０質量％以上とすることができ、９７．０質量％以上であることが好ましく、９９．０質量％以上であることがより好ましい。 The content of bismuth in the metal bismuth particles is not particularly limited. For example, it can be 95.0% by mass or more of the total metal bismuth particles, preferably 97.0% by mass or more, and more preferably 99.0% by mass or more.
　ビスマス合金粒子は、ビスマスを含む合金の粒子であれば特に制限されない。中でも、ビスマス合金粒子の融点及び拡散バリア性の観点から、ビスマス合金粒子のビスマスの含有率は粒子全体の４０．０質量％以上であることが好ましく、５０．０質量％以上であることがより好ましく、６０．０質量％以上であることが更に好ましく、７０．０質量％以上であることが特に好ましい。ビスマス合金粒子のビスマスの含有率は９５．０質量％以下であってもよい。 The bismuth alloy particles are not particularly limited as long as they are alloy particles containing bismuth. Above all, from the viewpoint of the melting point of the bismuth alloy particles and the diffusion barrier property, the bismuth content of the bismuth alloy particles is preferably 40.0% by mass or more, and more preferably 50.0% by mass or more. It is more preferably 60.0% by mass or more, and particularly preferably 70.0% by mass or more. The content of bismuth in the bismuth alloy particles may be 95.0% by mass or less.
　ビスマス合金としては、Ｂｉ－Ｓｎ系合金、Ｂｉ－Ｓｎ－Ｃｕ系合金、Ｂｉ－Ｐｂ－Ｓｎ系合金、Ｂｉ－Ｃｄ系合金等が挙げられる。 Examples of the bismuth alloy include Bi-Sn-based alloys, Bi-Sn-Cu-based alloys, Bi-Pb-Sn-based alloys, Bi-Cd-based alloys, and the like.
　酸化ビスマス粒子としては、三酸化ビスマス（Ｂｉ２Ｏ３）の粒子が挙げられる。充分な拡散バリア性及びアルミニウム／積層電極自身の低抵抗化を発揮する観点からは、酸化ビスマス粒子は金属ビスマス粒子と併用することが好ましい。
　ビスマス含有粒子は、金属ビスマス、ビスマス合金及び酸化ビスマスに該当しない成分を含まなくても、含んでいてもよい。
　ビスマス含有粒子が金属ビスマス、ビスマス合金及び酸化ビスマスに該当しない成分を含む場合、酸化ビスマス相の形成及びアルミニウム／銀のバリア性の観点からは、その含有率は、ビスマス含有粒子中に３．０質量％以下とすることができ、１．０質量％以下であることが好ましい。 Examples of the bismuth oxide particles include bismuth trioxide (Bi 2 O 3 ) particles. The bismuth oxide particles are preferably used in combination with the metal bismuth particles from the viewpoint of exhibiting sufficient diffusion barrier properties and lowering the resistance of the aluminum / laminated electrode itself.
The bismuth-containing particles may or may not contain components that do not correspond to metal bismuth, bismuth alloy, and bismuth oxide.
When the bismuth-containing particles contain a metal bismuth, a bismuth alloy, and a component that does not correspond to bismuth oxide, the content of the bismuth-containing particles is 3.0 in the bismuth-containing particles from the viewpoint of the formation of the bismuth oxide phase and the barrier property of aluminum / silver. It can be mass% or less, preferably 1.0 mass% or less.
　ビスマス含有粒子の粒子径は特に制限されないが、体積平均粒子径が０．１μｍ～５０．０μｍであることが好ましく、０．１５μｍ～４０．０μｍであることがより好ましく、０．２μｍ～３０．０μｍであることが更に好ましい。ビスマス含有粒子の粒子径が０．１μｍ以上であると、アルミニウム粒子含有膜への移行及び酸化ビスマス相の形成が促進される。ビスマス含有粒子の粒子径が５０．０μｍ以下であると、拡散バリア性が効果的に発揮される。
　ビスマス含有粒子の体積平均粒子径は、銀含有粒子の体積平均粒子径と同様にして測定される。 The particle size of the bismuth-containing particles is not particularly limited, but the volume average particle size is preferably 0.1 μm to 50.0 μm, more preferably 0.15 μm to 40.0 μm, and 0.2 μm to 30. It is more preferably 0 μm. When the particle size of the bismuth-containing particles is 0.1 μm or more, the migration to the aluminum particle-containing film and the formation of the bismuth oxide phase are promoted. When the particle size of the bismuth-containing particles is 50.0 μm or less, the diffusion barrier property is effectively exhibited.
The volume average particle size of the bismuth-containing particles is measured in the same manner as the volume average particle size of the silver-containing particles.
　ビスマス含有粒子の形状は特に制限されず、略球状、扁平状、ブロック状、板状、鱗片状等であってもよい。拡散バリア性の観点からは、略球状、扁平状又は板状であることが好ましい。 The shape of the bismuth-containing particles is not particularly limited, and may be substantially spherical, flat, block-shaped, plate-shaped, scale-shaped, or the like. From the viewpoint of diffusion barrier property, it is preferably substantially spherical, flat or plate-shaped.
　電極形成用組成物における銀含有粒子の含有量に対するビスマス含有粒子の含有量の質量比（Ｂｉ／Ａｇ比）は、０．３０～１．４０であることが好ましく。０．３５～１．３０であることがより好ましく、０．４０～１．２０であることが更に好ましく、０．４５～１．１０であることが更により好ましい。Ｂｉ／Ａｇ比を０．３０以上とすることで、アルミニウムと銀との相互拡散が効果的に抑制される傾向にある。Ｂｉ／Ａｇ比を１．４０以下とすることで、アルミニウム／銀積層電極表面の銀濃度が充分に確保され、接続材料の接続強度（はんだの濡れ性）が良好に維持される傾向にある。 The mass ratio (Bi / Ag ratio) of the content of the bismuth-containing particles to the content of the silver-containing particles in the electrode forming composition is preferably 0.30 to 1.40. It is more preferably 0.35 to 1.30, further preferably 0.40 to 1.20, and even more preferably 0.45 to 1.10. By setting the Bi / Ag ratio to 0.30 or more, the mutual diffusion between aluminum and silver tends to be effectively suppressed. By setting the Bi / Ag ratio to 1.40 or less, the silver concentration on the surface of the aluminum / silver laminated electrode is sufficiently secured, and the connection strength (wetting property of the solder) of the connecting material tends to be well maintained.
（ガラス粒子）
　電極形成用組成物はガラス粒子を含み、ガラス粒子としてリンを含有するガラス粒子（以下、リン含有ガラス粒子ともいう）を含む。リンを含有するガラスとしては、酸化リン（Ｐ２Ｏ５）を含むガラス粒子が挙げられ、リン酸塩ガラスが好ましい。
　本開示においてリン酸塩ガラスとは、酸化リン（Ｐ２Ｏ５）を網目形成酸化物として含むガラスを意味する。 (Glass particles)
The composition for forming an electrode contains glass particles, and contains glass particles containing phosphorus as glass particles (hereinafter, also referred to as phosphorus-containing glass particles). Examples of the phosphorus-containing glass include glass particles containing phosphorus oxide ( P2O 5 ) , and phosphate glass is preferable.
In the present disclosure, the phosphate glass means a glass containing phosphorus oxide ( P2O 5 ) as a network-forming oxide.
　リン含有ガラス粒子を構成するガラスの組成としては、ガラスの機能上の観点から、酸化リンの含有率が全体の２０．０質量％以上であることが好ましく、３０．０質量％以上であることがより好ましく、３５．０質量％以上であることが更に好ましい。酸化リン（Ｐ２Ｏ５）の含有率は全体の５０．０質量％以下であることが好ましく、４５．０質量％以下であることがより好ましく、４０．０質量％以下であることが更に好ましい。 As for the composition of the glass constituting the phosphorus-containing glass particles, the content of phosphorus oxide is preferably 20.0% by mass or more, preferably 30.0% by mass or more, from the viewpoint of the function of the glass. Is more preferable, and 35.0% by mass or more is further preferable. The content of phosphorus oxide (P 2 O 5 ) is preferably 50.0% by mass or less, more preferably 45.0% by mass or less, and further preferably 40.0% by mass or less. preferable.
　リン含有ガラス粒子は、酸化リンと、酸化リン以外の酸化物とを含んでもよい。
　リン含有ガラス粒子を構成するガラスに含まれる酸化リン以外の酸化物としては、例えば、二酸化ケイ素（ＳｉＯ２）、酸化アルミニウム（Ａｌ２Ｏ３）、酸化ホウ素（Ｂ２Ｏ３）、酸化バナジウム（Ｖ２Ｏ５）、酸化カリウム（Ｋ２Ｏ）、酸化ビスマス（Ｂｉ２Ｏ３）、酸化ナトリウム（Ｎａ２Ｏ）、酸化リチウム（Ｌｉ２Ｏ）、酸化バリウム（ＢａＯ）、酸化ストロンチウム（ＳｒＯ）、酸化カルシウム（ＣａＯ）、酸化マグネシウム（ＭｇＯ）、酸化ベリリウム（ＢｅＯ）、酸化亜鉛（ＺｎＯ）、酸化カドミウム（ＣｄＯ）、酸化錫（ＳｎＯ）、酸化ジルコニウム（ＺｒＯ２）、酸化タングステン（ＷＯ３）、酸化モリブデン（ＭｏＯ３）、酸化ランタン（Ｌａ２Ｏ３）、酸化ニオブ（Ｎｂ２Ｏ３）、酸化タンタル（Ｔａ２Ｏ５）、酸化イットリウム（Ｙ２Ｏ３）、酸化チタン（ＴｉＯ２）、酸化ゲルマニウム（ＧｅＯ２）、酸化テルル（ＴｅＯ２）、酸化ルテチウム（Ｌｕ２Ｏ３）、酸化アンチモン（Ｓｂ２Ｏ３）、酸化銅（ＣｕＯ）、酸化鉄（Ｆｅ２Ｏ３）、酸化銀（ＡｇＯ）及び酸化マンガン（ＭｎＯ）が挙げられる。 The phosphorus-containing glass particles may contain phosphorus oxide and an oxide other than phosphorus oxide.
Examples of oxides other than phosphorus oxide contained in the glass constituting the phosphorus-containing glass particles include silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), boron oxide (B 2 O 3 ), and vanadium oxide (B 2 O 3). V 2 O 5 ), potassium oxide (K 2 O), bismuth oxide (Bi 2 O 3 ), sodium oxide (Na 2 O), lithium oxide (Li 2 O), barium oxide (BaO), strontium oxide (SrO) , Calcium oxide (CaO), magnesium oxide (MgO), beryllium oxide (BeO), zinc oxide (ZnO), cadmium oxide (CdO), tin oxide (SnO), zirconium oxide (ZrO 2 ), tungsten oxide (WO 3 ) , Molybdenum oxide (MoO 3 ), Lantern oxide (La 2 O 3 ), Niobide oxide (Nb 2 O 3 ), Tantal oxide (Ta 2 O 5 ), Yttrium oxide (Y 2 O 3 ), Titanium oxide (TIO 2 ) , Germanium oxide (GeO 2 ), tellurium oxide (TeO 2 ), yttrium oxide (Lu 2 O 3 ), antimony oxide (Sb 2 O 3 ), copper oxide (CuO), iron oxide (Fe 2 O 3 ), silver oxide (AgO) and manganese oxide (MnO) can be mentioned.
　リン含有ガラス粒子は酸化バナジウム、酸化アルミニウム、酸化錫及び酸化亜鉛から選択される少なくとも１種を含むことが好ましく、酸化錫を含むことがより好ましく、錫含有リン酸塩ガラス（Ｐ２Ｏ５－ＳｎＯ系）等が好ましい例として挙げられる。このような組成のガラスを用いることで、アルミニウム／銀積層電極の高温高湿環境下での信頼性がより向上する傾向にある。 The phosphorus-containing glass particles preferably contain at least one selected from vanadium oxide, aluminum oxide, tin oxide and zinc oxide, more preferably tin oxide, and tin-containing phosphate glass (P 2 O 5 −. SnO system) and the like are given as preferable examples. By using glass having such a composition, the reliability of the aluminum / silver laminated electrode in a high temperature and high humidity environment tends to be further improved.
　リン含有ガラス粒子が酸化錫を含む場合、酸化錫の含有率は全体の２０．０質量％以上であることが好ましく、３０．０質量％以上であることがより好ましく、４０．０質量%以上であることが更に好ましい。酸化錫の含有率は全体の８０．０質量％以下であることが好ましく、７０．０質量％以下であることがより好ましく、６０．０質量%以下であることが更に好ましい。
　リン含有ガラス粒子は酸化ホウ素を含まないか、又は酸化ホウ素の含有率が酸化リンの含有率よりも低いことが好ましい。 When the phosphorus-containing glass particles contain tin oxide, the tin oxide content is preferably 20.0% by mass or more, more preferably 30.0% by mass or more, and 40.0% by mass or more. Is more preferable. The content of tin oxide is preferably 80.0% by mass or less, more preferably 70.0% by mass or less, and further preferably 60.0% by mass or less.
It is preferable that the phosphorus-containing glass particles do not contain boron oxide, or the content of boron oxide is lower than the content of phosphorus oxide.
　リン含有ガラス粒子は、体積平均粒子径が１０．０μｍ～５０．０μｍであり、１５．０．０μｍ～４０．０μｍであることが好ましく、１５．０μｍ～３５．０μｍであることがより好ましく、１５．０μｍ～２５．０μｍであることが更に好ましい。
　リン含有ガラス粒子の体積平均粒子径が１０．０μｍ以上であることで、電極形成用組成物を熱処理して得られる銀電極の表面にリン含有ガラス粒子に起因する凹凸形状が形成される。その結果、配線材料と銀電極との接触が点接触になるために応力が緩和され、高温高湿環境下における信頼性が向上する。
　リン含有ガラス粒子の体積平均粒子径が５０．０μｍ以下であることで、電極形成用組成物中でのリン含有ガラス粒子の分散性が良好であり、銀電極の表面に形成される凹凸形状の分布の偏りが抑制される。
　リン含有ガラス粒子の体積平均粒子径は、銀含有粒子の体積平均粒子径と同様にして測定される。 The phosphorus-containing glass particles have a volume average particle diameter of 10.0 μm to 50.0 μm, preferably 15.0.0 μm to 40.0 μm, and more preferably 15.0 μm to 35.0 μm. It is more preferably 15.0 μm to 25.0 μm.
When the volume average particle diameter of the phosphorus-containing glass particles is 10.0 μm or more, an uneven shape due to the phosphorus-containing glass particles is formed on the surface of the silver electrode obtained by heat-treating the electrode-forming composition. As a result, the contact between the wiring material and the silver electrode becomes a point contact, so that the stress is relaxed and the reliability in a high temperature and high humidity environment is improved.
When the volume average particle diameter of the phosphorus-containing glass particles is 50.0 μm or less, the dispersibility of the phosphorus-containing glass particles in the electrode forming composition is good, and the uneven shape formed on the surface of the silver electrode is formed. The bias of the distribution is suppressed.
The volume average particle size of the phosphorus-containing glass particles is measured in the same manner as the volume average particle size of the silver-containing particles.
　太陽電池素子の発電性能の観点からは、電極形成用組成物は、ホウ素を含有するガラス粒子（以下、ホウ素含有ガラス粒子ともいう）を更に含むことが好ましく、ホウ酸塩ガラスを含むことがより好ましい。
　本開示においてホウ酸塩ガラスとは、酸化ホウ素（Ｂ２Ｏ３）を網目形成酸化物として含むガラスを意味する。 From the viewpoint of the power generation performance of the solar cell element, the electrode forming composition preferably further contains boron-containing glass particles (hereinafter, also referred to as boron-containing glass particles), and more preferably contains borate glass. preferable.
In the present disclosure, the borate glass means a glass containing boron oxide (B 2 O 3 ) as a network-forming oxide.
　電極形成用組成物がホウ素含有ガラス粒子を更に含む場合には、電極形成用組成物がリン含有ガラス粒子とホウ素含有ガラス粒子とをそれぞれ含む場合と、電極形成用組成物がリン及びホウ素を含有するガラス粒子を含む場合とが含まれる。
　高温高湿環境下における信頼性の向上と発電性能の維持とを両立させる観点からは、電極形成用組成物は、リン含有ガラス粒子とホウ素含有ガラス粒子とをそれぞれ含むことが好ましく、リン酸塩ガラス粒子とホウ酸塩ガラス粒子とをそれぞれ含むことがより好ましい。 When the electrode forming composition further contains boron-containing glass particles, the electrode forming composition contains phosphorus-containing glass particles and boron-containing glass particles, respectively, and the electrode forming composition contains phosphorus and boron. The case where the glass particles are contained is included.
From the viewpoint of achieving both improvement of reliability and maintenance of power generation performance in a high temperature and high humidity environment, it is preferable that the composition for forming an electrode contains phosphorus-containing glass particles and boron-containing glass particles, respectively, and a phosphate salt. It is more preferable to contain glass particles and borate glass particles, respectively.
　電極形成用組成物がホウ素含有ガラス粒子を含むことで太陽電池素子の発電性能が向上する理由は必ずしも明らかではないが、下記のように考えられる。
　ビスマス含有粒子により形成される酸化ビスマス相は、アルミニウム粒子含有膜が形成される基板の表面のパッシベーション膜を保護するためのＳｉＮＸ膜を溶解して、パッシベーション効果を低減させる可能性がある。
　電極形成用組成物がホウ素含有ガラス粒子を含んでいると、ホウ素含有ガラス粒子が熱処理により溶融し、溶融物の一部はアルミニウム粒子含有膜が配置された基板の表面に達する。その結果、基板表面付近の酸化ビスマス相のビスマス濃度が低下して酸化ビスマス相によるＳｉＮＸ膜の溶解が抑制され、発電性能が良好に維持されると考えられる。 The reason why the power generation performance of the solar cell element is improved by containing the boron-containing glass particles in the electrode forming composition is not necessarily clear, but it is considered as follows.
The bismuth oxide phase formed by the bismuth-containing particles may dissolve the SiNX film for protecting the passivation film on the surface of the substrate on which the aluminum particle-containing film is formed, thereby reducing the passivation effect.
When the composition for forming an electrode contains boron-containing glass particles, the boron-containing glass particles are melted by heat treatment, and a part of the melt reaches the surface of the substrate on which the aluminum particle-containing film is arranged. As a result, it is considered that the bismuth concentration of the bismuth oxide phase near the surface of the substrate is lowered, the dissolution of the SiNX film by the bismuth oxide phase is suppressed, and the power generation performance is maintained well.
　電極形成用組成物がリン含有ガラス粒子とホウ素含有ガラス粒子とを含む場合、リン含有ガラス粒子とホウ素含有ガラス粒子との合計に対するリン含有ガラス粒子の含有率は、３．０質量％～５０．０質量％であることが好ましく、３．５質量％～４５．０質量％であることがより好ましく、４．０質量％～４０．０質量％であることが更に好ましい。
　リン含有ガラス粒子とホウ素含有ガラス粒子との合計に対するリン含有ガラス粒子の含有率を３．０質量％以上とすることで、高温高湿環境下でのアルミニウム／銀積層電極の信頼性がより効果的に向上する傾向にある。また、リン含有ガラス粒子の含有率を５０．０質量％以下とすることで、酸化ビスマス相によるＳｉＮＸ膜の溶解がより効果的に抑制され、発電性能が良好に維持される。 When the composition for forming an electrode contains phosphorus-containing glass particles and boron-containing glass particles, the content of the phosphorus-containing glass particles with respect to the total of the phosphorus-containing glass particles and the boron-containing glass particles is 3.0% by mass to 50. It is preferably 0% by mass, more preferably 3.5% by mass to 45.0% by mass, still more preferably 4.0% by mass to 40.0% by mass.
By setting the content of the phosphorus-containing glass particles to 3.0% by mass or more with respect to the total of the phosphorus-containing glass particles and the boron-containing glass particles, the reliability of the aluminum / silver laminated electrode in a high temperature and high humidity environment is more effective. It tends to improve. Further, by setting the content of the phosphorus-containing glass particles to 50.0% by mass or less, the dissolution of the SiNX film by the bismuth oxide phase is more effectively suppressed, and the power generation performance is maintained well.
　ホウ素含有ガラス粒子を構成するガラスの組成としては、ガラスの機能上の観点から、酸化物としての酸化ホウ素の含有率が全体の３．０質量％以上であることが好ましく、５．０質量％以上であることがより好ましく、１０．０質量％以上であることが更に好ましい。酸化ホウ素の含有率は全体の２５．０質量％以下であることが好ましく、２０．０質量％以下であることがより好ましく、１５．０質量％以下であることが更に好ましい。 As for the composition of the glass constituting the boron-containing glass particles, the content of boron oxide as an oxide is preferably 3.0% by mass or more, preferably 5.0% by mass, from the viewpoint of the function of the glass. The above is more preferable, and 10.0% by mass or more is further preferable. The content of boron oxide is preferably 25.0% by mass or less, more preferably 20.0% by mass or less, and further preferably 15.0% by mass or less.
　ホウ素含有ガラス粒子は、酸化ホウ素と、酸化ホウ素以外の酸化物とを含んでもよい。
　ホウ素含有ガラス粒子を構成するガラスに含まれる酸化ホウ素以外の酸化物としては、リン含有ガラス粒子を構成するガラスに含まれてもよい酸化物として例示した酸化物が挙げられる。
　ホウ素含有ガラス粒子は酸化リンを含まないか、又は酸化リンの含有率が酸化ホウ素の含有率よりも低いことが好ましい。 The boron-containing glass particles may contain boron oxide and an oxide other than boron oxide.
Examples of the oxide other than boron oxide contained in the glass constituting the boron-containing glass particles include oxides exemplified as oxides that may be contained in the glass constituting the phosphorus-containing glass particles.
It is preferable that the boron-containing glass particles do not contain phosphorus oxide or the content of phosphorus oxide is lower than the content of boron oxide.
　ホウ素含有ガラス粒子は酸化ケイ素、酸化アルミニウム、酸化亜鉛、酸化ビスマス、酸化銅及び酸化リチウムから選択される少なくとも１種を含むことが好ましく、酸化ビスマスを含むことがより好ましく、ビスマス含有ホウ酸塩ガラス（Ｂ２Ｏ３－Ｂｉ２Ｏ３系）等が好ましい例として挙げられる。このような組成のガラスは軟化点が低く、熱処理後に得られる電極の基板への密着性がより向上する傾向にある。 The boron-containing glass particles preferably contain at least one selected from silicon oxide, aluminum oxide, zinc oxide, bismuth oxide, copper oxide and lithium oxide, more preferably bismuth oxide-containing borate glass. (B 2 O 3 -Bi 2 O 3 system) and the like are given as preferable examples. Glass having such a composition has a low softening point, and the adhesion of the electrode obtained after the heat treatment to the substrate tends to be further improved.
　ホウ素含有ガラス粒子が酸化ビスマスを含む場合、酸化ビスマスの含有率が全体の７５．０質量％以上であることが好ましく、８０．０質量％以上であることがより好ましく、８５．０質量％以上であることが更に好ましい。酸化ビスマスの含有率は全体の９７．０質量％以下であることが好ましく、９５．０質量％以下であることがより好ましく、９０．０質量％以下であることが更に好ましい。 When the boron-containing glass particles contain bismuth oxide, the content of bismuth oxide is preferably 75.0% by mass or more, more preferably 80.0% by mass or more, and 85.0% by mass or more. Is more preferable. The content of bismuth oxide is preferably 97.0% by mass or less, more preferably 95.0% by mass or less, and further preferably 90.0% by mass or less.
　ホウ素含有ガラス粒子の粒子径は特に制限されないが、体積平均粒子径が０．２μｍ～１０．０μｍであることが好ましく、０．５μｍ～８．０μｍであることがより好ましい。ホウ素含有ガラス粒子の体積平均粒子径が０．２μｍ以上であると、電極極形成用組成物の製造時の作業性が向上する。ホウ素含有ガラス粒子の体積平均粒子径が１０．０μｍ以下であると、電極形成用組成物中への分散性が向上し、アルミニウム／銀積層電極におけるホウ素の分布の均一性が向上する。
　ホウ素含有ガラス粒子の体積平均粒子径は、銀含有粒子の体積平均粒子径と同様にして測定される。 The particle size of the boron-containing glass particles is not particularly limited, but the volume average particle size is preferably 0.2 μm to 10.0 μm, and more preferably 0.5 μm to 8.0 μm. When the volume average particle diameter of the boron-containing glass particles is 0.2 μm or more, the workability at the time of producing the electrode electrode forming composition is improved. When the volume average particle diameter of the boron-containing glass particles is 10.0 μm or less, the dispersibility in the electrode forming composition is improved, and the uniformity of the distribution of boron in the aluminum / silver laminated electrode is improved.
The volume average particle size of the boron-containing glass particles is measured in the same manner as the volume average particle size of the silver-containing particles.
　電極形成用組成物に含まれるガラス粒子は、１種のみでも２種以上であってもよい。
　電極形成用組成物が２種以上のガラス粒子を含む場合、ガラス粒子のすべてがリンを含有していても、ガラス粒子の少なくともいずれかがリンを含有していてもよい。 The glass particles contained in the electrode forming composition may be only one kind or two or more kinds.
When the composition for forming an electrode contains two or more kinds of glass particles, all of the glass particles may contain phosphorus, or at least one of the glass particles may contain phosphorus.
　ＳｉＮＸ膜の上にアルミニウム／銀積層電極を形成する場合は、鉛を実質的に含まない鉛フリーガラスを用いることが好ましい。鉛フリーガラスとしては、特開２００６－３１３７４４号公報の段落番号００２４～００２５に記載の鉛フリーガラス、特開２００９－１８８２８１号公報等に記載の鉛フリーガラス等が挙げられる。 When forming an aluminum / silver laminated electrode on a SiN X film, it is preferable to use lead-free glass containing substantially no lead. Examples of the lead-free glass include lead-free glass described in paragraphs 0024 to 0025 of JP-A-2006-313744, lead-free glass described in JP-A-2009-188281, and the like.
　ガラス粒子の軟化点は特に制限されないが、６５０℃以下であることが好ましく、５００℃以下であることがより好ましい。ガラス粒子の軟化点は、熱機械分析装置（ＴＭＡ）を用いて通常の方法によって測定される。 The softening point of the glass particles is not particularly limited, but is preferably 650 ° C or lower, and more preferably 500 ° C or lower. The softening point of the glass particles is measured by a conventional method using a thermomechanical analyzer (TMA).
　ガラス粒子の形状は特に制限されず、略球状、扁平状、ブロック状、板状、鱗片状等であってもよい。銀含有粒子及びビスマス含有粒子との濡れ性の観点からは、ガラス粒子の形状は略球状、扁平状又は板状であることが好ましい。 The shape of the glass particles is not particularly limited, and may be substantially spherical, flat, block-shaped, plate-shaped, scale-shaped, or the like. From the viewpoint of wettability with silver-containing particles and bismuth-containing particles, the shape of the glass particles is preferably substantially spherical, flat or plate-shaped.
　電極形成用組成物に含まれるガラス粒子の含有率（リン含有ガラス粒子とリンを含有しないガラス粒子とを含む場合は、その合計含有率）は、電極形成用組成物全体の１．０質量％～１５．０質量％であることが好ましく、３．５質量％～１４．０質量％であることがより好ましく、４．０質量％～１２．０質量％であることが更に好ましい。
　ガラス粒子の含有率を３．０質量％以上とすることで、高温高湿環境下における良好な信頼性が維持される傾向にある。ガラス粒子の含有率を１５．０質量％以下とすることで、アルミニウム電極の上に形成される銀電極の表面の銀濃度が充分に確保され、接続材料の接続強度（はんだの濡れ性）が良好に維持される傾向にある。 The content of the glass particles contained in the electrode forming composition (the total content of the phosphorus-containing glass particles and the phosphorus-free glass particles when they are contained) is 1.0% by mass of the entire electrode forming composition. It is preferably from 15.0% by mass, more preferably from 3.5% by mass to 14.0% by mass, and even more preferably from 4.0% by mass to 12.0% by mass.
By setting the content of the glass particles to 3.0% by mass or more, good reliability in a high temperature and high humidity environment tends to be maintained. By setting the content of the glass particles to 15.0% by mass or less, the silver concentration on the surface of the silver electrode formed on the aluminum electrode is sufficiently secured, and the connection strength (solder wettability) of the connecting material is increased. It tends to be well maintained.
　電極形成用組成物に含まれるガラス粒子の含有量に対するビスマス含有粒子の含有量の質量比（Ｂｉ／Ｇ比）は、０．５～１５．０であることが好ましく、１．０～１２．０であることがより好ましく、１．５～１０．０であることが更に好ましい。Ｂｉ／Ｇ比を０．５以上とすることで、酸化ビスマス相の拡散バリア性が効果的に発現する傾向にある。Ｂｉ／Ｇ比を１５．０以下とすることで、高温高湿環境下における信頼性が効果的に向上する傾向にある。 The mass ratio (Bi / G ratio) of the content of the bismuth-containing particles to the content of the glass particles contained in the electrode forming composition is preferably 0.5 to 15.0, preferably 1.0 to 12. It is more preferably 0, and even more preferably 1.5 to 10.0. By setting the Bi / G ratio to 0.5 or more, the diffusion barrier property of the bismuth oxide phase tends to be effectively exhibited. By setting the Bi / G ratio to 15.0 or less, the reliability in a high temperature and high humidity environment tends to be effectively improved.
（溶剤及び樹脂）
　電極形成用組成物は、溶剤及び樹脂の少なくとも一方を含んでいてもよい。
　電極形成用組成物が溶剤及び樹脂の少なくとも一方を含むことで、電極形成用組成物の液状性（粘度、表面張力等）を、基板等に付与する際の付与方法に適した範囲内に調整することができる。
　電極形成用組成物に含まれる溶剤又は樹脂は、それぞれ１種のみでも２種以上であってもよい。 (Solvent and resin)
The electrode forming composition may contain at least one of a solvent and a resin.
By containing at least one of a solvent and a resin in the electrode forming composition, the liquidity (viscosity, surface tension, etc.) of the electrode forming composition is adjusted within a range suitable for the application method when applied to a substrate or the like. can do.
The solvent or resin contained in the electrode forming composition may be only one type or two or more types, respectively.
　溶剤としては、ヘキサン、シクロヘキサン、トルエン等の炭化水素溶剤、ジクロロエチレン、ジクロロエタン、ジクロロベンゼン等のハロゲン化炭化水素溶剤、テトラヒドロフラン、フラン、テトラヒドロピラン、ピラン、ジオキサン、１，３－ジオキソラン、トリオキサン等の環状エーテル溶剤、Ｎ，Ｎ－ジメチルホルムアミド、Ｎ，Ｎ－ジメチルアセトアミド等のアミド溶剤、ジメチルスルホキシド、ジエチルスルホキシド等のスルホキシド溶剤、アセトン、メチルエチルケトン、ジエチルケトン、シクロヘキサノン等のケトン溶剤、エタノール、２－プロパノール、１－ブタノール、ジアセトンアルコール等のアルコール溶剤、２，２，４－トリメチル－１，３－ペンタンジオールモノアセテート、２，２，４－トリメチル－１，３ペンタンジオールモノプロピオネート、２，２，４－トリメチル－１，３－ペンタンジオールモノブチレート、エチレングリコールモノブチルエーテルアセテート、ジエチレングリコールモノブチルエーテルアセテート等の多価アルコールのエステル溶剤、ブチルセルソルブ、ジエチレングリコールモノブチルエーテル、ジエチレングリコールジエチルエーテル等の多価アルコールのエーテル溶剤、α－テルピネン、α－テルピネオール、ミルセン、アロオシメン、リモネン、ジペンテン、α－ピネン、β－ピネン、ターピネオール、カルボン、オシメン、フェランドレン等のテルペン溶剤などが挙げられる。 Examples of the solvent include hydrocarbon solvents such as hexane, cyclohexane and toluene, halogenated hydrocarbon solvents such as dichloroethylene, dichloroethane and dichlorobenzene, and cyclic compounds such as tetrahydrofuran, furan, tetrahydropyran, pyran, dioxane, 1,3-dioxolane and trioxane. Ether solvent, amide solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, sulfoxide solvent such as dimethylsulfoxide and diethylsulfoxide, ketone solvent such as acetone, methylethylketone, diethylketone, cyclohexanone, ethanol, 2-propanol, Alcohol solvents such as 1-butanol and diacetone alcohol, 2,2,4-trimethyl-1,3-pentanediol monoacetate, 2,2,4-trimethyl-1,3 pentanediol monopropionate, 2,2 , 4-trimethyl-1,3-pentanediol monobutylate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate and other polyvalent alcohol ester solvents, butyl cell solve, diethylene glycol monobutyl ether, diethylene glycol diethyl ether and other polyvalent alcohols. Examples thereof include ether solvents, α-terpineol, α-terpineol, milsen, aloosimene, limonene, dipentene, α-pinene, β-pinene, tarpineol, carboxylic, osimene, ferlandren and the like.
　溶剤は、電極形成用組成物の付与性（例えば、塗布性又は印刷性）の観点からは、溶剤は多価アルコールのエステル溶剤、テルペン溶剤及び多価アルコールのエーテル溶剤からなる群より選択される少なくとも１種を含むことが好ましく、多価アルコールのエステル溶剤及びテルペン溶剤からなる群より選択される少なくとも１種を含むことがより好ましい。 The solvent is selected from the group consisting of an ester solvent of a polyhydric alcohol, a terpene solvent and an ether solvent of a polyhydric alcohol from the viewpoint of imparting property (for example, coatability or printability) of the composition for forming an electrode. It is preferable to contain at least one kind, and it is more preferable to contain at least one kind selected from the group consisting of an ester solvent of a polyhydric alcohol and a terpene solvent.
　樹脂は、熱処理によって熱分解されうる樹脂であれば特に制限されず、天然高分子であっても、合成高分子であってもよい。具体的には、メチルセルロース、エチルセルロース、カルボキシメチルセルロース、ニトロセルロース等のセルロース樹脂、ポリビニルアルコール化合物、ポリビニルピロリドン化合物、アクリル樹脂、酢酸ビニル－アクリル酸エステル共重合体、ポリビニルブチラール等のブチラール樹脂、フェノール変性アルキド樹脂、ひまし油脂肪酸変性アルキド樹脂等のアルキド樹脂、エポキシ樹脂、フェノール樹脂、ロジンエステル樹脂などが挙げられる。 The resin is not particularly limited as long as it is a resin that can be thermally decomposed by heat treatment, and may be a natural polymer or a synthetic polymer. Specifically, cellulose resins such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose and nitrocellulose, polyvinyl alcohol compounds, polyvinyl pyrrolidone compounds, acrylic resins, vinyl acetate-acrylic acid ester copolymers, butyral resins such as polyvinyl butyral, and phenol-modified alkyds. Examples thereof include resins, alkyd resins such as castor oil fatty acid-modified alkyd resins, epoxy resins, phenolic resins, and rosin ester resins.
　熱処理による熱分解性の観点からは、樹脂はセルロース樹脂及びアクリル樹脂からなる群より選択される少なくとも１種を含むことが好ましい。 From the viewpoint of thermal decomposition by heat treatment, it is preferable that the resin contains at least one selected from the group consisting of cellulose resin and acrylic resin.
　樹脂の重量平均分子量は、特に制限されない。中でも樹脂の重量平均分子量は、５，０００～５００，０００が好ましく、１０，０００～３００，０００であることがより好ましい。樹脂の重量平均分子量が５，０００以上であると、電極形成用組成物の粘度の増加が抑制できる傾向にある。これは例えば、樹脂が粒子に吸着したときの立体的な反発作用が充分となり、これら樹脂同士の凝集が抑制されるためと考えることができる。一方、樹脂の重量平均分子量が５００，０００以下であると、樹脂同士が溶剤中で凝集することが抑制され、電極形成用組成物の粘度の増加が抑制できる傾向にある。また樹脂の重量平均分子量が５００，０００以下であると、樹脂の燃焼温度が高すぎて電極形成用組成物を熱処理する際に燃焼されずに異物として残存することが抑制され、より低抵抗率な電極を形成することができる傾向にある。 The weight average molecular weight of the resin is not particularly limited. Among them, the weight average molecular weight of the resin is preferably 5,000 to 500,000, more preferably 10,000 to 300,000. When the weight average molecular weight of the resin is 5,000 or more, the increase in the viscosity of the electrode forming composition tends to be suppressed. It can be considered that this is because, for example, the three-dimensional repulsive action when the resin is adsorbed on the particles is sufficient, and the aggregation of these resins is suppressed. On the other hand, when the weight average molecular weight of the resin is 500,000 or less, the resins are suppressed from aggregating with each other in the solvent, and the increase in the viscosity of the electrode forming composition tends to be suppressed. Further, when the weight average molecular weight of the resin is 500,000 or less, the combustion temperature of the resin is too high and it is suppressed that the composition for forming the electrode is not burned and remains as a foreign substance when the composition is heat-treated, and the resistance is lower. There is a tendency to be able to form various electrodes.
　重量平均分子量はＧＰＣ（ゲルパーミエーションクロマトグラフィー）を用いて測定される分子量分布から標準ポリスチレンの検量線を使用して換算して求められる。検量線は、標準ポリスチレンの５サンプルセット（ＰＳｔＱｕｉｃｋ　ＭＰ－Ｈ、ＰＳｔＱｕｉｃｋ　Ｂ、東ソー（株））を用いて３次元で近似する。ＧＰＣの測定条件は、以下の通りである。
　・装置：（ポンプ：Ｌ－２１３０型［（株）日立ハイテクノロジーズ］）、（検出器：Ｌ－２４９０型ＲＩ［（株）日立ハイテクノロジーズ］）、（カラムオーブン：Ｌ－２３５０［（株）日立ハイテクノロジーズ］）
　・カラム：Ｇｅｌｐａｃｋ　ＧＬ－Ｒ４４０　＋　Ｇｅｌｐａｃｋ　ＧＬ－Ｒ４５０　＋　Ｇｅｌｐａｃｋ　ＧＬ－Ｒ４００Ｍ（計３本）（日立化成（株））
　・カラムサイズ：１０．７ｍｍ×３００ｍｍ（内径）
　・溶離液：テトラヒドロフラン
　・試料濃度：１０ｍｇ／２ｍＬ
　・注入量：２００μＬ
　・流量：２．０５ｍＬ／分
　・測定温度：２５℃ The weight average molecular weight is obtained by converting the molecular weight distribution measured by GPC (gel permeation chromatography) using a standard polystyrene calibration curve. The calibration curve is approximated in three dimensions using a 5-sample set of standard polystyrene (PStQuick MP-H, PStQuick B, Tosoh Corporation). The measurement conditions of GPC are as follows.
-Equipment: (Pump: L-2130 type [Hitachi High-Technologies Corporation]), (Detector: L-2490 type RI [Hitachi High-Technologies Corporation]), (Column oven: L-2350 [Co., Ltd.] Hitachi High-Technologies])
-Column: Gelpack GL-R440 + Gelpack GL-R450 + Gelpack GL-R400M (3 in total) (Hitachi Kasei Co., Ltd.)
-Column size: 10.7 mm x 300 mm (inner diameter)
・ Eluent: Tetrahydrofuran ・ Sample concentration: 10 mg / 2 mL
・ Injection amount: 200 μL
・ Flow rate: 2.05 mL / min ・ Measurement temperature: 25 ° C
　電極形成用組成物が溶剤及び樹脂を含む場合、溶剤及び樹脂の含有率は、電極形成用組成物の所望の液物性、使用する溶剤及び樹脂の種類等に応じて選択できる。
　例えば、溶剤及び樹脂の合計含有率は、電極形成用組成物全体の３．０質量％～７０．０質量％であることが好ましく、２０．０質量％～５５．０質量％であることがより好ましく、３０．０質量％～５０．０質量％であることが更に好ましい。
　溶剤及び樹脂の総含有率が上記範囲内であることにより、電極形成用組成物を基板に付与する際の付与適性が良好になり、所望の幅及び高さを有する電極をより容易に形成することができる傾向にある。
　電極形成用組成物が溶剤及び樹脂を含む場合、溶剤及び樹脂の含有比は、電極形成用組成物が所望の液物性となるように、使用する溶剤及び樹脂の種類に応じて適宜選択することができる。 When the electrode forming composition contains a solvent and a resin, the content of the solvent and the resin can be selected according to the desired liquid physical characteristics of the electrode forming composition, the type of the solvent and the resin to be used, and the like.
For example, the total content of the solvent and the resin is preferably 3.0% by mass to 70.0% by mass, and preferably 20.0% by mass to 55.0% by mass, based on the entire composition for forming an electrode. More preferably, it is 30.0% by mass to 50.0% by mass.
When the total content of the solvent and the resin is within the above range, the aptitude for applying the electrode-forming composition to the substrate becomes good, and an electrode having a desired width and height can be more easily formed. Tend to be able to.
When the electrode forming composition contains a solvent and a resin, the content ratio of the solvent and the resin shall be appropriately selected according to the type of the solvent and the resin used so that the electrode forming composition has the desired liquid physical characteristics. Can be done.
　電極形成用組成物は、銀含有粒子の焼結性、ビスマス含有粒子の拡散バリア性、ガラス粒子によるアルミニウム電極の強度及び密着性の向上効果等の観点から、銀含有粒子、ビスマス含有粒子及びガラス粒子の合計含有率が、電極形成用組成物全体の３０．０質量％以上９７．０質量％以下であることが好ましく、４５．０質量％以上８０．０質量％以下であることがより好ましく、５０．０質量％以上７０．０質量％以下であることが更に好ましい。 The electrode-forming composition includes silver-containing particles, bis-mass-containing particles, and glass from the viewpoints of the sintering property of silver-containing particles, the diffusion barrier property of bismuth-containing particles, and the effect of improving the strength and adhesion of aluminum electrodes by glass particles. The total content of the particles is preferably 30.0% by mass or more and 97.0% by mass or less, and more preferably 45.0% by mass or more and 80.0% by mass or less of the entire composition for forming an electrode. It is more preferably 50.0% by mass or more and 70.0% by mass or less.
（その他の成分）
　電極形成用組成物は、上述した成分に加え、当該技術分野で通常用いられるその他の成分を更に含有してよい。その他の成分としては、可塑剤、分散剤、界面活性剤、増粘剤、無機結合剤、金属酸化物（酸化ビスマスを除く）、セラミックス、有機金属化合物等を挙げることができる。 (Other ingredients)
In addition to the above-mentioned components, the electrode-forming composition may further contain other components usually used in the art. Examples of other components include plasticizers, dispersants, surfactants, thickeners, inorganic binders, metal oxides (excluding bismuth oxide), ceramics, organic metal compounds and the like.
（電極形成用組成物の製造方法）
　電極形成用組成物の製造方法は、特に制限されない。例えば、銀含有粒子、ビスマス含有粒子、ガラス粒子及び必要に応じて用いられるその他の成分を分散及び混合することで製造することができる。分散及び混練の方法は特に制限されず、通常用いられる方法から選択して適用することができる。 (Method for manufacturing electrode forming composition)
The method for producing the electrode-forming composition is not particularly limited. For example, it can be produced by dispersing and mixing silver-containing particles, bismuth-containing particles, glass particles and other components used as necessary. The method of dispersion and kneading is not particularly limited, and can be selected and applied from commonly used methods.
＜アルミニウム／銀積層電極＞
　本開示の一実施形態に係るアルミニウム／銀積層電極は、上述した電極形成用組成物の熱処理物を含み、かつ、アルミニウムを含む第１電極と、前記第１電極の上に配置される銀を含む第２電極とを備え、前記第１電極は酸化ビスマス相及びリンを含有するガラス相を更に含む、アルミニウム／銀積層電極である。 <Aluminum / Silver laminated electrode>
The aluminum / silver laminated electrode according to the embodiment of the present disclosure contains the heat-treated product of the above-mentioned electrode forming composition, and contains a first electrode containing aluminum and silver arranged on the first electrode. The first electrode is an aluminum / silver laminated electrode including a second electrode containing a bismuth oxide phase and a glass phase containing phosphorus.
　第１電極が酸化ビスマス相及びガラス相を含むか否かは、透過型電子顕微鏡を用いて確認できる。具体的には、結晶Ｂｉ２Ｏ３の格子縞（原子の配列）の存在によって酸化ビスマス相の存在を確認でき、アモルファス特有の組織の存在によってガラス相の存在を確認できる。透過型電子顕微鏡の拡大倍率は、例えば、数十万倍に設定する。 Whether or not the first electrode contains the bismuth oxide phase and the glass phase can be confirmed by using a transmission electron microscope. Specifically, the presence of the bismuth oxide phase can be confirmed by the presence of lattice stripes (atomic arrangement) of the crystal Bi 2 O 3 , and the presence of the glass phase can be confirmed by the presence of a structure peculiar to amorphous. The magnification of the transmission electron microscope is set to, for example, several hundred thousand times.
　太陽電池素子の発電性能の観点からは、第１電極に含まれるガラス相はホウ素を更に含むことが好ましい。 From the viewpoint of the power generation performance of the solar cell element, it is preferable that the glass phase contained in the first electrode further contains boron.
　上記構成のアルミニウム／銀積層電極は、太陽電池素子を構成する基板の上に配置されることが好ましく、太陽電池素子の裏面に相当する側に配置されることがより好ましい。
　本開示において「基板の上」には、基板の表面に形成されるパッシベーション膜、パッシベーション膜の保護膜等の膜の上も含まれる。 The aluminum / silver laminated electrode having the above configuration is preferably arranged on the substrate constituting the solar cell element, and more preferably arranged on the side corresponding to the back surface of the solar cell element.
In the present disclosure, "on the substrate" also includes a film such as a passivation film formed on the surface of the substrate and a protective film of the passivation film.
　アルミニウムを含む第１電極の厚み（厚みが一定でない場合は、最小厚み）は、例えば、０．５μｍ～５０．０μｍの範囲であってよい。
　銀を含む第２電極の厚み（厚みが一定でない場合は、最小厚み）は、例えば、０．５μｍ～３０．０μｍの範囲であってよい。 The thickness of the first electrode containing aluminum (or the minimum thickness if the thickness is not constant) may be, for example, in the range of 0.5 μm to 50.0 μm.
The thickness of the second electrode containing silver (or the minimum thickness if the thickness is not constant) may be, for example, in the range of 0.5 μm to 30.0 μm.
　上記構成のアルミニウム／銀積層電極は、例えば、上述した電極形成用組成物を用いて製造することができる。
　電極形成用組成物を用いて製造されるアルミニウム／銀積層電極及びこれを含む太陽電池素子の構造の一例について、図１を用いて説明する。
　図１は、電極形成用組成物を用いて作製したＰＥＲＣ構造の太陽電池素子の裏面電極の断面模式図である。図１に示すように、半導体基板１の表面にはパッシベーション膜１８及び保護膜１９（ＳｉＮＸ）がこの順で成膜され、その上にアルミニウム電極（アルミニウム粒子焼結部とも言う）５及びアルミニウム／銀積層電極８が形成されている。
　アルミニウム／銀積層電極８は、アルミニウム電極と銀電極（銀粒子焼結部ともいう）とが積層された箇所を含む。例えば、アルミニウム／銀積層電極８の最表面に、銀粒子焼結部が形成されてよい。また、アルミニウム電極５と、アルミニウム／銀積層電極８を構成するアルミニウム電極とは、同時に形成されてよい。 The aluminum / silver laminated electrode having the above configuration can be produced, for example, by using the above-mentioned electrode forming composition.
An example of the structure of an aluminum / silver laminated electrode manufactured by using the electrode forming composition and a solar cell element including the same will be described with reference to FIG. 1.
FIG. 1 is a schematic cross-sectional view of a back surface electrode of a solar cell element having a PERC structure produced by using an electrode forming composition. As shown in FIG. 1, a passivation film 18 and a protective film 19 (SiN X ) are formed on the surface of the semiconductor substrate 1 in this order, and an aluminum electrode (also referred to as an aluminum particle sintered portion) 5 and aluminum are formed on the passivation film 18 and the protective film 19 (SiN X) in this order. / The silver laminated electrode 8 is formed.
The aluminum / silver laminated electrode 8 includes a portion where the aluminum electrode and the silver electrode (also referred to as a silver particle sintered portion) are laminated. For example, a silver particle sintered portion may be formed on the outermost surface of the aluminum / silver laminated electrode 8. Further, the aluminum electrode 5 and the aluminum electrode constituting the aluminum / silver laminated electrode 8 may be formed at the same time.
（アルミニウム／銀積層電極の製造方法）
　電極形成用組成物を用いてアルミニウム／銀積層電極を製造する方法は特に制限されない。
　例えば、半導体基板の上にアルミニウム粒子含有膜を形成する工程と、電極形成用組成物を、アルミニウム粒子含有膜の上に付与し、必要に応じて乾燥する工程と、アルミニウム粒子含有膜及び電極形成用組成物を熱処理する工程と、をこの順に実施する方法が挙げられる。 (Manufacturing method of aluminum / silver laminated electrode)
The method for producing an aluminum / silver laminated electrode using the electrode forming composition is not particularly limited.
For example, a step of forming an aluminum particle-containing film on a semiconductor substrate, a step of applying an electrode-forming composition onto the aluminum particle-containing film and drying it as necessary, and forming an aluminum particle-containing film and an electrode. Examples thereof include a step of heat-treating the composition for use and a method of carrying out the steps in this order.
　アルミニウム粒子含有膜は、パッシベーション膜及び保護膜（ＳｉＮＸ）が成膜された半導体基板上に形成されてよい。また、アルミニウム粒子含有膜は、半導体基板上に付与したアルミニウム電極形成組成物を乾燥して形成されてよい。半導体基板は、シリコン（Ｓｉ）基板であってよい。アルミニウム電極形成用組成物を用いて、アルミニウム粒子含有膜を半導体基板上に形成する場合の、アルミニウム電極形成用組成物を付与する方法としては、スクリーン印刷法、インクジェット法、ディスペンサー法等を挙げることができ、生産性の観点から、スクリーン印刷法が好ましい。アルミニウム電極形成用組成物を付与した後の乾燥条件としては、当該技術分野で通常用いられる熱処理条件を適用することができる。 The aluminum particle-containing film may be formed on a semiconductor substrate on which a passivation film and a protective film (SiN X ) are formed. Further, the aluminum particle-containing film may be formed by drying the aluminum electrode forming composition applied on the semiconductor substrate. The semiconductor substrate may be a silicon (Si) substrate. Examples of the method for applying the aluminum electrode forming composition when the aluminum particle-containing film is formed on the semiconductor substrate by using the aluminum electrode forming composition include a screen printing method, an inkjet method, a dispenser method and the like. The screen printing method is preferable from the viewpoint of productivity. As the drying conditions after applying the composition for forming an aluminum electrode, heat treatment conditions usually used in the art can be applied.
　電極形成用組成物を、アルミニウム粒子含有膜上に付与する方法としては、スクリーン印刷法、インクジェット法、ディスペンサー法等を挙げることができ、生産性の観点から、スクリーン印刷法が好ましい。 Examples of the method for applying the electrode forming composition onto the aluminum particle-containing film include a screen printing method, an inkjet method, a dispenser method, and the like, and the screen printing method is preferable from the viewpoint of productivity.
　電極形成用組成物をスクリーン印刷法によってアルミニウム粒子含有膜上に付与する場合、電極形成用組成物は、ペースト状であることが好ましい。ペースト状の電極形成用組成物は、２０Ｐａ・ｓ～１０００Ｐａ・ｓの範囲の粘度を有することが好ましい。尚、電極形成用組成物の粘度は、ブルックフィールドＨＢＴ粘度計を用いて２５℃で測定される。 When the electrode forming composition is applied onto the aluminum particle-containing film by a screen printing method, the electrode forming composition is preferably in the form of a paste. The paste-like electrode-forming composition preferably has a viscosity in the range of 20 Pa · s to 1000 Pa · s. The viscosity of the electrode forming composition is measured at 25 ° C. using a Brookfield HBT viscometer.
　電極形成用組成物のアルミニウム粒子含有膜への付与量は、形成する電極の大きさに応じて適宜選択することができる。例えば、電極形成用組成物の付与量としては、１．０ｍｇ／ｃｍ２～２０．０ｍｇ／ｃｍ２とすることができ、２．０ｍｇ／ｃｍ２～１５．０ｍｇ／ｃｍ２であることが好ましい。 The amount of the electrode-forming composition applied to the aluminum particle-containing film can be appropriately selected according to the size of the electrode to be formed. For example, the amount of the electrode-forming composition applied can be 1.0 mg / cm 2 to 20.0 mg / cm 2 , preferably 2.0 mg / cm 2 to 15.0 mg / cm 2 . ..
　また、電極形成用組成物を用いてアルミニウム／銀積層電極を形成する際の熱処理条件としては、当該技術分野で通常用いられる熱処理条件を適用することができる。熱処理温度としては、一般的な結晶シリコン系太陽電池素子を製造する際に用いられる７００℃～９００℃の範囲を好適に用いることができる。
　また熱処理時間は、熱処理温度に応じて適宜選択することができ、例えば、１秒～２０秒とすることができる。 Further, as the heat treatment conditions for forming the aluminum / silver laminated electrode using the electrode forming composition, the heat treatment conditions usually used in the art can be applied. As the heat treatment temperature, a range of 700 ° C. to 900 ° C., which is used when manufacturing a general crystalline silicon solar cell element, can be preferably used.
The heat treatment time can be appropriately selected according to the heat treatment temperature, and can be, for example, 1 second to 20 seconds.
　熱処理装置としては、上記温度に加熱できるものであれば適宜採用することができ、赤外線加熱炉、トンネル炉等を挙げることができる。赤外線加熱炉は、電気エネルギーを電磁波の形で加熱材料に投入し熱エネルギーに変換されるため高効率であり、また、より短時間での急速加熱が可能である。更に、燃焼による生成物が少なく、また非接触加熱であるため、生成する電極の汚染を抑えることが可能である。トンネル炉は、試料を自動で連続的に入り口から出口へ搬送し、熱処理するため、炉体の区分けと搬送スピードの制御によって、より均一に熱処理することが可能である。太陽電池素子の発電性能の観点からは、トンネル炉により熱処理することが好適である。 As the heat treatment apparatus, any one that can be heated to the above temperature can be appropriately adopted, and examples thereof include an infrared heating furnace, a tunnel furnace, and the like. The infrared heating furnace is highly efficient because electric energy is input to the heating material in the form of electromagnetic waves and converted into heat energy, and rapid heating in a shorter time is possible. Furthermore, since there are few products due to combustion and non-contact heating is used, it is possible to suppress contamination of the generated electrodes. Since the tunnel furnace automatically and continuously transports the sample from the inlet to the outlet and heat-treats it, it is possible to heat-treat more uniformly by classifying the furnace body and controlling the transport speed. From the viewpoint of the power generation performance of the solar cell element, it is preferable to heat-treat in a tunnel furnace.
　以下、アルミニウム／銀積層電極の製造方法の具体例を、図面を参照しながら説明する。ただし、本開示はこれに限定されるものではない。代表的なアルミニウム／銀積層電極の製造方法の一例を、図２Ａ～図２Ｃに示す。 Hereinafter, a specific example of the manufacturing method of the aluminum / silver laminated electrode will be described with reference to the drawings. However, this disclosure is not limited to this. An example of a typical method for manufacturing an aluminum / silver laminated electrode is shown in FIGS. 2A to 2C.
　まず図２Ａに示すように、パッシベーション膜１８及び保護膜（ＳｉＮＸ）１９が成膜された半導体基板１の一方の面に、ペースト状のアルミニウム電極形成用組成物２を、スクリーン印刷法で塗布する。これを１５０℃程度の温度で加熱し、アルミニウム電極形成用組成物２中の溶剤を除去する。これにより、図２Ｂに示すように、パッシベーション膜１８及び保護膜（ＳｉＮＸ）１９が成膜された半導体基板１上にアルミニウム粒子含有膜３が形成される。
　次いで、アルミニウム粒子含有膜３上の所望の領域に、電極形成用組成物４を塗布し、これを１５０℃程度の温度で加熱し、乾燥する。なお、電極形成用組成物４がペースト状の場合は、アルミニウム電極形成用組成物２と同様、スクリーン印刷法で塗布される。その後、これを上述した条件で熱処理する。これにより、図２Ｃに示すように、アルミニウム／銀積層電極８が、パッシベーション膜１８及び保護膜（ＳｉＮＸ）１９が成膜された半導体基板１上に形成される。
　アルミニウム／銀積層電極８は、最表面に銀粒子焼結部７が配置され、銀粒子焼結部７とパッシベーション膜１８及び保護膜（ＳｉＮＸ）１９が成膜された半導体基板１との間には、アルミニウム粒子焼結部／酸化ビスマス相混合部６が配置される。 First, as shown in FIG. 2A, the paste-like aluminum electrode forming composition 2 is applied to one surface of the semiconductor substrate 1 on which the passivation film 18 and the protective film (SiN X ) 19 are formed by a screen printing method. do. This is heated at a temperature of about 150 ° C. to remove the solvent in the composition 2 for forming an aluminum electrode. As a result, as shown in FIG. 2B, the aluminum particle-containing film 3 is formed on the semiconductor substrate 1 on which the passivation film 18 and the protective film ( SiNX ) 19 are formed.
Next, the electrode-forming composition 4 is applied to a desired region on the aluminum particle-containing film 3, heated at a temperature of about 150 ° C., and dried. When the electrode forming composition 4 is in the form of a paste, it is applied by a screen printing method in the same manner as the aluminum electrode forming composition 2. Then, this is heat-treated under the above-mentioned conditions. As a result, as shown in FIG. 2C, the aluminum / silver laminated electrode 8 is formed on the semiconductor substrate 1 on which the passivation film 18 and the protective film (SiN X ) 19 are formed.
The aluminum / silver laminated electrode 8 has a silver particle sintered portion 7 arranged on the outermost surface, and is between the silver particle sintered portion 7 and the semiconductor substrate 1 on which the passion film 18 and the protective film (SiN X ) 19 are formed. The aluminum particle sintered portion / bismuth oxide phase mixing portion 6 is arranged in the room.
　図３は、図２Ｃのうち、アルミニウム／銀積層電極の形成箇所を拡大して示したものである。図３に示すように、アルミニウム粒子焼結部／酸化ビスマス相混合部６は、アルミニウム粒子焼結部５と、アルミニウム粒子焼結部５の空隙部に充填された酸化ビスマス相９とを含む。アルミニウム粒子焼結部／酸化ビスマス相混合部６がこのような構成を有するのは、上述したように、電極形成用組成物４中のビスマス含有粒子の一部又は全体が熱処理によりアルミニウム粒子含有膜３に移行するためである。 FIG. 3 is an enlarged view of the formed portion of the aluminum / silver laminated electrode in FIG. 2C. As shown in FIG. 3, the aluminum particle sintered portion / bismuth oxide phase mixing portion 6 includes an aluminum particle sintered portion 5 and a bismuth oxide phase 9 filled in a void portion of the aluminum particle sintered portion 5. The reason why the aluminum particle sintered portion / bismuth oxide phase mixing portion 6 has such a configuration is that, as described above, a part or the whole of the bismuth-containing particles in the electrode forming composition 4 is heat-treated to form an aluminum particle-containing film. This is to move to 3.
　酸化ビスマス相９は、銀粒子焼結部７とアルミニウム粒子焼結部５とを隔てるように配置されていてもよく、アルミニウム粒子焼結部５中のアルミニウム粒子と、銀粒子焼結部７とが接触している箇所が部分的に形成されてもよい。この場合、アルミニウム粒子と銀粒子との過度の相互拡散が抑制される程度に、銀粒子焼結部７とアルミニウム粒子焼結部５とを隔てるように酸化ビスマス相９が配置されていることが好ましい。 The bismuth oxide phase 9 may be arranged so as to separate the silver particle sintered portion 7 and the aluminum particle sintered portion 5, and the aluminum particles in the aluminum particle sintered portion 5 and the silver particle sintered portion 7 May be partially formed where the particles are in contact with each other. In this case, the bismuth oxide phase 9 is arranged so as to separate the silver particle sintered portion 7 and the aluminum particle sintered portion 5 to the extent that excessive mutual diffusion between the aluminum particles and the silver particles is suppressed. preferable.
＜太陽電池素子＞
　本開示の一実施形態に係る太陽電池素子は、半導体基板と、前記半導体基板上に設けられるパッシベーション膜と、前記パッシベーション膜上に設けられる上述した電極形成用組成物の熱処理物を含むアルミニウム／銀積層電極と、を有する太陽電池素子である。 <Solar cell element>
The solar cell element according to the embodiment of the present disclosure is aluminum / silver including a semiconductor substrate, a passivation film provided on the semiconductor substrate, and a heat-treated product of the above-mentioned electrode forming composition provided on the passivation film. It is a solar cell element having a laminated electrode.
　上記太陽電池素子は、必要に応じ、半導体基板の上に設けられるパッシベーション膜を保護するための保護膜を備えてもよい。
　上記太陽電池素子のアルミニウム／銀積層電極は、半導体基板の裏面に設けられるものであってもよい。また、上記太陽電池素子はＰＥＲＣ構造を有するものであってもよい。 The solar cell element may be provided with a protective film for protecting the passivation film provided on the semiconductor substrate, if necessary.
The aluminum / silver laminated electrode of the solar cell element may be provided on the back surface of the semiconductor substrate. Further, the solar cell element may have a PERC structure.
　以下、太陽電池素子の構成の具体例を、図面を参照しながら説明するが、本開示はこれに限定されるものではない。代表的な太陽電池素子の一例を、図４、図５Ａ、図５Ｂ、図６Ａ、図６Ｂ及び図６Ｃに示す。 Hereinafter, specific examples of the configuration of the solar cell element will be described with reference to the drawings, but the present disclosure is not limited to this. An example of a typical solar cell element is shown in FIGS. 4, 5A, 5B, 6A, 6B and 6C.
　図４は、太陽電池素子の受光面側の概略平面図である。図４に示す受光面電極１４は、一般的には銀電極ペーストを用いて形成される。具体的には、反射防止膜１３上に銀電極ペーストを所望のパターンで付与し、乾燥した後、大気中７００℃～９００℃程度で熱処理して形成される。 FIG. 4 is a schematic plan view of the light receiving surface side of the solar cell element. The light receiving surface electrode 14 shown in FIG. 4 is generally formed by using a silver electrode paste. Specifically, a silver electrode paste is applied onto the antireflection film 13 in a desired pattern, dried, and then heat-treated at about 700 ° C. to 900 ° C. in the atmosphere to form the paste.
　図５Ａは、太陽電池素子の裏面の概略平面図である。図５Ａに示す太陽電池素子の裏面には、アルミニウム電極５が全面に形成されている。図５Ｂは、太陽電池素子の裏面のうち、アルミニウムフィンガー電極２０及びアルミニウムバスバー電極２１が裏面の一部に形成された場合の概略平面図である。
　太陽電池素子の裏面には、上述したように、アルミニウム電極形成用組成物の付与及び乾燥後、電極形成用組成物を所望のパターンで付与し乾燥する。次いで、これを大気中７００℃～９００℃程度で熱処理して、アルミニウム／銀積層電極を形成する。熱処理は、上述した受光面電極１４の形成のための熱処理と一括して行ってもよい。 FIG. 5A is a schematic plan view of the back surface of the solar cell element. An aluminum electrode 5 is formed on the entire surface of the back surface of the solar cell element shown in FIG. 5A. FIG. 5B is a schematic plan view of the back surface of the solar cell element when the aluminum finger electrode 20 and the aluminum bus bar electrode 21 are formed on a part of the back surface.
As described above, after the aluminum electrode forming composition is applied and dried on the back surface of the solar cell element, the electrode forming composition is applied in a desired pattern and dried. Next, this is heat-treated at about 700 ° C. to 900 ° C. in the atmosphere to form an aluminum / silver laminated electrode. The heat treatment may be performed collectively with the heat treatment for forming the light receiving surface electrode 14 described above.
　図６Ａ～６Ｃの概略断面図に示すように、半導体基板１の一方の面の表面付近には、ｎ＋型拡散層１２が形成され、ｎ＋型拡散層１２上に出力取出電極１４及び反射防止膜１３が形成されている。 As shown in the schematic cross-sectional views of FIGS. 6A to 6C, an n + type diffusion layer 12 is formed near the surface of one surface of the semiconductor substrate 1, and an output extraction electrode 14 and reflection are formed on the n + type diffusion layer 12. The prevention film 13 is formed.
　図６Ａは図５ＡにおけるＡ－Ａ´部の切断面である。Ａ－Ａ´断面が裏面パッシベーション膜の開口部を横切らない場合、裏面は図６Ａに示す構造をもつ。図６Ｂは、図５ＢにおけるＢ－Ｂ´部の切断面である。Ｂ－Ｂ´断面が裏面パッシベーション膜の開口部を横切らない場合、裏面は図６Ｂに示す構造をもつ。図６Ｃは、図５ＢにおけるＣ－Ｃ´部の切断面である。Ｃ－Ｃ´断面が裏面パッシベーション膜の開口部（アルミニウムフィンガー電極２０）を横切る場合、裏面は図６Ｃに示す構造をもつ。 FIG. 6A is a cut surface of the AA'part in FIG. 5A. When the AA'cross section does not cross the opening of the back surface passivation membrane, the back surface has the structure shown in FIG. 6A. FIG. 6B is a cut surface of the BB'part in FIG. 5B. If the BB'cross section does not cross the opening of the backside passivation membrane, the backside has the structure shown in FIG. 6B. FIG. 6C is a cut surface of the CC'part in FIG. 5B. When the CC'cross section crosses the opening of the back surface passivation film (aluminum finger electrode 20), the back surface has the structure shown in FIG. 6C.
　図６Ａ～図６Ｃに示すように、受光面側では、熱処理によって受光面電極１４を形成する銀電極ペーストに含まれるガラス粒子と、反射防止膜１３とが反応（ファイアースルー）して、受光面電極１４とｎ＋型拡散層１２とが電気的に接続（オーミックコンタクト）される。
　裏面側では、熱処理によってアルミニウム電極５、アルミニウムフィンガー電極２０又はアルミニウムバスバー電極２１中のアルミニウムが半導体基板１の裏面の一部（裏面パッシベーション膜成膜部をレーザーなどで除去した部分）に拡散して、ｐ＋型拡散層１５を形成することによって、半導体基板１とアルミニウム電極１５との間にオーミックコンタクトが部分的に形成される。 As shown in FIGS. 6A to 6C, on the light receiving surface side, the glass particles contained in the silver electrode paste forming the light receiving surface electrode 14 by heat treatment react (fire through) with the antireflection film 13 to cause a light receiving surface. The electrode 14 and the n + type diffusion layer 12 are electrically connected (omic contact).
On the back surface side, the aluminum in the aluminum electrode 5, the aluminum finger electrode 20, or the aluminum bus bar electrode 21 is diffused to a part of the back surface of the semiconductor substrate 1 (the portion where the back surface passivation film film-forming portion is removed by a laser or the like) by heat treatment. By forming the p + type diffusion layer 15, an ohmic contact is partially formed between the semiconductor substrate 1 and the aluminum electrode 15.
　以下、本開示の内容を実施例及び比較例を用いてより詳細に説明するが、本開示の範囲は以下の実施例に限定されるものではない。 Hereinafter, the contents of the present disclosure will be described in more detail using Examples and Comparative Examples, but the scope of the present disclosure is not limited to the following Examples.
　以下の実施例において、ガラス粒子の形状は、走査型電子顕微鏡（日立ハイテクノロジーズ社、ＴＭ－１０００）を用いて観察して判定した。ガラス粒子の体積平均粒子径（Ｄ５０％）はレーザー散乱回折法粒度分布測定装置（ベックマン・コールター社、ＬＳ　１３　３２０型、測定波長：６３２ｎｍ）を用いて算出した。ガラス粒子の軟化点は、示差熱・熱重量同時測定装置（株式会社島津製作所、ＤＴ－６０Ｈ）を用いて測定される示差熱（ＤＴＡ）曲線から求めた。具体的には、ＤＴＡ曲線において、吸熱部から軟化点を見積もることができる。 In the following examples, the shape of the glass particles was determined by observing using a scanning electron microscope (Hitachi High-Technologies Corporation, TM-1000). The volume average particle diameter (D50%) of the glass particles was calculated using a laser scattering diffraction method particle size distribution measuring device (Beckman Coulter, LS 13, 320 type, measuring wavelength: 632 nm). The softening point of the glass particles was determined from a differential thermal (DTA) curve measured using a differential thermal / thermogravimetric simultaneous measuring device (Shimadzu Seisakusho Co., Ltd., DT-60H). Specifically, in the DTA curve, the softening point can be estimated from the endothermic portion.
＜実施例１＞
（１）リン酸塩ガラス粒子の調製
　酸化リン（Ｐ２Ｏ５）３８．０質量％、酸化錫（ＳｎＯ）５７．９質量％、酸化亜鉛（ＺｎＯ）３．５質量％及び酸化アルミニウム（Ａｌ２Ｏ３）１．５質量％からなるリン酸塩ガラスを得た。得られたリン酸塩ガラスの軟化点は３４０℃であった。リン酸塩ガラスを用いて、体積平均粒子径が１５．０μｍであるリン酸塩ガラス粒子を得た。粒子の形状は略球状であった。 <Example 1>
(1) Preparation of Phosphate Glass Particles Phosphorus oxide (P 2 O 5 ) 38.0% by mass, tin oxide (SnO) 57.9% by mass, zinc oxide (ZnO) 3.5% by mass and aluminum oxide (Al). 2 O 3 ) Phosphate glass composed of 1.5% by mass was obtained. The softening point of the obtained phosphate glass was 340 ° C. Using phosphate glass, phosphate glass particles having a volume average particle diameter of 15.0 μm were obtained. The shape of the particles was substantially spherical.
（２）ホウ酸塩ガラス粒子の調製
　二酸化ケイ素（ＳｉＯ２）１．4質量％、酸化ホウ素（Ｂ２Ｏ３）１２．５質量％、酸化ビスマス（Ｂｉ２Ｏ３）８５．３質量％及び酸化リチウム（Ｌｉ２Ｏ）０．９質量％からなるホウ酸塩ガラスを得た。得られたホウ酸塩ガラスの軟化点は４４０℃であった。ホウ酸塩ガラスを用いて、体積平均粒子径が１．１μｍであるホウ酸塩ガラス粒子を得た。粒子の形状は略球状であった。 (2) Preparation of glass borate particles 1.4% by mass of silicon dioxide (SiO 2 ), 12.5% by mass of boron oxide (B 2 O 3 ), 85.3% by mass of bismuth oxide (Bi 2 O 3 ) and A borate glass composed of 0.9% by mass of lithium oxide (Li 2 O) was obtained. The softening point of the obtained borate glass was 440 ° C. Using borate glass, borate glass particles having a volume average particle diameter of 1.1 μm were obtained. The shape of the particles was substantially spherical.
（３）電極形成用組成物の調製）
　下記の成分をロールミル（株式会社アイメックス、ＢＲ－１５０ＨＣＶ）を用いて混合し、ペースト状の電極形成用組成物を調製した。 (3) Preparation of composition for forming electrodes)
The following components were mixed using a roll mill (IMEX Co., Ltd., BR-150HCV) to prepare a paste-like electrode-forming composition.
　銀粒子（体積平均粒子径：０．６μｍ、銀含有率：９９．９質量％）：２９．４質量部
　金属ビスマス粒子（体積平均粒子径：１．５μｍ、ビスマス含有率：９９．５質量％）：２９．１質量部
　リン酸塩ガラス粒子：０．５質量部
　ホウ酸塩ガラス粒子：２．５質量部
　テルピネオール：３０．０質量部
　エチルセルロース（日新化成株式会社、ＳＴＤ－１０）：５．０質量部 Silver particles (volume average particle diameter: 0.6 μm, silver content: 99.9 mass%): 29.4 parts by mass Metal bismuth particles (volume average particle diameter: 1.5 μm, bismus content: 99.5 mass%) ): 29.1 parts by mass Phosphorate glass particles: 0.5 parts by mass Borate glass particles: 2.5 parts by mass Terpineol: 30.0 parts by mass Ethylcellulose (Nisshin Kasei Co., Ltd., STD-10): 5 .0 parts by mass
（４）太陽電池素子の作製
　受光面にｎ＋型拡散層、テクスチャ及び反射防止（ＳｉＮＸ）膜が形成され、受光面とは反対側の面（以下、「裏面」ともいう）にパッシベーション膜としての酸化アルミニウム（ＡｌＯＸ）膜及び保護膜（ＳｉＮＸ）膜がこの順に形成された厚さ１６０μｍのｐ型シリコン単結晶基板を用意し、１５８．７５ｍｍ×１５８．７５ｍｍの大きさに切り出した。次いで、裏面のパッシベーション膜／保護膜の一部について、図５Ｂに示すように、アルミニウムフィンガー電極を形成する箇所をレーザーによって除去し、シリコン基板を露出させた。受光面上に、銀粒子及び鉛ガラス粒子を含む銀電極形成用組成物（デュポン社製、ＰＶ２０）を図４に示すような電極パターンとなるように（実際には、受光面出力取出電極１４の本数を９本とした）スクリーン印刷により付与した。これを２５０℃の設定温度及び２４０インチ／分の搬送速度の条件で加熱したトンネル炉（Ｄｅｓｐａｔｃｈ社）で加熱し、溶剤を蒸散により取り除いた。 (4) Fabrication of solar cell element An n + type diffusion layer, texture and antireflection (SiN X ) film are formed on the light receiving surface, and a passivation film is formed on the surface opposite to the light receiving surface (hereinafter, also referred to as “back surface”). A 160 μm-thick p-type silicon single crystal substrate in which an aluminum oxide (AlO X ) film and a protective film (SiN X ) film were formed in this order was prepared and cut into a size of 158.75 mm × 158.75 mm. .. Next, as shown in FIG. 5B, the portion of the passivation film / protective film on the back surface where the aluminum finger electrode was formed was removed by a laser to expose the silicon substrate. A composition for forming a silver electrode (manufactured by DuPont, PV20) containing silver particles and lead glass particles is arranged on the light receiving surface so as to have an electrode pattern as shown in FIG. 4 (actually, the light receiving surface output extraction electrode 14). The number of the particles was set to 9), and the particles were given by screen printing. This was heated in a tunnel furnace (Despatch) heated under the conditions of a set temperature of 250 ° C. and a transport speed of 240 inches / minute, and the solvent was removed by evaporation.
　続いて、シリコン基板の裏面側に、アルミニウム電極形成用組成物（Ｒｕｘｉｎｇ社、ＲＸ８４０１）と、上記で得られた電極形成用組成物とを、スクリーン印刷により、図５Ｂに示すような電極パターン（実際には、アルミニウムバスバー電極２１の本数を９本とし、アルミニウムバスバー電極２１の１本あたりのアルミニウム／銀積層電極の形成箇所を６か所とした）の形状に付与した。
　具体的には、アルミニウム電極形成用組成物を、アルミニウムフィンガー電極２０及びアルミニウムバスバー電極２１の細線パターンの形状に印刷し、乾燥してアルミニウム粒子含有膜を形成した。その後、アルミニウム粒子含有膜の上に電極形成用組成物を印刷した。
　アルミニウムフィンガー電極の形成箇所は、シリコン基板が露出している部分と一致させた。アルミニウム電極形成用組成物の印刷条件は、熱処理後のアルミニウム電極の厚さが３０μｍとなるように調節した。電極形成用組成物の印刷は、１．６ｍｍ×８．０ｍｍサイズのパッド形状が配列されたパターンを用いて、８．０ｍｇ／ｃｍ２の塗布量になるように行った。
　アルミニウム電極形成用組成物及び電極形成用組成物をそれぞれ印刷した後は、２５０℃の設定温度及び２４０インチ／分の搬送速度の条件で、トンネル炉（Ｄｅｓｐａｔｃｈ社）で加熱し、溶剤を蒸散により取り除いた。 Subsequently, on the back surface side of the silicon substrate, the aluminum electrode forming composition (Ruxing, RX8401) and the electrode forming composition obtained above are subjected to screen printing to form an electrode pattern as shown in FIG. 5B. Actually, the number of aluminum bus bar electrodes 21 was set to 9, and the aluminum / silver laminated electrodes were formed at 6 positions per aluminum bus bar electrode 21).
Specifically, the composition for forming an aluminum electrode was printed in the shape of a fine line pattern of the aluminum finger electrode 20 and the aluminum bus bar electrode 21 and dried to form an aluminum particle-containing film. Then, the composition for forming an electrode was printed on the aluminum particle-containing film.
The formed portion of the aluminum finger electrode was aligned with the exposed portion of the silicon substrate. The printing conditions of the composition for forming an aluminum electrode were adjusted so that the thickness of the aluminum electrode after the heat treatment was 30 μm. The electrode-forming composition was printed using a pattern in which pad shapes having a size of 1.6 mm × 8.0 mm were arranged so that the coating amount was 8.0 mg / cm 2 .
After printing the aluminum electrode forming composition and the electrode forming composition, respectively, the mixture is heated in a tunnel furnace (Despatch) under the conditions of a set temperature of 250 ° C. and a transport speed of 240 inches / minute, and the solvent is evaporated. Removed.
　続いてトンネル炉（Ｄｅｓｐａｔｃｈ社）を用いて大気雰囲気下、最高温度８７０℃の設定温度及び２４０インチ／分の搬送速度の条件で熱処理を行って、所望の電極が形成された太陽電池素子を作製した。 Subsequently, heat treatment is performed using a tunnel furnace (Despatch) under the conditions of a set temperature of a maximum temperature of 870 ° C. and a transport speed of 240 inches / minute in an atmospheric atmosphere to produce a solar cell element on which a desired electrode is formed. did.
＜実施例２＞
　実施例１において、リン酸塩ガラス粒子の体積平均粒子径が２５．０μｍであること以外は実施例１と同様にして電極形成用組成物を調製し、太陽電池素子を作製した。 <Example 2>
In Example 1, a composition for forming an electrode was prepared in the same manner as in Example 1 except that the volume average particle diameter of the phosphate glass particles was 25.0 μm, and a solar cell element was produced.
＜実施例３＞
　実施例１において、リン酸塩ガラス粒子の体積平均粒子径が３５．０μｍであること以外は実施例１と同様にして電極形成用組成物を調製し、太陽電池素子を作製した。 <Example 3>
In Example 1, a composition for forming an electrode was prepared in the same manner as in Example 1 except that the volume average particle diameter of the phosphate glass particles was 35.0 μm, and a solar cell element was produced.
＜実施例４＞
　実施例１において、リン酸塩ガラス粒子の体積平均粒子径が１０．０μｍであること以外は実施例１と同様にして電極形成用組成物を調製し、太陽電池素子を作製した。 <Example 4>
In Example 1, a composition for forming an electrode was prepared in the same manner as in Example 1 except that the volume average particle diameter of the phosphate glass particles was 10.0 μm, and a solar cell element was produced.
＜実施例５＞
　実施例１において、リン酸塩ガラス粒子の体積平均粒子径が５０．０μｍであること以外は実施例１と同様にして電極形成用組成物を調製し、太陽電池素子を作製した。 <Example 5>
In Example 1, a composition for forming an electrode was prepared in the same manner as in Example 1 except that the volume average particle diameter of the phosphate glass particles was 50.0 μm, and a solar cell element was produced.
＜比較例１＞
　実施例１において、リン酸塩ガラス粒子の体積平均粒子径が５．０μｍであること以外は実施例１と同様にして電極形成用組成物を調製し、太陽電池素子を作製した。 <Comparative Example 1>
In Example 1, a composition for forming an electrode was prepared in the same manner as in Example 1 except that the volume average particle diameter of the phosphate glass particles was 5.0 μm, and a solar cell element was produced.
＜比較例２＞
　実施例１において、リン酸塩ガラス粒子の体積平均粒子径が６０．０μｍであること以外は実施例１と同様にして電極形成用組成物を調製し、太陽電池素子を作製した。 <Comparative Example 2>
In Example 1, a composition for forming an electrode was prepared in the same manner as in Example 1 except that the volume average particle diameter of the phosphate glass particles was 60.0 μm, and a solar cell element was produced.
＜評価＞
（１）アルミニウム／銀積層電極の断面組織観察
　作製した太陽電池素子の裏面出力取出電極の断面を、走査電子顕微鏡（日立ハイテク社製、ＳＵ５０００）を用いて、加速電圧１５ｋＶで観察した。また、装置付属のＥＤＸ分析（エネルギー分散型Ｘ線分析、Energy dispersive X-ray spectroscopy）を実施し、裏面出力取出電極としてのアルミニウム／銀積層電極の表面における銀粒子焼結部の形成、アルミニウム／銀積層電極内部の酸化ビスマス相の形成及び酸化ビスマス相の基板への到達の状態を調べた。 <Evaluation>
(1) Observation of cross-sectional structure of aluminum / silver laminated electrode The cross section of the backside output extraction electrode of the produced solar cell element was observed at an acceleration voltage of 15 kV using a scanning electron microscope (SU5000, manufactured by Hitachi High-Tech). In addition, EDX analysis (energy dispersive X-ray spectroscopy) attached to the device was performed to form a silver particle sintered portion on the surface of the aluminum / silver laminated electrode as the backside output extraction electrode, and aluminum / The state of formation of the bismuth oxide phase inside the silver laminated electrode and the arrival of the bismuth oxide phase on the substrate was investigated.
　実施例１で作製したアルミニウム／銀積層電極の断面を走査電子顕微鏡で撮影した画像像を図７に、この画像のＥＤＸ分析結果を図８にそれぞれ示す。
　断面組織観察の結果、実施例１～５及び比較例１、２で作製した太陽電池素子の裏面には、図７に示すようなアルミニウム粒子焼結部の上に銀粒子焼結部が配置された状態のアルミニウム／銀積層電極が形成されていた。ＥＤＸ分析の結果、実施例１～５及び比較例１、２のいずれにおいても、アルミニウム／銀積層電極の最表面には銀粒子焼結部が形成され、アルミニウム粒子焼結部の空隙部には酸化ビスマス相が、それぞれ形成されていた。更に、酸化ビスマス相の一部は、アルミニウム／銀積層電極が接している基板の表面に到達していた。 An image of the cross section of the aluminum / silver laminated electrode produced in Example 1 taken with a scanning electron microscope is shown in FIG. 7, and the EDX analysis result of this image is shown in FIG. 8, respectively.
As a result of observing the cross-sectional structure, a silver particle sintered portion is arranged on the aluminum particle sintered portion as shown in FIG. 7 on the back surface of the solar cell elements manufactured in Examples 1 to 5 and Comparative Examples 1 and 2. The aluminum / silver laminated electrode was formed. As a result of the EDX analysis, in both Examples 1 to 5 and Comparative Examples 1 and 2, a silver particle sintered portion was formed on the outermost surface of the aluminum / silver laminated electrode, and the void portion of the aluminum particle sintered portion was formed. The bismuth oxide phase was formed respectively. Further, a part of the bismuth oxide phase reached the surface of the substrate in contact with the aluminum / silver laminated electrode.
（２）高温高湿環境下での信頼性
　作製した太陽電池素子のうち、裏面出力取出電極に、配線材料を接続したものを用いて、高温高湿環境下での電極部の抵抗値変化を評価した。具体的には、配線材料（Ｕｌｂｒｉｃｈ社、Ｍｕｌｔｉ－Ｔａｂｂｉｎｇ　ｗｉｒｅ、Ｓｎ－Ｐｂ系共晶はんだ被覆、Ｃｕコア材の寸法は直径０．４ｍｍ）を、裏面出力取出電極上に載せ、配線材料の上からはんだごてを押し当ててはんだを溶融させることで接続した。次いで、配線材料の長さ方向に等間隔でプローブピンを押し当て、汎用ソースメータ（２４００型、ケースレー社製）を用いて、－０．５Ｖ～＋０．５Ｖの範囲の印可電圧における平均抵抗値（単位：ｍΩ）を測定し、試験前の抵抗値とした。その後、配線材料を接続した太陽電池素子を恒温恒湿槽（エスペック株式会社、ＰＳＬ－２ＫＰＨ）に入れ、１２０℃及び１００％の条件で５０時間保持した。その後、配線材料間の抵抗値を再度測定し、試験後の抵抗値とした。抵抗値の増加率を下記式により算出した。結果を表１に示す。
　増加率（％）＝｛（試験後の抵抗値－試験前の抵抗値）／試験前の抵抗値｝×１００ (2) Reliability in a high temperature and high humidity environment Among the manufactured solar cell elements, the one in which the wiring material is connected to the backside output take-out electrode is used to change the resistance value of the electrode part in the high temperature and high humidity environment. evaluated. Specifically, a wiring material (Ulbrich, Multi-Tabbing wire, Sn-Pb-based eutectic solder coating, Cu core material having a diameter of 0.4 mm) is placed on the back surface output take-out electrode and placed on the wiring material. It was connected by pressing a soldering iron from the soldering iron to melt the solder. Next, probe pins are pressed at equal intervals in the length direction of the wiring material, and using a general-purpose source meter (2400 type, manufactured by Caseley), the average resistance value in the applied voltage range of -0.5V to + 0.5V. (Unit: mΩ) was measured and used as the resistance value before the test. Then, the solar cell element to which the wiring material was connected was placed in a constant temperature and humidity chamber (Espec Co., Ltd., PSL-2KPH) and kept at 120 ° C. and 100% for 50 hours. Then, the resistance value between the wiring materials was measured again and used as the resistance value after the test. The rate of increase in resistance was calculated by the following formula. The results are shown in Table 1.
Increase rate (%) = {(resistance value after test-resistance value before test) / resistance value before test} x 100
Figure JPOXMLDOC01-appb-T000001
 
Figure JPOXMLDOC01-appb-T000001
 
　表１に示すように、リン含有ガラス粒子の体積平均粒子径が１０．０μｍ～５０．０μｍの範囲内である実施例１～５は、リン含有ガラス粒子の体積平均粒子径が１０．０μｍ～５０．０μｍ以下の範囲外である比較例１、２に比べて高温高湿環境下での抵抗値の増加率が小さく、優れた信頼性を示した。 As shown in Table 1, in Examples 1 to 5 in which the volume average particle diameter of the phosphorus-containing glass particles is in the range of 10.0 μm to 50.0 μm, the volume average particle diameter of the phosphorus-containing glass particles is 10.0 μm or more. Compared with Comparative Examples 1 and 2 which are outside the range of 50.0 μm or less, the rate of increase in the resistance value in a high temperature and high humidity environment was small, and excellent reliability was shown.
　日本国特許出願第２０２０－２１１６１０号の開示は、その全体が参照により本明細書に取り込まれる。
　本明細書に記載された全ての文献、特許出願、および技術規格は、個々の文献、特許出願、および技術規格が参照により取り込まれることが具体的かつ個々に記された場合と同程度に、本明細書中に援用されて取り込まれる。 The disclosure of Japanese Patent Application No. 2020-21610 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards described herein are to the same extent as if the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference. Incorporated and incorporated herein.

Claims (13)

  1. 　銀含有粒子と、ビスマス含有粒子と、ガラス粒子とを含み、前記ガラス粒子はリンを含有するガラス粒子を含み、前記リンを含有するガラス粒子の体積平均粒子径が１０．０μｍ～５０．０μｍである、電極形成用組成物。 The glass particles include silver-containing particles, bismuth-containing particles, and glass particles, and the glass particles contain phosphorus-containing glass particles, and the volume average particle diameter of the phosphorus-containing glass particles is 10.0 μm to 50.0 μm. A composition for forming electrodes.
  2. 　前記ガラス粒子はホウ素を含有するガラス粒子を更に含む、請求項１に記載の電極形成用組成物。 The electrode-forming composition according to claim 1, wherein the glass particles further contain glass particles containing boron.
  3. 　前記リンを含有するガラス粒子において、酸化リンの含有率が全体の２０．０質量％以上である、請求項１又は請求項２に記載の電極形成用組成物。 The electrode-forming composition according to claim 1 or 2, wherein the phosphorus-containing glass particles have a phosphorus oxide content of 20.0% by mass or more as a whole.
  4. 　前記ホウ素を含有するガラス粒子において、酸化ホウ素の含有率が全体の３．０質量％以上である、請求項２に記載の電極形成用組成物。 The electrode-forming composition according to claim 2, wherein the boron oxide-containing glass particles have a boron oxide content of 3.0% by mass or more as a whole.
  5. 　前記ホウ素を含有するガラス粒子が酸化ビスマスを含む、請求項２又は請求項４に記載の電極形成用組成物。 The electrode-forming composition according to claim 2 or 4, wherein the boron-containing glass particles contain bismuth oxide.
  6. 　前記ビスマス含有粒子が金属ビスマス、ビスマス合金及び酸化ビスマスからなる群より選択される少なくとも１種を含む、請求項１～請求項５のいずれか１項に記載の電極形成用組成物。 The electrode-forming composition according to any one of claims 1 to 5, wherein the bismuth-containing particles contain at least one selected from the group consisting of metal bismuth, bismuth alloy, and bismuth oxide.
  7. 　前記銀含有粒子の含有量に対する前記ビスマス含有粒子の含有量の質量比（Ｂｉ／Ａｇ比）が０．３０～１．４０である、請求項１～請求項６のいずれか１項に記載の電極形成用組成物。 The invention according to any one of claims 1 to 6, wherein the mass ratio (Bi / Ag ratio) of the content of the bismuth-containing particles to the content of the silver-containing particles is 0.30 to 1.40. Composition for forming electrodes.
  8. 　前記ガラス粒子の含有量に対する前記ビスマス含有粒子の含有量の質量比（Ｂｉ／Ｇ比）が０．５～１５．０である、請求項１～請求項７のいずれか１項に記載の電極形成用組成物。 The electrode according to any one of claims 1 to 7, wherein the mass ratio (Bi / G ratio) of the content of the bismuth-containing particles to the content of the glass particles is 0.5 to 15.0. Formation composition.
  9. 　前記ガラス粒子の含有率が前記電極形成用組成物全体の１．０質量％～１５．０質量％である、請求項１～請求項８のいずれか１項に記載の電極形成用組成物。 The electrode-forming composition according to any one of claims 1 to 8, wherein the content of the glass particles is 1.0% by mass to 15.0% by mass of the entire electrode-forming composition.
  10. 　溶剤及び樹脂からなる群より選択される少なくとも１つを含む、請求項１～請求項９のいずれか１項に記載の電極形成用組成物。 The electrode-forming composition according to any one of claims 1 to 9, which comprises at least one selected from the group consisting of a solvent and a resin.
  11. 　アルミニウム電極の上に銀電極を形成するための、請求項１～請求項１０のいずれか１項に記載の電極形成用組成物。 The electrode forming composition according to any one of claims 1 to 10, for forming a silver electrode on an aluminum electrode.
  12. 　半導体基板と、前記半導体基板上に設けられるパッシベーション膜と、前記パッシベーション膜上に設けられる請求項１～請求項１１のいずれか１項に記載の電極形成用組成物の熱処理物を含むアルミニウム／銀積層電極と、を有する太陽電池素子。 Aluminum / silver containing a semiconductor substrate, a passivation film provided on the semiconductor substrate, and a heat-treated product of the electrode forming composition provided on the passivation film according to any one of claims 1 to 11. A solar cell element having a laminated electrode.
  13. 　請求項１～請求項１１のいずれか１項に記載の電極形成用組成物の熱処理物を含み、かつ、アルミニウムを含む第１電極と、前記第１電極の上に配置される銀を含む第２電極とを備え、前記第１電極は酸化ビスマス相及びリンを含有するガラス相を更に含む、アルミニウム／銀積層電極。 A first electrode containing the heat-treated electrode-forming composition according to any one of claims 1 to 11 and containing aluminum, and a silver containing silver arranged on the first electrode. An aluminum / silver laminated electrode comprising two electrodes, the first electrode further comprising a bismuth oxide phase and a phosphorus-containing glass phase.
PCT/JP2021/046334 2020-12-21 2021-12-15 Composition for forming electrode, solar cell element, and aluminum/silver stacked electrode WO2022138385A1 (en)

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