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WO2007004281A1 - Composition de pâte et élément de cellule solaire utilisant celle-ci - Google Patents

Composition de pâte et élément de cellule solaire utilisant celle-ci Download PDF

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Publication number
WO2007004281A1
WO2007004281A1 PCT/JP2005/012301 JP2005012301W WO2007004281A1 WO 2007004281 A1 WO2007004281 A1 WO 2007004281A1 JP 2005012301 W JP2005012301 W JP 2005012301W WO 2007004281 A1 WO2007004281 A1 WO 2007004281A1
Authority
WO
WIPO (PCT)
Prior art keywords
aluminum
paste composition
paste
semiconductor substrate
powder
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2005/012301
Other languages
English (en)
Japanese (ja)
Inventor
Takashi Watsuji
Jun Nakahara
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toyo Aluminum KK
Original Assignee
Toyo Aluminum KK
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toyo Aluminum KK filed Critical Toyo Aluminum KK
Priority to PCT/JP2005/012301 priority Critical patent/WO2007004281A1/fr
Publication of WO2007004281A1 publication Critical patent/WO2007004281A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/20—Electrodes
    • H10F77/206—Electrodes for devices having potential barriers
    • H10F77/211—Electrodes for devices having potential barriers for photovoltaic cells
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F10/00—Individual photovoltaic cells, e.g. solar cells
    • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
    • H10F10/14—Photovoltaic cells having only PN homojunction potential barriers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/547—Monocrystalline silicon PV cells

Definitions

  • the present invention generally relates to a paste composition and a solar cell element using the same.
  • the present invention relates to a paste composition used for forming a back surface aluminum electrode on a p-type silicon semiconductor substrate constituting a crystalline silicon solar cell, and a solar cell element using the paste composition.
  • Solar cells are desired to be used in a wider range as clean energy that is safe and has a low environmental impact.
  • it is necessary to promote light weight and low cost in order to popularize solar cells that use silicon semiconductor substrates to form elements.
  • research and development have been repeated in order to reduce the thickness of solar cell elements.
  • FIG. 1 is a diagram schematically showing a general cross-sectional structure of a solar cell element.
  • an n-type impurity layer 2 having a thickness of 0.3 to 0.5 m is provided on the light-receiving surface side of a ⁇ -type silicon semiconductor substrate 1 having a thickness of 00 to 600 ⁇ m.
  • a film 3 and a grid electrode 4 are formed in this order.
  • an aluminum electrode layer 8 is formed as a back electrode.
  • the aluminum electrode layer 8 includes an aluminum sintered layer 5 and an aluminum silicon mixed layer 6.
  • an aluminum sintered layer 5 and an aluminum silicon mixed layer 6 are formed, and at the same time, aluminum is contained in the p-type silicon semiconductor substrate 1.
  • the presence of the p + layer 7 provides a so-called BSF (Back Surface Field) effect, and can improve the collection efficiency of carriers generated in the p-type semiconductor substrate 1.
  • the aluminum electrode layer is formed to be thicker than necessary. Therefore, if the thickness of the silicon semiconductor substrate is reduced to 300 m or less in order to reduce the thickness of the solar cell element, the ratio of the thickness of the aluminum electrode layer to the thickness of the semiconductor substrate increases. As a result, when cooling from the firing temperature for forming the aluminum electrode layer to room temperature, internal stress is generated due to the difference in thermal expansion coefficient between the aluminum or aluminum silicon mixture and silicon. There has been a problem that the semiconductor substrate is warped or cracked.
  • the conventional method for manufacturing a solar cell element has a problem when the thickness of the silicon semiconductor substrate is reduced to 300 ⁇ m or less in response to a request for thinning the solar cell element.
  • Patent Document 1 A method of etching a part of the surface of the back electrode in the thickness direction after forming the back electrode on the semiconductor substrate has been proposed in, for example, Japanese Unexamined Patent Application Publication No. 2002-353476 (Patent Document 1).
  • Patent Document 1 Japanese Unexamined Patent Application Publication No. 2002-353476
  • this method has a problem in that the manufacturing process is complicated and warpage or cracking during firing cannot be prevented.
  • two or more types of aluminum-containing paste are applied to the entire back surface of the semiconductor substrate by first thinly applying it and then applying the aluminum-containing paste again to the portion to be thickened, followed by firing.
  • Japanese Patent Laid-Open No. 2002-217435 proposes a method of forming a back electrode with a thickness of 10 mm.
  • Patent Document 3 proposes a method of forming backside electrodes in a lattice pattern on the backside of a semiconductor substrate.
  • a method of forming a back electrode on the back surface of a semiconductor substrate in a strip shape having a different thickness is proposed, for example, in Japanese Patent Laid-Open No. 2002-141534 (Patent Document 4). It has been proposed.
  • a method of forming a back electrode in a rectangular shape on the back surface of a semiconductor substrate is, for example,
  • Patent Document 5 JP-A-2002-141546 (Patent Document 5).
  • the p + layer that produces the BSF effect formed by any of these methods becomes non-uniform, resulting in a decrease in conversion efficiency.
  • composition of a conductive paste capable of thinning the aluminum electrode layer while ensuring a desired BSF effect a composition containing aluminum powder, glass frit, an organic vehicle, and an aluminum-containing organic compound. JP 2000-90734 (Patent Document 6).
  • Patent Document 6 JP 2000-90734
  • the back electrode layer is thinned by reducing the coating amount while ensuring certain solar cell characteristics, and the amount of warpage generated in the p-type silicon semiconductor substrate is reduced.
  • the amount of warpage cannot be reduced without reducing the amount of conductive paste applied in order to obtain a sufficient BSF effect.
  • the coefficient of thermal expansion is smaller than that of aluminum, and the melting temperature, softening temperature and decomposition temperature are higher than the melting point of aluminum, and include an inorganic compound, aluminum powder, and organic vehicle.
  • Paste composition strength For example, it has been proposed in JP 2003-223813 A (Patent Document 7). However, when the amount of the inorganic compound added is increased, the occurrence of warpage or cracking during firing can be further suppressed, but the surface resistance of the aluminum electrode layer is increased and the ohmic resistance between the electrodes is increased. There was a problem that the energy generated by the irradiation of the material could not be extracted effectively, leading to a decrease in energy conversion efficiency.
  • Patent Document 1 Japanese Patent Laid-Open No. 2002-353476
  • Patent Document 2 JP 2002-217435 A
  • Patent Document 3 Japanese Patent Laid-Open No. 2002-141533
  • Patent Document 4 Japanese Patent Laid-Open No. 2002-141534
  • Patent Document 5 JP 2002-141546 A
  • Patent Document 6 Japanese Unexamined Patent Publication No. 2000-90734
  • Patent Document 7 Japanese Patent Laid-Open No. 2003-223813
  • an object of the present invention is to solve the above-mentioned problem, and even if a thinner silicon semiconductor substrate is used, warpage or cracking can be prevented, and high, A paste composition capable of achieving a BSF effect, high energy conversion efficiency, and a solar cell element including an electrode formed using the composition.
  • the paste composition according to the present invention has the following characteristics.
  • a paste composition according to the present invention is a paste composition for forming an electrode on a p-type silicon semiconductor substrate, and includes an aluminum powder, an organic vehicle, and a carbon powder.
  • the paste composition of the present invention further includes glass frit.
  • the paste composition of the present invention includes 0.1% by mass or more and 18% by mass or less of carbon powder.
  • the aluminum powder is 60% by mass or more and 75% by mass or less
  • the organic vehicle is 20% by mass or more and 35% by mass or less
  • the carbon powder is 0.1% by mass or more 18% by mass. Including mass% or less.
  • the paste composition of the present invention contains aluminum powder in an amount of 60% by mass to 75% by mass, an organic vehicle in an amount of 20% by mass to 30% by mass, and a carbon powder of 0. 1% to 18% by mass and glass frit to 5.0% by mass or less.
  • the carbon powder is preferably carbon black.
  • the average particle size of the carbon powder is preferably 10 ⁇ m or less.
  • the average particle size of the carbon powder is 0.5. It is preferable that it is below ⁇ m.
  • the carbon powder when the average particle size of the carbon powder is 0.5 ⁇ m or less, the carbon powder is preferably contained in an amount of 0.3 mass% to 6 mass%.
  • a solar cell element according to the present invention includes an electrode formed by applying a paste thread and composition having the above-described characteristics onto a p-type silicon semiconductor substrate and then firing it.
  • a solar cell element according to another aspect of the present invention includes an aluminum electrode layer, and the aluminum electrode layer includes carbon particles.
  • a solar cell element having an electrode formed using the composition can achieve a high BSF effect and a high energy conversion efficiency.
  • FIG. 1 is a diagram schematically showing a general cross-sectional structure of a solar cell element to which the present invention is applied as one embodiment.
  • FIG. 2 is a diagram schematically showing a method of measuring a warpage amount of a p-type silicon semiconductor substrate after firing in which an aluminum electrode layer is formed in Examples and Conventional Examples.
  • l p-type silicon semiconductor substrate
  • 2 n-type impurity layer
  • 3 antireflection film
  • 4 grid electrode
  • 5 aluminum sintered layer
  • 6 aluminum silicon mixed layer
  • 7 p + layer
  • 8 Aluminum electrode layer
  • the paste composition of the present invention is characterized by further containing carbon powder in addition to the aluminum powder and the organic vehicle.
  • the thermal expansion coefficient of carbon powder varies depending on the crystal structure and the like, but is approximately 0.5 to: LO X 10 _6 / ° C, which is smaller than the aluminum thermal expansion coefficient 23.5 X 10 _6 Z ° C.
  • the electrical conductivity of the carbon powder is determined by the inorganic compound powder or the key. Larger than lumium-containing organic compound powder.
  • the surface resistance of the aluminum electrode layer does not increase, there is no possibility of causing a decrease in energy conversion efficiency. Further, since the deformation of the p-type silicon semiconductor substrate after baking can be suppressed without reducing the paste coating thickness, a sufficient BSF effect can be obtained.
  • any material such as artificial graphite powder, activated carbon or carbon black, carbon fiber, glassy carbon and the like can be suitably used. .
  • the content of the carbon powder included in the paste yarn according to the present invention is preferably 0.1% by mass or more and 18% by mass. If the content of the carbon powder is less than 0.1% by mass, it is not possible to obtain a sufficient addition effect to suppress deformation of the p-type silicon semiconductor substrate after firing. If the content of the carbon powder exceeds 18 mass 0/0, the application of the paste in screen printing or the like is reduced. [0038]
  • the average particle size of the carbon powder included in the paste composition of the present invention is preferably 10 ⁇ m or less, more preferably 1 ⁇ m or less, and even more preferably 0.5 m or less. If the average particle size of the carbon powder exceeds 10 m, the number of carbon particles present in the aluminum electrode layer formed when the paste is baked is reduced, so that deformation of the p-type silicon semiconductor substrate after baking is suppressed. The sufficient addition effect cannot be obtained.
  • the average particle size of the carbon powder is not more than 0.3 and the content of the carbon powder is 0.3 mass. % To 6% by mass. By doing so, fine carbon powder is effectively dispersed and contained in the aluminum electrode layer.
  • the lower limit of the average particle size of the carbon powder is not particularly limited, but when the specific surface area that increases with the decrease in the average particle size exceeds 20000 m 2 / g, the viscosity of the paste increases, and the paste does not have a good effect during screen printing. The applicability decreases.
  • the content of the aluminum powder included in the paste composition of the present invention is preferably 60% by mass or more and 75% by mass or less. If the content of aluminum powder is less than 60% by mass, the surface resistance of the aluminum electrode layer after firing increases, which may lead to a decrease in energy conversion efficiency. If the aluminum powder content exceeds 75% by mass, the applicability of the paste during screen printing will decrease.
  • the organic vehicle included in the paste composition of the present invention one obtained by dissolving ethyl cellulose, acrylic resin, alkyd resin, etc. in a solvent is used.
  • the content of the organic vehicle is preferably 20% by mass or more and 35% by mass or less. When the content of the organic vehicle is less than 20% by mass or exceeds 35% by mass, the printability of the paste decreases.
  • the paste composition of the present invention may contain glass frit.
  • the glass frit content is preferably 5.0% by mass or less. Glass frit is not directly related to the deformation, BSF effect and energy conversion efficiency of p-type silicon semiconductor, but is added to improve the adhesion between the sintered aluminum electrode layer and p-type silicon semiconductor substrate. It is a thing. If the content of glass frit exceeds 5.0% by mass, there is a risk of glass praying.
  • Examples of the glass frit included in the paste composition of the present invention include SiO-BiO-PbO.
  • B O -SiO- Bi O system B O-SiO- ZnO system
  • Examples include the 2 3 2 2 3 2 3 2 2 3 2 system.
  • a solar cell element according to one embodiment of the present invention has a cross-sectional structure shown in FIG. 1, and aluminum as a back electrode formed on the back side of p-type silicon semiconductor substrate 1-
  • the volume electrode layer 8 contains carbon particles.
  • an organic vehicle in which ethyl cellulose is dissolved in a glycol ether organic solvent is coated with aluminum powder and a B 2 O—SiO—PbO glass frit.
  • the aluminum powder has a spherical shape with an average particle diameter of 2 to 20 / ⁇ ⁇ , or a spherical shape from the viewpoint of ensuring reactivity with the p-type silicon semiconductor substrate, coating properties, and uniformity of the coating film.
  • a powder composed of particles having a close shape was used.
  • the p-type silicon semiconductor substrate on which the paste has been printed After drying the p-type silicon semiconductor substrate on which the paste has been printed, it is heated in an infrared firing furnace at a temperature increase rate of 400 ° CZ in an air atmosphere and maintained at a temperature of 710 to 720 ° C for 30 seconds. Firing was carried out under the conditions. After firing, cooling was performed to obtain each sample in which an aluminum electrode layer 8 serving as a back electrode was formed on a p-type silicon semiconductor substrate 1 as shown in FIG.
  • the amount of warpage of the p-type silicon semiconductor substrate after the baking with the aluminum electrode layer formed is indicated by arrows at one end of the four corners of the substrate with the aluminum electrode layer facing upward as shown in FIG. Evaluation was performed by measuring the amount of lifting (including the thickness of the substrate) X of one end located at the opposite corner while holding the substrate as shown. The amount of lift X is shown in “Warpage (mm)” in Table 2.
  • the surface resistance of the aluminum electrode layer was measured with a 4-terminal surface resistance measuring device (RG-5 type sheet resistance measuring device manufactured by Nabson).
  • the measurement conditions were a voltage of 4 mV, a current of 100 mA, and a load applied to the surface of 200 grf (l. 96N).
  • the measured values are shown in the electrode layer surface resistance ( ⁇ inlet) in Table 1.
  • the ⁇ -type silicon semiconductor substrate on which the aluminum electrode layer is formed is immersed in an aqueous hydrochloric acid solution to dissolve and remove the aluminum electrode layer 8, and then the ⁇ -type silicon on which the ⁇ + layer 7 is formed.
  • the surface resistance of the semiconductor substrate 1 was measured with a 4-terminal surface resistance measuring instrument. The measured values are shown in Table 1 as ⁇ + layer surface resistance ( ⁇ port).
  • the example can maintain the p-layer surface resistance ( ⁇ port), while keeping the amount of warpage low, and the electrode layer surface resistance ( ⁇ / port) is also small. Power that can be done.
  • the paste composition of the present invention can prevent warping or cracking of the p-type silicon semiconductor substrate even when applied on the p-type silicon semiconductor substrate and baked, and the composition In a solar cell element with electrodes formed using, high BSF effect, high V, and energy conversion efficiency can be achieved.

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  • Photovoltaic Devices (AREA)

Abstract

L'invention concerne une composition de pâte qui peut prévenir la génération d'un gauchissement ou d'une cassure même lorsqu'un substrat semi-conducteur de silicium plus mince est utilisé, et qui peut obtenir des effets BSF élevés et un haut rendement de conversion d'énergie, ainsi qu'un élément de cellule solaire muni d'une électrode formée en utilisant une telle composition. La composition de pâte est utilisée pour former une couche d'électrode d'aluminium (8) sur un substrat semi-conducteur de silicium de type p (1) et elle inclut une poudre d'aluminium, un liant organique et une poudre de carbone. L'élément de cellule solaire est muni de la couche d'électrode d'aluminium (8) qui est formée en appliquant la composition de pâte présentant les caractéristiques mentionnées ci-dessus sur le substrat semi-conducteur de silicium de type p (1) puis en surchauffant la pâte. La couche d'électrode d'aluminium (8) inclut des particules de carbone.
PCT/JP2005/012301 2005-07-04 2005-07-04 Composition de pâte et élément de cellule solaire utilisant celle-ci Ceased WO2007004281A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/JP2005/012301 WO2007004281A1 (fr) 2005-07-04 2005-07-04 Composition de pâte et élément de cellule solaire utilisant celle-ci

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP2005/012301 WO2007004281A1 (fr) 2005-07-04 2005-07-04 Composition de pâte et élément de cellule solaire utilisant celle-ci

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WO2007004281A1 true WO2007004281A1 (fr) 2007-01-11

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004134775A (ja) * 2002-09-19 2004-04-30 Murata Mfg Co Ltd 導電性ペースト
JP2004303463A (ja) * 2003-03-28 2004-10-28 Sharp Corp 色素増感型太陽電池モジュール及びその製造方法
JP2005079031A (ja) * 2003-09-02 2005-03-24 Toin Gakuen 光充電可能な二次電池及び電気化学キャパシタ

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004134775A (ja) * 2002-09-19 2004-04-30 Murata Mfg Co Ltd 導電性ペースト
JP2004303463A (ja) * 2003-03-28 2004-10-28 Sharp Corp 色素増感型太陽電池モジュール及びその製造方法
JP2005079031A (ja) * 2003-09-02 2005-03-24 Toin Gakuen 光充電可能な二次電池及び電気化学キャパシタ

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