JP2012234989A - N-type diffusion layer formation composition, manufacturing method for the same, and manufacturing method for solar battery element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an n-type diffusion layer formation composition, a manufacturing method for the same, and a manufacturing method for a solar battery element, that can form an n-type diffusion layer in a particular portion without forming an unnecessary n-type diffusion layer in a manufacturing process for a solar battery element using a silicon substrate, and provide an n-type diffusion layer formation composition, a manufacturing method for the same, and a manufacturing method for a solar battery element, that can perform washing before thermal diffusion processing by performing preliminary heating after coating the silicon substrate with the n-type diffusion layer formation composition to solidify the coated surface in the manufacturing process for the solar battery element using the silicon substrate.SOLUTION: An n-type diffusion layer formation composition comprises: glass powder containing a donor element; and a curable resin. An n-type diffusion layer and a solar battery element including the n-type diffusion layer are manufactured by applying this n-type diffusion layer formation composition and performing thermal diffusion processing.

Description

  The present invention relates to a composition for forming an n-type diffusion layer of a solar cell element, a method for producing an n-type diffusion layer, and a method for producing a solar cell element. More specifically, the present invention relates to a specific portion of silicon as a semiconductor substrate. The present invention relates to a technique capable of forming an n-type diffusion layer.

The manufacturing process of the conventional silicon solar cell element is demonstrated.
First, a p-type silicon substrate having a textured structure formed on the light receiving surface is prepared so as to promote the light confinement effect, and then a donor element-containing compound such as phosphorus oxychloride (POCl ₃ ), nitrogen, oxygen The n-type diffusion layer is uniformly formed by performing several tens of minutes at 800 to 900 ° C. in the mixed gas atmosphere. In this conventional method, since phosphorus is diffused using a mixed gas, n-type diffusion layers are formed not only on the surface but also on the side surface and the back surface. Therefore, a side etching process for removing the side n-type diffusion layer is necessary. Further, the n-type diffusion layer on the back surface needs to be converted into a p ⁺ -type diffusion layer. An aluminum paste is applied on the n-type diffusion layer on the back surface, and the p ⁺ -type diffusion is performed from the n-type diffusion layer by the diffusion of aluminum. Was converted into a layer.

On the other hand, in the semiconductor manufacturing field, by applying a solution containing a phosphate such as phosphorus pentoxide (P ₂ O ₅ ) or ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) as a donor element-containing compound. A method for forming an n-type diffusion layer has been proposed (see, for example, Patent Document 1). In addition, for forming a diffusion layer, a technique is also known in which a paste containing phosphorus as a donor element is applied on a silicon substrate surface as a diffusion source and thermally diffused to form a diffusion layer (see, for example, Patent Document 2). ). However, in these methods, since the donor element or a compound containing the same is scattered from the solution or paste as the diffusion source, the diffusion of phosphorus is caused by the side surface and the diffusion during the formation of the diffusion layer as in the gas phase reaction method using the mixed gas. An n-type diffusion layer is also formed on the back surface and in addition to the applied portion.

JP 2002-75894 A Japanese Patent No. 4073968

  As described above, in forming a n-type diffusion layer, in the gas phase reaction using phosphorus oxychloride, not only one side (usually the light receiving surface or the surface) that originally requires the n-type diffusion layer but also the other side An n-type diffusion layer is also formed on the surface (non-light-receiving surface or back surface) and side surfaces. In addition, even in a method in which a solution containing a compound containing phosphorus or a paste is applied and thermally diffused, an n-type diffusion layer is formed in addition to the surface as in the gas phase reaction method. Therefore, in order to have a pn junction structure as an element, it is necessary to perform etching on the side surface and convert the n-type diffusion layer to the p-type diffusion layer on the back surface. In general, an aluminum paste which is a Group 13 element is applied to the back surface and fired to convert the n-type diffusion layer into a p-type diffusion layer. Further, in the conventionally known method of applying a paste containing a donor element such as phosphorus as a diffusion source, the compound having the donor element is volatilized and gas is diffused and diffused in a region other than the region where diffusion is required. In particular, it is difficult to form a diffusion layer in a specific region.

  The present invention has been made in view of the above-described conventional problems, and an n-type diffusion layer is formed in a specific portion without forming an unnecessary n-type diffusion layer in a manufacturing process of a solar cell element using a silicon substrate. It is an object of the present invention to provide an n-type diffusion layer forming composition, a method for manufacturing an n-type diffusion layer, and a method for manufacturing a solar cell element.

Means for solving the problems are as follows.
<1> An n-type diffusion layer forming composition containing glass powder containing a donor element and a curable resin.
<2> The n-type diffusion layer forming composition according to <1>, further comprising a thermosetting agent or a photocuring agent.
<3> The n-type diffusion layer forming composition according to <1> or <2>, wherein the donor element is at least one selected from P (phosphorus) and Sb (antimony).
<4> The glass powder containing the donor element includes at least one donor element-containing material selected from P ₂ O ₃ , P ₂ O ₅ and Sb ₂ O ₃ , and SiO ₂ , K ₂ O, and Na ₂ O. And at least one glass component material selected from Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ and MoO ₃ , The n-type diffusion layer forming composition according to any one of <1> to <3>.

<5> A step of applying the n-type diffusion layer forming composition according to any one of <1> to <4> on a semiconductor substrate, a step of curing the curable resin, and a step of applying a thermal diffusion treatment And a method for manufacturing an n-type diffusion layer.
<6> A step of applying the n-type diffusion layer forming composition according to any one of <1> to <4>, a step of curing the curable resin, and a thermal diffusion treatment on a semiconductor substrate. A method for manufacturing a solar cell element, comprising: forming an n-type diffusion layer; and forming an electrode on the formed n-type diffusion layer.

  According to the present invention, an n-type diffusion layer can be formed in a specific region without forming an n-type diffusion layer in an unnecessary region in a manufacturing process of a solar cell element using a silicon substrate.

It is sectional drawing which shows notionally an example of the manufacturing process of the solar cell element of this invention. (A) is the top view which looked at the solar cell element from the surface, (B) is the perspective view which expands and shows a part of (A).

First, the n-type diffusion layer forming composition of the present invention will be described, and then the n-type diffusion layer and solar cell element manufacturing method using the n-type diffusion layer forming composition will be described.
In this specification, the term “process” is not limited to an independent process, and even if it cannot be clearly distinguished from other processes, the term “process” is used if the intended action of the process is achieved. included. In the present specification, “to” indicates a range including the numerical values described before and after the values as a minimum value and a maximum value, respectively.

The n-type diffusion layer forming composition of the present invention contains a glass powder containing at least a donor element (hereinafter sometimes simply referred to as “glass powder”) and a curable resin, and further considers applicability and the like. In addition, other additives may be contained as necessary.
Here, the n-type diffusion layer forming composition contains a glass powder containing a donor element, and is a material capable of forming an n-type diffusion layer by thermally diffusing this donor element after being applied to a silicon substrate. Say. By using an n-type diffusion layer forming composition containing a donor element in glass powder, an n-type diffusion layer is formed at a desired site, and an unnecessary n-type diffusion layer is not formed on the back surface or side surface.

Therefore, if the composition for forming an n-type diffusion layer of the present invention is applied, the side etching step that is essential in the gas phase reaction method that has been widely employed is not required, and the process is simplified. In addition, the step of converting the n-type diffusion layer formed on the back surface into the p ⁺ -type diffusion layer is not necessary. Therefore, the method for forming the p ⁺ -type diffusion layer on the back surface and the material, shape, and thickness of the back electrode are not limited, and the choice of manufacturing method, material, and shape to be applied is widened. Although details will be described later, generation of internal stress in the silicon substrate due to the thickness of the back electrode is suppressed, and warpage of the silicon substrate is also suppressed.

  In addition, the glass powder contained in the n type diffused layer formation composition of this invention fuse | melts by baking, and forms a glass layer on an n type diffused layer. However, a glass layer is formed on the n-type diffusion layer even in a conventional gas phase reaction method or a method of applying a phosphate-containing solution or paste, and thus the glass layer produced in the present invention is a conventional method. Similarly to the above, it can be removed by etching. Therefore, the n-type diffusion layer forming composition of the present invention does not generate unnecessary products and does not increase the number of steps as compared with the conventional method.

In addition, since the donor component in the glass powder is difficult to volatilize even during firing, it is suppressed that the n-type diffusion layer is formed not only on the surface but also on the back surface and side surfaces due to the generation of the volatilizing gas.
The reason for this is considered that the donor component is bonded to an element in the glass powder or is taken into the glass, so that it is difficult to volatilize.

  Thus, since the n-type diffusion layer forming composition of the present invention can form an n-type diffusion layer having a desired concentration at a desired site, a selective region having a high n-type dopant concentration is formed. It becomes possible to form. On the other hand, it is generally difficult to form a selective region having a high n-type dopant concentration by a gas phase reaction method, which is a general method of an n-type diffusion layer, or a method using a phosphate-containing solution. .

  Further, by including the curable resin, it is possible to form the n-type diffusion layer in a desired shape regardless of the post-process after the application of the n-type diffusion layer composition.

The glass powder containing the donor element according to the present invention will be described in detail.
A donor element is an element that can form an n-type diffusion layer by doping into a silicon substrate. As the donor element, a Group 15 element can be used, and examples thereof include P (phosphorus), Sb (antimony), Bi (bismuth), As (arsenic), and the like. From the viewpoints of safety, ease of vitrification, etc., P or Sb is preferred.

Examples of the donor element-containing material used for introducing the donor element into the glass powder include P ₂ O ₃ , P ₂ O ₅ , Sb ₂ O ₃ , Bi ₂ O ₃ and As ₂ O ₃ , and P ₂ O ₃ It is preferable to use at least one selected from P ₂ O ₅ and Sb ₂ O ₃ .

Moreover, the glass powder containing a donor element can control a melting temperature, a softening point, a glass transition point, chemical durability, etc. by adjusting a component ratio as needed. Furthermore, it is preferable to contain the glass component substance described below.
Examples of glass component materials include SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ , WO ₃ , Examples include MoO ₃ , MnO, La ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Y ₂ O ₃ , TiO ₂ , ZrO ₂ , GeO ₂ , TeO _2, and Lu ₂ O _3. SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ , WO ₃ , MoO ₃ and MnO it is preferable to use the _{seeds, SiO 2, K 2 O,} Na 2 O, Li 2 O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V 2 O 5, SnO More preferably, at least one selected from ZrO ₂ and MoO ₃ is used.

Specific examples of the glass powder containing a donor element include a system containing both the donor element-containing material and the glass component material, and a P ₂ O ₅ -SiO ₂ system (in order of donor element-containing material-glass component material). in described, the same applies _{hereinafter), P 2 O 5 -K 2} O _based, P ₂ O 5 -Na _{2 O-based,} P ₂ O 5 -Li ₂ O _system, P ₂ O 5 _-BaO-based, P 2 _{O 5} - _SrO-based, P ₂ O 5 _-CaO-based, P ₂ O 5 _-MgO-based, P ₂ O 5 -BeO _based, P ₂ O 5 _-ZnO-based, P ₂ O 5 -CdO _based, P ₂ O 5 -PbO system , including _P 2 _O 5 _-V 2 _{O 5 system,} P ₂ O 5 _-SnO-based, P ₂ O 5 -GeO _{2 system,} a _P 2 _{O 5} as a donor element-containing material of P ₂ O 5 -TeO ₂ system, etc. Instead of P ₂ O ₅ in a system containing P ₂ O ₅ , a donor element-containing material is used. And glass powder of a system containing Sb ₂ O ₃ .
Note that a glass powder containing two or more kinds of donor element-containing substances, such as a P ₂ O ₅ —Sb ₂ O ₃ system and a P ₂ O ₅ —As ₂ O ₃ system, may be used.
Although the composite glass containing two components was illustrated above, glass powder containing three or more components such as P ₂ O ₅ —SiO ₂ —V ₂ O ₅ and P ₂ O ₅ —SiO ₂ —CaO may be used.

  The content ratio of the glass component substance in the glass powder is preferably set as appropriate in consideration of the melting temperature, the softening point, the glass transition point, and the chemical durability, and is generally 0.1% by mass to 95% by mass. It is preferable that it is 0.5 mass% or more and 90 mass% or less.

Specifically, for example, as glass component materials, SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO ₂ , and MoO _The glass containing at least one selected from ₃ is preferable because the reaction product with the silicon substrate does not remain as a residue during the hydrofluoric acid treatment. Moreover, in the case of glass containing vanadium oxide V ₂ O ₅ as a glass component substance (for example, P ₂ O ₅ —V ₂ O ₅ glass), V ₂ O ₅ is used from the viewpoint of lowering the melting temperature and the softening point. The content ratio is preferably 1% by mass or more and 50% by mass or less, and more preferably 3% by mass or more and 40% by mass or less.

  The softening point of the glass powder is preferably 200 ° C. to 1000 ° C., more preferably 300 ° C. to 900 ° C., from the viewpoints of diffusibility during the diffusion treatment and dripping.

Examples of the shape of the glass powder include a substantially spherical shape, a flat shape, a block shape, a plate shape, a scale shape, and the like. From the viewpoint of the application property to the substrate and the uniform diffusibility when it is an n-type diffusion layer forming composition, It is desirable to have a substantially spherical shape, a flat shape, or a plate shape. The particle size of the glass powder is desirably 100 μm or less. When glass powder having a particle size of 100 μm or less is used, a smooth coating film is easily obtained. Furthermore, the particle size of the glass powder is more desirably 50 μm or less. The lower limit is not particularly limited, but is preferably 0.01 μm or more.
Here, the particle diameter of glass represents an average particle diameter, and can be measured by a laser scattering diffraction particle size distribution measuring apparatus or the like.

The glass powder containing a donor element is produced by the following procedure.
First, raw materials, for example, the donor element-containing material and the glass component material are weighed and filled in a crucible. Examples of the material for the crucible include platinum, platinum-rhodium, iridium, alumina, quartz, carbon, and the like, and are appropriately selected in consideration of the melting temperature, atmosphere, reactivity with the molten material, and the like.
Next, it heats with the temperature according to a glass composition with an electric furnace, and is set as a melt. At this time, it is desirable to stir the melt uniformly.
Subsequently, the obtained melt is poured onto a zirconia substrate, a carbon substrate or the like to vitrify the melt.
Finally, the glass is crushed into powder. A known method such as a jet mill, a bead mill, or a ball mill can be applied to the pulverization.

  The content ratio of the glass powder containing the donor element in the n-type diffusion layer forming composition is determined in consideration of the coating property and the diffusibility of the donor element. In general, the content ratio of the glass powder in the n-type diffusion layer forming composition is preferably 0.1% by mass or more and 95% by mass or less, more preferably 1% by mass or more and 90% by mass or less, The content is more preferably 1.5% by mass or more and 85% by mass or less, and particularly preferably 2% by mass or more and 80% by mass or less.

The n-type diffusion layer forming composition contains at least one curable resin.
After coating the n-type diffusion layer forming composition to form a coating film, the curable resin is cured, so that the shape of the coating film can be changed even when an alcohol solvent such as ethanol is applied to the coating film. The n-type diffusion layer can be formed in a desired shape.

The curable resin is preferably used as a thermosetting resin composition or a photocurable resin composition. By using a thermosetting resin composition or a photocurable resin composition, an n-type diffusion layer can be formed with higher productivity.
The thermosetting resin composition includes a curable resin and a thermosetting agent, and the photocurable resin composition includes a curable resin and a photocuring agent.

The curable resin used in the present invention is preferably a curable resin having a high dispersibility of glass powder when formed into a paste, a good film formability, and a high surface hardness after curing.
Examples of such curable resins include acrylic resins, epoxy resins, melamine resins, polyester resins, urethane resins, alkyd resins, and the like.

  The use of an acrylic resin as the curable resin is also preferable from the viewpoint of pigment dispersibility.

  Examples of acrylic resins include 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, lauryl methacrylate, stearyl methacrylate, benzyl methacrylate, benzyl acrylate, Acrylic acid ester or methacrylic acid such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl methacrylate, hexyl acrylate, octyl methacrylate, octyl acrylate, phosphorus-containing methacrylate, etc. Ether, styrene, styrene derivatives, homopolymers or copolymers of other polymerizable monomers, and the like.

  The acrylic resin is (meth) acrylic acid (meaning acrylic acid and methacrylic acid; the same applies hereinafter), itaconic acid, maleic acid, maleic anhydride, monoalkyl maleate, citraconic acid, citraconic anhydride, citracone Copolymers of carboxyl group-containing polymerizable monomers such as acid monoalkyl esters and (meth) acrylic acid esters, styrene, styrene derivatives, and other polymerizable monomers may also be used.

  The maleic acid monoalkyl ester that can constitute the acrylic resin is preferably an alkyl having 1 to 12 carbon atoms, monomethyl maleate, monoethyl maleate, mono-n-propyl maleate, monoisopropyl maleate, Mono-n-butyl maleate, mono-n-hexyl maleate, mono-n-octyl maleate, mono-2-ethylhexyl maleate, mono-n-nonyl maleate, mono-n-dodecyl maleate, etc. It is done.

  As the citraconic acid monoalkyl ester that can constitute the acrylic resin, those having 1 to 12 carbon atoms of alkyl are preferable, citraconic acid monomethyl, citraconic acid monoethyl, citraconic acid mono-n-propyl, citraconic acid monoisopropyl, Citraconate mono-n-butyl, citraconic acid mono-n-hexyl, citraconic acid mono-n-octyl, citraconic acid mono-2-ethylhexyl, citraconic acid mono-n-nonyl, citraconic acid mono-n-dodecyl, etc. It is done.

  Examples of the styrene derivative that can constitute the acrylic resin include α-methylstyrene, m- or p-methoxystyrene, p-hydroxystyrene, 2-methoxy-4-hydroxystyrene, 2-hydroxy-4-methylstyrene, and the like. Can be mentioned.

Other polymerizable monomers that can constitute the acrylic resin include N-cyclohexylmaleimide, N-2-methylhexylmaleimide, N-2-ethylcyclohexylmaleimide, N-2-chlorocyclohexylmaleimide, N-phenylmaleimide, N- 2-methylphenylmaleimide, N-2-ethylphenylmaleimide, N-2-chlorophenylmaleimide, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, tricyclo [5.2.1.0 ^{2, 6} ] (meth) acrylic acid ester having a decanyl group.

  Moreover, as an acrylic resin, you may use what has light or a thermopolymerizable unsaturated bond. Preferable examples of such a resin include, for example, glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether, α-ethyl glycidyl acrylate, crotonyl glycidyl ether, monoalkyl glycidyl itaconate, on a high acid value carboxyl group-containing acrylic resin. Compounds having an oxirane ring such as ether and one ethylenically unsaturated bond, allyl alcohol, 2-buten-4-ol, furfuryl alcohol, oleyl alcohol, cinnamyl alcohol, 2-hydroxyethyl acrylate, 2-hydroxy Resin obtained by reacting a hydroxyl group such as ethyl methacrylate and N-methylolacrylamide with a compound (unsaturated alcohol) each having one ethylenically unsaturated bond, a carboxyl group-containing tree having a hydroxyl group A resin obtained by reacting an unsaturated compound containing a free isocyanate group with a resin, a resin obtained by reacting an addition reaction product of an epoxy resin and an unsaturated carboxylic acid with a polybasic acid anhydride, a conjugated diene polymer or a conjugated diene copolymer. Examples thereof include a resin obtained by reacting an addition reaction product with a saturated dicarboxylic acid anhydride with a hydroxyl group-containing polymerizable monomer.

  A bifunctional or higher functional epoxy resin is used as the epoxy resin. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, alicyclic epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, polyfunctional phenol diglycyl Etherified products, hydrogenated products thereof and the like can be mentioned, and several types can be used in combination.

  Melamine resins include N-monomethylol melamine, N, N′-dimethylol melamine, N, N ′, N ″ -trimethylol melamine, N, N, N ′, N ″ -tetramethylol melamine, N, N, N ′, N ′, N ″,-pentamethylol melamine, N, N, N ′, N ′, N ″, N ″ -hexamethylol melamine, N-monomethoxymethyl melamine, N, N ′ -Dimethoxymethylmelamine, N, N ', N "-trimethoxymethylmelamine, N, N, N', N" -tetramethoxymethylmelamine, N, N, N ', N', N ''-penta Methoxymethylmelamine, N, N, N ′, N ′, N ′, N′-hexamethoxymethylmelamine, N-monobutyrolmelamine, N, N′-dibutyrolmelamine, N, N ′, N ″- Tribylol melamine, N, N, N ′, N ″ -tetrabutyrol melamine, N, N, N ′, N ′, N ″ -pentabtyrol melamine N, N, N ′, N ′, N ″, N ″ -hexabutyrolol melamine, N-monobutoxymethyl melamine, N, N′-dibutoxymethyl melamine, N, N ′, N ″ − Tributoxymethyl melamine, N, N, N ′, N ″ -tetrabutoxymethyl melamine, N, N, N ′, N ′, N′-pentaboxymethyl melamine, N, N, N ′, N ′, N Monomers or quantifiers such as '', N ''-hexabutoxymethyl melamine. These can be used alone or in combination of two or more.

As the urethane resin, a reaction product of polyol (A) and isocyanate (B) is used.
Polyol (A) is a compound containing two or more alcoholic hydroxyl groups, such as trimethylolpropane, propane-1,2,3-triol, 1,4-butanediol, 1,3-propanediol, polycaprolactone. Examples include diol, polycaprolactone triol, polycarbonate diol, polycarbonate triol, polyester diol, and polyether diol. These polyols can be used individually by 1 type or in combination of 2 or more types.
Examples of the isocyanate (B) include 1,3-bis (isocyanatomethyl) cyclohexane, norbornene diisocyanate (2,5- (2,6) bisisocyanatomethyl [2,2,1] heptane), isophorone diisocyanate, 4,4'-methylenebis (siloxyhexyl isocyanate), isopropylidenebis (4-cyclohexylisocyanate), cyclohexyl diisocyanate and the like.
These isocyanates can be used individually by 1 type or in combination of 2 or more types.

A curable resin is used individually by 1 type or in combination of 2 or more types.
The weight average molecular weight of the curable resin is not particularly limited, and it is desirable to adjust appropriately in view of the desired viscosity as the composition.
The weight average molecular weight is preferably from 5,000 to 500,000, more preferably from 10,000 to 200,000, and most preferably from 20,000 to 100,000, from the viewpoints of solubility in a solvent and handleability of the dissolved product.
The weight average molecular weight can be measured by, for example, the GPC method.

  Epoxy resins, melamine resins, and urethane resins can be used alone, but may be used in combination with curable resins such as acrylic resins as thermosetting agents (crosslinked monomers).

  The thermosetting resin composition is particularly preferably an acrylic-melamine resin composition using an acrylic resin as the curable resin and a melamine resin as the cross-linked monomer from the viewpoint of the dispersibility and surface hardness of the glass powder.

The content of the curable resin in the present invention is 0.01% by mass to 30% by mass, preferably 0.2% by mass to 10% by mass, based on the total solid content in the n-type diffusion layer forming composition. More preferably, it is 1 mass%-5 mass%.
By setting the content of the curable resin within this range, the glass powder can be fixed on the semiconductor substrate, and a sufficient amount of the acceptor element can contribute to the diffusion, which is preferable.

Moreover, content of the thermosetting agent in this invention is 0.01 mass%-5 mass% with respect to the solid content total amount in n type diffused layer formation composition, Preferably it is 0.05 mass%-2 It is mass%, More preferably, it is 0.1 mass%-1 mass%.
The content of the thermosetting agent is preferably within this range, since the coating film strength of the n-type diffusion layer forming composition can be sufficiently maintained.

  In addition, the curable resin used in the present invention produces (b) one or more polymerizable monomers or oligomers having at least one ethylenically unsaturated group and (c) irradiation of active energy rays to generate free radicals. It is also preferable to use it as a photocurable composition by using it together with a photocuring agent composed of a polymerization initiator.

  In addition, the (b) at least one or more polymerizable monomers or oligomers that can constitute a photocuring agent are preferably one or more polymerizable monomers or oligomers having at least one ethylenically unsaturated group, Conventionally, it can be appropriately selected from those known as photopolymerizable polyfunctional monomers.

  Specifically, examples of monomers having one unsaturated bond include ester monomers of acrylic acid or methacrylic acid (methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, acrylic acid n- Propyl, n-propyl methacrylate, iso-propyl acrylate, iso-propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, iso-butyl acrylate, iso-butyl methacrylate, sec-butyl acrylate, Sec-butyl methacrylate, tert-butyl methacrylate, tert-butyl methacrylate, pentyl acrylate, pentyl methacrylate, hexyl acrylate, hexyl methacrylate, heptyl acrylate, heptyl methacrylate, 2-ethylhexyl acrylate, methacrylic acid 2 -Ethylhexyl, octyl acrylate, octyl methacrylate, nonyl acrylate, nonyl methacrylate, decyl acrylate, decyl methacrylate, dodecyl acrylate, dodecyl methacrylate, tetradecyl acrylate, tetradecyl methacrylate, hexadecyl acrylate, hexadecyl methacrylate , Octadecyl acrylate, octadecyl methacrylate, eicosyl acrylate, eicosyl methacrylate, docosyl acrylate, docosyl methacrylate, cyclopentyl acrylate, cyclopentyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, cycloheptyl acrylate, cycloheptyl methacrylate Benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, Methoxyethyl phosphate, methoxyethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminopropyl acrylate, dimethylaminopropyl methacrylate, 2-chloroethyl acrylate, 2-chloroethyl methacrylate, 2-acrylic acid 2- Fluoroethyl, 2-fluoroethyl methacrylate, 2-cyanoethyl acrylate, 2-cyanoethyl methacrylate, methoxydiethylene glycol acrylate, methoxydiethylene glycol methacrylate, methoxydipropylene glycol acrylate, methoxydipropylene glycol methacrylate, methoxytriacrylate Ethylene glycol, methoxytriethylene glycol methacrylate, etc.), styrene monomer (styrene, α-methylstyrene) , Pt-butylstyrene, etc.), polyolefin monomers (butadiene, isoprene, chloroprene, etc.), vinyl monomers (vinyl chloride, vinyl acetate, etc.), nitrile monomers (acrylonitrile, methacrylonitrile, etc.), 1- (methacrylic). And leuoxyethoxycarbonyl) -2- (3'-chloro-2'-hydroxypropoxycarbonyl) benzene.

  Examples of the monomer having two unsaturated bonds include ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate. Acrylate, tetraethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, hexapropylene glycol diacrylate, hexapropylene glycol dimethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, butylene glycol diacrylate, butylene glycol dimethacrylate Neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1, 5-pentanediol diacrylate, 1,5-pentanediol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, pentaerythritol diacrylate, pentaerythritol dimethacrylate, trimethylolpropane diacrylate, Trimethylolpropane dimethacrylate, bisphenol A diacrylate, bisphenol A dimethacrylate, 2,2-bis (4-acryloxyethoxyphenyl) Lopan, 2,2-bis (4-methacryloxyethoxyphenyl) propane, 2,2-bis (4-acryloxydiethoxyphenyl) propane, 2,2-bis (4-methacryloxydiethoxyphenyl) propane, 2 , 2-bis (4-acryloxypolyethoxyphenyl) propane, 2,2-bis (4-methacryloxypolyethoxyphenyl) propane, bisphenol A diglycidyl ether diacrylate, bisphenol A diglycidyl ether dimethacrylate, urethane diacrylate Compounds and the like.

  Examples of the monomer having three unsaturated bonds include trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, ethylene oxide modified trimethylolpropane triacrylate, ethylene oxide modified trimethylol. Examples include propane trimethacrylate, trimethylolpropane triglycidyl ether triacrylate, trimethylolpropane triglycidyl ether trimethacrylate, and the like.

  Examples of the monomer having four unsaturated bonds include tetramethylolpropane tetraacrylate, tetramethylolpropane tetramethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, and the like.

  Examples of the monomer having five unsaturated bonds include dipentaerythritol pentaacrylate and dipentaerythritol pentamethacrylate.

Examples of the monomer having six unsaturated bonds include dipentaerythritol hexaacrylate and dipentaerythritol hexamethacrylate.
In any case, these monomers having an unsaturated bond may be those that undergo radical polymerization by light irradiation, and these monomers having an unsaturated bond may be used alone or in combination of two or more. Used in combination.
The content of at least one or more polymerizable monomers or oligomers that can constitute the photo-curing agent is in the n-type diffusion layer forming composition in order to obtain the coating strength of the n-type diffusion layer forming composition. It is preferable to set it as 0.05 mass%-10 weight% of solid total amount of this, and it is more preferable that it is 0.1 mass%-1 weight%.

Examples of the polymerization initiator that can form a photocuring agent (c) that generates free radicals upon irradiation with active energy rays include benzophenone, N, N′-tetraethyl-4,4′-diaminobenzophenone, 4-methoxy. -4'-dimethylaminobenzophenone, benzyl, 2,2-diethoxyacetophenone, benzoin, benzoin methyl ether, benzoin isobutyl ether, benzyldimethyl ketal, α-hydroxyisobutylphenone, thioxanthone, 2-chlorothioxanthone, 1-hydroxycyclohexylphenyl Ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-1-propane, t-butylanthraquinone, 1-chloroanthraquinone, 2,3-dichloroanthraquinone, 3-chloro-2-me Tyranthraquinone, 2-ethylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthraquinone, 1,2-benzoanthraquinone lati-1,4-dimethylanthraquinone, 2-phenylanthraquinone, 2- (o-chlorophenyl) Examples include -4,5-diphenylimidazole dimer.
These polymerization initiators are used alone or in combination of two or more.
The content of the (c) polymerization initiator that can constitute the photocuring agent is n-type diffusion from the viewpoint of allowing a sufficient amount of active energy rays to reach the coating film thickness direction of the n-type diffusion layer forming composition. It is preferable to set it as 0.0005 mass%-0.05 weight% of solid content total amount in a layer forming composition, and it is more preferable that it is 0.001 mass%-0.01 weight%.

  The n-type diffusion layer forming composition of the present invention may contain other binder as needed as a medium (dispersion medium) for dispersing the glass powder in the composition, in addition to the curable resin.

Other binders include, for example, polyvinyl alcohol, polyacrylamides, polyvinylamides, polyvinylpyrrolidone, polyethylene oxides, polysulfonic acid, acrylamide alkylsulfonic acid, cellulose ethers, cellulose derivatives, carboxymethylcellulose, hydroxyethylcellulose, ethylcellulose, gelatin , Starch and starch derivatives, sodium alginate, xanthan, guar and gua derivatives, scleroglucan and scleroglucan derivatives, tragacanth and tragacanth derivatives, dextrin and dextrin derivatives, butadiene resins, styrene resins, or copolymers thereof, etc. In addition, a siloxane resin can be appropriately selected.
These are used singly or in combination of two or more.

The weight average molecular weight of the other binder is not particularly limited, and it is desirable to adjust appropriately in view of the desired viscosity as the composition.
The weight average molecular weight is preferably from 5,000 to 500,000, more preferably from 10,000 to 200,000, and most preferably from 20,000 to 100,000, from the viewpoints of solubility in a solvent and handleability of the dissolved product.

The n-type diffusion layer forming composition preferably contains at least one solvent.
Examples of the solvent include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-iso-propyl ketone, methyl-n-butyl ketone, methyl-iso-butyl ketone, methyl-n-pentyl ketone, methyl-n-hexyl ketone, Ketone solvents such as diethyl ketone, dipropyl ketone, di-iso-butyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone; diethyl ether, methyl ethyl ether, methyl -N-propyl ether, di-iso-propyl ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether Ter, ethylene glycol di-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether , Diethylene glycol di-n-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl n-butyl ether, triethylene glycol di-n- Butyl ether, G Ethylene glycol methyl-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetradiethylene glycol methyl ethyl ether, tetraethylene glycol methyl n-butyl ether, diethylene glycol di-n-butyl ether, tetraethylene glycol methyl n-hexyl Ether, tetraethylene glycol di-n-butyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl ethyl Ether, zip Lopylene glycol methyl-n-butyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene Glycol methyl ethyl ether, tripropylene glycol methyl-n-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetradipropylene glycol methyl ethyl Ether, tetrapropylene glycol methyl-n-butyl ether Ether solvents such as dipropylene glycol di-n-butyl ether, tetrapropylene glycol methyl-n-hexyl ether, tetrapropylene glycol di-n-butyl ether; methyl acetate, ethyl acetate, n-propyl acetate, i-propyl acetate, acetic acid n-butyl, i-butyl acetate, sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2- Butoxyethoxy) ethyl, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, nonyl acetate, methyl acetoacetate, ethyl acetoacetate, diethylene glycol methyl ether acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol acetate Methyl ether, dipropylene glycol ethyl ether, glycol diacetate, methoxytriglycol acetate, ethyl propionate, n-butyl propionate, i-amyl propionate, diethyl oxalate, di-n-butyl oxalate, lactic acid Methyl, ethyl lactate, n-butyl lactate, n-amyl lactate, ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene Ester solvents such as glycol ethyl ether acetate, propylene glycol propyl ether acetate, γ-butyrolactone, γ-valerolactone; N-methylpyrrolidinone, N-ethylpyrrolidinone, N-propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, etc. Aprotic polar solvent: methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, sec-butanol, t-butanol, n-pentanol, i-pentanol, 2-methylbutanol, sec -Pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, phenol, cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol, Alcohol solvents such as 1,2-propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, Diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol Mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, ethoxytriglycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether Glycol monoether solvents such as α-terpinene, α-terpineol, myrcene, alloocimene, limonene, dipentene, α-pinene, β-pinene, terpineol, carvone, ocimene, and ferrandrene; water . These are used singly or in combination of two or more.
In the case of an n-type diffusion layer forming composition, α-terpineol, diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether, and 2- (2-butoxyethoxy) ethyl acetate are used from the viewpoint of applicability to the substrate. Α-Terpineol, diethylene glycol mono-n-butyl ether, and 2- (2-butoxyethoxy) ethyl acetate are more preferable solvents.

The content ratio of the solvent in the n-type diffusion layer forming composition is determined in consideration of applicability and donor concentration.
The viscosity of the n-type diffusion layer forming composition is preferably 10 mPa · S or more and 1000000 mPa · S or less, more preferably 50 mPa · S or more and 500000 mPa · S or less in consideration of applicability.
The viscosity can be measured at 25 ° C. and 5 rpm using, for example, an E-type viscometer.

Furthermore, the n-type diffusion layer forming composition may contain other additives. Examples of other additives include metals that easily react with the glass powder.
The n-type diffusion layer forming composition is applied on a semiconductor substrate and heat-treated at a high temperature to form an n-type diffusion layer. At that time, glass is formed on the surface. This glass is removed by dipping in an acid such as hydrofluoric acid, but some glass is difficult to remove depending on the type of glass. In that case, the glass can be easily removed after the acid cleaning by adding a metal such as Ag, Mn, Cu, Fe, Zn, or Si. Among these, it is preferable to use at least one selected from Ag, Si, Cu, Fe, Zn and Mn, more preferable to use at least one selected from Ag, Si and Zn. It is particularly preferred.

  The content ratio of the metal is desirably adjusted as appropriate depending on the type of glass and the type of the metal, and is generally preferably 0.01% by mass or more and 10% by mass or less with respect to the glass powder.

  Next, the manufacturing method of the n type diffused layer and solar cell element of this invention is demonstrated, referring FIG. FIG. 1 is a schematic cross-sectional view conceptually showing an example of the manufacturing process of the solar cell element of the present invention. In the subsequent drawings, common constituent elements are denoted by the same reference numerals.

In FIG. 1A, an alkaline solution is applied to a silicon substrate which is a p-type semiconductor substrate 10 to remove a damaged layer, and a texture structure is obtained by etching.
Specifically, the damaged layer on the silicon surface generated when slicing from the ingot is removed with 20% by mass caustic soda. Next, etching is performed with a mixed solution of 1% by mass caustic soda and 10% by mass isopropyl alcohol to form a texture structure (the description of the texture structure is omitted in the figure). In the solar cell element, by forming a texture structure on the light receiving surface (surface) side, a light confinement effect is promoted, and high efficiency is achieved.

In FIG. 1B, the n-type diffusion layer forming composition layer 11 is formed by applying the n-type diffusion layer forming composition to the surface of the p-type semiconductor substrate 10, that is, the surface that becomes the light receiving surface. In the present invention, the application method is not limited, and examples thereof include a printing method, a spin method, a brush coating, a spray method, a doctor blade method, a roll coater method, and an ink jet method.
Is not particularly limited as coated amount of the n-type diffusion layer forming composition, for example, be a 0.01g ^{/ m 2} ~100g ^/ m 2 as a glass powder content, 0.1 g ^/ m 2 to 10 g / M ² is preferable.

  Depending on the composition of the n-type diffusion layer forming composition, a drying step for volatilizing the solvent contained in the composition may be necessary after coating. In this case, drying is performed at a temperature of about 80 ° C. to 300 ° C. for 1 minute to 10 minutes when a hot plate is used, and about 10 minutes to 30 minutes when a dryer or the like is used. The drying conditions depend on the solvent composition of the n-type diffusion layer forming composition, and are not particularly limited to the above conditions in the present invention.

Further, when the manufacturing method of the present invention is used, the manufacturing method of the p ⁺ -type diffusion layer (high concentration electric field layer) 14 on the back surface is limited to a method by conversion from an n-type diffusion layer to a p-type diffusion layer with aluminum. Therefore, any conventionally known method can be adopted, and the options of the manufacturing method are expanded. Therefore, for example, the high-concentration electric field layer 14 can be formed by applying the composition 13 containing a Group 13 element such as B (boron).
As the composition 13 containing a Group 13 element such as B (boron), for example, a glass powder containing an acceptor element is used instead of a glass powder containing a donor element, and the same as the composition for forming an n-type diffusion layer. A p-type diffusion layer forming composition constituted as described above can be given. The acceptor element may be an element belonging to Group 13, and examples thereof include B (boron), Al (aluminum), and Ga (gallium). The glass powder containing acceptor element preferably comprises at least one selected from _{B 2 O 3, Al 2 O} 3 and _Ga 2 _{O 3.}
Furthermore, the method for applying the p-type diffusion layer forming composition to the back surface of the silicon substrate is the same as the method for applying the n-type diffusion layer forming composition described above on the silicon substrate.
The high-concentration electric field layer 14 can be formed on the back surface by subjecting the p-type diffusion layer forming composition applied to the back surface to a thermal diffusion treatment similar to the thermal diffusion treatment in the n-type diffusion layer forming composition described later. . The thermal diffusion treatment of the p-type diffusion layer forming composition is preferably performed simultaneously with the thermal diffusion treatment of the n-type diffusion layer forming composition.

Next, the semiconductor substrate 10 on which the n-type diffusion layer forming composition layer 11 is formed is subjected to thermal diffusion treatment at 600 ° C. to 1200 ° C. By this thermal diffusion treatment, as shown in FIG. 1C, the donor element diffuses into the semiconductor substrate, and the n-type diffusion layer 12 is formed. A known continuous furnace, batch furnace, or the like can be applied to the thermal diffusion treatment. Further, the furnace atmosphere during the thermal diffusion treatment can be appropriately adjusted to air, oxygen, nitrogen or the like.
The thermal diffusion treatment time can be appropriately selected according to the content of the donor element contained in the n-type diffusion layer forming composition. For example, it may be 1 minute to 60 minutes, and more preferably 2 minutes to 30 minutes.

Moreover, before performing a thermal diffusion process, it can also have the process of hardening | curing curable resin contained in the n-type diffused layer formation composition layer 11 formed on the semiconductor substrate 10. FIG.
When a thermosetting agent is used in addition to the curable resin, the curable resin can be cured by preheating.
The temperature for preheating is preferably 50 ° C to 300 ° C, more preferably 100 ° C to 250 ° C.
The time for performing the preheating may be within a range in which a sufficient curing reaction can be obtained even during mass production, and can be, for example, 5 minutes to 30 minutes, and more preferably 10 minutes to 20 minutes.
On the other hand, when a photocuring agent is used in addition to the curable resin, it can be cured using active energy rays. The active energy ray can be irradiated using a known active light source. Examples of the active light source include a carbon arc lamp, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, and a xenon lamp. The irradiation amount of the actinic ray is usually 0.005 J / cm ^{2 to 1} J / cm ² . Further, after the light irradiation, preliminary heating may be further performed. The preheating conditions are the same as described above.

  Since a glass layer (not shown) such as phosphate glass is formed on the surface of the formed n-type diffusion layer 12, this phosphate glass is removed by etching. As the etching, a known method such as a method of immersing in an acid such as hydrofluoric acid or a method of immersing in an alkali such as caustic soda can be applied.

In the method for forming an n-type diffusion layer of the present invention in which the n-type diffusion layer 12 is formed using the n-type diffusion layer forming composition 11 of the present invention shown in FIGS. Thus, the n-type diffusion layer 12 is formed, and no unnecessary n-type diffusion layer is formed on the back surface or the side surface.
Therefore, in the conventional method of forming an n-type diffusion layer by a gas phase reaction method, a side etching process for removing an unnecessary n-type diffusion layer formed on a side surface is essential. According to the manufacturing method of the invention, the side etching process is not required, and the process is simplified.

Further, in the conventional manufacturing method, it is necessary to convert an unnecessary n-type diffusion layer formed on the back surface into a p-type diffusion layer. As this conversion method, a group 13 element is added to the n-type diffusion layer on the back surface. A method is adopted in which an aluminum paste is applied and baked to diffuse aluminum into the n-type diffusion layer and convert it into a p-type diffusion layer. In this method, in order to sufficiently convert to the p-type diffusion layer and to form a high concentration electric field layer of p ⁺ layer, an aluminum amount of a certain amount or more is required. Therefore, the aluminum layer is formed thick. There was a need. However, since the thermal expansion coefficient of aluminum is significantly different from that of silicon used as a substrate, a large internal stress is generated in the silicon substrate during the firing and cooling process, causing warpage of the silicon substrate. .
This internal stress has a problem that the crystal grain boundary is damaged and the power loss increases. Further, the warpage easily damages the solar cell element in the transportation of the solar cell element in the module process and the connection with a copper wire called a tab wire. In recent years, the thickness of the silicon substrate has been reduced due to the improvement of the slice processing technique, and the solar cell element tends to be easily broken.

  However, according to the manufacturing method of the present invention, since an unnecessary n-type diffusion layer is not formed on the back surface, it is not necessary to perform conversion from the n-type diffusion layer to the p-type diffusion layer, and the necessity of increasing the thickness of the aluminum layer is eliminated. . As a result, generation of internal stress and warpage in the silicon substrate can be suppressed. As a result, it is possible to suppress an increase in power loss and damage to the solar cell element.

Further, when the manufacturing method of the present invention is used, the manufacturing method of the p ⁺ -type diffusion layer (high concentration electric field layer) 14 on the back surface is limited to a method by conversion from an n-type diffusion layer to a p-type diffusion layer with aluminum. Any method can be adopted without any problem, and the choice of manufacturing method is expanded.
For example, using a glass powder containing an acceptor element instead of a glass powder containing a donor element, a p-type diffusion layer forming composition configured in the same manner as the n-type diffusion layer forming composition is formed on the back surface (n The p ⁺ -type diffusion layer (high-concentration electric field layer) 14 is preferably formed on the back surface by applying to the surface opposite to the surface on which the mold diffusion layer forming composition is applied and baking.
As will be described later, the material used for the back surface electrode 20 is not limited to Group 13 aluminum, and for example, Ag (silver) or Cu (copper) can be applied. In addition, it can be formed thinner than the conventional one.

In FIG. 1 (4), an antireflection film 16 is formed on the n-type diffusion layer 12. The antireflection film 16 is formed by applying a known technique. For example, when the antireflection film 16 is a silicon nitride film, it is formed by a plasma CVD method using a mixed gas of SiH ₄ and NH ₃ as a raw material. At this time, hydrogen diffuses into the crystal, and orbits that do not contribute to the bonding of silicon atoms, that is, dangling bonds and hydrogen are combined to inactivate defects (hydrogen passivation).
More specifically, the mixed gas flow ratio NH ₃ / SiH ₄ is 0.05 to 1.0, the pressure in the reaction chamber is 0.1 Torr to 2 Torr, the temperature during film formation is 300 ° C. to 550 ° C., It is formed under the condition that the frequency for discharge is 100 kHz or more.

  In FIG. 1 (5), the surface electrode 18 is formed on the antireflection film 16 on the surface (light-receiving surface) by printing and drying the surface electrode metal paste by screen printing. The metal paste for a surface electrode contains (1) metal particles and (2) glass particles as essential components, and includes (3) a resin binder and (4) other additives as necessary.

  Next, the back electrode 20 is also formed on the high-concentration electric field layer 14 on the back surface. As described above, in the present invention, the material and forming method of the back electrode 20 are not particularly limited. For example, the back electrode 20 may be formed by applying and drying a back electrode paste containing a metal such as aluminum, silver, or copper. At this time, a silver paste for forming a silver electrode may be partially provided on the back surface for connection between solar cell elements in the module process.

  In FIG. 1 (6), an electrode is baked and a solar cell element is completed. When firing at a temperature of 600 ° C. to 900 ° C. for several seconds to several minutes, the antireflection film 16 that is an insulating film is melted by the glass particles contained in the electrode metal paste on the surface side, and the silicon 10 surface is also partially melted. The metal particles (for example, silver particles) in the paste form a contact portion with the silicon substrate 10 and solidify. Thereby, the formed surface electrode 18 and the silicon substrate 10 are electrically connected. This is called fire-through.

  The shape of the surface electrode 18 will be described. The surface electrode 18 includes a bus bar electrode 30 and finger electrodes 32 intersecting with the bus bar electrode 30. FIG. 2A is a plan view of a solar cell element in which the surface electrode 18 includes a bus bar electrode 30 and a finger electrode 32 intersecting with the bus bar electrode 30 as viewed from the surface. FIG. 2B is an enlarged perspective view illustrating a part of FIG.

  Such a surface electrode 18 can be formed by means such as screen printing of the above-described metal paste, plating of an electrode material, or vapor deposition of an electrode material by electron beam heating in a high vacuum. The surface electrode 18 composed of the bus bar electrode 30 and the finger electrode 32 is generally used as an electrode on the light receiving surface side and is well known, and it is possible to apply known forming means for the bus bar electrode and finger electrode on the light receiving surface side. it can.

In the above description, the solar cell element in which the n-type diffusion layer is formed on the front surface, the p ⁺ -type diffusion layer is formed on the back surface, and the front surface electrode and the back surface electrode are further provided on the respective layers has been described. If a layer formation composition is used, it is also possible to produce a back contact type solar cell element.
The back contact type solar cell element has all electrodes provided on the back surface to increase the area of the light receiving surface. That is, in the back contact type solar cell element, it is necessary to form both the n-type diffusion region and the p ⁺ -type diffusion region on the back surface to form a pn junction structure. The n-type diffusion layer forming composition of the present invention can form an n-type diffusion site at a specific site, and can therefore be suitably applied to the production of a back contact type solar cell element.

  Examples of the present invention will be described more specifically below, but the present invention is not limited to these examples. Unless otherwise stated, all chemicals used reagents. “%” Means “% by mass” unless otherwise specified.

[Example 1]
P ₂ O ₅ -V ₂ O ₅ -based glass _{(P 2 O 5: 29.6%} , V 2 O 5: 10%, BaO: 10.4%, MoO 3: 10%, WO 3: 30%, K ₂ O: 10%) 20 g powder, methyl methacrylate (60 parts by mass): N-cyclohexylmaleimide (10 parts by mass): acrylic copolymer consisting of 2-hydroxyethyl acrylate (30 parts by mass) (weight average molecular weight 50000) 0.3 g, 0.1 g of N, N, N ′, N ′, N ″, N ″ -hexabutoxymethylmelamine and 7 g of 2- (2-butoxyethoxy) ethyl acetate using an automatic mortar kneader An n-type diffusion layer forming composition was prepared by mixing and pasting.

Next, the prepared paste was applied to the p-type silicon substrate surface by screen printing to form a coating film, and heated on a hot plate at 200 ° C. for 10 minutes to thermally cure the coating film.
Subsequently, ethanol was applied to the coating film to clean the surface, and the film was dried in the air. The shape of the coating film was maintained, and there was no change such as expansion of the coating film area.
Subsequently, thermal diffusion treatment was performed for 10 minutes in an electric furnace set at 1000 ° C., and then the substrate was immersed in hydrofluoric acid for 5 minutes in order to remove the glass layer, and washed with running water. There was some deposit on the surface, but it could be easily removed by rubbing with a waste cloth. After washing with running water, it was dried in the air.

  The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 186 Ω / □, and P (phosphorus) diffused to form an n-type diffusion layer. The sheet resistance on the back surface was 1000000 Ω / □ or more and could not be measured, and the n-type diffusion layer was not substantially formed.

[Example 2]
Methyl methacrylate (60 parts by mass): N-cyclohexylmaleimide (10 parts by mass): Ethyl cellulose as a curable resin instead of an acrylic copolymer (weight average molecular weight 50000) consisting of 2-hydroxyethyl acrylate (30 parts by mass) An n-type diffusion layer forming composition was prepared in the same manner as in Example 1 except that (ethylation degree 50%, weight average molecular weight 50,000) was used.
Next, the prepared paste was applied to the p-type silicon substrate surface by screen printing to form a coating film, and heated on a hot plate at 200 ° C. for 10 minutes to thermally cure the coating film.
Subsequently, ethanol was applied to the coating film to clean the surface and dried in the air. The shape of the coating film was maintained, and there was no change such as expansion of the coating film area.
Subsequently, thermal diffusion treatment was performed for 10 minutes in an electric furnace set at 1000 ° C., and then the substrate was immersed in hydrofluoric acid for 5 minutes in order to remove the glass layer, and washed with running water. There was some deposit on the surface, but it could be easily removed by rubbing with a waste cloth. After washing with running water, it was dried in the air.
The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 186 Ω / □, and P (phosphorus) diffused to form an n-type diffusion layer. The sheet resistance on the back surface was 1000000 Ω / □ or more and could not be measured, and the n-type diffusion layer was not substantially formed.

[Example 3]
P ₂ O ₅ -V ₂ O ₅ -based glass _{(P 2 O 5: 29.6%} , V 2 O 5: 10%, BaO: 10.4%, MoO 3: 10%, WO 3: 30%, K ₂ O: 10%) 20 g powder, methyl methacrylate (60 parts by mass): N-cyclohexylmaleimide (10 parts by mass): acrylic copolymer consisting of 2-hydroxyethyl acrylate (30 parts by mass) (weight average molecular weight 50000) 0.3 g, 0.1 g of pentaerythritol triacrylate, 0.001 g of N, N′-tetraethyl-4,4′-diaminobenzophenone and 7 g of 2- (2-butoxyethoxy) ethyl acetate as a photopolymerization initiator, automatic mortar An n-type diffusion layer forming composition was prepared by mixing using a kneader and forming a paste.
Next, the prepared paste is applied to the surface of the p-type silicon substrate by screen printing to form a coating film, irradiated with ultraviolet rays of 0.06 J / cm ² from above the coating film, and then on a hot plate at 200 ° C. The coating was cured by heating for 10 minutes.
Subsequently, ethanol was applied to the coating film to clean the surface and dried in the air. The shape of the coating film was maintained, and there was no change such as expansion of the coating film area.
Subsequently, thermal diffusion treatment was performed for 10 minutes in an electric furnace set at 1000 ° C., and then the substrate was immersed in hydrofluoric acid for 5 minutes in order to remove the glass layer, and washed with running water. There was some deposit on the surface, but it could be easily removed by rubbing with a waste cloth. After washing with running water, it was dried in the air.

  The sheet resistance of the surface on which the n-type diffusion layer forming composition was applied was 186 Ω / □, and P (phosphorus) diffused to form an n-type diffusion layer. The sheet resistance on the back surface was 1000000 Ω / □ or more and could not be measured, and the n-type diffusion layer was not substantially formed.

[Comparative Example 1]
P ₂ O ₅ -V ₂ O ₅ -based glass _{(P 2 O 5: 29.6%} , V 2 O 5: 10%, BaO: 10.4%, MoO 3: 10%, WO 3: 30%, K ₂ O: 10%) powder, 20 g, ethyl cellulose (ethylation degree 50%, weight average molecular weight 50,000) 0.3 g and 2- (2-butoxyethoxy) ethyl acetate 7 g were mixed using an automatic mortar kneader. Thus, an n-type diffusion layer forming composition was prepared.
Next, the prepared paste was applied to the p-type silicon substrate surface by screen printing to form a coating film, and heated on a hot plate at 200 ° C. for 10 minutes to thermally cure the coating film.
Subsequently, ethanol was applied to the coating film and dried in the atmosphere. As a result, the surface of the coating film became white and the area of the coating film was enlarged.
Subsequently, thermal diffusion treatment was performed for 10 minutes in an electric furnace set at 1000 ° C., and then the substrate was immersed in hydrofluoric acid for 5 minutes in order to remove the glass layer, and washed with running water. There was some deposit on the surface, but it could be easily removed by rubbing with a waste cloth. After washing with running water, it was dried in the air.
As a result, an n-type diffusion layer was formed over the entire enlarged region.

[Comparative Example 2]
An n-type diffusion layer forming composition was prepared in the same manner as in Comparative Example 1 except that the ethyl cellulose of Comparative Example 1 was changed to polyvinyl alcohol (molecular weight 50000).
Next, the prepared paste is applied to the surface of the p-type silicon substrate by screen printing to form a coating film, irradiated with ultraviolet rays of 0.06 J / cm ² from above the coating film, and then on a hot plate at 200 ° C. The coating was cured by drying for 10 minutes.
Subsequently, ethanol was applied to the coating film and dried in the atmosphere. As a result, the surface of the coating film became white and the area of the coating film was enlarged.
Subsequently, thermal diffusion treatment was performed for 10 minutes in an electric furnace set at 1000 ° C., and then the substrate was immersed in hydrofluoric acid for 5 minutes in order to remove the glass layer, and washed with running water. There was some deposit on the surface, but it could be easily removed by rubbing with a waste cloth. After washing with running water, it was dried in the air.
As a result, an n-type diffusion layer was formed over the entire enlarged region.

10 p-type semiconductor substrate 12 n-type diffusion layer 14 high-concentration electric field layer 16 antireflection film 18 surface electrode 20 back electrode (electrode layer)
30 Busbar electrode 32 Finger electrode

Claims (6)

  An n-type diffusion layer forming composition containing a glass powder containing a donor element and a curable resin.   Furthermore, the n type diffused layer formation composition of Claim 1 containing a thermosetting agent or a photocuring agent.   The n-type diffusion layer forming composition according to claim 1 or 2, wherein the donor element is at least one selected from P (phosphorus) and Sb (antimony). The glass powder containing the donor element includes at least one donor element-containing material selected from P ₂ O ₃ , P ₂ O ₅ and Sb ₂ O ₃ , SiO ₂ , K ₂ O, Na ₂ O, Li _2. And at least one glass component material selected from O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ and MoO _3. The n-type diffusion layer forming composition according to any one of claims 3 to 4. Applying the n-type diffusion layer forming composition according to any one of claims 1 to 4 on a semiconductor substrate;
Curing the curable resin;
A step of applying a thermal diffusion treatment;
The manufacturing method of the n type diffused layer which has this. Applying the n-type diffusion layer forming composition according to any one of claims 1 to 4 on a semiconductor substrate;
Curing the curable resin;
Performing a thermal diffusion treatment to form an n-type diffusion layer;
Forming an electrode on the formed n-type diffusion layer;
The manufacturing method of the solar cell element which has this.