JP5467697B2 - Manufacturing method of solar cell - Google Patents
Manufacturing method of solar cell Download PDFInfo
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- JP5467697B2 JP5467697B2 JP2012048340A JP2012048340A JP5467697B2 JP 5467697 B2 JP5467697 B2 JP 5467697B2 JP 2012048340 A JP2012048340 A JP 2012048340A JP 2012048340 A JP2012048340 A JP 2012048340A JP 5467697 B2 JP5467697 B2 JP 5467697B2
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- 238000004519 manufacturing process Methods 0.000 title claims description 20
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 129
- 229910052710 silicon Inorganic materials 0.000 claims description 129
- 239000010703 silicon Substances 0.000 claims description 129
- 239000000758 substrate Substances 0.000 claims description 128
- 229910021645 metal ion Inorganic materials 0.000 claims description 89
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 72
- 239000007864 aqueous solution Substances 0.000 claims description 62
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 38
- 238000005530 etching Methods 0.000 claims description 27
- 238000000034 method Methods 0.000 claims description 21
- 239000007800 oxidant agent Substances 0.000 claims description 11
- 238000007772 electroless plating Methods 0.000 claims description 10
- 238000007654 immersion Methods 0.000 claims description 8
- 238000006555 catalytic reaction Methods 0.000 claims description 6
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 5
- 229910017604 nitric acid Inorganic materials 0.000 claims description 5
- 239000000243 solution Substances 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims description 3
- 239000010410 layer Substances 0.000 description 37
- 150000002500 ions Chemical class 0.000 description 9
- 230000001590 oxidative effect Effects 0.000 description 7
- 238000001878 scanning electron micrograph Methods 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- 238000007747 plating Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 101710134784 Agnoprotein Proteins 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000003197 catalytic effect Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 3
- 229910052581 Si3N4 Inorganic materials 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000005229 chemical vapour deposition Methods 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- QOSATHPSBFQAML-UHFFFAOYSA-N hydrogen peroxide;hydrate Chemical compound O.OO QOSATHPSBFQAML-UHFFFAOYSA-N 0.000 description 2
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 2
- 230000033116 oxidation-reduction process Effects 0.000 description 2
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical class O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0236—Special surface textures
- H01L31/02363—Special surface textures of the semiconductor body itself, e.g. textured active layers
-
- 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
Description
本発明は、太陽電池の製造方法に関し、特にシリコン基板の表面に多孔質層を形成する方法に関するものである。 The present invention relates to a method for manufacturing a solar cell, and more particularly to a method for forming a porous layer on the surface of a silicon substrate.
石炭や石油などの代替エネルギーとして、クリーン、かつ無尽蔵なエネルギー源として太陽光が注目されており、当該太陽光の光エネルギーを電気エネルギーに変換する太陽電池の普及が一層期待されている。 As an alternative energy source such as coal and oil, sunlight is attracting attention as a clean and inexhaustible energy source, and the spread of solar cells that convert the light energy of the sunlight into electric energy is further expected.
太陽電池の表面には、太陽光を効果的に取り込む役割を有する微細な凹凸（以下、「テクスチャ」という。）が無数に形成されている。単結晶シリコンの場合、アルカリ液を用いてSi（100）面をエッチングすることにより、容易にピラミッド構造のテクスチャを得ることができる。一方、多結晶シリコンの場合は、シリコン基板表面に種々の結晶方位が出現しているため、単結晶シリコンのようにシリコン基板表面全体に均一なテクスチャを形成することは難しい。 Numerous fine irregularities (hereinafter referred to as “texture”) having a role of effectively taking sunlight are formed on the surface of the solar cell. In the case of single crystal silicon, the texture of the pyramid structure can be easily obtained by etching the Si (100) surface using an alkaline solution. On the other hand, in the case of polycrystalline silicon, since various crystal orientations appear on the surface of the silicon substrate, it is difficult to form a uniform texture on the entire surface of the silicon substrate like single crystal silicon.
多結晶シリコンからなるシリコン基板表面にテクスチャを形成する方法として、金属イオンを含有する、酸化剤とフッ化水素酸の混合水溶液に、シリコン基板を浸すことにより、シリコン基板の表面に多孔質層を形成する方法（例えば、特許文献１）が開示されている。また、金属イオンを含有する酸化剤とフッ化水素酸の混合水溶液にシリコン基板を浸漬して当該シリコン基板表面に多孔質層を形成する第一工程と、前記第一工程を経たシリコン基板表面をフッ化水素酸及び硝酸を主とした混酸に浸漬してエッチングしてテクスチャを形成する第二工程とを備える方法（例えば、特許文献２）が開示されている。 As a method of forming a texture on the surface of a silicon substrate made of polycrystalline silicon, a porous layer is formed on the surface of the silicon substrate by immersing the silicon substrate in a mixed aqueous solution of an oxidant and hydrofluoric acid containing metal ions. A forming method (for example, Patent Document 1) is disclosed. A first step of immersing the silicon substrate in a mixed aqueous solution of an oxidant containing metal ions and hydrofluoric acid to form a porous layer on the surface of the silicon substrate; and the silicon substrate surface that has undergone the first step. A method comprising a second step of forming a texture by dipping in a mixed acid mainly containing hydrofluoric acid and nitric acid is disclosed (for example, Patent Document 2).
上記特許文献２によると、上記特許文献１の方法により形成したテクスチャを有するシリコン基板は、反射率が低いもののシリコン基板表面が変色し、結果として太陽電池の特性が大幅に劣化するという問題がある。これに対し、上記特許文献２の方法では、上記特許文献１と同様の工程を経たシリコン基板表面をフッ化水素酸及び硝酸を主とした混酸に浸漬してエッチングしてテクスチャを形成することにより、反射率の低減効果を残したまま清浄なシリコン面が得られるとともに、孔の底の金属をも除去できるので、特性の高い太陽電池を製造することができるという効果が得られると、上記特許文献２に記載されている。 According to Patent Document 2, the silicon substrate having a texture formed by the method of Patent Document 1 has a problem that the surface of the silicon substrate is discolored although the reflectance is low, and as a result, the characteristics of the solar cell are greatly deteriorated. . On the other hand, in the method of Patent Document 2, the surface of the silicon substrate that has undergone the same process as in Patent Document 1 is immersed in a mixed acid mainly composed of hydrofluoric acid and nitric acid to form a texture. In addition, a clean silicon surface can be obtained while maintaining the effect of reducing the reflectance, and the metal at the bottom of the hole can be removed. It is described in Document 2.
しかしながら、上記特許文献１及び２では、いずれも金属イオンを含有する酸化剤とフッ化水素酸の混合水溶液にシリコン基板を浸すことにより、当該シリコン基板表面において金属イオンの付着とエッチングとが同時進行するので、金属イオンの付着量とエッチング量とを管理することが困難である。金属イオンの付着量のバラツキは、エッチングにより形成される孔の密度のバラツキの原因となる。また、エッチング量のバラツキは、エッチングにより形成される孔の大きさのバラツキの原因となる。金属イオンの付着量とエッチング量のバラツキは、シリコン基板表面全体において生じるだけでなく、同じ混合水溶液を使用した複数のシリコン基板間でも、混合水溶液の劣化により生じてしまう。したがって、金属イオンの付着量とエッチング量のバラツキが生じることにより、上記特許文献１及び２では、シリコン基板表面に大きさや密度が均一なテクスチャを形成することが困難であるという問題があった。 However, in both of Patent Documents 1 and 2, by immersing a silicon substrate in a mixed aqueous solution of an oxidant containing metal ions and hydrofluoric acid, adhesion of metal ions and etching proceed simultaneously on the silicon substrate surface. Therefore, it is difficult to manage the adhesion amount and etching amount of metal ions. The variation in the adhesion amount of metal ions causes variation in the density of holes formed by etching. Moreover, the variation in the etching amount causes the variation in the size of the hole formed by the etching. Variations in the adhesion amount and etching amount of metal ions not only occur on the entire surface of the silicon substrate, but also occur between a plurality of silicon substrates using the same mixed aqueous solution due to deterioration of the mixed aqueous solution. Therefore, due to variations in the amount of metal ions attached and the amount of etching, Patent Documents 1 and 2 have a problem that it is difficult to form a texture having a uniform size and density on the surface of the silicon substrate.
そこで、本発明は、シリコン基板表面にテクスチャをより均一に形成することができる太陽電池の製造方法を提供することを目的とする。 Then, an object of this invention is to provide the manufacturing method of the solar cell which can form a texture more uniformly in the silicon substrate surface.
本発明の請求項１に係る太陽電池の製造方法は、金属イオンを用いたエッチングによりシリコン基板の表面に多孔質層を形成する太陽電池の製造方法において、フッ化水素酸を含有する第１の水溶液に前記シリコン基板を浸漬し、前記シリコン基板表面の自然酸化膜を除去するステップと、前記金属イオンを含有し酸化剤とフッ化水素酸を含有しない第２の水溶液に、前記自然酸化膜を除去した前記シリコン基板を浸漬し、無電解めっきにより前記金属イオンを前記シリコン基板表面に付着させるステップと、フッ化水素酸と過酸化水素水とを含有する第３の水溶液に、前記金属イオンを表面に付着させた前記シリコン基板を浸漬し、前記金属イオンの触媒反応により前記シリコン基板表面に前記多孔質層を形成するステップとを備え、前記金属イオンを前記シリコン基板表面に付着させるステップにおいて、前記金属イオンの濃度を測定し、当該金属イオン濃度を一定に制御することを特徴とする。 The method for manufacturing a solar cell according to claim 1 of the present invention is the method for manufacturing a solar cell in which a porous layer is formed on the surface of a silicon substrate by etching using metal ions. The step of immersing the silicon substrate in an aqueous solution to remove a natural oxide film on the surface of the silicon substrate; and the step of removing the natural oxide film in a second aqueous solution containing the metal ions and not containing an oxidizing agent and hydrofluoric acid. The step of immersing the removed silicon substrate and attaching the metal ions to the surface of the silicon substrate by electroless plating; and the metal ions in a third aqueous solution containing hydrofluoric acid and hydrogen peroxide solution Immersing the silicon substrate attached to the surface, and forming the porous layer on the silicon substrate surface by catalytic reaction of the metal ions, In the step of adhering the genus ions into the silicon substrate surface, the concentration of the metal ions were measured, and controlling the metal ion concentration constant.
本発明の請求項１によれば、エッチングによる多孔質層の形成に先立ち、シリコン基板表面に金属イオンを付着させることとした。これにより金属イオンの付着とエッチングとを同時に行う従来に比べ、金属イオンをより均一にシリコン基板表面に付着させることができる。次いで、前記金属イオンの触媒反応により前記シリコン基板表面に多孔質層を形成することとした。これによりシリコン基板の浸漬時間及びフッ化水素酸と過酸化水素水の比率を制御することにより、触媒反応により形成される孔の大きさを制御することができる。したがってシリコン基板表面に、大きさや密度がより均一なテクスチャを形成することができる。さらに、第２の水溶液に含有される金属イオンの濃度をより確実に制御することにより、全体として金属イオンの付着量のバラツキを抑制することができる。 According to claim 1 of the present invention, metal ions are deposited on the surface of the silicon substrate prior to the formation of the porous layer by etching. As a result, the metal ions can be more uniformly attached to the surface of the silicon substrate than in the conventional case where the metal ions are attached and etched simultaneously. Next, a porous layer was formed on the surface of the silicon substrate by the catalytic reaction of the metal ions. Thus, the size of the holes formed by the catalytic reaction can be controlled by controlling the immersion time of the silicon substrate and the ratio of hydrofluoric acid and hydrogen peroxide solution. Therefore, a texture having a more uniform size and density can be formed on the surface of the silicon substrate. Furthermore, by more reliably controlling the concentration of the metal ions contained in the second aqueous solution, it is possible to suppress variations in the amount of metal ions attached as a whole.
以下、図面を参照して本発明に係る実施形態について詳細に説明する。図１に示す太陽電池１は、光電変換を行うシリコン基板２と、当該シリコン基板２表面をテクスチャ形状に加工した多孔質層３とを備え、多孔質層３が形成された受光面から入射した光をシリコン基板２において電気エネルギーに変換する。多孔質層３は、シリコン基板２表面に入射した光が透過・反射を繰り返し、その結果、平坦なシリコン基板表面に比べより多くの光をシリコン基板２内に導く。多孔質層３に形成された微細なテクスチャは、高さや密度が均一である方が不均一であるよりも入射した光を効率的に閉じ込められることが一般に知られている。なお、テクスチャの高さとは凹凸の高低差をいい、密度は単位面積当たりの凹または凸の数をいう。本実施形態に係る太陽電池１は、多孔質層３に微細なテクスチャが従来に比べ均一に形成されている点が特徴的であって、その他は従来と同じ構成である。 Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. A solar cell 1 shown in FIG. 1 includes a silicon substrate 2 that performs photoelectric conversion and a porous layer 3 in which the surface of the silicon substrate 2 is processed into a textured shape, and is incident from a light receiving surface on which the porous layer 3 is formed. Light is converted into electrical energy in the silicon substrate 2. In the porous layer 3, light incident on the surface of the silicon substrate 2 is repeatedly transmitted and reflected, and as a result, more light is guided into the silicon substrate 2 than on the flat silicon substrate surface. It is generally known that the fine texture formed in the porous layer 3 can efficiently confine incident light when the height and density are uniform rather than nonuniform. Note that the texture height refers to the difference in level of the unevenness, and the density refers to the number of concaves or convexes per unit area. The solar cell 1 according to the present embodiment is characterized in that a fine texture is uniformly formed in the porous layer 3 as compared with the conventional one, and the other configuration is the same as the conventional one.
実際上、太陽電池１は、図示しないが、ｐ型シリコン基板に対し、多孔質層３を形成する受光面側に拡散層、反射防止膜、グリッド電極が順に形成されており、裏面側に裏面電界層、裏面電極が順に形成されている。反射防止膜は、光の反射を抑制するために、多孔質層３の表面に形成されている。反射防止膜は、例えば、化学気相成長（CVD：Chemical Vapor Deposition）法などで形成される酸化チタン（TiO2）膜や窒化シリコン（SiN）膜の単層構造の膜で構成される。 Actually, although not shown, the solar cell 1 has a diffusion layer, an antireflection film, and a grid electrode sequentially formed on the light receiving surface side where the porous layer 3 is formed with respect to the p-type silicon substrate. An electric field layer and a back electrode are formed in this order. The antireflection film is formed on the surface of the porous layer 3 in order to suppress light reflection. The antireflection film is composed of, for example, a single layer structure of a titanium oxide (TiO 2 ) film or a silicon nitride (SiN) film formed by a chemical vapor deposition (CVD) method or the like.
次に多孔質層３の形成方法について図２を参照して説明する。以下の記載において、濃度は質量％である。 Next, a method for forming the porous layer 3 will be described with reference to FIG. In the following description, the concentration is mass%.
まず、ステップＳＰ１においてフッ化水素酸を含有する第１の水溶液に前記シリコン基板２を浸漬し、前記シリコン基板２表面の自然酸化膜を除去する。この場合の第１の水溶液の容量比はＨＦ（濃度５０％）：Ｈ２Ｏ＝４００ｍｌ〜５０００ｍｌ：１２００ｍｌ〜１５０００ｍｌであり、浸漬時間は６０秒〜３６０秒とすることができる。なお、第１の水溶液はシリコン基板２表面の自然酸化膜を除去することのみを目的としているため、金属イオンを含有しない。 First, in step SP1, the silicon substrate 2 is immersed in a first aqueous solution containing hydrofluoric acid, and the natural oxide film on the surface of the silicon substrate 2 is removed. The volume ratio of the first aqueous solution in this case is HF (concentration 50%): H 2 O = 400 ml to 5000 ml: 1200 ml to 15000 ml, and the immersion time can be 60 seconds to 360 seconds. Note that the first aqueous solution is intended only to remove the natural oxide film on the surface of the silicon substrate 2, and therefore does not contain metal ions.
次にステップＳＰ２において、金属イオンを含有する第２の水溶液に前記シリコン基板２を浸漬し、無電解めっきにより前記金属イオンを前記シリコン基板２表面に付着させる。金属イオンは、例えば、Ａｇイオンを適用することができる。金属イオンとしてＡｇイオンを適用する場合、金属イオン含有剤としてＡｇＮＯ３を用いて第２の水溶液を生成することができる。この場合の第２の水溶液の容量比は金属イオン含有剤（濃度１Ｅ-４Ｍ〜８Ｅ-４Ｍ）：Ｈ２Ｏ＝５．０ｍｌ〜１５ｍｌ：５０００ｍｌ〜１５０００ｍｌである。無電解めっきの条件は、例えば、浸漬時間を３００秒、第２の水溶液の温度を２６度とすることができる。無電解めっきは、第２の水溶液に含まれる金属イオンの濃度を測定し、当該金属イオン濃度を一定に制御しながら行う。金属イオンの濃度は、例えば、電気抵抗法で測定することができる。なお、第２の水溶液は金属イオンをシリコン基板２表面に付着させることのみを目的としており、シリコン基板２表面に多孔質層３を形成することは目的としていないため、酸化剤とフッ化水素酸を含有しない。 Next, in step SP2, the silicon substrate 2 is immersed in a second aqueous solution containing metal ions, and the metal ions are adhered to the surface of the silicon substrate 2 by electroless plating. As the metal ions, for example, Ag ions can be applied. When Ag ions are applied as the metal ions, the second aqueous solution can be generated using AgNO 3 as the metal ion-containing agent. The volume ratio of the second aqueous solution in this case is a metal ion-containing agent (concentration 1E-4M to 8E-4M): H 2 O = 5.0 ml to 15 ml: 5000 ml to 15000 ml. The electroless plating conditions can be, for example, an immersion time of 300 seconds and a temperature of the second aqueous solution of 26 degrees. The electroless plating is performed while measuring the concentration of metal ions contained in the second aqueous solution and controlling the metal ion concentration to be constant. The concentration of metal ions can be measured, for example, by an electric resistance method. Note that the second aqueous solution is only for attaching metal ions to the surface of the silicon substrate 2 and not for forming the porous layer 3 on the surface of the silicon substrate 2, so that the oxidizing agent and hydrofluoric acid are used. Does not contain.
本実施形態の場合、第２の水溶液は、金属イオンを含有するが酸化剤とフッ化水素酸を含有しないから金属イオン単体の濃度を測定することができる。したがって、本実施形態に係る製造方法は、金属イオンに加え酸化剤とフッ化水素酸とを含む水溶液を用いる従来に比べ、より容易に金属イオン濃度を測定することができる。このように第２の水溶液に含まれる金属イオン濃度を制御することにより、シリコン基板２表面に付着させる金属イオンの量をより確実に制御することができる。 In the case of this embodiment, since the second aqueous solution contains metal ions but does not contain an oxidizing agent and hydrofluoric acid, the concentration of metal ions alone can be measured. Therefore, the manufacturing method according to this embodiment can measure the metal ion concentration more easily than the conventional method using an aqueous solution containing an oxidizing agent and hydrofluoric acid in addition to metal ions. Thus, by controlling the metal ion concentration contained in the second aqueous solution, the amount of metal ions attached to the surface of the silicon substrate 2 can be controlled more reliably.
因みに、金属イオンを含有する酸化剤とフッ化水素酸の混合水溶液にシリコン基板を浸漬する従来の方法では、電気抵抗値が金属イオンと酸化剤とフッ化水素酸のそれぞれの抵抗値の和として計測され、金属イオンのみの抵抗値を直接計測することができないため、金属イオン単体の濃度を測定することが困難だった。 Incidentally, in the conventional method in which a silicon substrate is immersed in a mixed aqueous solution of an oxidant containing metal ions and hydrofluoric acid, the electrical resistance value is the sum of the resistance values of the metal ions, oxidant, and hydrofluoric acid. It was difficult to measure the concentration of a single metal ion because the resistance value of the metal ion alone could not be measured directly.
また、本実施形態の場合、無電解めっきは、第２の水溶液を流動しながら行うのが好ましい。例えば、第２の水溶液は、図示しないが、第２の水溶液を貯留した貯蔵タンクと、無電解めっきを行うめっき槽を２つの配管で連通し、ポンプで第２の水溶液を貯留タンクとめっき槽間を循環させてもよい（以下、「ポンプ循環器」ともいう）。また、第２の水溶液は、図示しないが、めっき槽内において、スターラーで撹拌することとしてもよい。このように本実施形態では、第２の水溶液を流動しながら無電解めっきを行うことにより、より確実に均一な密度で金属イオンをシリコン基板２表面に付着させることができる。 In the present embodiment, electroless plating is preferably performed while flowing the second aqueous solution. For example, the second aqueous solution is not shown, but a storage tank storing the second aqueous solution and a plating tank for performing electroless plating are connected by two pipes, and the second aqueous solution is connected to the storage tank and the plating tank by a pump. May be circulated (hereinafter also referred to as “pump circulator”). Further, the second aqueous solution may be stirred with a stirrer in the plating tank, although not shown. As described above, in this embodiment, by performing electroless plating while flowing the second aqueous solution, metal ions can be more reliably attached to the surface of the silicon substrate 2 with a uniform density.
次にステップＳＰ３において、フッ化水素酸と過酸化水素水を含有する第３の水溶液に前記シリコン基板２を浸漬する。シリコン基板２では、表面に付着した前記金属イオンの触媒作用による過酸化水素水の水素還元反応が進む。そうすると、電子消費量の増加分を補うため金属イオンに接するシリコン基板２表面から電子が引き抜かれる。この結果、シリコン基板２に正孔が生成され、シリコン基板の酸化的溶解を引き起こすことになる。このようにして前記シリコン基板２表面に孔が無数に形成され、孔（凹）と孔が形成されていない部分（凸）とで多孔質層３が形成される。この場合の第３の水溶液の容量比はＨＦ（濃度５０％）：Ｈ２Ｏ２（濃度３０％）：Ｈ２Ｏ＝４００ｍｌ〜４０００ｍｌ：４００ｍｌ〜２０００ｍｌ：１００００ｍｌ〜２００００ｍｌである。シリコン基板２の浸漬時間を制御することにより、多孔質層３を構成する孔の大きさを制御する。例えば、孔（凹）が大きいと、孔が形成されていない部分（凸）との高低差が大きくなるので、テクスチャの高さが大きくなる。なお、第３の水溶液は、エッチングによりシリコン基板２表面に多孔質層３を形成することのみを目的としており、シリコン基板２表面に金属イオンを付着させることを目的としていないため、金属イオンを含有しない。 Next, in step SP3, the silicon substrate 2 is immersed in a third aqueous solution containing hydrofluoric acid and hydrogen peroxide. In the silicon substrate 2, the hydrogen reduction reaction of hydrogen peroxide solution proceeds by the catalytic action of the metal ions attached to the surface. Then, electrons are drawn out from the surface of the silicon substrate 2 in contact with the metal ions in order to compensate for the increase in the amount of electron consumption. As a result, holes are generated in the silicon substrate 2 and cause oxidative dissolution of the silicon substrate. In this way, an infinite number of holes are formed on the surface of the silicon substrate 2, and the porous layer 3 is formed by the holes (concave) and the portions (convex) where no holes are formed. The volume ratio of the third aqueous solution in this case is HF (concentration 50%): H 2 O 2 (concentration 30%): H 2 O = 400 ml to 4000 ml: 400 ml to 2000 ml: 10000 ml to 20000 ml. By controlling the immersion time of the silicon substrate 2, the size of the pores constituting the porous layer 3 is controlled. For example, if the hole (concave) is large, the height difference from the portion (convex) where the hole is not formed becomes large, so that the height of the texture increases. The third aqueous solution contains metal ions only for the purpose of forming the porous layer 3 on the surface of the silicon substrate 2 by etching and not for attaching metal ions to the surface of the silicon substrate 2. do not do.
第３の水溶液における過酸化水素水の濃度は、より確実に多孔質層３を形成するため、金属イオンのエッチングを抑制しない程度の濃度に抑えることが好ましい。具体的には、過酸化水素水の濃度は、フッ化水素酸の濃度に対し、２５〜５０％であるのが好ましい。過酸化水素水は、金属イオンよりシリコン基板から電子を奪う力が強いので、過酸化水素水の濃度が５０％より高いと、金属イオンの触媒作用によるエッチング速度より過酸化水素水によるエッチング速度の方が早くなり、シリコン基板の表面全体が酸化されて鏡面になってしまい、多孔質層が形成されなくなってしまう。また、過酸化水素水は、フッ化水素酸に対する濃度が上記範囲外の場合、すなわちフッ化水素酸に対する濃度が５０％より高い場合、及びフッ化水素酸に対する濃度が２５％より小さい場合には、反射率を低下させることができない。 In order to form the porous layer 3 more reliably, the concentration of the hydrogen peroxide solution in the third aqueous solution is preferably suppressed to a concentration that does not suppress the etching of metal ions. Specifically, the concentration of the hydrogen peroxide solution is preferably 25 to 50% with respect to the concentration of hydrofluoric acid. Since the hydrogen peroxide solution has a stronger ability to take electrons from the silicon substrate than the metal ions, if the concentration of the hydrogen peroxide solution is higher than 50%, the etching rate by the hydrogen peroxide solution is higher than the etching rate by the catalytic action of the metal ions. As a result, the entire surface of the silicon substrate is oxidized and becomes a mirror surface, and the porous layer is not formed. Further, when the concentration with respect to hydrofluoric acid is outside the above range, that is, when the concentration with respect to hydrofluoric acid is higher than 50%, and when the concentration with respect to hydrofluoric acid is less than 25%, The reflectance cannot be reduced.
上記したように、本実施形態に係る太陽電池１の製造方法では、エッチングによる多孔質層３の形成に先立ち、金属イオンを含有する第２の水溶液にシリコン基板２を浸漬し、当該シリコン基板２表面に金属イオンを付着させることとした。これにより、金属イオンの付着とエッチングとを同時に行う従来に比べ、金属イオンを均一にシリコン基板２表面に付着させることができる。 As described above, in the method for manufacturing the solar cell 1 according to this embodiment, prior to the formation of the porous layer 3 by etching, the silicon substrate 2 is immersed in the second aqueous solution containing metal ions, and the silicon substrate 2 Metal ions were allowed to adhere to the surface. As a result, the metal ions can be uniformly attached to the surface of the silicon substrate 2 as compared with the conventional case where the metal ions are attached and etched simultaneously.
しかも、第２の水溶液は、金属イオンを含有するが、従来のように酸化剤とフッ化水素酸とを含まないので、金属イオンの濃度をより容易に測定することができる。したがって、本実施形態では、第２の水溶液に含有される金属イオンの濃度をより確実に制御することにより、一つのシリコン基板２表面内に金属イオンを均一に付着させることができるとともに、同じ第２の水溶液を複数のシリコン基板２に用いた場合でも複数のシリコン基板２の表面に均一に金属イオンを付着させることができるので、全体として金属イオンの付着量のバラツキを抑制することができる。 Moreover, although the second aqueous solution contains metal ions, it does not contain oxidant and hydrofluoric acid as in the prior art, so that the concentration of metal ions can be measured more easily. Therefore, in this embodiment, by controlling the concentration of the metal ions contained in the second aqueous solution more reliably, the metal ions can be uniformly attached to the surface of one silicon substrate 2 and the same first Even when the aqueous solution of 2 is used for the plurality of silicon substrates 2, the metal ions can be uniformly attached to the surfaces of the plurality of silicon substrates 2, so that variation in the adhesion amount of the metal ions can be suppressed as a whole.
さらに、本実施形態では、シリコン基板２表面に金属イオンを付着させた後、フッ化水素酸と過酸化水素水を含有する第３の水溶液に前記シリコン基板２を浸漬し、前記金属イオンの触媒反応により前記シリコン基板２表面に多孔質層３を形成することとした。このように、シリコン基板２の浸漬時間及びフッ化水素酸と過酸化水素水の比率を制御することにより、触媒反応により形成される孔の大きさを制御することができる。したがって、本実施形態では、シリコン基板２表面により均一な高さのテクスチャを形成することができる。 Further, in the present embodiment, after the metal ions are attached to the surface of the silicon substrate 2, the silicon substrate 2 is immersed in a third aqueous solution containing hydrofluoric acid and hydrogen peroxide solution, and the catalyst for the metal ions is obtained. The porous layer 3 was formed on the surface of the silicon substrate 2 by the reaction. In this way, by controlling the immersion time of the silicon substrate 2 and the ratio of hydrofluoric acid and hydrogen peroxide solution, the size of the holes formed by the catalytic reaction can be controlled. Therefore, in the present embodiment, a texture having a uniform height can be formed on the surface of the silicon substrate 2.
金属イオンをシリコン基板２表面に付着させた後、フッ化水素酸と過酸化水素水の濃度を管理した第３の水溶液に前記シリコン基板２を所定時間浸漬し、シリコン基板２表面に多孔質層３を形成することとしたから、シリコン基板２表面にテクスチャをより均一に形成することができる。 After attaching metal ions to the surface of the silicon substrate 2, the silicon substrate 2 is immersed in a third aqueous solution in which the concentrations of hydrofluoric acid and hydrogen peroxide are controlled, and a porous layer is formed on the surface of the silicon substrate 2. 3 is formed, the texture can be more uniformly formed on the surface of the silicon substrate 2.
多孔質層３を形成する第３の水溶液は、シリコン基板２の加工数に比例して劣化するので交換する必要があるが、本実施形態の場合、第３の水溶液が金属イオンを含有する第２の水溶液と別体であるから、従来のように金属イオンを廃棄する必要がないので、水溶液の管理を簡略化することができる。 The third aqueous solution that forms the porous layer 3 deteriorates in proportion to the number of processed silicon substrates 2 and needs to be replaced. In the present embodiment, the third aqueous solution contains metal ions. Since it is separate from the aqueous solution 2, there is no need to discard metal ions as in the prior art, so that the management of the aqueous solution can be simplified.
なお、上記ステップＳＰ３の後に下記のステップを追加することとしてもよい。すなわち、ステップＳＰ４において、水洗浄をし、ステップＳＰ５でフッ化水素酸と硝酸とを含有する第４の水溶液に前記シリコン基板２を浸漬し、エッチングする。これにより、本実施形態では、金属イオンを除去するという効果を得ることができる。この場合、第４の水溶液の容量比は、ＨＦ（濃度５０％）：ＨＮＯ３（濃度６９％）：Ｈ２Ｏ＝１００ｍｌ〜５００ｍｌ：６００ｍｌ〜３０００ｍｌ：１００００ｍｌ〜５００００ｍｌである。浸漬時間は、２４０秒〜３６０秒とすることができる。 The following steps may be added after step SP3. That is, in step SP4, water cleaning is performed, and in step SP5, the silicon substrate 2 is immersed in a fourth aqueous solution containing hydrofluoric acid and nitric acid and etched. Thereby, in this embodiment, the effect of removing a metal ion can be acquired. In this case, the volume ratio of the fourth aqueous solution is HF (concentration 50%): HNO 3 (concentration 69%): H 2 O = 100 ml to 500 ml: 600 ml to 3000 ml: 10000 ml to 50000 ml. The immersion time can be 240 seconds to 360 seconds.
次にステップＳＰ６において、水洗浄をし、次いでアルカリ薬液に前記シリコン基板２を浸漬し、ステイン膜を除去する（ステップＳＰ７）。ステイン膜とは、エッチングによりシリコン基板２表面に形成される黒褐色の膜をいう。最後に水洗浄することにより、本実施形態に係る多孔質層３を備えたシリコン基板２を得ることができる（ステップＳＰ８）。 Next, in step SP6, water washing is performed, and then the silicon substrate 2 is immersed in an alkaline chemical solution to remove the stain film (step SP7). The stain film is a black-brown film formed on the surface of the silicon substrate 2 by etching. Finally, the silicon substrate 2 provided with the porous layer 3 according to the present embodiment can be obtained by washing with water (step SP8).
次に、上記実施形態に係る太陽電池１の製造方法の実施例について説明する。本実施例ではシリコン基板２にｐ型シリコン基板を用いた。容量比をＨＦ（濃度５０％）：Ｈ２Ｏ＝１２００ｍｌ：１００００ｍｌに調整した第１の水溶液にシリコン基板２を３００秒浸漬し、自然酸化膜を除去した。次いで、容量比をＡｇＮＯ３（濃度３Ｅ-４Ｍ）：Ｈ２Ｏ＝３ｍｌ：１００００ｍｌに調整した第２の水溶液に前記シリコン基板２を立てた状態で浸漬し、無電解めっきにより前記金属イオンを前記シリコン基板２表面に付着させた。この場合のめっき条件は、浸漬時間を３００秒、第２の水溶液の温度を２６度とした。また、ポンプ循環器によりシリコン基板２の周囲を第２の水溶液が流動するようにした。なお、金属イオンの濃度は、溶液の抵抗を測定する抵抗測定装置により測定した。 Next, examples of the method for manufacturing the solar cell 1 according to the above embodiment will be described. In this embodiment, a p-type silicon substrate is used as the silicon substrate 2. The silicon substrate 2 was immersed in a first aqueous solution whose volume ratio was adjusted to HF (concentration 50%): H 2 O = 1200 ml: 10000 ml for 300 seconds to remove the natural oxide film. Next, the silicon substrate 2 is immersed in a second aqueous solution in which the volume ratio is adjusted to AgNO 3 (concentration 3E-4M): H 2 O = 3 ml: 10000 ml, and the metal ions are introduced by electroless plating. It was made to adhere to the silicon substrate 2 surface. The plating conditions in this case were an immersion time of 300 seconds and a temperature of the second aqueous solution of 26 degrees. Further, the second aqueous solution was allowed to flow around the silicon substrate 2 by the pump circulator. The metal ion concentration was measured with a resistance measuring device that measures the resistance of the solution.
このようにして金属イオンを付着させたシリコン基板表面２ＡのＳＥＭ（Scanning Electron Microscope）画像を図３に示す。本図から明らかなように、本実施形態に係る太陽電池１の製造方法によれば、金属イオン４をシリコン基板表面２Ａにより均一に付着させることができる。 FIG. 3 shows an SEM (Scanning Electron Microscope) image of the silicon substrate surface 2A to which metal ions are attached in this manner. As is clear from this figure, according to the method for manufacturing the solar cell 1 according to the present embodiment, the metal ions 4 can be uniformly attached to the silicon substrate surface 2A.
次いで、フッ化水素酸と過酸化水素水の容量比をＨＦ（濃度５０％）：Ｈ２Ｏ２（濃度３０％）：Ｈ２Ｏ＝１２００ｍｌ：８００ｍｌ：１００００ｍｌに調整した第３の水溶液に前記シリコン基板２を浸漬し、前記金属イオンの触媒反応により前記シリコン基板２表面に多孔質層３を形成した。このようにして多孔質層３が形成されたシリコン基板２表面のＳＥＭ画像を図４に示す。本図から明らかなように、本実施例に係る太陽電池１の製造方法によれば、シリコン基板２表面にテクスチャをより均一に形成することができる。 Next, the third aqueous solution in which the volume ratio of hydrofluoric acid and hydrogen peroxide water was adjusted to HF (concentration 50%): H 2 O 2 (concentration 30%): H 2 O = 1200 ml: 800 ml: 10000 ml was added to the third aqueous solution. The silicon substrate 2 was immersed, and the porous layer 3 was formed on the surface of the silicon substrate 2 by the catalytic reaction of the metal ions. An SEM image of the surface of the silicon substrate 2 on which the porous layer 3 is thus formed is shown in FIG. As is clear from this figure, according to the method for manufacturing the solar cell 1 according to this example, the texture can be more uniformly formed on the surface of the silicon substrate 2.
次いで、フッ化水素酸と硝酸の容量比を、ＨＦ（濃度５０％）：ＨＮＯ３（濃度６９％）：Ｈ２Ｏ＝４００ｍｌ：３０００ｍｌ：６０００ｍｌに調整した第４の水溶液に多孔質層を形成したシリコン基板２を浸漬し、エッチングした。このようにしてエッチングされたシリコン基板２表面のＳＥＭ画像を図５に示す。本図からも明らかなように、本実施例に係る太陽電池１の製造方法によれば、シリコン基板２表面にテクスチャをより均一に形成することができる。 Next, a porous layer is formed in a fourth aqueous solution in which the volume ratio of hydrofluoric acid and nitric acid is adjusted to HF (concentration 50%): HNO 3 (concentration 69%): H 2 O = 400 ml: 3000 ml: 6000 ml The silicon substrate 2 was immersed and etched. An SEM image of the surface of the silicon substrate 2 thus etched is shown in FIG. As is clear from this figure, according to the method for manufacturing the solar cell 1 according to this example, the texture can be more uniformly formed on the surface of the silicon substrate 2.
上記実施例に対し、金属イオンの付着とエッチングとを同時に行った比較例を作製した。本比較例は、シリコン基板としてｐ型多結晶シリコンウェハ（ボロンドープ、１〜３Ωｃｍ、１５×１５ｃｍ角、厚さ２８０μｍ）を用意し、シリコン基板表面のダメージ層をアルカリで除去した。その後、ＨＦ（濃度５０％）：Ｈ２Ｏ２（濃度３０％）：Ｈ２Ｏ：ＡｇＮＯ３（０．１Ｍ）＝４００ｍｌ：２００ｍｌ：１６００ｍｌ：４．４ｍｌ（［Ａｇ＋］＝２Ｅ−４Ｍ）の薬液が入った槽に、シリコン基板を立てた状態で、３分間エッチングを行った。その後、前記シリコン基板の水洗、乾燥を経て、ＨＦ（濃度５０％）：ＨＮＯ３（濃度６９％）：Ｈ２Ｏ：＝１：９：１５という容量比の混酸で３分間エッチングを行った。このように作製された比較例のＳＥＭ画像を図６に示す。本図から明らかなように、本比較例によれば、ナノサイズの四角い穴１０が多数形成されており、テクスチャの大きさにバラツキが大きいことが確認できた。 A comparative example in which metal ions were attached and etched at the same time as the above example was prepared. In this comparative example, a p-type polycrystalline silicon wafer (boron-doped, 1 to 3 Ωcm, 15 × 15 cm square, thickness 280 μm) was prepared as a silicon substrate, and the damaged layer on the silicon substrate surface was removed with an alkali. Then, HF (concentration 50%): H 2 O 2 (concentration 30%): H 2 O: AgNO 3 (0.1M) = 400 ml: 200 ml: 1600 ml: 4.4 ml ([Ag + ] = 2E-4M) Etching was performed for 3 minutes in a state where the silicon substrate was placed in a tank containing the chemical solution. Then, the silicon substrate was washed with water and dried, and then etched for 3 minutes with a mixed acid having a volume ratio of HF (concentration 50%): HNO 3 (concentration 69%): H 2 O: = 1: 9: 15. The SEM image of the comparative example produced in this way is shown in FIG. As is clear from this figure, according to this comparative example, a large number of nano-sized square holes 10 were formed, and it was confirmed that the size of the texture varied greatly.
次に、第３の水溶液における過酸化水素水の濃度が多孔質層の形成に及ぼす影響を調べた。容量比がＨＦ（濃度５０％）：Ｈ２Ｏ＝４００ｍｌ：８０００ｍｌであるフッ化水素酸の水溶液に対し、過酸化水素水（濃度５０％）を、０ｍｌ、１００ｍｌ、２００ｍｌ、３００ｍｌ、４００ｍｌ、５００ｍｌ添加した６種類の第３の水溶液を生成した。前記第３の水溶液に、それぞれ金属イオンを表面に付着させたシリコン基板を１０分間浸漬し、エッチングを行った。エッチング後のシリコン基板表面を確認した。その結果、図７に示すように、過酸化水素水の添加量が多いほど、シリコン基板表面が鏡面になることが分かった。 Next, the influence of the concentration of the hydrogen peroxide solution in the third aqueous solution on the formation of the porous layer was examined. Hydrogen peroxide solution (concentration 50%) is 0 ml, 100 ml, 200 ml, 300 ml, 400 ml, 500 ml with respect to an aqueous solution of hydrofluoric acid having a volume ratio of HF (concentration 50%): H 2 O = 400 ml: 8000 ml. Six types of added third aqueous solutions were produced. Etching was performed by immersing a silicon substrate with metal ions attached to the surface in the third aqueous solution for 10 minutes. The surface of the silicon substrate after etching was confirmed. As a result, as shown in FIG. 7, it was found that the greater the amount of hydrogen peroxide added, the more specular the silicon substrate surface.
過酸化水素水の酸化還元電位は１．７８（Ｖ ｖｓ．ＮＨＥ）であり、金属イオン（例えばＡｇイオンの酸化還元電位は０．８０（Ｖ ｖｓ．ＮＨＥ））に比べ高い。すなわち、過酸化水素水は、金属イオンよりシリコン基板から電子を奪う力が強い、といえる。このため、過酸化水素水の濃度が高いと、金属イオンの触媒作用によるエッチング速度より過酸化水素水によるエッチング速度の方が早くなり、シリコン基板の表面全体が酸化されて鏡面になると考えられる。 The oxidation-reduction potential of hydrogen peroxide water is 1.78 (V vs. NHE), which is higher than that of metal ions (for example, the oxidation-reduction potential of Ag ions is 0.80 (V vs. NHE)). That is, it can be said that the hydrogen peroxide solution has a stronger ability to take electrons from the silicon substrate than the metal ions. For this reason, it is considered that when the concentration of the hydrogen peroxide solution is high, the etching rate by the hydrogen peroxide solution is faster than the etching rate by the catalytic action of metal ions, and the entire surface of the silicon substrate is oxidized to become a mirror surface.
本実施例の結果から、過酸化水素水の添加量が３００ｍｌ以上のとき（図７Ｄ）、シリコン基板表面２０Ｄが鏡面になることが確認された。一方、過酸化水素水の添加量が１００ｍｌ（図７Ｂ）、２００ｍｌ（図７Ｃ）のとき、シリコン基板表面２０Ｂ、２０Ｃがステインで茶褐色になった。これは、金属イオンによるエッチングが促進されたことを示している。また、過酸化水素水を添加しなかった場合（図７Ａ）、シリコン基板表面２０Ａは薄いステインで白濁色になった。 From the results of this example, it was confirmed that the surface 20D of the silicon substrate was a mirror surface when the amount of hydrogen peroxide added was 300 ml or more (FIG. 7D). On the other hand, when the amount of hydrogen peroxide added was 100 ml (FIG. 7B) and 200 ml (FIG. 7C), the silicon substrate surfaces 20B and 20C were stained brown. This indicates that etching by metal ions is promoted. Further, when the hydrogen peroxide solution was not added (FIG. 7A), the silicon substrate surface 20A became a cloudy color with a thin stain.
次に、エッチング後のシリコン基板に８００ｎｍの光を照射した際の反射率を測定した。その結果を図８に示す。本図から、過酸化水素水の添加量を１００ｍｌ、２００ｍｌとすることにより、反射率が低下することが確認できた。したがって、過酸化水素水の添加量を１００ｍｌ、２００ｍｌとした第３の水溶液によりエッチングを行ったシリコン基板を太陽電池に適用することにより、光の反射によるロスを低減でき、光の変換効率の向上が期待できる。 Next, the reflectance when the silicon substrate after etching was irradiated with light of 800 nm was measured. The result is shown in FIG. From this figure, it was confirmed that the reflectance was lowered when the amount of hydrogen peroxide solution added was 100 ml and 200 ml. Therefore, by applying a silicon substrate etched with a third aqueous solution in which the amount of hydrogen peroxide added is 100 ml and 200 ml to a solar cell, loss due to light reflection can be reduced and light conversion efficiency can be improved. Can be expected.
このことから、過酸化水素水は、添加量を１００ｍｌより多く、２００ｍｌ以下、すなわち、過酸化水素水の濃度がフッ化水素酸の濃度に対し２５％以上５０％以下とすることにより、多孔質層を形成できることが確認された。 Therefore, the hydrogen peroxide solution is added in an amount of more than 100 ml and 200 ml or less, that is, the concentration of the hydrogen peroxide solution is 25% or more and 50% or less with respect to the concentration of hydrofluoric acid. It was confirmed that a layer could be formed.
（変形例）
本発明は上記実施形態に限定されるものではなく、本発明の趣旨の範囲内で適宜変更することが可能である。
例えば、上記実施形態では金属イオンとしてＡｇイオンを適用した場合について説明したが、本発明はこれに限らず、Ａｕイオン、Ｃｕイオン、Ｐｔイオン、Ｐｄイオンなどを適用することができる。
(Modification)
The present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the gist of the present invention.
For example, although the case where Ag ions are applied as metal ions has been described in the above embodiment, the present invention is not limited to this, and Au ions, Cu ions, Pt ions, Pd ions, and the like can be applied.
１ 太陽電池
２ シリコン基板
３ 多孔質層
DESCRIPTION OF SYMBOLS 1 Solar cell 2 Silicon substrate 3 Porous layer
Claims (6)
フッ化水素酸を含有する第１の水溶液に前記シリコン基板を浸漬し、前記シリコン基板表面の自然酸化膜を除去するステップと、
前記金属イオンを含有し酸化剤とフッ化水素酸を含有しない第２の水溶液に、前記自然酸化膜を除去した前記シリコン基板を浸漬し、無電解めっきにより前記金属イオンを前記シリコン基板表面に付着させるステップと、
フッ化水素酸と過酸化水素水とを含有する第３の水溶液に、前記金属イオンを表面に付着させた前記シリコン基板を浸漬し、前記金属イオンの触媒反応により前記シリコン基板表面に前記多孔質層を形成するステップと
を備え、
前記金属イオンを前記シリコン基板表面に付着させるステップにおいて、前記金属イオンの濃度を測定し、当該金属イオン濃度を一定に制御することを特徴とする太陽電池の製造方法。 In a method for manufacturing a solar cell in which a porous layer is formed on the surface of a silicon substrate by etching using metal ions,
Immersing the silicon substrate in a first aqueous solution containing hydrofluoric acid to remove a natural oxide film on the surface of the silicon substrate;
The silicon substrate from which the natural oxide film has been removed is immersed in a second aqueous solution containing the metal ions but not containing an oxidizing agent and hydrofluoric acid, and the metal ions are attached to the silicon substrate surface by electroless plating. Step to
The silicon substrate having the metal ions attached to the surface thereof is immersed in a third aqueous solution containing hydrofluoric acid and hydrogen peroxide, and the porous surface is formed on the silicon substrate surface by a catalytic reaction of the metal ions. Forming a layer,
In the step of attaching the metal ions to the surface of the silicon substrate, the concentration of the metal ions is measured and the concentration of the metal ions is controlled to be constant.
前記シリコン基板の浸漬時間、及び
前記フッ化水素酸と前記過酸化水素水の比率
を制御することにより、前記多孔質層を構成する孔の大きさを制御することを特徴とする請求項１〜４のうちいずれか１項に記載の太陽電池の製造方法。 In the step of forming the porous layer on the silicon substrate surface,
The size of the holes constituting the porous layer is controlled by controlling the immersion time of the silicon substrate and the ratio of the hydrofluoric acid and the hydrogen peroxide solution. The method for manufacturing a solar cell according to any one of 4.
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| CN103219428B (en) * | 2013-04-12 | 2015-08-19 | 苏州大学 | Suede structure of a kind of crystal silicon solar energy battery and preparation method thereof |
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