JP4185332B2 - Solar cell and solar cell module using the same - Google Patents

Description

【００３８】
表１において、セル化後の良品率とは、同一条件で１００セルを作製した時の歩留まりである。セル化後の良品率については、実施例１及び比較例１〜３での特段の有為差はない。これら良品セルを用いて、実施例１及び比較例１〜３についてそれぞれ１０台の太陽電池モジュールを作製した後、各モジュール全体に照射強度１００ｍＷ／ｃｍ²で疑似太陽光を照射した状態で負極端子、正極端子（図２参照）を用いてモジュールの発電効率を測定した。表１において、モジュールの良品率とは、モジュールに封入したセルの特性に対応したモジュール特性が得られた率である。
【００３９】
実施例１と比較例１は、本発明のセル構造を用いた。また、比較例２と比較例３は従来セル構造を用いた。基板厚さについては、実施例１と比較例２では薄い基板、比較例１と比較例３では厚い基板でセル化されている。セル化後の良品率については、概ね９０％以上が得られたものの、直列結線して、モジュール化された時の良品率は２０〜１００％と明確な差のあることが明らかになった。つまり、従来セル構造で薄型基板を用いて従来法結線（セル当たり２個所の幅２ｍｍの銅結線）の時には、モジュール化により殆どのセルが破損したと言える（比較例２）。しかし実施例１（本発明）のセル構造を薄型基板にしても、モジュール歩留まりは９０％と高く、比較例３の従来セル、モジュールにほぼ近い値となった。
【００４０】
次に、実施の形態１のセル構造の太陽電池セルであって、その受光面電極部における電気的接続個所の数が異なるものを製作し、各太陽電池セルについての電極盛上がり厚さを測定し、その結果を表２に示した。なお、この電極盛上がり厚さとは、図４に示すように、シリコン基板（半導体基板１１）の表面から分離電極の接続上部までの厚さＴである。
【００４１】
【表２】

【００４２】
表２より、接続個所が５個所以上であれば電極盛上がり厚さが４９０μｍ以下に減少していることが分かる。なお、接続個所が４個所では電極盛上がり厚さが従来と同じ程度で、基板厚さは低減できず従来と同等の基板厚さにしかならず、他方、接続個所が１０００個所を越えると盛上がり厚さを減少できるが、結線に要する時間が膨大になることから製造効率が低下しメリットがない。
【００４３】
次に、実施の形態１のセル構造の太陽電池セル、すなわち受光面電極部の各受光面分離電極のピッチと裏面電極部の各裏面分離電極のピッチとが１：１であり、かつその受光面側接合層（ｎ+層）のシート抵抗率が１００Ω／□であって、上記ピッチが異なる複数の太陽電池セルを製作し、照射強度１００ｍＷ／ｃｍ²で疑似太陽光を照射した状態で各太陽電池セルについてセル光電変換効率を測定し、その結果を表３に示した。なお、シート抵抗値の測定は、一般の半導体分野で用いられる４探針測定器を用いて行った。
【００４４】
【表３】

【００４５】
表３より、受光面電極部の各受光面分離電極のピッチが２ｍｍのときでセル光電変換効率が２０％と最も高く、次いでピッチ１ｍｍ、３ｍｍ、４ｍｍ、０．５ｍｍ、５ｍｍの順で光電変換効率が１８〜１４％と高い値を示すことが分かる。なお、ピッチが０．５ｍｍ未満では、受光面電極部の総面積が大きくなり過ぎてその分光入射面積が減少し、セル光電変換効率が激減し、ピッチが５ｍｍを越えると、受光面側接合層内を電流が移動して電極に到達する際、抵抗成分が大きくなり過ぎ、セル内部の抵抗発熱で消耗され、光電変換効率が激減する。
【００４６】
次に、実施の形態１の電極パターンの太陽電池セルであって、受光面電極部の各受光面分離電極のピッチに対する裏面電極部の各裏面分離電極のピッチの比率が異なる複数の太陽電池セルを製作し、各太陽電池セルについて受光面結線故障率を測定すると共に、照射強度１００ｍＷ／ｃｍ²で疑似太陽光を照射した状態でセル光電変換効率を測定し、その結果を表４に示した。
【００４７】
【表４】

【００４８】
表４より、上記比率が１：１の場合に受光面結線故障率が０．２％と最も低く、かつセル光電変換効率も１５％と高く、比率１：１を中心に比率１：３〜３：１の範囲では受光面結線故障率が０．２〜１．４％と低く、かつセル光電変換効率が１５〜１３％と高いことが分かる。なお、比率１：３〜３：１の範囲外において、受光面分離電極ピッチに対する裏面分離電極ピッチが大きいと、受光面電極部の受光面分離電極数の増加に伴う電気的接続個所の増加により受光面結線故障率が激増し、受光面分離電極ピッチに対する裏面分離電極ピッチが小さいと、セル光電変換効率が低下して満足のいく数値が得られない。
【００４９】
次に、実施の形態１の電極パターンの太陽電池セルであって、受光面接合層のシート抵抗値が異なり、かつ受光面電極部の各受光面分離電極のピッチが異なる複数の太陽電池セルを製作し、照射強度１００ｍＷ／ｃｍ²で疑似太陽光を照射した状態で各太陽電池セルについて短絡電流密度（ｍＡ／ｃｍ²）を測定し、その結果を表５に示した。
【００５０】
【表５】

【００５１】
表５より、上記シート抵抗値が２００Ω／□で、かつ受光面分離電極ピッチが１ｍｍの場合に短絡電流密度が３７ｍＡ／ｃｍ²と最も高く、シート抵抗値が８０〜２５０Ω／□で、かつ受光面分離電極ピッチが１〜２ｍｍの範囲では短絡電流密度が３７〜３２ｍＡ／ｃｍ²と高いことが分かる。なお、シート抵抗値が８０〜２５０Ω／□の範囲を逸脱しても、受光面分離電極ピッチが１〜２ｍｍの範囲を逸脱しても、短絡電流密度が低下して満足のいく数値を得ることができない。
【００５２】
【発明の効果】
本発明によれば、受光面となる片方表面の電極（受光面電極部）を分離形成することによって、太陽電池セル同士を電気的に直列に接続して太陽電池モジュールを製作する過程において、一の太陽電池セルの受光面電極部の各受光面分離電極と、隣接する他の太陽電池セルの裏面電極部（全面電極）とを電気的に接続する際の受光面側の応力集中を回避することができ、太陽電池セルの割れを低減することができると共に、裏面電極部の全面電極による裏面電界（buck surface field）効果も得ることができ、高いセル光電変換効率が得られる。
さらに、受光面電極部と同様に、裏面電極部も複数本の裏面分離電極から構成することによって、受光面側では応力集中回避など同様の効果を奏した上で、表裏電極に起因する半導体基板への機械応力を大幅に低減することができ、それによって１００μｍ以下の薄い半導体基板で大面積の太陽電池セルを製作することが可能となる。
したがって、本発明によれば、半導体基板の薄型大面積化による割れを大幅に低減し、より一層低コスト化を図り得る太陽電池セル及びそれを用いた太陽電池モジュールを提供することができる。
【図面の簡単な説明】
【図１】 本発明の実施の形態１に係る太陽電池セルの斜視図である。
【図２】 同実施の形態における太陽電池セルを用いた太陽電池モジュールの概略構成図である。
【図３】 同実施の形態における太陽電池モジュールの要部拡大断面図である。
【図４】 同実施の形態における太陽電池モジュールの要部拡大断面図であって、隣接する太陽電池セル同士を銅線にて電気的に接続した状態を示す。
【図５】 本発明の実施の形態２に係る太陽電池セルの電極パターン及びセル同士の結線状態を示す説明図である。
【図６】 本発明の実施の形態３に係る太陽電池セルの平面図である。
【図７】 本発明の実施の形態４に係る太陽電池セルの平面図である。
【図８】 本発明の他の実施の形態に係る太陽電池セルの平面図である。
【図９】 従来の太陽電池セルの斜視図である。
【符号の説明】
１１ 半導体基板
１２、２２、３２、４２ 受光面電極部
１３、２３ 裏面電極部
１０、２０、３０、４０ 太陽電池セル
１２ａ、２２ａ、３２ａ、４２ａ 受光面分離電極
１３ａ、２３ａ 裏面分離電極
Ｐ_12a、Ｐ_22a 所定ピッチ
Ｐ_13a、Ｐ_23a 所定ピッチ
１１ｂ 受光面側半導体層
Ｓ 電気的接続個所[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a solar battery cell and a solar battery module using the same, and particularly to an electrode structure that can be made thinner.
[0002]
[Prior art]
  Usually, a solar cell 100 having a pn junction using a single crystal silicon or a polycrystalline silicon substrate has a concavo-convex shape chemically processed on the light receiving surface side with respect to a p-type silicon substrate 101 as shown in FIG. Thereafter, an n-type layer 102 is formed by a thermal diffusion method, and a p + high concentration layer 103 is formed on the back side by aluminum element diffusion or the like (for example, see Patent Document 1). An antireflection film 104 is also formed on the surface of the n-type layer 102. The light receiving surface electrode 105 on the light receiving surface side is formed by a conductive paste printing method. At this time, as the shape of the light receiving surface electrode 105, a silicon surface on the light receiving surface is formed using a pattern in which a thin line portion (hereinafter referred to as a grid electrode 105a) and a thick line portion (hereinafter referred to as a main grid electrode 105b) are combined. The idea is to make it as wide as possible. On the other hand, the back-side electrode 106 is formed by printing and baking a material mainly composed of aluminum over substantially the entire surface. When manufacturing a solar cell module from the plurality of solar cells 100 thus manufactured, the main grid electrode on the light receiving surface side of one solar cell, and the back surface side electrode of another adjacent solar cell, In the state where the wiring material such as a copper ribbon is electrically connected with solder and the cells are connected in series of 10 or more in this way, the glass plate is bonded to one side of the glass plate through a transparent resin, and the moisture-proof film or module is connected. An electrode terminal or the like is provided.
[0003]
  In the conventional solar cell and the solar cell module using the conventional solar cell, the shape of the silicon substrate itself is increased to, for example, 15 cm square from the recent trend toward lower cost production, and the current per cell at the time of power generation by sunlight Is in the state of taking out a large current of about 8 A (ampere). On the main grid having a width of 2 to 3 mm for collecting a large current, a device for preventing a current loss as much as possible by stacking copper wiring materials is devised. At the same time as increasing the area of the substrate, the thickness of the substrate has been reduced to about 0.3 mm despite the fragility of the silicon substrate due to the need to reduce the silicon material.
[0004]
  In addition, as an integrated type solar cell module that does not use a silicon substrate, there is one that affixes a member for series connection instead of a main grid (see, for example, Patent Document 2).
[0005]
[Patent Document 1]
JP 2002-222773 A
[Patent Document 2]
Japanese Patent Laid-Open No. 10-51018 (page 4, FIGS. 1 and 2)
[0006]
[Problems to be solved by the invention]
  However, in the former (for example, Patent Document 1), if the cell thickness is further reduced in order to further reduce the cost, the failure rate of the cell itself is rapidly increased mainly in the process of configuring the module. The cost reduction by introducing a thin substrate has reached its limit.
  When the cause of this cell crack was investigated, a thick metal with a different thermal expansion coefficient from that of silicon was formed at the electrode part on the light-receiving surface side of the silicon substrate, particularly at the main grid electrode, which is the current collection part, and the current extraction part. Moreover, excessive mechanical stress is applied to the silicon substrate by the copper ribbon connection for the cell series wiring in this extraction portion. On the other hand, for the electrode formed on almost the entire back surface, when a paste material mainly composed of powdered aluminum is printed and fired, it is alloyed with silicon to form an electrode layer, but the entire silicon is warped. Arise. This can be said to be proof that stress is generated in the silicon substrate. In such a state, a cell breakage occurs because further mechanical stress is applied during modularization such as serial connection of cells or attachment to a glass plate.
  Moreover, in the latter (for example, patent document 2), there exists a difficulty in application of the module structure of a highly efficient and thin silicon solar cell.
[0007]
  One of the main objects of the present invention is to provide a solar cell and a solar cell module using the solar cell that can greatly reduce cracks due to a thin and large area of a semiconductor substrate and further reduce the cost. is there.
[0008]
[Means for Solving the Problems]
  Thus, according to the present invention,Semiconductor substrate having photoelectric conversion functionAnd this semiconductorsubstrateA light receiving surface electrode provided on the light receiving surface side of the semiconductor, and a semiconductorsubstrateA back surface electrode part provided on the back side of the solar cell, at least the light receiving surface electrode part,It consists of a plurality of linear or branched light receiving surface separation electrodes, and the plurality of light receiving surface separation electrodes are arranged separately and function as electrodes for taking out current to the outside.A solar cell is provided.
  In other words, the solar battery cell of the present invention has a light receiving surface electrode portion on the light receiving surface side separated into a plurality of parts, whereby a semiconductorsubstrateThe mechanical stress due to the light-receiving surface electrode can be dispersed against the semiconductorsubstrateSpecifically, the main grid electrode (thick line electrode portion) of the light receiving surface side electrode in the conventional solar cell (see FIG. 9) is omitted. Alternatively, it is formed in an electrode structure that is separated and reduced.
[0009]
  Here, in the present invention, a semiconductor having a photoelectric conversion function in which a plurality of semiconductor layers are stacked.substrateCan be formed by a known technique mainly using a silicon substrate, but in addition to the silicon substrate, a known material such as a compound semiconductor substrate such as a silicon germanium substrate or a gallium arsenide substrate can also be used. For example, as a basic structure, n and p from the light incident side, or p and n from the light incident side are possible. Furthermore, the light incident side may be n + with a high concentration instead of n, or the light incident side may be a p + with high concentration instead of p. These light-receiving surface-side semiconductor layers (hereinafter sometimes referred to as light-receiving surface-side bonding layers) can be formed by a conventionally used thermal diffusion method or ion implantation method. Further, an antireflection film may be formed on the surface of the light receiving surface side bonding layer. On the other hand, a BSF layer or a back surface reflector (back surface reflector) may be formed on the back surface opposite to the light incident side, or an oxide film or a nitride film may be formed to prevent surface recombination. Various oxide films can be used as the antireflection film and the back surface reflection film.
[0010]
  In the present invention, each of the light receiving surface electrode portionsPhotosensitive surfaceThe separation electrode can be formed by, for example, a printing method of printing and baking a conductive paste containing Ag powder as a main component, an Ag and / or Al vapor deposition method, or the like. Also,Photosensitive surfaceThe separation electrode can typically be exemplified by electrode pattern shapes formed at a predetermined pitch parallel to each other as straight lines having a constant width, but a plurality of adjacent (for example, two or three) electrodes can be cited.Photosensitive surfaceConnect the current extraction side ends of the separation electrodes to make one set with multiple pieces, and multiple sets as a wholeBranched light receiving surfaceIt can also be set as the electrode pattern which has arrange | positioned the separation electrode. Furthermore,Photosensitive surfaceMaking the separation electrode a curve,Photosensitive surfaceDo not place the separation electrodes in parallel.Photosensitive surfaceChanging the line width of the separation electrode,Photosensitive surfaceChanging the thickness of the separation electrode,Photosensitive surfaceIt is possible to embed the separation electrode in the substrate by detailed design.
[0011]
  In the present invention, the back electrode portion on the back side is(1)Consisting of full surface electrodes, or(2)As with the light receiving surface electrode,Multiple backs of linear or branched linesIt can consist of a separation electrode. the above(1)In this case, the entire surface electrode can be formed by printing and baking a paste material mainly composed of powdered aluminum on the entire back surface of the silicon substrate. the above(2)In the case ofBack sideA separation electrode can be formed. In one solar battery cell, the electrode pattern of the back electrode part may be the same as or different from the electrode pattern of the front electrode part.
[0012]
  According to the present invention, in the process of manufacturing a solar cell module by electrically connecting solar cells in series by separately forming an electrode (light-receiving surface electrode portion) on one surface serving as a light-receiving surface, Each of the light receiving surface electrode part of the solar battery cellPhotosensitive surfaceStress concentration on the light receiving surface side when electrically connecting the separation electrode and the back electrode portion of another adjacent solar battery cell can be avoided, and cracking of the solar battery cell can be reduced. The back electrode part is the above(1)In the case of a full surface electrode, the back surface field effect, that is, the effect of collecting the generated carriers by making electrolysis inside the cell by the highly concentrated semiconductor layer (for example, p + portion) on the back electrode side is improved. Thus, high cell photoelectric conversion efficiency can also be obtained. Also, above(2)Like the light receiving surface electrode part, the back electrode part isMultiple branched line backBy using separate electrodes, the light-receiving surface has the same effects as stress concentration avoidance, and the semiconductors originated from the front and back electrodessubstrateIt is possible to significantly reduce the mechanical stress on the solar cell, thereby making it possible to manufacture a large area (for example, 150 × 150 mm) solar cell with a thin semiconductor substrate of 100 μm or less.
[0013]
  In the present invention, each of the light receiving surface electrode portionsPhotosensitive surfaceSeparation electrode pitch or back electrode partBack sideThe pitch of the separation electrodes is preferably set to 0.5 to 5 mm, and preferably the pitch is 1 to 3 mm. If comprised in this way, it will become technically easy to manufacture a high-performance solar cell with high cell photoelectric conversion efficiency while using a thin large-area substrate of 100 μm or less. In particular, when the pitch is 1 to 3 mm, a solar battery cell with extremely high photoelectric conversion efficiency can be obtained. In addition,Each light receiving surface separation electrode and each back surface separation electrodeIf the pitch is less than 0.5 mm, the electrode area is increased and the light incident area is reduced, so that the photoelectric conversion efficiency is drastically reduced. Also,Each light receiving surface separation electrode and each back surface separation electrodeWhen the pitch of 5 mm exceeds 5 mm, when the current moves through the light-receiving surface side bonding layer to reach the electrode, the resistance component becomes too large and is consumed by the resistance heat generation inside the cell, and the photoelectric conversion efficiency is drastically reduced. .
[0014]
  In the present invention, each of the light receiving surface electrode portionsPhotosensitive surfaceThe separation electrodes are formed in parallel with each other at a predetermined pitch, and each of the back electrode portionsBack sideWhen the separation electrodes are formed at a predetermined pitch parallel to each other,Photosensitive surfaceSeparation electrode pitch andEach backThe ratio with the pitch of the separation electrodes is preferably set to 1: 3 to 3: 1, and preferably the ratio is substantially the same. By configuring in this way, when manufacturing the solar cell module, while suppressing the number of connections per cell (number of metal wires for connection), each of the separation electrodes of the light receiving surface electrode portion and the back surface electrode portion in each cell. The burden current can be adjusted, and high photoelectric conversion efficiency can be obtained. In particular, by making the above ratios substantially the same (approximately 1: 1), in addition to high photoelectric conversion efficiency, when the inside of the module is connected in series, the electrical connection between adjacent cells can be stress-relieved, The shortest distance with curvature, andEach light receiving surface separation electrode and each back surface separation electrodeCan be connected (wired) in a one-to-one relationship, making the connection work easy and significantly reducing the light-receiving surface connection failure rate. In addition,Photosensitive surfaceFor separation electrode pitchBack sideWhen the separation electrode pitch exceeds 3 times,Photosensitive surfaceAs the number of separation electrodes increases, the number of electrical connection points increases and the light receiving surface connection failure rate increases rapidly. vice versaBack sideFor separation electrode pitchPhotosensitive surfaceIf the separation electrode pitch exceeds three times, satisfactory photoelectric conversion efficiency cannot be obtained.
[0015]
  Moreover, the solar battery cell in the present invention is a semiconductor.substrateLight receiving surfaceSideThe sheet resistance value may be 80 to 250 Ω / □, and the pitch of each separation electrode of the light receiving surface electrode portion may be set to 1 to 2 mm. By comprising in this way, a high short circuit current density can be obtained. In particular, the sheet resistance value is 150 to 200Ω / □, and each of the light receiving surface electrode portionsPhotosensitive surfaceIf the pitch of the separation electrodes is set to 1 to 1.5 mm, a remarkably high short-circuit current density can be obtained, which is preferable. Even if the sheet resistance value deviates from the range of 80 to 250 Ω / □ or the pitch deviates from the range of 1 to 2 mm, a satisfactory high short-circuit current density cannot be obtained.
[0016]
  According to another aspect of the present invention, a plurality of solar cells having the above-described configuration are electrically connected in series, and the connection is made for each of the light receiving surface electrode portions of one solar cell.Photosensitive surfaceThere is provided a solar battery module formed between the separation electrode and the back electrode part of another adjacent solar battery cell. In this modularization, mechanical stress applied when the cells are connected in series or pasted to a glass plate is avoided, and cell cracking is reduced.
  Furthermore, as with the light receiving surface electrode portion, the back surface electrode portion is alsoMultiple backs of linear or branched linesConsists of separation electrodes, each of the light-receiving surface electrode parts between adjacent solar cellsPhotosensitive surfaceEach of separation electrode and back electrode partBack separation electrodeAre electrically connected to each other, so that the cell cracking is further reduced, and a solar cell having a large area (for example, 150 × 150 mm) can be obtained at a low cost with a thin semiconductor substrate of 100 μm or less.
[0017]
  In the solar cell module of the present invention, the number of electrical connection locations on the light-receiving surface electrode portion side is preferably set to 5 to 1000 locations, and preferably 10 to 50 electrical connection locations. It is. By configuring in this way, for example, in the case of having 100 electrical connection points per cell, the extraction current value per location is 8 mA to 80 mA (explained in FIG. 9), and the connection point The maximum height can be reduced from the conventional 0.9 mm to 0.15 mm or less, and the maximum width of the connection wiring can be reduced from the conventional 2.5 mm to 0.1 mm or less. As a result, the semiconductor substrate near the current extraction partTo boardIt is possible to reduce the concentrated stress to about 1/1000 or less, and it is possible to reliably reduce cell cracks in modularization. In particular, by setting the number of electrical connection points to 10 to 50, it is possible to shorten the connection time while reducing cell cracking. If the number of connection points is less than five, the electrode build-up thickness becomes large and the substrate thickness is equal to the conventional one. If the number of connection points exceeds 1,000, the connection speed per point is 100 ms (mm (Second) takes 1 minute or more per cell, and there is no merit in terms of cost.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment.
[0019]
[Embodiment 1]
  FIG. 1 is a perspective view of a solar battery cell according to Embodiment 1 of the present invention, FIG. 2 is a schematic configuration diagram of a solar battery module using the solar battery cell in the same embodiment, and FIG. 4 is an enlarged cross-sectional view of the main part of the solar cell module in the embodiment, FIG. 4 is an enlarged cross-sectional view of the main part of the solar cell module in the embodiment, and the adjacent solar cells are electrically connected with copper wires The connected state is shown.
[0020]
  The solar battery cell 10 of the first embodiment is,lightSemiconductor with electric conversion functionsubstrate11 and this semiconductorsubstrateA light-receiving surface electrode portion 12 provided on the light-receiving surface side of 11, and a semiconductorsubstrate11, a back electrode portion 13 provided on the back side of the semiconductor, and a semiconductorsubstrate11 and an antireflection film 14 formed on the light receiving surface.
[0021]
  Rectangular plate semiconductorsubstrate11 has an n + diffusion layer 11b on the light-receiving surface side of the p-type silicon substrate 11a and a p + layer 11c on the back side of the p-type silicon substrate 11a.
  The light receiving surface electrode portion 12 is a linear line separated into a plurality (in this case, 10).Photosensitive surfaceEach of the separation electrodes 12aPhotosensitive surfaceThe separation electrodes 12a are parallel to each other at an equal pitch P_12aIs arranged in.
  Similar to the light receiving surface electrode portion 12, the back surface electrode portion 13 is a linear line separated into a plurality of pieces (in this case, 10 pieces).Back sideIt consists of separation electrodes 13a, eachBack sideThe separation electrodes 13a are parallel to each other at an equal pitch P_13aIs arranged in.
  In the first embodiment, each of the light-receiving surface electrode portions 12Photosensitive surfaceEach of separation electrode 12a and back electrode part 13Back sideThe separation electrodes 13a have the same pitch P in the same direction_12a= P_13aThe case where it formed in (for example, 2 mm) is illustrated.
[0022]
  FIG. 2 shows a solar cell module M manufactured using eight of these solar cells 10, and in this case, two sets of cell rows 15 in which four solar cells 10 are connected in series are arranged in parallel. Each cell row 15, 15 is electrically connected at one end side by a conductive member 8. At the other end side opposite to the conductive member 8, one cell row 15 has a negative electrode terminal 6 and the other cell row 15 has The positive terminals 7 are electrically connected to each other.
[0023]
  As shown in FIG. 3 and FIG. 4, when modularizing, each of the light receiving surface electrode portions 12 of one solar battery cell 10.Photosensitive surfaceEach of the edge part of the separation electrode 12a, and the back surface electrode part 13 of the other adjacent photovoltaic cell 10Back sideThe copper wire 1 is soldered to the end of the separation electrode 13a, and the cells 10 are electrically connected in series. That meansPhotosensitive surfaceSeparation electrode 12a andBack sideThe separation electrodes 13a are connected to each other on a one-to-one basis. Therefore, in the first embodiment, there are 10 electrical connection locations S on the light-receiving surface electrode portion 12 side, and there are also 10 electrical connection locations S on the back electrode portion 13 side. The cell rows 15 and 15 are installed between the tempered glass 2 and the moisture-proof film 5 via the EVA sheets 3 and 4, whereby the solar cell module M is manufactured. In addition, about the manufacturing process of a photovoltaic cell and a photovoltaic module, it mentions in full detail in the below-mentioned Example.
[0024]
  According to the first embodiment of the present invention, the light receiving surface electrode portion and the back surface electrode portion are separated into a plurality of parts, thereby providing a semiconductor.substrateIn contrast, it has an electrode structure that can disperse mechanical stress due to the light-receiving surface electrode.substrateEven if the thickness is reduced, cell cracking due to modularization is greatly reduced, and a large area (for example, 150 × 150 mm) solar cell can be obtained with a thin semiconductor substrate of 100 μm or less. In addition, each of the light receiving surface electrode sectionPhotosensitive surfaceSeparation electrode pitch and back electrode partBack sideBy making the ratio with the pitch of the separation electrode 1: 1, a high photoelectric conversion efficiency is obtained, and when the inside of the module is connected in series, the electrical connection between adjacent cells can be stress-relieved, The shortest distance with curvature, andEach light receiving surface separation electrode and each back surface separation electrodeCan be connected on a one-to-one basis, the connection work is easy, and the light receiving surface connection failure rate is significantly reduced.
[0025]
[Embodiment 2]
  As shown in FIG. 5, the second embodiment of the present invention includes each of the light receiving surface electrode portions 22 of the solar battery cells 20.Photosensitive surfacePitch P of separation electrode 22a_22aAnd each of the back electrode part 23Back sidePitch P of separation electrode 23a_23aThe ratio is changed to 3: 1. in this case,Photosensitive surfaceThe number of separation electrodes 22a is five.Back sideThe number of separation electrodes 23a is fifteen. Other configurations are the same as those of the first embodiment. And in the case of modularization, one solar cell 20Photosensitive surfaceThe separation electrode 22a1 has another solar cell 20 adjacent to it.Three backsThe separation electrode 23 a is connected by three copper wires 1. Therefore, in this case, there are five electrical connection locations S on the light-receiving surface electrode portion 22 side, and there are 15 electrical connection locations S on the back electrode portion 23 side. In FIG. 5, the light-receiving surface electrode portion of the right solar cell 20 is not shown.
[0026]
  According to the second embodiment of the present invention, the light receiving surface separation electrode pitch P_22aAnd backside separation electrode pitch P_23aIs set to 3: 1 so that one of the light receiving surface electrode portions 22Photosensitive surfaceThree electrodes from the separation electrode 22a to the back electrode part 23Back sideIt is possible to connect to the separation electrode 23a, and in this manner, in each cell, each separation electrode 22a at the front surface electrode portion 22 and the back surface electrode portion 23 is suppressed while suppressing the electrical connection portion on the light receiving surface electrode portion 22 side per cell. , 23a can be adjusted, whereby the maximum photoelectric conversion efficiency can be obtained.
[0027]
[Embodiment 3]
  As shown in FIG. 6, the light receiving surface electrode part 32 of the photovoltaic cell 30 is shown in Embodiment 3 of the present invention.Is a linear light-receiving surface18 separation electrodes 32a are provided in parallel at a predetermined pitch,Linear photosensitive areaA set of three separation electrodes 32aOne branch line-shaped light receiving surface separation electrode is formed.Yes. In other words, this solar battery cell 30 has three adjacent electrical connection points in modularization.Photosensitive surfaceThe common electrode is used for the separation electrode 32a.Photosensitive surfaceThe end on the current extraction side of the separation electrode 32a is curved to the middlePhotosensitive surfaceIt is integrally connected to the end of the separation electrode 32a. In this case, one set of threePhotosensitive surfaceSince six sets of separation electrodes 32a are provided, there are six electrical connection points in the light-receiving surface electrode part 32. Although not shown, the back electrode portion may be the same electrode pattern as the light receiving surface electrode portion, a different electrode pattern, or a full surface electrode.
[0028]
  According to Embodiment 3 of the present invention,Photosensitive surfaceA plurality of adjacent electrode portions 32Photosensitive surfaceBy using an electrode pattern in which the current extraction side end of the separation electrode 32a is integrally connected in advance, the light receiving surface electrode portion per cell3The number of electrical connections on the two sides can be reduced, and the number of connections can be reduced as compared to the first embodiment.
[0029]
[Embodiment 4]
  As shown in FIG. 7, the fourth embodiment of the present invention has a light receiving surface electrode portion 42 of the solar battery cell 40.Photosensitive surface20 separation electrodes 42a are provided in parallel at a predetermined pitch,Photosensitive surfaceA set of four separation electrodes 42aOne branch line-shaped light receiving surface separation electrode is formed.Yes. In other words, there are four adjacent electrical connections in modularization.Photosensitive surfaceSeparated by the separation electrode 42a, for this reason, a pair of adjacentPhotosensitive surfaceThe ends of the separation electrode 42a are curved and connected to each other, and two pairs of two pairs are formed.Photosensitive surfaceThe separation electrode 42a is connected by a curved electrode connection portion 42b. In this case, one set of fourPhotosensitive surfaceSince five sets of separation electrodes 42a are provided, there are five electrical connection points in the light-receiving surface electrode portion 42. Although not shown, the back electrode portion may be the same electrode pattern as the light receiving surface electrode portion, a different electrode pattern, or a full surface electrode.
  According to the fourth embodiment, the same effect as in the third embodiment is obtained.
[0030]
[Other embodiments]
  In the above-described embodiment, the separation electrodes of the light-receiving surface electrode portion and the back electrode portion of the solar battery cell are electrode patterns formed in a straight line with a constant width and in parallel. An electrode pattern in which the separation electrode 52a is a wavy line as shown in (a), or an electrode pattern in which the separation electrodes 62a are not arranged in parallel as shown in FIG. Further, as shown in FIG. 8C, an electrode pattern is formed by combining substantially U-shaped separation electrodes 72a having different bending pitches, or the separation electrodes 82a and 92a are arranged in parallel as shown in FIGS. The electrode pattern may be a combination of straight lines, lines perpendicular to the parallel lines, and diagonal lines. Although only the light receiving surface electrode portion is shown in FIGS. 8A to 8E, the back electrode portion may be the same electrode pattern as the light receiving surface electrode portion, a different electrode pattern, or a full surface electrode. In the electrode patterns shown in FIGS. 8C, 8D, and 8E, the right end is an electrical connection portion of the light receiving surface electrode. Although not shown, the line width of the separation electrode may be changed, the thickness may be changed, a protrusion may be provided in the middle of the line, or the separation electrode may be embedded in the substrate.
  According to the present invention, as in the embodiment shown in FIGS. 8A to 8E, the design flexibility is wide in the shape, line width, thickness, arrangement, electrode pattern shape, etc. of each separation electrode. There are advantages.
[0031]
[Example 1]
  The solar battery cell 10 having the cell structure of the first embodiment described with reference to FIGS. 1 to 4 and the solar battery module M using the solar battery cell 10 were manufactured by the following manufacturing procedure.
[0032]
  First, a p-type silicon substrate 11a having an outer shape of 18 × 8 cm, a thickness of 0.24 mm, and a specific resistance of 2Ω / □ is sliced in a hydrofluoric acid (50%) / nitric acid mixed solution having a volume ratio of 1: 3. Layer removal is performed for 1 minute. Next, after spin-coating a BSG film on one side, boron diffusion for forming the P + layer 11c is performed in a heat treatment furnace at 900 ° C. for 30 minutes. The sheet resistance value of the P + layer 11c was 37Ω / □, and the junction depth was 0.4 μm. An acid-resistant tape is applied to this surface, and the P + layer on the other surface is removed in the hydrofluoric acid nitric acid solution. After removing and cleaning the tape with an organic solvent, the surface of the P + layer 11c is made of SiO for semiconductors.₂Apply coating agent and dry. 500 ° CofAfter densification by heating, POCl_Three860 ° C in an atmosphere containingofPerform phosphorus diffusion for 25 minutes in an electric furnace. The PSG (phosphorus glass) layer, etc. is removed from the HF-based solution to obtain a junction depth of about 0.3 μm and a surface concentration of 10¹⁹cm^-2The light receiving surface side n + diffusion layer 11b was obtained. The sheet resistance value of the n + diffusion layer 11b was 120Ω / □. Next, the surface of the n + diffusion layer 11b is made of Si using a plasma CVD apparatus._ThreeN_FourWas formed as an antireflection film 14. The thickness is about 800 mm. Silane and ammonia were used as gas species. In the next electrode formation, a paste containing Ag powder and Al powder was first printed and dried on the back surface. The back electrode 13a was formed by baking in a near-infrared furnace. Next, Si on the n + diffusion layer 11b is formed as a light receiving surface side electrode formation._ThreeN_FourScreen printing was performed on the antireflection film 14 with a pattern having an electrode pitch of 1.5 mm. As the electrode material on the light receiving surface side, a paste material mainly composed of Ag for solar cells was used. The solar cell 10 of the invention was completed by forming each separation electrode 12a of the light-receiving surface electrode portion 12 by firing at a temperature of about 650 ° C. using a near infrared furnace. In Example 1, the number of separation electrodes 12a of the light-receiving surface electrode portion 12 and the number of separation electrodes 13a of the back surface electrode portion 13 were each 52.
[0033]
  Irradiation intensity 100mW / cm²When the current-voltage characteristics of the manufactured solar cell 10 were measured under simulated sunlight, the short-circuit current density was 34.7 mA / cm.²The open circuit voltage was 0.6 V, the fill factor was 0.72, and the cell photoelectric conversion efficiency was 15.0%. At this time, a xenon lamp and a filter were used as a pseudo solar light source. A calibrated thermopile was used to measure the irradiation intensity. The short-circuit current density was measured by operating a solar cell under simulated sunlight using a digital variable voltage power supply. The cell photoelectric conversion efficiency was obtained by calculating the ratio of conversion energy to incident energy with respect to the cell area.
[0034]
  Next, as shown in FIG. 2, in a state where eight solar cells 10 thus produced are arranged, as shown in FIG.Photosensitive surfaceA copper wire 1 having a diameter of 80 μm and a length of 10 mm was soldered to each end of the separation electrode 12a. Furthermore, the other end of the copper wire 1 is connected to the back surface of the adjacent solar battery cell 10.Back sideEach was soldered to the separation electrode 13a. Between adjacent cells, the copper wire 1 was connected at 52 locations. Next, after placing the tempered glass 2, EVA (ethylene vinyl acetate) sheet 3, cell array 15 in which a plurality of solar cells 10 are connected in series, EVA sheet 4, and moisture-proof film 5 in this order in the laminator device. The solar cell module M was completed by the procedures of exhausting air, heating and sealing. A negative electrode terminal 6 and a positive electrode terminal 7 are attached to the solar cell module M. Note that the cell rows 15 and 15 arranged in two rows are electrically connected in series via the conductive member 8.
[0035]
  Further, Comparative Examples 1, 2, and 3 as described below were produced.
[Comparative Example 1]
  In Comparative Example 1, the cell thickness was changed from 0.24 mm to 0.35 mm. All other conditions were the same as in Example 1. In Comparative Example 1, 15.2% was obtained as the cell photoelectric conversion efficiency. Then, modularization was performed with this solar battery cell.
[Comparative Example 2]
  In Comparative Example 2, a cell and a module were manufactured by applying the conventional cell structure (see FIG. 9) to a 12 × 12 cm square polycrystalline silicon substrate having a substrate thickness of 0.24 mm. In the conventional structure, the light receiving surface electrode is composed of a grid electrode and a main grid electrode as shown in FIG. 9, and the back electrode is obtained by printing and baking aluminum paste on the back surface side. Other conditions are the same as those in the first embodiment. In Comparative Example 2, the cell photoelectric conversion efficiency was 13.8%. Then, modularization was performed with this solar battery cell.
[Comparative Example 3]
  In Comparative Example 3, the substrate thickness was changed from 0.24 mm to 0.35 mm to perform cell formation. All other conditions were the same as in Comparative Example 2. In Comparative Example 3, 14.1% was obtained as the cell photoelectric conversion efficiency. Then, modularization was performed with this solar battery cell.
  In Comparative Examples 1 to 3, the cell photoelectric conversion efficiency was measured under the same conditions as in Example 1.
[0036]
  The non-defective product rate and the non-defective product rate of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were determined, and the situation was summarized in Table 1.
[0037]
[Table 1]

[0038]
  In Table 1, the yield rate after cell formation is the yield when 100 cells are manufactured under the same conditions. There is no significant difference between Example 1 and Comparative Examples 1 to 3 regarding the yield rate after cell formation. Using these non-defective cells, 10 solar cell modules were prepared for Example 1 and Comparative Examples 1 to 3, respectively, and then the irradiation intensity was 100 mW / cm for each module.²The power generation efficiency of the module was measured using a negative electrode terminal and a positive electrode terminal (see FIG. 2) in a state in which simulated sunlight was irradiated. In Table 1, the module non-defective rate is the rate at which module characteristics corresponding to the characteristics of the cells enclosed in the module were obtained.
[0039]
  In Example 1 and Comparative Example 1, the cell structure of the present invention was used. Further, Comparative Example 2 and Comparative Example 3 used a conventional cell structure. As for the substrate thickness, cells are formed in a thin substrate in Example 1 and Comparative Example 2, and in a thick substrate in Comparative Example 1 and Comparative Example 3. About 90% or more of the non-defective product rate after the cell formation was obtained, but it became clear that the non-defective product rate when it was connected in series and modularized had a clear difference of 20 to 100%. That is, it can be said that most cells were damaged by the modularization when the conventional cell connection (two copper connections with a width of 2 mm per cell) using a thin substrate with a conventional cell structure (Comparative Example 2). However, even if the cell structure of Example 1 (the present invention) is made a thin substrate, the module yield is as high as 90%, which is almost the same as the conventional cell and module of Comparative Example 3.
[0040]
  Next, a solar cell having the cell structure of the first embodiment, which has a different number of electrically connected portions in the light-receiving surface electrode portion, is manufactured, and an electrode rising thickness for each solar cell is measured. The results are shown in Table 2. In addition, as shown in FIG. 4, this electrode rising thickness is a silicon substrate (semiconductorsubstrate11) the thickness T from the surface to the connection upper part of the separation electrode.
[0041]
[Table 2]

[0042]
  From Table 2, it can be seen that if the number of connection points is 5 or more, the electrode build-up thickness is reduced to 490 μm or less. In addition, when the number of connection points is four, the thickness of the raised electrode is about the same as the conventional one, and the substrate thickness cannot be reduced, and it is only the same as the conventional thickness. Although it can be reduced, since the time required for connection becomes enormous, the production efficiency is lowered and there is no merit.
[0043]
  Next, each solar cell having the cell structure of the first embodiment, that is, each of the light receiving surface electrode portionsPhotosensitive surfaceSeparation electrode pitch and back electrode partBack sideA plurality of solar cells having a separation electrode pitch of 1: 1 and a sheet resistivity of the light-receiving surface side bonding layer (n + layer) of 100Ω / □ and different pitches are manufactured and irradiated. Strength 100mW / cm²The cell photoelectric conversion efficiency was measured for each solar battery cell in the state of irradiating pseudo sunlight with, and the results are shown in Table 3. The sheet resistance value was measured using a four-probe measuring instrument used in the general semiconductor field.
[0044]
[Table 3]

[0045]
  From Table 3, each of the light receiving surface electrode partsPhotosensitive surfaceWhen the separation electrode pitch is 2 mm, the cell photoelectric conversion efficiency is as high as 20%, and then the photoelectric conversion efficiency is as high as 18 to 14% in the order of pitch 1 mm, 3 mm, 4 mm, 0.5 mm, and 5 mm. I understand. If the pitch is less than 0.5 mm,Photosensitive surfaceWhen the total area of the electrode becomes too large, the spectral incident area decreases, the cell photoelectric conversion efficiency decreases drastically, and when the pitch exceeds 5 mm, the current moves through the light-receiving surface side bonding layer and reaches the electrode. The resistance component becomes too large and is consumed by the resistance heat generation inside the cell, and the photoelectric conversion efficiency is drastically reduced.
[0046]
  Next, it is a photovoltaic cell of the electrode pattern of Embodiment 1, and each of the light-receiving surface electrode partPhotosensitive surfaceEach of the back electrode part with respect to the pitch of the separation electrodeBack sideA plurality of solar cells having different separation electrode pitch ratios are manufactured, and the light receiving surface connection failure rate is measured for each solar cell, and the irradiation intensity is 100 mW / cm.²The cell photoelectric conversion efficiency was measured in the state of irradiating pseudo sunlight with Table 4 and the results are shown in Table 4.
[0047]
[Table 4]

[0048]
  From Table 4, when the ratio is 1: 1, the light receiving surface connection failure rate is the lowest as 0.2% and the cell photoelectric conversion efficiency is as high as 15%. In the range of 3: 1, it can be seen that the light receiving surface connection failure rate is as low as 0.2 to 1.4% and the cell photoelectric conversion efficiency is as high as 15 to 13%. If the back surface separation electrode pitch with respect to the light receiving surface separation electrode pitch is large outside the range of the ratio of 1: 3 to 3: 1,Photosensitive surfaceIncreasing the number of separation electrodes increases the number of electrical connection points, and the failure rate of the light receiving surface connection increases dramatically.If the back surface separation electrode pitch with respect to the light receiving surface separation electrode pitch is small, the cell photoelectric conversion efficiency decreases and a satisfactory value I can't get it.
[0049]
  Next, in the solar cell of the electrode pattern of the first embodiment, the sheet resistance value of the light receiving surface bonding layer is different, and each of the light receiving surface electrode portionsPhotosensitive surfaceA plurality of solar cells having different separation electrode pitches were manufactured, and the irradiation intensity was 100 mW / cm.²The short circuit current density (mA / cm) for each solar cell in the state irradiated with simulated sunlight at²) And the results are shown in Table 5.
[0050]
[Table 5]

[0051]
  From Table 5, the short-circuit current density is 37 mA / cm when the sheet resistance is 200Ω / □ and the light receiving surface separation electrode pitch is 1 mm.²In the range where the sheet resistance value is 80 to 250 Ω / □ and the light receiving surface separation electrode pitch is 1 to 2 mm, the short circuit current density is 37 to 32 mA / cm.²I understand that it is expensive. In addition, even if the sheet resistance value deviates from the range of 80 to 250 Ω / □ or the light receiving surface separation electrode pitch deviates from the range of 1 to 2 mm, the short-circuit current density is reduced to obtain a satisfactory value. I can't.
[0052]
【The invention's effect】
  According to the present invention, in the process of manufacturing a solar cell module by electrically connecting solar cells in series by separately forming an electrode (light-receiving surface electrode portion) on one surface serving as a light-receiving surface, Each of the light receiving surface electrode part of the solar battery cellPhotosensitive surfaceIt is possible to avoid stress concentration on the light receiving surface side when electrically connecting the separation electrode and the back electrode portion (full surface electrode) of another adjacent solar battery cell, and to reduce the cracking of the solar battery cell In addition, a back surface electric field (buck surface field) effect due to the entire surface electrode of the back electrode portion can be obtained, and high cell photoelectric conversion efficiency can be obtained.
  Furthermore, as with the light receiving surface electrode portion, the back surface electrode portion also has a plurality of pieces.Back sideBy using separate electrodes, the light-receiving surface has the same effects as stress concentration avoidance, and the semiconductors originated from the front and back electrodessubstrateIt is possible to significantly reduce the mechanical stress on the semiconductor device, thereby making it possible to manufacture a large area solar cell with a thin semiconductor substrate of 100 μm or less.
  Therefore, according to the present invention, it is possible to provide a solar battery cell and a solar battery module using the solar battery which can greatly reduce the cracks due to the reduction in thickness and area of the semiconductor substrate and further reduce the cost.
[Brief description of the drawings]
FIG. 1 is a perspective view of a solar battery cell according to Embodiment 1 of the present invention.
FIG. 2 is a schematic configuration diagram of a solar cell module using solar cells in the same embodiment.
FIG. 3 is an enlarged cross-sectional view of a main part of the solar cell module in the same embodiment.
FIG. 4 is an enlarged cross-sectional view of a main part of the solar cell module according to the embodiment, showing a state in which adjacent solar cells are electrically connected with a copper wire.
FIG. 5 is an explanatory diagram showing an electrode pattern of a solar battery cell and a connection state between cells according to Embodiment 2 of the present invention.
FIG. 6 is a plan view of a solar battery cell according to Embodiment 3 of the present invention.
FIG. 7 is a plan view of a solar battery cell according to a fourth embodiment of the present invention.
FIG. 8 is a plan view of a solar battery cell according to another embodiment of the present invention.
FIG. 9 is a perspective view of a conventional solar battery cell.
[Explanation of symbols]
11 Semiconductorsubstrate
12, 22, 32, 42 Light-receiving surface electrode section
13, 23 Back electrode part
10, 20, 30, 40 Solar cell
12a, 22a, 32a, 42aPhotosensitive surfaceSeparation electrode
13a, 23aBack sideSeparation electrode
P_12a, P_22a  Predetermined pitch
P_13a, P_23a  Predetermined pitch
11b Light-receiving surface side semiconductor layer
S Electrical connection location

Claims (11)

A semiconductor substrate having a photoelectric conversion function, a light-receiving surface electrode portion provided on the light-receiving surface side of the semiconductor substrate, a solar cell and a back electrode portion provided on a rear surface side of the semiconductor substrate, at least the light receiving surface The electrode portion is composed of a plurality of light receiving surface separation electrodes that are linear or branched,
The plurality of light receiving surface separation electrodes are separately disposed and function as electrodes for taking out current to the outside . The back surface electrode portion is composed of a plurality of back surface separation electrodes that are linear or branched,
2. The solar cell according to claim 1, wherein the plurality of back surface separation electrodes are disposed separately and function as electrodes for taking out current to the outside . The photovoltaic cell of Claim 1 or 2 by which each light-receiving surface isolation | separation electrode is arrange | positioned in parallel with each other with the predetermined pitch. The solar cell according to claim 2 or 3, wherein the back surface separation electrodes are arranged in parallel with each other at a predetermined pitch. The solar cell according to claim 3 or 4, wherein a pitch of each light receiving surface separation electrode and each back surface separation electrode is set to 0.5 to 5 mm. The photovoltaic cell according to claim 4 or 5, wherein a ratio between a pitch of each light receiving surface separation electrode and a pitch of each back surface separation electrode is set to 1: 3 to 3: 1. The solar cell according to claim 6, wherein the ratio between the pitch of each light receiving surface separation electrode and the pitch of each back surface separation electrode is substantially the same. The photovoltaic cell according to any one of claims 3 to 7, wherein the sheet resistance value on the light receiving surface side of the semiconductor substrate is 80 to 250 Ω / □, and the pitch of each light receiving surface separation electrode is set to 1 to 2 mm. . A plurality of solar cells according to claim 1 are electrically connected in series, and the connection is made between each light receiving surface separation electrode of the light receiving surface electrode portion of one solar cell and another adjacent solar cell. A solar cell module, characterized in that the solar cell module is formed with a back electrode portion of a battery cell. 10. The solar cell module according to claim 9, wherein the back surface electrode portion includes a plurality of linear or branched back surface separation electrodes that are electrically connected to each light receiving surface separation electrode of the light receiving surface electrode portion.   The solar cell module according to claim 9 or 10, wherein the number of electrical connection portions on the light-receiving surface electrode portion side is set to 5 to 1000 locations.

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