JP5923735B2 - Manufacturing method of solar cell - Google Patents

Description

  The present invention relates to a method for manufacturing a solar cell.

  Conventionally, a back junction solar cell is known as a solar cell capable of realizing improved photoelectric conversion efficiency (see, for example, Patent Document 1). Patent Document 1 describes that a back electrode is formed by a screen printing method.

JP-A-2005-101240

  The method described in Patent Document 1 has a problem that it is difficult to manufacture a solar cell having improved photoelectric conversion efficiency.

  The main object of the present invention is to provide a method capable of producing a solar cell having improved photoelectric conversion efficiency.

  In the method for manufacturing a solar cell according to the present invention, a photoelectric conversion unit having a p-type surface and an n-type surface on one main surface is prepared. An insulating layer that partitions the p-type surface and the n-type surface is formed on one main surface of the photoelectric conversion unit. After forming the insulating layer, an electrode forming step is performed in which a p-side electrode is formed on the p-type surface and an n-side electrode is formed on the n-type surface by plating.

  ADVANTAGE OF THE INVENTION According to this invention, the method which can manufacture the solar cell which has the improved photoelectric conversion efficiency can be provided.

It is a schematic sectional drawing for demonstrating the solar cell manufacturing process in 1st Embodiment. It is a schematic sectional drawing for demonstrating the solar cell manufacturing process in 1st Embodiment. It is a schematic sectional drawing for demonstrating the solar cell manufacturing process in 1st Embodiment. It is schematic-drawing sectional drawing of an example of a photoelectric conversion part. It is schematic-drawing sectional drawing of the other example of a photoelectric conversion part.

  Hereinafter, an example of the preferable form which implemented this invention is demonstrated. However, the following embodiment is merely an example. The present invention is not limited to the following embodiments.

  Moreover, in each drawing referred in embodiment etc., the member which has a substantially the same function shall be referred with the same code | symbol. The drawings referred to in the embodiments and the like are schematically described, and the ratio of the dimensions of the objects drawn in the drawings may be different from the ratio of the dimensions of the actual objects. The dimensional ratio of the object may be different between the drawings. The specific dimensional ratio of the object should be determined in consideration of the following description.

  In the present embodiment, an example of a method for manufacturing the back junction solar cell 1 shown in FIG. 3 will be described.

  First, the photoelectric conversion unit 10 shown in FIG. 1 is prepared. The photoelectric conversion unit 10 is not particularly limited as long as it has a p-type surface 10 bp and an n-type surface 10 bn on one main surface (back surface) 10 b. An example of the photoelectric conversion unit 10 will be described later.

  Next, the insulating layer 22 that partitions the p-type surface 10 bp and the n-type surface 10 bn is formed on the main surface 10 b of the photoelectric conversion unit 10. The insulating layer 22 may be composed of, for example, an inorganic insulating material such as silicon oxide or silicon nitride, or an organic insulating material such as a photosensitive or non-photosensitive epoxy resin or polyimide resin, or ethylene vinyl acetate copolymer resin. it can. The insulating layer 22 can be formed, for example, by removing a part of the insulating film formed on the main surface 10b by etching or the like. When the insulating layer 22 is formed of an organic insulating material, the insulating layer 22 can be formed by a printing method such as a screen printing method or an ink jet method. When the insulating layer 22 is formed of a photosensitive resin material, the insulating layer 22 can also be formed using a photolithography method.

  Next, the seed layer 21 is formed on the main surface 10 b of the photoelectric conversion unit 10. Specifically, a planar seed layer 21 is formed on substantially the entire main surface 10 b including the insulating layer 22. The seed layer 21 is a layer that serves as a seed for plating. The seed layer 21 can be formed by a sputtering method, a CVD method, an electroless plating method, or the like. Moreover, the seed layer 21 can be comprised by the laminated body of transparent conductive films, such as ITO (indium tin oxide), metal films, such as Cu, or a transparent conductive film and a metal film, for example.

  Next, the p-side electrode 13p (see FIG. 3) is formed on the p-type surface 10bp by a plating method such as an electroless plating method or an electrolytic plating method, and the n-side electrode 14n is formed on the n-type surface 10bn. The solar cell 1 can be completed by performing the electrode formation process which forms.

  In the present embodiment, specifically, as shown in FIG. 2, first, in the electrode forming step, the conductive film 12 thicker than the insulating layer 22 is formed on the main surface 10 b of the photoelectric conversion unit 10. The conductive film 12 is formed over substantially the entire main surface 10b so as to straddle a portion where the insulating layer 22 is not provided and a portion where the insulating layer 22 is provided. Therefore, in this state, the portion located on the p-type surface 10bp of the conductive film 12 and the portion located on the n-type surface 10bn are electrically connected.

  Next, the thickness of the conductive film 12 is set to be equal to or less than the thickness of the insulating layer. Thereby, the part located on the p-type surface 10bp of the conductive film 12 and the part located on the n-type surface 10bn are separated by the insulating layer 22, and the p-type surface 10bp of the conductive film 12 is separated. A p-side electrode 13p is formed from a portion located on the n-type surface, and an n-side electrode 14n is formed from a portion located on the n-type surface 10bn of the conductive film 12.

  Note that examples of a method for reducing the thickness of the conductive film 12 include a polishing method by mechanical polishing, and a CMP (Chemical Mechanical Polishing) method using both mechanical polishing and chemical polishing. When the flatness of the surface of the conductive film 12 is high, an etch back method is preferably used.

  Note that in the step of reducing the thickness of the conductive film 12, the thickness of the insulating layer 22 may be simultaneously reduced so that the thickness of the conductive film 12 is equal to the thickness of the insulating layer 22.

  As described above, in the present embodiment, the seed layer 21 is formed by the sputtering method with the insulating layer 22 provided, and the p-side electrode 13p and the n-side electrode 14n are formed by the plating method. For this reason, the p-side electrode 13p and the n-side electrode 14n can be formed with high shape accuracy. Therefore, the interval between the p-side electrode 13p and the n-side electrode 14n can be reduced. Accordingly, it is possible to manufacture the solar cell 1 having improved photoelectric conversion efficiency.

  When the insulating layer 22 is not removed after the step of setting the thickness of the conductive film 12 to be equal to or less than the thickness of the insulating layer 22 as in the present embodiment, the solar cell 1 having the insulating layer 22 can be obtained. By having the insulating layer 22, the insulation between the p-side electrode 13p and the n-side electrode 14n is sufficiently maintained, and the reliability of the solar cell 1 is improved.

  In addition, by forming the seed layer 21 in the state where the insulating layer 22 is provided, when the conductive film 12 is formed by the electroplating method, a current can be supplied uniformly to the entire seed layer 21. Thereby, the uniformity of the film thickness of the conductive film 12 is improved.

  By the way, a first seed layer is formed on the n-type surface, a second seed layer isolated from the first seed layer is formed on the p-type surface, and then the seed layer is formed by plating. It is also conceivable to form a p-side electrode and an n-side electrode on the substrate. However, in this case, if the distance between the first seed layer and the second seed layer is small, the p-side electrode and the n-side electrode may come into contact with each other. For this reason, it is necessary to widen the distance between the first seed layer and the second seed layer. On the other hand, in the present embodiment in which the insulating layer 22 is provided, there is no possibility that the p-side electrode 13p and the n-side electrode 14n are in contact with each other, and therefore, the interval between the p-side electrode 13p and the n-side electrode 14n is reduced. Can do. Therefore, the solar cell 1 having improved photoelectric conversion efficiency can be manufactured.

  In the present embodiment, the thickness of the conductive film 12 is reduced after the conductive film 12 is formed thicker than the insulating layer 22. However, the conductive film 12 is formed thinner than the insulating layer 22, and the p-side electrode 13 p and The n-side electrode 14n may be formed.

(Example of photoelectric conversion unit 10)
FIG. 4 is a schematic cross-sectional view of an example of the photoelectric conversion unit. As shown in FIG. 4, in this example, the photoelectric conversion unit 10 includes a substrate 11. The substrate 11 is made of a semiconductor material. The substrate 11 can be made of, for example, a crystalline semiconductor such as crystalline silicon. The substrate 11 has one conductivity type. Specifically, an example in which the conductivity type of the substrate 11 is n-type will be described here.

  On the first main surface 11a located on the other main surface (light receiving surface) 10a side of the substrate 11, a semiconductor layer 15n made of an n-type semiconductor having the same conductivity type as the substrate 11 is disposed. . The semiconductor layer 15n covers substantially the entire first major surface 11a. The semiconductor layer 15n can be composed of n-type amorphous silicon or the like.

  A semiconductor layer made of a substantially intrinsic i-type semiconductor having a thickness that does not substantially contribute to power generation, for example, about several to 250 mm, is disposed between the semiconductor layer 15n and the first main surface 11a. May be.

  On the surface of the semiconductor layer 15n opposite to the substrate 11, a reflection suppressing layer 16 having both a function of suppressing reflection and a function as a protective film is disposed. The reflection suppressing layer 16 constitutes the light receiving surface 10 a of the photoelectric conversion unit 10. The reflection suppression layer 16 can be made of, for example, silicon nitride.

  A semiconductor layer 17 p made of a p-type semiconductor having a conductivity type different from that of the substrate 11 is disposed on a part of the second main surface 11 b of the substrate 11. A semiconductor layer 18n made of an n-type semiconductor having the same conductivity type as that of the substrate 11 is disposed on at least a part of the second main surface 11b of the substrate 11 where the semiconductor layer 17p is not disposed. ing. The semiconductor layer 17p can be composed of, for example, p-type amorphous silicon. In the present embodiment, substantially the entire second main surface 11b is covered with the semiconductor layer 17p and the semiconductor layer 18n.

  The semiconductor layer 17p and the semiconductor layer 18n constitute the back surface 10b of the photoelectric conversion unit 10. The semiconductor layer 17p constitutes a p-type surface 10bp. The semiconductor layer 18n constitutes the n-type surface 10bn.

  A semiconductor layer made of a substantially intrinsic i-type semiconductor having a thickness that does not substantially contribute to power generation, for example, about several to 250 mm, is disposed between the semiconductor layer 17p and the second main surface 11b. May be. Similarly, between the semiconductor layer 18n and the second main surface 11b, there is a semiconductor layer made of a substantially intrinsic i-type semiconductor having a thickness that does not substantially contribute to power generation, for example, about several to 250 inches. It may be arranged. The semiconductor layer made of a substantially intrinsic i-type semiconductor can be made of, for example, i-type amorphous silicon.

  An end portion of the semiconductor layer 17p in the x-axis direction overlaps the semiconductor layer 18n in the thickness direction z. An insulating layer 19 is disposed between the end of the semiconductor layer 17p and the semiconductor layer 18n. The insulating layer 19 can be made of, for example, silicon nitride or silicon oxide.

  As described above, the insulating layer 22 is formed on the photoelectric conversion unit 10 thus configured. After forming the insulating layer 22, the seed layer 21 is formed by sputtering, and the p-side electrode 13pn side electrode 14n is formed by plating, whereby the solar cell 1 can be completed.

(Another example of the photoelectric conversion unit 10)
FIG. 5 is a schematic cross-sectional view of another example of the photoelectric conversion unit. As shown in FIG. 5, in this example, a substantially intrinsic i having a thickness that does not substantially contribute to power generation, for example, about several to 250 inches, is formed between the substrate 11 and the semiconductor layer 17p. A semiconductor layer 17i made of a type semiconductor is disposed. Between the substrate 11 and the semiconductor layer 18n, a semiconductor layer 18i made of a substantially intrinsic i-type semiconductor having a thickness that does not substantially contribute to power generation, for example, about several to 250 inches is disposed.

  The semiconductor layer 17i and the semiconductor layer 17p are arranged so as to cover substantially the entire second main surface 11b including the top of the semiconductor layer 18n. For this reason, the semiconductor layer 17i and the semiconductor layer 17p are also disposed on the semiconductor layer 18n. A recombination layer 20 is disposed between the semiconductor layer 18n and the semiconductor layer 17p. Thus, a further semiconductor layer may be provided on the n-type surface 10bn constituted by the semiconductor layer 18n.

  The electrons collected at the p-type surface 10 bp are taken out from the p-side electrode 13p that is in direct contact with the semiconductor layer 17p. On the other hand, electrons collected on the n-type surface 10bn are extracted from the n-side electrode 14n through the recombination layer 20, the semiconductor layer 17i, and the semiconductor layer 17p.

  The recombination layer 20 can be made of a semiconductor material having many in-gap levels in the energy band, a metal material in ohmic contact with the p-type semiconductor layer, or the like. By selecting such a material as the material of the recombination layer 20, loss of electrons taken out from the n-side electrode 22n can be reduced. Specifically, the recombination layer 20 can be composed of, for example, p-type amorphous silicon.

  As described above, the seed layer 21 and the insulating layer 22 are formed on the photoelectric conversion unit 10 thus configured. After forming the insulating layer 22, the p-side electrode 13pn side electrode 14n is formed by plating, and the solar cell 1 can be completed.

  The p-type surface 10bp and the n-type surface 10bn are connected via the semiconductor layer 17i and the semiconductor layer 17p. However, since the semiconductor layer 17i and the semiconductor layer 17p are thin, the resistance is large and the flowing current is small. Thereby, the current generated from the p-side electrode 13p and the n-side electrode 14n can be efficiently extracted while omitting the step of forming the semiconductor layer 17i and the semiconductor layer 17p.

DESCRIPTION OF SYMBOLS 1 ... Solar cell 10 ... Photoelectric conversion part 10a, 10b ... Main surface 10bn ... N-type surface 10bp ... P-type surface 12 ... Conductive film 13p ... P-side electrode 14n ... N-side electrode 21 ... Seed layer 22 ... Insulating layer

Claims (2)

Preparing a photoelectric conversion part having a p-type surface and an n-type surface on one principal surface;
Forming an insulating layer that partitions the p-type surface and the n-type surface on one main surface of the photoelectric conversion unit;
Forming a seed layer in a state where the insulating layer is provided after forming the insulating layer;
A conductive film is formed by flowing a current through the seed layer by plating, and a p-side electrode is formed on the p-type surface by the conductive film, and an n-side electrode is formed on the n-type surface. An electrode forming step to be formed;
A method for manufacturing a solar cell.   In the electrode formation step, after forming a conductive film thicker than the insulating layer on one main surface of the photoelectric conversion unit, the conductive film is made to have a thickness equal to or less than the thickness of the insulating layer. A portion located on the p-type surface and a portion located on the n-type surface are separated by the insulating layer, and the p-side electrode and the n-side electrode are formed from the insulating layer. The method for manufacturing a solar cell according to claim 1.

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