JP6350981B2 - Solar cell - Google Patents

Description

  The present invention relates to a solar cell and a manufacturing method thereof.

  The solar cell module is configured by connecting a plurality of solar cells. In such a solar cell module, if some of the solar cells cannot receive sunlight due to entering the shadow of an obstacle, the solar cells It is known that the total generated voltage of other solar cells is applied as a reverse voltage and a phenomenon (hot spot phenomenon) in which some of the solar cells generate heat (for example, Patent Document 1) occurs.

JP 2013-33832 A

  The objective of this invention is providing the solar cell which can suppress that a hot spot phenomenon generate | occur | produces, and its manufacturing method.

  The solar cell of the present invention includes a first main surface and a one-conductivity type crystalline silicon substrate having a second main surface provided on the opposite side of the first main surface, and the first main surface side. An amorphous silicon film of another conductivity type provided, and an amorphous silicon film of one conductivity type provided on the second main surface side, and the other conductivity type amorphous silicon film provided on a peripheral portion of the crystalline silicon substrate. A fragile portion in which the pn junction between the amorphous silicon film and the crystalline silicon substrate is easily broken is formed.

  The method for manufacturing a solar cell of the present invention includes a first main surface and a one-conductivity type crystalline silicon substrate having a second main surface provided on the opposite side of the first main surface, and the first main surface. A method of manufacturing a solar cell comprising an amorphous silicon film of another conductivity type provided on the surface side and an amorphous silicon film of one conductivity type provided on the second main surface side, comprising at least the above-mentioned A step of preparing the crystalline silicon substrate having a first concavo-convex structure in which a (111) plane of crystalline silicon is exposed on a first principal surface; and the other on the first principal surface side of the crystalline silicon substrate. Forming a conductive amorphous silicon film; forming the one conductive amorphous silicon film on the second main surface side of the crystalline silicon substrate; and a peripheral portion of the crystalline silicon substrate. The other conductivity type amorphous silicon film and the crystalline silicon group. According to and a step of pn junction forms a easily fragile portion is broken.

  According to the present invention, occurrence of a hot spot phenomenon can be suppressed.

It is typical sectional drawing which shows the peripheral part vicinity of the solar cell of embodiment. It is typical sectional drawing which shows the peripheral part vicinity of the crystalline silicon substrate before roughening the surface by laser irradiation. It is typical sectional drawing which shows the peripheral part vicinity of the crystalline silicon substrate after roughening the surface by laser irradiation. FIG. 4 is a schematic cross-sectional view showing a state in which an amorphous silicon film and a transparent electrode layer are formed on a crystalline silicon substrate and then the crystalline silicon substrate is irradiated with a laser.

  Hereinafter, preferred embodiments will be described. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In each drawing, members having substantially the same function may be referred to by the same reference numeral.

  FIG. 1 is a schematic cross-sectional view showing the vicinity of the peripheral edge of the solar cell of the embodiment. The solar cell 1 of the present embodiment includes a first conductive crystal silicon substrate 10 having a first main surface 11 and a second main surface 12 provided on the opposite side of the first main surface 11, and a first An amorphous silicon film 23 of another conductivity type provided on the main surface 11 side and an amorphous silicon film 24 of one conductivity type provided on the second main surface 12 side are provided. The solar cell 1 includes a first transparent electrode layer 31 provided on the other conductivity type amorphous silicon film 23 and a second transparent electrode layer provided on the one conductivity type amorphous silicon film 24. 32.

  In this embodiment, one conductivity type is n-type and the other conductivity type is p-type. Hereinafter, the solar cell 1 of this embodiment will be described with one conductivity type being n-type and the other conductivity type being p-type.

  A first intrinsic amorphous silicon film 21 is provided on the first major surface 11 of the n-type crystalline silicon substrate 10. A p-type amorphous silicon film 23 is provided on the first intrinsic amorphous silicon film 21. A second intrinsic amorphous silicon film 22 is provided on the second main surface 12 of the n-type crystalline silicon substrate 10. An n-type amorphous silicon film 24 is provided on the second intrinsic amorphous silicon film 22. A first transparent electrode layer 31 is provided on the p-type amorphous silicon film 23. A second transparent electrode layer 32 is provided on the n-type amorphous silicon film 24. On the first transparent electrode layer 31 and the second transparent electrode layer 32, collector electrodes (not shown) such as finger electrodes and bus bar electrodes are formed. A bus bar-less collector electrode in which no bus bar electrode is formed may be used.

  As shown in FIG. 1, the first main surface 11 of the n-type crystalline silicon substrate 10 is formed with a first concavo-convex structure 11a in which the (111) plane of crystalline silicon is exposed. A second concavo-convex structure 11b different from the first concavo-convex structure 11a is formed at the peripheral edge S of the first main surface 11 of the n-type crystalline silicon substrate 10. In the present embodiment, as will be described later, the second concavo-convex structure 11b is formed in the peripheral portion S of the first main surface 11 by roughening the first concavo-convex structure 11a by laser irradiation or the like.

  In the present embodiment, the first concavo-convex structure 12 a in which the (111) plane of crystalline silicon is exposed is also formed on the second main surface 12 of the n-type crystalline silicon substrate 10. A second concavo-convex structure 12b different from the first concavo-convex structure 12a is also formed in the peripheral portion S of the second main surface 12. The second concavo-convex structure 12b is formed by roughening the first concavo-convex structure 12a by laser irradiation or the like.

  A first intrinsic amorphous silicon film 21 and a p-type amorphous silicon film 23 are formed on the second concavo-convex structure 11 b in the peripheral portion S, as in the region other than the peripheral portion S. However, since the second concavo-convex structure 11b has irregularities that are larger and irregular than the first concavo-convex structure 11a, the fragile portions 25 and 33 are formed. The fragile portions 25 and 33 are portions where the pn junction between the p-type amorphous silicon film 23 and the n-type crystalline silicon substrate 10 is easily broken. In the present embodiment, since the first intrinsic amorphous silicon film 21 is formed between the p-type amorphous silicon film 23 and the n-type crystalline silicon substrate 10, the fragile portions 25 and 33 have pin junctions. It is a part that is easily destroyed.

  In the fragile portion 25, the thickness of the first intrinsic amorphous silicon film 21 and the p-type amorphous silicon film 23 in the peripheral portion S of the n-type crystalline silicon substrate 10 is the same as that of the first intrinsic amorphous in the other region. It is formed by being thinner than the thickness of the silicon film 21 and the p-type amorphous silicon film 23.

  The fragile portion 33 is configured such that the first transparent electrode layer 31 is in contact with the p-type amorphous silicon film 23 and the n-type crystalline silicon substrate 10, so that the p-type amorphous silicon film 23 and the n-type crystalline silicon substrate 10 are in contact with each other. Is formed by short-circuiting.

  Therefore, in this embodiment, the fragile portions 25 and 33 are formed by forming the second concavo-convex structure 11b different from the first concavo-convex structure 11a on the peripheral edge S of the n-type crystalline silicon substrate 10. .

  In the present embodiment, fragile portions 25 and 33 in which the pn junction (pin junction) is easily broken are formed in the peripheral edge portion S of the n-type crystalline silicon substrate 10. For this reason, when a reverse voltage is applied to the solar cell 1, it is possible to suppress the weak spots 25 and 33 from being a current leakage path and the occurrence of the hot spot phenomenon. Moreover, since the weak parts 25 and 33 are formed in the peripheral part S of the n-type crystalline silicon substrate 10, the occurrence of a hot spot phenomenon can be suppressed without reducing the cell characteristics of the solar cell 1. Further, since the peripheral portion S of the n-type crystalline silicon substrate 10 has a larger surface area than the central portion, even if a current flows through the leak path composed of the fragile portions 25 and 33, the battery density does not increase. The calorific value is small.

  In the present embodiment, fragile portions 25 and 33 are formed in a region where the second transparent electrode layer 32 is not formed in the peripheral edge portion S of the n-type crystalline silicon substrate 10.

  The width of the region of peripheral edge S of n-type crystalline silicon substrate 10 is preferably in the range of 0.2 to 5% of the entire width of n-type crystalline silicon substrate 10.

  FIG. 2 is a schematic cross-sectional view showing the vicinity of the periphery of the crystalline silicon substrate before the surface is roughened by laser irradiation. As shown in FIG. 2, the first concavo-convex structure 11 a is formed on the first main surface 11 of the peripheral edge S of the n-type crystalline silicon substrate 10 before the surface is roughened by laser irradiation. Similarly, a first concavo-convex structure 12 a is formed on the second main surface 12. In this state, as shown in FIG. 2, the laser 40 is irradiated from the first main surface 11 side of the peripheral portion S of the n-type crystalline silicon substrate 10.

  As irradiation conditions for laser irradiation, for example, an Nd: YAG pulse laser with a wavelength of 1064 nm, a pulse width of 20 nm, a repetition frequency of 10 to 100 kHz, and an output of 10 W is used, a spot diameter of about 0.1 to 1 mm, a scanning speed of 10 to 100 mm / second. And the conditions for laser scanning irradiation.

  FIG. 3 is a schematic cross-sectional view showing the vicinity of the periphery of the crystalline silicon substrate after the surface is roughened by laser irradiation. As shown in FIG. 3, at the peripheral edge S of the n-type crystalline silicon substrate 10, the first concavo-convex structure 11a of the first main surface 11 is roughened by laser irradiation, and the second concavo-convex structure 11b is formed. . Similarly, the 1st uneven structure 12a of the 2nd main surface 12 is roughened by laser irradiation, and the 2nd uneven structure 12b is formed. Also, an uneven structure 10 b is formed on the end face 10 a of the n-type crystalline silicon substrate 10.

  The solar cell 1 of the embodiment shown in FIG. 1 includes a first intrinsic amorphous silicon film 21, a p-type amorphous silicon on the first main surface 11 of the n-type crystalline silicon substrate 10 shown in FIG. The film 23 and the first transparent electrode layer 31 are formed in this order. On the second main surface 12, the second intrinsic amorphous silicon film 22, the n-type amorphous silicon film 24, and the first transparent electrode layer 31 are formed. The two transparent electrode layers 32 can be formed in this order.

  As described above, in the manufacturing method of the present embodiment, the step of forming the fragile portions 25 and 33 is performed before the first intrinsic amorphous silicon film 21 and the p-type amorphous silicon film 23 are formed. A step of forming a second concavo-convex structure 11b different from the first concavo-convex structure 11a on the first main surface 11 of the peripheral edge S of the mold crystal silicon substrate 10 is included.

  In the said embodiment, although the method of irradiating a laser is shown as a method of forming the 2nd uneven structure 11b, this invention is not limited to this. For example, you may form the 2nd uneven structure 11b using the method of roughening a surface mechanically. Examples of methods for mechanically roughening the surface include mechanical polishing of the surface, blasting methods such as sand blasting, and etching methods such as plasma etching.

  FIG. 4 is a cross-sectional view for explaining a manufacturing method according to another embodiment. In this embodiment, after forming an amorphous silicon film and a transparent electrode layer on a crystalline silicon substrate, the crystalline silicon substrate is irradiated with a laser. As shown in FIG. 4, first concavo-convex structures 11 a and 12 a are formed on the first main surface 11 and the second main surface 12 of the peripheral edge S of the n-type crystalline silicon substrate 10, respectively. On the first main surface 11 of the n-type crystalline silicon substrate 10, the first intrinsic amorphous silicon film 21, the p-type amorphous silicon film 23, and the first transparent electrode layer 31 are arranged in this order. Is formed. A second intrinsic amorphous silicon film 22, an n-type amorphous silicon film 24, and a second transparent electrode layer 32 are formed on the second main surface 12 in this order.

  In this state, as shown in FIG. 4, the laser 40 is irradiated from the first main surface 11 side of the peripheral portion S of the n-type crystalline silicon substrate 10. By this laser irradiation, a fragile portion can be formed in the peripheral portion S of the n-type crystalline silicon substrate 10 as in the embodiment shown in FIG. This method can be used, for example, when a plurality of solar cells are produced as a base material and are divided into individual solar cells by laser irradiation.

  In the embodiment shown in FIG. 1, the fragile portion 25 in which the thickness of the amorphous silicon film is reduced and the fragile portion 33 due to a short circuit between the amorphous silicon film and the crystalline silicon substrate are shown as the fragile portion. The fragile part is not limited to these aspects. Further, as in the embodiment shown in FIG. 1, it is necessary that both the fragile portion 25 where the thickness of the amorphous silicon film is thin and the fragile portion 33 due to a short circuit between the amorphous silicon film and the crystalline silicon substrate are present. There may be only one of them.

The dopant concentration in the p-type amorphous silicon film 23 is higher than the dopant concentration in the first intrinsic amorphous silicon film 21 and is preferably 1 × 10 ²⁰ cm ⁻³ or more. Further, the thickness of the p-type amorphous silicon film 23 is made thin so as to reduce the absorption of light as much as possible. On the other hand, carriers generated in the photoelectric conversion portion are effectively separated at the joint portion, and the carriers are first separated. The transparent electrode layer 31 is preferably thick enough to be collected efficiently. Specifically, the p-type amorphous silicon film 23 preferably has a thickness of 1 nm to 50 nm.

The dopant concentration in the n-type amorphous silicon film 24 is higher than the dopant concentration in the second intrinsic amorphous silicon film 22 and is preferably 1 × 10 ²⁰ cm ⁻³ or more. The thickness of the n-type amorphous silicon film 24 is such that carriers generated inside the n-type crystalline silicon substrate 10 can be effectively separated at the junction, and the carriers can be efficiently collected by the second transparent electrode layer 32. It is preferable to make it thick. Specifically, the thickness of the n-type amorphous silicon film 24 is preferably 1 nm or more and 50 nm or less.

The dopant concentration in the n-type crystalline silicon substrate 10 is higher than the dopant concentration in the first intrinsic amorphous silicon film 21 and the second intrinsic amorphous silicon film 22 and is 1 × 10 ²⁰ cm ⁻³ or more. Is preferred.

The p-type or n-type dopant concentration in the first and second intrinsic amorphous silicon films 21 and 22 is preferably 5 × 10 ¹⁸ cm ⁻³ or less. The first and second intrinsic amorphous silicon films 21 and 22 are thinned so as to suppress light absorption as much as possible, while the surface of the n-type crystalline silicon substrate 10 is sufficiently passivated. It is preferable to increase the thickness. Specifically, it is preferably 1 nm or more and 25 nm or less, and more preferably 2 nm or more and 10 nm or less.

  In the solar cell 1 of the present embodiment, the first main surface 11 side may be the light receiving surface side, and the second main surface 12 side may be the light receiving surface side. Moreover, it is good also as a double-sided light reception type solar cell.

  The thickness of the first and second transparent electrode layers 31 and 32 is preferably 50 nm or more and 150 nm or less, and more preferably 70 nm or more and 120 nm or less. By setting the thicknesses of the first and second transparent electrode layers 31 and 32 within the above range, it is possible to suppress the increase in electric resistance while suppressing the absorption of incident light.

  Bus bar electrodes and finger electrodes (not shown) can be formed by a method for forming bus bar electrodes and finger electrodes in a general solar cell. For example, it can be formed by printing Ag (silver) paste.

  Each layer of the solar cell 1 can be formed as follows. First, it is preferable that the surface of the n-type crystalline silicon substrate 10 is cleaned before forming each layer. Specifically, it can be performed using a hydrofluoric acid solution or an RCA cleaning solution. The first concavo-convex structure 11a on the first main surface 11 and the first concavo-convex structure 12a on the second main surface 12 of the n-type crystalline silicon substrate 10 are, for example, alkaline etching such as a potassium hydroxide aqueous solution (KOH aqueous solution). It can be formed using a liquid. In this case, the n-type crystalline silicon substrate 10 having the (100) plane is anisotropically etched with an alkaline etching solution to form the first concavo-convex structures 11a and 12a having the pyramidal (111) plane. it can.

  Further, in order to improve the consistency between the first intrinsic amorphous silicon film 21 and the second intrinsic amorphous silicon film 22, the first intrinsic amorphous silicon film 21 and the second intrinsic amorphous film are used. A predetermined oxidation treatment may be performed before forming the porous silicon film 22 to form an oxidation interface. As the predetermined oxidation treatment, it can be left in an atmosphere or humidity controlled atmosphere for a predetermined time, or an ozone water treatment, a hydrogen peroxide solution treatment, an ozonizer treatment or the like can be used as appropriate.

The first intrinsic amorphous silicon film 21, the second intrinsic amorphous silicon film 22, the p-type amorphous silicon film 23, and the n-type amorphous silicon film 24 are formed by plasma chemical vapor deposition, thermal chemistry. It can be formed by methods such as vapor deposition, photochemical vapor deposition, and sputtering. For plasma chemical vapor deposition, any method such as an RF plasma method, a VHF plasma method, or a microwave plasma method may be used. For example, when RF plasma chemical vapor deposition is used, a silicon-containing gas such as silane (SiH ₄ ), a p-type dopant-containing gas such as diborane (B ₂ H ₆ ), and an n-type dopant-containing gas such as phosphine (PH ₃ ). Is diluted with hydrogen and supplied, RF high frequency power is applied to a parallel plate electrode or the like to form plasma, and the plasma is supplied to the surface of the heated n-type crystalline silicon substrate 10. Note that the substrate temperature during film formation is preferably in the range of 150 ° C. to 250 ° C. The RF power density during film formation is preferably in the range of 1 mW / cm ² to 10 mW / cm ² .

  In the above embodiment, the first and second intrinsic amorphous silicon films 21 and 22 are provided between the n-type crystalline silicon substrate 10 and the p-type amorphous silicon film 23 and the n-type amorphous silicon film 24, respectively. However, the present invention is not limited to this. A p-type amorphous silicon film 23 or an n-type amorphous silicon film 24 may be provided directly on the n-type crystalline silicon substrate 10.

  In the above embodiment, an example in which one conductivity type is n-type and another conductivity type is p-type is shown, but the present invention is not limited to this, and one conductivity type is p-type and another conductivity type is n-type. It is good also as a type. In the above embodiment, an example in which the crystalline silicon substrate 10 is n-type, that is, one conductivity type has been described. However, the present invention is not limited to this, and may be p-type, that is, another conductivity type.

DESCRIPTION OF SYMBOLS 1 ... Solar cell 10 ... N-type crystalline silicon substrate 10a ... End surface 10b ... Uneven structure 11, 12 ... 1st, 2nd main surface 11a, 12a ... 1st uneven structure 11b, 12b ... 2nd uneven structure 21, 22... First and second intrinsic amorphous silicon films 23... P-type amorphous silicon film 24... N-type amorphous silicon films 25 and 33. Layer 40 ... Laser S ... Rim

Claims (3)

A one-conductivity type crystalline silicon substrate having a first main surface ;
An amorphous silicon film of another conductivity type provided on the first main surface;
A first transparent electrode layer provided on the amorphous silicon film of the other conductivity type ,
The first transparent electrode layer is a solar cell in contact with the crystalline silicon substrate and the other conductive type amorphous silicon film . The solar cell according to claim 1, wherein the first transparent electrode layer is in contact with the crystalline silicon substrate at a peripheral edge of the crystalline silicon substrate. The solar cell according to claim 1, further comprising a first intrinsic amorphous silicon film between the crystalline silicon substrate and the other conductivity type amorphous silicon film.

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