JP2016058408A - Photovoltaic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photovoltaic device enhanced in reliability.SOLUTION: A photovoltaic device 100 has a second conduction type layer 26, a base layer 12 provided on the second conduction type layer 26, a first metal electrode 20 provided on the base layer 12, a through-hole 36 penetrating through the first metal electrode 20 and the base layer 12, an insulation layer 22 which is provided on substantially the whole surface of the first metal electrode 20 and covers the inner wall of the through-hole 36, and a second metal electrode 30 provided on the insulation layer 22. The second metal electrode 30 contacts the second conduction type layer 26 through the through-hole 36 covered with the insulation layer 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photovoltaic device.

  Photovoltaic elements that convert light energy into electrical energy have been vigorously developed in various fields. For example, research and practical application of photovoltaic elements or photovoltaic devices using crystalline silicon such as single crystal silicon and polycrystalline silicon have been actively conducted.

  In recent years, as a photovoltaic element that has increased the light receiving area of the light incident surface to increase the power conversion efficiency, a through-hole that penetrates from the light receiving surface that is the light incident surface to the back surface that faces the light receiving surface is formed. A photovoltaic element having a metal wrap-through structure that draws output power obtained from the side to the back side through a through hole has attracted attention. As a method of manufacturing such a type of photovoltaic device, a method is provided in which a through-hole is provided in a single crystal silicon layer that generates photovoltaic power, and a heterojunction of an amorphous silicon layer is formed on a part of the inner wall of the through-hole Is known (see, for example, Patent Document 1).

JP 2010-80885 A

  In a photovoltaic device having a metal wrap-through structure, the through hole is generally embedded with a metal material, but this metal material contacts the region other than the light receiving surface on the wall surface forming the through hole or the back surface of the photovoltaic device. If this happens, the positive and negative electrodes may be short-circuited and the output characteristics may be greatly impaired.

  The present invention has been made in view of these problems, and an object thereof is to provide a photovoltaic device with improved reliability.

  In order to solve the above problems, a photovoltaic device according to an aspect of the present invention includes a conductive layer, a base layer provided on the conductive layer, a first electrode provided on the base layer, A through-hole penetrating one electrode and the base layer, an insulating layer provided so as to cover substantially the entire surface of the first electrode and covering an inner wall of the through-hole, and a second electrode provided on the insulating layer. . The second electrode is in contact with the conductive type layer through the through hole.

  According to the present invention, a photovoltaic device with improved reliability can be provided.

It is sectional drawing which shows the structure of the photovoltaic apparatus in 1st Embodiment. It is the external view which looked at the photovoltaic apparatus of FIG. 1 from the back surface. It is the external view which looked at the photovoltaic apparatus of FIG. 1 from the light-receiving surface. It is a figure which shows the material board | substrate with which the base layer was formed. It is a figure which shows the material board | substrate with which the 1st i-type layer and the 1st conductivity type layer were formed. It is a figure which shows the material board | substrate with which the 1st transparent electrode layer and the 1st metal electrode were formed. It is a figure which shows the state in which the 1st hole which penetrates from a 1st metal electrode to a 1st i-type layer was formed. It is a figure which shows the state in which the 2nd hole which penetrates a base layer was formed. It is a figure which shows a mode that the inner wall of a 1st hole and a 2nd hole is dry-etched. It is a figure which shows the state in which the insulating layer was formed. It is a figure which shows the state which isolate | separated the material board | substrate. It is a figure which shows the state in which the 2nd i-type layer, the 2nd conductivity type layer, and the 2nd transparent electrode layer were formed. It is a figure which shows the state in which the 2nd metal electrode and the tab electrode were formed. It is sectional drawing which shows the structure of the photovoltaic apparatus in 2nd Embodiment. It is the external view which looked at the photovoltaic apparatus of FIG. 14 from the back surface. It is a figure which shows a mode that a several photovoltaic element is sealed with a protective substrate and a back sheet.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate.

<First Embodiment>
FIG. 1 is a cross-sectional view showing the structure of the photovoltaic device 100 according to the first embodiment. The photovoltaic device 100 includes a photovoltaic element 70 and a tab electrode 80 for taking out the electric power generated by the photovoltaic element 70 to the outside. The photovoltaic element 70 includes a first metal electrode 20 and a second metal electrode 30 provided on the back surface 70b side facing the light receiving surface 70a on which light (sunlight) A is incident as an electrode for taking out the generated electric power to the outside. Prepare. The second metal electrode 30 has a second conductive type layer 26 and a second transparent electrode layer 28 formed on the light receiving surface 70a side through a through hole 36 penetrating the light receiving surface 70a and the back surface 70b of the photovoltaic element 70. Connected. Thus, the photovoltaic device 100 has a metal wrap-through structure that can draw the power from the light receiving surface 70a side to the back surface 70b side through the second metal electrode 30 filling the through hole 36.

  The photovoltaic element 70 includes a base layer 12, a first i-type layer 14, a first conductivity type layer 16, a first transparent electrode layer 18, a first metal electrode 20, an insulating layer 22, a first layer 2 i-type layer 24, second conductivity type layer 26, second transparent electrode layer 28, and second metal electrode 30.

The base layer 12 is a crystalline semiconductor layer, for example, a single crystal semiconductor layer or a polycrystalline semiconductor layer in which a large number of crystal grains are aggregated. Here, an n-type crystalline silicon substrate to which an n-type dopant is added is used as the base layer 12, and the doping concentration is about 10 ¹⁶ / cm ³ . Further, the base layer 12 is provided with a texture structure on the light receiving surface 70a side for improving the efficiency of absorbing light incident on the photovoltaic element 70. By providing the texture structure, the traveling direction of light incident on the photovoltaic element 70 can be changed, and the optical path length of the light incident on the base layer 12 can be increased.

The first i-type layer 14 and the first conductivity type layer 16 are amorphous semiconductor layers, and are semiconductor layers including an amorphous phase or a microcrystalline phase in which minute crystal grains are precipitated in the amorphous phase. is there. Here, amorphous silicon containing hydrogen is used. The first i-type layer 14 is substantially intrinsic amorphous silicon, and the first conductivity type layer 16 is amorphous silicon to which an n-type dopant is added. The first conductivity type layer 16 is made of silicon having a dopant concentration higher than that of the first i-type layer 14. For example, the first i-type layer 14 is not intentionally doped, and the dopant concentration of the first conductivity type layer 16 may be about 10 ¹⁸ / cm ³ .

  The thickness of the first i-type layer 14 is desirably as thin as possible in order to suppress light absorption as much as possible, and is preferably set to such an extent that the surface of the base layer 12 is sufficiently passivated. Specifically, the thickness of the first i-type layer 14 may be 1 nm or more and 50 nm or less, for example, 10 nm. The first conductivity type layer 16 is preferably as thin as possible in order to suppress light absorption as much as possible, and is preferably thick enough to increase the open circuit voltage of the photovoltaic element 70 sufficiently. Specifically, the thickness of the first conductivity type layer 16 may be, for example, 1 nm or more, for example, 200 nm.

The second i-type layer 24 and the second conductivity type layer 26 are amorphous semiconductor layers, and are semiconductor layers including an amorphous phase or a microcrystalline phase in which minute crystal grains are precipitated in the amorphous phase. Yes, here it is assumed to be amorphous silicon containing hydrogen. The second i-type layer 24 is substantially intrinsic amorphous silicon, and the second conductivity type layer 26 is amorphous silicon to which a p-type dopant is added. The second conductivity type layer 26 is a silicon layer having a dopant concentration higher than that of the second i-type layer 24. For example, the second i-type layer 24 is not intentionally doped, and the dopant concentration of the second conductivity type layer 26 may be about 10 ¹⁸ / cm ³ .

  The thickness of the second i-type layer 24 may be thick enough that the surface of the base layer 12 is sufficiently passivated. Specifically, the thickness of the second i-type layer 24 may be 1 nm or more, for example, 10 nm. Further, the thickness of the second conductivity type layer 26 is preferably set such that the open circuit voltage of the photovoltaic element 70 becomes sufficiently high. The thickness of the second conductivity type layer 26 may be 1 nm or more and 50 nm or less, for example, 10 nm.

  The first i-type layer 14 and the first conductivity type layer 16 form a heterojunction on the back surface 70b side, and the second i-type layer 24 and the second conductivity type layer 26 form a heterojunction on the light receiving surface 70a side. Form. Thereby, a built-in potential is formed in the photovoltaic device 70.

The first transparent electrode layer 18 and the second transparent electrode layer 28 are made of tin oxide (SnO ₂ ), zinc oxide (ZnO), indium tin oxide (ITO), etc., tin (Sn), antimony (Sb), fluorine (F ), Transparent conductive oxide (TCO) doped with aluminum (Al) or the like, it is preferable to use at least one kind or a combination of plural kinds. In particular, zinc oxide (ZnO) has advantages such as high translucency and low resistivity. The film thicknesses of the first transparent electrode layer 18 and the second transparent electrode layer 28 may be 10 nm or more and 500 nm or less, for example, 100 nm.

  Note that an antireflection film for reducing the reflectance of the incident light A may be formed on the second transparent electrode layer 28 provided on the light receiving surface 70a side.

  The first metal electrode 20 and the second metal electrode 30 are electrodes for taking out the electric power generated by the photovoltaic element 70 to the outside. For example, nickel (Ni), iron (Fe), aluminum (Al), copper (Cu), silver (Ag) or an alloy thereof, or a paste containing these metal particles. Since the first metal electrode 20 serves as a temporary support substrate in the manufacturing process described later, the thickness of the first metal electrode 20 is desirably 50 μm or more.

  2 is an external view of the photovoltaic device 100 of FIG. 1 viewed from the back surface 70b, and FIG. 3 is an external view of the photovoltaic device 100 of FIG. 1 viewed from the light receiving surface 70a. The second metal electrode 30 is provided on the back surface 70b side of the photovoltaic element 70, and is provided so as to fill a plurality of through holes 36 penetrating the light receiving surface 70a and the back surface 70b of the photovoltaic element 70. The plurality of through holes 36 filled with the second metal electrode 30 are arranged apart from each other in order to increase the current collection efficiency of the second metal electrode 30. Note that the thickness of the second metal electrode 30 is desirably 10 μm or more in order to reduce the electric resistance.

  As shown in FIG. 2, the second metal electrode 30 is formed on the back surface 70 b side so as to cover a region C <b> 1 where a plurality of through holes 36 are arranged. Further, as shown in FIG. 1, the first metal electrode 20 is formed so as to cover a region other than the region C <b> 1 where the plurality of through holes 36 are arranged. For this reason, the back surface 70 b side of the photovoltaic element 70 is substantially entirely covered with the first metal electrode 20 or the second metal electrode 30. Thereby, even if light incident from the light receiving surface 70a of the photovoltaic element 70 passes through the base layer 12 only once and is not sufficiently absorbed, the first metal electrode 20 formed on the back surface 70b side and It is reflected by the second metal electrode 30 and passes through the base layer 12 again. Therefore, compared with the case where the substantially entire surface on the back surface 70b side is not covered by the first metal electrode 20 or the second metal electrode 30, more light is reflected on the base layer 12 and the light absorption amount of the base layer 12 is increased. Can be increased.

The insulating layer 22 is provided so as to cover substantially the entire surface of the first metal electrode 20 and to form the inner wall of the through hole 36, and the second metal electrode 30 includes the base layer 12, the first i-type layer 14, The first conductivity type layer 16, the first transparent electrode layer 18, and the first metal electrode 20 are insulated so as not to contact each other. The insulating layer 22 is made of an electrically insulating material, and is preferably a transparent material that does not absorb light in order to increase the light absorption amount of the base layer 12. The insulating layer 22 may be, for example, silicon oxide (SiO ₂ ), silicon nitride (SiN), aluminum oxide (Al ₂ O ₃ ), or a resin material, and the film thickness may be, for example, 100 nm or more and 1 μm or less. . The insulating layer 22 may not be formed in the region where the tab electrode 80 is provided so that power can be taken out from the first metal electrode 20 to the outside.

  In the present embodiment, the second transparent electrode layer 28 of the photovoltaic element 70 becomes the light receiving surface 70a. Here, the light receiving surface means a main surface on which light (sunlight) A is mainly incident on the photovoltaic element 70, and specifically, a large amount of light A incident on the photovoltaic element 70. This is the surface on which the part is incident.

Next, a method for manufacturing the photovoltaic device 100 will be described.
FIG. 4 is a diagram showing the material substrate 10 on which the base layer 12 is formed. The material substrate 10 is a crystalline semiconductor material, for example, a semiconductor substrate such as silicon, polycrystalline silicon, gallium arsenide (GaAs), or indium phosphide (InP). Note that in this embodiment, an example in which a single crystal silicon substrate is used as the material substrate 10 is described. Accordingly, the base layer 12, the first i-type layer 14, the first conductivity type layer 16, the second i-type layer 24, and the second conductivity type layer 26 described later are also silicon layers. However, the material substrate 10 may be made of a material other than silicon, and these layers may be made of materials other than the silicon layer.

The porous layer (brittle layer) 10a is formed by anodizing the material substrate 10 or the like. The electrolyte used for anodization can be, for example, a mixed solution of hydrofluoric acid and ethanol, or a mixed solution of hydrofluoric acid and hydrogen peroxide solution. The current density of the anodization may be a 5 mA / cm ² or more 600 mA / cm ² or less, for example, 10 mA / cm ² approximately.

  The thickness of the porous layer 10a may be 0.01 μm or more and 30 μm or less, for example, about 10 μm. The pore diameter of the porous layer 10a may be 0.002 μm or more and 5 μm or less, for example, about 0.01 μm. The porosity of the porous layer 10a may be 10% or more and 70% or less, for example, about 20%.

A base layer 12 is formed on the porous layer 10 a of the material substrate 10. The base layer 12 can be formed by chemical vapor deposition (CVD). The base layer 12 is formed by epitaxial growth using the porous layer 10a as a seed layer, and forms a homojunction region in which crystalline semiconductor layers are joined to each other. For example, the film formation can be performed by heating the material substrate 10 to 950 ° C. and supplying dichlorosilane (SiH ₂ Cl ₂ ) diluted with hydrogen (H ₂ ) as a source gas. The flow rates of hydrogen (H ₂ ) and dichlorosilane (SiH ₂ Cl ₂ ) are, for example, 0.5 (l / min) and 180 (l / min), respectively. Further, if necessary, phosphine (PH ₃ ) is added as a doping gas.

  Although not shown, a texture structure is formed on the surface 12 a of the base layer 12. The material substrate 10, the porous layer 10a, and the base layer 12 are chemically etched in an aqueous solution of sodium hydroxide (NaOH) to form a texture structure having a fine uneven shape on the surface 12a of the base layer 12. In addition, it is desirable to control the uneven shape of the texture structure by changing the concentration of NaOH aqueous solution used for etching, reaction time, or the like.

Note that a substrate made of a material other than silicon, such as sapphire (Al ₂ O ₃ ), may be used as the material substrate 10. In this case, it is not necessary to form the porous layer 10a on the material substrate 10. Instead of providing the porous layer 10a, a fine texture structure is provided on the sapphire substrate, and the base layer 12 is epitaxially grown on the surface to thereby form the surface. The base layer 12 in which the texture structure is formed can be obtained.

  FIG. 5 is a diagram showing the material substrate 10 on which the first i-type layer 14 and the first conductivity type layer 16 are formed. A first i-type layer 14 and a first conductivity type layer 16 are sequentially formed on the base layer 12.

The first i-type layer 14 and the first conductivity type layer 16 can be formed by plasma enhanced chemical vapor deposition (PECVD) using a silicon-containing gas such as silane (SiH ₄ ). While supplying a silicon-containing gas such as silane (SiH ₄ ) and supplying high-frequency power from a high-frequency power source to a high-frequency electrode, a raw material gas plasma is generated, and the raw material is supplied from the plasma onto the base layer 12 to form a silicon thin film. Is formed. The source gas is mixed with a dopant-containing gas such as phosphine (PH ₃ ) as necessary.

  FIG. 6 is a diagram showing the material substrate 10 on which the first transparent electrode layer 18 and the first metal electrode 20 are formed. The first transparent electrode layer 18 can be formed by a thin film forming method such as sputtering or plasma enhanced chemical vapor deposition (PECVD). In the first metal electrode 20, a metal layer made of an alloy of nickel and iron is formed by a plating method.

  FIG. 7 is a diagram illustrating a state in which the first hole 32 penetrating from the first metal electrode 20 to the first i-type layer 14 is formed. By irradiating the first laser electrode 60 from above the first metal electrode 20, the first hole 32 penetrating from the first metal electrode 20 to the first i-type layer 14 and exposing the base layer 12 is formed. Form. The irradiation condition of the first laser 60 is, for example, a pulsed focused laser beam having a wavelength of 355 nm, a repetition frequency of 250 kHz, a power of 0.90 W, and a pulse energy of 3.6 μJ. By irradiating the region C1 having a diameter of 50 μm from above the first metal electrode 20, the first hole 32 having a diameter of about 45 μm penetrating from the first metal electrode 20 to the first i-type layer 14 is formed. Can do.

  FIG. 8 is a diagram illustrating a state in which the second hole penetrating the base layer 12 is formed. By irradiating the inside of the first hole 32 with the second laser 62, the second hole 34 penetrating the base layer 12 and exposing the porous layer 10a is formed. The irradiation condition of the second laser 62 is, for example, a pulsed focused laser beam having a wavelength of 1064 nm, a repetition frequency of 15 kHz, a power of 25 W, and a pulse energy of 1.7 mJ. By irradiating the region C2 having a diameter of 40 μm of the base layer 12 exposed through the first hole 32, a second hole 34 having a diameter of about 30 μm that penetrates the base layer 12 and reaches the surface of the porous layer 10a is formed. To do.

FIG. 9 is a diagram showing how the inner walls of the first hole 32 and the second hole 34 are dry-etched. When forming the first hole 32 and the second hole 34 described above, scattered matter called so-called debris is generated from the irradiation region of the laser beam, and the inner walls of the first hole 32 and the second hole 34 and the first metal are formed. It adheres to the upper surface 20a of the electrode 20. If such a deposit causes a short circuit between the layers formed between the base layer 12 and the first metal electrode 20, the output characteristics of the photovoltaic device 70 will be degraded. Therefore, after forming the first hole 32 and the second hole 34, they are exposed to the plasma gas 64 of carbon tetrafluoride and oxygen (CF ₄ + O ₂ ) from above the first metal electrode 20. The kimono is dry-etched to clean the inner walls of the first hole 32 and the second hole 34 and the upper surface 20a of the first metal electrode 20. Note that the gas used for etching is not limited to CF ₄ + O ₂ , and nitrogen trifluoride (NF ₃ ), sulfur hexafluoride (SF ₆ ), or the like may be used.

FIG. 10 is a diagram illustrating a state in which the insulating layer 22 is formed. The insulating layer 22 is formed so as to cover the upper surface 20a of the first metal electrode 20 and the inner walls of the first hole 32 and the second hole 34 from above the first metal electrode 20 that has been dry-etched. The insulating layer 22 is a silicon nitride layer having a thickness of about 200 nm, and is supplied by plasmaizing a raw material gas in which silane (SiH ₄ ) and hydrogen (H ₂ ) are mixed with nitrogen (N ₂ ) or ammonia (NH ₃ ). It can be formed by plasma enhanced chemical vapor deposition (PECVD). As a result, a side surface portion 22 a that covers the inner walls of the first hole 32 and the second hole 34 and a bottom surface portion 22 b that covers the surface of the porous layer 10 a exposed by the second hole 34 are formed. Note that the insulating layer 22 is not formed by applying a mask to a partial region C3 of the first metal electrode 20 so that the tab electrode 80 for taking out power from the first metal electrode 20 to the outside can be connected. .

  FIG. 11 is a diagram illustrating a state where the material substrate 10 is separated. The base layer 12 side and the material substrate 10 side are mechanically separated from each other with the porous layer 10a as a boundary. At this time, the diameter of the second hole 34 is about 30 μm, whereas the film thickness of the insulating layer 22 is about 200 nm, which is extremely thin with respect to the diameter of the second hole 34, and thus the diameter above the porous layer 10 a. The bottom surface portion 22b formed in the range of about 30 μm remains on the material substrate 10 side. For this reason, the bottom surface portion 22b formed on the porous layer 10a is cut off from the side surface portion 22a, and the through hole 36 is formed by the side surface portion 22a covering the first hole 32 and the second hole 34.

  In the separation process of the material substrate 10, for example, the material substrate 10 and the insulating layer 22 can be separated from the porous layer 10 a portion by adsorbing the material substrate 10 and the insulating layer 22 with a vacuum chuck and pulling them apart. In addition, the insulating layer 22 and the material substrate 10 are respectively fixed to different temporary support bases with an adhesive or tape, and separated by applying external force to these temporary support bases, and then the adhesive, Alternatively, the tape may be removed. Further, the material substrate 10 can be separated from the porous layer 10a portion by spraying a water jet from the side surface of the material substrate 10 onto the porous layer 10a.

FIG. 12 is a diagram showing a state in which the second i-type layer 24, the second conductivity type layer 26, and the second transparent electrode layer 28 are formed, and these layers are base layers provided with through holes 36. 12 are formed in order. Similar to the first i-type layer 14 and the first conductivity type layer 16, the second i-type layer 24 and the second conductivity type layer 26 are plasma chemical vapors using a silicon-containing gas such as silane (SiH ₄ ). It can be formed by a phase method (PECVD). The source gas is mixed with a dopant-containing gas such as diborane (B ₂ H ₆ ) as necessary.

  Similar to the first transparent electrode layer 18, the second transparent electrode layer 28 can be formed by a thin film formation method such as sputtering or plasma enhanced chemical vapor deposition (PECVD). In addition, after forming the second transparent electrode layer 28, an antireflection layer having a refractive index smaller than that of the second transparent electrode layer 28 may be formed on the second transparent electrode layer 28. In this case, it is desirable to form the antireflection film at a temperature of 250 ° C. or lower so as not to affect the already formed heterojunction.

  The film thicknesses of the second i-type layer 24, the second conductivity type layer 26, and the second transparent electrode layer 28 are extremely thin compared to the diameter of the through-hole 36. Even if the layer is formed, the through hole 36 is not buried. As a result, the through hole 36 penetrates from the insulating layer 22 to the second transparent electrode layer 28.

  FIG. 13 is a diagram illustrating a state in which the second metal electrode 30 and the tab electrode 80 are formed. For the second metal electrode 30, a metal mask having an opening corresponding to the region C1 where the first metal electrode 20 is not formed is disposed on the insulating layer 22, and a CVD method with high adhesion to the wall surface from above is used. It is formed by a sputtering method. Thus, the inside of the through hole 36 is filled, and the second metal electrode 30 is formed so as to cover a partial region C1 of the insulating layer 22. The second metal electrode 30 is connected to the second conductivity type layer 26 and the second transparent electrode layer 28 on the light receiving surface 70 a side through the through hole 36. In addition, you may form the 2nd metal electrode 30 so that the through-hole 36 may be embedded by the method of screen-printing a metal paste. Finally, the tab electrode 80 is provided in the region C3 where the first metal electrode 20 is exposed.

  By the manufacturing method described above, the photovoltaic device 100 has the first metal electrode 20 and the second metal electrode 30 formed on the back surface 70b side, and the second conductivity type layer on the light receiving surface 70a side through the through hole 36. 26 and a second metal electrode 30 connected to the second transparent electrode layer 28 is provided. As a result, there is no need to form a collecting electrode on the light receiving surface 70a, so that the light receiving area of the light receiving surface 70a can be increased compared with the case where the collecting electrode is formed on the light receiving surface 70a, and the power conversion efficiency Can be increased.

  The second metal electrode 30 is electrically insulated from each layer provided between the base layer 12 and the first metal electrode 20 by the insulating layer 22 covering the through hole 36 and the first metal electrode 20. It will be. For this reason, it prevents that the area | region other than the 2nd i-type layer 24, the 2nd conductivity type layer 26, and the 2nd transparent electrode layer 28 provided in the light-receiving surface 70a side contacts the 2nd metal electrode 30. Therefore, a highly reliable metal wrap-through structure can be obtained.

  Further, since the first metal electrode 20 and the second metal electrode 30 are formed on different planes with the insulating layer 22 interposed therebetween, it is not necessary to make one of the metal electrodes comb-like or the like, as shown in FIG. In addition, a metal electrode having a large area can be obtained. For this reason, an electrode structure can be manufactured simply and cost increase can be prevented.

  In addition, since the second metal electrode 30 is formed so as to cover the region C1 where the first metal electrode 20 is not formed, the back surface 70b side of the photovoltaic element 70 is connected to the first metal electrode 20 or the first metal electrode 20. It will be covered with either of the two metal electrodes 30. As a result, even if a part of the incident light, for example, the light is transmitted to the back surface 70b side, either the first metal electrode 20 or the second metal electrode 30 reflects the transmitted light and directs it to the photovoltaic element 70 again. A confinement effect can be obtained and power conversion efficiency can be increased.

<Second Embodiment>
FIG. 14 is a cross-sectional view showing the structure of the photovoltaic device 200 according to the second embodiment. Hereinafter, the difference from the photovoltaic device 100 in the first embodiment will be mainly described.

  The photovoltaic device 200 includes a plurality of photovoltaic elements 70 shown in the first embodiment and is connected to each other by a tab electrode 80. FIG. 15 is an external view of the photovoltaic device 200 of FIG. 14 as viewed from the back surface 70 b, and shows a state in which a plurality of photovoltaic elements 70 are connected by tab electrodes 80. As shown in FIG. 15, the tab electrode 80 connects a plurality of photovoltaic elements 70 in series by connecting the first metal electrode 20 and the second metal electrode 30 of the adjacent photovoltaic elements 70. In the present embodiment, since both the first metal electrode 20 and the second metal electrode 30 are provided on the back surface 70b side of the photovoltaic element 70, a plurality of photovoltaic elements 70 are simply connected by the tab electrode 80. be able to.

  Returning to FIG. 14, the photovoltaic device 200 includes a protective substrate 40, a protective layer 42, and a back sheet 50. The protective substrate 40 protects the photovoltaic element 70 from the external environment and transmits light in a wavelength band that the photovoltaic element 70 absorbs for power generation. The protective substrate 40 is, for example, a glass substrate. In addition, since the light receiving surface 70a of the photovoltaic element 70 in the present embodiment is formed flat without an electrode formed in a comb shape, the protective substrate 40 is disposed so as to be in contact with the light receiving surface 70a. Can do. Thereby, since the adhesive for bonding the light receiving surface 70a and the protective substrate 40 can be omitted, the absorption loss of incident light by the adhesive can be prevented, and the power conversion efficiency can be increased.

  The protective layer 42 and the back sheet 50 are resin materials such as EVA and polyimide. Thereby, while preventing the penetration | invasion of the water | moisture content to the electric power generation layer of the photovoltaic apparatus 200, the intensity | strength of the photovoltaic apparatus 200 whole is improved. The back sheet 50 may be the same glass as the protective substrate 40 or a transparent substrate such as plastic. Further, by providing a reflective layer between the protective layer 42 and the back sheet 50 so that a large amount of light incident from the protective substrate 40 side is absorbed by the base layer 12, the back sheet is transmitted through the photovoltaic device 70. The light reaching 50 may be reflected to the photovoltaic element 70.

Next, a method for manufacturing the photovoltaic device 200 will be described.
FIG. 16 is a diagram showing a state in which a plurality of photovoltaic elements 70 are sealed with the protective substrate 40 and the back sheet 50. After a plurality of photovoltaic elements 70 manufactured by the steps shown in FIGS. 4 to 13 are connected in series by the tab electrode 80, the protective substrate 40 is disposed on the light receiving surface 70a side, and the protective layer 42 is sandwiched on the back surface 70b side. Thus, the back sheet 50 is arranged. Thereafter, the photovoltaic device 70 shown in FIG. 14 is removed by thermocompression bonding with the photovoltaic element 70 sandwiched between the protective substrate 40 and the backsheet 50 and by removing the protective layer 42 protruding from the protective substrate 40. It is formed.

  With the above manufacturing method, the photovoltaic device 200 includes a plurality of photovoltaic elements 70 that are modularized, the protective substrate 40 is on the light receiving surface side, and the first metal electrode 20 and the second metal electrode 30 are on the back surface side. Will be provided. Moreover, it has a metal wrap through structure in which the second metal electrode 30 connected to the second transparent electrode layer 28 on the light receiving surface 70a side through the through hole 36 is provided. Thereby, the effect similar to 1st Embodiment can be acquired.

  As described above, the present invention has been described with reference to the above-described embodiments. However, the present invention is not limited to the above-described embodiments, and the configurations of the embodiments are appropriately combined or replaced. Those are also included in the present invention. Further, it is possible to appropriately change the combination and processing order in each embodiment based on the knowledge of those skilled in the art and to add various modifications such as various design changes to each embodiment. Embodiments to which is added can also be included in the scope of the present invention.

  In the above-described embodiment, the metal electrode is not provided on the second transparent electrode layer 28 on the light receiving surface 70a side, but the metal electrode formed in a comb shape is formed on the second transparent electrode layer 28. May be. In this case, the light receiving area is reduced by the amount of the metal electrodes formed in a comb shape, but the current collection efficiency on the light receiving surface 70a side can be increased.

  In the above-described embodiment, the case where the second metal electrode 30 is formed so as to cover the region C1 in which the plurality of through holes 36 are arranged has been described. However, the second metal electrode 30 covers a region other than the region C1. It may be formed as follows. For example, the second metal electrode 30 may be formed so as to cover a region slightly wider than the region C1, and the second metal electrode 30 may overlap the first metal electrode 20 with the insulating layer 22 interposed therebetween. Further, the second metal electrode 30 may be formed so as to cover substantially the entire surface of the insulating layer 22. Thus, by forming an electrode so that at least a partial region of the second metal electrode 30 overlaps the first metal electrode 20, the light confinement effect can be further enhanced.

  In addition, the photovoltaic device by the following combinations can also be included in the scope of the present invention.

  (1) A photovoltaic device includes a conductive layer, a base layer provided on the conductive layer, a first electrode provided on the base layer, and a through-hole penetrating the first electrode and the base layer. And an insulating layer which covers the substantially entire surface of the first electrode and covers the inner wall of the through hole, and a second electrode which is provided on the insulating layer. The second electrode is in contact with the conductive type layer through the through hole.

  According to this aspect, since it can be set as the structure which does not provide an electrode on the conductive type layer used as a light-receiving surface, the light-receiving area of a light-receiving surface can be enlarged and power conversion efficiency can be improved. The first electrode is substantially entirely covered with an insulating layer, and the second electrode is in contact with the conductive type layer through a through hole covered with the insulating layer, so that the first electrode, the base layer, the second electrode, It is possible to secure electrical insulation between them and to improve the reliability of the photovoltaic device.

  (2) The first electrode has a transparent electrode layer provided on the base layer and a metal electrode provided on the transparent electrode layer, and the second electrode is formed on the metal electrode with the insulating layer interposed therebetween. The photovoltaic device according to (1) may have a region overlapping with.

  According to this aspect, the first electrode, which is a metal electrode, is formed on the base layer, and the second electrode is provided so as to overlap the first electrode. It is formed so as to cover the entire surface. For this reason, even if light incident from the conductive layer serving as the light receiving surface is transmitted to the back side without being absorbed by the base layer, it can be reflected by the electrode formed on the back side and be directed again to the base layer. . As a result, the photoelectric conversion efficiency can be increased as compared with the case where the electrode is not formed on substantially the entire back surface side.

  (3) A plurality of through holes are provided so as to be arranged apart from each other, and the second electrode is in contact with the conductive type layer via the plurality of through holes provided. The photovoltaic device may be used. The current collection efficiency by the second electrode can be increased by contacting the conductive type layer through the plurality of through holes in which the second electrode is arranged apart from each other.

  (4) The base layer is a crystalline silicon layer, and a heterojunction region including a substantially intrinsic amorphous silicon layer is formed in a region between the first electrode and the conductive type layer. A heterojunction region comprising an amorphous silicon layer that is highly doped compared to the base layer and is substantially intrinsic in the region between the base layer (1) to ( The photovoltaic device according to any one of 3) may be used.

  DESCRIPTION OF SYMBOLS 12 ... Base layer, 14 ... 1st i-type layer, 16 ... 1st conductivity type layer, 18 ... 1st transparent electrode layer, 20 ... 1st metal electrode, 22 ... Insulating layer, 24 ... 2nd i-type layer , 26 ... second conductivity type layer, 28 ... second transparent electrode layer, 30 ... second metal electrode, 36 ... through hole, 40 ... protective substrate, 42 ... protective layer, 50 ... back sheet, 70 ... photovoltaic element , 70a ... light receiving surface, 70b ... back surface, 80 ... tab electrode, 100, 200 ... photovoltaic device.

Claims (4)

A conductive layer;
A base layer provided on the conductive type layer;
A first electrode provided on the base layer;
A through-hole penetrating the first electrode and the base layer;
An insulating layer provided so as to cover substantially the entire surface of the first electrode, and covering an inner wall of the through hole;
A second electrode provided on the insulating layer;
With
The photovoltaic device according to claim 1, wherein the second electrode is in contact with the conductive layer through the through hole. The first electrode has a transparent electrode layer provided on the base layer, and a metal electrode provided on the transparent electrode layer,
2. The photovoltaic device according to claim 1, wherein the second electrode has a region overlapping the metal electrode with the insulating layer interposed therebetween. A plurality of the through holes are provided so as to be arranged apart from each other,
3. The photovoltaic device according to claim 1, wherein the second electrode is in contact with the conductive type layer through a plurality of the through holes. The base layer is a crystalline silicon layer, and a heterojunction region including a substantially intrinsic amorphous silicon layer is formed in a region between the first electrode and the first layer.
The conductive type layer is a layer doped more heavily than the base layer, and a heterojunction region including an amorphous silicon layer that is substantially intrinsic is formed in a region between the base layer and the base layer. The photovoltaic device according to claim 1, wherein the photovoltaic device is provided.

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