JP2007266096A - Solar cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell preventing a side leakage without forming an isolation trench increasing an ineffective area by a connecting section between photoelectric conversion layers and increasing a laser machining process. <P>SOLUTION: The solar cell has a power generation unit with at least two layers of the laminated photoelectric conversion layers 4 and 8 and intermediate regions 15 and 25 being interposed between the two layers of the photoelectric conversion layers 4 and 8 and electrically and optically connecting two layers of these photoelectric conversion layers. In the solar cell, the intermediate regions contain small regions 16 and 26 electrically dispersed discontinuously in the extension direction of two layers of the photoelectric conversion layers. Such a solar cell is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multijunction solar cell in which a plurality of photoelectric conversion layers are stacked, a manufacturing method thereof, and an integrated solar cell in which a plurality of multijunction photoelectric conversion cells in which a plurality of photoelectric conversion layers are stacked are connected. .

A so-called single cell solar cell is known that includes a power generation unit in which a lower electrode, a photoelectric conversion cell made of a single photoelectric conversion layer made of a semiconductor such as silicon, and an upper electrode are sequentially formed on an insulating substrate. This solar cell formed as a single cell has a drawback that long wavelength light having energy lower than the band gap of the semiconductor is transmitted or reflected without being absorbed by the semiconductor. In addition, short-wavelength light having energy larger than the band gap is absorbed and contributes to power generation, but excess energy beyond the band gap becomes heat and is not used. Therefore, there is a method of using a plurality of photoelectric conversion layers made of semiconductors having different band gaps in order to increase the efficiency of the solar cell. As described above, solar cells using a plurality of stacked photoelectric conversion layers include a tandem solar cell in which two photoelectric conversion layers having different absorption wavelength bands are stacked, and a triple solar cell in which three layers are stacked. As the tandem solar cell, a thin-film silicon tandem solar cell using a-Si (amorphous silicon) for the top cell on the sunlight incident side and crystalline Si or a-SiGe (amorphous silicon germanium) for the bottom cell on the back surface side, A thin film compound tandem solar cell using CuGaSe _{2 for} the top cell and CuIn _x Ga _1-x Se ₂ for the bottom cell is also known. As the triple solar cell, a thin-film silicon triple solar cell using a-SiC (amorphous silicon carbide) for the top cell, a-Si for the middle cell provided between the top cell and the bottom cell, and a-SiGe for the bottom cell, etc. Are known. Taking a tandem solar cell using a-Si as a top cell and crystalline Si (for example, microcrystalline silicon in which an amorphous phase is mixed) as a bottom cell as an example, a-Si on the sunlight incident side is short. Crystalline Si absorbs light of a wavelength and absorbs light of a long wavelength that is not absorbed. Since the top cell and the bottom cell are electrically in series, the same amount of current flows through both cells, but the current of the tandem solar cell is determined by a-Si, which has a small generated current. Although the current can be increased by increasing the film thickness of a-Si and increasing the amount of light absorption, there is a problem that the light deterioration increases. Therefore, the light having a short wavelength that cannot be absorbed by a-Si is transmitted and reflected by the transparent intermediate layer to the a-Si film side to make the optical path longer and absorbed, thereby increasing the film thickness of a-Si. The generated current can be increased.

This transparent intermediate layer is the same as the transparent electrode used for the lower electrode or the upper electrode on the light incident side of the solar cell, such as zinc oxide (ZnO), tin oxide (SnO ₂ ), and indium tin oxide (ITO). An object is a main component and is generally a low resistance film. The conductivity of the transparent metal oxide has the property of changing depending on the oxygen deficiency and doping element content.

The specific resistance of the transparent electrode is low, about 5 × 10 ⁻⁴ Ω · cm, but about two orders of magnitude higher than the specific resistance of the metal film used for the back electrode. Therefore, power loss occurs while the current generated in the cell flows through the transparent electrode. This is more noticeable as the substrate area becomes larger, and an integrated structure is known that reduces the loss in order to reduce the power that can be extracted to the outside. FIG. 3 is a schematic partial cross-sectional view of an integrated solar cell having such an integrated structure. In this integrated solar cell, a plurality of solar cells (power generation units) are formed on one substrate and connected in series.

  A lower electrode 52, a lower photoelectric conversion layer 53, a transparent intermediate layer 54, an upper photoelectric conversion layer 55, and an upper electrode 56 are formed as a laminated film on the insulating substrate 51, and these laminated films constitute a power generation film. A transparent electrode is used for the lower electrode 52 or the upper electrode 56 on the light incident side. The power generation film is divided into a plurality of power generation units by a lower electrode separation groove 57 and an upper electrode separation groove 59. Further, between the power generation units adjacent to each other, the lower electrode 52 of one power generation unit and the upper electrode 56 of the other power generation unit respectively extend and come into electrical contact with each other through the connection groove 58 so that the respective power generation units are connected in series. It is connected. This is to reduce the amount of current flowing through the transparent electrode by dividing the power generation film and reducing the area of one power generation unit, and by increasing the voltage by serialization, the loss is suppressed. The separation grooves and connection grooves are formed by laser scribing so as to extend in a direction perpendicular to the series connection direction (a direction perpendicular to the paper surface).

  The solar cell includes a super straight type in which sunlight enters from the lower side of FIG. 3 and a substrate type in which sunlight enters from the upper side of the figure. The super straight type solar cell includes a transparent substrate 51 such as glass, a transparent electrode used as the lower electrode 52, a top cell that absorbs a short wavelength region used as the lower photoelectric conversion layer 53, and an upper photoelectric conversion layer 55. A bottom cell that absorbs the long wavelength region used and a back electrode made of a metal film used as the upper electrode 56 are configured. In the substrate type solar cell, since the substrate 1 does not need to be transparent, a metal or a polymer film is also used in addition to glass. The substrate type solar cell is used as a substrate 51, a back electrode made of a metal film used as the lower electrode 52, a bottom cell that absorbs a long wavelength region used as the lower photoelectric conversion layer 53, and an upper photoelectric conversion layer 55. A top cell that absorbs a short wavelength region and a transparent electrode used as the upper electrode 56 are configured.

An integrated thin-film silicon tandem solar cell in which a transparent intermediate layer is inserted is disclosed in Patent Document 1, Patent Document 2, and the like. In these, the specific resistance value of the intermediate layer is defined, and 1 × 10 ⁻¹ Ω · cm or less is considered good. In FIG. 3, when the specific resistance of the intermediate layer 58 is low, if the extended portion of the upper electrode 56 covering the connection groove 58 is connected to the intermediate layer 54, it flows from the upper photoelectric conversion layer 55 to the lower photoelectric conversion layer 53. There is a problem that a part of the current should flow in the direction indicated by the arrow 60 in FIG. 3 and leak to the upper electrode 56 covering the connection groove 58 through the intermediate layer. This current leakage is called side leakage because it flows laterally along the film.

  An example of an integrated structure for preventing side leakage is disclosed in Patent Document 3. In this integrated structure, a separation groove 61 for removing the lower photoelectric conversion layer and the transparent intermediate layer is provided between the lower electrode separation groove 57 and the connection groove 58 in FIG. The current path flowing through is interrupted. However, in this integrated structure, an increase in the number of separation grooves 61 increases the area of the connection portion that does not contribute to power generation between the upper photoelectric conversion layer 55 and the lower photoelectric conversion layer 53, and an unnecessary laser processing apparatus is required. Problem arises.

JP 2001-274430 A JP 2002-118273 A JP 2002-261308 A

  The present invention has been made in view of such circumstances, and provides a solar cell that prevents side leakage without providing a separation groove that causes an increase in ineffective area due to a connection portion between photoelectric conversion layers and an increase in laser processing steps. The purpose is to do.

In order to solve the above problems, the present invention employs the following means.
That is, the solar cell according to the present invention is interposed between at least two stacked photoelectric conversion layers and the two photoelectric conversion layers, and the two photoelectric conversion layers are electrically and optically connected. The intermediate region includes small regions that are electrically discontinuously dispersed in the extending direction of the two photoelectric conversion layers.
In this solar cell, current flows in the thickness direction of the two photoelectric conversion layers in the intermediate region, but current does not flow in the extending direction of the layers. Therefore, a separation groove is provided in the intermediate region by laser processing or the like. Side leakage can be prevented.

  In the solar cell of the present invention, the small region may be an insulator having a conductivity lower than that of the two photoelectric conversion layers. Alternatively, the small region may be a conductor having a conductivity higher than that of the two photoelectric conversion layers. In the description of the present invention, “insulator” and “conductor” do not refer to materials having a specific conductivity range, but the conductivity of a photoelectric conversion layer in electrical contact with these materials. A material having a low conductivity is called an “insulator”, and a material having a high conductivity is called a “conductor”.

In the solar cell of the present invention, the intermediate region may have a region including an insulator around a small region made of a conductor.
Thus, a high light scattering effect can be obtained by configuring the small region and the surrounding region with different materials.

The solar cell of the present invention includes an insulating substrate and the power generation unit formed on the insulating substrate, and the power generation unit has a lower electrode on the insulating substrate side and an upper portion on the opposite side to the insulating substrate. It can be set as the structure which has an electrode.
The solar cell of the present invention includes an insulating substrate and a plurality of the power generation units formed on the insulating substrate, and each of the plurality of power generation units is provided on the insulating substrate side, and An upper electrode provided on the opposite side of the insulating substrate, and at least one of the plurality of power generation units is configured such that the upper electrode is electrically connected to a lower electrode of another adjacent power generation unit It can be.
In the solar cell of the present invention, since current does not easily flow in the extending direction of the photoelectric conversion layer in the intermediate region, it extends to the side of the power generation unit in order to electrically connect the upper electrode or lower electrode of the power generation unit to other units. Even if it exists, side leak does not occur in the upper electrode or the lower electrode from the end of the intermediate region.

  The method for producing a solar cell according to the present invention includes at least two photoelectric conversion layers stacked and the two photoelectric conversion layers interposed between the two photoelectric conversion layers electrically and optically. A method for manufacturing a solar cell having a power generation unit including an intermediate region to be connected, and after forming a first photoelectric conversion layer of the two photoelectric conversion layers, on the first photoelectric conversion layer A step of dispersively forming small regions made of an insulator having a conductivity lower than that of the two photoelectric conversion layers, and the photoelectric conversion of the two layers on the surface where the small regions are formed. Forming a second photoelectric conversion layer among the layers, and forming a small region in which the intermediate region is electrically discontinuously dispersed in the extending direction of the two photoelectric conversion layers. It is a method to make an area.

Alternatively, the method for manufacturing a solar cell according to the present invention is interposed between at least two stacked photoelectric conversion layers and the two photoelectric conversion layers, and the two photoelectric conversion layers are electrically and optically connected. A solar cell manufacturing method having a power generation unit with an intermediate region to be connected to the first photoelectric conversion layer after forming the first photoelectric conversion layer of the two photoelectric conversion layers. A step of dispersively forming a small region made of a conductor having a conductivity higher than that of the two photoelectric conversion layers on the layer; and a step of forming the two layers on the surface on which the small region is formed. Forming a second photoelectric conversion layer of the photoelectric conversion layer, and forming a small region in which the intermediate region is electrically discontinuously dispersed in the extending direction of the two photoelectric conversion layers It is a method to make it the area | region made.
According to any one of the solar cell manufacturing methods of the present invention, the intermediate region is a region in which small regions are formed that are electrically discontinuously dispersed in the extending direction of the two photoelectric conversion layers. Thus, a step of forming a separation groove in the intermediate region by laser processing or the like to prevent side leakage is unnecessary, and thus a solar cell can be manufactured easily and at low cost.

The step of forming the small region may include a step of applying a dispersion liquid in which fine particles made of the insulator or the conductor are dispersed in a dispersion medium.
In the step of forming the small region, the insulator or the conductor is formed on the first photoelectric conversion layer, and then the insulator or the conductor is dissolved with a solvent that dissolves the insulator. Alternatively, a step of removing a part of the layer made of the conductor may be included.
Alternatively, the step of forming the small region may include a step of forming the small region on the first photoelectric conversion layer through a mask having a plurality of discontinuous opening patterns.
By the process of forming these small regions, small regions that are electrically discontinuously dispersed in the extending direction of the two photoelectric conversion layers can be formed by a simple method.

In the solar cell manufacturing method of the present invention, when the small region is the conductor, a step of forming a region including an insulator around the small region in the intermediate region may be provided.
According to this manufacturing method, since the small region and the region including the insulator are formed from different materials, an enhanced light scattering effect can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the solar cell which prevented the side leak without providing the isolation groove which causes the increase in an ineffective area by the connection part between photoelectric conversion layers, and the increase in a laser processing process can be provided.

DESCRIPTION OF EMBODIMENTS Embodiments according to a solar cell and a manufacturing method thereof according to the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a schematic partial cross-sectional view showing the solar cell according to the first embodiment. In this solar cell, a lower electrode 2, a first photoelectric conversion layer 4, a second photoelectric conversion layer 8, and an upper electrode 10 are sequentially stacked on a transparent insulating substrate 1. In this solar cell, the first photoelectric conversion layer 4 absorbs short-wavelength light out of light incident from the transparent insulating substrate 1 side, and the second photoelectric conversion layer 8 absorbs long-wavelength light. It is a super straight tandem solar cell that absorbs and generates current. This solar cell further has an intermediate region 15 between the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8 for electrically and optically connecting the two photoelectric conversion layers 4 and 8. is doing.

The constituent elements of the solar cell of the present embodiment can be formed in the same manner as the constituent elements of a normal super straight tandem solar cell except for the intermediate region 15, but in the present embodiment, for example, as follows: Composed.
As the transparent insulating substrate 1, a plate-like insulating material having light transmittance is used, and for example, white plate glass is adopted.
As the lower electrode 2, a transparent electrode made of a conductive metal oxide thin film having optical transparency is used. For example, SnO ₂ is used as the metal oxide.
The first photoelectric conversion layer 4 and the second photoelectric conversion layer 8 are both semiconductor layers such as silicon having a pin junction or a nip junction. For example, the first photoelectric conversion layer 4 is made of amorphous silicon (a- Si) and the second photoelectric conversion layer 8 can be microcrystalline silicon (μc-Si).

The upper electrode 10 includes a transparent electrode 11 formed on the second photoelectric conversion layer 8 and a back electrode 12 formed on the transparent electrode 11. The transparent electrode 11 is made of a conductive metal oxide thin film having optical transparency, and SnO ₂ is used as the metal oxide, for example. Further, as the back electrode 12, an Ag film, an Al film, or the like is employed.

In the present embodiment, the intermediate region 15 includes a small region 16 discontinuously dispersed between the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8, and an interface between the photoelectric conversion layers 4 and 8. have. The small region 16 is formed of insulating fine particles having a lower conductivity than the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8.
As the insulating fine particles, those having optical transparency are preferable. For example, metal oxide fine particles such as SiO ₂ , TiO ₂ and ZnO, and fine particles made of other transparent insulating materials such as MgF ₂ may be adopted. it can. One of the small regions 16 may be composed of one insulating fine particle, or may be composed of an aggregate of the insulating fine particles. The size of the small region 16 is not particularly limited, but passes through the light reflected by the small region 16 and contributing to power generation in the first photoelectric conversion layer 4 and the interface between the small region 16 and the photoelectric conversion layers 4 and 8. Then, it is selected in consideration of the balance of light that contributes to power generation in the second photoelectric conversion layer 8, and the fact that current flow is not hindered in the layer thickness direction. For example, the thickness of the small region 16 can be 0.01 μm or more and 2 μm or less, and the coverage of the first photoelectric conversion layer 4 by the small region 16 can be 10% or more and 70% or less.

  The solar cell of this embodiment uses the lower electrode 2, the first photoelectric conversion layer 4, the intermediate region 15, the second photoelectric conversion layer 8, and the upper electrode 10 as one power generation unit, and a plurality of similar power generation units. Is formed on the transparent insulating substrate 1, and the plurality of power generation units are connected in series by electrically connecting the upper electrode 10 and the lower electrode 2 of the adjacent power generation units, thereby obtaining an integrated solar cell ( Module).

The solar cell of this embodiment is manufactured as follows, for example.
First, a transparent conductive film such as a SnO ₂ film is formed on a transparent insulating substrate by atmospheric pressure CVD to form the lower electrode 2. Next, a p-layer, an i-layer, and an n-layer made of amorphous silicon or the like are formed on the lower electrode 2 in this order or in reverse order by the plasma CVD method, thereby forming the first photoelectric conversion layer 4.
Next, a dispersion liquid in which the insulating fine particles having a particle size of 0.01 μm or more and 2 μm or less are dispersed in an appropriate dispersion medium is applied onto the first photoelectric conversion layer 4 by a spin coating method. By drying and removing the dispersion medium, discontinuously dispersed small regions 16 made of insulating fine particles are formed on the first photoelectric conversion layer 4.

Next, a p layer, an i layer, and an n layer made of microcrystalline silicon or the like are formed in this order or in reverse order on the first photoelectric conversion layer in which the small region 16 is formed by a plasma CVD method. Then, the second photoelectric conversion layer 8 is formed. A transparent conductive film such as a SnO ₂ film is formed on the second photoelectric conversion layer 8 by atmospheric pressure CVD to form the transparent electrode 11 of the upper electrode 10. Further, a metal thin film such as an Ag film is formed on the transparent electrode 11 by a sputtering method, a vacuum deposition method, or the like, thereby forming the back electrode 12. Thus, the solar cell of this embodiment is manufactured.

  In the solar cell of this embodiment, unlike the conventional intermediate layer made of a transparent transparent conductive film, the intermediate region 15 in which the small regions 16 made of an insulator are discontinuously dispersed is formed in the first photoelectric conversion layer 4 and Since it was formed between the second photoelectric conversion layers 8, current flows in the thickness direction of the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8, but current flows in the extending direction of these layers. Difficult to flow. Therefore, even if the solar cell is the integrated solar cell and the portion that electrically connects the upper electrode 10 and the lower electrode 2 is formed, for example, on the side portion of the power generation unit, no side leak occurs. Further, by dispersing the small regions 16 made of a light-transmitting insulator in the extending direction of the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8, the light scattering effect of incident light is enhanced, and the optical path A long increase effect can be obtained. Therefore, it is possible to effectively use incident light and increase power generation efficiency. In addition, since it is not necessary to provide a separation groove for preventing side leakage in the intermediate region 15, the area of the connection portion between the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8 that does not contribute to power generation is suppressed. Thus, the power generation efficiency can be increased.

  In addition, according to the method for manufacturing a solar cell of this embodiment, since a step of forming a separation groove in the intermediate region 15 by laser processing or the like is not required in order to prevent side leakage, the solar cell can be more easily performed at low cost. Can be manufactured.

[Modification of First Embodiment]
In the first embodiment, the small region 16 may be formed of conductive fine particles having a higher conductivity than the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8.
As the conductive fine particles, those having optical transparency are preferable. For example, transparent metal oxide fine particles such as gallium-doped zinc oxide (GZO) and indium tin oxide (ITO) can be employed. In the present modification, one of the small regions 16 may be composed of one conductor fine particle, or may be composed of an aggregate of the conductor fine particles. The size of the small region 16 is not particularly limited, but passes through the light reflected by the small region 16 and contributing to power generation in the first photoelectric conversion layer 4 and the interface between the small region 16 and the photoelectric conversion layers 4 and 8. Thus, it is selected in consideration of the balance of light that contributes to power generation in the second photoelectric conversion layer 8 and the fact that no current flows in the extending direction of the photoelectric conversion layers 4 and 8. For example, the thickness of the small region 16 can be 0.01 μm or more and 2 μm or less, and the coverage of the first photoelectric conversion layer 4 by the small region 16 can be 10% or more and 70% or less.

  In the solar cell manufacturing method of the present modification, the small region 16 is formed as follows, for example. First, a dispersion liquid in which the conductive fine particles having a particle diameter of 0.01 μm to 2 μm are dispersed in a suitable dispersion medium is applied onto the first photoelectric conversion layer 4 by a spin coating method. By removing the dispersion medium by drying, small regions 16 that are discontinuously dispersed of the conductive fine particles are formed on the first photoelectric conversion layer 4.

  In the solar cell of this modification, unlike the conventional intermediate layer made of a continuous transparent conductive film, the intermediate region 15 in which the small regions 16 made of a conductor are discontinuously dispersed is formed in the first photoelectric conversion layer 4 and Since it formed between the 2nd photoelectric converting layers 8, although an electric current flows through the thickness direction of the 1st photoelectric converting layer 4 and the 2nd photoelectric converting layer 8, the extension direction of these photoelectric converting layers 4 and 8 Current is difficult to flow through. Therefore, even if the solar cell is the integrated solar cell and the portion that electrically connects the upper electrode 10 and the lower electrode 2 is formed, for example, on the side portion of the power generation unit, no side leak occurs. Further, by dispersing the small regions 16 made of a light-transmitting conductor in the extending direction of the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8, the light scattering effect of incident light is enhanced, and the optical path A long increase effect can be obtained. Therefore, it is possible to effectively use incident light and increase power generation efficiency. In addition, since it is not necessary to provide a separation groove for preventing side leakage in the intermediate region 15, the area of the connection portion between the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8 that does not contribute to power generation is suppressed. Thus, the power generation efficiency can be increased.

  In addition, according to the method for manufacturing a solar cell of the present modification, a step of forming a separation groove in the intermediate region 15 by laser processing or the like is unnecessary in order to prevent side leakage, so that the solar cell can be more easily performed at low cost. Can be manufactured.

[Second Embodiment]
FIG. 2 is a schematic partial cross-sectional view showing a solar cell according to the second embodiment. In the solar cell according to the present embodiment, the configuration other than the intermediate region 25 is the same as that of the first embodiment, and thus description thereof is omitted. The same configuration as that of the first embodiment will be described using the same reference numerals.
In the present embodiment, the intermediate region 25 is formed to discontinuously disperse between the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8 and to fill the periphery of these small regions 26. Filled region 27. The small region 16 is made of a conductive material having a higher conductivity than the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8. The filling region 27 is formed of an insulator material having a lower conductivity than the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8.

As the conductor material, a material having optical transparency is preferable. For example, a transparent metal oxide such as gallium-doped zinc oxide (GZO) or indium tin oxide (ITO) can be employed. As the insulator material, a material having optical transparency is preferable. For example, a metal oxide such as SiO ₂ , TiO ₂ , or ZnO, or another transparent insulating material such as MgF ₂ can be employed. One of the small regions 26 may be composed of one insulating fine particle, or may be composed of an aggregate of the insulating fine particles. The filling region 27 may be uniformly formed of the insulator material or may be formed as an aggregate of insulator fine particles.

  The sizes of the small region 26 and the filling region 27 are not particularly limited, but the light reflected by these regions and contributing to power generation in the first photoelectric conversion layer 4 and the second photoelectric conversion layer passing through these regions. 8 is selected in consideration of the balance of light that contributes to power generation at 8 and that the current flow is not hindered in the thickness direction of the layer. For example, the thickness of each of the small region 26 and the filling region 27 can be 0.01 μm or more and 2 μm or less, and the coverage of the first photoelectric conversion layer 4 by the small region 26 can be 10% or more and 70% or less. However, in this embodiment, when both the small region 26 and the filling region 27 are made of a light transmissive material, a light scattering effect can be obtained by both of them. It can be made thinner than the small region 16 of one embodiment.

In the solar cell manufacturing method of the present embodiment, the intermediate region 25 is formed as follows.
First, a small region 26 made of a conductor is formed on the first photoelectric conversion layer 4 by performing a sputtering method or a CVD method using a transparent conductive metal oxide material such as GZO or ITO as a target or a vapor deposition material. At this time, the surface of the first photoelectric conversion layer is covered with a mask having a discontinuous opening pattern corresponding to the small region 26, thereby forming the discontinuously dispersed small regions 26 made of a conductor. .

  Next, the first photoelectric conversion layer 4 in which the small regions 26 are formed by using a dispersion obtained by dispersing fine particles of the insulator having a particle diameter of 0.01 μm or more and 2 μm or less in an appropriate dispersion medium by spin coating. Apply on top. By drying and removing the dispersion medium, a filling region 27 made of the insulating fine particles is formed around the small region 26. Thus, the intermediate region 25 of the present embodiment having the small region 26 and the filling region 27 is formed.

  In the solar cell of this embodiment, unlike the conventional intermediate layer made of a transparent transparent conductive film, the discontinuously dispersed small regions 26 made of a conductor and the insulation formed around these small regions 26 Since the intermediate region 25 having the filling region 27 made of a body is formed between the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8, the first photoelectric conversion layer 4 and the second photoelectric conversion layer Although the current flows in the thickness direction of 8, the current hardly flows in the extending direction. Therefore, even if the solar cell is the integrated solar cell and the portion that electrically connects the upper electrode 10 and the lower electrode 2 is formed, for example, on the side portion of the power generation unit, no side leak occurs. Further, the small regions 26 made of a light-transmitting conductor are dispersed in the extending direction of the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8, and the surroundings are filled regions made of a light-transmitting insulator. By filling with 27, the light scattering effect of incident light can be enhanced, and the optical path length increasing effect can be obtained. In particular, in the present embodiment, since the small region 26 and the filling region 27 are formed of different materials, when they are made of a light-transmitting material, the respective light refractive indexes are different. A light scattering effect further enhanced than that of the form can be obtained. Therefore, it is possible to effectively use incident light and increase power generation efficiency. In addition, since it is not necessary to provide a separation groove for preventing side leakage in the intermediate region 25, the area of the connection portion between the first photoelectric conversion layer 4 and the second photoelectric conversion layer 8 that does not contribute to power generation is suppressed. Thus, the power generation efficiency can be increased.

  In addition, according to the method for manufacturing a solar cell of this embodiment, since a step of forming a separation groove in the intermediate region 25 by laser processing or the like is not necessary in order to prevent side leakage, the solar cell can be more easily performed at low cost. Can be manufactured.

As mentioned above, although this invention was demonstrated by 1st Embodiment and 2nd Embodiment, this invention is not limited to these.
The formation method of the small regions 16 and 26 and the filling region 27 is not limited to the method adopted in the above embodiment, and various film forming methods such as a spin coating method, a spray method, a dipping method, a sputtering method, and a CVD method are adopted. be able to. Further, it is not necessary to form the small regions 16 and 26 on the first photoelectric conversion layer 4 from the beginning. For example, a conductive film or an insulating film is uniformly formed on the first photoelectric conversion layer 4 by sputtering or CVD. After forming the film, the other part may be dissolved and removed by using an appropriate etching agent while leaving the part of the conductive film or the insulating film that is difficult to dissolve, such as crystal grains. In this case, the portions of the conductive film or insulating film that remain without being dissolved in the etching agent become the small regions 16 and 26. In this method, not only wet etching using a liquid etching agent but dry etching such as reactive ion etching (RIE) may be employed.

  Moreover, in the said embodiment, although the example which applied this invention to the super straight type solar cell in which light injects from a board | substrate side was demonstrated, this invention is not limited to this, Light injects from the opposite side to a board | substrate. The present invention may also be applied to a substrate type solar cell. Also in this case, an intermediate region can be formed between the two photoelectric conversion layers by the same method as in the above embodiment.

  Moreover, in the said embodiment, although the example which applied this invention to the tandem-type solar cell which has the two photoelectric converting layer which consists of the 1st photoelectric converting layer 4 and the 2nd photoelectric converting layer was demonstrated, this book The invention is not limited to this, and can be applied to a multi-junction solar cell such as a triple solar cell having three photoelectric conversion layers. In this case, an intermediate region may be formed between at least one pair of adjacent two photoelectric conversion layers by the same method as in the above embodiment, or between all the photoelectric conversion layers in the same manner as in the above embodiment. An intermediate region may be formed.

It is a general | schematic fragmentary sectional view which shows the solar cell which concerns on 1st Embodiment. It is a general | schematic fragmentary sectional view which shows the solar cell which concerns on 2nd Embodiment. It is a general | schematic fragmentary sectional view which shows the example of the conventional integrated solar cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent insulating board | substrate 2 Lower electrode 4 1st photoelectric converting layer 8 2nd photoelectric converting layer 10 Upper electrode 11 Transparent electrode 12 Back surface electrodes 15, 25 Middle area | region 16, 26 Small area 27 Filling area | region

Claims (15)

At least two photoelectric conversion layers stacked;
A solar cell having a power generation unit that is interposed between the two photoelectric conversion layers and includes an intermediate region that electrically and optically connects the two photoelectric conversion layers;
The solar cell, wherein the intermediate region includes small regions that are electrically discontinuously dispersed in the extending direction of the two photoelectric conversion layers.   The solar cell according to claim 1, wherein the small region is an insulator having a conductivity lower than that of the two photoelectric conversion layers.   The solar cell according to claim 1, wherein the small region is a conductor having a conductivity higher than that of the two photoelectric conversion layers.   An insulator having a conductivity lower than the conductivity of the two photoelectric conversion layers is disposed around a small region made of a conductor having a conductivity higher than that of the two photoelectric conversion layers. The solar cell of Claim 3 which has the area | region to include. An insulating substrate;
The solar cell according to any one of claims 1 to 4, further comprising the power generation unit formed on the insulating substrate.
The power generation unit is a solar cell having a lower electrode on the insulating substrate side and an upper electrode on the opposite side of the insulating substrate. An insulating substrate;
A solar cell according to any one of claims 1 to 4, comprising a plurality of the power generation units formed on the insulating substrate.
Each of the plurality of power generation units has a lower electrode provided on the insulating substrate side and an upper electrode provided on the opposite side of the insulating substrate,
At least one of the plurality of power generation units is a solar cell in which an upper electrode is electrically connected to a lower electrode of another power generation unit adjacent thereto. At least two photoelectric conversion layers stacked;
A method for producing a solar cell having a power generation unit that is interposed between the two photoelectric conversion layers and includes an intermediate region that electrically and optically connects the two photoelectric conversion layers,
After forming the first photoelectric conversion layer of the two photoelectric conversion layers, an insulator having a conductivity lower than that of the two photoelectric conversion layers is formed on the first photoelectric conversion layer. Forming a small region to be distributed,
Forming a second photoelectric conversion layer of the two photoelectric conversion layers on the surface on which the small region is formed, and
A method for manufacturing a solar cell, wherein the intermediate region is a region in which small regions are formed that are electrically discontinuously dispersed in the extending direction of the two photoelectric conversion layers.   The method for manufacturing a solar cell according to claim 7, wherein the step of forming the small region includes a step of applying a dispersion liquid in which fine particles made of the insulator are dispersed in a dispersion medium.   The step of forming the small region forms a layer made of the insulator on the first photoelectric conversion layer, and then removes a part of the layer made of the insulator with a solvent that dissolves the insulator. The manufacturing method of the solar cell of Claim 7 including a process.   The step of forming the small region includes the step of forming the small region on the first photoelectric conversion layer through a mask having a plurality of discontinuous opening patterns. Production method. At least two photoelectric conversion layers stacked;
A method for producing a solar cell having a power generation unit that is interposed between the two photoelectric conversion layers and includes an intermediate region that electrically and optically connects the two photoelectric conversion layers,
After forming the first photoelectric conversion layer of the two photoelectric conversion layers, a conductor having a conductivity higher than the conductivity of the two photoelectric conversion layers is formed on the first photoelectric conversion layer. Forming a small region to be distributed,
Forming a second photoelectric conversion layer of the two photoelectric conversion layers on the surface on which the small region is formed, and
A method for manufacturing a solar cell, wherein the intermediate region is a region in which small regions are formed that are electrically discontinuously dispersed in the extending direction of the two photoelectric conversion layers.   The method for manufacturing a solar cell according to claim 11, wherein the step of forming the small region includes a step of applying a dispersion liquid in which fine particles made of the conductor are dispersed in a dispersion medium.   The step of forming the small region forms a layer made of the conductor on the first photoelectric conversion layer, and then removes a part of the layer made of the insulator with a solvent that dissolves the insulator. The manufacturing method of the solar cell of Claim 11 including a process.   The step of forming the small region includes the step of forming the small region on the first photoelectric conversion layer through a mask having a plurality of discontinuous opening patterns. Production method.   15. The region according to claim 11, wherein a region including an insulator having a conductivity lower than that of the two photoelectric conversion layers is formed around the small region in the intermediate region. Solar cell.

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