WO2013122067A1

WO2013122067A1 - Photoelectric conversion element

Info

Publication number: WO2013122067A1
Application number: PCT/JP2013/053304
Authority: WO
Inventors: 剛人辻
Original assignee: 富士電機株式会社
Priority date: 2012-02-17
Filing date: 2013-02-13
Publication date: 2013-08-22

Abstract

Provided is a photoelectric conversion element that minimizes Joule heating near a through-hole. One embodiment of the present invention provides a photoelectric conversion element (100) in which a plurality of unit cells (10) are formed on one surface (1a) of an insulating substrate (1). The other surface (1b) thereof is provided with a plurality of backside electrodes (20) that connect the unit cells to each other in series. Each unit cell is provided with an underside electrode (12), a photoelectric conversion layer (14), and a transparent electrode (16). Each such transparent electrode is provided with a conductor (50) that is formed in contact with the surface of said transparent electrode and has linear sections (52) that extend from a first through-hole (30).

Description

Photoelectric conversion element

The present invention relates to a photoelectric conversion element. More specifically, the present invention relates to a photoelectric conversion element utilizing a through hole.

BACKGROUND In recent years, solar cells that generate electric power by sunlight, that is, photoelectric conversion elements have been manufactured. In particular, thin film solar cells, which are flexible and lightweight photoelectric conversion elements with few materials used at the time of manufacture, are attracting attention. A common structure as a thin film solar cell is a so-called monolithic structure in which a plurality of unit cells are connected in series for integration. In this monolithic structure, unit cells are individualized by separating an electrode layer or the like by patterning or scribing about three times, and the unit cells are connected in series. Further, as another structure of the thin film solar cell, a solar cell having through holes connecting both surfaces of a substrate or the like has been proposed (for example, Patent Document 1). Furthermore, a method of forming a series connection of unit cells through a through hole formed in a substrate, which is represented by a SCAF structure (Series Connection through Apertures Formed on Film, FIG. 1), has also been put to practical use.

In the solar cell of a SCAF structure, the back electrode formed in the back which is a field of a substrate opposite to a light-receiving side is used. That is, in a unit cell, one of two electrodes such as a transparent electrode and a back electrode sandwiching the photoelectric conversion layer formed on the light receiving surface is connected to a back electrode serving as a wiring provided on the back. The back electrode extends to the back of the substrate and is connected to the other electrode of another unit cell disposed next to the light receiving surface. In order to establish conduction between the light receiving surface and the back surface, a first through hole (referred to as a current collection hole) and a second through hole (referred to as a connection hole) penetrating the substrate are used. The structure of the photoelectric conversion element of a SCAF structure is shown by the perspective view in FIG.

As a current collection structure other than the above, a structure has also been proposed in which the current generated through the through holes formed in the insulating layer called Metal Wrap Through (MWT) back contact cell is collected by the metal foil on the back surface ( For example, Patent Document 2).

Japanese Patent Laid-Open No. 2002-208718 International Publication No. WO 2007/106756 Pamphlet (Japanese Patent Application Publication No. 2009-529805)

In a conventional photoelectric conversion element of SCAF structure, as shown in FIG. 1, a transparent electrode is disposed on the surface of the light receiving surface on the positive electrode side, and the generated current is collected by this transparent electrode. Specifically, as shown in the entire image in FIG. 1A, the photoelectric conversion element 700 is formed by dividing each photoelectric conversion element as a laminate by scribe lines or separation lines SL1 and SL2. Have. Each unit cell 710 includes a back surface electrode 712, a photoelectric conversion layer 714, and a transparent electrode 716, and is connected in series by the back surface electrode 720. In the inner wall surface of the first through hole 730, the layer of the transparent electrode 716 and the layer of the back electrode 720 on the back surface of the substrate 701 are in contact with each other, and the current from the transparent electrode 716 is transmitted to the back electrode 720.

However, as the transparent conductive material 716, a conductive oxide, that is, an In-based oxide such as ITO (tin-doped indium oxide) or a Zn-based oxide material such as AZO (aluminium-doped zinc oxide) is used. Therefore, the electrical resistance of the transparent conductive material 716 is larger than that of metal, and energy loss which is lost as Joule heat until reaching the first through hole 730 becomes a problem. This energy loss also affects the solar cell characteristics as a reduction of the fill factor. The energy loss is also a problem because the transparent electrode 716 is the current path of the entire series connection of the unit cells 710. Moreover, the path for transferring power from the transparent electrode 716 to the back surface of the substrate 701 through the first through holes 730 (FIG. 1B) is necessarily a current path gradually concentrated toward the first through holes 730. As the current passes through the first through hole 730, the current generated by the photoelectric conversion layer 714 is also added, so the current density near the first through hole 730 increases dramatically. In FIG. 1 (b), the state of the current is schematically displayed by a white arrow. This concentration of current generates Joule heat locally, leading to a local temperature rise. If the substrate 701 in the vicinity of the first through holes 730 and a sealing material (not shown) for sealing the photoelectric conversion element 700 can not withstand the heat, irreversible damage of these members may be caused.

Furthermore, on the inner wall surface of the first through hole 730, a further concentrated current is transmitted by the contact between the layer of the transparent conductive film 716 and the layer of the back electrode 720, so concentration of current and accompanying heat generation become more remarkable. . That is, if the contact portion between the layer of the transparent conductive film 716 and the layer of the back electrode 720 on the inner wall surface of the first through hole 730 can not be formed with high reliability, the electrical characteristics may also be defective after production or installation. It may be connected.

One countermeasure against these problems is to increase the number of first through holes 730 formed. Accordingly, it is not impossible to distribute the current to the plurality of first through holes 730. However, increasing the first through holes 730 may cause new problems. When the first through holes 730 are increased, for example, the area of the power generation area decreases, which adversely affects the power generation function. In addition, when the number of the first through holes 730 is increased, the probability that the mechanical strength of the substrate 701 decreases or the leak due to an unexpected current path due to the first through holes 730 itself increases.

The similar situation, in particular, the problem due to the problem on the inner wall surface of the through hole and the improvement due to the number of formation thereof also hold for the second through hole 740. As shown in FIG. 1C, in the second through hole 740, the current from the back electrode 720 is transmitted to the back electrode 712 located on the light receiving surface of the substrate 701. The white arrow in FIG. 1C also schematically shows the path of the current. Since the back electrode 720 and the back electrode 712 are usually made of metal, the generation of Joule heat is not as serious as the first through holes 730. However, a similar problem arises from the fact that this current also flows intensively on the inner wall surface of the second through hole 740, and the problem is alleviated by the number of formation. And the same is true for the new problems caused by increasing the number of formations.

Moreover, the higher the type of photoelectric conversion element, the higher the current density at which power is generally generated. For example, in the case of an amorphous silicon solar cell, the amount of current per unit area of the power generation area, that is, the current density J _op is approximately 10 mA / cm ² during the power generation operation. Furthermore, as a photoelectric conversion element of a type in which current density is increased, compound solar cells including CIGS [Cu (In, Ga) Se2] called chalcopyrite-based are also known. The current density J _{op in} that case reaches about 25 mA / cm ² or so. With such a type in which the current is about three times as large, the above-mentioned problem of the current concentration in the through hole may be more serious.

The present invention has been made to solve at least one of the above-mentioned problems. The present invention contributes to the realization of a photoelectric conversion element in which the Joule heat in the vicinity of a through hole such as a current collection hole is suppressed by reducing the electric resistance in the vicinity of the current collection hole that collects generated current from a transparent conductive film. .

As a result of examining the above problems, the inventor of the present application solves at least some of the above problems by adopting a specific configuration for reducing the electrical resistance in the vicinity of the current collection holes (first through holes). I found that.

That is, in one aspect of the present invention, it is a photoelectric conversion element in which a plurality of unit cells connected in series with each other are formed on one surface of a piece of insulating substrate, and each unit cell is A back surface electrode formed on the one surface of the substrate, a photoelectric conversion layer formed on the surface of the back surface electrode, and a transparent electrode formed on the surface of the photoelectric conversion layer Through the first through hole formed on the other surface of the substrate and electrically connected to the transparent electrode of one unit cell through the first through hole penetrating through the substrate, and through the second through hole penetrating through the substrate The unit cell further includes a plurality of back electrodes separated from one another electrically connected to the back electrode of another unit cell, wherein the plurality of unit cells are separated by the transparent electrode and the back electrode belonging to each unit cell. For the back electrode, the first The unit cell is electrically connected through the through hole and the second through hole, whereby each unit cell is connected in series by the back electrode, the transparent electrode is formed in contact with the surface of the transparent electrode, and the first There is provided a photoelectric conversion element comprising a metal conductor having a linear portion extending from a through hole.

Here, the photoelectric conversion layer is an arbitrary layer that generates electric power by light, and typically, a thin film of silicon or silicon germanium such as amorphous or microcrystalline (hereinafter referred to as “silicon-based thin film”) or a compound such as CIGS It contains a system thin film.

In any aspect of the present invention, it is possible to produce a photoelectric conversion element that reduces Joule heat (resistance loss) generated due to the electrical resistance of the transparent conductive film.

It is a perspective view which shows the structure of the photoelectric conversion element of the conventional SCAF structure. It is a partially broken perspective view which shows schematic structure of the photoelectric conversion element of the improved SCAF structure in one embodiment of this invention. It is a top view which shows the structure of the photoelectric conversion element of the improved SCAF structure in one embodiment of this invention. FIG. 3A is a plan view of one surface (light receiving surface) side, and FIG. 3B is a plan view of the other surface (rear surface) side. It is a top view which shows the structure of the transparent electrode in the photoelectric conversion element of a SCAF structure. FIG. 4 (a) shows a unit cell in a conventional photoelectric conversion device of the SCAF structure, and FIGS. 4 (b) and 4 (c) show unit cells in the photoelectric conversion device of the improved SCAF structure according to an embodiment of the present invention. Indicates It is a top view showing alignment of a unit cell of a photoelectric conversion element of the improved SCAF structure in one embodiment of the present invention. 5 is a flow chart illustrating a process of manufacturing an improved SCAF structured photoelectric conversion device according to an embodiment of the present invention. It is an enlarged view which shows the structure of the 1st through-hole vicinity of the photoelectric conversion element of the improved SCAF structure in one embodiment of this invention. Fig.7 (a) is a top view of 1st through-hole vicinity, FIG.7 (b) is a schematic sectional drawing which shows the structure of 1st through-hole vicinity. It is a schematic sectional drawing which shows the structure inside the 1st through-hole of a photoelectric conversion element. FIGS. 8 (a) and 8 (b) show the overlap of the membrane inside the first through hole of the conventional SCAF structure and the improved SCAF structure of an embodiment of the present invention, respectively. It is a schematic sectional drawing which shows the structure inside the 2nd through-hole of a photoelectric conversion element. FIGS. 9 (a) and 9 (b) show the overlap of the membranes on the inner wall surface 42 of the second through hole of the conventional SCAF structure and the improved SCAF structure of the embodiment of the present invention, respectively.

Hereinafter, an embodiment of a photoelectric conversion element according to the present invention will be described based on the drawings. In the description, unless otherwise stated, common parts or elements throughout the drawings are denoted by common reference numerals. Further, in the drawings, each of the elements of the respective embodiments is not necessarily shown with the scale ratio of each other.

First Embodiment
[1 Outline structure]
[1-1 Schematic Configuration of Photoelectric Conversion Element]
FIG. 2 is a partially broken perspective view showing a schematic structure of an example of the improved SCAF structure photoelectric conversion element 100 in the present embodiment. FIG. 3 is a plan view showing the configuration of the photoelectric conversion element 100. As shown in FIG. In the photoelectric conversion element 100 provided in the present embodiment, as shown in FIG. 2 and FIG. 3, a plurality of unit cells 10 connected in series are formed on one surface 1 a of a piece of insulating substrate 1. It is done. For example, a substrate of a plastic film can be employed as the substrate 1. Each unit cell 10 is formed on the back surface electrode 12 formed on one surface 1 a of the substrate 1, the photoelectric conversion layer 14 formed on the surface of the back surface electrode 12, and the surface of the photoelectric conversion layer And the transparent electrode 16. That is, in the operation of each unit cell 10, the power generated by the photoelectric conversion layer 14 by the light transmitted through the transparent electrode 16 is taken out by the back electrode 12 and the transparent electrode 16.

A plurality of back electrodes 20 are formed on the other surface 1 b of the substrate 1. The back electrodes 20 are separated from each other so as to be unit areas corresponding to the unit cells 10. The back electrode 20 included in the photoelectric conversion element 100 is electrically connected to the transparent electrode 16 of one unit cell (for example, unit cell 10 _i ) through a first through hole 30 penetrating the substrate 1. The back electrode 20 is also electrically connected to the back electrode 12 of another unit cell (for example, unit cell 10 _{i + 1} ) through a second through hole 40 penetrating the substrate 1. For this reason, in the photoelectric conversion element 100 provided in the present embodiment, in the plurality of unit cells 10, the transparent electrodes 16 and the back surface electrodes 12 belonging to each unit cell _10i are respectively different from the back electrodes 20 different from each other. It is electrically connected through the first through hole and the second through hole. Thus, in the photoelectric conversion element 100, the unit cells 10 are connected in series by the back electrodes 20. In addition, in the unit cell 10 and the back surface electrode 20 which are located in the both ends of the said serial connection, since it is the structure which takes out electric power out of the photoelectric conversion element 100, it is not necessarily produced in this way. For example, there is a configuration in which the connection with the back electrode 20 is established to only one of the transparent electrode 16 or the back electrode 12 of the terminal unit cell 10 or a configuration in which the back electrode 20 is connected to only one unit cell 10 Will be adopted. In addition, in the photoelectric conversion element 100 of the SCAF structure shown in FIG. 2, the 1st through-hole 30 penetrates not only the board | substrate 1 but the back surface electrode 12, the photoelectric converting layer 14, and the transparent electrode 16. On the other hand, the second through hole 40 penetrates the back electrode 12 in addition to the substrate 1.

In the photoelectric conversion element 100 provided in the present embodiment, the conductor 50 in contact with the surface of the transparent electrode 16 is further formed. And the conductor 50 is provided with the linear part 52 extended from the 1st through-hole 30 (FIG. 2 and FIG. 3).

[1-1-1 Effect of Conductor 50]
The photoelectric conversion element 100 having the above structure has several technical advantages in the operation or fabrication of the photoelectric conversion element. First, by forming the conductor 50 on the transparent electrode 16, it is possible to reduce the number of first through holes 30 and the number (area density) per area. That is, the number and the surface density of the conventional first through holes 730 (FIG. 1) have high resistivity indicated by the transparent electrode 716 and the current path from the transparent electrode 716 to the back electrode 720 in the conventional first through holes 730. In order to correspond to both of the high resistivity shown by the above, it has been determined under the premise that the current flowing through the transparent electrode 716 is charged to the back electrode 720. In other words, the current path of the transparent electrode 716 is as short as possible to transmit the current to the back electrode 720, and the current is distributed to as many first through holes 730 as possible, and the current per one first through hole 730 is distributed. It was designed to reduce the amount. On the other hand, in the photoelectric conversion element 100 of the present embodiment, as a different approach from the conventional design concept, the conductive resistance function of the conductor 50, particularly the linear portion 52, reduces the effective resistance value of the transparent electrode 16. . As a result, the reduction of the power generation area by the first through hole 30 is prevented, and the operational advantage of preventing the reduction of the energy loss, ie, the curvilinear factor is also provided

Moreover, in the photoelectric conversion element 100 of the said structure, by making the conductor 50 contact and form the transparent electrode 16, the advantage that a hot spot phenomenon becomes difficult to generate arises also. As described with reference to FIG. 1, in the hot spot phenomenon in the case of the SCAF structure in which unit cells are connected in series, the resistance of the transparent electrode 716 in the current path concentrated in the first through hole 730 becomes a problem. In the photoelectric conversion element 100 of the present embodiment, the linear portion 52 of the conductor 50 is formed to extend from the first through hole 30. Therefore, the current flows through the linear portion 52 rather than the transparent electrode 16 and reaches the first through hole 30. Therefore, a local temperature rise in the vicinity of the first through hole 30 can be suppressed, and the hot spot phenomenon is avoided.

Here, that the linear portion 52 extends from the first through hole 30 typically means that the linear portion 52 starts from the first through hole 30, forms a continuous body, and follows the path thereof It is connected seamlessly and reaches the other part of the transparent electrode 16. However, in addition to this, even if the linear portion 52 extends while being in contact with the edge portion 54 when the edge portion 54 (FIG. 7) that forms the edge of the first through hole 30 is formed, The protuberance 52 extends from the first through hole 30. Further, the linear portion 52 includes an element portion that forms a linear path by a portion or combination that forms a generally linear path. Here, it should be noted that the linear portion 52 plays a role even if, for example, minute fractures are formed. For example, a flexible substrate may be adopted as the substrate 1 to cause bending with a small radius of curvature, or cracks may occur for some reason such as thermal expansion. In some cases, the material of the conductor 50 is intentionally patterned to form a chain-like path in anticipation of the occurrence of the cracks. Even in the case of the conductor structure as in these examples, typical examples of the linear portion 52 include those having a generally linear shape. As long as the linear portion 52 is formed in contact with the transparent electrode 16 having a certain degree of conductivity, the role of lowering the resistance value of the transparent electrode 16 is realized even if there is a fractured portion. .

Furthermore, in the photoelectric conversion element 100 of the present embodiment in which the conductor 50 is formed, the number of first through holes 30 can be reduced without degrading the characteristics of the photoelectric conversion element, so the processing time of the first through holes 30 can be reduced. Can be shortened. When the through holes are formed by mechanical punching, the processing time can be shortened by reducing the number of times of punching. Furthermore, the miniaturization of the mold used is possible. This also makes it possible to reduce the device cost. Further, even in the case of processing using a laser, it is possible to shorten the possible time by reducing the number of irradiations and to reduce the cost of the apparatus accordingly.

[1-1-2 electrode non-forming area (ENEA)]
In the photoelectric conversion element 700 (FIG. 1) of the conventional SCAF structure, the back electrode 720 is formed over a wide area in accordance with the current collection holes (first through holes) being distributed over the wide area of the light receiving surface. There is a need to. In order to form the back electrode 720, it is necessary to reduce the area as much as possible, since it is necessary to form an electrode film for that purpose and to process it for patterning. Therefore, as a preferable configuration in the present embodiment, in the photoelectric conversion element 100, as shown in FIGS. 2 and 3, an electrode non-formed area 60 ((abbreviated as “Electrode Non-Existent Area 60, hereinafter“ ENEA 60 ”) The ENEA 60 in this embodiment is a region where the back electrode 20 is not formed on the other surface 1b of the substrate 1. Fig. 3 (a) is the one surface 1a (light receiving surface) side, Fig. 3 (b). 3B is a plan view of the other surface 1b (rear surface) side, and in FIG. 3B, the ENEA 60 is drawn as a surface to which the other surface 1b of the substrate 1 is exposed. As shown in the positional relationship between a) and (b) in comparison, the ENEA 60 has the other corresponding to the area (for example, the power generation area 18) of one surface 1a on which a plurality of unit cells 10 are formed. It is formed so as to occupy at least a part of the region on the side of the surface 1b, and as shown in FIG. On the side, it extends to at least a part of the area corresponding to ENEA 60. Such a configuration of the photoelectric conversion element 100 makes it possible to reduce the number or the surface density of the first through holes 30 by the conductor 50. In the photoelectric conversion element 100 capable of reducing the number of the first through holes 30, it is possible to provide the ENEA 60 by limiting the area of the back electrode 20.

In the photoelectric conversion element 100 which forms ENEA60, a technical merit arises compared with the structure which does not form ENEA60. The first advantage is that the provision of the ENEA 60 limits the range in which the back electrode 20 is formed, and reduces the resources required to produce the photoelectric conversion element 100. More specifically, when the layer of the back electrode 20 is formed by sputtering, for example, the amount of use can be reduced by miniaturizing the target. In addition, since the electrode size of the sputtering apparatus can be miniaturized, the miniaturization of the apparatus and the reduction of energy at the time of film formation can also be achieved.

Furthermore, the second advantage is that the time for processing can be reduced. Providing the ENEA 60 to limit the range of the back electrode 20 shortens the patterning distance of the laser scribing process for forming, for example, the separation line SL2 (FIG. 3B) for dividing the back electrode 20. The processing time of the scribing process can be shortened.

In addition, as a third advantage, the risk of short circuit between adjacent back electrodes 20 is also reduced. This is because shortening the patterning distance reduces the probability of causing a leak. Furthermore, it is also possible to reduce the risk of damage to the back electrode during back surface processing that may occur due to variations in patterning conditions.

[1-2 Structure of transparent electrode]
Next, a more detailed structure of the above-described photoelectric conversion element 100 will be described. First, the structures of the transparent electrode 16 and the conductor 50 will be described. FIG. 4 is a plan view showing the structure of the transparent electrode in the improved SCAF photoelectric conversion element of this embodiment. FIG. 4A shows a unit cell 710 in the photoelectric conversion element 700 of the conventional SCAF structure, and FIGS. 4B and 4C show a unit cell 10 in the photoelectric conversion element 100 of the present embodiment. Moreover, FIG. 5 is a top view which shows the sequence of the unit cell 10 of the photoelectric conversion element 100 of the improved SCAF structure in the photoelectric conversion element 100 of this embodiment. It is explanatory drawing which expands and shows the structure of the transparent electrode in a photoelectric conversion element.

In the photoelectric conversion element 100, the plurality of unit cells 10 are divided into strips extending in one direction, and the unit cells are arranged in the width direction of the strips. In FIG. 4 and FIG. 5, each unit cell is drawn by a strip extending in the vertical direction of the paper surface. The plurality of back electrodes 20 are divided into the back electrodes 20 on the other surface 1 b of the substrate 1 so as to be aligned in the direction in which the

unit cells

10 _i and 10 _{i + 1} are arranged in the plurality of unit cells 10. (Figure 3). In the unit cell 710 (FIG. 4A) of the conventional photoelectric conversion element 700, the current collected by the transparent electrode 716 having a large electric resistance flows, and another unit cell 710 included in the photoelectric conversion element 700. The current from the source also has to pass through the transparent electrode 716. Therefore, a large number of first through holes 730 are formed. On the other hand, in the photoelectric conversion element 100 (FIGS. 4B and 4C) of the present embodiment, at least a part of the linear portion 52 of the conductor 50 is in the longitudinal direction of the strip of the transparent electrode 16, that is, photoelectric conversion It extends in the vertical direction on the sheet of FIG. 4 of the element 100. For this reason, even if the number of first through holes 30 is reduced, a current path passing not only through the transparent electrode 16 but also through the conductor 50 is established. That is, the electrical resistance of the transparent electrode 16 does not substantially increase. Furthermore, as shown in FIG. 4C, for example, an ENEA 60 is formed on the other surface 1b of the substrate 1 and from the first through hole 30 to reach a region corresponding to the ENEA 60 on the side of one surface 1a. It can also be configured to extend. For that purpose, for example, as clearly shown in FIG. 4C, a device such as increasing the number of linear portions 52 is effective. Besides this, adjustment such as lowering the electric resistance of the conductor 50 by adjusting the material and film thickness of the conductor 50 is also effective.

Note that, as shown in FIG. 3, a typical ENEA 60 in the photoelectric conversion element 100 has a direction in which a plurality of unit cells 10 are arranged, that is, a strip-like width direction (upper and lower in FIG. Direction). In the photoelectric conversion element 100 having such a configuration, the ENEA 60 extends in the direction in which the strip-shaped

unit cells

10 _i and 10 _{i + 1} are arranged. For this reason, it becomes possible to make ENEA 60 into the shape with high practicability, such as a strip | belt-shaped area | region. This can be said to be an effect resulting from the arrangement in which the linear portion 52 is oriented to extend in the longitudinal direction of the strip shape as shown in FIG. 4 (c).

In particular, in the photoelectric conversion element 100, through one unit cell 10 _i transparent electrode 16 and the back electrode 12 belongs to is in the vicinity of both end portions 10E1 and 10E2 of the strip, the first through hole 30 and the second through hole 40, They are electrically connected to the back electrodes 20 different from one another. Further, the ENEA 60 is a region of the other surface 1 b corresponding to a region extending in the width direction of the strip across the plurality of unit cells 10 in the longitudinal direction central portion of the strip of each of the plurality of unit cells 10.

In the photoelectric conversion element 100, in addition to forming the ENEA 60 in a shape having high practicability described above, the connection by the first through holes 30 and the second through holes 40 is realized at each of the both ends 10E1 and 10E2 of the strip. Is also possible. Then, the electrical resistance connecting the unit cells 10 can be kept small while the advantage of providing the ENEA 60, that is, the shape of the back electrode 20 is reduced.

In particular, as shown in FIG. 5, in the photoelectric conversion element 100 of the present embodiment, each unit cell 10 _i is provided with a plurality of first through holes 30, and one linear portion 52 of the conductor 50 is one unit cell. At least two of the first through holes 30 in the range of 10 _i are formed to be connected. In this configuration, the collected current and the currents from other unit cells are distributed among the plurality of first through holes 30 connected by the linear portions 52 in accordance with the resistance value of each path. In addition, even if any failure occurs in any of the first through holes 30, the other first through holes 30 connected by the route of the linear portion 52 become redundant paths, so the failure is directly related to the power generation performance. Adverse effects are less likely to occur. Furthermore, even when the electromotive force of the power generation operation is distributed in one unit cell 10, the generated current is distributed among the plurality of first through holes 30 connected by the linear portion 52. For this reason, it is possible to prevent in advance the situation in which the current is concentrated in the individual first through holes 30 due to the distribution of the electromotive force to cause the hot spot phenomenon.

Furthermore, the linear portion 52 of the conductor 50 in the photoelectric conversion element 100 has a plurality of linear portions extending from the first through hole 30 in a plurality of directions on one surface 1 a. With this configuration, the resistance value of the path of the current flowing from each part of the transparent electrode 16 having a planar spread toward the first through hole 30 is reduced.

[1-3 Material of Conductor 50]
The conductor 50 is most typically one component as a main component, such as a layer formed by patterning a silver paste by screen printing and then curing the silver paste and forming it as a metal. . That is, the conductor 50 may contain components other than metals, such as a binder component. In addition to the above, a layer of a conductor mainly composed of any kind of metal that can be patterned can be adopted as the conductor 50. For example, the same effect can be achieved by adopting deposition of a thin metal layer with a suitable mask, adhesion with a conductive adhesive of a patterned metal foil, or the like. Moreover, it is also possible to employ a conductive material such as carbon paste for the conductor 50. However, in the case of utilizing the effect of conduction of the conductor 50 on the inner wall surface 32 of the first through hole 30 described later, a forming method or a material in which the conductor 50 can be formed on the inner wall surface 32 is employed.

[1-4 Manufacturing method]
Next, a method of manufacturing the photoelectric conversion element 100 having the structure shown in FIGS. 2 to 5 will be described with reference to FIG. The materials, amounts used, proportions, treatment contents, treatment procedures, orientations of elements or members, specific arrangements and the like shown in the following description of the production method can be appropriately changed without departing from the spirit of the present invention. Accordingly, the scope of the present invention is not limited to the following specific examples. FIG. 6 is a flowchart showing steps of manufacturing the improved SCAF photoelectric conversion element in the present embodiment. In addition, FIG. 7, FIG. 8 (b), and FIG.9 (b) which the cross-section of the photoelectric conversion element 100 clearly shows are also referred to suitably. First, as a substrate 1 for producing the photoelectric conversion element 100, an insulating film substrate is adopted. Specifically, for example, a polyimide film having a thickness of about 50 μm is used. Other examples of the material of the substrate that can be adopted include other insulating plastic films such as PET, PEN, PES, acryl, aramid and the like.

First, an opening 44 (FIG. 9B) for the second through hole 40 (connection hole) is formed in the substrate 1. For this purpose, an opening 44 is provided at a predetermined position of the substrate 1 by a punching die (punch) (connection hole forming step S102). Next, by heating under reduced pressure, degassing processing S104 is performed to remove the gas released from the polyimide film of the material of the substrate 1. The degassing process S104 may be performed either before or after the connection hole forming process S102. For example, it is also preferable to add a degassing process (not shown) before the connection hole forming step S102 in the flow of FIG.

Thereafter, a layer to be the back surface electrode 12 is formed on one surface 1a of the substrate 1 (back surface electrode layer forming step S106), and then the other surface 1b of the surface of the substrate 1 and the layer on the substrate 1 side of the back surface electrode 20 The first connection wiring layer 22 is formed (first connection wiring layer forming step S108). The layer to be the back electrode 12 is formed by sputtering, for example, silver (Ag) to a film thickness of 200 nm. Also, as a material of the first connection wiring layer 22, for example, the same Ag as the layer to be the back electrode 12 is adopted. In addition to these materials, metals such as an Ag alloy, aluminum (Al), and an alloy thereof can be used as the material of the layer serving as the back surface electrode 12 and the first connection wiring layer 22. Moreover, the film etc. which consist of a multilayer structure of a metal layer and a transparent electrode layer can also be used for the layer used as the back surface electrode 12. The film formation method for forming the layer to be the back electrode 12 and the first connection wiring layer 22 is not limited to the sputtering method, and vacuum deposition, spray film formation, printing, coating, and plating may be employed. You can also.

Here, in the first connection wiring layer forming step S108, in order to form the ENEA 60, the formation range of the first connection wiring layer 22 is limited to a region other than the ENEA 60. In order to provide the ENEA 60 and limit the area of the back electrode 12, it is a typical method in sputtering to form the ENEA 60 depending on the shape of the target and the electrode shape of the sputtering apparatus. Even when other film forming methods are adopted, it is easy to provide ENEA 60 having a simple shape like, for example, a strip. In addition, if the amount of released gas from the substrate 1 becomes a problem in the subsequent film forming process as a result of providing the ENEA 60, the timing and processing conditions of the degassing process such as the degassing process S104 should be changed. Is possible.

When the back surface electrode layer forming step S106 and the first connection wiring layer forming step S108 are completed, the layer to be the back surface electrode 12 formed on one surface 1a of the substrate 1 and the other surface 1b formed on the other surface 1b of the substrate 1 The layers of the first connection wiring layer 22 overlap directly on or near the inner wall surface of the second through hole 40 (connection hole), and are electrically connected to each other (FIG. 9B).

When the first connection wiring layer forming step S108 is completed, the first surface patterning step S110 is performed, and at that time, the first connection wiring layer 22 formed on one surface 1a (first surface) of the substrate 1 is separated. It separates with SL1. Thereafter, an opening 34 (FIG. 8 (b)) for the first through hole 30 (current collecting hole) is formed in the substrate 1 using a punching die different from the case of the second through hole 40 (current collecting hole Formation step S112). At this time, not only the substrate 1 but also the layer to be the back electrode 12 and the first connection wiring layer 22 which are formed on the substrate 1 at that stage are formed. Furthermore, a photoelectric conversion layer 14 such as a semiconductor layer is formed on one surface 1a side of the substrate 1 (semiconductor layer forming step S114). In this photoelectric conversion layer 14, for example, an n layer, an i layer and a silicon (Si) layer of an nip structure in which an n layer, an i layer and ap layer of amorphous silicon are arranged from the substrate 1 side are formed. A coupled plasma CVD (Chemical Vapor Deposition) method is used. In addition, the film-forming method at the time of forming the photoelectric converting layer 14 in this embodiment is not specifically limited. As described above, using a high-frequency capacitively coupled plasma CVD method, and using a device having a parallel plate type shower head electrode as a discharge electrode as a film forming device therefor is a preferable example of the film forming method. Another configuration of the photoelectric conversion layer 14 may be a photoelectric conversion layer in which microcrystalline Si is used for the i layer, or a multijunction in which an nip structure of amorphous Si and an nip structure of microcrystalline Si are stacked. It may be a type (tandem type) photoelectric conversion layer. As another example of the constituent material of the n layer and the p layer, it is also possible to modify the present embodiment so as to use an alloy such as amorphous SiO. Moreover, it is also possible to add SiO, amorphous Si, or a microcrystalline Si layer as an interface layer or a tunnel junction layer in order to make various technical improvements.

Moreover, in the case of formation of the photoelectric converting layer 14 in the photoelectric conversion element 100 of this embodiment, the other device for improving the processing efficiency of a film-forming process is also useful. For example, a roll-to-roll system in which a film is continuously formed while continuously transporting the substrate 1 can be adopted as a preferable process for the present embodiment. Besides this, a method (stepping roll method) is also implemented, which operates so as to repeat the transport mode and the film formation mode, and causes the substrate to be in a stopped state in the film formation mode. It can be adopted as a preferred process of form.

After forming the photoelectric conversion layer 14 in the semiconductor layer forming step S114, a transparent conductive material is further deposited on the side of one surface 1a of the substrate 1 as a layer to be the transparent electrode 16 (transparent conductive layer forming step S116) . At this time, the transparent conductive material is not deposited in the range by providing a mask in the range in which the second through holes 40 are provided among both end portions of the photoelectric conversion layer, that is, both ends 10E1 and 10E2. Make it As a result, in this range, the photoelectric conversion layer 14 is exposed (FIG. 2, FIG. 3 (a), FIG. 9 (b)). Thus, the transparent electrode 16 is not formed in the region of the second through hole 40.

Various kinds of transparent conductive materials can be used as the transparent conductive material for the layer to be the transparent electrode 16 of the present embodiment, and the material is not particularly limited. This transparent conductive material is typically any one or a combination of transparent conductive materials of metal oxides such as ITO, SnO ₂ , TiO ₂ , ZnO, IZO (In ₂ O ₃ -ZnO, registered trademark), etc. (Laminate or mixture) is selected. Furthermore, RF sputtering, DC sputtering, a printing method, a coating method, etc. are employable as a film-forming method of transparent conductive layer formation process S116.

Next, a layer of the second connection wiring layer 24 which forms the back electrode 20 together with the first connection wiring layer 22 is formed on the entire surface of the other surface 1 b of the substrate 1 (second connection wiring layer forming step S118). As the layer of the second connection wiring layer 24, a low resistance conductive layer such as a metal material such as nickel is formed. After the second connection wiring layer forming step S118, the layer to be the transparent electrode 16 formed on one surface 1a of the substrate 1 and the layer of the second connection wiring layer 24 formed on the other surface 1b of the substrate 1 (1) They are directly superposed on or near the inner wall surface of the through hole 30 and electrically connected to each other (FIG. 8 (b)). Since the second connection wiring layer 24 is formed to be in contact with the first connection wiring layer 22 on the other surface 1b of the substrate 1, these connection wiring layers on the other surface 1b are connected to each other and electrically Are layers for the back electrode 20 as an integrated connection wiring layer.

Conductor 50 is formed on the surface of the layer to be transparent electrode 16 on one surface 1a side of substrate 1 after the second connection wiring layer formation step S118 so that a predetermined pattern is formed (conductivity Body layer forming step S120). As a material of the conductor 50, a metal material such as silver (Ag) can be adopted. Besides this, it is also possible to use a film having a multilayer structure using a metal material such as Ag alloy, Al, Cu, Ti or the like. Furthermore, a conductive film containing fine powder or fine particles of these metals, for example, a conductive film formed of silver paste can also be adopted. Here, the factors considered in selecting the material of the conductor 50 are that patterning is easy and that the conductivity is high, deterioration occurs during the expected period of use of the product (module) of the solar cell. There is no such thing. By the patterning, the linear portion 52 and the border portion 54 (FIG. 7) are also formed as a part of the conductor 50. Furthermore, materials with low conductivity such as carbon paste are also applicable.

It supplements regarding the patterning method used in conductor layer formation process S120. Various methods can be adopted for the patterning used in the present embodiment. The screen printing method described above is a preferred example thereof. Other than this, an inkjet printing method, a patterning process by vapor deposition using a metal mask, a dispenser drawing, a film transfer and the like can also be adopted.

After the conductor layer forming step S120, patterning by the separation line SL1 is performed again on one surface 1a (first surface) side of the substrate 1 of the substrate 1 (first surface patterning step S122). As a result of this patterning, the photoelectric conversion layer 14 has the same shape as the back electrode 12. The transparent electrode 16 is not formed in the vicinity of the second through hole 40, but the vicinity of the separation line SL1 is divided at the same position as the back surface electrode. Thus, the unit cell 10 is formed by stacking the back electrode 12, the photoelectric conversion layer 14 (semiconductor layer), and the transparent electrode 16 in this order except for the vicinity of the connection hole 2 at the end in the shape surrounded by the separation line SL1. Be done.

In addition to the first surface patterning step S122 shown here, it is also preferable to perform a preliminary patterning process (for example, the first surface patterning step S110) in order to perform the step of forming the unit cells 10 more reliably. The preliminary patterning process is performed, for example, at any stage after the back surface electrode layer forming process S106 and before the semiconductor layer forming process S114. Also in this preliminary patterning process, it is the position of the separation line SL1 that is patterned so as to separate the back electrode layer 6.

Finally, laser processing is performed on the side of the other surface 1b (second surface) of the substrate 1 of the substrate 1 at the position of the separation line SL2 (second surface patterning step S124). In the second surface patterning step S124, the second connection wiring layer 24 and the first connection wiring layer 22 are simultaneously separated. In addition to the scribing process (laser scribing) which typically uses a laser, depending on the material of the back surface electrode 12 and the photoelectric converting layer 14, the mechanical scribing method by the metal blade can also be employ | adopted for these patterning.

In the above description, although the conductive layer forming step S120 is performed in the order prior to the first surface patterning step S122 and the second surface patterning step S124, the conductive layer forming step S120 is patterned on the first surface It is also possible to carry out between the step S122 and the second surface patterning step S124 or to carry out the conductor layer forming step S120 after completing the first surface patterning step S122 and the second surface patterning step S124.

[1-5 configuration of through holes: outline by conductor 50]
Next, the structure of the conductor 50 in the vicinity of the first through hole 30 in the photoelectric conversion element 100 of the present embodiment will be described in detail. FIG. 7 is an enlarged view showing a structure in the vicinity of the first through hole 30 in the photoelectric conversion element 100 of the improved SCAF structure in the present embodiment. FIG. 7 (a) is a plan view seen from one surface 1a side in the vicinity of the first through hole 30, and FIG. 7 (b) shows a structure in the vicinity of the first through hole 30 at a position of AA '. It is the schematic sectional drawing cut | disconnected.

In the photoelectric conversion element 100, the conductor 50 covers a position of the surface of the transparent electrode 16 at which the opening 34 of the first through hole 30 is bordered. That is, as shown in FIG. 7, in the unit cell 10, the edge of the first through hole 30 of the first through hole 30 penetrating the substrate 1, the back electrode 12, the photoelectric conversion layer 14, and the transparent electrode 16 is an edge. A border 54 is formed to be taken. Such a configuration of the rim portion 54 is particularly effective in suppressing the generation of Joule heat due to the high current density caused by the current concentration on the transparent electrode 16 in the vicinity of the first through hole 30. Therefore, it becomes possible to suppress a local temperature rise in the vicinity of the first through hole 30, and is useful in the configuration of the photoelectric conversion element 100 of the present embodiment.

[1-6 Connection on inner wall surface of through hole]
In the photoelectric conversion element 100 of the present embodiment, the conduction function of the conductor 50 can also be utilized inside the through hole. FIG. 8 is a schematic cross-sectional view showing the structure inside the first through hole of the photoelectric conversion element. FIGS. 8 (a) and 8 (b) show the overlap of the membranes on the inner wall of the first through hole, respectively, of the conventional SCAF structure and of the improved SCAF structure according to an embodiment of the invention It is. Moreover, FIG. 9 is a schematic sectional drawing which shows the structure inside the 2nd through-hole of a photoelectric conversion element. FIGS. 9 (a) and 9 (b) show the overlap of the membranes on the inner wall of the second through hole, respectively with the conventional SCAF structure and the improved SCAF structure of the embodiment of the present invention is there.

In the first through hole 730 (FIG. 8A) of the conventional SCAF structure, typically, the layer of the back electrode 720 and the layer of the transparent electrode 716 extend on the inner wall surface 732 of the first through hole 730 Electrical continuity is established in the region (indicated by the symbol “716/724”) where they contact each other on the inner wall surface 732. The current path is shown by the outline arrow on the inner wall surface on the right side of the paper surface of FIG. 8A. However, region 716/724 does not always always have a sufficient current path on inner wall surface 732 due to factors such as manufacturing variations. Even if it is assumed that the electric resistance value of the transparent electrode 716 is sufficiently low, as shown in FIG. 4 (a), from the state where a large number of first through holes 730 are disposed, FIG. 4 (b) or (c) As long as the number (area density) per unit area of the first through holes 30 is reduced by reducing the number of the first through holes 30 as in the photoelectric conversion element 100 of the present embodiment shown in FIG. It is necessary to improve the reliability of the first through hole 30 as the conduction path. In particular, even if the probability of breakage due to the hot spot phenomenon is reduced by forming the linear portion 52 of the conductor 50 in contact with the transparent electrode 16, the situation in which the current is still concentrated in the first through hole 30 Is maintained. One direct improvement in such a case is to widen the inner diameter of the first through hole 30 and increase the peripheral length of the first through hole 30 to enlarge the conductive region. However, the improvement will reduce the power generation area.

Therefore, in the photoelectric conversion element 100 of the improved SCAF structure in the present embodiment shown in FIG. 9, a device is employed to improve the reliability of conduction of each first through hole 30 using the conductor 50 (FIG. 8). (B). Specifically, the conductor 50 is disposed on at least a part of the inner wall surface 32 of the first through hole 30 in which each of the back electrode 20 and the transparent electrode 16 extends. The conductor 50 is in contact with both the back electrode 20 and the transparent electrode 16 on the inner wall surface 32 and functions to establish or enhance an electrical path. Adopting such a configuration makes it possible to improve the reliability of conduction in the first through holes 30. The conductor 50 on the inner wall surface 32 may be disposed so as to close the opening 34 of the first through hole 30. Further, regardless of whether or not the opening 34 is closed, there is no manufacturing difficulty in arranging the conductor 50 as shown in FIG. 8B on the inner wall surface 32. As in the example of the manufacturing method described above, the conductor 50 can be formed using a conductive paste by a method such as screen printing. That is, the size of the first through hole 30 is often about 1 mm to 5 mm in diameter, and the thickness of the substrate 1 is typically less than 1 mm. Therefore, even when the first through hole 30 at the time of forming the conductor 50 is in the same state as the first through hole 730 (FIG. 8A), the first through hole 30 passes through the other side of the substrate 1. The conductor 50 can also be formed on the inner wall surface 32 to such an extent that it reaches the surface 1b side or protrudes to the other surface 1b side.

Furthermore, the effect of enhancing the reliability of the connection in the through hole is similarly achieved in the second through hole 40. FIG. 9 is a schematic cross-sectional view showing the structure inside the second through hole of the photoelectric conversion element. FIGS. 9 (a) and (b) show the overlap of the film on the inner wall surface of the second through hole in the photoelectric conversion element in the conventional SCAF structure and the improved SCAF structure of the embodiment of the present invention, respectively. The connection between the back surface electrode 712 and the back surface electrode 720 (the first connection wiring layer 722 and the second connection wiring layer 724) in the second through holes 740 in the conventional photoelectric conversion element 700 is the same as that of the second through holes 740. It is limited to the area (indicated by the reference numerals 712/722/724) which is internally overlapped and in contact. This overlapping region may not have an area sufficient for the actual photoelectric conversion element 700 due to manufacturing variations. On the other hand, in the photoelectric conversion element 100 of the present embodiment, each of the back electrode 20 and the back electrode 12 extends to at least a part of the inner wall surface 42 of the second through hole 40, and the conductor 50 Preferably, an electrical path is established or enhanced in contact with both the back electrode 20 and the back electrode 12 on the inner wall surface 42 of the through hole 40. Also in this case, the conductor 50 may be disposed to fill the inside of the second through hole 40. In addition, the arrangement of the conductor 50 in the second through hole 40 also has no particular difficulty in preparation.

[2 modification]
The configuration of the photoelectric conversion element 100 of the present embodiment is merely an example. Therefore, photoelectric conversion element 100 of this embodiment is not limited to what was mentioned above, A various change or improvement can be given.

[2-1 Adoption of ENEA 60]
Although the configuration in which the ENEA 60 is formed is described in the photoelectric conversion element 100 described above with reference to FIG. 3, it is not essential that the explicit ENEA 60 is formed in the present embodiment. For example, depending on the material of the substrate 1, there is a property of releasing gas during vacuum processing. In such a case, the back electrode 20 may function as a gas barrier layer. In such a case, technical merits and demerits between providing and not providing the ENEA 60 can be taken into consideration, and the adoption or rejection of the ENEA 60 can be determined.

[2-2 Modification of ENEA 60]
Further, in the photoelectric conversion element 100 in which the ENEA 60 is formed, the shape and position of the ENEA 60 do not necessarily have to be formed at the central portion in the longitudinal direction of the unit cell 10.

Furthermore, it is also useful to provide an electrode reduction area (not shown) instead of the ENEA 60. The electrode reduced area is formed to occupy the area of the same or similar shape as the ENEA 60 on the other surface 1 b of the substrate 1. That is, the electrode reduced area is formed in at least a part of the area on the side of the other surface 1 b corresponding to the area in which the plurality of unit cells are formed. Further, in the configuration in which the electrode reduction area is provided, the back electrode 20 is formed of a laminated film of a plurality of metal layers such as the first connection wiring layer 22 and the second connection wiring layer 24 described above. In that case, the electrode reduction region is a region where at least one of the electrode layers of the laminated film forming the back electrode 20 is not formed. Therefore, there may be a back electrode 20 in which the number of layers is reduced in the electrode reduction region, and in that respect, the electrode reduction region is different from the ENEA 60. Also in this case, as described with reference to FIG. 3 for the ENEA 60, the linear portion 52 provided in the conductor 50 is at least a part of the region corresponding to the electrode reduction region on the side of one surface 1a of the substrate 1 It extends to Even with such a configuration, the same advantages as the advantage that manufacturing becomes possible due to the resource saving of the photoelectric conversion element 100 provided with the above-described ENEA 60 are realized at least to some extent.

In such a case, as an option, the photoelectric conversion element adopting a planar arrangement in which the first through holes 30 are not disposed in the electrode reduction region is, for example, to suppress the erosion of the power generation area by the first through holes 30. It is a further preferred configuration.

[2-3 Deformation of conductor 50]
Furthermore, in the structure of the first through hole 30 shown in FIGS. 7 and 8, the conductor 50 does not block the first through hole 30. However, the conductor 50 does not cover the first through hole 30. It is also possible to adopt a closed configuration. The same applies to the case where the conductor 50 is disposed on the inner wall surface 42 of the second through hole 40.

The pattern formed as the conductor 50 can also be various patterns. The typical example of the pattern of the conductor 50 formed by screen printing is illustrated below.

The extending direction of the linear portion 52 may be any of vertical, horizontal, and diagonal directions in the plane of the one surface 1a. As described above, in one typical example, at least a portion of the linear portion 52 extends in the longitudinal direction of the strip of the transparent electrode 16 from the first through hole 30 to the ENEA 60 on the side of one surface 1 a of the substrate 1. It has reached the corresponding area. At this time, the plurality of unit cells 10 are divided into strips extending in one direction, and the unit cells are arranged in the width direction of the strips.

Further, having a plurality of linear portions extending from the first through hole 30 in a plurality of directions means, for example, that the directions extending from the first through hole 30 are different by 180 degrees from each other. It is typical to have linear portions 52 of a plurality of orientations specified by angles, such as different orientations. Other than that, the linear part 52 includes one having a branched structure such as a trunk, a branch, and a twig like a branch of a tree.

The shape of the linear portion 52 of the conductor 50 of the present embodiment can be appropriately deformed and adjusted so as to satisfy the electrical requirements, the optical requirements, the mechanical requirements, and the manufacturing requirements. When the material of the linear portion 52 is the same, the substantial resistance of the transparent electrode 16 can be reduced as the number of the linear portions 52 is large, the line width is large, and the film thickness is large. In addition, as the number of linear portions 52 is smaller and the line width is smaller, the ratio of blocking light passing through the transparent electrode 16 can be reduced. Furthermore, when the substrate 1 is formed on a flexible substrate and the photoelectric conversion element 100 is desired to have flexibility, it is considered that the smaller the film thickness, the less the influence of the flexibility. As a manufacturing requirement, if the width of the linear portion 52 is generally wide, formation is easy.

Further, in the case of providing the border 54 shown in FIG. 7, the range of the border 54 is also appropriately adjusted. In general, if the border 54 is wide, it is possible to improve the performance from the electrical side. On the other hand, from the optical side, it is also considered that the light shielding by the border 54 reduces the power generation area.

And in the embodiment mentioned above, when forming the linear part 52 and the edge part 54, or forming the conductor 50 in the inner wall face of the 1st through-hole 30 or the 2nd through-hole 40, It has been described that each of the 50 parts is formed by one process. However, as long as the conductor 50 is a conductor such as a metal substantially having an electrical path, it can also be formed by combining those partially formed by a plurality of treatments.

Furthermore, in the description of the preferred configuration, the function of establishing or enhancing the electrical path on the inner wall surface 32 of the first through hole 30 and the inner wall surface 42 of the second through hole 40 has been described. However, the establishment of the electrical path by the conductor 50 and the enhancement of the electrical path are not necessarily limited to the establishment of the electrical path without conduction at all by the conductor 50 alone. Conductor 50 establishes an electrical path or enhances an electrical path as long as it functions to obviously or potentially reduce a defect in which the electrical path is stochastically incomplete due to a factor such as a variation during mass production. To perform the function.

[2-4 Unit cell 10 array modification]
Only one row of unit cells 10 is not necessarily formed on the substrate 1. Even when the series-connected unit cells 10 described above are provided in a plurality of rows (not shown), the transparent conductive material for the transparent electrode 16 is not deposited between the rows. Also in that case, it is possible to form ENEA 60. In that case, also in that case, the arrangement of ENEA 60 is at least a part of the region on the other surface 1 b side corresponding to the region in which a plurality of unit cells are formed on one surface 1 a of substrate 1 . As long as the back electrode 20 is disposed in a region where the first through holes 30 and the second through holes 40 are disposed and serial connection is established, it is not a hindrance to provide the ENEA 60 in which the back electrode 20 is not disposed.

[2-5 Material of photoelectric conversion layer 14]
The type of photoelectric conversion element employed in the photoelectric conversion element 100 of the present embodiment is not particularly limited. That is, the material of the photoelectric conversion layer 14 is a silicon (Si) layer of an nip structure in which the n layer, i layer, and p layer of the amorphous silicon described above in the column of the manufacturing method are disposed from the substrate 1 side. It is typical.

Another typical example is a compound solar cell including CIGS [Cu (In, Ga) Se2] called chalcopyrite as a material of the photoelectric conversion layer 14. In that case, the method of manufacturing the photoelectric conversion element 100, in particular, the back electrode layer forming step S106 to the transparent conductive layer forming step S116 are as follows.

First, in the back surface electrode layer forming step S106, a layer to be the back surface electrode 12 on the surface of one surface 1a of the substrate 1 is formed of molybdenum (Mo). Next, as described above, the first connection wiring layer formation step S108, the first surface patterning step S110, and the current collection hole formation step S112 are performed. After that, the p-type CIGS absorption layer and the buffer layer are formed in this order as the photoelectric conversion layer 14 in the layer of Mo to be the back surface electrode 12 formed at that time (semiconductor layer forming step S114). Furthermore, the transparent conductive layer formation process S116 which forms the transparent electrode 16 is implemented. In the case of CIGS, the transparent electrode corresponding to the transparent electrode 16 is a laminate of a high resistance transparent electrode layer and a low resistance transparent electrode layer. The p-type CIGS absorption layer is expressed by, for example, Cu (In _1-x Ga _x ) Se ₂ by an element such as Cu, In, Ga, and Se (copper, indium, gallium, selenium) and the like. is there. Here, in the p-type CIGS absorption layer, the composition is adjusted between Cu and (In + Ga) so as to be a p-type conductivity type. The material of the buffer layer may be selected _{CdS, ZnS, ZnO, ZnOH,} ZnSe, ZnIn 2 Se 4, In 2 S 3, a ZnMgO. After the transparent electrode 16 is formed, the second connection wiring layer forming step S118 to the second surface patterning step S124 are performed as described above.

In addition, the current is larger in the CIGS solar cell than in the silicon thin film photoelectric conversion element. For this reason, the reduction of the resistance of the transparent electrode 16 by adopting the conductor 50 of the present embodiment and the reduction of resistance and improvement of the reliability of series connection through the first through holes 30 or the second through holes 40 are more useful. It is. On the other hand, CIGS solar cells generally have the property of being insensitive to vacuum. That is, even if the degree of vacuum of the environment is deteriorated during the film forming process of forming the back electrode 12, the adverse effect on the performance of the photoelectric conversion element 100 after formation is slight compared to the case of the silicon based thin film solar cell. For this reason, the request | requirement of the gas barrier property with respect to degassing from the board | substrate 1 by the back surface electrode 20 mentioned above is not high, and the combination with arrange | positioning ENEA60 becomes a more preferable structure compared with the case of a silicon system photoelectric conversion element.

The embodiments of the present invention have been specifically described above. The above-described embodiments and examples are described to explain the invention, and the scope of the invention of the present application should be determined based on the description of the claims. In addition, modifications within the scope of the present invention, including other combinations of the respective embodiments, are also included in the scope of the claims.

The photoelectric conversion element of the present invention can be used for any device that generates electric power by light such as sunlight.

100 photoelectric conversion element 1 substrate 1b one surface 1a other surface 10 unit cells 10E1 and 10E2 both ends 12 back surface electrode 14 photoelectric conversion layer 16 transparent electrode 20 back surface electrode 22 first connection wiring layer 24 second connection wiring layer 30 first Through hole 32 inner wall surface 34 opening 40 second through hole 42 inner wall surface 44 opening 50 conductor 52 linear portion 54 edge portion 60 electrode non-forming area (ENEA)
SL1, SL2 separation line

Claims

A photoelectric conversion element in which a plurality of unit cells connected in series with each other is formed on one surface of a piece of insulating substrate,
Each unit cell is formed on the back surface electrode formed on the one surface of the substrate, the photoelectric conversion layer formed on the surface of the back surface electrode, and the surface of the photoelectric conversion layer And a transparent electrode,
A second through hole is formed on the other surface of the substrate, is electrically connected to the transparent electrode of one unit cell through a first through hole passing through the substrate, and the other through the second through hole through the substrate. And a plurality of back electrodes separated from one another electrically connected to the back electrode of the unit cell,
In the plurality of unit cells, the transparent electrode and the back electrode belonging to each unit cell are electrically connected to the separate back electrodes through the first through holes and the second through holes, respectively. Each unit cell is connected in series by each back electrode,
A photoelectric conversion element, wherein the transparent electrode includes a conductor formed in contact with a surface of the transparent electrode and having a linear portion extending from the first through hole.
An electrode non-forming region in which the back electrode is not formed is provided in at least a part of the region on the other side corresponding to the region in which the plurality of unit cells are formed,
The photoelectric conversion element according to claim 1, wherein the linear portion provided in the conductor extends in at least a part of a region corresponding to the electrode non-formed region on the side of the one surface of the substrate.
The plurality of unit cells are divided into strips extending in one direction, and the unit cells are arranged side by side in the width direction of the strips.
The plurality of back electrodes are divided into the back electrodes on the other surface of the substrate so as to be aligned in the direction in which the unit cells are arranged in the plurality of unit cells.
At least a portion of the linear portion of the conductor extends in the longitudinal direction of the strip of the transparent electrode from the first through hole, and corresponds to the electrode non-forming region on the side of the one surface of the substrate Reach the area,
The photoelectric conversion element according to claim 2, wherein the electrode non-forming region extends in the width direction of the strip over the range of the plurality of unit cells.
The transparent electrode and the back electrode belonging to one unit cell are electrically connected to the back electrodes different from each other through the first through hole and the second through hole, respectively, in the vicinity of both ends of the strip. Has been
The electrode non-forming region is a region of the other surface corresponding to a region extending in the width direction of the strip across the plurality of unit cells in the longitudinal central portion of the strip in each of the plurality of unit cells. Item 4. The photoelectric conversion element according to item 3.
The back electrode is formed of a laminated film of a plurality of metal layers,
An electrode in which at least one of the electrode layers of the laminated film forming the back electrode is not formed on at least a part of the area on the other side corresponding to the area where the plurality of unit cells are formed A reduction area is provided,
The photoelectric conversion element according to claim 1, wherein the linear portion provided in the conductor extends in at least a part of a region corresponding to the electrode reduction region on the side of the one surface of the substrate.
The photoelectric conversion element according to any one of claims 1 to 5, wherein the conductor covers the opening of the first through hole on the surface of the transparent electrode.
Each of the back electrode and the transparent electrode extends on at least a part of the inner wall surface of the first through hole,
The electric conductor establishes or enhances an electrical path in contact with both the back electrode on the inner wall surface of the first through hole and the transparent electrode. The photoelectric conversion element as described in a term.
Each of the back electrode and the back electrode extends on at least a part of the inner wall surface of the second through hole,
The electric conductor establishes or enhances an electrical path in contact with both the back surface electrode and the back surface electrode on the inner wall surface of the second through hole. The photoelectric conversion element as described in a term.
A plurality of first through holes are provided in each unit cell, and one linear portion of the conductor is formed to connect at least two of the first through holes in the range of one unit cell. The photoelectric conversion element according to any one of claims 1 to 5.
The linear portion of the conductor includes a plurality of linear portions extending from the first through hole toward a plurality of directions on the one surface. The photoelectric conversion element as described in 1 or 2.