JPH08340125A - Method of manufacturing thin film solar battery - Google Patents

Abstract

PURPOSE: To manufacture this thin film solar battery in small connecting resistance in hole and high conversion efficiency by a method wherein either one of both electrode layers electrically connected in a through hole of a substrate is arranged on the opposed side surface of a formed surface of the substrate while the opposing back substrate at intervals not exceeding a specific value in the regions exceeding 1/2 of the formed film region back side are arranged on said opposite side surface. CONSTITUTION: In order to connect the third electrode layer 4 on the back of a flexible substrate to the first electrode layer 3 through the intermediary of a through hole 2, the extension part of the electrode layer creeping in the through hole 2 is utilized. For this purpose, it is required that both electrode layers 3, 4 creeping in the through hole 2 come into contact with each other on the inner wall of the through hole 2 or that at least one electrode reaches from the formed surface of the through hole 2 to the opposite side aperture part without being interrupted halfway on the inner wall. Accordingly, in case of forming at least one electrode of the back substrates are opposed not exceeding 11mm in the region exceeding 1/2 of the back side of the formed region on the opposite side of the substrate, the depositing rate of an electrode layer material is decelerated to facilitate the deposition on the inner surface of the through hole 2 thereby enabling a continuous electrode layer extension part to be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film solar cell using a photoelectric conversion layer composed of an amorphous semiconductor thin film formed on a flexible substrate such as an insulating film.

[0002]

2. Description of the Related Art Solar cells have been attracting attention as clean energy, and their technological progress has been remarkable. In particular, since a photoelectric conversion layer mainly composed of amorphous silicon can be easily formed into a large area and is inexpensive, a thin-film solar cell using it is highly expected. Glass substrates have been used for conventional thin film solar cells, but they are thick and heavy, and have the drawback of being easily cracked. Also, they are thin and lightweight for reasons such as improved workability when applied to outdoor roofs. Is becoming more and more demanding. In response to these demands, a flexible thin film solar cell using a flexible plastic film or a thin metal film as a substrate is being put into practical use.

A thin film solar cell is formed by forming a photoelectric conversion layer on one surface of a substrate and providing electrode layers on both surfaces. Among the electrode layers, those existing on the light incident side are ITO or Zn.
It is a transparent electrode layer made of a transparent conductive material such as O. Since this transparent electrode layer has a large sheet resistance, a power loss due to a current flowing through the transparent electrode layer becomes large.
Therefore, conventionally, a thin film solar cell is divided into a plurality of narrow unit cells, and the divided unit cells are electrically connected to adjacent unit cells in series connection structure. On the other hand, in the thin film solar cell known in Japanese Patent Laid-Open No. 6-342924, a hole is made in the insulating substrate, and the transparent electrode layer on the opposite side of the photoelectric conversion layer is used to form a connection electrode on the back surface of the substrate by utilizing this hole. By connecting to the layer, the distance of the path of the current flowing through the transparent electrode layer having a high sheet resistance can be shortened. As a result, a thin-film solar cell that can be configured as a low-voltage, large-current type without dividing into unit cells of limited dimensions, has a small Joule loss, and has a reduced ineffective area and an increased effective power generation area is obtained. I was able to. The serial connection is facilitated by connecting the transparent electrode layer of one unit cell and the counter electrode layer of the adjacent unit cell by utilizing the connection electrode layer on the back surface of the substrate, which is particularly excellent in productivity.

2A to 2F show a manufacturing process of such a thin film solar cell. A flexible insulating substrate 1 is used for this thin film solar cell [FIG. 2 (a)]. The flexible insulating substrate 1 is a polyimide film and has a thickness of 50 μm. As the film, polyethylene naphthalate (PEN),
Any material such as polyether sulfone (PES), polyethylene terephthalate (PET), and aramid film can be used. A plurality of through holes 2 are formed in a part of the substrate 1 [FIG. 2 (b)]. The through hole 2 may be mechanically formed by using a punch, or may be formed by using an energy beam such as a laser. An Ag film having a thickness of about 100 nm to 400 nm is formed on the first electrode layer 3 as a third electrode layer 4 serving as a connection electrode layer on the surface opposite to the first electrode layer 3 by a sputtering method [FIG. )]. On this occasion,
The extension portions of the two electrode layers 3 and 4 are in contact with each other on the inner wall of the through hole 2 to connect the two electrode layers 3 and 4. In addition to Ag, a metal such as Al, Cu, or Ti may be formed as a metal electrode by a sputtering method, an electron beam evaporation method, or the like. Alternatively, a multilayer film including a metal oxide film and a metal film may be formed as the electrode layer. When the electrode layer is formed on the flexible substrate 1 having a clear through hole 2 as described above, the method of forming the film on the substrate which is in contact with the can roll also serving as a heating body cannot be adopted. Because, in the substrate with a clear through hole, the electrode material adheres to the can roll through the through hole,
The electrode material on the can roll is peeled off when another portion of the substrate comes into contact with it and redeposited on the substrate, so that the manufacturing yield of the solar cell is reduced. Therefore, the film is formed by a roll-to-roll method in which the substrate is passed close to the heating body. In the roll-to-roll method, as shown in FIG. 1, the substrate 1 conveyed from the feed roll 12 housed in the vacuum chamber 11 to the winding roll 13 is passed between the idle rolls 14 in the vicinity of the heating body 15. Then, a high voltage is applied between the target 16 and the heating body 15 to form a metal film on the substrate 1 by the sputtering rig. In this apparatus, since film formation cannot be performed only on one surface of the substrate 1,
To form the electrode layer on the opposite substrate surface, the substrate 1 is turned upside down and conveyed again between the heating body 15 and the target 16. Next, a plurality of through holes 5 are again formed in the substrate. The forming method is the same as that of the through hole 2 above [FIG.
(D)].

After passing through these steps, the thin film semiconductor layer 6 to be the photoelectric conversion layer is formed. The thin film semiconductor layer 6 is formed, for example, by a plasma CVD method using amorphous silicon (a-Si) as a main component and SiH ₄ and H ₂ as main raw material gases. The photoelectric conversion layer includes CuInSe ₂ , Cd
Any material such as Te and polycrystalline Si can be used [Fig. 2
(E)]. A transparent electrode layer which is the second electrode layer 7 is formed thereon. An oxide conductive layer of ITO, SnO ₂ , ZnO or the like is generally used for this layer, and for example, an ITO film formed by a sputtering method is used. At this time, the ITO film is not formed in the first portion of the through hole 2 which is covered with a mask when forming the film. [Figure 2
(F)]. Further, the additional third electrode layer 8 made of a low resistance conductive film such as a metal film is finally formed on the surface of the substrate 1 opposite to the surface on which the solar cell is formed [FIG. 2 (g)]. The additional third electrode layer 8 is attached to the inner wall of the through hole 5 and is also connected to the transparent electrode layer 7 attached to the inner wall of the through hole 5.

Finally, in order to form a series connection, as shown in the plan view of FIG. 3, the formed solar cells are linearly removed at regular intervals to form a plurality of electrically insulated solar cells. Form. Further, the third electrode layer 4 and the additional third electrode layer 8 are also removed by using a laser or the like at a position which has almost the same interval as the solar cell formed on the opposite surface but does not face each other, and a plurality of third electrode layers is formed. Divide into layers. At this time, in the divided third electrode layer region, the dividing line is shifted with respect to the dividing line on the surface so as to sequentially include the through holes 5 of the adjacent unit cells. By this step, one of the second electrode layers 7 of the unit cells adjacent to each other via the non-covering region is connected in series with the third electrode layer of the other cell, and finally, a plurality of the unit cells on the substrate are formed. A structure in which individual unit cells are sequentially connected in series is formed.

[0007]

In such a thin film solar cell, the connection resistance (through the through hole 2 or 5) between the electrode layer 3 or 4 on the front surface of the substrate and the third electrode layer 5, 8 on the back surface of the substrate ( Hereinafter, referred to as in-hole connection resistance) has a great influence on output characteristics. However, the in-hole connection resistance of the thin-film solar cell manufactured by the conventional method may be several Ω or infinity, the conversion efficiency may be significantly reduced, and series connection may not be formed.

An object of the present invention is to solve the above-mentioned problems and to provide a method for manufacturing a thin film solar cell having a small in-hole connection resistance and a high conversion efficiency.

[0009]

In order to achieve the above object, the first invention is to provide a first electrode layer sandwiching a photoelectric conversion layer made of a semiconductor on one surface of an insulating flexible substrate. , A transparent second electrode layer was formed, a third electrode layer was formed on the other surface of the substrate, and the first electrode layer, the second electrode layer, and the third electrode layer were formed on the substrate, respectively. In the method for manufacturing a thin-film solar cell in which at least one of the two electrode layers that wraps around the through hole is electrically connected through an extension portion of the electrode layer, both of the electrically connecting inside the through hole of the substrate are provided. At least one of the electrode layers is formed on the surface of the substrate opposite to the film-forming surface in an area of at least one-half or more on the back side of the film-forming area by 11 mm.
It is assumed that the opposing back substrates are arranged at the following intervals to form a film. In that case, the through-hole is opened by a mechanical method, and when a burr connected to one end of the through-hole occurs, the substrate surface at the other end of the through-hole is used as a film formation surface, It is preferable to form a film by disposing a back substrate so as to face the opposite surface. It is effective to form the electrode layer by a sputtering method in which the back substrate is used as a heating body of the substrate and the target is opposed to the film formation surface of the substrate. The second aspect of the present invention is the method for manufacturing a thin-film solar cell described above, wherein the outer peripheral length of the through hole is 1.8 mm or more. In any case, the first electrode layer, the photoelectric conversion layer, and the second electrode layer formed on one surface of the substrate are divided into a plurality of regions, and the third electrode layer formed on the other surface of the substrate is formed into a plurality of regions. The third electrode layer formed on the other surface of the substrate is divided into a plurality of areas, and is connected to the first electrode layer belonging to one area of each layer on the one surface of the substrate through a through hole. It is preferable to connect the third electrode layer that is located on the one surface of the substrate and the second electrode layer that belongs to a region adjacent to the region of each layer on one surface of the substrate through another through hole.

[0010]

[Function] Particularly, the third electrode layer on the back surface of the flexible substrate, which is used for series connection of the unit cells of the thin film solar cell, is connected to the first electrode layer or the second electrode layer on the front surface through the through hole of the substrate. In order to do so, the extension of the electrode layer that goes around the through hole is used. For that purpose, both of the electrode layers wrap around the through hole and come into contact with each other on the inner wall of the through hole, or at least one of the electrode layers reaches the opening on the opposite side of the film forming surface of the through hole without interruption on the inner wall. It is necessary. When the film is formed by the roll-to-roll method by the sputtering method or the plasma CVD method, if the speed of the electrode layer material particles reaching the substrate surface is high, there is a high possibility that the electrode layer material particles are not deposited on the inner wall and come off. Therefore, when at least one of the electrode layers is formed, if the back substrate is opposed to the opposite side of the substrate in the upper half of the deposition target area by 11 mm or less, the speed of the electrode layer material decreases, It is easy to deposit on the inner surface of the through hole, and a continuous electrode layer extension is formed. In particular, when the through hole is mechanically opened by using a punch or the like, burrs of the insulating substrate may occur due to the connection to the end of the through hole. There is no problem if a part of the outer circumference of the through hole is a flash-free part or if the flash is away from the inner wall of the through hole, but if the flash is protruding from the insulating substrate into the through hole on the entire circumference, this flash is Prevents connection of electrode layers. By providing the back substrate, the electrode layer material repelled by the back substrate enters the groove formed by the burr from the side opposite to the film formation surface, and the contact with the electrode layer on the opposite side is ensured, so that the inside of the hole Connection resistance is low. On the other hand, the in-hole connection resistance depends on the area of the inner wall of the through hole, that is, the length of the outer peripheral portion of the through hole. By setting the outer circumference of the through hole to be 1.8 mm or more, the deposition area of at least one of the electrode layers on both surfaces of the substrate is widened, and the connection resistance in the hole is reduced.

[0011]

EXAMPLES A method for manufacturing thin film solar cells of Comparative Examples and Examples for confirming the effects of the present invention will be described below with reference to the drawings already shown. In the manufacturing process shown in FIG. 2, the first electrode layer 3 and the third electrode layer 4 of FIG.
As shown in Table 1, the steps of forming by g-sputtering are
I went under different conditions. The distance p between the heating element and the substrate and the distance q between the target and the substrate are shown in FIG. The diameter of the through hole 2 formed in the step of FIG. 2B is 0.5 mm.

[0012]

[Table 1] In the example, the distance p between the heating element and the substrate is 0 to 3 mm because the distance between the heating element and the heating element is due to the vibration of the substrate during the transportation or the waviness in the width direction. Is not constant.

FIG. 4 shows the distribution of contact resistance in the through hole 2 between the first electrode layer and the third electrode layer thus formed. When the distance between the heating element and the substrate in the comparative example is about 15 mm, the variation in the connection resistance in the hole is very large, and the resistance of 0.2 Ω or less that does not deteriorate the characteristics of the solar cell is 60.5. %, The rate of non-defective products is very low. Furthermore, 1Ω
Six of the thirteen of the above were completely electrically open. On the other hand, the distance p between the heating element and the substrate in the embodiment is 0 to 3
In the case of mm, in most cases the connection resistance in the hole was 0.2Ω or less, and the rate of non-defective products was improved to 98.9%, and even defective products were all 0.3Ω or less, which is within the range that does not significantly affect the solar cell characteristics. It is a value.

In the present embodiment, an example in which the distance p between the heating element and the substrate is 0 to 3 mm is shown, but this distance is about 1 mm even when it is about 5 mm or about 10 mm.
Compared with the case of 5 mm, it was effective in lowering the resistance and improving the yield rate. At about 5 mm, the yield rate of non-defective products is 95.8.
%, It was 83.7% in the case of 10 mm. 10 mm
In the case of, the yield decreased, but even if the defective product was 0.
None of them were in an electrically open state at 8Ω or less.

Further, in this way, the distance p between the heating element and the substrate is
To shorten the temperature
It is not necessary to carry out over the entire region passing through the gaps, and if it is 11 mm or less in the range of 50% or more, the effect of lowering the resistance and improving the yield rate can be obtained. The same effect can be obtained with metal electrodes other than Ag. Next, as shown in FIG. 2D, a through hole 5 having a diameter of 1 mm is opened, a thin film semiconductor layer 6 is formed as shown in FIG. 2E, and then ITO sputtering is performed to form a thin film semiconductor layer 6 as shown in FIG. As shown in Table 2, the film formation process of the second electrode layer 7 and the additional third electrode layer 8 of FIG. 2G by sputtering Ag was performed under two kinds of conditions.

[0016]

[Table 2] The distance p between the heating element and the substrate is 0 to 3 mm because the distance between the heating element and the substrate is not constant because the substrate 1 vibrates during conveyance or is wavy in the width direction. is there. FIG. 5 shows the distribution of the connection resistance in the through hole 5 with the additional third electrode layer 8 with respect to the film thickness of the second electrode layer 7 thus formed. Condition A, that is, the additional third electrode layer 8
When the distance p between the heating element and the substrate when forming is about 15 mm, the variation in the in-hole connection resistance is larger than that under the condition B where p is 0 to 3 mm, and the second electrode layer 7 In some cases, when the film thickness was as thin as 70 nm or less, the resistance value was 3 Ω or more, which causes deterioration of the characteristics of the solar cell. On the other hand, the additional third electrode layer 8 has a heater body-substrate distance p of 0 to 3
In the case of the condition B in which the second electrode layer 7 was formed to have a thickness of 3 mm, the resistance value was a substantially constant value of 3Ω or less, regardless of the film thickness of the second electrode layer 7, and good characteristics were exhibited.

In condition B, an example is shown in which the distance p between the heating element and the substrate is 0 to 3 mm, but most of this distance is 3 Ω or less even when it is about 5 mm or about 10 mm. The number of non-defective products was small, and it was effective in lowering the resistance and improving the non-defective product rate as compared with the case where one of them was 15 mm. Also,
It is not necessary to shorten the distance p between the heating body and the substrate as described above over the entire region where the substrate passes between the heating body 15 and the target. If the distance is 50% or more and 11 mm or less, the resistance is constant and low. Value, good characteristics can be obtained.

Table 3 shows the formation of the third electrode layer 4 and the second electrode layer 7, and the solar cell of the comparative example in which each electrode layer was formed under the conditions shown as the comparative example in Table 1 and the condition A in Table 2. The film was formed with the distance between the heating body and the substrate p = 0 to 3 mm, but the film formation of the first electrode layer 3 and the additional third electrode layer 8 to be connected to them was p = about 1
The characteristic of the solar cell of the Example performed on condition of 5 mm is shown.

[0019]

[Table 3] In the embodiment, one of the electrode layers connected in the hole is heated by
By forming the film with the substrate-to-substrate distance p of 0 to 3 mm, the resistance in the portion of the through-hole forming the serial connection was reduced as compared with the comparative example, so that the fill factor was improved and the conversion efficiency was improved by 19%. That is, it was found that the effect of the present invention can be obtained by reducing p when forming one of the electrode layers. Furthermore, the conversion efficiency is about 6.1% when p is about 5 mm during the formation of the third electrode layer 4 and the second electrode layer 7, and about 5.9% when about 10 mm. It was confirmed that the fill factor was improved as compared with the comparative example of No. 3.

In the above examples, when the film formation was performed by the sputtering method or the film formation by plasma CVD, the same effect was obtained by bringing the ground electrode behind the substrate close. In FIG. 6, the first electrode layer 3 and the third electrode layer 4 were formed under the same conditions as in the comparative example shown in Table 1, but the distribution of the connection resistance in the hole when the diameter of the through hole was 1 mm Is the result of examining. By increasing the diameter of the through holes 2 from 0.5 mm to 1 mm, the non-defective rate was greatly improved from 60.5% to 96.3%. Also, the connection resistance in the hole of a good product is 0.
The value of 0.1Ω or less, which did not reach in the case of 5 mm,
It became possible by increasing the diameter to 1 mm. This decrease in resistance is because the length of the outer peripheral portion of the hole becomes longer, so that the contact area on the inner wall surface of the through hole 2 of the first electrode layer 3 and the third electrode layer 4 increases. A similar decrease in resistance was also observed in the in-hole connection resistance of the second electrode layer 7 and the additional third electrode layer 8. From the results of this example, the connection resistance in the hole and the yield of the non-defective product rate depend on the length of the outer peripheral portion of the hole, and it is important that the outer diameter is 1.8 mm, that is, if the outer periphery is circular, the diameter is about 0.6 mm or more. Is. In this embodiment, the shape of the hole is a circle, but it is important that the length of the outer circumference is 1.8 mm or more, and the shape of the hole may be any shape.

[0021]

According to the present invention, when a film is formed on a flexible substrate having a through hole, a substrate is placed behind the substrate at an interval of 11 mm or less to prevent the through hole from passing through the electrode layer material. By forming the extension portion of the electrode layer on the inner wall of the through hole, the connection between the electrode layers on the front and back sides of the substrate in the through hole was reduced and the resistance was lowered. In addition, the outer circumference of the through hole is 1.8
The hole connection resistance can also be reduced by setting the thickness to at least mm. As a result, it is possible to prevent the conversion efficiency from being lowered or the inability to connect in series due to the connection resistance in the hole of the thin film solar cell of the serial connection structure using the third electrode layer on the back surface of the substrate, and it is extremely effective in expanding the applications of the thin film solar cell. .

[Brief description of drawings]

FIG. 1 is a sectional view of a roll-to-roll type film forming apparatus used in an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing steps of a method for manufacturing a thin film solar cell according to the present invention in the order of (a) to (g).

FIG. 3 is a plan view of a thin-film solar cell manufactured by implementing the present invention, in which (a) is a top view and (b) is a bottom view.

FIG. 4 is a distribution diagram of in-hole connection resistance in an example of the present invention and a comparative example.

FIG. 5 is a relationship diagram of the connection resistance in the hole and the film thickness of the second electrode under two film forming conditions.

FIG. 6 is a distribution diagram of connection resistance in holes in another embodiment of the present invention.

[Explanation of symbols]

 1 Flexible Substrate 2, 5 Through Hole 3 First Electrode Layer 4 Third Electrode Layer 6 Thin Film Semiconductor Layer 7 Second Electrode Layer 8 Additional Third Electrode Layer 11 Vacuum Chamber 15 Heating Body 16 Target

Claims (5)

[Claims] 1. A first electrode layer and a transparent second electrode layer are formed on one surface of an insulating flexible substrate with a photoelectric conversion layer made of a semiconductor interposed therebetween, and a third electrode is formed on the other surface of the substrate. An electrode layer is formed, and at least one of the two electrode layers in which the first electrode layer and the second electrode layer and the third electrode layer are respectively wrapped around the through holes formed in the substrate In the method for manufacturing a thin film solar cell electrically connected via an extension portion, at least one of both electrode layers electrically connected in the through hole of the substrate, on the surface opposite to the film-formed surface of the substrate, A method for manufacturing a thin-film solar cell, characterized in that at least one-half or more regions on the back side of the film formation region are arranged with opposing backing substrates arranged at intervals of 11 mm or less. 2. A through hole is formed by a mechanical method, and when a burr connected to one end of the through hole occurs, a substrate surface at which the other end of the through hole opens is used as a film formation surface, The method for manufacturing a thin-film solar cell according to claim 1, wherein the back substrate is arranged so as to face the opposite surface of the substrate to form a film. 3. The method for producing a thin film solar cell according to claim 1, wherein the back substrate is used as a heating body for the substrate, and the electrode layer is formed by a sputtering method in which the target is opposed to the end surface of the substrate on which the film is to be formed. Method. 4. A first electrode layer and a transparent second electrode layer are formed on one surface of an insulative flexible substrate with a photoelectric conversion layer made of a semiconductor interposed therebetween, and a third electrode is formed on the other surface of the substrate. An electrode layer is formed, and at least one of the two electrode layers in which the first electrode layer and the second electrode layer and the third electrode layer are respectively wrapped around the through holes formed in the substrate A method of manufacturing a thin-film solar cell, which is electrically connected via an extension, wherein the through hole has an outer circumference of 1.8 mm or more. 5. A first electrode layer, a photoelectric conversion layer, and a second electrode layer formed on one surface of a substrate are divided into a plurality of regions, and a third electrode layer formed on the other surface of the substrate is formed into a plurality of areas. A third electrode layer that is divided into regions and is connected to the first electrode layer belonging to one region of each layer on one surface of the substrate through a through hole; and a region adjacent to the region of each layer on one surface of the substrate. The method for manufacturing a thin-film solar cell according to claim 1, wherein the second electrode layer to which the thin film solar cell belongs is connected through another through hole.