JP2000188410A - Manufacture of photovoltaic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a photovoltaic element wherein its leakage current caused by its defect portions of pin holes, etc., existing over a large area is decreased and its electromotive force characteristic in a low illuminance is made excellent. SOLUTION: In this method, there is performed the manufacture of a photovoltaic element 300, which has a process for dipping in an electrolyte the photovoltaic element (amorphous solar battery) 300 wherein at least a first electrode layer 302, a semiconductor layer 303, and a second electrode layer 304 are formed on a substrate 301, and which has a process for removing therefrom by the action of an electric field short-circuit current paths generated by the defects of the photovoltaic element 300. In this case, there are provided a reducing process for reducing in the electrolyte the second electrode layer 304 which is the defect portion of the photovoltaic element 300, and a removing process for washing by an electrolyte solution 309 a reduction substance 306 generated in the reducing process and included in the second electrode layer 304 and removing it therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a photovoltaic device, and more particularly, to a method for manufacturing a photovoltaic device having excellent characteristics by removing a short-circuit current path due to a defect.

[0002]

2. Description of the Related Art In recent years, with an increase in the area of a photovoltaic element such as a solar cell, development of a photovoltaic element having a multilayer structure in which a semiconductor layer such as amorphous silicon is formed over a large area has been advanced. Also, in order to manufacture a photovoltaic element having a large area, a continuous process method such as roll-to-roll has attracted attention.

However, it is difficult to manufacture a photovoltaic element having a multilayer structure having no defect over a large area. For example, in a photovoltaic element in which a large number of thin films of amorphous silicon or the like are stacked, pinholes and defects are generated due to the influence of dust and the like when the semiconductor layer is formed, and shunts and short circuits are likely to occur. It is known that the characteristics of photovoltaic elements are significantly reduced. It has been found that when a shunt or a short circuit occurs, the electromotive voltage characteristic is significantly reduced among the characteristics.

The causes and effects of pinholes and defects will be described in more detail. For example, in the case of an amorphous silicon solar cell deposited on a stainless steel substrate, the substrate surface cannot be said to be a completely smooth surface, but has scratches, dents, or spike-like projections. Further, an uneven electrode layer (back reflector) is provided on a stainless steel substrate for the purpose of scattering light on the substrate. for that reason,
The inability of such a thin semiconductor layer having a thickness of several hundreds of degrees to completely cover such a surface, such as p and n layers, is one of the major causes of defects and peen holes. Further, as described above, pinholes may be generated due to minute dust at the time of film formation.

[0005] As described above, the semiconductor layer between the first electrode (lower electrode) and the second electrode (upper electrode) of the solar cell is lost due to the pinhole, and the first electrode and the second electrode are lost. If the electrodes make direct contact, spike-like defects on the substrate make contact with the second electrode, or a shunt or short circuit with low resistance even if the semiconductor layer is not completely lost, light The generated current flows in parallel through the second electrode and flows into the low-resistance portion of the shunt portion or the short portion, so that the generated current is lost.
With such a current loss, the open-circuit voltage, that is, the voltage characteristic of the solar cell is significantly reduced, and the phenomenon becomes more remarkable under low illumination, which is a serious problem for a solar cell that requires power generation in all weather conditions. Becomes

When a short circuit occurs as described above, it is necessary to take measures to reduce the loss of the current generated by flowing into the low resistance portion of the short section. As such a measure, it is known to reduce or eliminate current loss by directly removing a defective portion or a pinhole, or by removing or insulating a member around a short portion.

Specifically, US Pat. No. 4,166,918
In the specification, as a method of removing a defective portion of an electrical short-circuit portion of a large-area solar cell, a method of burning a defective portion of a solar cell using a sufficiently high reverse bias voltage equal to or lower than a breakdown voltage is described. . However, in such a method, since a high reverse bias voltage is applied to the solar cell, there is a possibility that normal parts other than the defective part may be damaged when burning out the defective part,
There is a problem that the control is difficult.

Japanese Patent Publication No. 62-59901 discloses a method of burying a pinhole of a semiconductor device with a laser. However, such a method requires a special application to focus the laser on the pinhole. Further, the laser may damage other normal parts.

Further, Japanese Patent Publication No. 62-4869 discloses a method of filling a pinhole formed through an amorphous film of a photovoltaic element with an insulator. However, such a method is a method of selectively filling a pinhole with an insulator by applying light through a light-transmitting substrate after applying a photosensitive insulator, and using an opaque conductive substrate. Was not applicable, and the range of application was limited.

In US Pat. No. 4,729,970, a conversion reagent is brought into contact with a short defect portion of an electric device including a transparent conductive film to increase the resistance of a conductive film in the vicinity of the defect, thereby forming an electrode. A method for electrically insulating is disclosed. As a specific method, a reagent containing a Lewis acid (more specifically, a salt of an amphoteric element) is used.
₃ , processing is performed using a reagent containing a chloride such as ZnCl _2. However, when processing is performed using such a halide, A is contained in a photovoltaic device having a multilayer structure.
When an amphoteric metal such as 1 is used, the amphoteric metal is significantly eroded, and thus there has been a problem of side effects such as peeling during processing. In addition, there have been problems such as poor appearance and deterioration of electrical characteristics due to precipitation of metal particles in the reduction step of the second electrode layer.

Further, in US Pat. No. 5,084,400, a short defect portion of a photovoltaic element deposited on a metal substrate is formed by applying a voltage in an acid solution such as H ₂ SO ₄ to a portion near the defect. A method of electrically insulating a conductive film from an electrode by increasing the resistance of the conductive film is disclosed. Certainly, in such a method, the problem of peeling was improved by using an acid containing a sulfate group such as H ₂ SO ₄ , but when used for a long time, the acid content of the liquid was concentrated and a stable reaction was observed. Was difficult to control.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned problems and to reduce a leakage current caused by the presence of a defect such as a pinhole of a photovoltaic element over a large area, and to reduce the leakage current. An object of the present invention is to provide a method for manufacturing a photovoltaic element having excellent electromotive voltage characteristics in illuminance. Another object of the present invention is to provide a method for manufacturing a photovoltaic element having high mass productivity and high reliability.

[0013]

Accordingly, the present invention provides a photovoltaic element having at least a first electrode layer, a semiconductor layer, and a second electrode layer formed on a substrate by immersing the element in an electrolytic solution. Removing the short-circuit current path due to a defect in the photovoltaic element by the action of the photovoltaic element, reducing the second electrode layer in the defective portion of the photovoltaic element in an electrolytic solution. Providing a method for manufacturing a photovoltaic device, comprising: a reducing step of removing the reducing substance contained in the second electrode layer generated in the reducing step by washing with an electrolyte solution. I do.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In order to achieve the above-mentioned object, the present inventors have reduced the leakage current from a defective portion such as a pinhole existing in a photovoltaic element, and have further reduced the deposition of metal particles. As a result of intensive studies on a method of manufacturing a photovoltaic element that can perform stable processing for a long time without causing side effects such as
The following findings were obtained.

That is, when the photovoltaic element is immersed in the electrolytic solution and the short-circuit current path due to the defect of the photovoltaic element is removed by the action of an electric field, the second electrode layer is reduced and dissolved,
Further, by removing a reducing substance contained in the second electrode layer generated in the reduction step, the electrode layer in the middle of the reaction such as a defect peripheral portion is dissolved to dissolve the second electrode layer near the defect portion such as a pinhole. Locally increases the electrical resistance of the metal, prevents generation of leakage current, and minimizes appearance defects caused by deposition of metal and the like. As a result, it has been found that the characteristics of the photovoltaic element, particularly the electromotive voltage characteristics at low illuminance of the photovoltaic element, are improved, and the appearance defect can be prevented to a minimum.

The reduction substance generated in the reduction step and the removal of the reduction substance by washing with an electrolyte solution will be described in further detail. As described above, when the semiconductor layer has a defect, the second electrode layer in the defective portion is removed. Is electrolytically treated and dissolved by reduction to insulate it from the peripheral part, thereby preventing current generated in other parts from flowing into the defective part.

However, when reducing and dissolving the second electrode layer in the defective portion, the current at which reduction occurs in the second electrode layer even in a portion where there is no defect due to a difference in the degree of the defect and a difference in local resistance. Is generated, and reduction dissolution occurs, so that metal and the like contained in the second electrode layer are deposited around the defective portion and the like, resulting in poor appearance due to discoloration of the electrode layer and electrical characteristics due to conduction of metal particles. This causes problems such as a decrease in the temperature. In order to solve this, the reducing substance contained in the second electrode layer deposited on the surface of the photovoltaic element when the second electrode layer of the defective portion is subjected to electrolytic treatment, from the surface of the photovoltaic element It is effective to stably take in the electrolyte and remove it from the surface of the photovoltaic element.

Specifically, the removal of the precipitated reducing substance from the photovoltaic element is performed by supplying an electrolytic solution to the surface of the photovoltaic element, and forming a double salt with the reducing substance and ions contained in the solute of the electrolytic solution. And complex salts are formed and stably incorporated into the electrolyte solution. At this time, by heating the electrolyte solution at a high temperature, the degree of dissociation of the solute in the electrolyte solution increases, the number of ions for taking in the reducing substance increases, and the reaction with the reducing substance is further promoted. As a result, the metal contained in the second electrode layer, which is generated when the second electrode in the defective portion is subjected to the electrolytic treatment, is removed, the appearance defect is minimized, and the electromotive force characteristic at low illuminance is obtained. Recovery can be obtained.

The present invention has been completed on the basis of these findings, and the method for manufacturing a photovoltaic element according to the present invention comprises at least a first electrode layer, a semiconductor layer, and a second electrode layer on a substrate. A method for manufacturing a photovoltaic device, comprising: immersing the formed photovoltaic device in an electrolytic solution, and removing a short-circuit current path due to a defect in the photovoltaic device by the action of an electric field.
A reduction step of reducing the second electrode layer in the defective portion of the photovoltaic element in an electrolytic solution, and washing a reducing substance contained in the second electrode layer generated in the reduction step with an electrolyte solution. And a removing step for removing by.

A photovoltaic element having at least a first electrode layer, a semiconductor layer, and a second electrode layer formed on a substrate is immersed in an electrolytic solution, and short-circuited by a defect of the photovoltaic element due to the action of an electric field. A method for manufacturing a photovoltaic element having a step of removing a current path, wherein a reducing step of reducing the second electrode layer in a defective portion of the photovoltaic element in an electrolytic solution; and A removing step of removing a reducing substance contained in the second electrode layer by washing with an electrolyte solution. As a result, it is possible to eliminate poor appearance due to precipitation of a reducing substance contained in the second electrode layer portion generated in the reduction process of the second electrode layer, and to recover electromotive force characteristics at low illuminance. It is possible to obtain.

Further, since the reducing substance generated in the reducing step is made of the metal contained in the second electrode, it can be easily taken into the solution with an acidic solution or the like.

Further, by using the electrolyte solution used in the reduction step as the electrolyte solution in the removal step, the preparation of the electrolyte solution can be performed only once, and the operation can be performed efficiently.

In addition, since the removing step is performed by continuously spraying the electrolyte solution onto the surface of the photovoltaic element, a new electrolyte solution is always supplied to the surface of the photovoltaic element, and the reaction of the defective portion is performed. Can be completely removed without stopping the reaction due to the equilibrium state of the second electrode layer.

Further, the removing step is performed by immersing the photovoltaic element in the electrolyte solution, so that the electrolyte solution spreads over the entire surface of the photovoltaic element and is surely contained in the second electrode layer. Reduced substances can be removed.

Further, by heating the electrolyte solution used in the removal step to 20 ° C. to 60 ° C., the reaction for taking the reducing substance into the solution is promoted, and the treatment can be performed in a short time. The reaction can be performed without imposing a burden on the user.

Further, the electrolyte can be selected according to the type of the second electrode layer to be laminated, so that an electrolytic solution suitable for the production conditions can be obtained.

Further, the hydrogen ion concentration of the electrolytic solution used in the reduction step is set to 1.0 × 10 ^{−3.0 to} 1.0 × 10 ^−1.0 m
By adjusting the concentration to ol / l, the metal contained in the second electrode layer is less likely to be taken into the electrolytic solution, and the first electrode layer does not peel off, and the photovoltaic device has good electromotive voltage characteristics. Can be manufactured stably.

Further, since an electric field is generated by applying a bias to the photovoltaic element, various electric field conditions can be selected.

Further, by applying the bias to the photovoltaic element in the forward direction, the processing can be performed without adversely affecting the normal part of the photovoltaic element.

Further, by irradiating the photovoltaic element with light, an electric field is generated by the electromotive voltage of the photovoltaic element body, so that an unreasonable electric field is not applied to the photovoltaic element, and the defective part is not affected. The action of the electric field is ensured, and the characteristics can be recovered.

Further, by using a conductive substrate as the substrate, it is possible to easily take out the electrodes and the like during the electrolytic treatment, and to carry out the treatment easily.

Further, by forming the first electrode layer into a plurality of layers including at least one kind of metal layer, the effect of reflection at the time of light incidence is increased, and a photovoltaic element having good characteristics is manufactured. be able to.

Further, a photovoltaic element having a large area by roll-to-roll can be manufactured by using an amorphous semiconductor for the semiconductor layer.

Further, since the second electrode layer is made of a metal oxide, a reduction reaction can be caused to occur preferentially in the second electrode layer over the semiconductor layer, and an electrical short circuit at a defective portion can be eliminated.

An embodiment of the present invention will be described below with reference to the drawings.

First, the photovoltaic device manufactured according to the present invention will be described.

FIG. 1 is a schematic view showing an example of a photovoltaic element manufactured according to the present invention. FIG. 1 (a) is a sectional view and FIG. 1 (b) is a plan view.

FIG. 1 shows a photovoltaic device 100 having an amorphous silicon semiconductor layer. The photovoltaic device 100 has a plurality of pin junctions 103, 113 and 123 which generate a current flow in response to absorption of incident light. Having a semiconductor layer 110 composed of. 101 is a substrate that supports the solar cell body, 102 is a first electrode layer, 104 is a second electrode layer made of a transparent conductive film, 105 is a grid electrode used as a current collecting electrode, and 106 is a photovoltaic element. Defects such as existing pinholes and the like, 107 is a high-resistance portion removed and reduced, 108 is a plus electrode (plus tab), and 109 is a minus electrode (minus tab).

FIG. 1 shows an amorphous silicon-based photovoltaic element in which light enters from the side opposite to the substrate. Although the present invention can be used with respect to the manufacture of such a photovoltaic device, the present invention is not limited to a method of manufacturing a photovoltaic device having such a specific structure or shape.

(Substrate 101) The substrate 101 is a substrate that mechanically supports the semiconductor layer 110 in the case of a photovoltaic element having a configuration in which multilayer thin films made of amorphous silicon or the like are stacked, and is also used as an electrode at the same time. In some cases.

The substrate 101 is, for example, a stainless steel substrate,
A conductive member such as a metal member such as a tin metal foil or a conductive film deposited on at least a portion of glass or a synthetic polymer resin is preferable.

(First electrode layer 102) First electrode layer 10
Reference numeral 2 denotes one electrode for extracting the power generated by the semiconductor layer 110, and the semiconductor layer 110 is required to have a work function that serves as an ohmic contact.
It is preferable that the first electrode layer is textured in order to cause irregular reflection of light to improve electromotive current characteristics.

The material of the first electrode layer 102 is preferably Al, Ag, Pt, ZnO, In ₂ O ₃ , ITO,
A metal body or alloy such as AlSi and a transparent conductive oxide (TCO) are used. As a method for forming the first electrode layer, a method such as plating, vapor deposition, or sputtering is suitable.

Here, it is important for the first electrode layer 102 to include a metal layer made of a metal or a metal alloy having high conductivity and high reflectivity in order to improve the characteristics of the photovoltaic element. is there. Further, the first electrode layer is preferably formed from a plurality of layers including at least one type of metal layer. For example, when the first electrode layer has a configuration in which a metal layer and a transparent conductive oxide layer are sequentially stacked on the substrate 101, a problem arises in that the first electrode layer is alloyed at the interface between the metal layer and the semiconductor layer 110, thereby increasing the series resistance. Is preferred because there is no

(Semiconductor Layer 110) As the semiconductor layer 110, when an amorphous silicon-based photovoltaic element is taken as an example, a-Si, a
So-called IVB group and IV such as -SiGe, a-SiC, etc.
A group B alloy-based amorphous semiconductor is exemplified. The semiconductor material constituting the p-type layer or the n-type layer can be obtained by doping a valence electron controlling agent into the above-described semiconductor material constituting the i-type layer. As a valence electron controlling agent for obtaining a p-type semiconductor, a compound containing a Group IIIB element is used. Group IIIB elements include B, Al, Ga,
In is mentioned. As a valence electron controlling agent for obtaining an n-type semiconductor, a compound containing a VB group element is used.
Group VB elements include P, N, As, and Sb.

The amorphous silicon semiconductor layer may be formed by vapor deposition, sputtering, RF plasma, microwave plasma CVD, ECR, thermal CVD, LPC, or the like.
A known method such as a VD method is used as needed. Further, in order to obtain a large-area substrate, a method in which a substrate is continuously transported by a roll-to-roll method to form a film is used.

The present invention relates to a device having only one semiconductor junction (pin junction or pn junction), a so-called tandem cell having two or more layers, or a triple cell as shown in FIG. 1 for the purpose of improving spectral sensitivity and voltage. Can also be used.

(Second electrode layer 104) Second electrode layer 10
Reference numeral 4 denotes an electrode for extracting an electromotive force generated in the semiconductor layer 110, and forms a pair with the first electrode layer 102.

The second electrode layer 104 is necessary for a photovoltaic device using a semiconductor having a high sheet resistance, such as an amorphous silicon photovoltaic device. The second electrode layer 104 is required to be transparent because it is located on the light incident side, and is also called a transparent electrode. Second electrode layer 104
In order to efficiently absorb light from the sun, a fluorescent lamp, or the like into the semiconductor layer 110, it is preferable that the light transmittance is 85% or more. To make it flow laterally to 110,
The sheet resistance is desirably 100Ω / □ or less.

As a material having such properties, SnO
₂ , In ₂ O ₃ , ZnO, CdO, CdSnO ₄ , ITO
(Indium tin oxide) and the like.

(Grid electrode 105) Grid electrode 10
5 is generated in the semiconductor layer 110 and the second electrode layer 104
The current extracted by the above is further collected.

The grid electrode 105 is formed in a comb shape, and a suitable width, pitch and the like are designed and determined from the magnitude of the sheet resistance of the second electrode layer 104. It is required that the grid electrode 105 has a low specific resistance and does not become the series resistance of the photovoltaic element. As a specific method for forming the grid electrode 105, a method of forming a paste by mixing a powder of a metal such as Ag, Ni, Al, Ti, Cr, W, and Cu with a polymer binder and a solvent, and forming the paste by a screen printing method. And a method of directly forming by a vapor deposition method, a soldering method, a plating method, and a method of laying the metal in a wire form.

(Defective portion 106) In the amorphous silicon-based photovoltaic device described above, the semiconductor layer 1 to be deposited
Numeral 10 is a thin film layer having a total thickness of about 4000 °. For this reason, when there are protrusions and foreign matter from above and below, it is difficult to sufficiently cover the protrusions and foreign matter by deposition.

For example, in the case where the substrate 101 is made of stainless steel and the semiconductor layer 110 is continuously deposited thereon, even if the surface of the substrate 101 is smoothed, it is possible to eliminate projections, dents and distortions at all. Have difficulty. Further, during the transfer of the continuous film formation, mechanical dents and scratches are generated from the back side of the substrate 101 to a considerable extent. Therefore, 1 μm
The above unevenness causes mechanical damage to the semiconductor layer 110 and leads to the generation of the defective portion 106. For example, the substrate 10
If the height of the protrusion from one surface is large, the semiconductor layer 110 cannot cover the protrusion, and then the second electrode layer 10
3 are directly laminated on the protrusions, and the substrate 101 or the first electrode layer 102 and the second electrode layer 103 are in direct contact with each other, causing a shunt or short circuit. Further, when dust or the like is deposited during the formation of the semiconductor layer 110, an unformed portion of the semiconductor layer 110 is formed or peeled off, which not only causes a pinhole, but also causes the second electrode layer 1
03 is directly formed on the first electrode layer 102 and the substrate 101, causing a shunt and a short circuit.

The presence of these defects affects the voltage characteristics at low illuminance. That is, the photovoltaic current of the photovoltaic element increases linearly with increasing illumination, but the resulting electromotive voltage increases exponentially. That is, when the illuminance is strong, there is almost no difference in the electromotive voltage under extreme illumination of AM-1 regardless of the degree of the defect, but as the illuminance decreases, the difference between the defective and the non-defective appears. . This tendency becomes more remarkable when the illuminance is 1000 Lux or less. For this reason, it is important to eliminate the influence of a defect indoors or in an environment where sunlight hardly gathers.

(High-resistance part 107) By using the present invention, a high-resistance part 107 is formed in a part of the second electrode layer 104 on the defect part 106 in the semiconductor layer 110 of the photovoltaic element 100. By doing so, a current path to the defective portion 106 is prevented. At this time, since the resistance of the second electrode layer 104 is increased only in the vicinity of the defective portion 106, the resistivity itself of the second electrode layer 104 does not increase. Does not increase.

Next, the manufacturing method according to the present invention will be described.

(Reduction Step) FIG. 2 is a schematic sectional view showing an example of an apparatus for performing the reduction step of the present invention.
Indicates a device using an external power supply. In FIG. 2, reference numeral 200 denotes a photovoltaic element, 201 denotes a substrate, 202 denotes a first electrode layer,
Reference numeral 203 denotes a semiconductor layer having a p-layer deposited on the uppermost layer (the left side in FIG. 2), 204 denotes a second electrode layer, 205 denotes a defect,
6 is an electrolytic treatment tank, 207 is an electrolytic solution, 208 is a counter electrode,
Reference numeral 209 denotes a power supply.

As described above, according to the present invention, the defect 2
A current path to the defective portion 205 is prevented by forming a high-resistance portion in a part of the second electrode layer 204 above the second electrode layer 204.
Is achieved by reducing a part of

Hereinafter, description will be made with reference to FIG. The photovoltaic element 200 is immersed in the electrolytic solution 207 in the electrolytic treatment tank 206, connected to the negative electrode side of the power source 209, and
8 is connected to the positive pole side. That is, the photovoltaic element 20
The mechanism is such that a bias voltage is applied to 0 in the forward direction. At this time, when a bias voltage is applied between the electrodes, current flows preferentially through the defective portion 205 having a low resistivity using the electrolyte 207 as a medium. At this time, nascent hydrogen (active hydrogen) is generated on the side of the photovoltaic element 200 on the side of the cathode, and between the periphery of the defect 205, that is, the portion corresponding to the upper part of the defect 205 of the second electrode layer 204. A chemical reaction occurs. That is, the second electrode layer 204 made of a metal oxide or the like is reduced. At the same time as the reduction reaction, dissolution of the reaction product in the electrolytic solution starts, and the dissolved portion has a shape in which the second electrode layer 204 is missing, and substantially from the lateral direction via the second electrode layer 204. The path of the leakage current flowing into the defective portion 205 is cut off.

The above-mentioned electric field can also be generated by irradiating the photovoltaic element with light in an electrolytic solution. At this time, the electromotive voltage itself generated by the photovoltaic element by light becomes the applied bias voltage. Note that bias conditions can be controlled by the intensity of irradiation light.

The electrolytic solution 207 used here is not particularly limited as long as it can electrically dissolve the second electrode layer 204, but is preferably an acidic solution, and the second electrode layer formed in the reduction step is preferably used. It is preferable to contain ions for taking in a reducing substance contained in the layer 204. Specific examples include those selected from at least one selected from the group consisting of sulfates, acetates, oxalates, and selenates. These acidic solutions stably take in the reduced substances that have been reduced and dissolved in the electrolytic solution as complex salts or double salts.

In order to prevent the first electrode layer 202 from peeling off and to stably take in the reducing substance, the electrolyte 20
7 has a hydrogen ion concentration of 1.0 × 10 ^{-3 to} 1.0 × 10 ^-1
mol / l is preferred.

(Removal Step) According to the present invention, the reducing substance generated in the electrolytic treatment of the photovoltaic element is stably taken into the electrolytic solution by washing with the electrolytic solution.

FIG. 2 is a schematic sectional view showing an example of an apparatus for performing the removing step of the present invention, and shows an apparatus for directly injecting an electrolytic solution onto the surface of a second electrode layer of a photovoltaic element. . In FIG. 3, reference numeral 300 denotes a photovoltaic element, 301 denotes a substrate, 302 denotes a first electrode layer, 303 denotes a semiconductor layer having a p-layer deposited on the uppermost layer, 304 denotes a second electrode layer, and 305 denotes a defect portion. A high resistance portion from which the second electrode layer has been removed; 306, a reducing substance generated in the reducing step; 307, a cleaning tank; 308, a nozzle for injecting an electrolyte solution;
9 is an electrolyte solution, 310 is an electrolyte solution circulation device, 311
Denotes an electrolyte solution recovery dish, and 312 denotes a heat source (heater).

In the present invention, the reducing substance contained in the second electrode layer generated on the surface of the photovoltaic element is removed by supplying an electrolytic solution to the surface of the photovoltaic element to reduce the solute of the reducing substance and the electrolytic solution. This is achieved by forming a double salt or complex salt with the contained ions and stably incorporating the ions into the electrolyte solution.

This will be described with reference to FIG. Cleaning tank 307
The photovoltaic element 300 is disposed inside, and the electrolyte solution 309 is jetted from the nozzle 308 to the surface of the photovoltaic element. In order to always fill the surface of the photovoltaic element 300 with the active electrolyte solution, the injection pressure of the electrolyte solution is 1.0 to 3.0 kg / cm.
^{2. The} injection rate is preferably 1 to 30 liter / min. At this time, if the electrolyte solution 309 is heated to 20 ° C. to 60 ° C. using the heat source 312 such as a throw heater, the degree of dissociation of the solute of the electrolyte solution 309 increases, and the reducing substance 30
The number of ions for taking in 6 increases, and the reaction with the reducing substance 306 is also promoted, so that processing can be performed in a short time. The end point of these reactions is a point at which discoloration due to deposition of metal on the surface of the photovoltaic element 300 disappears and there is no difference in color from the peripheral portion, and can be controlled by a change in color. As described above, the reducing substance 306 contained in the second electrode layer which is generated when the second electrode layer in the defective portion is subjected to the electrolytic treatment is removed by washing the surface of the photovoltaic element with the electrolyte solution 309. After that, by performing washing and drying with water, it is possible to minimize the appearance defect and to recover the electromotive force characteristics at low illuminance.

The method of cleaning with an electrolyte solution in the removing step is not particularly limited, and may be performed by immersing the photovoltaic element in the electrolyte solution.

Further, as the electrolyte solution, the same electrolyte solution as that used in the above-described reduction step can be used, and the electrolyte solution used in the reduction step can be used as it is as the electrolyte solution.

[0070]

Hereinafter, embodiments of the present invention will be described in detail.
The present invention is not limited to these examples.

Example 1 As an example of the photovoltaic element of the present invention, a solar cell 100 having a pin junction type triple configuration as shown in FIG. 1 was manufactured.

First, on a roll-shaped stainless steel 430BA substrate 101, as a first electrode layer 102, an Al layer was formed by sputtering at 1000 ° C., and then a ZnO layer was formed to a thickness of 1 μm.
m. Thereafter, the film was placed in a plasma CVD film forming apparatus (not shown) and deposited in the order of an n-type layer, an i-type layer, and a p-type layer to form a bottom layer (pin junction) 103. At this time, the i-type layer is a
-SiGe layer. Next, a middle layer (pin junction) 113 was formed by depositing an n-type layer, an i-type layer, and a p-type layer in this order. The i-type layer was an a-SiGe layer like the bottom layer.
Next, an n-type layer, an i-type layer, and a p-type layer were sequentially deposited to form a top layer (pin junction) 123. The i-type layer was an a-Si layer. Note that the n-type layer and the p-type layer were all a-Si layers. Further, the i-type layer of the bottom layer and the i-type layer of the middle layer were formed by microwave plasma CVD, and the other layers were formed by RF plasma CVD. Next, as a transparent second electrode layer 104 having a function also having an anti-reflection effect, ITO was deposited at 700 °. Thus, a photovoltaic element was formed.

Next, this photovoltaic element was cut into a 31 cm × 31 cm square, and 30 cm by a known chemical etching method.
After subcell patterning to a size of 30 cm square, it was set in the electrolytic processing apparatus shown in FIG. The back side of the photovoltaic element 200, that is, the stainless steel substrate side was connected to the minus pole side of the power supply 209, and the 31 cm square SUS316 counter electrode 208 was connected to the plus pole side. As the electrolytic solution 207, a 20% solution using aluminum sulfate octahydrate as an electrolyte was used. At that time, the conductivity of the electrolyte was 32.0 mS / c.
m and the hydrogen ion concentration were 1.0 × 10 ^−2.02 mol / l. The liquid temperature was 25.0 ° C., the same as room temperature.

The electrolysis conditions were as follows: the distance between the electrodes was 4.0 cm;
Five pulse voltages were applied with an applied voltage of 5.0 V, an applied time of 0.3 seconds, and an applied interval of 0.1 seconds. After the electrolysis is completed, the photovoltaic element 300 on the surface of which the reducing substance contained in the second electrode layer has been generated is set in the processing apparatus shown in FIG. 3, and the electrolytic solution used for the electrolytic treatment is used as the electrolytic solution 309, After jetting continuously from the nozzle 308 for 10 minutes to remove discolored portions on the surface, washing with water and drying were performed. Thereafter, an electrode in which a copper wire was covered with a carbon paste was bonded by a thermocompression bonding apparatus to form a grid electrode 105. Positive electrode 108 and grid electrode 1 using copper foil
05, and the negative electrode 109 was soldered and connected to the SUS substrate 101 on the back surface to obtain a solar cell.

The initial characteristics of these samples were measured as follows.

First, the voltage-current characteristics in the dark state were measured.
When the shunt resistance was calculated from the inclination near the origin, no shunt occurred at an average of 200 kΩ · cm ² .
Next, when the electromotive voltage was measured while changing the illuminance using a fluorescent lamp device, a result as shown in FIG. 4 was obtained, and an electromotive voltage of 1.2 V or more was obtained even under an illuminance of 200 Lux. Further, a pseudo solar light source (SPIRE) having a light intensity of 100 mW / cm ^{2 in} the solar spectrum of AM1.5 global
(Manufactured by the company) and the conversion efficiency was determined to be 9.0% ± 0.2%, which was good. Further, when the active area of the solar cell was observed with a microscope in detail, no metal particles considered to be generated from the second electrode layer were observed. At this time, the yield was 98%.

Further, these samples were laminated by a known method to form a module, and the reliability test was performed according to Japanese Industrial Standard C8.
917 was performed based on the temperature-humidity cycle test A-2 specified in the environmental test method and the durability test method of the crystalline solar cell module.

The sample was put into a thermo-hygrostat capable of controlling the temperature and humidity, and a cycle test in which the temperature was changed from −40 ° C. to + 85 ° C. (relative humidity: 85%) was repeated 20 times. Next, the sample after completion of the test was measured by a simulator in the same manner as in the initial stage. As a result, only 2.0% of the initial conversion efficiency deteriorated on average, and no significant deterioration occurred.

From the results of this example, it can be seen that the photovoltaic element manufactured according to the present invention has good yield, good characteristics, good appearance, and excellent reliability.

Example 2 FIG. 1 was similar to Example 1 except that the removing step was performed by immersion in an electrolyte solution.
A solar cell 100 as shown in FIG.

That is, after the reduction step is completed, the photovoltaic element having the surface on which the metal particles contained in the second electrode layer are generated is set in a solution immersion-type processing apparatus containing an electrolyte solution, and is set for 10 minutes. After leaving to remove discolored parts on the surface,
And washing with water and drying were performed.

The initial characteristics of these samples were measured in the same manner as in Example 1. As a result, the electromotive voltage at an illuminance of 200 Lux was 1.20 V on average, and the conversion efficiency was 9.2, which was good at 0.3%. In addition, a precipitate which was considered to be a reducing substance was not observed.

(Comparative Example 1) A solar cell 100 was manufactured in the same manner as in Example 1 except that the removing step was not performed. The photovoltaic element immediately after washing and drying after the reduction step,
The second electrode layer was discolored in some places and was rough as if dusted.

When the shunt resistance was measured in the same manner as in Example 1, there were some shunt resistors with an average of 50 kΩcm ² near the shunt. When the electromotive voltage at low illuminance was measured, as shown in FIG.
The electromotive voltage value at 0 Lux or less became a low value. Further, the conversion efficiency had a large variation of 8.0% ± 1.6%. In addition, according to observation with a microscope, metal precipitates that were regarded as reducing substances were observed in the discolored portion on the surface of the second electrode layer around the defect. When the shunt resistance was low and the efficiency was not good, metal grains were located under the grid electrode. In addition, metal particles considered to have been generated when the second electrode layer was reduced were observed even in a portion having no defect.

Further, these samples were laminated by a known method to form a module, and a reliability test was performed in the same manner as in Example 1. As a result, a 10% reduction in efficiency and a 15% reduction in shunt resistance were found. Was done. According to microscopic observation,
This was because the metal particles formed during the electrolytic treatment entered the defective portion due to moisture and heat shrinkage, causing conduction.

Example 3 A solar cell 100 as shown in FIG. 1B was produced in the same manner as in Example 1 except that aluminum acetate was used as the electrolyte for the electrolytic solution 207. At this time, the conductivity of the electrolyte 207 is 41 mS / cm,
The hydrogen ion concentration was 1.0 × 10 ^−2.9 mol / l.

The electrolysis conditions were such that the distance between the electrodes was 4.0 cm,
The application voltage was 4.5 V, the application time was 0.3 seconds, the application interval was 0.1 second, and the pulse voltage was applied five times.

The initial characteristics of these samples were measured in the same manner as in Example 1. As a result, the electromotive voltage at an illuminance of 200 Lux was 1.21 V on average and the conversion efficiency was 9.2 ± 0.1%. In addition, a precipitate which was considered to be a reducing substance was not observed.

FIG. 5 shows the relationship between the hydrogen ion concentration of the electrolyte and the electromotive voltage characteristics of the solar cell at low illuminance (200 Lux). As shown in FIG. 5, since the precipitation of the reducing substance contained in the second electrode layer can be prevented and the first electrode layer can be prevented from peeling off, the hydrogen ion concentration of the electrolytic solution is 1.0 ×
It is preferably from 10 ^{−3.0 to} 1.0 × 10 ^−1.0 mol / l.

(Example 4) The electrolytic solution in the removing step was changed to 5
A solar cell 100 as shown in FIG. 1B was produced in the same manner as in Example 1 except that the heating was performed at a high temperature of 0 ° C.

When the initial characteristics of these samples were measured in the same manner as in Example 1, the electromotive voltage at an illuminance of 200 Lux was 1.21 V on average and the conversion efficiency was 9.0 ± 0.2%, which was good. In addition, precipitates and the like, which are considered to be metal particles as reducing substances, were not observed.

FIG. 6 shows the relationship between the temperature of the electrolyte solution and the time required for cleaning the solar cell. As shown in FIG. 6, since the processing time is short and the load on the apparatus is small, the solution temperature 2
It is preferable to set the temperature to 0 ° C to 60 ° C.

(Example 6) In this example, a solar cell 100 was manufactured in the same manner as in Example 1 except that an electric field was generated by light irradiation.

That is, a patterned photovoltaic element produced in the same manner as in Example 1 was set in a treatment tank containing an electrolytic solution, with the light irradiation surface (second electrode layer side) facing upward. Light with a light intensity of approximately 100 mW / cm ² was irradiated for 60 seconds from a light irradiation unit 210 formed of a metal halide lamp. Then, as in the first embodiment, FIG.
A solar cell as shown in FIG.

When the initial characteristics of these samples were measured in the same manner as in Example 1, the electromotive voltage at an illuminance of 200 Lux was 1.22 V on average and the conversion efficiency was 9.0 ± 0.2%, which was good. In addition, precipitates of metal particles, which are considered to be a reducing substance, were not observed.

[0096]

According to the method for manufacturing a photovoltaic element of the present invention, there is provided a photovoltaic element which is excellent in initial characteristics and long-term reliability without problems of appearance defects and characteristic defects due to residual metal particles. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a photovoltaic device manufactured according to the present invention.

FIG. 2 is a schematic cross-sectional view showing one example of an apparatus for performing the reduction step of the present invention.

FIG. 3 is a schematic cross-sectional view showing one example of an apparatus for performing a removing step of the present invention.

FIG. 4 is a graph showing electromotive force characteristics at low illuminance of the solar cells manufactured according to Example 1 and Comparative Example 1.

FIG. 5 is a graph showing a relationship between a hydrogen ion concentration of an electrolytic solution and an electromotive voltage characteristic at low illuminance of a solar cell in Example 4.

FIG. 6 is a graph showing the relationship between the temperature of the electrolyte solution and the time required for cleaning the solar cell in Example 5.

[Explanation of symbols]

100, 200, 300 Photovoltaic element (amorphous solar cell) 101, 201, 301 Substrate 102, 202, 302 First electrode layer 103, 113, 123 Pin junction 104, 204, 304 Second electrode layer 105 Grid electrode 106, 205 Defect 107, 305 High resistance 108 Positive electrode (plus tab) 109 Negative electrode (minus tab) 110, 203, 303 Semiconductor layer 206 Electrolytic treatment tank 207 Electrolyte 208 Counter electrode 209 Power supply 306 Reducing material 307 Cleaning treatment tank 308 Nozzle 309 Electrolyte solution 310 Electrolyte solution circulation device 311 Electrolyte solution recovery dish 312 Heat source

Claims (15)

[Claims] 1. A photovoltaic device having at least a first electrode layer, a semiconductor layer, and a second electrode layer formed on a substrate is immersed in an electrolytic solution, and the defect of the photovoltaic device is caused by the action of an electric field. A method of manufacturing a photovoltaic device having a step of removing a short-circuit current path by reducing a second electrode layer in a defective portion of the photovoltaic element in an electrolytic solution; And removing the reducing substance contained in the second electrode layer by washing with an electrolyte solution. 2. The method according to claim 1, wherein the reducing substance is made of a metal contained in the second electrode layer. 3. The method according to claim 1, wherein the electrolytic solution used in the reduction step is used as an electrolyte solution in the removal step. 4. The photovoltaic device according to claim 1, wherein the removing step is performed by continuously spraying the electrolyte solution onto the surface of the photovoltaic device. Production method. 5. The method according to claim 1, wherein the removing step is performed by immersing the photovoltaic element in the electrolyte solution. 6. The electrolyte solution used in the removing step,
The method for producing a photovoltaic device according to any one of claims 1 to 5, wherein the heating is performed at 20 ° C to 60 ° C. 7. The electrolyte used in the reduction step is at least one selected from the group consisting of sulfate, acetate, oxalate, and selenate.
7. The method for manufacturing a photovoltaic device according to any one of claims 6 to 6. 8. The electrolyte used in the reduction step has a hydrogen ion concentration of 1.0 × 10 ^{−3.0 to} 1.0 × 10 ^−1.0 mol.
The method of manufacturing a photovoltaic device according to any one of claims 1 to 7, wherein the ratio is / l. 9. The method for manufacturing a photovoltaic device according to claim 1, wherein the electric field is an electric field generated by applying a bias to the photovoltaic device. 10. The method according to claim 9, wherein the bias is applied to the photovoltaic device in a forward direction. 11. The photovoltaic element according to claim 1, wherein the electric field is an electric field generated by an electromotive voltage of the photovoltaic element main body when the photovoltaic element is irradiated with light. Of manufacturing a photovoltaic element. 12. The method for manufacturing a photovoltaic device according to claim 1, wherein said substrate is a conductive substrate. 13. The photovoltaic device according to claim 1, wherein the first electrode layer is formed of a plurality of layers including at least one kind of metal layer. Method. 14. The method according to claim 1, wherein said semiconductor layer is made of an amorphous semiconductor. 15. The method according to claim 1, wherein the second electrode layer is formed from a metal oxide.