JPH06318723A - Photovoltaic element and its manufacture - Google Patents

Abstract

PURPOSE:To improve the characteristics and reliability of a photovoltaic element by providing an electrode layer between an upper electrode and a grid electrode respectively composed of semiconductor layers and an insulating layer between the upper electrode and the electrode layer. CONSTITUTION:This element has at least semiconductor layers 103, 104, and 105 formed on a substrate 101 and a high-resistance electrode layer and a low- resistance electrode for preventing short-circuit currents. An insulating layer 107 is provided between the semiconductor layers 103, 104, and 105 and the electrode layer 108 and the electrode layer 108 is electrically connected to the semiconductor layer 103, 104, and 105 through the insulating layer 107. The layer 107 is composed of a high polymer resin selected from among polyester, ethylene-vinyl acetate copolymer, acrylic resin, epoxy resin, and polyurethane and has transmissivity of >=50% against the sunlight. Therefore, a photovoltaic element having high initial characteristics and excellent durability can be obtained, because the internal defect of the element can be sealed and the void content of the electrode layer can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device having good characteristics and high reliability, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Photovoltaic modules are widely applied as power sources for consumer equipment such as calculators and wristwatches.
It is drawing attention as a technology that can be put to practical use as an alternative power source for so-called fossil fuels such as oil and coal. The photovoltaic element used in this photovoltaic module includes a single crystal semiconductor, a polycrystalline semiconductor, a thin film semiconductor, and the like. Among them, the thin-film photovoltaic element is that a film having a large area can be produced as compared with the single crystal photovoltaic element, and that the film thickness can be thin.
It has advantages such as being able to be deposited on any substrate material, and is considered promising.

A thin film photovoltaic element is a semiconductor pn junction, p
This is a technology that uses the diffusion potential generated in a semiconductor junction such as an in-junction or a Schottky junction. A semiconductor such as silicon absorbs sunlight to generate photocarriers for electrons and holes, and the photocarriers are joined. The internal electric field generated by the diffusion potential of the part causes the electric field to drift to the outside. As a semiconductor material for such a photovoltaic element, a material using a tetrahedral amorphous semiconductor such as amorphous silicon, amorphous silicon germanium, or amorphous SiC can be used.

The structure of an amorphous silicon photovoltaic element is, for example, a p layer composed of a thin p layer, an i layer and an n layer on a substrate.
It is configured by stacking in-junctions. In addition, a so-called tandem cell in which two or more pin junctions are stacked in series has been studied to improve conversion efficiency. A pair of electrodes, an upper electrode and a lower electrode, are provided on the light incident side and the back surface side of the semiconductor. The upper electrode is a transparent conductive film, and a comb-shaped grid electrode is formed thereon as a collector electrode so as not to prevent the incidence of light. Further, a bus bar for collecting the current of the grid electrode is provided. The grid electrode can be formed by using a vacuum process such as a sputtering method or an evaporation method, but a mask for patterning is required, the evaporation material of the mask portion is wasted, and the film formation time is long. There is a problem in mass productivity. On the other hand, a screen printing method using a conductive paste has been put into practical use as a method suitable for mass production with high throughput.

By the way, when the photovoltaic module is used, for example, for supplying electric power to general households, an output of about 3 KW is required, and when a photovoltaic module with a conversion efficiency of 10% is used, it has a large area of 30 m ^2. Photovoltaic modules are required. However, in the manufacturing process of a photovoltaic element, it is difficult to manufacture a photovoltaic element having no defects over a large area. For example, in a polycrystal, a low resistance portion is generated in a grain boundary portion. Also, in thin-film photovoltaic modules such as amorphous silicon, pinholes and defects occur due to the influence of dust during semiconductor layer formation, causing shunts and shorts. Is known to be significantly reduced.

The cause of pinholes and defects and their effects will be described in more detail. For example, in the case of an amorphous silicon photovoltaic element deposited on a stainless steel substrate, the substrate surface cannot be said to be a completely smooth surface and may be scratched or damaged. Due to the presence of dents or spike-like protrusions and the provision of a back reflector having irregularities on the substrate for the purpose of irregularly reflecting light, a thin semiconductor layer with a thickness of several tens nm, such as p and n layers, is formed. Such surface cannot be completely covered, or another cause is that pinholes are generated due to dust during film formation.

Amorphous silicon photovoltaic devices
Generally, semiconductors have high sheet resistance, so semiconductors
Requires a transparent top electrode over the body, usually S
nO ₂, ITO (In₂O₃+ SnO₂Anti-reflective like
A transparent conductive film that also functions as a film is provided. Photovoltaic element
The semiconductor between the bottom and top electrodes of the
And the lower and upper electrodes made direct contact.
Board spike-like defects may come into contact with the upper electrode,
A shunt with low resistance, even if the conductor layer is not completely lost.
Is caused by light when it is short
Current flows in parallel through the upper electrode and the shunt or short
The current will flow into the low resistance part of the
The flow is lost. Even small defects flow to the defects.
The current flowing in is quite large. Such current
If there is a loss, the open circuit voltage of the photovoltaic element will drop and
If the light intensity is low, the current generated by the light and
The magnitude of the leakage current due to the shunt does not change much
Therefore, the open circuit voltage is significantly reduced. further,
If the position of the defect is far from the grid electrode or bus bar
In this case, the resistance when flowing into the defective part is large, so
The flow loss is relatively small, but the defective parts are
If it is below the bar, the current lost due to the defect is
It will be bigger.

On the other hand, at the pinhole-shaped defect portion, not only the charge generated in the semiconductor layer leaks to the defect portion, but also an ionic substance is generated in the pinhole due to the interaction with moisture, and When using the electromotive force module,
There is a phenomenon in which the electric resistance of the defective portion gradually decreases with the lapse of use time, and characteristics such as conversion efficiency deteriorate.

As measures against such a problem, a method of selectively filling the shunt portion with a resin, a method of depositing a metal on the shunt portion and then insulating the metal by an anodic oxidation method, and the like have been proposed.

For example, as disclosed in US Pat. No. 4,451,970, there is a method of detecting a defective portion of an element with a detector and then applying an insulator to the detected defective portion with an applicator. Further, the method disclosed in Japanese Patent Publication No. 62-40871 is a method of coating a photoresist and filling the pinhole, and then performing the steps of exposure, development, rinsing and baking to close the pinhole.

[0011]

However, in the invention disclosed in US Pat. No. 4,451,970,
First, it is necessary to detect defects and selectively attach resin, which complicates the process and makes the device large. Further, in the invention disclosed in Japanese Patent Publication No. 62-40871, not only the process of exposing and developing after applying a photoresist becomes complicated, but also it can be used only for a photovoltaic device of a thin film deposited on a transparent substrate. There wasn't. Further, neither of these methods has a problem in that it cannot deal with defects that occur after the existing shunt is closed.

Therefore, the present inventor seals a defect existing under the electrode, which causes a large decrease in conversion efficiency. Therefore, when there is a defect between the electrode and the semiconductor layer, the inventor works as a resistor. A study was made to provide an electrode layer for short-circuit current sealing, which does not become a resistance against the current generated by the photovoltaic element.

However, at the interface between the electrode layer and the semiconductor layer, since the porosity of the electrode layer is large and the adhesion is poor,
It has been discovered that the resistance between the electrode and the semiconductor layer increases, which hinders current collection and reduces efficiency. Further, they have found that peeling occurs, and a leak current gradually occurs to lower reliability.

An object of the present invention is to solve the above-mentioned problems in a photovoltaic device and the above-mentioned problems caused in the process of the present invention, and to provide a structure of a photovoltaic device having good characteristics.

Another object of the present invention is to provide a method for manufacturing a photovoltaic device which has good mass productivity and high reliability.

[0016]

In the photovoltaic device of the present invention, a photovoltaic device is formed by forming at least a semiconductor layer, a high resistance electrode layer for preventing a short circuit current, and a low resistance electrode on a substrate. In the element, an insulating layer is provided between the semiconductor and the electrode layer, and the electrode layer and the semiconductor layer are electrically connected through the insulating layer.

The insulating layer is preferably a polymer resin selected from polyester, ethylene-vinyl acetate copolymer, acrylic, epoxy, and polyurethane, and has a transmittance of sunlight of 50% or more. It is preferable.

Further, the electrode layer is preferably formed by using a conductive paste, and the conductive paste is In ₂ O ₃ , SnO ₂ , ZnO, CdO, CdSnO ₄ ,
ITO (In ₂ O ₃ + SnO ₂ ) and at least one of conductive fillers made of carbon and polyester,
It is preferable to include at least one of polymer resin binders composed of epoxy and polyurethane.

Further, the porosity of the electrode layer is preferably 5% or less.

Further, the method for producing a photovoltaic element of the present invention is
In a method for manufacturing a photovoltaic device, which comprises at least a semiconductor layer, an insulating layer, and an electrode layer formed on a substrate, an insulating layer made of a polymer resin is formed after the semiconductor layer is formed, and a polymer resin binder is further added. It is characterized in that the electrode layer is formed using a conductive paste containing the same.

The insulating layer is formed by a method selected from electrodeposition, electrolytic polymerization, plasma polymerization, spin coating, roll coating and dipping.

Further, it is preferable that the conductive paste contains a component capable of dissolving the polymer resin, and dissolves a part of the insulating layer when the electrode layer is formed.

[0023]

According to the present invention, an electrode layer is provided between the upper electrode of the semiconductor layer and the grid electrode, and the upper electrode is provided as a structure of a photovoltaic element in which defects are sealed and which has high characteristics and reliability. An insulating layer is provided between the electrode layer and the electrode layer.

In explaining the operation of the present invention, the knowledge obtained in the process of completing the present invention will be described first.

In order to prevent a short-circuit current to the defective portion, it is sufficient to cover the defective portion with an insulating material, but rather than detecting and closing the defective portion, an electrode layer is provided between the grid electrode and the upper electrode, and It is easier not to act as a resistance against the current generated by the electromotive force element, but to act as a resistance when there is a defect, and it is possible to cope with a shunt that occurs later. However, when only this electrode layer is laminated between the grid electrode and the upper electrode, the porosity becomes high, the resistance between the grid electrode and the upper electrode becomes very large, and the current is lost or the air gap is reduced. Since there are a large number of defects, peeling and leakage current occur, which causes problems such as low reliability.

Based on these findings, by providing an insulating layer between the electrode layer and the upper electrode, the porosity of the electrode layer can be reduced, and a photovoltaic element with extremely excellent characteristics and reliability and high yield can be obtained. The present invention enables the manufacturing method.

In the photovoltaic device of the present invention, the solvent contained in the paste or the monomer of the polymer resin binder partially dissolves the insulating layer laminated on the upper electrode when the conductive paste serving as the electrode layer is applied. However, it is characteristic that the porosity of the formed electrode layer can be reduced and the conductive filler can come into contact with the upper electrode to make good electrical contact.

Therefore, it is necessary to select a conductive paste material according to the physical properties of the insulating layer. That is, even if an electrode layer is laminated on the insulating layer, the ohmic contact between the electrode layer and the upper electrode is not sufficient, and a sufficient current cannot flow through the grid electrode. However, the solvent or unreacted components of the polymer resin binder contained in the conductive paste dissolves the insulating layer,
When the conductive filler contacts the upper electrode, the electrode layer and the upper electrode come into sufficient electrical contact.
In this case, the contact between the defective part and the conductive filler may occur at the same time, but since the binder and the electrode layer that cannot be completely dissolved by the solvent cover the defective part, it is more appropriate than when directly laminating the grid electrode. Resistance, and the degree of short circuit is reduced. Further, as compared with the case where the electrode layer is directly laminated on the upper electrode, the porosity of the electrode layer is reduced and the adhesion is improved.

Further, by laminating the grid electrode on the electrode layer in close contact, the resistance of the wiring can be reduced. Further, not only the electrode layer but also the insulating layer covers and insulates the defective portion of the semiconductor layer that causes the shunt or short circuit, so that the short circuit can be suppressed.

The contents of the present invention will be described in detail with reference to FIG. The present invention is not limited to FIG. Figure 1
, 100 is a photovoltaic element body, 101 is a substrate,
102 is a lower electrode, 103 is an n layer, 104 is an i layer, 10
5 is a p-layer, 106 is an upper electrode, 107 is an insulating layer, 108
Is an electrode layer, 109 is a grid electrode, and 111 is a defective portion.

The defective portion 111 is a low resistance portion caused by unevenness of the substrate or dust during film formation. Further, it also indicates a portion where the resistance is lowered during use even though the portion is normal in the initial stage of manufacture.

The insulating layer 107 used in the present invention is an electrode layer 108 made of a conductive paste for sealing a short circuit current.
Has the role of lowering the porosity of the electrode layer 108 when forming. Since the insulating layer 107 is laminated on the surface of the photovoltaic element on which sunlight is incident, the transmittance for sunlight is preferably 90% or more so as not to prevent the incidence of sunlight. It is also insulative to seal defects. Also, considering the environment when used outdoors as a photovoltaic module, it is required to have good weather resistance and stability against heat, humidity and light. Also, in some cases, the photovoltaic module may be bent or impacted,
It is necessary to have mechanical strength as well. A polymer resin is suitable as such a material, and specifically, polyester, ethylene vinyl acetate copolymer, acrylic resin, epoxy resin, urethane or the like is used. A number average molecular weight of the polymer resin is preferably about 1 to 20,000. The film thickness is preferably selected according to the type of polymer resin because it is preferable that the electrical insulation is maintained and the light transmittance is not impaired, but typically several μm.
The place is appropriate.

As a method for laminating such a polymer resin, an ordinary method is used, for example, a method of dissolving in a solvent and performing spin coating or dipping, a method of melting by heat and coating with a roller, and an electrolytic polymerization. A method of depositing, a method of depositing by electrodeposition, a method by plasma polymerization, etc. are used and appropriately determined from various conditions such as physical properties of the polymer resin and a desired film thickness, but from the viewpoint of mass productivity, a dipping method, a roller A coating method, an electrodeposition method and the like are suitable.

The thickness of the insulating layer 107 is determined by requirements such as no pinholes, sufficient barrier properties against humidity, adhesion and flexibility, but if the thickness is 1 μm or less, it easily becomes pinholes, and if it is 30 μm or more, it is flexible. Since the property is impaired, the thickness is preferably about 1 to 30 μm.

The electrode layer 108 used in the present invention serves as a pattern for forming the grid electrode 109. Examples of the material include a conductive paste, a binder made of a polymer, and a conductive paste which is made into a paste by mixing a solvent that dissolves the binder in an appropriate ratio.

This conductive paste is composed of In ₂ O ₃ and Sn.
O ₂ , ZnO, CdO, CdSnO ₄ , ITO (In ₂ O ₃
+ SnO ₂ ), containing at least one conductive filler of carbon, and preferably containing at least one polymer resin binder of polyester, epoxy or polyurethane. Further, the component that dissolves the polymer resin (insulating layer) contained in the conductive paste is at least one of ethyl acetate, methyl ethyl ketone, and toluene, or is an unreacted component of the polymer resin binder. desirable. The preferable resistance value of the electrode layer 108 is determined by the grid design, the current value at the operating point of the photovoltaic element, the size of the defect, etc.
When 0 μm, the specific resistance is 0.1 Ωcm to 100 Ωc
m is preferable, and in this range, the resistance is sufficient for the shunt, and the resistance value is negligible for the current generated in the photovoltaic element.

The lamination of these electrode layers can be produced with good productivity by using the screen printing method. In the screen printing method, a conductive paste is used as a printing ink by using a screen in which a mesh made of nylon or stainless steel is subjected to desired patterning, and the line width can be about 50 μm at the minimum. The screen-printed conductive paste is heated in a drying oven to crosslink the binder and volatilize the solvent.

When the pattern formation of the electrode layer 108 is performed by screen printing, the conductive paste has a viscosity of 100.
It is desirable that it is about 0 cps to 100,000 cps. In addition, when the photovoltaic module is used outdoors, it is necessary to have weather resistance that can withstand humidity and temperature.

The form of the electrode layer 108 is the grid electrode 109.
It is formed in the same pattern as the pattern of
In order to facilitate alignment when stacking the grid electrode 109 and to prevent migration due to the influence of humidity of the metal used for the grid electrode 109, it is preferable to form the electrode slightly wider than the grid electrode 109, and it is 1 to 5 times larger. It is preferable that In this case, it is preferable that the photovoltaic element is transparent to a wavelength having spectral sensitivity so as to prevent shadow loss due to the electrode layer 108 other than the grid electrode 109.

In the photovoltaic element of the present invention, an electrode layer having a relatively high resistance is formed under the grid electrode, and an insulating layer is provided between the electrode layer of this high resistance pile and the semiconductor layer to form the electrode layer. By reducing the porosity, current leakage due to shunts and short circuits is reduced, and the resistance between the grid electrode and the upper electrode is improved by reducing the resistance.
Although it can be suitably applied to an amorphous silicon photovoltaic element, a similar configuration is applicable to a photovoltaic element using a single crystal, a polycrystalline system or a semiconductor other than silicon, a Schottky junction type photovoltaic element, etc. It goes without saying that it is also applicable.

Examples of embodiments of the photovoltaic element of the present invention will be described below with reference to FIGS. 1 to 3, but the contents of the present invention are not limited to these.

A suitable configuration example of the photovoltaic element of the present invention is schematically shown in the drawing. FIG. 1 is a cross-sectional view of an amorphous silicon photovoltaic element having a single cell structure in which light is incident from the side opposite to the substrate, and FIG. 2 is a plan view of the photovoltaic element having the configuration of FIG. 3 grids 10 cm long
The rows are formed and a bus bar is provided at the center of each row. FIG. 3 is a cross-sectional view of a triple cell configuration.

Further, although not shown, the idea of the present invention is applied to an amorphous silicon photovoltaic element deposited on a glass substrate, a crystalline photovoltaic element such as a single crystal or a polycrystal, and a thin film polycrystalline photovoltaic element. It goes without saying that the configuration that has been used is applicable.

The substrate 101 is like amorphous silicon
Layer 103, 10 in case of thin film photovoltaic device
4, 105 is a member that mechanically supports the
Therefore, it is used as an electrode. Substrate 101 is a semiconductor
To the heating temperature when forming the layers 103, 104, 105
Electrical resistance is required even if it is conductive, although it must withstand heat
It can be sex. As the conductive material, specifically,
Fe, Ni, Cr, Al, Mo, Au, Nb, Ta,
Metals such as V, Ti, Pt, Pb, and Ti, or their combination
Gold, for example brass, stainless steel, etc.
Coalesce, carbon sheet, galvanized steel sheet, etc.
Polyester and polyethylene are used as electrically insulating materials.
Resin, polycarbonate, cellulose acetate, polyp
Ropylene, polyvinyl chloride, polyvinylidene chloride, poly
Heat resistance of styrene, polyamide, polyimide, epoxy, etc.
Synthetic resin film or sheet or glass with these
Fiber, carbon fiber, boron fiber,
Composites with metal fibers, thin plates of these metals, resins
Metal thin film and / or Si made of different materials on the surface of sheet etc.
O ₂, Si₃N_Four, Al₂O₃, Insulating thin film such as AlN
Surface coating process by the putter method, vapor deposition method, plating method, etc.
And the glass, ceramics, etc.
You can

The lower electrode 102 is composed of the semiconductor layers 103 and 10
It is one electrode for taking out the electric power generated at 4, 105, and is required to have a work function for forming an ohmic contact with the semiconductor 103. As the material, Al, Ag, Pt, Au, Ni, Ti, Mo,
W, Fe, V, Cr, Cu, stainless steel, brass, nichrome, SnO ₂ , In ₂ O ₃ , ZnO, so-called metal simple substance or alloy such as ITO, and transparent conductive oxide (TC)
O) or the like is used. Although the surface of the lower electrode 102 is preferably smooth, it may be textured if it causes irregular reflection of light. Further, when the substrate 101 is conductive, the lower electrode 102 need not be provided.

As a method of manufacturing the lower electrode, a method such as plating, vapor deposition, sputtering or the like is used. As a method for manufacturing the upper electrode, a resistance heating vapor deposition method, an electron beam heating vapor deposition method, a sputtering method, a spray method, or the like can be used, and is appropriately selected as desired.

As the semiconductor layer of the photovoltaic element used in the present invention, amorphous silicon, polycrystalline silicon,
Single crystal silicon and the like can be mentioned. As the semiconductor material forming the i layer 104 in the amorphous silicon photovoltaic element, a-Si: H, a-Si: F, a-Si:
H: F, a-SiGe: H, a-SiGe: F, a-S
iGe: H: F, a-SiC: H, a-SiC: F, a
Examples include so-called group IV and group IV alloy-based amorphous semiconductors such as -SiC: H: F. The semiconductor material forming the p-layer 105 or the n-layer 103 can be obtained by doping the above-mentioned semiconductor material forming the i-layer 104 with a valence electron control agent. Also, as a raw material,
A compound containing an element of Group III of the periodic table is used as a valence electron control agent for obtaining a p-type semiconductor. No. III
Examples of the group element include B, Al, Ga, and In. As the valence electron control agent for obtaining the n-type semiconductor, a compound containing an element of the periodic table V is used. Examples of the Group V element include P, N, As, and Sb.

As the film forming method of the amorphous silicon semiconductor layer, vapor deposition method, sputtering method, RF plasma CVD method,
Microwave plasma CVD method, ECR method, thermal CVD method,
A known method such as the LPCVD method is used as desired. As an industrially adopted method, RF plasma CV in which a raw material gas is decomposed by RF plasma and deposited on a substrate
Method D is preferably used. Furthermore, RF plasma CVD
The decomposition efficiency of the source gas is as low as about 10%, and the deposition rate is from 0.1 nm / sec to 1 nm / sec.
The microwave plasma CVD method has been attracting attention as a film forming method that improves this point, although it has a problem of being relatively slow.
As a reaction apparatus for performing the above film formation, a known apparatus such as a batch type apparatus or a continuous film forming apparatus can be used as desired. The photovoltaic element of the present invention can also be used in a so-called tandem cell in which two or more semiconductor junctions are stacked for the purpose of improving spectral sensitivity and voltage.

The upper electrode 106 is composed of the semiconductor layers 103 and 10
Electrodes for extracting the electromotive force generated at 4, 105, which form a pair with the lower electrode 102. The upper electrode 106 is necessary in the case of a semiconductor having a high sheet resistance such as amorphous silicon, and is not particularly necessary in a crystalline photovoltaic element since it has a low sheet resistance. Further, since the upper electrode 106 is located on the light incident side, it needs to be transparent and is also called a transparent electrode. Upper electrode 106
Has a light transmittance of 85% or more in order to efficiently absorb light from the sun or a white fluorescent lamp into the semiconductor layer. Furthermore, electrically, a current generated by light is applied to the semiconductor layer. On the other hand, it is desirable that the sheet resistance value is 100Ω / □ or less so that the sheet flows in the lateral direction. As materials having such characteristics, SnO ₂ , In ₂ O ₃ , Zn
O, CdO, CdSnO ₄ , ITO (In ₂ O ₃ + Sn
Metal oxides such as O ₂ ) may be mentioned.

Next, the grid electrode 109 is the semiconductor layer 10
It is an electrode for taking out the electromotive force generated at 3, 104 and 105. The grid electrode 109 is formed on a comb, and a suitable width and pitch are determined from the magnitude of the sheet resistance of the semiconductor layer 105 or the upper electrode 106. The grid electrode 109 is required to have a low specific resistance and not become a series resistance of the photovoltaic element, and a desired specific resistance is 10 ^-2 Ω.
cm to 10 ⁻⁶ Ωcm, and the materials are Ti and C
Metals such as r, Mo, W, Al, Ag, Ni, Cu, Sn and Pt, or alloys or solders thereof are used.

Since the grid electrode 109 is comb-shaped, a sputtering method, a resistance heating method, a CVD method or the like using a mask pattern of a desired shape is used as a forming method. Alternatively, a method of depositing a metal layer on the entire surface and then patterning by etching, a method of directly forming a grid electrode pattern by photo CVD, a method of forming a negative pattern mask of the grid electrode and then forming by a plating method, and a conductive paste are used. There is a method of forming by screen printing.

Bus bar 110 used in the present invention
Is an electrode for further collecting the current flowing through the grid electrode 109 at one end. Ag, Pt, C as electrode materials
It is possible to use a metal such as u or an alloy thereof, and as a form, a wire-shaped or foil-shaped one may be attached, or a conductive paste similar to the grid electrode 109 may be used. The foil-shaped material is, for example, a copper foil, or a copper foil plated with tin, and in some cases, a material with an adhesive is used.

As a method of forming the bus bar 110, a metal wire may be fixed with a conductive adhesive, a copper foil may be attached, or the bus bar 110 may be formed similarly to the grid electrode 109.

The photovoltaic module produced as described above is modularized by encapsulation by a known method in order to improve weather resistance and maintain mechanical strength when used outdoors. As a specific encapsulation material, EVA (ethylene vinyl acetate) is preferably used for the adhesive layer in terms of adhesiveness to the photovoltaic element, weather resistance, and buffering effect. Further, in order to further improve the moisture resistance and the scratch resistance, a fluorine resin is laminated as the surface protective layer. Examples of the fluorine-based resin include a polymer TFE of tetrafluoroethylene (such as Teflon manufactured by DuPont) and a copolymer ETF of ethylene tetrafluoride and ethylene.
Examples thereof include E (Tefzel manufactured by DuPont), polyvinyl fluoride (Tedlar manufactured by DuPont), and polychlorofluoroethylene CTFE (Neotron manufactured by Daikin Industries). Further, weather resistance may be improved by adding a known ultraviolet absorber to these resins.

As a method of encapsulation,
Using a known device such as a vacuum laminator,
A method in which the photovoltaic element substrate and the resin film are heated and pressed in vacuum is desirable.

[0056]

EXAMPLES The structure of the photovoltaic element of the present invention and the method for producing the photovoltaic element of the present invention will be described in groups based on examples, but the present invention is not limited to these examples. .

(Example 1) A photovoltaic element 100A having a pin junction type single cell structure with a bus bar having a grid length of 10 cm and having the layer structure shown in FIG. 1 was manufactured as follows.

First, SUS4 that has been thoroughly degreased and washed
30BA substrate (width 30 cm x length 30 cm, thickness 0.
2mm) 101 is put in a DC sputtering device and Ag is set to 400
nm, and then ZnO was deposited to 400 nm to form the lower electrode 102. The substrate 101 is taken out and placed in an RF plasma CVD film forming apparatus, and the n layer 103, i layer 104,
Deposition was performed in order of the p layer 105. Then, it is put in a resistance heating vapor deposition apparatus and 1 × 10 ⁻⁴ Tor is introduced while introducing oxygen.
A transparent ITO upper electrode 1 which also functions as an anti-reflection effect by keeping an internal pressure of r and depositing an alloy of In and Sn by resistance heating.
06 was deposited to 70 nm.

Next, the substrate 101 was placed in a dipping device and coated with an insulating layer 107 made of butyral resin. The thickness of the coated butyral resin was 3 μm. Next, set the temperature of the hot air oven to 150
The temperature was kept at 0 ° C., the substrate 101 was charged, and the butyral resin was cured.

After that, the substrate 101 was taken out from the oven and cooled, and then the substrate 101 was set in a screen printing machine.
The electrode layer 108 having a width of 300 μm and a length of 10 cm is separated by 5 m.
3 rows were printed with m. At this time, the conductive paste is ITO
A composition containing 80% by weight of powder, 20% by weight of an epoxy binder, and 10% by weight of butyl cellulose acetate as a solvent was used.

Next, the temperature of the hot air oven was maintained at 180 ° C., the substrate 101 was charged, and the ITO paste was cured. After that, the substrate 101 is taken out of the oven and cooled, and then the substrate 101 is installed in a screen printing machine and a width of 20
The grid electrodes 109 having a length of 0 μm and a length of 10 cm are spaced by 1 cm.
Printed in. Ag paste was used as the electrode material.
After printing, the substrate 101 was placed in the oven and held at 160 ° C. for 30 minutes to cure the conductive paste. In addition,
The thicknesses of the electrode layer 108 and the grid electrode 109 are both
It was 10 μm.

Further, a bus bar 110 of copper foil with an adhesive having a width of 5 mm was adhered to produce a single cell of 30 cm × 30 cm square shown in FIG. In FIG. 2, 101 is a substrate, 102 to 106 are lower electrodes, semiconductor layers, upper electrodes,
109 is a grid and 110 is a bus bar. further,
Twenty samples were prepared by the same method.

Next, encapsulation of these samples was carried out as follows. EVA is laminated on the upper and lower sides of the substrate 101, and the fluororesin film ETFE is formed on the upper and lower sides of the EVA.
After stacking (ethylene tetrafluoroethylene) (product name Tefzel manufactured by DuPont), it was put into a vacuum laminator and held at 150 ° C. for 60 minutes to perform vacuum lamination.

The initial characteristics of the obtained sample were measured as follows.

First, the voltage-current characteristics of the sample in the dark state were measured, and the shunt resistance was obtained from the inclination near the origin. The shunt resistance was 160 KΩcm ^{2 to} 230 KΩcm ² , and the variation was small. The average series resistance was 31.2 Ωcm ² .

Next, the photovoltaic module characteristics were measured using a pseudo solar light source (hereinafter referred to as a simulator) having a light amount of 100 mW / cm ² in AM1.5 global sunlight spectrum, and conversion efficiency was obtained. 5.5% ± 0.
The characteristic was as good as 3% and there was little variation.

A reliability test was conducted on 10 of the above samples based on the temperature / humidity cycle test A-2 defined in the environmental test method and durability test method of the crystalline photovoltaic module of Japanese Industrial Standard C8917. went. First, the sample was placed in a thermo-hygrostat capable of controlling temperature and humidity, and a cycle test for changing from -40 ° C to + 85 ° C (relative humidity 85%) was repeated 10 times.

Next, the characteristics of the photovoltaic module of the sample after the test were measured by using a simulator in the same manner as the measurement of the initial characteristics. As a result, the average conversion efficiency was reduced by 4%, showing no significant deterioration. Did not happen. When the shunt resistance was measured, there was no significant deterioration with an average decrease of about 10%.

Next, when the cross section of the sample including the grid was observed with a scanning electron microscope, it was observed that the cross section of the electrode layer was uniform, and the porosity was measured to be 2-4.
%Met.

A reliability test was conducted on the remaining 10 sheets as follows. Put the sample in the constant temperature and humidity chamber and add +85
The temperature was kept at 85 ° C and the relative humidity was 85%. A forward bias voltage of +0.3 V was applied to the sample for 20 hours in this tester, and the leak current flowing during that time was measured. FIG. 4 shows an example of the change over time of the leak current. The leak current after application of the bias voltage for 20 hours was 7.2 mA on average, and almost no leak occurred.

From the results of this example, it is understood that the photovoltaic element of the present invention using the constitution of the present invention has good yield, good characteristics, and high reliability.

Comparative Example 1 Next, for comparison, a photovoltaic element 300 having a conventional structure shown in FIG. 6 was manufactured as follows.

Similar to Example 1, the upper electrode 306 was formed on the substrate 301. Next, the grid electrode 309 was printed in the same manner as in Example 1. Further, a bus bar 310 of copper foil with an adhesive is laminated, and 30 cm × 30 shown in FIG.
20 cm square single cells were prepared.

Next, the encapsulation of this sample was performed in the same manner as in Example 1.

When the initial characteristics of the obtained sample were measured by the same procedure as in Example 1, the conversion efficiency was 4.3% ± 1.5.
%, The shunt resistance is 0.3 KΩcm ² to 60 KΩcm ²
As compared with Example 1, the shunt resistance was low and varied, so the conversion efficiency was low and the variation was large. The series resistance was 27.8 Ωcm ² on average and there was no significant difference from Example 1.

Then, a reliability test was performed on 10 of the samples in the same manner as in Example 1. When the photovoltaic module characteristic measurement of the sample after the temperature / humidity cycle test was completed, it showed a 25% decrease on average from the initial value, and significant deterioration had occurred.

Further, when the shunt resistance was measured, it was found that the average was decreased by 85%, and it was found that the shunt was generated after the reliability test.

Next, the leak current was measured for the remaining 10 samples in the same manner as in Example 1. FIG. 4 shows an example of changes over time in the leakage current. The leak current when a bias voltage was applied for 20 hours was 120 mA on average, and it was found that a shunt occurred and a large leak current was flowing.

The shunt portion of this sample was confirmed as follows. First, a reverse bias of 1.5 V was applied to the sample. At this time, current flows through the shunt portion to generate heat, but the normal portion does not generate heat due to the reverse bias because no current flows. When the surface of the sample was observed with an infrared camera in this state, a heat generating portion was observed and it was found that the sample electrode was shunted under the grid electrode 309.

From the above-described Example 1 and Comparative Example 1, it was found that the photovoltaic element of the present invention had defects sealed therein, good initial efficiency, and good reliability.

Comparative Example 2 Next, for comparison, the photovoltaic element 1 of FIG. 5 having the same structure as that of Example 1 and having no insulating layer.
00D was produced as follows.

Similar to Example 1, the upper electrode 106 was formed on the substrate 101. Next, the electrode layer 108 of the conductive paste and then the grid electrode 109 were printed in the same manner as in Example 1. Further, a bus bar 110 of copper foil with an adhesive was laminated to manufacture 20 single cells of 30 cm × 30 cm square shown in FIG. 7.

Next, encapsulation of this sample was performed in the same manner as in Example 1.

When the initial characteristics of the obtained sample were measured by the same procedure as in Example 1, the conversion efficiency was 5.0% ± 1.2.
%, The shunt resistance was 15 KΩcm ² to 75 KΩcm ² , and the shunt resistance was low compared to Example 1, and therefore the conversion efficiency was low and the variation was large. The series resistance is 45.3 Ωcm ² on average, and it is considered that the current loss is higher than that of the example.

Next, the reliability test of this sample was evaluated in the same manner as in Example 1. When the photovoltaic module characteristics of the sample after the completion of the temperature / humidity cycle test were measured, it showed an average decrease of 19% with respect to the initial value, and significant deterioration occurred.

Further, when the shunt resistance was measured, it was found that the average shunt resistance decreased by 20%, and it was found that the shunt occurred after the reliability test.

Next, the leak current was measured in the same manner as in Example 1. The average leak current when applying the bias voltage for 20 hours was 34 mA, which was smaller than that in Comparative Example 1, but it was found that a shunt was generated.

When the shunt portion of this sample was confirmed in the same manner as in Comparative Example 1, it was found that the shunt portion was under the grid electrode 109 as well. Next, when the cross section was observed with an electron microscope in the same manner as in Example 1, holes having a diameter of about 1 to 3 μm were observed in the electrode layer, and the porosity was measured to be 10 to 15%.

From the above Example 1 and Comparative Examples 1 and 2,
In the photovoltaic element of the present invention, stacking an electrode layer between the upper electrode and the grid electrode is effective in preventing a short circuit current, and further, this electrode layer has an insulating layer stacked between the upper electrode and the upper electrode. As a result, it was found that the initial efficiency was good and the reliability was also good because the voids became low and they adhered to the upper electrode.

(Example 2) Next, a photovoltaic element having the same structure as that of Example 1 but different in the method of laminating the polymer resin to serve as the insulating layer was prepared in substantially the same manner as in Example 1.

First, as in Example 1, the layers up to the upper electrode 106 were laminated. Next, the substrate 101 was placed in the electrodeposition apparatus and an electrodeposition film was formed using an acrylic anion electrodeposition coating material.
The substrate 101 is taken out, excess paint is washed with water, and then the electrodeposition film is dried in a hot air oven kept at 80 ° C. for 10 minutes,
Next, the electrodeposition film was cured for 30 minutes in a hot air oven maintained at 180 ° C.

Next, in the same manner as in Example 1, the electrode layer 108,
Then, the grid electrode 109 was printed, and then encapsulation was performed in the same manner as in Example 1. Further, 10 samples were prepared by the same method.

When the initial characteristics of the obtained sample were measured by the same method as in Example 1, the conversion efficiency was 5.8 ± 0.4%, and the shunt resistance was 140 KΩcm ² to 180 KΩ.
It was cm ² and had good characteristics and small variations.

Next, the reliability of this sample was evaluated in the same manner as in Example 1. The conversion efficiency was 5% lower than the initial value, and no significant deterioration was observed. The shunt resistance was reduced by 8% on average, and no significant deterioration was observed. Further, in the cross-section observation, the electrode layer was uniform and the porosity was 2% to 3%.

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

(Example 3) Next, in Example 1, the solar cell is substantially the same as in Example 1 except that the triple solar cell of FIG. 3 is used and the microwave plasma CVD method is used for forming the semiconductor layer. A solar cell was manufactured by the following method.

First, a lower electrode 102 composed of an Ag layer and a ZnO layer is formed on a substrate 101, and then placed in a microwave plasma CVD film forming apparatus to deposit an n layer 103 and an i layer 10.
4 and p layer 105 were deposited in this order to form a bottom layer.
At this time, the i layer 104 was a-SiGe. Next, n layer 11
3, the i layer 114 and the p layer 115 were deposited in this order to form a middle layer. The i layer 114 is made of a-SiG as in the bottom layer.
e. Next, the n layer 123, the i layer 124, and the p layer 125 were deposited in this order to form a top layer. The i layer 124 is a-
It was set to Si. Next, as in Example 2, a transparent upper electrode 106 having a reflection preventing effect was deposited to a thickness of 70 nm. In ₂ O ₃ (IO) was used as the upper electrode 106.

Next, the substrate 101 is placed in a dipping device, and the insulating layer 1 made of butyral resin is used as in Example 1.
After coating 07, it was cured as in Example 1.

Further, the electrode layer 108, the grid electrode, and the bus bar 110 are laminated in the same manner as in Example 1, and 30 shown in FIG.
A cm square triple cell was prepared. Similarly, ten samples were prepared.

Further, the encapsulation of this sample was performed in the same manner as in Example 1.

The initial characteristics of the obtained sample are 7.8% ±
0.4% and the shunt resistance is 120 KΩcm ² to 15
It was 0 KΩcm ² and had good characteristics with little variation.

When the reliability test of these samples was measured in the same manner as in Example 1, the average conversion efficiency was 2% lower than the initial conversion efficiency, and no significant deterioration occurred. Also,
When the shunt resistance was measured, there was no significant deterioration with an average reduction of about 6%.

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

[0104]

According to the photovoltaic element of the present invention, that is, a photovoltaic element in which at least a semiconductor layer, a high resistance electrode layer for preventing a short circuit current, and a low resistance electrode are formed on a substrate. In, by providing an insulating layer between the semiconductor and the electrode layer, defects can be sealed and the porosity of the electrode layer can be reduced, the initial characteristics are high, and the photovoltaic element has excellent durability. Can be provided.

According to the method for producing a photovoltaic element of the present invention, that is, in the method for producing a photovoltaic element in which at least a semiconductor layer, an insulating layer, and an electrode layer are formed on a substrate, a semiconductor layer is formed. After that, an insulating layer made of a polymer resin is formed, and then an electrode layer is formed by using a conductive paste containing a polymer resin binder, whereby an electrode layer with a low porosity is formed, good initial characteristics, and reliable. A photovoltaic element having excellent properties can be manufactured with a high yield.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing the structure of a photovoltaic element of the present invention.

FIG. 2 is a plan view schematically showing the structure of the photovoltaic element of the present invention.

FIG. 3 is a sectional view schematically showing the structure of a triple photovoltaic element of the present invention.

FIG. 4 is a graph showing changes in leak current with time in Example 1 and Comparative Examples 1 and 2.

FIG. 5 is a cross-sectional view schematically showing the structure of a photovoltaic element of Comparative Example 2.

FIG. 6 is a cross-sectional view that schematically shows the configuration of the photovoltaic element of Comparative Example 1.

FIG. 7 is a plan view schematically showing the configuration of a photovoltaic element of Comparative Example 1.

[Explanation of symbols]

 100, 300 Photovoltaic device body 101, 301 Substrate 102, 302 Lower electrode 103, 113, 123, 303 n layer 104, 114, 124, 304 i layer 105, 115, 125, 305 p layer 106, 306 upper electrode 107 Insulating layer 108 Electrode layer 109, 309 Grid electrode 110, 210 Bus bar 111, 311 Defect part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Hasebe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (18)

[Claims] 1. A photovoltaic element comprising at least a semiconductor layer, a high resistance electrode layer for preventing a short circuit current, and a low resistance electrode formed on a substrate, wherein the semiconductor layer and the electrode layer are between the semiconductor layer and the electrode layer. A photovoltaic element, wherein an insulating layer is provided on the substrate, and the electrode layer and the semiconductor layer are electrically connected through the insulating layer. 2. The specific resistance of the electrode layer is 0.1 to 100.
It is 0 ohm-cm, The photovoltaic element of Claim 1 characterized by the above-mentioned. 3. The photovoltaic element according to claim 1, wherein the photovoltaic element is made of a thin film semiconductor. 4. The electrode according to claim 1, wherein the electrode is a collector electrode or a take-out electrode.
The photovoltaic element according to the item. 5. The sunlight transmittance of the insulating layer is
It is 50% or more, The photovoltaic element according to any one of claims 1 to 4. 6. The photovoltaic element according to claim 1, wherein the insulating layer is made of polymer resin. 7. The photovoltaic element according to claim 6, wherein the polymer resin comprises a component selected from polyester, ethylene vinyl acetate copolymer, acrylic, epoxy, and polyurethane. . 8. The electrode layer according to claim 1, which is formed by using a conductive paste.
The photovoltaic element according to the item. 9. The conductive paste is In ₂ O ₃ , Sn.
O ₂ , ZnO, CdO, CdSnO ₄ , ITO (In ₂ O ₃
9. The photovoltaic element according to claim 8, comprising at least one of + SnO ₂ ) and a conductive filler made of carbon. 10. The photovoltaic device according to claim 8, wherein the conductive paste contains at least one of polymer resin binders made of polyester, epoxy and polyurethane. 11. The photovoltaic element according to claim 1, wherein the porosity of the electrode layer is 5% or less. 12. A method of manufacturing a photovoltaic element comprising a substrate, on which at least a semiconductor layer, an insulating layer, and an electrode layer are formed, wherein an insulating layer made of a polymer resin is formed after the semiconductor layer is formed. A method for manufacturing a photovoltaic element, comprising forming an electrode layer using a conductive paste containing a polymer resin binder. 13. The insulating layer comprises an electrodeposition method, an electrolytic polymerization method,
The method for producing a photovoltaic element according to claim 12, wherein the photovoltaic element is formed by a method selected from a plasma polymerization method, a spin coating method, a roll coating method, and a dipping method. 14. The method according to claim 12, wherein a part of the insulating layer is melted when the electrode layer is formed.
4. The method for manufacturing the photovoltaic element according to item 3. 15. The method for manufacturing a photovoltaic element according to claim 14, wherein the conductive paste contains a component that dissolves the polymer resin and dissolves a part of the insulating layer. 16. The method for producing a photovoltaic element according to claim 15, wherein the component that dissolves the polymer resin is at least one of methyl acetate, methyl ethyl ketone, and toluene. 17. The photovoltaic device according to claim 12, wherein the polymer resin binder contains at least one of polyester, epoxy, and polyurethane. Method. 18. The method for manufacturing a photovoltaic element according to claim 12, wherein the polymer resin binder contains an unreacted component.