JP3078936B2 - Solar cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell. More specifically, the present invention relates to improvement of a surface coating material of a solar cell, and relates to a solar cell having high initial characteristics and high reliability.

[0002]

2. Description of the Related Art Solar cells, which are photoelectric conversion elements for converting sunlight into electric energy, are widely used as power supplies for consumer appliances such as calculators and watches, and are used as substitutes for so-called fossil fuels such as oil and coal. It is attracting attention as a technology that can be practically used as power for electricity.

[0003] A solar cell is a technique utilizing a diffusion potential generated at a pn junction of a semiconductor. A semiconductor such as silicon absorbs sunlight, and generates photo carriers of electrons and holes. The drift is caused by the internal electric field generated by the diffusion potential at the junction, and the drift is taken out. As the material of the solar cell, monocrystalline silicon, polycrystalline silicon, amorphous silicon, amorphous silicon germanium, the tetrahedral type such as amorphous SiC amorphous semiconductor and, CdS, II-VI group and GaAs, such as Cu ₂ S, such as GaAlAs III
-V group compound semiconductors and the like. In particular, thin-film solar cells using amorphous semiconductors are promising because of their advantages such as the ability to produce large-area films, smaller thicknesses, and the ability to be deposited on any substrate material compared to single-crystal solar cells. Have been watched.

[0004] Amorphous silicon solar cells, crystalline thin-film solar cells, and the like use a thin-film solar cell element formed on a flexible substrate such as stainless steel to provide a thin, light, and more flexible solar cell. It is made in the form of a battery module and is in practical use. In addition, the surface is coated with a coating material for weather resistance and protection from mechanical damage.

Next, the structure of a conventional solar cell will be specifically described. As a configuration of a conventional solar cell, for example, as shown in FIG. 4, light is incident from the opposite side of the substrate, and the structure of the amorphous silicon solar cell element is such that a lower electrode 42 is provided on a substrate 41 and a lower electrode 42 is provided thereon. N-layer 43, i-layer 4 of thin film
4, a semiconductor layer composed of a p-layer 45 is laminated, and an upper electrode 46 is further provided. Further, a grid electrode 47 and a bus bar for current collection are provided.

Further, in order to protect the solar cell from mechanical damage, moisture and the like, a covering material made of glass, a polymer resin or the like is provided.

[0007] Since sunlight is reflected on the surface of the solar cell element, not all sunlight can be used effectively, and various measures have been taken to reduce the reflection. The antireflection film is designed so that the reflection at the wavelength at which the solar cell element has the highest sensitivity is minimized, but the reflection is not sufficiently small at other wavelengths. Therefore, for the purpose of confining light in the semiconductor layer, which is a photoactive layer, and extending the optical path length, a so-called texture structure in which the surface of the solar cell element is uneven has been devised to further reduce reflection. ing. On the other hand, according to the apparatus disclosed in Japanese Patent Application Laid-Open No. 62-90983, an attempt has been made to form irregularities by etching an impurity layer on the opposite side of the substrate with a material having a different etching rate.

In an amorphous solar cell in which a texture structure is formed on a glass substrate, there is a method in which light is effectively used by using a transparent conductive film on the light incident side as a structure having irregularities.

In a single-crystal solar cell, for example, fine irregularities are formed on a light incident surface of a substrate surface by an etching method, and then n-type is formed by doping to form a pn-type solar cell.
There is known a configuration in which a junction is formed to reduce light reflection and increase a photocurrent.

Further, in the above-mentioned amorphous silicon solar cell in which light is incident from the side opposite to the substrate, the anti-reflection film has a preferable thickness of about 1000 A from the refractive index of amorphous silicon and the refractive index of the anti-reflection film. It is designed and at this thickness it is practically impossible to provide a textured structure.

Although it is possible to simply form a transparent conductive film having a texture structure without performing optical design as an anti-reflection film, the problem in this case is that a high substrate temperature is required for texturing. Is required, which may affect the underlying amorphous silicon layer, and increase the cost and decrease the throughput if a thick transparent conductive film is formed. Therefore, in reality, an antireflection film having a uniform film thickness is employed, and a texture structure is not used.

Further, in the case where the texture is formed by the above-described etching, desired irregularities cannot be obtained unless the etching rate is delicately controlled, and there is a possibility that the base may be etched when the etching is performed excessively. Actually, it was difficult to texture it because of the fact that it is necessary to prepare a mixed crystal of microcrystal and amorphous.

Further, in the single crystal solar cell, there is a problem in that the bonding portion is mechanically weakened due to the formation of the unevenness, and as a result, a short portion is generated and conversion efficiency is impaired.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solar cell which makes it possible to more effectively utilize sunlight and has a high photoelectric conversion efficiency.

[0015]

According to the present invention, there is provided a solar cell in which the surface on the light incident side is coated with a coating material, wherein the coating material has irregularities and a light-transmitting electrodeposition containing a filler. It is characterized by being made of resin.

The coating material has a height difference of irregularities of 0.5 μm.
Preferably, the filer is an organic or inorganic material having a particle size of 0.5 μm to 10 μm.

[0017]

Next, an embodiment of the present invention will be described.

The solar cell of the present invention has been completed by examining in more detail the findings obtained through experiments conducted by the inventors of the present invention with respect to a configuration that enables effective use of light from the solar cell. Discloses a method in which the surface of a solar cell is coated with an organic or inorganic transparent coating material, and the coating material has a texture structure having irregularities, whereby light is scattered and light can be effectively used. In the configuration of the solar cell of the present invention, the solar cell is suitable for a single crystal, a polycrystal, and an amorphous silicon solar cell in which light enters from the side opposite to the substrate.

As the coating material having the texture structure,
It is necessary that the material be transparent so as to transmit sunlight or indoor light. In addition, in order to scatter light, the refractive index of the coating material needs to be larger than the refractive index 1 of air. Preferably, the refractive index must be 1.4 or more.

Further, it is preferable that the coating material having the texture structure has a function as a protective film for protecting the solar cell as well as a function for effectively using the light as described above. In this case, the coating material is required to have good weather resistance and stability to heat, humidity and light. Further, when the solar cell is used, the solar cell may be bent or subjected to an impact in some cases, so that it is necessary to have both mechanical strength and peel strength.

The thickness of the coating material having the texture structure is preferably selected depending on the type of the material, since it is preferable that electrical insulation and moisture resistance are maintained and the light transmittance is not impaired. However, typically, about 0.5 μm to 50 μm is appropriate. If the function of the texture coating material alone is not sufficient, another coating material may be laminated.

In order to enable effective use of light, the wavelength of light contributing to power generation in a solar cell must be between 400 nm and 900 nm.
Since the visible light is about nm, it is preferable that the height difference between the irregularities is 0.5 μm to 10 μm. The unevenness does not need to be a uniform shape such as a patterned one, and the height difference between the unevenness and the random shape is 0.5 μm.
It is sufficient if it is within the range of 10 μm to 10 μm. The shape of the unevenness may be any shape such as a pyramid, a hemisphere, and a trapezoid. As a measure of the surface roughness, for example, when the haze ratio indicating the component ratio of the diffused light to the transmitted light is measured by using a measuring method determined by JIS K7105 only for the coating material, a suitable haze ratio Is preferably 10% or more.

As a method of providing such a texture structure, a method of transferring to a coating material by a mold or the like, a method of electrostatically spraying fine particles, or an electrodeposition paint to which a filler is added can be used. In particular, the electrodeposition method is a method suitable for forming a coating material having a texture structure. Examples of the filler include inorganic pigments such as ZnO and TiO ₂ ,
Ceramics such as l ₂ O ₃ , AlN, BN, etc., glass frit, fine particle polymer, SnO ₂ , In ₂ O ₃ , ITO
And the like are appropriately selected from metal oxides and the like. However,
It is necessary to select a material or a process that can maintain the particle size of the filler without melting and flattening after forming the electrodeposition film.

As the material of the texture coating material, a polymer resin such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, polyimide and epoxy is preferably used.

When an electrodeposition resin is used, an acrylic resin, a polyester resin, an epoxy resin,
It is appropriately selected from urethane resin, fluororesin, melamine resin, butadiene resin and the like as desired. Further, in order to make these resins water-soluble and to perform electrophoresis, it is necessary to introduce a functional group that causes ionization in an aqueous solution, and examples of the functional group include a carboxyl group and an amino group. Electrodeposition paints can be classified into cationic and anionic based on the polarity of the functional groups. Since the polarities applied to the solar cells are different from each other, they may be appropriately selected according to the desired polarities of the solar cells. Further, in order to cure the electrodeposited resin by heating, melamine crosslinking, carbon-carbon double bond,
In order to utilize a urethane bond or the like, a functional group that causes such a cross-linking reaction is appropriately introduced into the skeleton resin or the side chain.

In order to form a uniform film, it is important that these electrodeposition resins are stably suspended without being precipitated in a solution. For this purpose, the resin is made of colloidal particles having an appropriate size. It is desirable that The particle size of the colloid particles is preferably in the range of about 10 nm to 100 nm, and the particle size is desirably monodispersed.
The preferred molecular weight of the skeletal resin constituting the colloidal particles has a weight average molecular weight of about 1,000 to 20,000.

In order to selectively and effectively insulate a defective portion of a solar cell with an electrodeposited resin in order to improve light resistance, heat resistance, moisture resistance, selectivity of a defective portion, etc. It is preferable that the weight of the electrodeposition film is large, and for this purpose, the coulomb efficiency of the electrodeposition paint is preferably 10 mg / C or more. As a solvent for the electrodeposition paint, a transparent conductive oxide, a solution containing an acid or alkali at a concentration that does not easily dissolve solar cell constituent materials such as a semiconductor layer and a lower electrode,
Alternatively, a solution containing a metal salt thereof is used. As the metal salt, a salt having a negative standard electrode potential and a hydrogen overvoltage value smaller than the absolute value of the standard electrode potential is used as a metal constituting the salt. Electrodeposition paints are used after being diluted with deionized water.
The solid content is preferably in the range of about 1% to about 25%. The conductivity of the electrodeposition solution is preferably in the range of 100 μS / cm to 2000 μS / cm so that the resin can be stably suspended and electrophoresis can easily occur.

Depending on the method of manufacturing the solar cell, a solvent may be used or heat treatment may be performed after electrodeposition. In this case, it is required that the deposited electrodeposition film is not affected by these treatments.

In the step of depositing the electrodeposited resin, the solar cell and the counter electrode are immersed in an electrodeposition paint, and a voltage is applied between the solar cell and the counter electrode to deposit the electrodeposited resin on the surface of the solar cell. It is done by doing. When a voltage is applied to the solar cell, it may be applied to the conductive substrate or the lower electrode. In the case of single crystal and polycrystal, an electrodeposition film is deposited on the solar cell surface, and in the case of amorphous silicon, the electrodeposition film is deposited on the transparent conductive film.

The material of the counter electrode is required not to be corroded in the electrodeposition paint, and is made of platinum, carbon,
Nickel, stainless steel and the like are preferably used. Also,
It is necessary to make the area of the counter electrode a constant ratio with respect to the area of the solar cell in order to make electrodeposition uniform. As a so-called pole ratio, the ratio between the area of the solar cell and the area of the counter electrode is 1 It is preferably in the range of / 2 to 2/1. The distance between the solar cell and the counter electrode is an important factor in maintaining the uniformity of electrodeposition, but there is a suitable range depending on various conditions such as the conductivity of the electrodeposition paint and the applied voltage. More specifically, 10 mm to 100 mm is desirable.

In order for the electrodeposition film to be deposited only on the front surface of the solar cell, it is not preferable to expose a conductive portion such as a substrate to the electrodeposition paint. It is desirable to cover the surface of the conductive substrate with an insulating coating material such as a plastic film or a rubber magnet.

Electrodeposition can be carried out by a constant voltage method or a constant current method. For example, in the constant voltage method, the voltage applied to the solar cell is hydrogen calculated from the electrode potential defined by the Nernst equation. A voltage higher than the generated potential, specifically, a voltage of 2 volts or more, which is a value obtained by adding an overvoltage to the theoretical decomposition voltage of water, is required. Furthermore, since the preferable range of the applied voltage differs between the case where the conductivity of the electrodeposition paint and the polarity of the voltage applied to the solar cell are reverse bias and the case where the polarity is forward bias, the configuration, area, and electric power of each solar cell are different. An appropriate voltage range is determined from various points such as physical properties such as conductivity of the coating material and polarity of applied voltage.
V range. In addition, since part of the applied voltage is also applied to the solar cell, if the polarity is such that the solar cell is reverse-biased, the voltage must be within a range where the solar cell does not break down. No.

In the electrodeposition by the constant current method, the current density is preferably 0.1 to 10 A / dm ² in order to form a dense electrodeposited film, depending on the degree of shunt of the solar cell.
Range.

FIGS. 5 and 6 show an example of the electrodeposition apparatus.

FIG. 5 shows an example of a batch type electrodeposition apparatus. In the figure, 51 is an electrodeposition tank, 52 is an electrodeposition liquid, 53 is a counter electrode, 54 is a solar cell substrate, 55 is a solar cell active layer, 56
Indicates a power supply, and 57 indicates a wiring.

FIG. 6 shows an example of a roll-to-roll type electrodeposition apparatus. In FIG. 5, the solar cell has a cut sheet shape, and the electrodeposition process is a single-wafer process. However, if necessary, the electrodeposition is continuously performed by a roll-to-roll type apparatus shown in FIG. It is also possible. In the figure, 70 is a substrate, 6
1 is a substrate feeding roller, 62 is a substrate take-up roller, 63 is an electrolytic tank, 64 is a cleaning tank, 65 is a drying furnace, 66
Is a power supply, 67 is a mask film feeding roller, 68
Denotes a mask film take-up roller, 69 denotes a mask film, 71 denotes a counter electrode, and 72 denotes a conductive roller.

As a preferred embodiment in this figure, the solar cell is nip type amorphous silicon deposited on a stainless steel substrate, and an upper electrode of ITO is formed on the light incident side. The solar cell substrate 70 is delivered from the substrate delivery roller 61 and is immersed in the electrolytic cell 63,
After passing through the cleaning tank 64 and the drying furnace 65, the winding roll 6
It is wound up in 2. Before being immersed in the electrolytic cell 63, a film 69 for the back surface mask of the solar cell is sent out from the mask film sending-out roller 67 and bonded to the back surface of the solar cell substrate 70. After the completion of the electrodeposition, the film is peeled again, washed and dried, and then wound up by a winding roller 68. Conductive roller 72 in contact with solar cell substrate 70 and electrolytic cell 6
The voltage of the power supply 66 is applied between the opposing electrodes 71 immersed in 3.

Hereinafter, a configuration example of the solar cell of the present invention will be described with reference to the drawings.

Preferred examples of the structure of the solar cell of the present invention are shown in FIGS.
FIG. 3 schematically shows this.

FIG. 1A is an amorphous silicon solar cell in which light is incident from the side opposite to the substrate, and FIG.
(A) Solar cell having triple structure, FIG. 2
2A shows a crystalline solar cell, and FIG. 2B shows a thin-film polycrystalline solar cell. FIG. 3 is a diagram of FIG. 1A as viewed from above. In the figure, 1 is a solar cell body, 11 is a substrate, 12 is a lower electrode, 13 is an n layer, 14 is an i layer, 15 is a p layer, 16
Is an upper electrode, 17 is a grid electrode, 18 is a bus bar, 1
9 represents a covering material.

The substrate 11 is a member for mechanically supporting the semiconductor layers 13, 14, and 15 in the case of a thin-film solar cell such as amorphous silicon, and is sometimes used as an electrode. The substrate 11 has semiconductor layers 13, 14, 1
5 is required to have heat resistance to withstand the heating temperature at the time of film formation, and may be a conductive material or an electrically insulating material. Specific examples of the conductive material include Fe, Ni, Cr, and A.
1, Mo, Au, Nb, Ta, V, Ti, Pt, Pb,
Metals such as Ti or alloys thereof, for example, brass, thin plates such as stainless steel and composites and carbon sheets thereof,
Galvanized steel sheet and the like, and as the electrically insulating material, polyester, polyethylene, polycarbonate,
Cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide,
Films or sheets of heat-resistant synthetic resin such as polyimide or epoxy, or composites of these with glass fiber, carbon fiber, boron fiber, metal fiber, etc., and metals of different materials on the surface of thin plates of these metals, resin sheets, etc. Thin films and / or SiO ₂ , Si ₃ N ₄ ,
Examples thereof include those obtained by subjecting an insulating thin film such as Al ₂ O ₃ or AlN to a surface coating treatment by a sputtering method, a vapor deposition method, a plating method, or the like, glass, ceramics, and the like.

The lower electrode 12 is composed of the semiconductor layers 13, 14, 1
5 is one electrode for taking out the electric power generated in 5,
The semiconductor layer 13 is required to have a work function that becomes an ohmic contact. As a material,
Al, Ag, Pt, Au, Ni, Ti, Mo, W, F
e, V, Cr, Cu, stainless steel, brass, nichrome, SnO ₂ , In ₂ O ₃ , ZuO, ITO, and other so-called simple metals or alloys, and transparent conductive oxides (TC
O) and the like. The surface of the lower electrode 12 is preferably smooth, but may be textured when irregular reflection of light is caused. When the substrate 11 is conductive, the lower electrode 12 does not need to be provided.

Examples of the semiconductor layer of the solar cell used in the present invention include a compound semiconductor such as a pin junction amorphous silicon, a pn junction polycrystalline silicon, and CuInSe ₂ / CdS. In amorphous silicon solar cells, i
As a semiconductor material constituting the layer 14, a-Si: H,
a-Si: F, a-Si: H: F, a-SiGe: H,
a-SiGe: F, a-SiGe: H: F, a-Si
So-called group IV and group IV alloy-based amorphous semiconductors such as C: H, a-SiC: F, and a-SiC: H: F are exemplified. The semiconductor material forming the p-layer 15 or the n-layer 13 can be obtained by doping the above-described semiconductor material forming the i-layer 104 with a valence electron controlling agent.
As a raw material, a compound containing an element of Periodic Table III is used as a valence electron controlling agent for obtaining a p-type semiconductor. Group III elements include B, Al, Ga,
In. As a valence electron controlling agent for obtaining an n-type semiconductor, a compound containing an element of Periodic Table V is used. Group V elements include P, N, As, and Sb.

The solar cell of the present invention can 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 16 is composed of the semiconductor layers 13, 14, 1
5 is an electrode for taking out the electromotive force generated in 5 and forms a pair with the lower electrode 12. The upper electrode 16 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 solar cell because the sheet resistance is low. Further, since the upper electrode 16 is located on the light incident side, it needs to be transparent, and is also called a transparent electrode. The upper electrode 16 desirably has a light transmittance of 85% or more in order to efficiently absorb light from the sun, a white fluorescent lamp, or the like into the semiconductor layer. Is desirably 100 Ω / □ or less in order to cause the lateral flow in the semiconductor layer. Materials having such characteristics include SnO ₂ , In ₂ O ₃ , ZnO, CdO, and CdSn.
O ₄ And metal oxide semiconductors such as ITO (In ₂ O ₃ + SnO ₂ ).

Next, the grid electrode 17 is connected to the semiconductor layer 13,
Electrodes for extracting the electromotive force generated in 14 and 15 and are called current collecting electrodes. The grid electrode 17 is the semiconductor layer 1
A suitable arrangement is determined from the magnitude of the sheet resistance of the upper electrode 5 or the upper electrode 16, but it is formed in a substantially skewered shape, and is designed so as not to hinder light incidence as much as possible.

It is required that the grid electrode has a low specific resistance and does not become a series resistance of the solar cell. The desired specific resistance is 10 ⁻² Ωcm to 10 ⁻⁵ Ωcm, and the material of the grid electrode is Ti, Cr. , Mo, W, Al, Ag, N
Metal materials such as i, Cu, Sn, etc. and Ag, Pt, Cu, C
A so-called conductive paste is prepared by mixing a polymer binder and a binder solvent in an appropriate ratio with a powder of a metal such as these or an alloy thereof in an appropriate ratio.

The bus bar 18 used in the present invention
Is an electrode for collecting the current flowing through the grid electrode 17 at one end. Ag, Pt, C as electrode material
A metal such as u, C, or an alloy thereof can be used. As a form, a wire-like or foil-like thing may be attached, or the same conductive paste as the grid electrode 17 may be used. For example, copper foil,
Alternatively, tin-plated copper foil with an adhesive may be used in some cases.

The solar cell manufactured as described above is modularized by encapsulation to improve weather resistance and maintain mechanical strength when used outdoors. Specifically, as the encapsulation material, EVA is preferably used for the adhesive layer in terms of adhesion to a solar cell, weather resistance, and a buffer effect. Further, in order to further improve moisture resistance and scratch resistance, a fluorine-based resin is laminated as a 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 tetrafluoroethylene and ethylene
E (such as Tefzel manufactured by DuPont), polyvinyl fluoride (such as Tedlar manufactured by DuPont), and polychlorofluoroethylene CTFE (neoflon manufactured by Daikin Industries, Ltd.). The weather resistance may be improved by adding an ultraviolet absorber to these resins.

In the method of manufacturing a solar cell according to the present invention, the semiconductor layers 13, 14, 15 and the lower electrode 12, the upper electrode 1
6, the grid electrode 17, the bus bar 18, and the like are formed by a generally known method.

The amorphous silicon semiconductor layer may be formed by vapor deposition, sputtering, RF plasma CVD,
Microwave plasma CVD, ECR, thermal CVD,
A known method such as an LPCVD method is used as required. As a method adopted industrially, an RF plasma CVD method in which a source gas is decomposed by plasma and deposited on a substrate is preferably used. Further, in the RF plasma CVD method, the decomposition efficiency of the raw material gas is as low as about 10%,
There is a problem that the deposition rate is as low as about 1 A / sec to about 10 A / sec. However, a microwave plasma CVD method can be used as a film formation method which improves this point. In the case of polycrystalline silicon, Cu
In the case of InSe ₂ / CdS, it is formed by a method such as electron beam evaporation, sputtering, or electrolysis of an electrolytic solution.

As a reaction apparatus for performing the above film formation, a batch type apparatus or a continuous film formation apparatus can be used as desired.

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

Since the grid electrode 17 is formed in a skewered shape,
Examples of the formation method include a sputtering method using a mask pattern, resistance heating, a CVD evaporation method, a method of depositing a metal layer on the entire surface and then etching and patterning the same, a method of directly forming a grid electrode pattern by optical CVD, and a method of forming a grid electrode. There is a method of forming the mask by forming a negative pattern of a pattern and then forming the mask, and a method of forming the mask by printing a conductive paste. In the screen printing method, a conductive paste is used as a printing ink using a screen in which a desired pattern is formed on a mesh made of polyester or stainless steel, and the electrode width can be set to a minimum of about 50 μm. As the printing machine, a commercially available screen printing machine is suitably used. The screen-printed conductive paste is heated in a drying oven to crosslink the binder and volatilize the solvent.

As a method of forming the bus bar 18, a metal wire may be fixed with a conductive adhesive, a copper foil may be attached, or the bus bar 18 may be formed in the same manner as the grid electrode 17. As a method of encapsulation, for example, a method in which a solar cell substrate and the resin film are heated and pressed in a vacuum using a commercially available device such as a vacuum laminator is desirable.

[0056]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to these Examples.

(Example 1) An amorphous silicon solar cell 100 having a coating material having a texture structure shown in FIG. 1A formed on the surface thereof was manufactured as follows.

First, SUS4 which has been sufficiently degreased and washed
30BA substrate (30cm x 30cm, thickness 0.2m
m) 11 was placed in a DC sputtering device (not shown), and an AlSi alloy layer and a ZnO layer were deposited to a thickness of 200 nm, respectively, to form a lower electrode 12. The ZnO layer has a reflection increasing function,
Provided for shunt prevention function.

The substrate 11 is taken out and put into an RF plasma CVD film forming apparatus (not shown), the n-layer 13, the i-layer 14, and the p-layer 15
Were deposited in this order.

Thereafter, it is placed in a resistance heating vapor deposition device (not shown), and while keeping the internal pressure of 1 × 10 ⁻⁴ Torr while introducing oxygen, an alloy of In and Sn is vapor deposited by resistance heating to also have an antireflection effect. A transparent ITO upper electrode 16 having a function of 70 nm was deposited.

Next, the substrate 11 is set on a screen printing machine (not shown), and the grid electrode 1 having a width of 100 μm and a length of 8 cm is provided.
8 were printed at 1 cm intervals. At this time, a conductive paste of Ag was used as an electrode material. After printing, the substrate 11
Was placed in an oven at 150 ° C. for 30 minutes to cure the conductive paste.

Further, a copper foil busper 109 having a width of 5 mm with an adhesive was bonded thereto to produce a single 30 cm square cell shown in FIG.

Next, the electrodeposition paint was bathed as follows. As the electrodeposition paint 202, an acrylic cationic electrodeposition paint having a solid content of 10% was used. The electrodeposition paint contained 5% of a fluorine-based filler having a particle size of 3 μm. Next, the back side of the substrate 11 is covered with an insulating film made of plastic to cover the substrate 1 during electrodeposition.
1. The electrodeposition tank 5 shown in FIG.
1 was immersed. As the counter electrode 53, a SUS304 stainless plate having a size of 30 cm × 30 cm and a back side sealed with a plastic insulating film with respect to the substrate 11 was used so that the pole ratio was 1: 1. Electrodeposition was performed by applying a voltage of plus 10 V to the substrate 54 and holding it for 60 seconds. The solar cell 1 is lifted from the electrodeposition tank 51, washed sufficiently with pure water, and unnecessary electrodeposition paint is washed away at 50 ° C. /
And then left for 30 minutes to dry the water. Thereafter, the temperature of the oven was raised at a rate of 10 ° C./min, and was maintained at 180 ° C. for 30 minutes to cure the electrodeposited resin. The substrate 11 was taken out of the oven and returned to room temperature. Further, ten samples were produced in the same manner.

When the surface roughness of the obtained sample was measured by a stylus type surface roughness meter, the average roughness was Ra = 2 μm, and it was found that a sufficiently textured surface could be obtained.

(Comparative Example 1) Next, for comparison, a solar cell 4 having the same structure as in Example 1 but without the covering material having a texture structure and having the structure shown in FIG. 4 was produced.

As in the first embodiment, the upper electrode 4
6 were formed. Next, the grid electrode 47 was printed in the same manner as in Example 1. Furthermore, copper foil with an adhesive was laminated as a bus bar, and ten single cells of 30 cm square shown in FIG. 4 were produced.

The characteristics of the samples of Example 1 and Comparative Example 1 produced as described above were measured as follows.

First, in order to measure the surface reflectance of the sample, 40 μm was applied to the sample surface using MCPD-200 manufactured by Union Giken.
Light from 0 nm to 800 nm was irradiated to detect reflected light from the sample surface, and the reflectance was measured. FIG. 7 shows the results.
As shown in FIG. 7, the sample of Example 1 has a low reflectance, indicating that light is absorbed by the solar cell and is effectively used.

Next, the spectral sensitivity (external collection efficiency) of each wavelength of this sample was measured. The measurement method is JIS C891
A method for measuring spectral sensitivity characteristics of a five-crystal solar cell was used.

FIG. 8 shows the results. As is clear from FIG. 8, it was found that the spectral sensitivity of Example 1 was higher than that of Comparative Example 1.

As can be seen from FIG. 7 and FIG.
Has a good surface anti-reflection effect, and has good reflectance and collection efficiency.

Next, the solar cell characteristics of the sample were measured using a pseudo solar light source having a light intensity of 100 mW / cm ^{2 in} the AM1.5 global sunlight spectrum. As a measurement method,
The short-circuit current value of the solar cell was measured using the JIS C8913 crystalline solar cell output measuring method. The short-circuit current values of Example 1 and Comparative Example 1 were 12 ± 0.5 mA, respectively.
/ Cm ² , 10 ± 0.7 mA / cm ² ,
It was found that good properties can be obtained by the texture coating material.

As described above, it has been proved that the solar cell of the present invention can obtain good characteristics.

Example 2 Next, a solar cell having the structure shown in FIG. 1A was manufactured in substantially the same manner as in Example 1 except that the electrodeposition paint was changed.

First, as in the case of the first embodiment, the SUS430BA
Substrate (30 cm x 30 cm, thickness 0.2 mm) 101
A lower electrode 12 is formed thereon, and then placed in an RF plasma CVD film-forming apparatus (not shown) to form an n-layer 13, an i-layer 14, and a p-layer 1.
The deposition was performed in the order of 5. As in the case of the first embodiment, the transparent upper electrode 16 having a function of also
Deposited.

Next, the electrodeposition paint was bathed as follows.
First, as in Example 1, 15% of acrylic melamine and 2% of alumina having a particle size of 5 μm were added, and dispersed by a ball mill for 10 hours. Next, the electrodeposition paint was put into the electrodeposition tank 51 of FIG. 5, and the substrate 11 was immersed to perform electrodeposition. afterwards,
After sufficiently washing with pure water, the electrodeposition resin was cured in an oven. The washing and curing conditions were the same as in Example 1. Thereafter, the substrate 11 was taken out of the oven, and after cooling, the grid electrode 17 was formed by screen printing. Further, a copper foil bus bar 18 with an adhesive was laminated thereon, and the 30 cm shown in FIG.
A corner single cell was fabricated. Similarly, ten samples were prepared.

When the surface roughness of the sample was measured by a stylus type surface roughness meter, the average roughness was Ra = 3 μm, and a sufficiently textured surface was obtained. When the characteristics of the obtained sample were measured in the same manner as in Example 1, the short-circuit current was 11.8 ± 0.
It was 3 mA / cm ² , which was a better result as compared with Comparative Example 1.

Example 3 Next, in Example 1, the structure of the solar cell is shown in FIG.
A solar cell was formed in the same manner as in Example 1 except that a textured coating material was provided on the surface, and a silicon plasma was formed by a microwave plasma CVD method. Produced.

First, a lower electrode 12 composed of an Ag layer and a ZnO layer is formed on a substrate 11 and then placed in a microwave plasma CVD film-forming apparatus (not shown) to form an n-layer 13 and an i-layer 1.
4, deposition was performed in the order of the p layer 15 to form a bottom layer. At this time, the i-layer 14 was a-SiGe. Next, the n-layer 2
3, the i-layer 24 and the p-layer 25 were deposited in this order to form a middle layer. The i-layer 24 was made of a-SiGe similarly to the bottom layer. Next, an n-layer 33, an i-layer 34, and a p-layer 35 were sequentially deposited to form a top layer. The i-layer 34 was a-Si.
Next, as in Example 1, a transparent upper electrode 16 having a function also having an antireflection effect was deposited to a thickness of 70 nm. In ₂ O ₃ (IO) was used as the upper electrode 16.

Next, after washing and drying, an electrodeposition treatment was performed using an epoxy-based cationic electrodeposition paint. The composition of the electrodeposition coating material used was a composition containing 10% of epoxy resin and 3% of SiO ₂ powder having a diameter of 5 μm. At the time of electrodeposition, a forward bias was applied to the solar cell. Thereafter, the solar cell was washed and cured. The grid electrode 17 was printed, and the bus bar 18 was further laminated thereon to produce a 30 cm square triple cell shown in FIG. Similarly, 1
Zero samples were prepared.

When the surface roughness of the sample was measured by a stylus type surface roughness meter, the average roughness was Ra = 10 μm, and a sufficiently textured surface was obtained.

(Comparative Example 2) For comparison, a solar cell having the same structure as in Example 3 but without a texture coating material was produced as follows.

The upper electrode 1 was formed on the substrate 11 in the same manner as in the first embodiment.
6 were formed. Next, the grid electrode 17 was printed in the same manner as in Example 1. Further, a copper foil with an adhesive was laminated as a bus bar 18, and ten single cells of 30 cm square shown in FIG. 3 were produced.

The solar cell characteristics of the manufactured samples of Example 3 and Comparative Example 2 were measured in the same manner as in Example 1.
The short-circuit current is 6 ± 0.5 mA / cm ² , 5.3 ±
It was 0.5 mA / cm ² .

From the results of Example 3 and Comparative Example 2, it was demonstrated that the solar cell of the present invention had good characteristics and good durability.

[0086]

As described above, according to the first to third aspects of the present invention, the surface on the light incident side is covered with a light-transmissive coating material having irregularities to enable effective use of light. It is possible to provide a solar cell having good characteristics.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the configuration of a solar cell of the present invention.

FIG. 2 is a schematic cross-sectional view showing a configuration of a solar cell of the present invention.

FIG. 3 is a schematic cross-sectional view illustrating a configuration of a solar cell of the present invention.

FIG. 4 is a schematic diagram showing a configuration of a conventional solar cell.

FIG. 5 is a schematic view showing an example of an electrodeposition apparatus.

FIG. 6 is a schematic view showing an example of a roll-to-roll type electrodeposition apparatus.

FIG. 7 is a graph showing the light reflectance of the solar cell of Example 1.

FIG. 8 is a graph showing the spectral sensitivity of the solar cell of Example 1.

[Explanation of symbols]

1,4 solar cell body, 11,41 substrate, 12,42
Lower electrode, 13, 23, 33, 43 n-layer, 14, 2
4,34,44 i-layer, 15,25,35,45p
Layer, 16, 46 upper electrode, 17, 47 grid electrode, 18 bus bar, 19 coating material, 51 electrodeposition tank, 5
2 Electrodeposition liquid, 53 Counter electrode 54 Solar cell substrate, 55
Solar cell active layer 56 Power supply 57 Wiring 61 Substrate delivery roller, 62 Substrate take-up roller, 63 Electrolyte tank, 64 Cleaning tank, 65 Drying furnace, 66 Power supply, 67
Mask film feed roller, 68 Mask film take-up roller, 69 Mask film, 70
Substrate, 71 Counter electrode, 72 Conductive roller.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Soichiro Kawakami 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tsutomu Murakami 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Takahiro Mori 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hirofumi Ichinose 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Hiroshi Yamamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-63-102279 (JP, A) JP-A-4-266068 (JP, A) 63-15071 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/04 H01L 31/042

Claims (3)

(57) [Claims] 1. A solar cell having a light incident side surface coated with a coating material, the coating material having irregularities and containing a filler.
A solar cell comprising a light-transmissive electrodeposited resin . 2. The coating material according to claim 1, wherein a height difference of the unevenness is 0.5 μm.
Solar cell according to claim 1, characterized in that the M～10myuemu. 3. The filer has a particle size of 0.5 μm to 1 μm.
The solar cell according to claim 1 , wherein the solar cell is an organic or inorganic material having a thickness of 0 µm.