JP3078938B2 - 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 suitable for outdoor installation.

[0002]

2. Description of the Related Art (Relationship between antireflection film and current collecting electrode) Conventionally, a general structure of a solar cell is, for example, in the case of a crystalline solar cell, an antireflection layer and a current collector are provided on the light incident side of a semiconductor pn junction. The electrodes are stacked in that order, and a lower electrode is provided on the back side of the semiconductor junction. here,
The antireflection film is optically designed so as to eliminate the reflection component as much as possible and to increase the incident component in order to effectively take in sunlight. Further, the antireflection film is formed to have a desired film thickness by calculating a suitable film thickness from the refractive index.

On the other hand, the current collecting electrodes are provided in a grid on the antireflection layer in order to extract current effectively. As a material for the electrode, a material having a low specific resistance such as silver, aluminum or copper is selected.

(Appearance problem of current collecting electrode) In the above conventional example, the antireflection layer constituting the solar cell element has a minimum value of reflection at a specific wavelength.
Generally, a blue-based interference color is easily observed in appearance, while the current collecting electrode has a metallic luster because it is a metal. For this reason, the grid-like metal is arranged on the blue solar cell element, and when the solar cell is installed in a building, there is a problem that color harmony with surroundings is poor and aesthetic appearance is impaired.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a roofing material,
It is an object of the present invention to provide a solar cell which can be applied to buildings such as wall materials in harmony.

[0006]

According to the present invention, there is provided a solar cell comprising a solar cell element having an antireflection film and a current collecting electrode provided on the solar cell element. It is characterized in that it is covered with a coating layer made of an organic or inorganic substance containing a pigment having a similar color. In this case, the current collecting electrode is desirably formed by a screen printing method or an electrodeposition method because it is necessary to selectively cover the current collecting electrode.

As the solar cell element of the present invention, any of a single crystal, a polycrystalline semiconductor, and an amorphous semiconductor can be used, and further, a polycrystalline semiconductor thin film formed on a substrate may be used. Specifically, in the case of a crystalline system, for example, silicon, GaAs, CdS, or the like is suitably used, and in the case of an amorphous system, silicon, silicon germanium, or the like is suitably used.

In general, a crystalline solar cell does not require a substrate, but an amorphous semiconductor or some polycrystalline semiconductors are thin films and are deposited on the substrate. For example, in the case of an amorphous solar cell, a thin film p
A semiconductor junction consisting of a layer, an i layer, and an n layer is formed. Furthermore, a pin junction is used to improve spectral sensitivity and voltage.
A so-called tandem type laminated as described above may be used. When the substrate material is insulating like glass or ceramics, a conductive layer is provided as a lower electrode.

Also, when the substrate material is conductive,
There is no need to provide a lower electrode. Examples of conductive substrate materials include Fe, Ni, Cr, Al, Mo, Au, Nb, Ta,
Metals such as V, Ti, Pt, Pb or alloys thereof;
For example, a thin plate of brass, stainless steel, or the like or a composite thereof may be used.

An antireflection layer is formed on the light incident side of the semiconductor layer. The antireflection layer is optically designed to eliminate reflection and increase incidence in order to effectively take in sunlight. Such a material is, for example, SiO ₂ or SiO _{2 in} a crystalline solar cell. , Ta ₂ O ₅ or the like of an insulating material is used, desired film thickness antireflection layer is calculated suitable thickness from each refractive index is formed.

On the other hand, in the case of an amorphous silicon solar cell, unlike a crystalline solar cell, the current generated by light cannot flow in the lateral direction with respect to the semiconductor junction because of the high sheet resistance of the surface. Therefore, a transparent upper electrode for lowering the sheet resistance is required.

The sheet resistance of the upper electrode is 100Ω.
/ □ or less is desirable. A material having both the function of the upper electrode and the function of the antireflection layer is used.
Materials having such properties include SnO ₂ , In
₂ O ₃ , ZnO, CdO, CdSnO ₄ , ITO (In ₂ O
₂ + SnO ₂ ). As a manufacturing method thereof, a resistance heating evaporation method, an electron beam heating evaporation method, a sputtering method, a spray method, or the like can be used.

[0013]

In the structure of the present invention, the current collecting electrode is covered with a thin film. The thin film is made of a polymer resin or an inorganic material containing a pigment so as to match the color tone of the solar cell. As the material of the polymer resin, generally used polyester, ethylene-vinyl acetate copolymer, acrylic resin, epoxy resin, urethane and the like are preferably used. As a method of coating such a polymer resin, a commonly used method is used, for example, a method of dipping by dissolving in a solvent or a method of screen printing, a method of coating by electrodeposition,
However, a screen printing method or an electrodeposition method is preferable since it is necessary to paint only on the current collecting electrode portion.
In the case of screen printing, an ink containing a pigment may be printed on the current collecting electrode using a plate matching the pattern of the current collecting electrode.

In the case of the electrodeposition method, a relatively low molecular weight anionic electrodeposition coating material having an ionized functional group such as a carboxylic acid group or an amino group or a cationic electrodeposition coating solution is applied to a counter electrode and a solar cell. If the battery is immersed and the current collecting electrode is electrodeposited as a cathode electrode or an anode electrode, an electrodeposition film can be formed only on the current collecting electrode, so that the alignment problem can be avoided. Further, since it is possible to cover not only the surface of the current collecting electrode but also the end face, this is an advantageous method that can completely cover the current collecting electrode. Further, in the electrodeposition method, when coloring, a pigment of a desired color may be mixed in the electrodeposition liquid.

The current collecting electrode in the present invention is formed on the antireflection layer. The shape of the current collecting electrode is as thin as possible so as not to hinder the light incidence, and furthermore, it is formed in a grid shape. Desirably. Further, a configuration may be employed in which the current collected by the current collecting electrode is further collected by a bus bar.

[0016]

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention. The solar cell 100 according to this example was manufactured as follows. First, S which has been subjected to mirror polishing and sufficiently degreased and washed
A lower electrode 102, an n-layer 103, and a substrate 430 made of US430BA (width 10 cm, length 5 cm, thickness 0.1 mm) 101
Deposition was performed in the order of the i-layer 104 and the p-layer 105, and then the antireflection layer 106 was deposited. Then, using a screen printing machine (not shown), a current collecting electrode 1 having a width of 200 μm and a length of 4 cm
07 was printed at an interval of 1 cm and cured (cured) in a heating furnace. Subsequently, a tin-plated copper foil bus bar (not shown) was attached. Using the same procedure, ten solar cells were manufactured as samples.

Thereafter, as shown in FIG.
10 liters of deionized water was put therein, and 2 liters of an anionic acrylic electrodeposition paint mixed with a blue pigment was added while stirring at a speed of 500 rpm. After stirring for 1 hour, the solution was left standing for 2 days for aging to prepare an electrodeposition solution 402.

Next, the substrate 101 was put into the electrodeposition bath 401, and the counter electrode 403 and the bus bar 405 were connected by the conducting wire 407. 30V so that the bus bar 405 becomes negative
, And maintained for 2 minutes. After depositing the coating layer 108 only on the collecting electrode 407 and the bus bar 405,
The substrate 101 was taken out of the electrodeposition bath, washed with deionized water, placed in a thermostat and kept at 150 ° C. for 5 minutes to dry the coating layer 108. As a result, the blue covering layer 108 was able to be laminated on the current collecting electrode 107 and the bus bar (not shown). The film thickness of the coating layer 108 was 5 μm when measured by a stylus-type film thickness meter.

Next, encapsulation of these serialized solar cells was performed in the following procedure. First, EVA (ethylene vinyl acetate) is laminated on the upper and lower sides of the solar cell 100, and further, the fluororesin film ETFE (ethylene tetrafluoroethylene) is laminated, and then charged into a vacuum laminator and held at 150 ° C. for 60 minutes. Vacuum lamination was performed to produce ten solar cell modules. Each of the manufactured sample solar cell modules is N
o. No. 1 to No. Numbered ten. In the obtained solar cell module, the appearance was improved because the current collecting electrode 107 had the same color tone as the solar cell main body.

The initial characteristics of the manufactured solar cell module were measured in the following procedure. First, the sunlight spectrum of AM1.5 was measured at 100 mW / cm ² using a pseudo solar light source (hereinafter referred to as a simulator) using a xenon lamp.
And the current-voltage characteristics of the solar cell were measured.
This characteristic result is normalized by the opening area of the solar cell to 6.5.
% Average initial conversion efficiency was obtained.

Next, the durability characteristics of these samples were evaluated based on the temperature-humidity cycle test A-2 specified in the environmental test method and the durability test method of the crystalline solar cell module of Japanese Industrial Standard C8917. First, the sample is put into a thermo-hygrostat capable of controlling the temperature and humidity, and the temperature is changed from −40 ° C. to +8.
1 cycle test to change to 5 ° C (85% relative humidity)
Repeated 0 times.

Next, when the solar cell characteristics of these samples were measured using a simulator in the same manner as the initial characteristics, the conversion efficiency of the samples after the test was 98% of the initial conversion efficiency, and remarkable deterioration occurred. Did not. When the shunt resistance was measured, it was reduced by about 10%, and no remarkable deterioration occurred. This is considered to be due to an improvement in the durability characteristics, and it is considered that the reason for this is that the formation of the coating layer 108 prevents the current collecting electrode 107 from deteriorating due to humidity. Also, no peeling of the encapsulation resin from the substrate was observed at all, indicating that the passivation layer 107 has a good adhesive effect.

Comparative Example In order to compare the features of this example, a conventional solar cell 300 having the structure shown in FIG. 3 was manufactured as follows. First, a SUS430BA substrate (width: 10 cm, length: 5 cm, thickness: 0.1 mm) 301 was placed in a DC sputtering device (not shown), and Cr was deposited at 2000 ° to form a lower electrode 302 in the same manner as in the first embodiment. The substrate 301 is taken out, put into an RF plasma CVD film forming apparatus (not shown),
03, i-layer 304, and p-layer 305 in this order.
Thereafter, the film is put into a resistance heating vapor deposition device (not shown), and an alloy of In and Sn is vapor deposited by resistance heating.
Was deposited at 700 °.

Next, as in the first embodiment, the substrate 3
01 on a screen printing machine (not shown),
A current collecting electrode 307 having a length of 4 cm was printed at an interval of 1 cm. At this time, an Ag paste was used as the conductive paste. After printing, the substrate 301 is placed in a heating furnace at 150 ° C. for 5 minutes.
The conductive paste was cured by holding for a minute.

Next, encapsulation of this solar cell was performed in the same procedure as in Example 1 to produce ten solar cell modules.

The solar cell module manufactured as described above has the following characteristics for each sample. 11 to No. Numbering was performed up to 20, and the initial characteristics of each manufactured solar cell module were measured. First, a solar spectrum of AM1.5 was irradiated at an intensity of 100 mW / cm ² using a simulator, and the current-voltage characteristics of the solar cell were measured. This characteristic result was normalized by the opening area of the solar cell to obtain an average conversion efficiency of 6.5%. Subsequently, the durability characteristics of these samples were evaluated in the same manner as in the fifth embodiment. First, the sample was put into a thermo-hygrostat capable of controlling the temperature and humidity, and a cycle test in which the temperature was changed from −40 ° C. to + 85 ° C. (relative humidity 85%) was repeated 10 times. Next, the solar cell characteristics of the sample after the test were measured using a simulator in the same manner as in the case of the initial characteristics.
Met. When the shunt resistance was measured, it was about 30
%, And current leakage was observed.

Therefore, when the first embodiment and the comparative example are compared and examined, it can be seen that the solar cell of the present invention has improved appearance and durability as compared with the solar cell of the comparative example.

Embodiment 2 FIG. 2 shows a second embodiment of the present invention. The solar cell 200 of this example was manufactured as follows. After a lower electrode 202 was formed on the back surface of the metal silicon substrate 201, an n-type polysilicon 203 was formed on the substrate 201, and a p-type microcrystalline silicon was formed by a plasma CVD method as in the first embodiment.

Thereafter, in the same manner as in Example 1, the steps up to the formation of the single-crystal silicon upper electrode of the antireflection layer 206 made of ITO were performed in the same manner as in Example 1. Next, the current collecting electrode 207 was printed using a screen printer (not shown) and cured in the same manner as in Example 1. Next, a tin-plated copper foil bus bar (not shown) was attached. Further, a coating layer 208 was deposited using an acrylic anion electrodeposition paint. Then, it adhered to the back surface of the solar cell 200. Ten solar cells were produced in the same manner. Ten of these were connected in series to produce a serialized large intestine battery as shown in FIG.

Next, encapsulation of this serialized solar cell was performed in the same manner as in Example 1, ten solar cell modules were manufactured, and the sample was designated as No. 1. 21 to No. 21. 30. Example 1 shows the initial characteristics of the obtained solar cell module.
, And the durability characteristics of these samples were evaluated in the same manner as in the comparative example. The conversion efficiency of the sample after the test was 96% of the initial conversion efficiency, and no significant deterioration occurred. Also, when the shunt resistance was measured, there was no significant deterioration with a decrease of about 15%.

Thus, it can be seen that this embodiment also has good durability.

(Embodiment 3) FIG. 5 shows a third embodiment. The solar cell 500 according to this example was manufactured as follows. After forming the lower electrode 1002 on the back surface of the n-type silicon substrate 503, a p-type silicon layer 505 was formed on the substrate 503 by a thermal diffusion method. After that, the anti-reflection layer 506 made of SiO ₂
Was formed by a sputtering method. Further, the current collecting electrode 507 is printed by a screen printer (not shown) in the same manner as in the first embodiment.
Cure at 0 ° C. In this case, the collecting electrode 507 penetrated the antireflection layer 506 and directly contacted the p layer 505. Next, a tin-plated copper foil bus bar (not shown) was attached. Further, a coating layer 508 was deposited using an acrylic cationic electrodeposition paint.

Next, encapsulation of this solar cell was performed in the same manner as in Example 1, and the solar cell module was
No. was prepared and the sample was No. 31 to No. 31 40. In the obtained solar cell module, the color tone of the current collecting electrode 507 and the antireflection layer 506 were almost the same, and the appearance was improved.

Example 4 The solar cell according to this example has the same configuration as the solar cell 100 according to Example 1 shown in FIG. 1, but was manufactured by a different method as described below. Current collecting electrode 1 in the same manner as in Example 1.
07 and a bus bar 108 (not shown) were formed. further,
The coating layer 108 was deposited using an acrylic anion electrodeposition paint. Thereafter, an epoxy resin containing a blue pigment is printed on the solar cell 100 using a screen printing plate having the same pattern as the current collecting electrode 107 and the bus bar, and the coating layer 10 is formed.
8 was formed.

Next, encapsulation of this serialized solar cell was performed in the same manner as in Example 1, ten solar cell modules were manufactured, and the sample was designated as No. 1. No. 41 to No. 41. 50. The initial characteristics of the obtained solar cell module were measured in the same manner as in Example 5. Then, the durability characteristics of these samples were evaluated in the same manner as the comparative example. The conversion efficiency of the sample after the test was 97% of the initial conversion efficiency, and no remarkable deterioration occurred. When the shunt resistance was measured, there was no remarkable deterioration with a decrease of about 12%.

As described above, it can be seen that the durability of the solar cell is also improved in the case of this embodiment.

[0037]

According to the present invention, a solar cell having high durability can be obtained by forming a skin covering layer covering a current collecting electrode, and a solar cell with improved appearance can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a schematic sectional view illustrating a configuration of a solar cell according to a second embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a configuration of a conventional solar cell.

FIG. 4 is a cross-sectional view showing an apparatus of an electrodeposition method.

FIG. 5 is a schematic sectional view showing a configuration of a solar cell according to a third embodiment of the present invention.

[Explanation of symbols]

100, 200, 300, 500 solar cells, 101,
201, 301 substrate, 102, 202, 302 lower electrode, 103, 203, 303 n-layer, 104, 20
4, 304 i-layer, 105, 205, 305 p-layer, 1
06, 206, 306 anti-reflection layer, 107, 207,
307 collecting electrode, 108, 208, 308 coating layer,
401 electrodeposition tank, 402 electrodeposition liquid, 403 counter electrode,
404 board, 405 bus bar, 406 power supply, 40
7 conductor, 502 lower electrode, 503 n-type silicon substrate, 505 p-type silicon layer, 506 anti-reflection layer, 5
07 current collecting electrode, 508 coating layer.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 31/04 H01L 31/042 E04D 13/18

Claims (2)

(57) [Claims] 1. A solar cell comprising a current collecting electrode provided on a solar cell element having an antireflection film, wherein the current collecting electrode comprises:
Including pigments that are similar in color to the color of the solar cell element
Solar cell characterized by being covered with coating layer made of non-organic or inorganic. 2. A method according to claim wherein the coating layer is characterized by Tei Rukoto formed using electrodeposition method or a screen printing method
2. The solar cell according to 1 .