JPH053333A - Method for repairing solar battery - Google Patents

Abstract

PURPOSE:To improve the reliability of a solar battery by impressing a reverse bias upon the solar battery under a condition where the temperature is equal to or higher than the glass transition temperature of the binder used for conductive paste and the relative humidity is >=60%. CONSTITUTION:This solar battery repairing method which remedies the fault of a solar battery, the electrode of which is formed of conductive paste, by impressing a reverse bias impresses the reverse bias upon the solar battery under a condition where the temperature is higher than the glass transition temperature of the binder used for the conductive paste and relative humidity is >=60%. This method is suitable for a solar battery which is constituted by successively forming an amorphous silicon layer having pin structures 3, 4, and 5, transparent electrode 6, grid electrodes 7 made of conductive paste, and resin film on a substrate 1. Therefore, the fault of the solar battery caused by short circuit or shunt can be repaired and the production yield of the solar battery can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a highly reliable solar cell. More particularly, the present invention relates to a method for preventing initial characteristics of a solar cell and deterioration during use by simply repairing a short circuit or a shunt that occurs in the manufacturing process of the solar cell.

[0002]

2. Description of the Related Art Solar cells, which are photoelectric conversion elements that convert sunlight into electric energy, have been widely applied as a small power source for consumer use 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. A solar cell is a technology that uses the photovoltaic power of a semiconductor pn junction.
When a semiconductor such as silicon absorbs sunlight, photo carriers of electrons and holes are generated. The optical carrier drifts due to the internal electric field of the pn junction and is taken out to the outside. Such a solar cell is manufactured by using a semiconductor process. Specifically, a p-type or n-type valence electron controlled silicon single crystal is produced by a crystal growth method such as the CZ method, and the single crystal is sliced to obtain about 300
Make a silicon wafer with a thickness of μm. Further, a pn junction is formed in the wafer by forming layers of different conductivity types by an appropriate means such as diffusion of a valence electron control agent and ion implantation so that the wafer has a conductivity type opposite to that of the wafer. create.

From the viewpoint of reliability and conversion efficiency,
Currently, single crystal silicon is mainly used for practically used solar cells. However, since the solar cell is manufactured by using the semiconductor process as described above, its production cost is high.

The single crystal silicon solar cell also has the following drawbacks. Since single crystal silicon is an indirect transition, it has a small light absorption coefficient, and a thickness of at least 50 μm or more is necessary to obtain the required amount of light. This is disadvantageous in terms of weight saving.

The band gap suitable for a solar cell is 1.5 eV, but in the case of single crystal silicon it is about 1.1 eV. Therefore, there is a drawback that the short wavelength component of sunlight cannot be effectively used.

If polycrystalline silicon is used instead of single crystal silicon, the production cost will be reduced, but since polycrystalline silicon is also an indirect transition, the problem of solar cell thickness remains. Further, polycrystalline silicon has grain boundaries and other problems.

Further, a solar cell using crystalline silicon cannot produce a large amount of electric power by itself because it is difficult to manufacture a large-area wafer. Therefore, a wiring technique for serializing or parallelizing the unit elements is required. Also, when used outdoors, expensive packaging is required to protect the solar cells from mechanical damage caused by various weather conditions.

As described above, the conventional solar cell has a problem that the production cost per unit power generation amount becomes higher than that of the existing power generation method. Therefore, in advancing the practical use of solar cells for electric power, cost reduction and large area are important technical issues. In order to solve the above problems, various investigations are currently being made, and materials such as low cost materials and low conversion efficiency materials are being sought. Such materials include amorphous silicon,
Tetrahedral amorphous semiconductor such as amorphous silicon germanium or amorphous silicon carbide, or CdS, Cu ₂
II-VI group compound semiconductors such as S and GaAs, GaA
Examples thereof include III-V group compound semiconductors such as 1As. In particular, a thin-film solar cell using an amorphous semiconductor for the photovoltaic layer is capable of forming a film having a large area as compared with a single-crystal solar cell, has a small film thickness, and can be used as an arbitrary substrate material. It has advantages such as being able to be deposited and is considered promising.

However, when producing a large-area film,
Pinholes and defects occur in the manufacturing process, and problems remain in terms of improving reliability.

As a means for solving such a problem, a method of repairing a solar cell after film formation is used. As a method for repairing defects in a solar cell, US Pat.
In 18, there is disclosed a method of burning off a short circuit portion by applying a reverse bias to the solar cell. According to the method disclosed above, in a solar cell using a cermet, which is a mixture of a metal and an insulator, as an electrode, the cermet existing in the short-circuit portion is burned out by reverse bias.

Since the above-mentioned conventional example discloses only the case where cermet is used as the electrode metal, the same effect cannot be obtained in the solar cells having other configurations. For example, a method of manufacturing a solar cell in which a grid electrode made of at least one amorphous silicon having a pin structure, a transparent electrode, and a conductive paste is sequentially provided on a substrate, and then a resin film is laminated on the grid electrode. In the conventional repair method, the printed conductive paste is in the pinhole due to the moisture that has penetrated through the encapsulation resin when the solar cell is used and the electromotive force generated by light. There was a problem that the short circuit occurred gradually after migrating to.

[0012]

SUMMARY OF THE INVENTION The present invention overcomes the problems of the conventional reverse bias application repair method as described above, repairs defects in solar cells due to shorts and shunts, and improves product yield. To provide a method.

Still another object of the present invention is to provide a manufacturing method for improving the reliability of solar cell characteristics in actual use.

[0014]

In order to achieve the above object, the present invention provides a method for repairing defects by applying a reverse bias to a solar cell in which an electrode is formed of a conductive paste. A reverse bias is applied to the solar cell at a temperature not lower than the glass transition point of the binder used in the conductive paste and at a relative humidity of 60% or higher. Further, such a method is characterized in that at least one amorphous silicon having a pin structure, a transparent electrode, a grid electrode made of a conductive paste, and a resin film are sequentially formed on a substrate. It is preferably used for solar cells. Further, the conductive paste is Ag,
A film containing at least one metal of Pd and Cu as a filler, the binder being polyester, urethane, epoxy, or polyimide, and the resin film containing at least a copolymer of ethylene and vinyl acetate, or a fluorinated film. It is preferably used for a solar cell which is one of ethylene.

In the experiment of the inventor of the present invention, in the solar cell having the structure in which the electrodes are formed by the conductive paste, the solar cell is long even if the short circuit and the shunt are burned out and repaired by the conventional reverse bias application method. It turns out that a shunt occurs again when used for a period of time. A detailed experiment conducted by the present inventor showed that the cause was a short circuit in which the metal of the conductive paste was repaired due to the electromotive force generated by moisture and light that had penetrated through the encapsulation resin under high temperature and high humidity. It was also found that the phenomenon of migration to the shunt portion occurs.

The present inventor has conducted further studies and found that the above-mentioned migration can be prevented by improving the method of reverse bias application repair and the reliability of the solar cell is improved.

The present invention has been completed based on the above basic knowledge.

The present invention will be described in more detail below, but the present invention is not limited by the following specific description.

The repair method of the present invention uses p of amorphous silicon.
It can be applied to an in-type solar cell having a structure in which a grid electrode or a lower electrode is screen-printed with a conductive paste. Further, the method of the present invention is preferably used when the electrodes are formed by screen printing even in the conventional solar cells such as single crystal silicon and polycrystalline silicon. Further, in a solar cell of a compound semiconductor such as CdS, the present invention is used because the electrodes are usually formed by screen printing. Structural examples of these solar cells are shown in FIGS. 5A to 5D.

FIG. 5A shows a pin type solar cell made of amorphous silicon. In the figure, 51 is a support, 52 is a lower electrode, 53 is an n-type semiconductor layer, 54 is an i-type semiconductor layer, 55 is a p-type semiconductor layer, 56 is a transparent electrode, and 57 is a grid electrode, which is a solar cell formed by depositing in this order. The present solar cell is premised on that light is incident from the transparent electrode 56 side.

FIG. 5B shows a solar cell using a glass substrate, in which the substrate 51 is made of glass, and light is emitted from above. In this case, the lower electrode 52 is made of a conductive paste.

FIG. 5C shows a solar cell using thin-film polycrystalline silicon in which the n-type semiconductor layer 53 is formed of a thin-film polycrystal.

FIG. 5D shows a solar cell using crystalline silicon or polycrystalline silicon. In this case, the transparent electrode 5 is used.
6 does not have to be conductive, for example, SiO, SiO
₂ , Ta ₂ O ₅ , Si ₃ N _4, etc. are used.

The grid electrode 57 used in each solar cell is provided as a current collector for extracting the current generated in the semiconductor layer to an external circuit, but a sufficient amount of light incident on the semiconductor layer is secured. So that its shape and area are appropriately designed.

For example, it is desirable that the shape thereof be uniformly spread over the light receiving surface of the photovoltaic element, and that the area of the light receiving area is preferably 15% or less, more preferably 10% or less.

The sheet resistance value is preferably 50 Ω / □ or less, more preferably 10 Ω / □ or less. As a method for wiring a grid electrode having such characteristics to a large area solar cell, a vacuum process such as vapor deposition or sputtering, as well as a screen printing method using plating or a conductive paste is used. A screen printing method is preferably used to obtain a large area pattern. As the electrode material, Ag, Cr, Ni, Al, Au,
Examples include metals such as Ti, Pt, Cu, Mo, W, and alloys thereof. These thin films can be laminated and used. In the case of the screen printing method using a conductive paste, the conductive paste is prepared by dissolving the metal fine particles and the polymer binder in a solvent. The polymer may be crosslinked or non-crosslinked as desired. Further, the polymer is selected from resins such as epoxy, polyester, polyurethane and polyimide according to the required physical properties such as adhesive strength and flexibility.

Next, FIG. 1A shows an example of a circuit suitable for repairing the solar cell of the present invention. In FIG. 1, the solar cell has the structure shown in FIG. 5A, 8 is a conducting wire for connecting a circuit, 9 is a voltage source, 10 is an ammeter, and 11 is a voltmeter. Since the voltage source 9 is for applying a reverse bias to the solar cell, a voltage source capable of generating a stable DC voltage is preferable. The range of voltage generated is from 0 V to a voltage at which breakdown of the solar cell does not occur, for example, 30
It suffices if a voltage of V order can be generated. The voltmeter 11 reads the voltage generated by the voltage source 9, and the resolution may be about 0.1V. The ammeter 10 reads the leak current of the solar cell and requires a range according to the area of the solar cell. Here, FIG. 1B is a cross-sectional view schematically showing a short circuit portion of the solar cell.

As a method of applying a reverse bias, a voltage is gradually applied from 0 V to the p-type semiconductor layer 5 of the solar cell, and a leak current is recorded at the same time. The voltage is increased at a speed of about 1V / min and the voltage application is stopped at about 10V.

By the way, these conditions cannot be generally determined depending on the structure of the solar cell and the size of the short circuit.
In some cases, even if the above reverse bias is applied, there is almost no effect.

The present inventors have conducted the following experiments focusing on the environmental conditions of the solar cell when a reverse bias is applied. [Experiment]
First, the shunt resistance and solar cell characteristics are almost the same as in FIG.
Eighteen solar cells having the structure shown in (A) were prepared. The voltage-current characteristics of these solar cells in the dark state were measured, and the shunt resistance was calculated from the slope near the origin of the voltage-current curve. Then, using a solar simulator, the light of the sunlight spectrum of AM 1.5 was 100 mW / The initial characteristics of the solar cell were measured by irradiating with an intensity of cm ² and determining the voltage-current characteristics.

Next, one of the solar cells was placed in an oven and a reverse bias was applied under the conditions of a temperature of 40 ° C. and a relative humidity of 50%. Voltage is 1V / mi from 0V to 15V
It was applied at a speed of n. Thereafter, the solar cell was taken out of the oven, returned to room temperature, and the shunt resistance and the solar cell characteristics were measured by the methods described above. Next, the ratio of the shunt resistance before repair and the shunt resistance after repair was determined and was taken as Rsh. Next, the same experiment was repeated with another solar cell. At this time, the temperature and the relative humidity were changed to 90 ° C. and 80%, respectively. The results are shown in Fig. 2. Also,
FIG. 3A shows the voltage-current characteristics in the dark state before and after repair of the solar cell repaired at a temperature of 90 ° C. and a relative humidity of 80%. Similarly, FIG. 3 (B) shows the voltage-current characteristics before and after repair in the light irradiation state. As can be seen from these results, it was found that the effect was remarkable when the temperature when the reverse bias was applied was higher than 60 ° C., and the effect was produced when the humidity was 60% or more.

The present inventor has considered the reason for this as follows. That is, the moisture permeability of the binder portion is improved by heating the solar cell above the Tg of the binder of the conductive paste, and the moisture enters through the binder by increasing the relative humidity around the solar cell. When reverse bias is applied in such a state, the silver in the short-circuited portion migrates to the grid electrode side and is removed. In addition, since the binder polymer softened and melted at a temperature of Tg or higher enters the portion thus removed, and the secondary effect such as the role of the sealant can be expected, the present invention is extremely stable. It is a repair method. Needless to say, a phenomenon in which the short-circuit portion is burned out by Joule heat at the same time due to reverse bias application as is usually considered.

Next, the long-term use characteristics of this solar cell were evaluated as follows.

The temperature is 70 ° C. and the relative humidity is 80% by the above method.
A solar cell repaired by applying a reverse bias and a non-treated solar cell as a comparative example were prepared.

The initial solar cell characteristics were measured, the optimum load was calculated from the open circuit voltage V _OC and the short circuit current I _SC obtained from the voltage-current characteristics, and the load resistance was connected to these solar cells.

Next, a solar cell with a load resistor connected
Placed on a sample table kept at a constant temperature of 70 ° C and a relative humidity of 70%,
The same AM 1.5 light (100 mW / cm ² ) as described above was continuously irradiated, and after a fixed time, the shunt resistance was determined again, and normalized by the initial shunt resistance to determine Rsh. Do this operation 10
Repeated during 0 hours of continuous irradiation. Figure 4 shows the results obtained.
It was shown to. As can be seen from FIG. 4, it was found that the solar cell prepared by using the present invention with respect to the comparative sample was more stable to light.

[0037]

EXAMPLES Example 1 A solar cell having the layer structure shown in FIG. 5A was prepared as follows, and then reverse bias application repair was performed.

First, SUS that has been thoroughly degreased and washed
A 430BA substrate (10 cm square, thickness 1 mm) 51 was placed in a DC sputter device (not shown) to deposit 2000 liters of Cr to form a lower electrode 52. The substrate 51 is taken out, placed in an RF plasma CVD film forming apparatus (not shown), and the base pressure in the film forming chamber is evacuated to a vacuum degree of 10 ⁻⁶ Torr.
SiH ₄ 20sccm, PH ₃ (1% H ₂ diluted) 2sc
cm, H ₂ 200 sccm, and the internal pressure is 1 Torr
The n-type semiconductor layer 53 is maintained at RF power of 100 W.
Was deposited. Then, the base pressure in the film forming chamber was evacuated to a vacuum degree of 10 ^-6 Torr, and then SiH ₄ was added.
50 sccm and H ₂ 100 sccm were introduced, and the pressure was kept at 1.5 Torr. Furthermore, RF power 50W
Was added to deposit the i-type semiconductor layer 54. The base pressure in the film forming chamber was evacuated to a vacuum degree of 10 ^-6 Torr, SiH ₄ 20 sccm, BF ₃ (diluted 1% H ₂ )
40 sccm and H ₂ 600 sccm were introduced, the internal pressure was maintained at 1.2 Torr, the RF power was set to 1.0 kW, and the p-type semiconductor layer 55 was deposited.

Next, after cooling the substrate 1, it was taken out of the film forming chamber, placed in a resistance heating vapor deposition device (not shown), the inside of the device was evacuated to 10 ^-7 Torr or less, and then oxygen gas was introduced. After setting the internal pressure to 0.5 mTorr, an alloy of In and Sn was vapor-deposited by resistance heating, and 700 Å of a transparent conductive film (ITO film) having a function also as an antireflection effect was deposited to form the upper electrode 56. After completion of the vapor deposition, the sample was taken out and a grid having a width of 300 μm and a length of 7 cm was printed at a distance of 1 cm by a screen printer (not shown). At this time, the conductive paste is composed of 40 parts of Ag filler and 60 parts of polyester binder.
Parts (volume ratio) having a composition were used. Binder Tg
Was 60 ° C.

Next, the voltage-current characteristics of the obtained solar cell in the dark state were measured and the shunt resistance was measured to be about 50.
It was 0 Ωcm ² , and it was found that there was a large short circuit or shunt. This solar cell uses a solar simulator to generate 1 light of the AM 1.5 sunlight spectrum.
The initial characteristics of the solar cell were measured by irradiating with an intensity of 00 mW / cm ² and determining the voltage-current characteristics. The initial fill factor (hereinafter referred to as FF) of this solar cell was 0.45.

Next, this solar cell was placed in an oven at a temperature of 65 ° C. and a relative humidity of 70% to reach equilibrium, and then a reverse bias was applied. The voltage was applied from 0 V to 15 V at a rate of 1 V / min. Thereafter, the solar cell was taken out of the oven, returned to room temperature, and the shunt resistance and the solar cell characteristics were measured by the methods described above. Shunt resistance is about 2kΩc
It was increased to m ² . In addition, FF among the solar cell characteristics was improved to 0.60.

Photodegradation characteristics of the solar cell as long-term use characteristics were evaluated as follows.

The optimum load is calculated from the open circuit voltage V _OC and the short circuit current I _SC obtained when the above voltage-current characteristics are obtained,
A load resistor was connected to each sample.

Next, a solar cell connected to a load resistor was placed on a sample table kept at a temperature of 50 ° C. and a relative humidity of 70%, and the same AM1.5 light (100 mW / cm ² ) as described above was continuously applied for 500 hours. After irradiation, the shunt resistance was measured again. The thus obtained shunt resistance after 500 hours was 1.5 kΩcm ² and was found to be stable to light. Example 2 Next, a solar cell having the layer structure shown in FIG. 5B was produced as follows, and subsequently, reverse bias application repair was performed.

A solar cell was manufactured by a method similar to that of Example 1.

First, 705 that was thoroughly degreased and washed.
The 9 glass substrate (10 cm square) 51 was placed in a resistance heating vapor deposition device (not shown), and the inside of the device was evacuated to 10 ^-7 Torr or less, and then oxygen gas was introduced to adjust the internal pressure to 0.5 mTo.
After being set to rr, Sn was vapor-deposited by resistance heating, and a transparent conductive film (SnO ₂ film) was deposited to 8000Å to form the upper electrode 56. The substrate 51 is taken out and RF plasma CVD (not shown)
The film was placed in a film forming apparatus and the inside of the film forming chamber was evacuated to a vacuum degree of 10 ^-6 Torr. SiH ₄ 20 sccm, BF ₃ (1% H ₂ dilution)
40 sccm and H ₂ 600 sccm were introduced, the internal pressure was maintained at 1.2 Torr, the RF power was set to 1.0 kW, and the p-type semiconductor layer 55 was deposited. After that, the film forming chamber was evacuated to a vacuum degree of 10 ^-6 Torr, and SiH ₄ 50 sc
cm, introduced the H ₂ 100sccm, the pressure 1.5To
Hold at rr. Furthermore, the RF power of 50 W is input to the i
The type semiconductor layer 54 was deposited. 10 in the film forming chamber again
^{Evacuated to -6} Torr vacuum, SiH ₄ 20sccm,
PH ₃ (1% H ₂ diluted) ₂ sccm, H ₂ 200 scc
Introducing m, keeping the internal pressure at 1 Torr, RF power at 1
The n-type semiconductor layer 53 was deposited at 00W.

Next, after cooling the substrate 51, it is taken out of the film forming chamber and the lower electrode 52 is removed by a screen printing device (not shown).
Was formed. At this time, the conductive paste used had a composition of Cu filler 70 parts and epoxy binder 30 parts (volume ratio). The Tg of the binder was 90 ° C.

Next, the voltage-current characteristic of the solar cell in the dark state was measured by the same procedure as in Example 1 to measure the shunt resistance, which was about 800 Ωcm ² . The initial characteristics of the solar cell were measured by irradiating the solar cell with light of AM 1.5 sunlight spectrum at an intensity of 100 mW / cm ² using a solar simulator and determining the voltage-current characteristic. The initial fill factor of this solar cell (hereinafter F
(Written as F) was 0.55. Next, this solar cell was placed in an oven and a reverse bias was applied under the conditions of a temperature of 90 ° C. and a relative humidity of 90%. The voltage was applied from 0 V to 10 V at a rate of 0.5 V / min. Thereafter, the solar cell was taken out of the oven, returned to room temperature, and the shunt resistance and the solar cell characteristics were measured by the methods described above. The shunt resistance had increased to about 2.5 kΩcm ² . In addition, FF of the solar cell characteristics was improved to 0.65.

Photodegradation characteristics of this solar cell were evaluated in the same manner as in Example 1.

The shunt resistance after 500 hours is 1.9 kΩ.
It was found to be cm ² and stable to light. Example 3 Next, a solar cell module having the configuration shown in FIG. 6 was produced using the solar cell subjected to the reverse bias application repair by the method shown in Example 1, and the stability during long-term use was evaluated.

A solar cell was manufactured by the same method as in Example 1.

First, in the same manner as in Example 1, 30 10 cm square solar cells having the structure of FIG. At this time, the conductive paste forming the grid electrode 57 is 70 parts of Ag filler and 30 parts of urethane resin binder (volume ratio).
The composition was used. The Tg of the binder was 70 ° C.

Next, these solar cells were placed in an oven and reverse bias was applied under the conditions of a temperature of 75 ° C. and a relative humidity of 80%. Voltage is 1V / mi from 0V to 15V
It was applied at a speed of n. Thereafter, the solar cell was taken out of the oven, returned to room temperature, and the shunt resistance and the solar cell characteristics were measured by the methods described above. The average shunt resistance of 30 sheets was about 1.5 kΩcm ² . The average of 30 FFs of the solar cell characteristics was 0.62.

Next, the grid 67 of these solar cells and the substrate 61 were connected with a tin-plated copper tape for serialization. After that, the encapsulant 68 made of ethylene vinyl acetate resin was encapsulated with a Teflon resin 69 for improving weather resistance.

The photodegradation characteristics of this solar cell were evaluated as follows.

The optimum load is calculated from the open circuit voltage V _OC and the short circuit current I _SC obtained when the above-mentioned voltage-current characteristics are obtained,
A load resistor was connected to each sample.

Next, a solar cell connected to a load resistor was placed on a sample table kept at a temperature of 50 ° C. and a relative humidity of 70%, and the same AM1.5 light (100 mW / cm ² ) as described above was continuously applied for 500 hours. After irradiation, the shunt resistance was measured again as described above. The thus obtained shunt resistance after 500 hours was 1.5 kΩcm ² and was found to be stable to light.

[0058]

According to the present invention, the solar cell characteristics are improved,
Furthermore, a solar cell with little photodegradation and high reliability even after long-term use can be obtained.

[Brief description of drawings]

FIG. 1 (A) is a connection diagram schematically showing a method for repairing a solar cell of the present invention. (B) It is sectional drawing which shows typically the short circuit part of the solar cell of the same figure (A).

FIG. 2 is a graph showing the relationship between shunt resistance and temperature under various conditions of the present invention.

FIG. 3A is a graph showing voltage-current characteristics of a solar cell before and after repair of the present invention in a dark state. (B) is a graph showing voltage-current characteristics of the solar cell before and after repair of the present invention during light irradiation.

FIG. 4 is a graph showing changes with time in actual use of the solar cell before and after repair of the present invention.

FIG. 5 is a schematic diagram showing the configuration of various solar cells to which the solar cell repair method of the present invention is applied. (A) Amorphous silicon solar cell (B) Glass substrate solar cell (C) Thin film polycrystalline silicon solar cell (D) Single crystal or polycrystalline silicon solar cell

FIG. 6 is a cross-sectional view schematically showing a module configuration of a solar cell to which the solar cell repair method of the present invention is applied.

[Explanation of symbols]

1,51,61 substrate 2,52,62 Lower electrode 3,53,63 n-type semiconductor layer 4,54,64 i-type semiconductor layer 5,55,65 p-type semiconductor layer 6,56,66 transparent electrode 7,67 Grid electrode 8 conductors 9 Voltage source 10 ammeter 11 Voltmeter 12 short section 68,69 Resin film

Claims (5)

[Claims] 1. A method of repairing defects by applying a reverse bias to a solar cell in which an electrode is formed of a conductive paste, at a temperature equal to or higher than a glass transition point of a binder used for the conductive paste, A method of repairing a solar cell, which comprises applying a reverse bias to the solar cell at a relative humidity of 60% or more. 2. A solar cell having at least one p on a substrate.
The method for repairing a solar cell according to claim 1, wherein an amorphous silicon having an in structure, a transparent electrode, a grid electrode made of a conductive paste, and a resin film are sequentially formed. 3. The method for repairing a solar cell according to claim 1, wherein the conductive paste contains at least one metal selected from Ag, Pd and Cu as a filler. 4. The method for repairing a solar cell according to claim 1, wherein the binder of the conductive paste is polyester, urethane, epoxy, or polyimide. 5. A film in which the resin film comprises at least a copolymer of ethylene and vinyl acetate, or
5. The method for repairing a solar cell according to claim 1, wherein the method is one of fluorine-containing ethylene.