JP2003101048A - Method for manufacturing photovoltaic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a photovoltaic device, wherein high yield and high conversion characteristics are realized. SOLUTION: An i-type amorphous silicon layer 2 and a p-type amorphous silicon layer 3 are formed on a substrate 1 composed of n-type silicon (a), and an nip junction is obtained (b). A transparent conducting film 4 is formed on the p-type amorphous silicon layer 3 (c). Masking is performed to the central effective part of the transparent conducting film 4 by using mask member 7, and only the end portion of the transparent conducting film 4 is subjected to oxygen plasma treatment and made high resistance (d). As a result, leakage between the substrate 1 and the transparent conducting film 4 is restrained. Finally, a comb-shaped collecting electrode 5 and a back electrode 6 are formed (e), and a photovoltaic device is manufactured.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a photovoltaic device, and more particularly to a method for forming a transparent conductive film.

[0002]

2. Description of the Related Art HIT (Heterojunction with Intrinsi
A c thin-layer) photovoltaic device is formed by sequentially forming an amorphous semiconductor layer, a transparent conductive film, and a collecting electrode on a silicon wafer, and mainly emits light incident from the side opposite to the silicon wafer. It is the photovoltaic device used. This HIT type photovoltaic device can be manufactured at a lower temperature than the crystalline photovoltaic device, and is expected as a photovoltaic device that can achieve cost reduction and high conversion efficiency.

In order to obtain a high conversion output with a single silicon wafer, it is important to increase the photoelectric conversion area, and for that reason, the formation area of the transparent conductive film is made as large as possible.

[0004]

When it is attempted to increase the formation area of the transparent conductive film as described above, when the transparent conductive film is formed on the amorphous semiconductor layer formed on the silicon wafer, the amorphous conductive film is formed. The transparent conductive film may be formed even in a portion where the semiconductor layer is not formed. In such cases,
There is a problem in that a leak occurs between the excessively formed transparent conductive film and the silicon wafer, which causes deterioration of photoelectric conversion characteristics.

The present invention has been made in view of such circumstances, and by performing the resistance increasing treatment on the end portion of the formed transparent conductive film, it is possible to prevent the leakage as described above, and to obtain a high yield and a high conversion. It is an object of the present invention to provide a method for manufacturing a photovoltaic device that can realize the characteristics.

[0006]

A method for manufacturing a photovoltaic device according to a first aspect of the present invention comprises a semiconductor layer, a transparent conductive film and a collector electrode formed in this order on a substrate, and mainly from the collector electrode side. In a method of manufacturing a photovoltaic device that emits light,
The semiconductor layer and the transparent conductive film are formed on the substrate, and an end portion of the formed transparent conductive film is selectively subjected to a resistance increasing treatment.

In the first invention, after the semiconductor layer and the transparent conductive film are formed on the substrate, the effective portion at the center of the transparent conductive film is masked to selectively increase the resistance only at the end portions. Therefore, even if an extra transparent conductive film is formed beyond the formation region of the semiconductor layer, that portion has high resistance,
Leakage with the substrate does not occur.

A method of manufacturing a photovoltaic device according to a second aspect of the invention is characterized in that, in the first aspect of the invention, the resistance increasing treatment is an oxygen plasma treatment.

In the second aspect of the invention, only the end portions of the transparent conductive film are selectively made high in resistance by the oxygen plasma treatment.
Therefore, the resistance increasing process can be easily performed.

The method for manufacturing a photovoltaic device according to a third aspect of the present invention is characterized in that, in the first aspect, the resistance increasing treatment is an energy beam irradiation treatment in an oxygen atmosphere.

According to the third aspect of the invention, only the end portions of the transparent conductive film are selectively made high in resistance by irradiation with an energy beam in an oxygen atmosphere. Therefore, the resistance increasing process can be easily performed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. (First Embodiment) FIG. 1 is a process diagram of a method for manufacturing a photovoltaic device according to the first embodiment. First, about 1Ω ・ c
An n-type (100) silicon wafer having a thickness of m and a thickness of 300 μm is normally washed to remove impurities and prepare a substrate 1 (FIG. 1A).

Next, an i-type amorphous silicon layer 2 and a p-type amorphous silicon layer 3 are formed in this order on one surface of the substrate 1 by a plasma CVD method (FIG. 1 (b)). . Specifically, a known RF plasma CVD apparatus (13.56
MHz), substrate temperature: 100 to 250 ° C., reaction pressure: 0.2 to 0.6 Torr, RF power: 10 to 1
The film thickness of each of the i-type amorphous silicon layer 2 and the p-type amorphous silicon layer 3 was set to 50 Å or less under the condition of 00 W / cm ² .

Next, a transparent conductive film 4 is formed on the p-type amorphous silicon layer 3 by the sputtering method (FIG. 1 (c)).
Specifically, using a known magnetron sputtering apparatus, the substrate temperature: 250 ° C. or less, the gas flow rate: Ar is 200.
O ₂ at 50 sccm or less, power: 0.
An ITO film having a film thickness of about 1000Å was formed under the condition of 5 to 3 kW. Here, in the end portion of the formed transparent conductive film 4, a minute leak occurs due to a portion outside the base layer (p-type amorphous silicon layer 3 / i-type amorphous silicon layer 2), and photoelectric conversion is performed. It causes deterioration of conversion characteristics.

Therefore, in the first embodiment, the resistance increasing treatment is selectively applied only to the end portion (hatched portion) of the transparent conductive film 4 by the oxygen plasma treatment (FIG. 1).
(D)). Specifically, using the RF plasma CVD device (13.56 MHz) described above, the substrate temperature: 200 ° C.,
O ₂ : 200 sccm, pressure: 50 Pa, power: 30
Oxygen plasma is generated under the condition of 0 mW / cm ² and the central effective portion is masked with a metal mask material 7 such as SUS or Al so that oxygen is selectively present only at the end portions of the transparent conductive film 4. Introduced to increase the resistance.

FIG. 2 shows a known RF plasma CV for an ITO film (thickness: 1000Å) formed on a glass substrate.
9 is a graph showing the relationship between plasma processing time and sheet resistance when oxygen plasma processing by method D is performed. Figure 2
The sheet resistance of No. 2 is represented by a normalized value with respect to the sheet resistance when the oxygen plasma treatment is not performed. From the results of FIG. 2, it can be confirmed that the sheet resistance increases as the plasma processing time increases, and the transparent conductive film 4 (ITO film) is obtained by the oxygen plasma processing in the first embodiment.
It can be seen that the end portion of can be made sufficiently high in resistance.

Finally, a comb-shaped collector electrode 5 is formed on the transparent conductive film 4.
Further, the bus bar electrode is formed as a plus side electrode, and the back surface electrode 6 is formed as a minus side electrode on the back surface of the substrate 1 (FIG. 1E) to manufacture the photovoltaic device.
Specifically, an Ag paste obtained by kneading Ag fine powder into an epoxy resin has a thickness of about 10 to 30 by a screen printing method.
After being applied on the transparent conductive film 4 with a width of 100 μm and a width of 100 to 500 μm, it is baked and cured at 150 to 250 ° C. to form a comb-shaped collector electrode 5 having a plurality of parallel branches and a current flowing through the collector electrode 5. And a bus bar electrode for assembling are formed, and Al is vapor-deposited on the back surface of the substrate 1 to form the back surface electrode 6.

In the first embodiment, after forming the transparent conductive film 4, the formation region of the underlying amorphous semiconductor layer (p-type amorphous silicon layer 3 / i-type amorphous silicon layer 2) is formed. Surrounding 1
mm inside is masked and the above conditions (substrate temperature:
At 200 ° C., O ₂ : 200 sccm, pressure: 50 Pa, power: 300 mW / cm ² ), a plurality of types of photovoltaic devices in which the plasma processing time was changed were manufactured. The product of the open circuit voltage Voc and the fill factor FF was measured for these manufactured photovoltaic devices. FIG. 3 is a graph showing the relationship between the oxygen plasma treatment time and Voc × FF. V in FIG.
The value of oc × FF is normalized by the value of Voc × FF when the oxygen plasma treatment is not performed.

From the results shown in FIG. 3, it can be seen that the value of Voc × FF is improved as the oxygen plasma treatment time is increased. This is because the resistance of the edge of the ITO film was selectively increased to suppress Voc × FF due to the leakage of the edge. Under the above plasma conditions, the processing time is 1
It can be seen that the value of Voc × FF does not change when the time is 20 seconds or more, but it goes without saying that this characteristic (Voc × FF) is greatly affected by the plasma processing conditions and the ITO film quality.

Even when plasma is generated only in the vicinity of the substrate by using the aperture type discharge electrodes corresponding to the end regions, the mask material is used so that the mask material does not have to be used during the plasma processing. It was confirmed that the same effect as was obtained.

(Second Embodiment) FIG. 4 is a process diagram of a method for manufacturing a photovoltaic device according to a second embodiment. First
Similar to the embodiment, a substrate 1 made of an n-type (100) silicon wafer is prepared (FIG. 4A), and the i-type amorphous silicon layer 2 and the p-type non-silicon layer 2 are formed on one surface of the substrate 1. The crystalline silicon layer 3 is formed in this order (FIG. 4B), and the transparent conductive film 4 is formed on the p-type amorphous silicon layer 3 (FIG. 4).
(C)).

Next, by the energy beam irradiation in the oxygen atmosphere, only the end portion (hatched portion) of the transparent conductive film 4 is selectively subjected to the resistance increasing treatment (FIG. 4).
(D)). Specifically, the central effective part is SUS, Al
Around the region where the amorphous semiconductor layer is formed at the end of the transparent conductive film 4 formed by masking with a metal mask material 7 such as
Only the outer part including mm was irradiated with a laser beam by an excimer laser in an oxygen atmosphere to increase the resistance of the irradiation region.

FIG. 5 shows the relationship between the laser power and the sheet resistance when an ITO film (thickness: 1000Å) formed on a glass substrate is laser-treated by an excimer laser beam in an oxygen atmosphere. It is a graph. Figure 5
The sheet resistance of is represented by a standardized value with respect to the sheet resistance when the laser processing is not performed. From the result of FIG. 5, it can be confirmed that the sheet resistance increases as the laser power increases, and the edge of the transparent conductive film 4 (ITO film) is sufficiently increased in resistance by the laser beam irradiation in the second embodiment. I see what I can do.

Finally, as in the first embodiment, the comb-shaped collector electrode 5, the bus bar electrode and the back surface electrode 6 are formed (FIG. 4E), and the photovoltaic device is manufactured.

In the second embodiment, after forming the transparent conductive film 4, the formation region of the underlying amorphous semiconductor layer (p-type amorphous silicon layer 3 / i-type amorphous silicon layer 2) is Surrounding 1
mm was masked, and an excimer laser beam was irradiated in an oxygen atmosphere to selectively introduce oxygen into the irradiation portion to manufacture a plurality of types of photovoltaic devices in which the laser power was changed. The product of the open circuit voltage Voc and the fill factor FF was measured for these manufactured photovoltaic devices. Figure 6
4 is a graph showing the relationship between laser power and Voc × FF. The value of Voc × FF in FIG.
It is standardized by the value of Voc × FF when J / cm ² .

From the result of FIG. 6, the laser power is 0.25.
It can be seen that the value of Voc × FF becomes the largest when J / cm ² , and the optimum laser power exists. When the laser power becomes too strong, the underlying amorphous semiconductor layer is microcrystallized and becomes a new leak component.

In place of the excimer laser beam,
It was confirmed that the same effect can be obtained by irradiating with another energy beam or by performing treatment with spot-shaped plasma.

(Third Embodiment) A plurality of substrates 1 each having an i-type amorphous silicon layer 2 / p-type amorphous silicon layer 3 and a transparent conductive film 4 formed thereon are stacked, and a stack of the stacked substrates is stacked. By performing the oxygen plasma treatment according to the first embodiment or the excimer laser beam irradiation treatment according to the second embodiment in a state where the front and back surfaces are covered with a fixing jig using a dummy wafer, The end portion of the transparent conductive film 4 can have a high resistance. In the third embodiment, since a plurality of wafers can be processed at one time, the productivity is extremely high.

In addition to the oxygen plasma treatment and the energy beam irradiation treatment, dipping in an HCl solution or HC
The resistance of the end portion of the transparent conductive film 4 can be increased by the plasma treatment. Although the case where amorphous silicon is used as the semiconductor layer has been described, the same effect can be obtained even if the semiconductor layer is made of crystalline silicon. Furthermore, the transparent conductive film 4
Although the ITO film is used as the above, it goes without saying that a ZnO film may be used. . Further, when the i-type amorphous silicon, the n-type amorphous silicon, the transparent conductive film, and the collector electrode are formed on the back surface of the substrate, the present invention can be applied to the back surface side.

[0030]

As described above, according to the present invention, after the semiconductor layer and the transparent conductive film are formed on the substrate, the effective portion at the center of the transparent conductive film is masked to selectively increase the resistance only at the end portions. By doing so, leakage between the substrate and the extra transparent conductive film can be prevented, and high yield and high photoelectric conversion characteristics can be realized.

Further, since the end portions of the transparent conductive film are made to have a high resistance by the oxygen plasma treatment or the energy beam irradiation treatment in an oxygen atmosphere, the high resistance treatment can be easily performed.

[Brief description of drawings]

FIG. 1 is a process drawing of a method for manufacturing a photovoltaic device according to a first embodiment.

FIG. 2 is a graph showing the relationship between oxygen plasma treatment time and sheet resistance in the first embodiment.

FIG. 3 is a graph showing the relationship between the oxygen plasma processing time and Voc × FF in the first embodiment.

FIG. 4 is a process drawing of the method for manufacturing the photovoltaic device according to the second embodiment.

FIG. 5 is a graph showing the relationship between laser power and sheet resistance in the second embodiment.

FIG. 6 shows laser power and Voc × in the second embodiment.
It is a graph which shows the relationship with FF.

[Explanation of symbols]

1 substrate 2 i-type a-Si layer 3 p-type a-Si layer 4 Transparent conductive film 5 collecting electrodes 6 Back electrode 7 Mask material

Claims (3)

[Claims] 1. A method for manufacturing a photovoltaic device in which a semiconductor layer, a transparent conductive film, and a collecting electrode are formed in this order on a substrate, and in the method for manufacturing a photovoltaic device in which light is mainly incident from the collecting electrode side, A method for manufacturing a photovoltaic device, comprising forming the semiconductor layer and the transparent conductive film, and selectively subjecting an end portion of the formed transparent conductive film to a resistance increasing treatment. 2. The method for manufacturing a photovoltaic device according to claim 1, wherein the resistance increasing treatment is an oxygen plasma treatment. 3. The method for manufacturing a photovoltaic device according to claim 1, wherein the resistance increasing treatment is an energy beam irradiation treatment in an oxygen atmosphere.