WO2020184705A1

WO2020184705A1 - Method for manufacturing back contact-type solar cell

Info

Publication number: WO2020184705A1
Application number: PCT/JP2020/011062
Authority: WO
Inventors: 紹太鈴木; マルワンダムリン; 山口　昇; 英夫鈴木
Original assignee: 東洋アルミニウム株式会社
Priority date: 2019-03-13
Filing date: 2020-03-13
Publication date: 2020-09-17
Also published as: JP7264673B2; CN113597682A; JP2020150110A

Abstract

The present invention provides a method for manufacturing a back contact-type solar cell that can be carried out with a smaller number of processes than in conventional manufacturing methods.　The present invention is a method for manufacturing a back contact-type solar cell, wherein the method has, in sequence: a step (A) for partially forming a n⁺ layer (20) by ion injection and activation annealing using a mechanical hard mask on the reverse surface of a crystalline silicon substrate (10); a step (B) for forming a passivation film (40) on both surfaces of the crystalline silicon substrate (10) having the n⁺ layer (20) obtained in step (A); and a step (C) for removing a part or all of the region, of the passivation film (40) formed on the reverse surface side of the crystalline silicon substrate (10), that directly covers the crystalline silicon substrate (10), and forming one or more aluminum electrodes (60B) on the exposed crystalline silicon substrate (50).

Description

Manufacturing method of back contact type solar cell

The present invention relates to a method for manufacturing a back contact type solar cell.

In recent years, as a crystalline solar cell with high conversion efficiency, an n ⁺ diffusion layer and a p ⁺ diffusion layer are provided on the back surface of a crystalline silicon substrate called a back contact type solar cell (IBC: Interdigitated Back Contact), and the surface thereof is covered. The development of cells having a structure in which a back surface electrode is formed is being actively carried out.

In a normal silicon solar cell structure, an electrode on the light receiving surface (main surface) side of the solar cell and an electrode on the back surface side are provided. In this way, when the electrode is formed on the light receiving surface (main surface) side, the amount of incident sunlight is reduced by the area of the electrode because the electrode reflects and absorbs sunlight. On the other hand, in the back contact type solar cell, not only the wiring resistance can be reduced and the power loss can be reduced by consolidating the wiring on the back surface side, but also it is not necessary to provide an electrode on the light receiving surface. It is possible to widen and take in a lot of light.

In such a back contact type solar cell, a concave-convex shape is formed on the surface of the light receiving surface of the crystalline silicon substrate by texture etching or a release resin, a dielectric layer is formed so as to be in contact with the entire surface of the crystalline silicon substrate, and an insulating layer is further formed. At the same time, a solar cell in which the short circuit between the p electrode and the n electrode is reduced by repeating patterning and etching in order to form an n ⁺ layer and a p ⁺ layer on the back surface of the crystalline silicon substrate is disclosed. (For example, Patent Document 1).

However, in the technique of Patent Document 1, it is necessary to repeat patterning and etching in order to form the n ⁺ layer and the p ⁺ layer, which increases the number of manufacturing steps. In addition, there is a high risk that the adhesive due to printing, curing, and peeling of the peeling resin remains, and it takes time to clean the residue. Further, a thin-film deposition method or a sputtering method is used to form the n ⁺ layer and the p ⁺ layer, and such a method also requires a long processing time.

Japanese Unexamined Patent Publication No. 2016-171095

In view of the above circumstances, an object of the present invention is to provide a method for manufacturing a back contact type solar cell, which can be carried out with a smaller number of steps than the conventional manufacturing method.

As a result of intensive research to achieve the above object, the present inventors have reduced the number of steps as compared with the conventional manufacturing method according to the manufacturing method having a specific step using the ion implantation method using a mechanical hard mask. It was found that a back contact type solar cell can be manufactured in Japan. The present inventors have further studied based on such findings and have completed the present invention.

That is, the present invention relates to the following method for manufacturing a back contact type solar cell.
1. 1. A method for manufacturing back-contact solar cells.
Step (A) of partially forming an n ⁺ layer on the back surface of a crystalline silicon substrate by an ion implantation method using a mechanical hard mask and activation annealing.
Of the steps (B) obtained in the step (A) for forming a passivation film on both surfaces of the crystalline silicon substrate having the n ⁺ layer, and the passivation film formed on the back surface side of the crystalline silicon substrate. A step (C) of removing a part or all of the region directly covering the crystalline silicon substrate to form one or more aluminum electrodes on the exposed crystalline silicon substrate.
A method for manufacturing a back-contact type solar cell, which comprises the following in order.
2. 2. After the step (B), a part of the passivation film formed on the back surface side of the crystalline silicon substrate, which covers the crystalline silicon substrate via the n ⁺ layer, was removed and exposed. It has a step (C') of forming one or more silver electrodes in the n ⁺ layer.
Item 2. The production method according to Item 1, wherein the step (C) and the step (C') are in no particular order.
3. 3. Item 2. The production method according to Item 2, wherein a copper electrode or an aluminum alloy electrode is formed in place of the silver electrode in the step (C').
4. The aluminum electrode is formed by firing a coating film of an aluminum paste containing 2 to 20 parts by mass of an organic vehicle and 0.15 to 15 parts by mass of a glass frit with respect to 100 parts by mass of aluminum powder at 650 to 900 ° C. , The production method according to any one of the above items 1 to 3.
5. Item 2. The manufacturing method according to Item 2, wherein the aluminum electrodes and the silver electrodes are formed so as to be alternately arranged on the back surface side of the crystalline silicon substrate.

According to the manufacturing method of the back contact type solar cell of the present invention, it is not necessary to repeat patterning and etching in order to form the n ⁺ layer and the p ⁺ layer, and the back contact type solar cell can be backed up with a smaller number of steps than the conventional manufacturing method. It is possible to manufacture contact type solar cells. Therefore, there is a great advantage in terms of manufacturing cost of the back contact type solar cell. In addition, by providing the n ⁺ layer on the back surface of the crystalline silicon substrate by the ion implantation method using a mechanical hard mask and activation annealing, the effect that leakage current (power loss) can be suppressed as compared with the conventional manufacturing method. Can also be obtained.

It is explanatory drawing of the manufacturing method of the back contact type solar cell of this invention. It is the schematic of the back contact type solar cell of an Example. It is an enlarged view of the schematic diagram of the back contact type solar cell of an Example. It is explanatory drawing of the layer structure in the back contact type solar cell of the comparative example. It is the schematic which shows an example of the ion implantation apparatus applied to the manufacturing method of the back contact type solar cell of this invention.

The method for manufacturing a back contact type solar cell of the present invention is
Step (A) of partially forming an n ⁺ layer on the back surface of a crystalline silicon substrate by an ion implantation method using a mechanical hard mask and activation annealing.
Of the steps (B) obtained in the step (A) for forming a passivation film on both surfaces of the crystalline silicon substrate having the n ⁺ layer, and the passivation film formed on the back surface side of the crystalline silicon substrate. A step (C) of removing a part or all of the region directly covering the crystalline silicon substrate to form one or more aluminum electrodes on the exposed crystalline silicon substrate.
It is characterized by having.

According to the method for producing a back-contact type solar cell of the present invention having the above characteristics, it is not necessary to repeat patterning and etching in order to form the n ⁺ layer and the p ⁺ layer, which is less than that of the conventional manufacturing method. Back contact type solar cells can be manufactured by the number of processes. Therefore, there is a great advantage in terms of manufacturing cost of the back contact type solar cell. In addition, by providing the n ⁺ layer on the back surface of the crystalline silicon substrate by the ion implantation method using a mechanical hard mask and activation annealing, the effect that leakage current (power loss) can be suppressed as compared with the conventional manufacturing method. Can also be obtained.

Hereinafter, the method for manufacturing the back contact type solar cell of the present invention (the manufacturing method of the present invention) will be described step by step with reference to the drawings as examples.

Process (A)
In the step (A), the n ⁺ layer 20 is partially formed on the back surface of the crystalline silicon substrate 10 (FIG. 1 (a)) by an ion implantation method using a mechanical hard mask and activation annealing (FIG. 1 (b)). ). In FIG. 1 (b), 30 is a portion that does not form an n ⁺ layer.

As the crystalline silicon substrate to be used, a known crystalline silicon substrate used for a back contact type solar cell can be widely adopted, and there is no particular limitation. Further, either an n-type silicon semiconductor substrate or a p-type silicon semiconductor substrate may be used, and can be appropriately selected depending on the desired use and specifications of the solar cell. In the present specification, one side of the crystalline silicon substrate is referred to as a main surface (light receiving surface when used as a cell), and the other surface is referred to as a back surface.

Further, the crystalline silicon substrate may be wet-etched with an alkaline solution or the like in advance for the purpose of removing the damaged layer on the cut surface and forming a texture.

The thickness of the crystalline silicon substrate is not particularly limited, but can be, for example, 100 to 250 μm, preferably 150 to 200 μm.

A known technique can be used for the ion implantation method for forming the n ⁺ layer. In the production method of the present invention, an ion implantation method using a mechanical hard mask is particularly used. The mechanical hard mask is used to partially provide the n ⁺ layer on the back surface of the crystalline silicon substrate. Examples of the mechanical hard mask include a mechanical hard mask in which openings having a width of 700 μm and closed portions having a width of 300 μm are alternately arranged. In this case, as shown in FIG. 1B, for example, a mechanical hard mask having a width of 700 μm. The n ⁺ layers 20 are formed in a pattern with an interval of 30 of 300 μm. A known mechanical hard mask can be used, and examples of the material include carbon-based, silicon-based, copper-based, and quartz-based.

In the ion implantation method, for example, a technique of using PH ₃ (phosphine) as a raw material to generate plasma, ionize it, and then irradiate it as an ion beam onto a crystalline silicon substrate can be used. At this time, a mechanical hard mask is used to separate the part to be irradiated with the ion beam and the part not to be irradiated with the ion beam. As the ion implantation device for carrying out the ion implantation method, a known mass-separation type ion implantation device or non-mass separation type ion implantation device can be used.

FIG. 5 shows a schematic view of a non-mass separation type ion implanter. The outline is as follows.

The ion implantation apparatus 1000 shown in FIG. 5 includes a vacuum chamber 1001 (lower vacuum chamber), a vacuum chamber 1002 (upper vacuum chamber), an insulating member 1003, a stage 1004, and a gas supply source 1005. The ion implantation device 1000 further includes an RF introduction coil 1100, a permanent magnet 1101, an RF introduction window (quartz window) 1102, an electrode 1200, an electrode 1201, a DC power supply 1300, and an AC power supply 1301.

The vacuum tank 1002 has a smaller diameter than the vacuum tank 1001 and is provided on the vacuum tank 1001 via an insulating member 1003. The vacuum chamber 1001 and the vacuum chamber 1002 can be maintained in a reduced pressure state by a vacuum exhaust means such as a turbo molecular pump. The stage 1004 is provided in the vacuum chamber 1001. The stage 1004 can support the substrate S1. A heating mechanism for heating the substrate S1 may be provided in the stage 1004. The substrate S1 is a crystalline silicon substrate used in the manufacturing method of the present invention. Further, a gas for ion implantation is introduced into the vacuum chamber 1002 by the gas supply source 1005.

The RF introduction coil 1100 is arranged on the RF introduction window 1102 so as to surround the permanent magnet 1101. The shape of the permanent magnet 1101 is ring-shaped. The shape of the RF introduction coil 1100 is a coil shape. The diameter of the RF introduction coil 1100 can be appropriately set according to the size of the substrate S1. When a gas for ion implantation is introduced into the vacuum chamber 1002 and a predetermined power is supplied to the RF introduction coil 1100 from the AC power supply 1301, plasma 1010 is generated in the vacuum chamber 1002 by ICP (Inductively Coupled Plasma) discharge. ..

The electrode 1200 is an electrode having a plurality of openings (for example, a mesh electrode) and is supported by the insulating member 1003. The potential of the electrode 1200 is a floating potential. As a result, stable plasma 1010 is generated in the space surrounded by the vacuum chamber 1002 and the electrode 1200.

Under the electrode 1200, another electrode (for example, a mesh electrode) 1201 having a plurality of openings is arranged. The electrode 1201 faces the substrate S1. A DC power supply 1300 is connected between the electrode 1201 and the RF introduction coil 1100, and a negative potential (acceleration voltage) is applied to the electrode 1201. As a result, the cations in the plasma 1010 are drawn from the plasma 1010 by the electrode 1201.

The extracted positive ions can pass through the mesh-shaped

electrodes

1200 and 1201 and reach the substrate S1. In the ion implanter 1000, the accelerating voltage of positive ions can be set in the range of 1 kV or more and 30 kV or less, for example. Further, a bias power supply capable of adjusting the acceleration voltage may be connected to the stage 1004.

A gas containing an impurity element (n-type impurity element) to be injected into the substrate S1 is introduced into the vacuum chamber 1002. Plasma 1010 is formed in the vacuum chamber 1002 by this gas, and n-type impurity ions in the plasma 1010 are injected into the substrate S1. The n-type impurity ion is, for example, at least one such as P, PX ⁺ , PX ²⁺ , and PX ³⁺ . Here, "X" is either hydrogen or halogen (F, Cl).

In the present embodiment, the means for forming the plasma 1010 is not limited to the ICP method, but may be an electron Cyclotron resonance plasma method, a helicon wave plasma method, or the like. Further, when the n-type impurity ion is implanted into the substrate S1, even if a gas containing hydrogen (for example, PH ₃ , BH _2, etc.) is added to the ion implantation gas from the viewpoint of repairing the lattice defects of the substrate S1. Good.

The conditions for activation annealing are not limited, but the temperature is preferably 600 to 1000 ° C, more preferably 700 to 900 ° C. The atmosphere during annealing preferably has a step of setting the oxygen concentration to 1 to 100%, and more preferably 5 to 50%.

The thickness of the n ⁺ layer is not particularly limited, but is preferably 0.1 to 2 μm, and more preferably 0.3 to 1 μm.

Process (B)
In the step (B), the passivation film 40 is formed on both surfaces (main surface and back surface) of the crystalline silicon substrate having the n ⁺ layer obtained in the step (A) (FIG. 1 (c)). That is, for the portion 20 forming the n ⁺ layer in the step (A) a passivation film is formed on the n ⁺ layer, the existent parts 30 of the n ⁺ layer forms a passivation film on the crystalline silicon substrate.

The passivation film is not particularly limited as long as it has a passivation effect due to a fixed charge in the solar cell of the present invention. Specifically, one or more selected from the group consisting of a silicon nitride film, a silicon oxide film, an aluminum oxide film, an amorphous silicon film, and a microcrystalline silicon film can be exemplified. These films may be a single layer having only one layer, or a plurality of various layers may be laminated.

The method for forming the passivation film is not particularly limited, and for example, various chemical vapor deposition methods or sputtering methods such as a plasma CVD method, a normal pressure CVD method for semiconductors, and an ALD method (atomic layer deposition method) can be exemplified. it can. More specifically, a method of forming a passivation film made of aluminum oxide by the ALD method using trimethylaluminum as a raw material can be mentioned.

The thickness of the passivation film is not particularly limited, but is preferably 10 to 200 nm, more preferably 15 to 50 nm, from the viewpoint of the passivation effect and the workability of the passivation film removing step described later. It is preferable that the surface of the passivation film is further provided with an antireflection film, and the antireflection film can be obtained by forming a silicon nitride film on the surface of the passivation film in an atmosphere of silane gas and ammonia gas, for example, by a plasma CVD method. Be done.

Process (C)
In the step (C), a part or all of the region directly covering the crystalline silicon substrate in the passivation film formed on the back surface side of the crystalline silicon substrate is removed (FIG. 1 (d)) and exposed. One or more aluminum electrodes 60B are formed on the crystalline silicon substrate 50 (FIG. 1 (f)). Here, when the passivation film is removed at a plurality of locations, it is preferable to provide one aluminum electrode for each exposed portion of the crystalline silicon substrate.

The portion from which the passivation film is removed may be a part or the entire region of the passivation film formed on the back surface side of the crystalline silicon substrate, which directly covers the crystalline silicon substrate. The method for removing the passivation film is not particularly limited, and examples thereof include an etching paste and a method of irradiating a laser beam.

As a method for forming the aluminum electrode 60B on the exposed crystalline silicon substrate 50 (FIG. 1 (d)) from which the passivation film has been removed, a known method can be widely adopted, and there is no particular limitation. Specifically, a method of applying aluminum paste 60A to the exposed crystalline silicon substrate 50 by an appropriate method such as coating and firing can be exemplified (FIG. 1 (e) shows a state before firing, and FIG. 1 shows. (F) shows the state after firing.). By such a method, an aluminum-silicon alloy layer 60C and a BSF layer 60D are formed on the crystalline silicon substrate 10 (FIG. 1 (f)). In FIG. 1 (f), the aluminum paste is fired to form an aluminum-silicon alloy layer and a BSF layer on a crystalline silicon substrate, forming an aluminum electrode 60B.

The firing temperature of the aluminum paste is not particularly limited, but is preferably 650 to 900 ° C., for example. The composition of the aluminum paste is not particularly limited, but for example, it is a paste containing 2 to 20 parts by mass of an organic vehicle containing a resin or an organic solvent and 0.15 to 15 parts by mass of a glass frit with respect to 100 parts by mass of aluminum powder. Is preferable.

Further, the aluminum powder may be high-purity aluminum, but may be an aluminum alloy, and an aluminum silicon alloy and an aluminum silicon magnesium alloy are preferably used.

The shape and size of the aluminum electrode are preferably 40 μm to 200 μm in width because it is necessary to cover the exposed crystalline silicon substrate, and the higher the electrode height is, the better in order to lower the resistance value of the electrode. The larger the aspect (width / height) of the printed Al line, the better.

Process (C')
The step (C') is one of the regions of the passivation film formed on the back surface side of the crystalline silicon substrate after the step (B) in which the crystalline silicon substrate is covered with the n ⁺ layer. It is a step of removing a portion and forming one or more silver electrodes 70B on the exposed n ⁺ layer (FIG. 1 (f)), and the steps (C) and (C') are in no particular order. .. Here, when the passivation film is removed at a plurality of locations, it is preferable to provide one silver electrode for each exposed portion of the n ⁺ layer. As described above, after the step (B) is carried out, either the step (C) or the step (C') may be carried out first.

The method for removing the passivation film is not particularly limited. For example, a paste (so-called fire-through type silver paste) to which a component for removing the passivation film is added is applied to silver paste 70A and baked in the range of 550 to 900 ° C. By doing so, a method of forming a silver electrode while removing the passivation film directly under the paste (method of FIG. 1 (e) → FIG. 1 (f)), a method of applying an etching paste, a method of irradiating a laser beam, etc. are mentioned. Can be done.

When the fire-through type silver paste is used, for example, as shown in FIG. 1 (e), silver paste 70A is applied to the surface of the passivation film and then fired in the range of 550 to 900 ° C. As shown in FIG. 1 (f), the silver electrode 70B can be formed on the exposed n ⁺ layer while removing the passivation film immediately under the coating.

The composition of the silver paste is not particularly limited, but for example, 100 parts by mass of silver powder, 0.1 to 10 parts by mass of glass frit, and 3 to 15 parts by mass of an organic vehicle containing a resin and / or an organic solvent. It is preferable that the paste contains a portion. The silver powder may be in the form of flakes, but may be spherical powder, and spherical powder is preferably used. Although the silver electrode is formed in this step, instead of the silver electrode, a copper electrode or an aluminum alloy electrode (unlike the aluminum electrode formed in the step (C)), "aluminum electrode" and "aluminum" are used in the present specification. The term "alloy electrode" is distinguished.) May be formed. As described above, in the present invention, a wide range of techniques known in the technical field of solar cells can be applied.

As for the shape and size of the silver electrode, it is preferable to print a straight line of 50 to 130 μm so that the aluminum electrode and the comb teeth are arranged.

Although the embodiments of the present invention have been described above, the present invention is not limited to such examples, and it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention.

Hereinafter, embodiments of the present invention will be described in more detail based on Examples, but the present invention is not limited thereto.
(Example 1)
A crystalline silicon substrate made of p-type single crystal silicon was prepared (FIG. 1 (a)) (substrate: 6 inches, thickness 200 μm). The surface of the crystalline silicon substrate was wet-etched with potassium hydroxide for the purpose of removing the damaged layer on the cut surface of the crystalline silicon substrate and forming a texture.

Process (A)
Subsequently, using PH ₃ (phosphine) as a raw material, P element is injected into the surface of the crystalline silicon substrate by an ion injection method in which the ionized raw material is irradiated toward the surface of the crystalline silicon substrate after generating plasma, and then activated. By annealing, an n ⁺ layer was partially formed so as to have a thickness of about 0.1 to 1 μm (FIG. 1 (b)).

Here, closed portion of the opening and 300μm of 700μm width crystalline silicon substrate surface by using a mechanical hard mask lined alternately region and the n ⁺ layer forming the n ⁺ layer by implanting P element is not formed The areas are alternated.

Process (B)
Next, a passivation film made of aluminum oxide is formed to about 15 to 50 nm by the plasma CVD method, and then a silicon nitride film is formed on the entire crystalline silicon substrate (main surface and back surface) by using silane gas and ammonia gas as an antireflection film by the plasma CVD method. ) (FIG. 1 (c). However, the antireflection film is not shown).

Process (C)
Following the step of forming an opening for the p ⁺ layer formed using aluminum electrodes, n ⁺ for the passivation film in the region where the layer is not formed, n ⁺ center depth is not formed regions of the layer 0 The laser irradiation was performed after adjusting the line shape to a width of 1 to 1.0 μm and a width of 30 μm, and an opening for forming a p ⁺ layer using an aluminum electrode was provided (FIG. 1 (d)).

Next, the aluminum paste was applied linearly with a thickness of 20 μm and a width of 70 μm to the p ⁺ layer forming opening using a screen printing machine so as to fill the opening, and the crystalline silicon substrate coated with the aluminum paste was applied. It was dried at 100 ° C. for 10 minutes (FIG. 1 (e)).

Process (C')
Further, as shown in FIGS. 2 and 3, a known silver paste is printed with a printing width of 50 μm so that the distance from the center to the center in the width direction of the silver electrode is 1000 μm so as to correspond with the aluminum electrode and the comb teeth. It was printed and dried at 100 ° C. for 10 minutes (FIG. 1 (e)). Next, firing was performed in a belt furnace at a peak temperature of 900 ° C. (FIG. 1 (f)). By this firing, an aluminum electrode (including a p ⁺ layer) is formed, and a silver electrode is formed on the surface of the n ⁺ layer.

As described above, a back contact type solar cell was obtained.

Since the process of Example 1 is simple, the number of processes required in Comparative Example 1 can be significantly reduced, and a significant reduction in manufacturing cost can be achieved. Moreover, since the p ⁺ layer and the n ⁺ layer are not in contact with each other, the leakage current between the p ⁺ layer and the n ⁺ layer is significantly reduced. The time required to manufacture the back-contact type solar cell was 230 minutes.
(Comparative Example 1)
Similar to the prior art, the surface of the light receiving surface of the crystalline silicon substrate was texture-etched to form an uneven shape, a dielectric layer was formed so as to be in contact with the entire surface of the crystalline silicon substrate, and an insulating layer was further formed. At the same time, a back contact type solar cell was obtained by repeating patterning and etching in order to form an n ⁺ layer and a p ⁺ layer on the back surface of the crystalline silicon substrate. The specific procedure will be described in detail below.

First, a crystalline silicon substrate made of n-type single crystal silicon was prepared (substrate: 6 inches, thickness 200 μm). The front and back surfaces of the prepared crystalline silicon substrate were wet-etched with a mixed solution of hydrofluoric acid and nitric acid for the purpose of removing the damaged layer on the cut surface of the prepared crystalline silicon substrate.

Subsequently, an emitter layer and a BSF layer were formed on the back surface side of the crystalline silicon substrate. As shown in FIG. 4, a pattern was formed so that the desired diffusion region was formed in a band shape in which the n-type diffusion region and the p-type diffusion region were alternately formed. Specifically, the width (A) of the n-type diffusion region is 2500 μm, the width (B) of the p-type diffusion region is 1000 μm, the space (C) between the n-type diffusion region and the p-type diffusion region is 250 μm, at the edge of the substrate. The space (D) between the edge of the nearest diffusion layer and the edge of the substrate was 1000 μm.

First, in order to form a p-type diffusion layer, heat treatment was performed at 900 to 1000 ° C. by vapor phase diffusion using BBr ₃ to form a p-type diffusion region. After the heat treatment, the glass component attached to the crystalline silicon substrate was cleaned and removed by glass etching or the like.

Subsequently, a passivation film made of silicon oxide was formed at about 15 to 50 nm by the plasma CVD method, and then a silicon nitride film was formed on the back surface of the crystalline silicon substrate by the plasma CVD method using silane gas and ammonia gas as an antireflection film. Then, the p-type diffusion region formed on the front side of the crystalline silicon substrate was removed by immersing it in a mixed solution of hydrofluoric acid and nitric acid.

Subsequently, as a mask for forming the pattern of the n-type diffusion layer, an oxide film was formed on the back surface in addition to the desired n-type diffusion region by the same treatment. An n-type diffusion region was formed on the back surface by performing a heat treatment at 900 to 1000 ° C. by vapor phase diffusion using POCl ₃ . Further, for the purpose of removing the oxide film on the surface of the crystalline silicon substrate and forming a texture, the surface of the silicon substrate was wet-etched with an alkaline solution (potassium hydroxide).

After that, in order to form a P-diffused n ⁺ layer on the surface, heat treatment was performed at 900 to 1000 ° C. by vapor phase diffusion using POCl ₃ to form an n-type diffusion region on the surface.

Subsequently, after the heat treatment, the glass components attached to the crystalline silicon substrate were similarly cleaned by glass etching. Then, a silicon nitride film was formed on the entire front and back surfaces of the crystalline silicon substrate by using silane gas and ammonia gas as the antireflection film by the plasma CVD method.

Subsequently, in order to form an electrode, the SiNx contact portion on the back surface of the crystalline silicon substrate was patterned, and the aluminum electrode was formed by aluminum vapor deposition.

After that, Ni, Cu, and Ag plating were performed so that they could be contacted with aluminum, and annealing treatment was performed.

As described above, a back contact type solar cell was obtained.

The time required was 480 minutes due to the complicated process.

10 Crystallized silicon substrate 20 n ⁺ layer 30 Exposed part of crystalline silicon substrate (part where n ⁺ layer is not formed)
40 Passivation film 50 Exposed part of crystalline silicon substrate (part where the passivation film is removed)
60A Aluminum paste for forming aluminum electrode 60B Aluminum electrode 60C Aluminum-silicon alloy layer 60D BSF layer 70A Silver paste for forming silver electrode 70B Silver electrode 70 Aluminum electrode 72 Silver electrode 74 Silver electrode for aluminum bonding An type Width of diffusion region B Width of p-type diffusion region Space between Cn-type diffusion region and p-type diffusion region D Space between the end of the diffusion layer closest to the edge of the substrate and the edge of the substrate 1000

Ion injection device

1001, 1002 Vacuum chamber 1003 Insulation Member 1004 Stage 1005 Gas supply source 1010 Plasma 1100 RF introduction coil 1101 Permanent magnet 1102

RF introduction window

1200, 1201 Electrode 1300 DC power supply 1301 AC power supply S1 substrate

Claims

A method for manufacturing back-contact solar cells.
Step (A) of partially forming an n + layer on the back surface of a crystalline silicon substrate by an ion implantation method using a mechanical hard mask and activation annealing.
Of the steps (B) obtained in the step (A) for forming a passivation film on both sides of the crystalline silicon substrate having the n + layer, and the passivation film formed on the back surface side of the crystalline silicon substrate. A step (C) of removing a part or all of the region directly covering the crystalline silicon substrate to form one or more aluminum electrodes on the exposed crystalline silicon substrate.
A method for manufacturing a back-contact type solar cell, which comprises the following in order.
After the step (B), a part of the passivation film formed on the back surface side of the crystalline silicon substrate, which covers the crystalline silicon substrate via the n + layer, was removed and exposed. It has a step (C') of forming one or more silver electrodes in the n + layer.
The manufacturing method according to claim 1, wherein the step (C) and the step (C') are in no particular order.
The manufacturing method according to claim 2, wherein a copper electrode or an aluminum alloy electrode is formed in place of the silver electrode in the step (C').
The aluminum electrode is formed by firing a coating film of an aluminum paste containing 2 to 20 parts by mass of an organic vehicle and 0.15 to 15 parts by mass of a glass frit with respect to 100 parts by mass of aluminum powder at 650 to 900 ° C. , The manufacturing method according to any one of claims 1 to 3.
The manufacturing method according to claim 2, wherein the aluminum electrodes and the silver electrodes are formed so as to be alternately arranged on the back surface side of the crystalline silicon substrate.