阅读说明：本技术 背接触型太阳能电池单元的制造方法 (Method for manufacturing back contact type solar cell unit ) 是由 铃木绍太 马尔万·达姆林 山口升 铃木英夫 于 2020-03-13 设计创作，主要内容包括：提供背接触型太阳能电池单元的制造方法,能够以比现有制造方法少的工序数实施。本发明是背接触型太阳能电池单元的制造方法,依次有：在结晶硅基板(10)背面形成氧化膜(20)的工序(A)；在所述氧化膜(20)的暴露面形成硅薄膜层(30A)的工序(B)；在所述硅薄膜层(30A)以用机械硬掩模的离子注入法及活化退火局部形成n～(+)层(40)的工序(C)；在经所述工序(C)所得具有所述氧化膜(20)、所述硅薄膜层(30B)及所述n～(+)层(40)的所述结晶硅基板(10)两面形成钝化膜(50)的工序(D)；将形成于所述结晶硅基板(10)背面侧的所述钝化膜(50)的未覆盖所述n～(+)层(40)的区域局部去除,在暴露的所述硅薄膜层(30B)形成一或多个铝电极(60B)的工序(E)。(Provided is a method for manufacturing a back contact type solar cell, which can be performed with a smaller number of steps than conventional manufacturing methods. The invention relates to a method for manufacturing a back contact type solar cell unit, which sequentially comprises the following steps: a step (A) for forming an oxide film (20) on the back surface of a crystalline silicon substrate (10); a step (B) for forming a silicon thin film layer (30A) on the exposed surface of the oxide film (20); n is locally formed on the silicon thin film layer (30A) by ion implantation using a mechanical hard mask and activation annealing + A step (C) for forming a layer (40); the silicon thin film layer (30B) and the oxide film (20) obtained by the step (C)N is + A step (D) for forming a passivation film (50) on both surfaces of the crystalline silicon substrate (10) of the layer (40); the passivation film (50) formed on the back side of the crystalline silicon substrate (10) is not covered with the n + And a step (E) for partially removing the layer (40) and forming one or more aluminum electrodes (60B) on the exposed silicon thin film layer (30B).)

1. A method for manufacturing a back contact type solar cell, comprising the steps of:

a step (A) of forming an oxide film on the back surface of a crystalline silicon substrate;

forming a silicon thin film layer on an exposed surface of the oxide film;

forming n locally on the silicon thin film layer by ion implantation using a mechanical hard mask and activation annealing⁺A step (C) of forming a layer;

the oxide film, the silicon thin film layer and the n obtained in the step (C)⁺A step (D) of forming a passivation film on both surfaces of the crystalline silicon substrate of the layer; and

uncovered with the n in the passivation film to be formed on the back surface side of the crystalline silicon substrate⁺A step (E) of removing a part of the layer region and forming one or more aluminum electrodes on the exposed silicon thin film layer.

2. The manufacturing method according to claim 1,

the step (D) is followed by a step (E') of forming the passivation film on the back surface side of the crystalline silicon substrate with the oxide film and the n interposed therebetween⁺Removing a part of the region of the layer covering the crystalline silicon substrate and exposing the n⁺One or more silver electrodes are formed on the layer,

the step (E) is in a different order from the step (E').

3. The production method according to claim 2, wherein in the step (E'), a copper electrode or an aluminum alloy electrode is formed instead of the silver electrode.

4. The production method according to any one of claims 1 to 3,

the aluminum electrode is formed by sintering 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 per 100 parts by mass of aluminum powder at 650 to 900 ℃.

5. 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.

Technical Field

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

Background

In recent years, as a crystalline solar cell having high conversion efficiency, a structural unit called an Interdigitated Back Contact (IBC) solar cell in which n is provided on the Back surface of a crystalline silicon substrate has been actively developed⁺Diffusion layer and p⁺The diffusion layer has a back electrode formed on its surface. In addition, in order to improve the characteristics, a structure in which both surfaces of the crystalline silicon substrate of the solar cell are covered with an oxide film or a nitride film to reduce power loss in power generation has been studied.

In a general silicon solar cell structure, an electrode on the light receiving surface (main surface) side and an electrode on the back surface side of the solar cell are provided. When the electrode is formed on the light receiving surface (main surface) side in this way, sunlight may be reflected and absorbed by the electrode, and thus the amount of incident sunlight may be reduced according to the area of the electrode. On the other hand, in the back contact type solar cell, wiring resistance is reduced by collecting wiring on the back surface side, and therefore, not only can power loss be reduced, but also it is not necessary to provide an electrode on the light receiving surface, and therefore, the light receiving surface is enlarged and a large amount of light can be taken in. In addition, as described above, by forming a passivation film (for example, an oxide film) for reducing power loss on the back surface of the crystalline silicon substrate of the solar cell and forming a polycrystalline semiconductor layer thereon, it is possible to improve power generation efficiency while satisfying both the passivation effect and the effect as an electrode.

As such a back contact type solar cell, there is disclosed a solar cell in which a surface of a light-receiving surface of a crystalline silicon substrate is textured by etching or peeling a resin to form a concave-convex shape, a dielectric layer is formed so as to be in contact with the entire surface of the crystalline silicon substrate, an insulating layer is further formed, and n is formed on a back surface of the crystalline silicon substrate⁺Layer and p⁺The patterning and etching are repeated for the layer to reduce short-circuiting between the p-electrode and the n-electrode (for example, patent document 1).

However, in the technique of patent document 1, n is formed⁺Layer and p⁺The layer needs to be repeatedly patterned and etched, and thus, the number of manufacturing steps is increased. In addition, since the risk of residual adhesive due to printing, curing, and peeling of the release resin is high, it takes time to perform a cleaning process on the residue. And, to form n⁺Layer and p⁺The layer electrode is formed by vapor deposition or sputtering, and these methods also require a long processing time.

In order to improve the conversion efficiency of solar light into electric power, a solar cell structure called a passivation contact type has been developed, in which both surfaces of a semiconductor substrate are covered with a passivation film, and electric power is taken out through the passivation film, thereby achieving high power generation efficiency. However, in order to have a structure in which both surfaces are passivated as a whole and power is extracted, it is necessary to perform a process more complicated than that of a conventional back contact type solar cell (for example, non-patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-171095

Non-patent document

Non-patent document 1: "Laser contact options for local poly-Si-metal contacts addressing 26.1% effective POLO-IBC Solar Cells (Laser contact openings for local polysilicon metal contacts that can achieve a POLO-IBC Solar cell efficiency of 26.1%)", Felix Hasse, Solar Energy Materials and Solar Cells 186(2018) 184-.

Disclosure of Invention

Technical problem to be solved

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a back contact type solar cell, which can be performed with fewer steps than conventional manufacturing methods.

(II) technical scheme

In order to achieve the above object, the present inventors have intensively studied and found that a back contact type solar cell can be manufactured with a smaller number of steps than a conventional manufacturing method using an ion implantation method using a mechanical hard mask and having a specific step. The present inventors have further studied and completed the present invention based on this finding.

That is, the present invention relates to a method for manufacturing a back contact type solar cell as follows.

1. A method for manufacturing a back contact type solar cell, comprising the steps of:

a step (A) of forming an oxide film on the back surface of a crystalline silicon substrate;

forming a silicon thin film layer on an exposed surface of the oxide film;

forming n locally on the silicon thin film layer by ion implantation using a mechanical hard mask and activation annealing⁺A step (C) of forming a layer;

the oxide film, the silicon thin film layer and the n obtained in the step (C)⁺A step (D) of forming a passivation film on both surfaces of the crystalline silicon substrate of the layer; and

will be formed at the junctionN in the passivation film on the back surface side of the crystalline silicon substrate is not covered⁺A step (E) of removing a part of the layer region and forming one or more aluminum electrodes on the exposed silicon thin film layer.

2. The production method according to item 1 above, characterized in that,

the step (D) is followed by a step (E') of forming the passivation film on the back surface side of the crystalline silicon substrate with the oxide film and the n interposed therebetween⁺Removing a part of the region of the layer covering the crystalline silicon substrate and exposing the n⁺One or more silver electrodes are formed on the layer,

the step (E) is in a different order from the step (E').

3. The production method according to the above item 2, characterized in that,

in the step (E'), a copper electrode or an aluminum alloy electrode is formed instead of the silver electrode.

4. The production method according to any one of the above items 1 to 3,

the aluminum electrode is formed by sintering 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 per 100 parts by mass of aluminum powder at 650 to 900 ℃.

5. The production method according to the above item 2, characterized in that,

the aluminum electrodes and the silver electrodes are formed on the back surface side of the crystalline silicon substrate so as to be alternately arranged.

(III) advantageous effects

According to the method for manufacturing the back contact type solar cell unit of the present invention, it is not necessary to form n⁺Layer and p⁺The back contact type solar cell can be manufactured by repeating the patterning and etching of the layer, and by a smaller number of steps than in the conventional manufacturing method. Therefore, there is a great advantage in terms of the manufacturing cost of the back contact type solar cell unit. In addition, n is formed by ion implantation using a mechanical hard mask and activation annealing⁺Layer, thus in n⁺Layer and p⁺Arranged between layersThe presence of the insulating layer also provides an effect of suppressing a leakage current (loss of electric power) as compared with the conventional manufacturing method.

Drawings

Fig. 1-1 is an explanatory view (previous stage) of a method for manufacturing a back contact type solar cell according to the present invention.

Fig. 1 to 2 are explanatory views (later stages) of the method for manufacturing the back contact type solar cell unit of the present invention.

Fig. 2 is a schematic view of a back contact type solar cell of the embodiment.

Fig. 3 is an enlarged view of a schematic view of the back contact type solar cell of the embodiment.

Fig. 4 is an explanatory view of a layer structure in the back contact type solar cell unit of the comparative example.

Fig. 5 is a schematic diagram showing an example of an ion implantation apparatus to which the method for manufacturing a back contact type solar cell of the present invention is applied.

Detailed Description

The method for manufacturing a back contact type solar cell according to the present invention includes, in order:

a step (A) of forming an oxide film on the back surface of a crystalline silicon substrate;

forming a silicon thin film layer on an exposed surface of the oxide film;

forming n locally on the silicon thin film layer by ion implantation using a mechanical hard mask and activation annealing⁺A step (C) of forming a layer;

the oxide film, the silicon thin film layer and the n obtained in the step (C)⁺A step (D) of forming a passivation film on both surfaces of the crystalline silicon substrate of the layer; and

uncovered with the n in the passivation film to be formed on the back surface side of the crystalline silicon substrate⁺A step (E) of removing a part of the layer region and forming one or more aluminum electrodes on the exposed silicon thin film layer.

According to the method for manufacturing the back contact type solar cell unit of the present invention having the above-described features, it is not necessary to form n⁺Layer and p⁺The back contact type solar cell can be manufactured by repeating the patterning and etching of the layer, and by a smaller number of steps than in the conventional manufacturing method. Therefore, there is a great advantage in terms of the manufacturing cost of the back contact type solar cell unit. In addition, n is formed by ion implantation using a mechanical hard mask and activation annealing⁺Layer, thus in n⁺Layer and p⁺The insulating layer is provided between the layers, and thus, a leakage current (loss of electric power) can be suppressed as compared with a conventional manufacturing method.

Hereinafter, the method for manufacturing the back contact type solar cell according to the present invention (the method for manufacturing the present invention) will be described with reference to the drawings.

Process (A)

In the step (A), an oxide film 20 is formed on the back surface of the crystalline silicon substrate 10 (FIG. 1-1 (a)) (FIG. 1-1 (b)).

As the crystalline silicon substrate to be used, a known crystalline silicon substrate used for a back contact type solar cell can be widely used, and is not particularly limited. Both the n-type silicon semiconductor substrate and the p-type silicon semiconductor substrate can be used, and can be appropriately selected according to the intended use and specification of the solar cell. In this specification, a crystalline silicon substrate is referred to as a principal surface (light-receiving surface when used as a cell) on one surface and a back surface on the other surface.

In addition, the crystalline silicon substrate may be subjected to wet etching with an alkali solution or the like in order to remove a damaged layer on a cut surface and form a texture in advance.

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

A known technique can be used for forming an oxide film on the back surface of the crystalline silicon substrate.

Specifically, there are a technique of forming an oxide film by heating a crystalline silicon substrate, a technique of forming an oxide film by immersing a crystalline silicon substrate in nitric acid, a technique of forming an oxide film by immersing a crystalline silicon substrate in ozone water, and the like.

The thickness of the oxide film is not limited, but is preferably 0.5 to 4nm, more preferably 1.0 to 2.0 nm. In the production method of the present invention, the oxide film may be formed on the back surface (entire back surface) of the crystalline silicon substrate, or may be formed on the other surface (entire main surface) of the crystalline silicon substrate as needed (fig. 1-1 (b) shows an embodiment in which the oxide film 20 is formed on the back surface and the entire main surface (both surfaces) of the crystalline silicon substrate 10). In this case, the effect of suppressing the leakage current when the solar battery cell is used can be further improved.

Process (B)

Step (B) is to form a silicon thin film layer 30A on the exposed surface of the oxide film (FIG. 1-1 (c)). The oxide film is an oxide film formed on the back surface of the crystalline silicon substrate, which is required to be provided in the step (a).

A known technique can be used to form the silicon thin film layer on the exposed surface of the oxide film formed on the back surface of the crystalline silicon substrate.

Specifically, the plasma CVD method, the atmospheric pressure CVD method (APCVD) for semiconductor, the reduced pressure CVD method (LPCVD) for semiconductor, the sputtering method, and the like can be given. The thickness of the silicon thin film layer is not limited, and is usually about 10 to 150 nm.

Process (C)

Step (C) of locally forming n on the silicon thin film layer 30A by an ion implantation method using a mechanical hard mask and activation annealing⁺Layer 40 (FIG. 1-1 (d)). In (d) of FIGS. 1-1, the portion 40 is such that n is formed⁺The layer portion, the portion in which the state of 30A is maintained is not formed with n⁺A portion of a layer.

Form n⁺The ion implantation of the layer may use well-known techniques. In the manufacturing method of the present invention, an ion implantation method using a mechanical hard mask is particularly used. Mechanical hard mask for n⁺The layer is locally disposed on the silicon thin film layer. The mechanical hard mask may be, for example, a mechanical hard mask in which openings of 700 μm width and closed portions of 300 μm are alternately arranged, and in this case, n is 700 μm width⁺The layer 40 is spaced apart by 300 μm (corresponding to n not being formed)⁺Portion 30A of the layer) is formed in a pattern. The mechanical hard mask may be of a known type and may be made ofExamples of the material include carbon, silicon, copper, and quartz.

In the ion implantation method, for example, the following techniques can be used: to adjust the pH₃(phosphine) as a raw material, plasma is generated and ionized, and then the silicon thin film layer is irradiated with an ion beam. In this case, a mechanical hard mask is used to distinguish between a portion irradiated with the ion beam and a portion not irradiated with the ion beam. As an ion implantation apparatus for performing the ion implantation method, a known mass separation type ion implantation apparatus or a non-mass separation type ion implantation apparatus can be used.

Fig. 5 is a schematic diagram of a non-mass-separation type ion implantation apparatus. The summary 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 mounting table 1004, and a gas supply source 1005. The ion implantation apparatus 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 chamber 1002 has a smaller diameter than the vacuum chamber 1001, and is provided above the vacuum chamber 1001 via an insulating member 1003. The vacuum tanks 1001 and 1002 can be maintained in a reduced pressure state by a vacuum exhaust means such as a turbo molecular pump. The mounting table 1004 is provided in the vacuum chamber 1001. The mounting table 1004 can support the substrate S1. A heating mechanism for heating the substrate S1 may be provided in the mounting table 1004. Substrate S1 is a crystalline silicon substrate (having an oxide film and a silicon thin film layer on the back surface side, and a part of the silicon thin film layer being the subject of ion implantation) used in the manufacturing method of the present invention. Further, a gas for ion implantation is introduced into the vacuum chamber 1002 from a gas supply source 1005.

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

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

Another electrode (for example, a mesh electrode) 1201 having a plurality of openings is disposed below the electrode 1200. 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. Thereby, positive ions in the plasma 1010 are extracted from the plasma 1010 by the electrode 1201.

The extracted positive ions can reach the substrate S1 through the mesh-like electrodes 1200 and 1201. In the ion implantation apparatus 1000, the acceleration voltage of the positive ions can be set, for example, in a range of 1kV or more and 30kV or less. Further, a bias power supply capable of adjusting an acceleration voltage may be connected to the mounting table 1004.

A gas containing an impurity element (n-type impurity element) implanted on the substrate S1 is introduced into the vacuum chamber 1002. Plasma 1010 is formed in the vacuum chamber 1002 by the gas, and n-type impurity ions in the plasma 1010 are implanted into the substrate S1. The n-type impurity ion is, for example, P, PX⁺、PX²⁺、PX³⁺And the like. Here, "X" is any of hydrogen and halogen (F, Cl).

In the present embodiment, the mode of forming the Plasma 1010 is not limited to the ICP mode, and may be an Electron Cyclotron resonance Plasma (Electron Cyclotron resonance Plasma) mode, a Helicon Wave Plasma (Helicon Wave Plasma) mode, or the like. In addition, when the n-type impurity ions are implanted into the substrate S1, a gas containing hydrogen (for example, PH) may be added to the gas for ion implantation from the viewpoint of repairing the lattice defect of the substrate S1₃、BH₂Etc.).

The conditions for the activation annealing are not limited, and the temperature is preferably 600 to 1000 ℃, more preferably 700 to 900 ℃. The atmosphere in the annealing is preferably a step of setting the oxygen concentration to 1 to 100%, more preferably a step of setting the oxygen concentration to 5 to 50%. In addition, the silicon thin film layer 30A (particularly, an amorphous silicon thin film layer or a microcrystalline silicon thin film layer) is changed into a polycrystalline silicon thin film layer 30B by the activation annealing. Therefore, the silicon thin film layer in the subsequent step represents the polysilicon thin film layer 30B.

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

Process (D)

The step (D) is to form a film having the oxide film 20, the silicon thin film layer (polysilicon thin film layer; the same applies hereinafter) 30B and the n obtained in the step (C)⁺Passivation films 50 are formed on both sides of the crystalline silicon substrate of the layer 40 ((f) of fig. 1-2). That is, n is formed in the step (C) on the back surface side of the crystalline silicon substrate⁺Part of layer 40, at n⁺A passivation film 50 is formed on the layer 40 for the absence of n⁺In the layer portion, a passivation film is formed on the silicon thin film layer 30B. Further, a passivation film is formed on the surface of the crystalline silicon substrate on the principal surface side of the crystalline silicon substrate, either directly or via an oxide film optionally formed.

The passivation film is not particularly limited as long as it can have a passivation effect by 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 used. These films may be a single layer of only one layer, or a plurality of layers may be stacked.

The method for forming the passivation film is not particularly limited, and examples thereof include various chemical vapor methods such as a plasma CVD method, an atmospheric pressure CVD method for semiconductor, and an ALD method (atomic layer deposition method), and a sputtering method. More specifically, a method of forming a passivation film made of aluminum oxide by ALD using trimethylaluminum as a raw material is given.

The thickness of the passivation film is not particularly limited, but is preferably 5 to 200nm, and more preferably 10 to 80nm, from the viewpoints of the passivation effect and the operability in the passivation film removal step described later. Further, it is preferable that an antireflection film (not shown) is further provided on the surface of the passivation film, and the antireflection film is obtained by forming a silicon nitride film on the surface of the passivation film in a silane gas and ammonia gas atmosphere by, for example, a plasma CVD method.

Process (E)

Step (E) of leaving the passivation film formed on the back surface side of the crystalline silicon substrate uncovered with the n⁺A part of the region of the layer is removed ((g) of fig. 1-2), and one or more aluminum electrodes 60B are formed on the exposed silicon thin-film layer 30B ((i) of fig. 1-2). Here, when the passivation film is removed at a plurality of places, it is preferable to provide an aluminum electrode one by one for each exposed portion of the silicon thin film layer.

The part for removing the passivation film is uncovered n in the passivation film formed on the back side of the crystalline silicon substrate⁺A portion of a region of a layer. 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 removing the passivation film and forming an aluminum electrode on the exposed silicon thin film layer, a known method can be widely used, and is not particularly limited. Specifically, a method of providing and sintering an aluminum paste 60A on the exposed silicon thin film layer by an appropriate method such as coating (fig. 1-2 (h) shows a state before sintering, and fig. 1-2 (i) shows a state after sintering) can be exemplified. By this method, the aluminum-silicon alloy layer 60C and the BSF layer 60D are formed on the silicon thin film layer 30B ((i) of fig. 1-2). In fig. 1-2 (i), the aluminum paste is fired to form an aluminum-silicon alloy layer and a BSF layer on the silicon thin film layer, thereby forming an aluminum electrode 60B.

The sintering temperature of the aluminum paste is not particularly limited, but is preferably 650 to 900 ℃. The composition of the aluminum paste is not particularly limited, and for example, 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.

The aluminum powder may be high-purity aluminum or an aluminum alloy, and preferably an aluminum-silicon alloy or an aluminum-silicon-magnesium alloy is used.

The shape and size of the aluminum electrode are preferably 40 to 200 μm in width from the viewpoint of the necessity of covering the exposed silicon thin film layer, and the higher the electrode height is, the better in order to reduce the resistance value of the electrode. The larger the aspect ratio (width/height) of the printed Al line, the better.

Step (E')

The step (E') is to form the passivation film on the back surface side of the crystalline silicon substrate after the step (D) through the oxide film and the n⁺Removing a part of the region of the layer covering the crystalline silicon substrate and exposing the n⁺A step of forming one or more silver electrodes 70B on the layer 40, wherein the step (E) is in a different order from the step (E'). Here, when the passivation film is removed at a plurality of places, it is preferable that n is applied to each place⁺The exposed portions of the layers are provided one by one with silver electrodes. As described above, after the step (D) is performed, either of the step (E) and the step (E') may be performed first.

The method for removing the passivation film is not particularly limited, and examples thereof include a method (a method of fig. 1-2 (h) → fig. 1-2 (i)) of coating a paste (a so-called fire through type (japanese: ファイヤースルー type) silver paste) containing a component for removing the passivation film to the silver paste 70A, firing the paste at 550 to 900 ℃ to remove the passivation film directly below the paste, and forming a silver electrode, a method of coating an etching paste, and a method of irradiating a laser beam.

In the case of using the above fire-through type silver paste, for example, as shown in fig. 1-2 (h), the surface of the passivation film is coated with the silver paste 70A and then sintered at 550 to 900 ℃, whereby the passivation film directly under the coating can be removed and exposed n can be exposed as shown in fig. 1-2 (i)⁺On the layer, a silver electrode 70B is formed.

The composition of the silver paste is not particularly limited, and for example, a paste containing 0.1 to 10 parts by mass of a glass frit and 3 to 15 parts by mass of an organic vehicle containing a resin and/or an organic solvent with respect to 100 parts by mass of the silver powder is preferable. The silver powder may be in the form of a flake or a spherical powder, and the spherical powder is preferably used. Although the silver electrode is formed in this step, a copper electrode or an aluminum alloy electrode may be formed instead of the silver electrode (the term "aluminum electrode" is distinguished from the term "aluminum alloy electrode" in the present specification, unlike the aluminum electrode formed in step (E)). As such, the present invention can be widely applied to a technique known in the technical field of solar battery cells.

Regarding the shape and size of the silver electrode, 50 to 130 μm linear lines are printed so as to be the arrangement of the aluminum electrode and the comb teeth.

The embodiments of the present invention have been described above, but the present invention is not limited to these examples, and can be implemented in various ways without departing from the scope of the present invention.

[ examples ] A method for producing a compound

The embodiments of the present invention will be described in more detail below based on examples, but the present invention is not limited thereto.

(example 1)

A crystalline silicon substrate (FIG. 1-1 (a)) composed of p-type single crystal silicon (substrate: 6 inches, thickness: 200 μm) was prepared. In addition, in order to remove the damaged layer of the cut surface of the crystalline silicon substrate and form a texture, the surface of the crystalline silicon substrate was wet-etched using potassium hydroxide.

Process (A)

The crystalline silicon substrate is immersed in a nitric acid solution, thereby forming a silicon oxide film on both surfaces thereof (fig. 1-1 (b)).

Process (B)

A 200nm silicon thin film layer (amorphous silicon thin film layer) was formed on the back surface of the crystalline silicon substrate (having an oxide film) by CVD (fig. 1-1 (c)).

Process (C)

Then, to use PH₃(phosphine) as a raw material, implanting a P element into the silicon thin film layer by an ion implantation method in which the surface of the silicon thin film layer is irradiated with a plasma-generated and ionized raw material (see (d) in FIG. 1-1), and then locally forming n so as to have a thickness of about 0.1 to 1 μm by performing activation annealing⁺Layer (FIG. 1-1 (e)). The activation annealing also has the effect of polycrystallizing the amorphous silicon thin film layer.

Here, the silicon thin film layer was formed by alternately arranging openings of 700 μm width and 300 μm closed parts on the surface of the silicon thin film layerMechanical hard mask to implant P element and form n⁺Region of layer and not forming n⁺The regions of the layer alternate.

Process (D)

Next, after a passivation film made of alumina having a thickness of about 10 to 50nm was formed by a plasma CVD method, a silicon nitride film was formed as an anti-reflection film on the entire crystalline silicon substrate (main surface and rear surface) by a plasma CVD method using a silane gas and an ammonia gas (fig. 1-2 (f)). The antireflection film is not shown).

Process (E)

Next, as p in which an aluminum electrode was used was formed⁺A step of forming an opening for layer formation in which n is not formed⁺Passivation film of the region of the layer to form n⁺Laser irradiation is performed while adjusting the center of the region of the layer to be a linear shape having a depth of 0.1 to 1.0 μm and a width of 30 μm, and a p-electrode using an aluminum electrode is provided⁺An opening for layer formation (FIG. 1-2 (g)).

Then, for p⁺The opening for layer formation was coated with an aluminum paste in a line shape having a thickness of 20 μm and a width of 70 μm using a screen printer so as to fill the opening, and the crystalline silicon substrate coated with the aluminum paste was dried at 100 ℃ for 10 minutes ((h) of fig. 1-2).

Step (E')

Further, as shown in fig. 2 and 3, a known silver paste was printed with a printing width of 50 μm so as to correspond to the aluminum electrode through the comb teeth and to make the distance from the center to the center in the width direction of the silver electrode 1000 μm, and dried at 100 ℃ for 10 minutes ((h) of fig. 1-2). Next, the sintering was carried out in a belt furnace with the peak temperature set at 900 ℃ (fig. 1-2 (i)). By this sintering, an aluminum electrode (containing p) was formed⁺Layer) and at n⁺The surface of the layer forms a silver electrode.

A back contact type solar cell unit was thus obtained as above.

The process of example 1 was simple, and thus the time required to manufacture the back contact type solar cell unit was 260 minutes.

For reference, in example 1, the difference in time required to manufacture the back contact type solar cell unit was 30 minutes compared to the manner in which the process (a) and the process (B) were not performed. As for the effect of suppressing the manufacturing cost and the leakage current, it was confirmed that: by suppressing the leakage current, the discharge voltage Voc characteristic is improved by 1.5%, and the curve factor characteristic is improved by 2.5%, thereby reducing the manufacturing cost per unit power generation amount.

Comparative example 1

In the same manner as in the conventional technique, the surface of the light-receiving surface of the crystalline silicon substrate is texture-etched to form a concave-convex shape, the silicon oxide film is formed so as to be in contact with the entire surface of the crystalline silicon substrate, the silicon thin film layer (amorphous silicon thin film layer) is further formed, and n is formed on the front surface and the back surface of the crystalline silicon substrate⁺Layer and p⁺And repeatedly implanting impurities into the layer by using an ion implantation method to obtain the back contact type solar cell unit. The specific steps are described in detail below.

First, a crystalline silicon substrate (substrate: 6 inches, thickness: 200 μm) made of p-type single crystal silicon was prepared. In order to remove the cut surface damaged layer of the prepared crystalline silicon substrate, the front surface and the back surface of the crystalline silicon substrate are wet-etched using a solution such as a mixed solution of hydrofluoric acid and nitric acid.

Next, the crystalline silicon substrate is immersed in a nitric acid solution, thereby forming a silicon oxide film on both surfaces.

Subsequently, 200nm silicon thin film layers (amorphous silicon thin film layers) were formed on both surfaces. As shown in fig. 4, a pattern in which p-type diffusion layers and n-type diffusion layers are alternately formed in a stripe shape is formed on the silicon thin film layer on the back surface by an ion implantation method using a resist mask. Specifically, the width (A) of the n-type diffusion region was set to 700 μm, the width (B) of the p-type diffusion region was set to 200 μm, the space (C) between the n-type diffusion region and the p-type diffusion region was set to 50 μm, and the distance (D) between the diffusion layer end closest to the substrate end and the substrate end was set to 1000 μm. Then, p is annealed at 875 ℃ in a heating furnace⁺Layer n⁺Activating the layer and modifying the amorphous silicon film layer to the polycrystalline silicon film layer.

Then, after a passivation film of about 30 to 50nm of silicon oxide is formed by a plasma CVD method, a passivation film of 10 to 30nm of aluminum oxide is formed on the surface by an ALD method, and then a silicon nitride film is formed as an anti-reflection film on the back surface of the crystalline silicon substrate by a plasma CVD method using a silane gas and an ammonia gas.

Next, in order to form an electrode, a pattern was formed on the back surface of the crystalline silicon substrate, and an aluminum electrode was formed by aluminum vapor deposition.

Thereafter, Ni, Cu, and Ag were plated so as to be in contact with aluminum, and annealing was performed. Further, the formed electrode is separated from p by the laser irradiation device⁺An electrode in contact with the layer, and⁺an electrode in contact with the layer.

A back contact type solar cell unit was thus obtained as above.

The time required was 350 minutes because the process was complicated.

Description of the reference numerals

10-crystalline silicon substrate; 20-an oxide film; 30A-a silicon thin film layer; 30B-silicon thin film layer (after activation annealing); 40-n⁺A layer; 50-a passivation film; 60A-aluminum paste for forming aluminum electrodes; 60B-aluminum electrodes; a 60C-aluminum-silicon alloy layer; a 60D-BSF layer; 70A-silver paste for forming silver electrode; 70B-silver electrode; 70-an aluminum electrode; 72-a silver electrode; 74-silver electrode for aluminum bonding; the width of the A-n type diffusion region; the width of the B-p type diffusion region; a space between the C-n type diffusion region and the p type diffusion region; d-the space between the end of the diffusion layer closest to the substrate end and the substrate end; 1000-an ion implantation device; 1001. 1002-vacuum groove; 1003-insulating member; 1004-a placing table; 1005-a gas supply source; 1010-plasma; 1100-RF lead-in coil; 1101-a permanent magnet; 1102-RF lead-in window; 1200. 1201-electrodes; 1300-a direct current power supply; 1301-an alternating current power supply; s1-substrate.