JPWO2014196253A1 - Method for forming p-type selective emitter - Google Patents

Abstract

A step of forming an organosilicon compound film on the light-receiving surface side of the silicon substrate, a step of removing a region where the high concentration diffusion layer is to be formed from the organosilicon compound film, and forming an opening in the region; Next, a first dopant coating agent is applied to cover the film and opening of the organosilicon compound, the first dopant is diffused from the organosilicon compound and the opening to the silicon substrate, and the first dopant is spread from the opening. A high-concentration diffusion layer comprising a step of forming a high-concentration diffusion layer in a portion where the dopant is diffused and a low-concentration diffusion layer in a portion where the first dopant is diffused through the organosilicon compound film. And a p-type selective emitter layer having a low-concentration diffusion layer can be easily produced, and a high-performance solar cell can be produced while maintaining the production yield at a high level. It can do today.

Description

  The present invention uses a film made of an organosilicon compound as a diffusion suppression mask for suppressing diffusion of a dopant, and forms a selective emitter layer in a p layer, and a p-type selective emitter layer formed by this formation method. It has a solar cell.

  A solar cell is a semiconductor element that converts light energy into electric power, and includes a pn junction type, a pin type, a Schottky type, and the pn junction type is widely used. Further, when solar cells are classified based on their substrate materials, they are broadly classified into three types: silicon crystal solar cells, amorphous (amorphous) silicon solar cells, and compound semiconductor solar cells. Silicon crystal solar cells are further classified into single crystal solar cells and polycrystalline solar cells. Since a silicon crystal substrate for a solar cell can be manufactured relatively easily, its production scale is currently the largest and is expected to become more widespread in the future (for example, Patent Document 1: JP-A-8-073297). Publication).

The output characteristics of a solar cell are generally evaluated by measuring an output current voltage curve using a solar simulator. The product of the output current I _max and the output voltage V _max on this curve, the point at which I _max × V _max is maximum is called the maximum output P _max , and this P _max is the total light energy (S × (I: S is the element area, I is the intensity of the irradiated light))
η = {P _max / (S × I)} × 100 (%)
Is defined as the conversion efficiency η of the solar cell.

In order to increase the conversion efficiency η, the short-circuit current Isc (output current value when V = 0 in the current-voltage curve) or Voc (output voltage value when I = 0 in the current-voltage curve) is increased. It is important to make the output current voltage curve as close to a square as possible. The squareness of the output current voltage curve is generally
FF = P _max / (Isc × Voc)
It can be evaluated by the fill factor (curve factor) defined by the equation (1). The closer the FF value is to 1, the closer the output current-voltage curve becomes to an ideal square, and the higher the conversion efficiency η.

  In order to improve the conversion efficiency η, it is important to reduce the surface recombination of carriers. In a silicon crystal solar cell, minority carriers generated by incident light of sunlight reach the pn junction surface mainly by diffusion, and then are transferred to the outside as majority carriers from the electrodes attached to the light receiving surface and the back surface. It is taken out and becomes electric energy.

  At that time, carriers that could be extracted as current through the interface states existing on the substrate surface other than the electrode surface may be recombined and lost, leading to a decrease in conversion efficiency η.

  Therefore, in high-efficiency solar cells, the light-receiving surface and back surface of the silicon substrate are protected by an insulating film except for the contact portion with the electrode, and carrier recombination at the interface between the silicon substrate and the insulating film is suppressed and converted. The efficiency η is improved.

  In order for solar cells to become more widespread in the future, higher conversion efficiency is required. As a means of increasing the conversion efficiency, for example, a high concentration diffusion layer containing a high concentration of dopant is formed only directly under the electrode, and the surface dopant concentration of the diffusion layer in the other part of the light receiving surface is lowered, that is, a selective emitter is formed. There is a method for improving the conversion efficiency.

  On the other hand, Patent Document 2 (Japanese Patent Application Laid-Open No. 2007-081300) proposes a method of forming a patterned diffusion layer by applying a silicon oxide film to a diffusion control mask (diffusion suppression mask). However, when the silicon oxide film is applied to a diffusion control mask (diffusion suppression mask), it is difficult to form a uniform film thickness of the silicon oxide film. There is a problem that a diffusion layer cannot be formed.

  Patent Document 3 (Japanese Patent Application Laid-Open No. 2004-221149) proposes that a plurality of types of coating agents are separately applied by an inkjet method to create regions with different dopant concentrations and dopant types in a simple process. ing. However, in such an ink jet system, when phosphoric acid or the like is used as a dopant, a countermeasure against corrosion is necessary, and the apparatus becomes complicated and maintenance becomes complicated. Further, even if coating agents having different dopant concentrations and types are applied separately by inkjet, if the diffusion is performed by a single heat treatment, a desired concentration difference cannot be obtained by autodoping.

  Further, Patent Document 4 (Japanese Patent Laid-Open No. 2004-28169) proposes a method of forming a low concentration diffusion layer and a high concentration diffusion layer by two heat treatments. However, in this method, it is necessary to perform thermal diffusion of the dopant twice, which may complicate the process and increase the manufacturing cost. However, if the heat treatment is performed once, the dopant is highly concentrated in portions other than the portion immediately below the electrode on the light receiving surface due to autodoping, and high conversion efficiency is not exhibited.

  Even in a solar cell having a p-type light-receiving surface, formation of a selective emitter is indispensable for high conversion efficiency, and control of the surface dopant concentration is important. However, it is not easy to form a boron selective emitter, and the conventional method requires a plurality of diffusion suppression mask formations and heat treatments, and the process is complicated and complicated.

JP-A-8-073297 JP 2007-081300 A JP 2004-221149 A JP 2004-28169 A

  The present invention has been made in view of the above problems, and provides a solar cell and a p-type selective emitter formation method that can form a p-type selective emitter layer by a simple method and have high energy conversion efficiency. The purpose is to do.

  As a result of intensive studies to achieve the above object, the inventors of the present invention formed a film made of an organosilicon compound on the light receiving surface side of a silicon substrate, and formed a film of an organosilicon compound at a portion corresponding to a p-layer high concentration diffusion region. After forming the opening and forming the opening, a boron-containing coating agent is applied and diffused over the organic silicon compound film and the opening, so that multiple heat treatment steps are not required, and it is simple and reliable. It has been found that a p-type selective emitter layer can be formed.

That is, when a diffusion suppression mask that suppresses the diffusion of the dopant to the boron dopant is applied to a film of an organosilicon compound such as a polysilazane film, there is a phenomenon that boron diffuses into the silicon substrate at a concentration proportional to the film thickness. confirmed.
In a solar cell, the surface dopant concentration on the light receiving surface should be low in order to improve the conversion efficiency in the short wavelength region, but in order to reduce the electrode contact resistance, it is necessary to increase the dopant concentration. When the dopant concentration in the diffusion layer decreases, ohmic contact cannot be obtained.

  In the present invention, the region of the silicon substrate on the light receiving surface side where the electrode is connected does not form an organic silicon compound film, and other regions are diffused using a film made of an organic silicon compound, Since the high concentration diffusion layer is formed in the region serving as the electrode connection position, the electrode contact resistance can be reduced, while the surface dopant concentration in the film formation region made of the organosilicon compound is lowered, the surface passivation is improved, and the short The conversion efficiency in the wavelength region can be improved, and a p-type selective emitter layer having a high-concentration diffusion layer and a low-concentration diffusion layer in the p-type diffusion layer can be easily formed.

Accordingly, the present invention provides the following p-type selective emitter formation method and solar cell.
[1] A step of forming an organosilicon compound film on the light-receiving surface side of the silicon substrate, and removing an area where the high-concentration diffusion layer is to be formed from the organosilicon compound film to form an opening in the area. And then applying a first dopant coating agent over the organosilicon compound film and opening, diffusing the first dopant from the organosilicon compound and opening to the silicon substrate, and from the opening Forming a high-concentration diffusion layer in a portion where the first dopant is diffused, and forming a low-concentration diffusion layer in a portion where the first dopant is diffused through the organosilicon compound film. Forming method.
[2] The selective emitter formation method according to [1], wherein the film of the organosilicon compound is a polysilazane film or a polysiloxane film.
[3] The selective emitter formation method according to [1] or [2], wherein the silicon substrate is n-type.
[4] The selective emitter formation method according to any one of [1] to [3], wherein the organic silicon compound film is formed with a thickness of 5 to 300 nm.
[5] The selective emitter formation method according to any one of [1] to [4], wherein the first dopant is boron.
[6] A solar cell comprising a p-type selective emitter layer formed by the selective emitter formation method according to any one of [1] to [5].

  According to the present invention, a solar cell having a p-type selective emitter layer having a high-concentration diffusion layer and a low-concentration diffusion layer can be easily manufactured, and a high-performance solar cell while maintaining a high manufacturing yield. Can be provided.

(A)-(H) are schematic sectional drawings which demonstrate the process sequentially about an example of the manufacturing method of the solar cell of this invention.

  Referring to FIG. 1 (H), a solar cell having a p-type selective emitter layer formed by the p-type selective emitter forming method of the present invention is formed on a silicon substrate 1 and a light receiving surface side of the silicon substrate 1, A p-type selective emitter layer 4 having a p-type high-concentration diffusion layer 4a and a low-concentration diffusion layer 4b having a dopant concentration lower than that of the high-concentration diffusion layer 4a, and the p-type selective emitter layer high-concentration diffusion layer 4a A solar cell comprising a light receiving surface electrode 7 to be electrically connected, an n-type diffusion layer 5 formed on the back side of the silicon substrate 1, and a back electrode 8 electrically connected to the n-type diffusion layer 5. In this p-type selective emitter forming method, a film made of an organosilicon compound is formed on the silicon substrate on the side to be the p-type diffusion layer, and the organosilicon compound corresponding to the region to be the electrode connection position of the p-type diffusion layer Partial removal of the membrane After forming an opening in a region to be a high concentration diffusion region, a dopant is applied on the film made of the organosilicon compound, and the dopant is simultaneously diffused into the silicon substrate through the film made of the opening and the organosilicon compound. Thus, a p-type selective emitter layer is formed.

  Hereinafter, although the manufacturing method of the solar cell using the p-type selective emitter formation method of this invention is demonstrated using drawing, this invention is not limited by this description.

1A to 1H are schematic cross-sectional views showing a manufacturing process according to an embodiment of the method for manufacturing a solar cell of the present invention. Hereinafter, each step will be described in detail.
(1) The silicon substrate 1 may be n-type or p-type, but an n-type substrate is used in Example 1 of the present invention. This silicon single crystal substrate may be produced by any of the Czochralski (CZ) method and the float zone (FZ) method. The specific resistance of the silicon substrate 1 is preferably 0.1 to 20 Ω · cm, and more preferably 0.5 to 2.0 Ω · cm from the viewpoint of producing a high-performance solar cell. As the silicon substrate, a phosphorus-doped n-type single crystal silicon substrate is preferable. The phosphorus-doped dopant concentration is preferably 1 × 10 ¹⁵ cm ^{−3 to} 5 × 10 ¹⁶ cm ⁻³ [FIG. 1 (A)].

(2) Damage etching / texture formation The silicon substrate 1 is immersed in an aqueous sodium hydroxide solution, for example, and the damaged layer is removed by etching. For removing damage from the substrate, a strong alkaline aqueous solution such as potassium hydroxide may be used, and a similar purpose can be achieved with an acid aqueous solution such as hydrofluoric acid. A random texture is formed on the substrate 1 subjected to damage etching. In general, a solar cell preferably has an uneven shape on the surface. The reason is that in order to reduce the reflectance in the visible light region, it is necessary to cause the light receiving surface to perform reflection at least twice as much as possible. The size of each of these peaks is preferably about 1 to 20 μm. Typical surface uneven structures include V-grooves and U-grooves. These can be formed using a grinding machine. In order to create a random concavo-convex structure, a method of performing wet etching by immersing in an aqueous solution of sodium hydroxide and isopropyl alcohol, or acid etching, reactive ion etching, or the like can be used. In the drawing, the texture structure formed on both sides is fine and therefore omitted.

(3) Formation of organosilicon compound film A film made of an organosilicon compound is formed on the surface of the textured silicon substrate that serves as the light-receiving surface [FIG. 1 (B)]. Examples of the film made of an organosilicon compound include a polysilazane film and a polysiloxane film. As a method for forming the film, in the case of a polysilazane film, a polysilazane solution is applied to the surface to be the light-receiving surface of the silicon substrate, and the solvent is removed by heat drying treatment, so that a self-crosslinking reaction proceeds and a polysilazane film is formed. The The method for applying the polysilazane solution is not particularly limited, such as a spin coating method, a spray method, or a dip method, but the spin coating method is simple and suitable.

The coating composition used for forming the polysilazane solution, that is, the polysilazane film, includes polysilazane and a solvent.
As polysilazane, the following general formula (1)
-(SiH ₂ NH) _n- (1)
The perhydropolysilazane represented by the formula (2) is preferred because there are few impurities remaining in the film after conversion. In addition, perhydropolysilazane is an inorganic polymer having — (SiH ₂ NH) — as a basic unit, all of its side chains being hydrogen, and being soluble in an organic solvent.

  The solvent may be any solvent that does not react with perhydropolysilazane. Toluene, xylene, dibutyl ether, diethyl ether, THF (tetrahydrofuran), PGME (propylene glycol ether ether), PGMEA (propylene glycol ether ether) ), Aromatic solvents such as hexane, aliphatic solvents, and ether solvents.

  The concentration of polysilazane in the solvent is preferably 1 to 30% by mass, and more preferably 3 to 20% by mass. If the amount is less than 1% by mass, the film thickness after coating becomes thin, and there is a risk that a difference in diffusion concentration in the p-type diffusion layer may not be obtained.

  The drying temperature for forming the polysilazane film is not a problem as long as it is equal to or higher than the boiling point of the solvent being used, but it is preferable to perform the drying temperature in the range of 80 to 200 ° C. The heating method is not particularly limited, and examples thereof include a method of heating with a hot plate and a method of using an electric furnace, and the method of using a hot plate is preferable from the viewpoint of cost and convenience of work. The thickness of the polysilazane film is preferably 5 to 300 nm, more preferably 50 to 100 nm. If the film thickness is too thin, a difference in diffusion concentration in the p-type diffusion layer cannot be obtained, and even if it is too thick, boron may not be able to diffuse through the polysilazane film.

  Note that the polysilazane film is baked and converted by heat treatment at the time of forming the p-type emitter layer to be converted into a silicon-containing inorganic thin film, and functions as a diffusion suppression mask.

  The polysiloxane film can be formed by using a vinyl group, amino group, epoxy group, carbinol group, silanol group, methacryl group on the side chain or terminal of a polysiloxane such as dimethylpolysiloxane, methylphenylpolysiloxane, or methylhydrogenpolysiloxane. Using a reactive polysiloxane modified with a reactive organic group such as a group, a polysiloxane film is formed by the same treatment as the polysilazane film. In this case, if necessary, an appropriate known cross-linking agent corresponding to the type of the polysiloxane may be used to form a cross-linked polysiloxane film.

In this case, the polysiloxane may be linear, branched or cyclic, and specifically, the one represented by the following formula (2) is preferably used.
R′R ₂ SiO— (R ₂ SiO) —SiR ₂ R ′ (2)
Here, in said formula, R is a C1-C3 alkyl group, R 'shows reactive organic groups, such as a vinyl group, an amino group, an epoxy group, a carbinol group, a silanol group, and a methacryl group.

  The thickness of the polysiloxane film is preferably 5 to 300 nm, more preferably 50 to 100 nm. If the film thickness is too thin, a difference in diffusion concentration in the p-type diffusion layer cannot be obtained, and if it is too thick, boron may not be able to diffuse through the polysiloxane film.

The polysiloxane film is baked by a heat treatment in the subsequent p-type emitter layer formation to be a silicon-containing inorganic thin film made of SiO ₂ and functions as a diffusion suppression mask.

(4) Removal of organosilicon compound film Part of the organosilicon compound film is partially removed from the region to be the electrode connection position of the p-type diffusion layer, and the opening 2a is formed in the region to be the high concentration diffusion region. Form [FIG. 1 (C)]. The method for removing the film made of the organosilicon compound is not particularly limited, and examples of known methods include removal by etching paste, removal by laser ablation, and removal by masking etching that covers areas not to be removed with an etching resistant mask. It is done. Of these, removal by laser ablation is simple and suitable.

(5) Formation of p-type selective emitter layer A coating agent 3 containing a boron dopant is applied on the organic silicon compound film formed on the light-receiving surface side of the silicon substrate 1 and covering the opening [FIG. ]. Thereafter, heat treatment is performed to form the p-type selective emitter layer 4 [FIG. 1E]. At this time, the film of the organosilicon compound becomes a silicon-containing inorganic thin film and exhibits a function as a diffusion suppression mask. That is, in the region where the silicon-containing inorganic thin film does not exist (opening region), the dopant is diffused as it is to form the high-concentration diffusion layer 4a, and in the region where the silicon-containing inorganic thin film exists, the diffusion of the dopant is suppressed more than in the opening region. Thus, the low concentration diffusion layer 4b is formed. Thereafter, the silicon-containing inorganic thin film is etched away together with the glass component.

The heat treatment temperature is preferably 800 to 1,100 ° C, particularly 900 to 1,000 ° C. The heat treatment time is usually 20 to 30 minutes. The dopant is preferably boron, and the surface dopant concentration of the high-concentration diffusion layer 4a in the p-type selective emitter layer 4 is preferably 1 × 10 ¹⁸ cm ^{−3 to} 5 × 10 ²⁰ cm ^{−3 and} more preferably 5 × 10 ^18. More preferably, cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ . On the other hand, the surface dopant concentration of the low-concentration diffusion layer 4b is preferably 1 × 10 ¹⁷ cm ^{−3 to} 5 × 10 ¹⁹ cm ^{−3, and} more preferably 5 × 10 ¹⁷ cm ⁻³ to 1 × 10 ¹⁹ cm ^−3. preferable.

(6) Formation of n-type diffusion layer The same process is performed on the back surface of the silicon substrate 1 to form the n-type diffusion layer 5 on the back surface [FIG. 1 (F)]. The dopant is preferably phosphorus. The surface dopant concentration of the n-type diffusion layer 5 is preferably 1 × 10 ¹⁸ cm ^{−3 to} 5 × 10 ²⁰ cm ^{−3, and} more preferably 5 × 10 ¹⁸ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ .

(7) Pn junction isolation Pn junction isolation is performed using a plasma etcher. In this process, the sample is stacked so that plasma and radicals do not enter the light-receiving surface and the back surface, and the end surface is cut by several microns in that state. After bonding and separation, glass components, silicon powder, and the like attached to the substrate are washed by glass etching or the like.

(8) Antireflection film formation Subsequently, in order to effectively take sunlight light into the silicon substrate, the antireflection film 6 is formed on both the front surface and the back surface of the silicon substrate [FIG. 1G]. A silicon nitride film is preferable as the antireflection film. This silicon nitride film also functions as a passivation film on the silicon substrate surface and inside. This film thickness is preferably 70 to 100 nm. Other antireflection films include a titanium dioxide film, a zinc oxide film, a tin oxide film, a tantalum oxide film, a niobium oxide film, a magnesium fluoride film, and an aluminum oxide film, which can be substituted. The formation method includes a plasma CVD method, a coating method, a vacuum deposition method, and the like. From the economical viewpoint, it is preferable to form the silicon nitride film by the plasma CVD method.

(9) Electrode formation Using a screen printing device or the like, a paste made of, for example, silver is printed on the p-type high concentration diffusion layer 4a and the n-type diffusion layer 5 using the screen printing device on the light receiving surface side and the back surface side. Then, it is applied to a comb-shaped electrode pattern and dried. Finally, in the firing furnace, firing is performed at 500 to 900 ° C. for 1 to 30 minutes, and the finger electrode 7, the back electrode 8, and the bus bar are electrically connected to the p-type high concentration diffusion layer 4 a and the n-type diffusion layer 5. The electrode 9 is formed [FIG. 1 (H)].

  In FIG. 1H, the bus bar electrode 9 is shown not to be connected to the diffusion layers 4 and 5, but is fired through by firing and is actually connected to the diffusion layer.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Example 1]
Crystal plane orientation (100), 15.65 cm square 200 μm thickness, as-slice specific resistance 2 Ω · cm (dopant concentration 7.2 × 10 ¹⁵ cm ⁻³ ) Phosphorus-doped n-type single crystal silicon substrate is immersed in an aqueous sodium hydroxide solution The damaged layer was removed by etching, and texture formation was performed by soaking in an aqueous solution obtained by adding isopropyl alcohol to an aqueous potassium hydroxide solution and performing alkali etching. A polysilazane solution was applied to the surface of the obtained silicon substrate 1 and dried on a hot plate at 150 ° C. to form a polysilazane film 2 having a thickness of 80 nm.
In addition, as polysilazane, the AZ120-20 perhydropolysilazane 20% dibutyl ether solution made from AZ was used.
Thereafter, the polysilazane film in the region immediately below the light-receiving surface electrode is removed with a laser, and then a coating agent containing a boron dopant is applied on the polysilazane film, followed by heat treatment at 950 ° C. for 30 minutes, and the p-type selective emitter layer 4 Formed.
Subsequently, after a coating agent containing a phosphorus dopant was applied to the back surface of the silicon substrate 1, heat treatment was performed at 900 ° C. for 30 minutes to form the n-type diffusion layer 5 on the back surface. After the heat treatment, the glass component attached to the substrate was removed by high concentration hydrofluoric acid solution and then washed.
Next, pn junction isolation was performed using a plasma etcher. In order to prevent plasma and radicals from entering the light-receiving surface and back surface, the end face was cut several microns with the target stacked. The glass component attached to the substrate was removed with a high-concentration hydrofluoric acid solution and then washed.
Further, using a parallel plate type CVD apparatus and using a mixed gas of monosilane, ammonia and hydrogen as a film forming gas, silicon nitride is formed on the light-receiving surface side p-type selective emitter layer 4 and the back surface n-type diffusion layer 5 from silicon nitride. An antireflection film 6 was laminated. This film thickness was 70 nm.
Subsequently, silver paste was electrode-printed on the high-concentration diffusion layer 4a on the light-receiving surface side and the back surface side, respectively, dried, and then baked at 750 ° C. for 3 minutes to form the front electrode 7, the back electrode 8, and the bus bar electrode 9.

[Example 2]
Instead of the polysilazane solution, a mixed solution consisting of a polysiloxane modified with a terminal vinyl group and the following crosslinking agent was applied on a silicon substrate and cured by heating to form a polysiloxane film. A solar cell was produced by the method.
In this case, the polysiloxane is represented by the following formula: CH ₂ ═CHSi (CH ₃ ) ₂ O— (Si (CH ₃ ) ₂ O) —Si (CH ₃ ) ₂ CH═CH ₂
And the following formula CH ₃ Si (OH) ₃
I used one.

[Comparative Example 1]
It was produced by the same method as in Example 1 except that the polysilazane film was not formed on the light receiving surface side of the silicon substrate.
That is, in the formation of the p-type diffusion layer, a p-type diffusion layer is formed by directly applying a coating agent containing a boron dopant to the light receiving surface of the silicon substrate 1.

The current-voltage characteristics of the solar cells obtained in Examples and Comparative Examples were measured in a 25 ° C. atmosphere under a solar simulator (light intensity: 1 kW / m ² , spectrum: AM1.5 global). The results are shown in Table 1. In addition, the number in a table | surface is an average value of ten cells made as an experiment in an Example and a comparative example.

  As described above, in the solar cell according to the example, the organosilicon compound film is formed on the side that becomes the p-type diffusion layer of the silicon substrate, and the organosilicon compound film in the region serving as the electrode connection position of the p-type diffusion layer is partially formed. After removing the target and forming an opening in a region that becomes a high-concentration diffusion region, a dopant is applied on the organosilicon compound film, and the dopant is simultaneously diffused into the silicon substrate through the opening and the organosilicon compound film. By forming the p-type selective emitter layer, the p-layer passivation was improved, and the open circuit voltage and the short-circuit current were improved. According to the manufacturing method of the present invention, it is possible to form a p-type selective emitter with a small number of steps.

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Polysilazane film 2a Opening part 3 Boron coating agent 4 p-type selective emitter layer 4a p-type high concentration diffusion layer 4b p-type low concentration diffusion layer 5 n-type diffusion layer 6 Antireflection film 7 Light-receiving surface electrode (finger electrode)
8 Back electrode 9 Bus bar electrode

The present invention is a film made of an organic silicon compound used to suppress diffusion suppression mask dopant diffusion relates to how to form a selective emitter layer on the p-layer.

The present invention has been made in view of the above problems, and can be used to form a p-type selective emitter layer by a simple method, and a p-type selective emitter formation method that can provide a solar cell having high energy conversion efficiency. The purpose is to provide.

Accordingly, the present invention provides a p-type selective emitter formed how below.
[1] a step of forming a polysilazane film or polysiloxane film on the light-receiving surface side of the silicon substrate, an opening in the area to remove the region for forming a high concentration diffusion layer of the polysilazane film or polysiloxane film A step of forming, and then applying a first dopant coating agent so as to cover the polysilazane film or polysiloxane film and the opening, and further heat-treating at 800 to 1100 ° C. to make the polysilazane film or polysiloxane film a silicon-containing inorganic thin film with a to diffuse first dopant in the silicon substrate from the silicon-containing inorganic thin film and the opening, the high-concentration diffusion layer in a portion by diffusing the first dopant through the opening, the silicon-containing inorganic films A step of forming a low-concentration diffusion layer in a portion where the first dopant is diffused through the p-type selection Emitter formation method.
[2] The selective emitter forming method according to [1], wherein a polysilazane solution is applied to a surface to be a light receiving surface of a silicon substrate, and is heated and dried at 80 to 200 ° C. to form the polysilazane film.
[3] A composition containing a reactive polysiloxane having a reactive organic group at its side chain or terminal is applied to the surface to be the light-receiving surface of the silicon substrate, and heat-cured to form the polysiloxane film [1] ] The selective emitter formation method of description.
[ 4 ] The selective emitter forming method according to any one of [1] to [3], wherein the silicon substrate is n-type.
[ 5 ] The method for forming a selective emitter according to any one of [1] to [ 4 ], wherein a film of an organosilicon compound is formed with a thickness of 5 to 300 nm.
[ 6 ] The selective emitter formation method according to any one of [1] to [ 5 ], wherein the first dopant is boron.

Claims (6)

  A step of forming an organosilicon compound film on the light-receiving surface side of the silicon substrate, a step of removing a region where the high concentration diffusion layer is to be formed from the organosilicon compound film, and forming an opening in the region; Next, a first dopant coating agent is applied to cover the film and opening of the organosilicon compound, the first dopant is diffused from the organosilicon compound and the opening to the silicon substrate, and the first dopant is spread from the opening. A method of forming a p-type selective emitter, comprising a step of forming a high concentration diffusion layer in a portion where a dopant is diffused and a low concentration diffusion layer in a portion where the first dopant is diffused through the organosilicon compound film.   2. The selective emitter forming method according to claim 1, wherein the organosilicon compound film is a polysilazane film or a polysiloxane film.   3. The selective emitter forming method according to claim 1, wherein the silicon substrate is n-type.   The method of forming a selective emitter according to any one of claims 1 to 3, wherein the organosilicon compound film is formed to a thickness of 5 to 300 nm.   The selective emitter formation method according to claim 1, wherein the first dopant is boron.   A solar cell comprising a p-type selective emitter layer formed by the selective emitter forming method according to claim 1.

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