WO2017057618A1 - Solar cell element, method for manufacturing same and solar cell module - Google Patents

Abstract

A solar cell element 1 is provided with a first silicon oxide layer 9a disposed on a silicon substrate 2, and a second silicon oxide layer 9b disposed on the first silicon oxide layer 9a with more silicon content relative to oxygen than the first silicon oxide layer 9a. Furthermore, in the solar cell element 1, the surface of the silicon substrate 2 is oxidized to form the first silicon oxide layer 9a, and through a CVD method using monosilane gas and nitrous oxide gas, the second silicon oxide layer 9b is formed on the first silicon oxide layer 9a. Further, a solar cell module 30 is provided with the solar cell element 1.

Description

SOLAR CELL DEVICE, ITS MANUFACTURING METHOD, AND SOLAR CELL MODULE Cross-reference of related applications

This international application claims the priority of Japanese Patent Application No. 2015-190958 (filed on September 29, 2015). The disclosure content of the above Japanese patent application is incorporated into this international application.

The present disclosure relates to a solar cell element, a manufacturing method thereof, and a solar cell module.

A PID (Potential Induced Degradation) phenomenon is known in which sodium ions diffused into a semiconductor substrate of a solar cell element hinder the movement of light-generating carriers and the output of a solar cell module composed of the solar cell element decreases. . In order to reduce the occurrence of this PID phenomenon, it has been proposed to provide an ion diffusion blocking layer on a silicon substrate constituting a solar cell element (see, for example, Patent Document 1 below).

Currently, a solar cell element that can further reduce the occurrence of the PID phenomenon is desired.

JP 2014-110432 A

According to one aspect of the solar cell element of the present disclosure, a first silicon oxide layer disposed on a silicon substrate and a silicon oxide layer disposed on the first silicon oxide layer, the silicon with respect to oxygen rather than the first silicon oxide layer. A second silicon oxide layer having a high content.

In one aspect of the method for manufacturing a solar cell element, the surface of a silicon substrate is oxidized to form the first silicon oxide layer, and the first silicon oxide is formed by a CVD method using monosilane gas and nitrous oxide gas. The second silicon oxide layer is formed on the layer.

Furthermore, one aspect of the solar cell module of the present disclosure includes the solar cell element.

FIG. 1 is a diagram for explaining an example of a solar cell element according to the embodiment. FIG. 1A is a plan view of the solar cell element as viewed from the surface side, and FIG. It is the top view seen from the back side. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is an enlarged cross-sectional view enlarging a part A of FIG. FIG. 4 is a diagram for explaining an example of a method for manufacturing a solar cell element according to the embodiment, and FIGS. 4A to 4G are cross-sectional views of the solar cell element. FIG. 5 is a partial cross-sectional view illustrating a method for forming a first silicon oxide layer constituting an example of the solar cell element according to the embodiment. FIG. 6 is a diagram for explaining an example of the solar cell element according to the embodiment, and is an enlarged cross-sectional view of a portion corresponding to part A in FIG. 2. FIG. 7 is a diagram illustrating an example of the solar cell module according to the embodiment. FIG. 7A is a plan view showing the first surface side of the solar cell module, and FIG. It is a top view which shows the 2nd surface side. FIG. 8 is a view for explaining an example of the solar cell element constituting the solar cell module shown in FIG. 7, and FIG. 8 (a) is a plan view showing a state in which a connecting member is connected to the solar cell element. b) is a cross-sectional view showing a connection state between two solar cell elements. FIG. 9 is an exploded cross-sectional view showing an example of a solar cell panel constituting the solar cell module shown in FIG.

Embodiments of a solar cell element and a solar cell module will be described with reference to the drawings. The drawings are schematically shown.

<Solar cell element>
As shown in FIGS. 1 and 2, the solar cell element 1 includes a silicon substrate 2. The solar cell element 1 has a surface 1a that is a first surface that mainly receives light and a back surface 1b that is a second surface facing the surface 1a.

The silicon substrate 2 also has a surface 2a that is a first surface corresponding to the surface 1a of the solar cell element 1 and a back surface 2b that is a second surface corresponding to the back surface 1b of the solar cell element 1. As the silicon substrate 2, for example, a single crystal silicon substrate or a polycrystalline silicon substrate is used. The silicon substrate 2 contains a dopant element such as boron or gallium and has one conductivity type (for example, p-type) region. The planar shape of the silicon substrate 2 is, for example, a square shape or a rectangular shape having a side of about 100 mm to 180 mm, but is not particularly limited. The thickness of the silicon substrate 2 is, for example, about 150 μm to 250 μm. Further, minute irregularities for reducing the reflectance of light may be provided on the surface 2 a side of the silicon substrate 2. In the following, an example in which a p-type polycrystalline silicon substrate is used as the silicon substrate 2 will be described.

As shown in FIG. 2, the silicon substrate 2 has a reverse conductivity type layer 8 on the surface 2a side. The reverse conductivity type layer 8 is a reverse conductivity type (n-type) region with respect to the one conductivity type region 7 of the silicon substrate 2 and forms a pn junction with the one conductivity type region 7. The reverse conductivity type layer 8 can be formed by diffusing a dopant element such as phosphorus on the surface 2 a side of the silicon substrate 2. On the reverse conductivity type layer 8, a silicon oxide layer 9 (first silicon oxide layer 9a, second silicon oxide layer 9b) and an antireflection layer 11 are arranged in this order.

As shown in FIG. 1 (a), on the surface 1a side of the solar cell element 1, a bus bar electrode 3 and finger electrodes 4 are arranged as surface electrodes. Moreover, as shown in FIG.1 (b), the collector electrode 5 and the connection electrode 6 are arrange | positioned as a back surface electrode at the back surface 1b side.

The bus bar electrode 3 provided on the surface 1a (surface 2a of the silicon substrate 2) side of the solar cell element 1 has a role of further collecting photogenerated carriers (hereinafter referred to as carriers) collected by the finger electrodes 4. The bus bar electrodes 3 have an elongated shape with a width of about 1 mm to 3 mm along the Y-axis direction shown in FIG.

The finger electrode 4 has a role of collecting carriers from the silicon substrate 2 and extends, for example, in the X-axis direction illustrated in FIG. 1A and is connected so as to be substantially orthogonal to the bus bar electrode 3. The finger electrodes 4 have a width of about 50 μm to 200 μm, and a plurality of finger electrodes 4 are formed with an interval of about 1 mm to 8 mm. The bus bar electrode 3 and the finger electrode 4 are formed by, for example, applying a conductive paste mainly composed of silver in a desired shape and then baking it. The thickness of the bus bar electrode 3 and finger electrode 4 after firing is, for example, about 10 μm to 30 μm.

As shown in FIG. 1 (b), a connection electrode 6 is provided on the back surface 1 b side of the solar cell element 1. The connection electrode 6 has a width of about 1 mm to 5 mm, and is arranged in the Y-axis direction illustrated in FIG. 1B at about 2 to 5 at positions almost opposite to the bus bar electrode 3 provided on the surface 1a. . The connection electrode 6 is formed, for example, by applying a conductive paste containing silver as a main component in a desired shape and baking it. The thickness of the connection electrode 6 after firing is about 10 μm to 30 μm.

The collecting electrode 5 collects carriers on the back surface 1 b of the solar cell element 1 and transmits them to the connection electrode 6. The collecting electrode 5 is formed on the substantially entire surface of the back surface 2 b excluding the 0.5 mm to 3 mm width portion in the outer peripheral portion of the back surface 2 b of the silicon substrate 2 and the arrangement portion of the connection electrode 6. The current collecting electrode 5 can be formed by, for example, applying a conductive paste mainly composed of aluminum in a desired shape and then baking it. The thickness of the current collecting electrode 5 is, for example, about 15 μm to 50 μm.

A BSF (Back-Surface-Field) region 10 shown in FIG. 2 forms an internal electric field on the back surface 2b side of the silicon substrate 2, and hardly reduces the photoelectric conversion efficiency due to recombination of minority carriers in the vicinity of the back surface 2b. Have the role of The BSF region 10 has the same conductivity type as the one conductivity type region 7 of the silicon substrate 2, and the dopant element is present at a concentration higher than the concentration of the dopant element doped in the one conductivity type region 7. To do. Further, when the silicon substrate 2 has a p-type, the BSF region 10 diffuses a dopant element such as boron or aluminum to the back surface 2b side, for example. The BSF region 10 is preferably formed so that the concentration of the dopant element is about 1 × 10 ¹⁸ atoms / cm ³ to about 5 × 10 ²¹ atoms / cm ³ .

As shown in FIG. 3 in which the portion A of FIG. 2 is enlarged, a silicon oxide layer 9 is disposed on the reverse conductivity type layer 8 of the silicon substrate 2. The silicon oxide layer 9 is composed of a first silicon oxide layer 9a made of SiOx, and SiOy that is disposed on the first silicon oxide layer 9a and has a higher silicon content with respect to oxygen than silicon oxide in the first silicon oxide layer 9a. And a second silicon oxide layer 9b. Here, if x> y is about 1.8 to 3 in SiOx and y is about 1 to 1.7 in SiOy, as described later, in the second silicon oxide layer 9b, It becomes silicon rich and the conductivity increases. As a result, sodium ions easily move at the interface between the first silicon oxide layer 9a and the second silicon oxide layer 9b and between the second silicon oxide layer 9b and the antireflection layer 11. As a result, the accumulation of sodium ions at the interface is reduced. For this reason, in this embodiment, the amount of sodium ions reaching the silicon surface can be further reduced. Thereby, in this embodiment, generation | occurrence | production of a PID phenomenon can be reduced. The film thickness of the first silicon oxide layer 9a can be about 0.3 nm to 6 nm, or about 0.5 nm to 3 nm. Further, the film thickness of the second silicon oxide layer 9b can be about 8 nm to 50 nm and about 10 nm to 20 nm. In this case, the amount of sodium ions trapped in the second silicon oxide layer 9b can be increased. Thereby, since the second silicon oxide layer 9b has a stronger positive charge, the effect of blocking sodium ions can be further enhanced. Furthermore, the refractive index of the first silicon oxide layer 9a is about 1.4 to 1.5, and the refractive index of the second silicon oxide layer 9b is about 1.6 to 1.7. I also understood that.

The PID phenomenon is said to occur due to the movement of sodium ions released from the glass substrate of the solar cell module to the surface and inside of the silicon substrate 2. The movement of sodium ions into the material is affected by the density and crystal structure of the material in which it is present. For example, sodium ions easily move into the silicon nitride and hardly move into the silicon oxide. Accordingly, sodium ions are less likely to move inside the silicon oxide layer 9 including the first silicon oxide layer 9a and the second silicon oxide layer 9b as compared to the antireflection layer 11 containing silicon nitride. For this reason, since it becomes difficult for sodium ions to enter the first silicon oxide layer 9, it becomes difficult for sodium ions to enter the silicon substrate 2, and the occurrence of the PID phenomenon is reduced.

Further, since the silicon oxide layer 9 includes two layers of the first silicon oxide layer 9a and the second silicon oxide layer 9b, the following effects can be expected. Sodium ions move through fine defects or pinholes or thin portions of the second silicon oxide layer 9b. However, sodium ions can be blocked by the first silicon oxide layer 9a. Further, the second silicon oxide layer 9b contains silicon oxide (SiOy) having a higher silicon content ratio relative to oxygen than the silicon oxide (SiOx) of the first silicon oxide layer 9a. That is, the second silicon oxide layer 9b is in a richer silicon state than the first silicon oxide layer 9a. For this reason, the conductivity of the second silicon oxide layer 9b is increased, and sodium is added at the interface between the first silicon oxide layer 9a and the second silicon oxide layer 9b and at the interface between the second silicon oxide layer 9b and the antireflection layer 11. Ions move easily. Then, accumulation of sodium ions at these interfaces is eliminated, and the amount of sodium ions reaching the surface of the silicon substrate 2 can be further reduced. Thereby, it can be set as the solar cell element which a PID phenomenon does not produce easily.

The second silicon oxide layer 9b is preferably thicker than the first silicon oxide layer 9a. By making the film thickness of the second silicon oxide layer 9b larger than the film thickness of the first silicon oxide layer 9a, the amount of sodium ions trapped in the second silicon oxide layer 9b can be increased. Further, since the second silicon oxide layer 9b has a stronger positive charge, it repels the positive charge of sodium ions, and the action of blocking the movement of sodium ions to the silicon substrate 2 can be further enhanced. it can.

The silicon content with respect to oxygen in the first silicon oxide layer 9a and the second silicon oxide layer 9b is, for example, secondary ion mass spectrometry (SIMS) or X-ray photoelectron spectroscopy (XPS). ray Photoelectron Spectroscopy).

Further, as shown in FIG. 3, the solar cell element 1 is preferably provided with an antireflection layer 11 disposed on the second silicon oxide layer 9b and having a refractive index higher than that of the second silicon oxide layer 9b. The antireflection layer 11 reduces the reflectance of light on the surface 1a of the solar cell element 1 and increases the number of electron-hole pairs generated by light absorption, thereby increasing carriers and increasing the photoelectric of the solar cell element 1. Contributes to improved conversion efficiency. The antireflection layer 11 may be a single layer film such as silicon nitride, titanium oxide, or aluminum oxide, or a laminated film thereof.

By making the refractive index of the antireflection layer 11 larger than that of the second silicon oxide layer 9b, the total refractive index and film thickness of the first silicon oxide layer 9a, the second silicon oxide layer 9b, and the antireflection layer 11 can be reduced. Can be more optimal. Thereby, the effect of preventing reflection of light incident on the solar cell element 1 can be improved. In order to reduce the occurrence of the PID phenomenon, if the refractive index and thickness of the antireflection layer 11 are set within a certain range, a sufficient antireflection effect may not be obtained. In the antireflection layer 11 of the present embodiment, since the first silicon oxide layer 9a and the second silicon oxide layer 9b can be expected to reduce the occurrence of the PID phenomenon, the refractive index of the antireflection layer 11 is higher than that of the second silicon oxide layer 9b. Can be set larger, and the thickness can be set freely. For this reason, the antireflection layer can function effectively. In addition, each refractive index and thickness of the 1st silicon oxide layer 9a, the 2nd silicon oxide layer 9b, and the reflection preventing layer 11 can be measured with an ellipsometer.

In the solar cell element 1, a silicon oxide layer having a positive fixed charge and an antireflection layer 11 having silicon nitride are arranged on the surface of the n-type reverse conductivity type layer 8. Thereby, the effects described below can be expected. Minority carriers are moved away from the interface (the surface of the silicon substrate 2) with the reverse conductivity type layer 8 by the electric field effect of the antireflection layer 11 having a silicon oxide layer and silicon nitride. Thereby, recombination of minority carriers on the surface of the silicon substrate 2 is reduced, and a passivation effect for improving the photoelectric conversion efficiency can be obtained. In particular, since the antireflection layer 11 contains silicon nitride, since the positive fixed charge of silicon nitride is stronger than that of silicon oxide, the photoelectric conversion efficiency of the solar cell element 1 can be further improved. The antireflection layer 11 can be a silicon nitride film (SiNz film (the composition ratio z of N has a width with a center on the stoichiometry of Si ₃ N ₄ )). This silicon nitride film can be manufactured using a monosilane gas, ammonia gas, or the like by a CVD method.

The antireflection layer 11 is preferably thicker than the second silicon oxide layer 9b. Thereby, since it becomes a stronger positive electric charge, the above-mentioned passivation effect can be enlarged more. For example, when the thickness of the second silicon oxide layer 9b is about 10 to 30 nm, the thickness of the antireflection layer 11 made of silicon nitride is about 40 to 100 nm (refractive index is about 1.7 to 2.3). ).

<Method for producing solar cell element>
Next, the manufacturing method of the solar cell element 1 is demonstrated.

First, a silicon substrate 2 is prepared as shown in FIG. The silicon substrate 2 is, for example, a monocrystalline or polycrystalline silicon substrate having a one conductivity type region 7 having a specific resistance of about 0.2 Ω · cm to 2 Ω · cm. When the silicon substrate 2 is a single crystal silicon substrate, it is manufactured by, for example, the FZ (floating zone) method or the CZ (Czochralski) method. When the silicon substrate 2 is a polycrystalline silicon substrate, it is produced by, for example, a casting method. Hereinafter, an example in which a p-type polycrystalline silicon substrate is used as the silicon substrate 2 will be described.

A method for manufacturing the silicon substrate 2 will be described. First, an ingot of polycrystalline silicon is produced by a casting method. Next, the p-type silicon substrate 2 is manufactured by slicing the ingot into a thickness of, for example, about 150 μm to 250 μm using a multi-wire saw or the like. Thereafter, in order to remove the mechanical damage layer and the contamination layer on the cut surface of the silicon substrate 2, the surface is made of an alkaline solution containing sodium hydroxide (NaOH) or potassium hydroxide (KOH), or hydrofluoric acid (HF). Etching with a mixed solution with nitric acid (HNO ₃ ) about several μm, washing and drying.

Thereafter, a texture structure having fine irregularities may be formed on substantially the entire surface 2a of the silicon substrate 2 by using a reactive ion etching (RIE) apparatus. In the present embodiment, for example, while flowing trifluoride methane (CHF ₃ ) at a flow rate of 20 sccm, chlorine (Cl ₂ ) at 50 sccm, oxygen (O ₂ ) at 10 sccm, and sulfur hexafluoride (SF ₆ ) at a flow rate of 80 sccm. Then, dry etching is performed for about 3 minutes under conditions of a reaction pressure of 7 Pa and an RF power for generating plasma of 500 W. Thereafter, the silicon residue on the surface 2a of the silicon substrate 2 is washed and removed.

Next, as shown in FIG. 4B, an n-type reverse conductivity type layer 8 is formed in the surface layer of the silicon substrate 2 on the surface 2a side. The reverse conductivity type layer 8 is formed by applying a thermal diffusion method in which a paste of diphosphorus pentoxide (P ₂ O ₅ ) is applied to the surface 2a of the silicon substrate 2 and thermally diffused, or phosphorus oxychloride in a gas state. It is formed by a vapor phase thermal diffusion method using (POCl ₃ ) as a diffusion source. The reverse conductivity type layer 8 has a thickness of about 0.1 μm to 1 μm, and is formed to have a sheet resistance of about 40Ω / □ to 150Ω / □.

Thereafter, in order to remove the phosphorus glass layer and unnecessary oxide film formed on the surface of the silicon substrate 2, the silicon substrate 2 is immersed in a hydrofluoric acid aqueous solution and then washed with pure water. At the end of the cleaning with pure water, the surface of the silicon substrate 2 is oxidized using ozone to form a first silicon oxide layer 9a on the surface of the silicon substrate 2 as shown in FIG.

Specifically, first, a pipe 21 for introducing an ozone-containing gas is arranged inside a tank 20 made of a fluorine-based resin or polypropylene. The first end of the pipe 21 is connected to an ozone generator that generates an ozone-containing gas containing ozone in the oxygen gas, and the discharge port 22 that is the second end of the pipe 21 is disposed at the bottom of the tank 20. Is done. After putting pure water into this tank 20, ozone-containing gas is discharged from the discharge port 22, and bubbling is performed in pure water. Thereby, the ozone containing water 23 containing ozone is produced.

Next, as shown in FIG. 5, the silicon substrate 2 is immersed in the ozone-containing water 23 during the cleaning. Then, ozone-containing gas bubbles are generated in the ozone-containing water 23 so that the ozone-containing gas 24 hits the surface of the silicon substrate 2 from the discharge port 22 of the pipe 21. The film thickness of the first silicon oxide layer 9a thus formed is about 0.3 nm to 6 nm. At this time, the first silicon oxide layer 9a is formed substantially uniformly without being substantially affected by the texture structure of the silicon substrate 2. For this reason, even if a minute defect, a pinhole, a thin part, etc. have arisen in the 2nd silicon oxide layer 9b formed on the 1st silicon oxide layer 9a, it can block sodium ion more certainly. Further, the formed first silicon oxide layer 9a is a silicon oxide layer with little impurity contamination. For this reason, it is possible to terminate the dangling bonds of silicon atoms of the reverse conductivity type layer 8 by oxygen atoms of the first silicon oxide layer 9a, and to further improve the photoelectric conversion efficiency of the solar cell element 1. .

The formation of the first silicon oxide layer 9a is not limited to the method of immersing the silicon substrate 2 in the ozone-containing water 23 described above. For example, the first silicon oxide layer 9a may be formed by disposing the silicon substrate 2 directly below the ultraviolet lamp and irradiating the silicon substrate 2 with ultraviolet rays. In this case, oxygen in the air changes to ozone by the action of ultraviolet rays. The ozone oxidizes the surface of the silicon substrate 2 to form the first silicon oxide layer 9a. However, in this formation method by ultraviolet irradiation, there may be a case where impurities in the air are included in the formed first silicon oxide layer 9a.

Further, when the reverse conductivity type layer 8 is formed on the back surface 2b side when the reverse conductivity type layer 8 is formed by vapor phase thermal diffusion or the like, the first silicon oxide layer 9a is further formed on the back surface 2b side. In such a case, only the back surface 2b side of the silicon substrate 2 is immersed in a mixed solution of hydrofluoric acid and nitric acid. Thus, the reverse conductivity type layer 8 and the first silicon oxide layer 9a on the back surface 2b side are removed by etching, and the p-type one conductivity type region 7 is exposed on the back surface 2b side. As described above, a pn junction is formed in the silicon substrate 2 by the p-type one conductivity type region 7 and the n-type reverse conductivity type layer 8, and the first silicon oxide layer 9 a is formed on the reverse conductivity type layer 8. Can be formed.

Next, as shown in FIG. 4D, a second silicon oxide layer 9 b is formed on the first silicon oxide layer 9 a on the surface 2 a side of the silicon substrate 2. An ALD (Atomic Layer Deposition) method can be used to form the second silicon oxide layer 9b. In this case, for example, N, N, N ′, N ′, tetraethylsilanediamine (H ₂ Si [N (C ₂ H ₅ ) ₂ ] ₂ ) gas and ozone gas as the oxidizing agent are used as the source gas. be able to. The second silicon oxide layer 9b thus formed is substantially formed from silicon and oxygen. Thereby, movement of sodium ions to the silicon substrate 2 can be blocked by the second silicon oxide layer 9b.

The second silicon oxide layer 9b can also be formed using, for example, a CVD (Chemical Vapor Deposition) method using monosilane gas (SiH ₄ ) and nitrous oxide (N ₂ O) gas. The second silicon oxide layer 9b having a desired refractive index and thickness can be obtained by controlling the flow rate of monosilane gas and nitrous oxide gas and the film formation time.

In this case, the formed second silicon oxide layer 9b contains nitrogen, but the content of this contained nitrogen is less than the content of oxygen. For example, the ratio of the number of atoms of nitrogen and oxygen in the second silicon oxide layer 9b is about 0.3 to 0.5 times that of oxygen. Here, the ratio of the number of atoms of nitrogen and oxygen can be measured by SIMS or XPS.

The refractive index of the first silicon oxide layer 9a is about 1.4 to 1.6, and the refractive index of the antireflection layer 11 is about 1.9 to 2.1. In this case, the refractive index of the second silicon oxide layer 9b can be about 1.7 to 1.8, which is an almost intermediate value. Thereby, the refractive index from the antireflection layer 11 on the outermost surface of the solar cell element 1 to the first silicon oxide layer 9a in contact with the silicon substrate 2 can be gradually lowered at substantially equal intervals, so that the light reflection is further reduced. can do.

Next, as shown in FIG. 4E, an antireflection layer 11 is formed on the second silicon oxide layer 9b. For example, when the antireflection layer 11 made of silicon nitride is formed by a PECVD (Plasma Enhanced Chemical Vapor Deposition) apparatus, the reaction chamber is set to about 400 ° C. to 500 ° C., and silane (SiH ₄ ) and ammonia (NH ₃ ). A high frequency voltage is applied between the electrodes in the reaction chamber while diluting the mixed gas with nitrogen (N ₂ ). Then, the antireflection layer 11 is formed on the second silicon oxide layer 9b by depositing these gases into plasma by glow discharge decomposition. At this time, the flow rate of each gas of monosilane gas, ammonia gas, and nitrogen gas, the film formation time, and the like may be adjusted so that the antireflection layer 11 has a predetermined refractive index and thickness.

In the present embodiment, the second silicon oxide layer 9b and the antireflection layer 11 can both be formed by the CVD method as described above. For this reason, two film formation chambers (first film formation chamber and second film formation chamber) are prepared with an inline-type PECVD apparatus, and the second silicon oxide layer 9b is formed in the first film formation chamber. The antireflection layer 11 may be deposited in the deposition chamber. This makes it difficult to form an oxide film at the interface between the second silicon oxide layer 9b and the antireflection layer 11, and reduces man-hours such as movement between apparatuses and transfer time to an apparatus-specific transport tray during mass production. it can.

Next, as shown in FIG. 4 (f), the surface-side conductive paste 13 to be the bus bar electrode 3 and the finger electrode 4 is applied and disposed on the surface 2 a of the silicon substrate 2. As the surface-side conductive paste 13, a paste containing silver as a main component and containing about 70% by mass to 85% by mass in a conductive paste and further kneaded with glass frit, an organic vehicle, or the like is used. The organic vehicle is obtained, for example, by adding a resin component used as a binder to an organic solvent. As the binder, an acrylic resin or an alkyd resin can be used in addition to a cellulose resin such as ethyl cellulose. As the organic solvent, for example, diethylene glycol monobutyl ether acetate, terpineol or diethylene glycol monobutyl ether is used. The organic vehicle may be contained in an amount of about 5% by mass to 20% by mass in the conductive paste. As the glass frit component, lead glass such as SiO ₂ —Bi ₂ O ₃ —PbO or Al ₂ O ₃ —SiO ₂ —PbO can be used as a glass material. As other glass materials, non-lead glass such as B ₂ O ₃ —SiO ₂ —Bi ₂ O ₃ or B ₂ O ₃ —SiO ₂ —ZnO can also be used. The glass frit may be about 2% by mass to 15% by mass in the conductive paste. As a method of arranging the surface-side conductive paste 13, the surface-side conductive paste 13 to be the finger electrode 4 is arranged on the first texture structure region 11 by using a printing method using screen plate making. Apply. After this application, the solvent is dried by drying at a predetermined temperature.

Similarly, the back surface side first conductive paste 14 for the connection electrode 6 is disposed on the back surface 2 b of the silicon substrate 2. As the back side first conductive paste 14, the same conductive paste as the above-described front side conductive paste 13 can be used. After arrange | positioning the back surface side 1st electrically conductive paste 14, it is made to dry at predetermined temperature and a solvent is evaporated.

Next, as shown in FIG. 4G, the back side second conductive paste 15 for the back side collecting electrode 5 is disposed. As the second conductive paste 15, for example, an aluminum paste containing a metal powder containing aluminum as a main component, glass frit, and an organic vehicle is used. As the coating method, a printing method or the like can be used. After applying the conductive paste in this manner, the solvent is evaporated by drying at a predetermined temperature.

Next, the silicon substrate 2 on which the front-side conductive paste 13, the back-side first conductive paste 14, and the back-side second conductive paste 15 are placed is put into a firing furnace, and these are simultaneously heated to the maximum temperature in the firing furnace. Is about 750 ° C. to 900 ° C., and the maximum temperature is maintained for about 0.1 seconds to several tens of seconds. As a result, the glass frit melted during firing reacts with the outermost surface of the silicon substrate 2 and adheres to form an electrical contact between each electrode and the silicon substrate 2 and increase the mechanical adhesive strength. it can. At this time, the surface-side conductive paste 13 fires through the antireflection layer 11 to form bus bar electrodes 3 and finger electrodes 4 that are in direct contact with the silicon substrate 2. Further, by this firing, the back side first conductive paste 14 becomes the connection electrode 6, and the back side second conductive paste 15 becomes the current collecting electrode 5. At this time, the BSF region 10 is formed by diffusing aluminum into the silicon substrate 2 simultaneously with the formation of the collecting electrode 5. The solar cell element 1 shown in FIGS. 1 and 2 is completed through the above steps.

In addition, the manufacturing method of the solar cell element 1 which concerns on this embodiment is not limited to said thing. For example, the firing step may be sequentially performed after the surface-side conductive paste 13, the back-side first conductive paste 14, and the back-side second conductive paste 15 are arranged. Alternatively, the front-side conductive paste 13 and the back-side first conductive paste 14 may be performed simultaneously, and further baked after the back-side second conductive paste 15 is disposed. As another method, after the front surface side conductive paste 13 is fired, the back side first conductive paste 14 and the back side second conductive paste 15 may be fired simultaneously. Further, the bus bar electrode 3 and the connection electrode 6 may be formed of a conductive paste mainly composed of silver and copper in addition to the above-described conductive paste mainly composed of silver.

<Other Embodiment of Solar Cell Element>
The solar cell element 1 according to this embodiment further includes an aluminum oxide layer 12 disposed between the first silicon oxide layer 9a and the second silicon oxide layer 9b as shown in FIG. By further providing the aluminum oxide layer 12, sodium ions can be more reliably blocked even when fine defects, pinholes, thin portions, or the like are generated in the second silicon oxide layer 9b. As a method of forming the aluminum oxide layer 12, for example, an ALD method excellent in coverage of fine irregularities on the surface of the silicon substrate 2 may be used.

In the formation of the aluminum oxide layer 12 by the ALD method, first, the silicon substrate 2 on which the first silicon oxide layer 9a shown in FIG. 4C is formed is placed in the chamber of the film forming apparatus. And the process from the process A shown below to the process D is repeated in multiple times in the state which heated the silicon substrate 1 at the temperature range of 100 to 250 degreeC. Thereby, the aluminum oxide layer 12 having a desired thickness is formed. The content of each process from the process A to the process D is as follows.

[Step A] An aluminum material such as trimethylaluminum (TMA) for forming aluminum oxide is supplied onto the silicon substrate 1 in the chamber of the film forming apparatus together with a carrier gas such as Ar gas or nitrogen gas. As a result, the aluminum material is adsorbed around the entire periphery of the silicon substrate 1. The time for which TMA is supplied may be about 15 to 3000 milliseconds, for example.

Note that at the start of the process A, the surface of the silicon substrate 1 is preferably terminated with an OH group. By making the surface of the silicon substrate 1 have a Si—O—H structure, a covalent bond is easily formed at the interface between the surface of the silicon substrate 1 and the formed aluminum oxide film. Thereby, the bonding strength between the surface of the silicon substrate 1 and the aluminum oxide film can be improved, and the reliability of the solar cell element 10 can be further improved. The Si—O—H structure can be formed, for example, by treating the silicon substrate 1 with dilute hydrofluoric acid and then washing with pure water.

[Step B] The inside of the chamber of the film forming apparatus is cleaned with nitrogen gas, and the aluminum material in the chamber is removed. Furthermore, aluminum materials other than components chemically adsorbed at the atomic layer level are removed from the aluminum materials physically and chemically adsorbed on the silicon substrate 1. The time for purifying the inside of the chamber with nitrogen gas may be, for example, about 1 second to several tens of seconds.

[Step C] By supplying an oxidizing agent such as water or ozone gas into the chamber of the film forming apparatus, the alkyl group contained in the TMA is removed and replaced with an OH group. Thereby, an atomic layer of aluminum oxide is formed on the silicon substrate 1. Note that the time during which the oxidizing agent is supplied into the chamber may be about 500 milliseconds to 1500 milliseconds. Further, hydrogen is supplied into the chamber together with the oxidizing agent, so that hydrogen atoms are more easily contained in the formed aluminum oxide film.

[Step D] The inside of the chamber of the film forming apparatus is cleaned with nitrogen gas, and the oxidizing agent in the chamber is removed. At this time, for example, the oxidizing agent that did not contribute to the reaction during the formation of atomic layer level aluminum oxide on the silicon substrate 1 is removed. Note that the time required for purifying the chamber with nitrogen gas may be, for example, about 1 second to several tens of seconds.

Thereafter, an aluminum oxide film having a desired film thickness (for example, about 10 nm to 200 nm) is formed by repeating a series of steps from step A to step D a plurality of times.

Here, although the case where aluminum oxide is formed using TMA as the aluminum material is shown, it goes without saying that other materials may be used as the aluminum material. For example, any material that has an appropriate vapor pressure (for example, 100 Pa or more) as a gas supply reduction at the raw material supply temperature (in the range from −20 ° C. to 120 ° C.) and can be supplied in a gaseous state in the chamber may be used. As the aluminum raw material, for example, triethylaluminum (TEA) can be used. The material that can be supplied in a gaseous state may be supplied after being diluted with nitrogen gas, carbon dioxide gas or the like as a carrier gas. By adjusting the gas species of the source gas and the carrier gas and the mixing ratio thereof, the content of the constituent elements in the formed film can be adjusted optimally.

The aluminum oxide layer may also be formed on the back surface 2b of the silicon substrate 2. Since the aluminum oxide layer has a negative fixed charge, the aluminum oxide layer becomes a passivation film having a negative fixed charge with respect to the back surface 2b. Then, electrons which are minority carriers move away from the interface between the back surface 2b and the passivation film 4 due to the electric field effect. As a result, in the solar cell element 1, minority carrier recombination is reduced, and the photoelectric conversion efficiency can be improved.

<Solar cell module>
As shown in FIGS. 7A and 7B, the solar cell module 30 according to this embodiment is disposed on the solar cell panel 33 having the plurality of solar cell elements 1 and the outer peripheral portion of the solar cell panel 33. It has a frame 34. The solar cell module 30 has a first surface 30a (see FIG. 7A) that is a surface that mainly receives light, and a second surface 30b that corresponds to the back surface of the first surface 30a (FIG. 7B). See). And the solar cell module 30 has the terminal box 35 in the 2nd surface 30b, as shown in FIG.7 (b). The terminal box 35 is wired with an output cable 36 for supplying power generated by the solar cell module 30 to an external circuit.

The solar cell element 1 constituting the solar cell module 30 only needs to be that of the above-described embodiment. Adjacent solar cell elements 1 are electrically connected by a connection conductor 32 as shown in FIGS. For example, the connection conductor 32 may be a copper or aluminum metal foil having a thickness of about 0.1 mm to 0.3 mm. This metal foil has a surface coated with solder. This solder is provided by plating or dipping so as to have an average thickness of, for example, about 5 μm to 30 μm. The width of the connection conductor 32 may be equal to or smaller than the width of the bus bar electrode 3 of the solar cell element. As a result, the connection conductor 32 can make it difficult to prevent the solar cell element 1 from receiving light. Further, the connection conductor 32 may be connected to substantially the entire surface of the bus bar electrode 3 and the connection electrode 6. Thereby, the resistance component of the solar cell element 1 can be reduced. Here, when the silicon substrate 2 having a connection conductor 32 of about 156 mm square is used, the connection conductor 32 may have a width of about 1 mm to 3 mm and a length of about 260 mm to 310 mm.

As shown in FIG. 8A, in the connection conductor 32 connected to one solar cell element 1, one connection conductor 32a is soldered to the bus bar electrode 3 on the surface 1a of the solar cell element 1. The other connection conductor 32 b is soldered to the connection electrode 6 on the back surface of the solar cell element 1.

Moreover, as shown in FIG.8 (b), the adjacent solar cell element 1 (solar cell element 1S, 1T) connects the other end part of the connection conductor 32 connected to the bus-bar electrode 3 of the surface 1a of the solar cell element 1S. It connects by soldering to the connection electrode 6 of the back surface 1b of the solar cell element 1T. By repeating such a connection to a plurality (for example, about 5 to 10) of solar cell elements 1, a solar cell string in which the plurality of solar cell elements 1 are linearly connected in series is formed.

Next, a plurality of solar cell strings (for example, about 2 to 10) are prepared and aligned approximately parallel with a predetermined interval of about 1 mm to 10 mm. Then, the solar cell elements 1 at each end of the solar cell string are connected to each other by soldering or the like with the lateral wiring 37. The external lead-out wiring 42 is connected to the solar cell element 1 to which the lateral wiring 37 of the solar cell strings on both ends is not connected.

Next, a translucent substrate 38, a front surface side filler 39, a back surface side filler 40, and a back surface material 41 are prepared. As the translucent substrate 38, glass is used. Here, as the glass, for example, white plate glass, tempered glass, double tempered glass, or heat ray reflective glass having a thickness of about 3 mm to 5 mm is used.

The front-side filler 39 and the back-side filler 40 are each made of an ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA) or polyvinyl butyral (PVB), and have a thickness of about 0.4 mm to 1 mm by an extruder or the like. What was shape | molded in the sheet form is used. These are heated and pressed under reduced pressure by a laminating apparatus, and are softened and fused to be integrated with other members.

The back material 41 has a role of reducing moisture intrusion from the outside. As the back material 41, for example, a weather-resistant fluorine-based resin sheet sandwiching an aluminum foil, a polyethylene terephthalate (PET) sheet on which alumina or silica is deposited, and the like are used. The back material 41 may use glass or polycarbonate resin when incident on light from the second surface 30b side of the solar cell module 30 is used for photovoltaic power generation.

Next, as shown in FIG. 9, after the surface-side filler 39 is disposed on the translucent substrate 38, the solar cell element 1, the back-side filler 40, and the back-surface material 41 connected as described above are sequentially stacked. To produce a laminate.

Next, this laminate is set in a laminator. And the solar cell panel 33 is producible by heating at 100 to 200 degreeC, for example for about 15 minutes to 1 hour, pressurizing under reduced pressure.

Finally, as shown in FIGS. 7 (a) and 7 (b), the solar cell module 30 is attached to the outer periphery of the solar cell panel 33 as necessary by attaching the terminal box 35 to the frame 34 or the second surface 30b side. Complete. Thus, by providing the above-described solar cell element 1, it is possible to provide the solar cell module 30 in which the occurrence of the PID phenomenon is reduced.

Hereinafter, examples and comparative examples will be described.

<Production of Solar Cell Element of Example>
As shown in FIG. 4A, boron having a specific resistance value of about 1 Ω · cm, a side of about 156 mm, and a thickness of about 200 μm, produced by a casting method, as the semiconductor substrate 2. A p-type polycrystalline silicon substrate 2 doped with is prepared.

The silicon substrate 2 was etched to a depth of about 8 μm to 13 μm from the surface using a sodium hydroxide (NaOH) aqueous solution, and then a fine texture was formed on the surface 2a side using an RIE apparatus.

Thereafter, an n-type region was formed on the entire surface of the silicon substrate 2 by vapor phase thermal diffusion using phosphorus oxychloride (POCl ₃ ) as a diffusion source. This n-type region was formed to have a sheet resistance of about 50Ω / □ to 100Ω / □. Thereafter, the entire silicon substrate 2 was immersed in a hydrofluoric acid solution to remove the phosphorus glass and the oxide layer on the surface, and washed with pure water.

Next, the first silicon oxide layer 9a was formed on the surface of the silicon substrate 2 as follows. First, a polypropylene pipe 21 for introducing an ozone-containing gas was disposed inside a tank 20 made of polypropylene and having a width of 30 cm, a height of 35 cm, and a depth of about 40 cm. The first end of the pipe 21 was connected to an ozone generator, and the discharge port 22 as the second end was disposed at the bottom of the tank 20. As the ozone generator, one that generates an ozone-containing gas containing about 170 g / m ³ to 230 g / m ³ of ozone in oxygen gas was used. After putting about 25 liters of pure water into this tank 20, ozone-containing gas is discharged from the discharge port 22 about 1 liter to 3 liters per minute and bubbled in pure water for about 7 to 10 minutes, thereby containing ozone. Water 23 was produced. Thereafter, the entire silicon substrate 2 was immersed in the ozone-containing water 23 in succession to the cleaning operation with pure water after removing the phosphorous glass and the oxide layer on the surface. During this immersion, the ozone-containing gas was discharged from about 1 liter to 3 liters per minute so that the ozone-containing gas 24 hits the surface of the silicon substrate 2 from the discharge port 22 of the pipe 21. The silicon substrate 2 was held for about 1 minute in a state where the ozone-containing gas was bubbled in the ozone-containing water 23, and then pulled out from the ozone-containing water 23 and dried. Thereby, the first silicon oxide layer 9 a was formed on the surface of the silicon substrate 2.

Thereafter, only the back surface 2b side of the silicon substrate 2 is immersed in a mixed solution of hydrofluoric acid and nitric acid to remove the first silicon oxide layer 9a and the n-type region on the back surface 2b side, and then the silicon substrate 2 is washed. , Dried. As a result, a first silicon oxide layer 9a was formed on the reverse conductivity type layer 8 on the surface 2a side of the silicon substrate 2 as shown in FIG. The composition of the formed first silicon oxide layer 9a is SiOx (the value of x is about 2.2 to 2.5), the film thickness is about 1 nm to 2 nm, and the refractive index is 1.4 to 1. It was about 6. The film thickness and refractive index were measured with an ellipsometer. The film thickness and refractive index described below were also measured in the same manner.

Next, as shown in FIG. 4D, a second silicon oxide layer 9 b was formed on the first silicon oxide layer 9 a on the surface 2 a side of the silicon substrate 2. The second silicon oxide layer 9b was formed using a PECVD apparatus using monosilane gas (SiH ₄ ) and nitrous oxide (N ₂ O) gas. The composition of the formed second silicon oxide layer 9b is SiOy (the value of y is about 1.0 to 1.2), the film thickness is about 10 nm to 18 nm, and the refractive index is 1.7 to 1. It was about 8. Further, the formed second silicon oxide layer 9b contains nitrogen, and the ratio of the number of atoms of nitrogen and oxygen in the second silicon oxide layer 9b is 0.4 to 0. It was about 45 times. Here, the ratio of the number of atoms of nitrogen and oxygen was measured by SIMS.

Next, as shown in FIG. 4E, on the second silicon oxide layer 9b on the surface 2a side of the silicon substrate 2, an antireflection layer 11 made of silicon nitride is formed by monosilane gas (SiH ₄ ) and ammonia gas (NH ₃ ) Using a PECVD apparatus. The formed antireflection layer 11 had a refractive index of about 2.1 to 2.2 and a thickness of about 50 nm to 80 nm.

Next, as shown in FIG. 4 (f), the surface-side conductive paste 13 for forming the bus bar electrode 3 and the finger electrode 4, which are electrodes on the surface 2 a side, was applied and arranged. As the surface-side conductive paste 13, a paste containing silver as a main component and containing glass frit, an organic vehicle, and the like was used. And the surface side conductive paste 13 was apply | coated to the thickness of about 20 micrometers-30 micrometers using the screen printing method in the shape as shown to Fig.1 (a), and it dried after that.

Furthermore, the back side first conductive paste 14 for forming the connection electrode 6 was disposed on the back side 2b of the silicon substrate 2 as follows. The back side first conductive paste 14 was the same conductive paste as the above-mentioned front side conductive paste 13. 1B is applied to the back surface 2b of the silicon substrate 2 to a shape as shown in FIG. 1B on the back surface 2b of the silicon substrate 2 to a thickness of about 20 μm to 30 μm. Drying was performed.

Next, as shown in FIG. 4G, the back side second conductive paste 15 for forming the back side collecting electrode 5 was arranged as follows. As the second conductive paste 15, for example, an aluminum paste containing a metal powder mainly composed of aluminum, glass frit, and an organic vehicle was used. Then, using a screen printing method, the second conductive paste 15 was applied to a thickness of about 40 μm to 50 μm, and then dried.

Next, the silicon substrate 2 on which the surface-side conductive paste 13, the back-side first conductive paste 14, and the back-side second conductive paste 15 were placed was put into a firing furnace. These conductive pastes were simultaneously fired at a maximum temperature of about 730 ° C. to 760 ° C. for several seconds at the maximum temperature in a firing furnace. Through the above steps, the solar cell element 1 of the example was completed.

<Production of comparative solar cell element>
In the production of the comparative solar cell element, in the production of the solar cell element of the above example, the formation of the first silicon oxide layer 9a shown in FIG. 4C and the second silicon oxide layer shown in FIG. The antireflection layer 11 made of silicon nitride was formed directly on the reverse conductivity type layer 8 on the surface 2a side of the silicon substrate 2 without forming the 9b. The method for forming the antireflection layer 11 is the same as in the example. The refractive index of the formed antireflection layer 11 was about 2.1 to 2.2, which was the same as that of the example. However, since the first silicon oxide layer 9a and the second silicon oxide layer 9b are not provided in the comparative example, the deposition time is extended and the thickness of the antireflection layer 11 is set to about 70 nm to 90 nm. The other steps were produced using the same materials and process conditions as those for producing the solar cell element of the above example.

<Production of solar cell module>
Next, two types of solar cell modules using the solar cell elements of Examples and Comparative Examples were produced. First, the solar cell string which comprises a solar cell module was produced as follows. Seven solar cell elements of Examples and Comparative Examples were prepared. And as shown in FIG.8 (b), two types of solar cell strings using the solar cell element of an Example and a comparative example which connected the solar cell elements in series by soldering using the connection conductor 32, and were connected. Was made.

Furthermore, six solar cell strings prepared in this way were prepared for manufacturing solar cell modules for Examples and Comparative Examples. The six solar cell strings are aligned substantially parallel to each other, and the lateral wiring 37 and the external lead-out wiring 42 as shown in FIG. 8 are soldered to the solar cell elements at the end of each solar cell string. Connected by attaching.

Thereafter, as shown in FIG. 9, after the surface-side filler 39 is disposed on the translucent substrate 38, the six solar cell strings, the back-side filler 40, and the back-surface material 41 connected to each other are sequentially stacked. Thus, a laminate was produced. And this solar cell panel 33 was produced by setting this laminated body to a laminating apparatus, and heating and pressing at about 100 to 160 degreeC for about 20 minutes, pressurizing under reduced pressure.

Next, a frame 34 made of aluminum is attached to the outer peripheral portion of the solar cell panel 33, a terminal box 35 is disposed on the second surface 30b side, and the solar cell module 21 using the solar cell element of the example and the comparative example. A solar cell module using a solar cell element was completed.

<PID resistance test>
Next, a PID resistance test was performed on these solar cell modules. In each solar cell module, in a state where the positive electrode terminal and the negative electrode terminal in the terminal box 24 are short-circuited, the space between the electrode terminal and the frame 23 attached to the outer peripheral portion of the solar cell panel 22 is approximately. A voltage of 1000 V was applied. Then, the output characteristics of each solar cell module are measured, and the change in the deterioration rate with the output (Pmax) over time (how many percentages have deteriorated over time when the initial characteristics are taken as 100%) %) Is measured). This output characteristic was measured in accordance with Japanese Industrial Standard JIS C 8914.

As a result, the output value of the solar cell module using the solar cell element of the example is about 0.2% lower than the initial output value even after 300 hours have passed (the maintenance ratio from the initial output value is 99. Only 8%). On the other hand, in the solar cell module using the solar cell element of the comparative example, an output decrease of about 2% (maintenance rate from the initial output value was about 98%) was observed after 300 hours.

From the above, in the solar cell module using the solar cell element of the example, it was confirmed that the resistance to PID was improved with respect to the solar cell module using the solar cell element of the comparative example.

1: Solar cell element 1a: Front surface 1b: Back surface 2: Silicon substrate 2a: Front surface 2b: Back surface 3: Busbar electrode 4: Finger electrode 5: Current collecting electrode 6: Connection electrode 7: One conductivity type region 8: Reverse conductivity type region (Reverse conductivity type layer)
9: Silicon oxide layer 9a: First silicon oxide layer 9b: Second silicon oxide layer 10: BSF region 11: Antireflection layer 12: Aluminum oxide layer 13: Front side conductive paste 14: Back side first conductive paste 15 : Back side second conductive paste 20: Tank 21: Pipe 22: Discharge port 23: Ozone-containing water 24: Ozone-containing gas 30: Solar cell module 30a: First surface 30b: Second surface 32: Connection conductor 33: Sun Battery panel 34: Frame 35: Terminal box 36: Output cable 37: Lateral wiring 38: Translucent substrate 39: Front side filler 40: Back side filler 41: Back side material 42: External lead-out wiring

Claims (11)

1. A first silicon oxide layer disposed on a silicon substrate;
   A solar cell element comprising: a second silicon oxide layer disposed on the first silicon oxide layer and having a higher silicon content relative to oxygen than the first silicon oxide layer.
2. The solar cell element according to claim 1, wherein the second silicon oxide layer contains nitrogen.
3. The solar cell element according to claim 1 or 2, wherein a thickness of the second silicon oxide layer is larger than a thickness of the first silicon oxide layer.
4. The solar cell element according to any one of claims 1 to 3, further comprising an antireflection layer disposed on the second silicon oxide layer and having a higher refractive index than the second silicon oxide layer.
5. The solar cell element according to claim 4, wherein the antireflection layer contains silicon nitride.
6. The solar cell element according to claim 4 or 5, wherein the thickness of the antireflection layer is thicker than the thickness of the second silicon oxide layer.
7. The solar cell element according to any one of claims 1 to 6, wherein the second silicon oxide layer contains nitrogen, and the content of nitrogen is less than the content of oxygen.
8. The solar cell element according to any one of claims 1 to 7, further comprising an aluminum oxide layer positioned between the first silicon oxide layer and the second silicon oxide layer.
9. A method for manufacturing a solar cell element according to any one of claims 1 to 8,
   Oxidizing the surface of the silicon substrate to form the first silicon oxide layer;
   A method for manufacturing a solar cell element, wherein the second silicon oxide layer is formed on the first silicon oxide layer by a CVD method using monosilane gas and nitrous oxide gas.
10. The method for manufacturing a solar cell element according to claim 9, wherein the first silicon oxide layer is formed by immersing the surface of the silicon substrate in water containing ozone.
11. A solar cell module comprising the solar cell element according to any one of claims 1 to 8.

Images