JP5664591B2 - Solar cell and manufacturing method thereof - Google Patents

Description

  The present invention relates to an inexpensive solar cell having high photoelectric conversion efficiency and a method for manufacturing the same.

  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. Further, it is classified into a single crystal solar cell and a polycrystalline solar cell.

  As an example, FIG. 1 shows an overview of the light receiving surface of a pn junction solar cell using a p-type semiconductor substrate, and FIG. 2 shows an overview of the back surface. On the light receiving surface, finger electrodes 102 for collecting photoexcited carriers are provided at intervals of several millimeters, and two to four bus bar electrodes 101 for collecting carriers from the finger electrodes are provided. Silver (Ag) is often used for the light-receiving surface electrode from the viewpoint of conductivity. On the back surface, aluminum (Al) 202 is formed on almost the entire surface, and 2 to 4 bus bar electrodes 201 for current collection are provided.

An overview of the cross section is shown in FIG. A thin diffusion layer 303 opposite to the conductivity type of the substrate is provided on the light receiving surface, and a silicon nitride (SiNx) film or a silicon oxide (SiO ₂ ) film is often formed thereon as the antireflection film 302. Reference numeral 301 denotes a finger electrode for collecting a light receiving surface, and reference numeral 305 denotes Al provided as a back electrode.

  In addition, a double-sided solar cell in which an opening is provided between the back electrodes and light is also taken from the back surface has higher photoelectric conversion efficiency than the cell having the structure shown in FIG. The light receiving surface structure is the same as in FIG. 1, but the back surface structure is different. A rear view is shown in FIG. Current collecting electrodes 402 are provided at intervals of several mm on the back surface, and Ag is often used for the back surface electrode from the viewpoint of conductivity.

An overview of a cross section of a double-sided light receiving solar cell is shown in FIG. The light receiving surface structure is the same as in FIG. 1, but a current collecting electrode 506 is locally provided on the back surface. The region other than the back electrode is protected (passivated) by an insulating film such as a SiNx film or a SiO ₂ film, or a film 505 in which these layers are stacked.

  When mass-producing solar cells such as those described above, it is effective for investigation of manufacturing history and the like to mark the cell itself with identification symbols and numbers such as date of manufacture. As this method, a method of performing individual identification of a cell by changing an electrode shape is disclosed (for example, Japanese Utility Model Laid-Open No. 05-093054 (Patent Document 1)). However, this method is not preferable because it consumes an electrode material more than necessary and causes problems such as reducing the light receiving area.

  For this reason, a method of directly engraving the cell itself with a laser or the like is widely used, and is known, for example, in Japanese translations of PCT publication No. 2009-528687 (Patent Document 2).

Japanese Utility Model Publication No. 05-093054 Special table 2009-5286687

  However, the direct marking method on the cell using a laser or the like after forming the cell easily damages the cell surface and easily causes recombination of the generated carriers. Further, Patent Document 2 is a method of marking at the initial stage of the cell forming process. In this case, however, the effective light receiving area is reduced, and both of them cause deterioration of cell characteristics. In addition, printing is irrelevant to the functions necessary for power generation, and the aesthetics are impaired. In particular, in the case of a double-sided light-receiving solar cell, both surfaces of the substrate are exposed to the outside, and thus it is necessary to avoid giving the pattern unnecessary for power generation as much as possible.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a solar cell in which identification information of the solar cell is marked and a manufacturing method thereof without deteriorating aesthetics and without deteriorating cell characteristics. And

In order to achieve the above object, the present invention provides the following solar battery cell and manufacturing method thereof.
A solar cell comprising a silicon substrate having a pn junction in [1] one surface and an electrode comprising a bus bar electrode front and back surfaces are formed on each of the silicon substrate, the pn junction formed of the silicon substrate It has a surface layer directly below the bus bar electrode on the opposite side of the surface and a portion where a specific metal impurity is locally diffused as an individual identification information portion of a cell observed as a dark portion by an electric field excitation light emission (EL) method Solar cell.
[2] The solar battery cell according to [1], wherein the metal impurity is Fe.
[3] The solar cell according to [1] or [2], wherein the number of individual identification information portions of the cell is 1 to 40.
[4] The solar cell according to any one of [1] to [3], wherein a size of the individual identification information portion of the cell on the surface of the silicon substrate is 2 to 20 mm.
[ 5 ] The solar cell according to any one of [1] to [ 4 ], wherein the arrangement pattern of the individual identification information section of the cell indicates individual identification information of the solar cell.
A silicon substrate having a pn junction in [6] one surface, a method of manufacturing a solar cell comprising an electrode comprising a front and back surface bus bar electrodes formed on each of the silicon substrate, a specific metal impurities A thermal diffusion process is performed in a state where the silicon substrate is attached to a position directly below the bus bar electrode on the surface opposite to the surface forming the pn junction, and the metal impurity is formed on the surface layer and the local surface of the silicon substrate. A method for manufacturing a solar cell, comprising: forming an individual identification information portion of a cell observed as a dark portion by an electric field excitation light emission (EL) method on a silicon substrate surface.
[ 7 ] The method for producing a solar battery cell according to [ 6 ], wherein the metal impurity is Fe.
[ 8 ] The attachment of the metal impurity to the silicon substrate surface is performed by bringing a member made of the metal impurity into contact with a predetermined position of the silicon substrate surface. [ 6 ] or [ 7 ] A method for producing a solar battery cell.
[ 9 ] Any one of [6] to [8] , wherein the thermal diffusion treatment is performed in combination with a heat treatment for forming a diffusion layer to be the pn junction or a thermal oxidation treatment before forming the antireflection film. The manufacturing method of the photovoltaic cell of crab.
[10] The method for manufacturing a solar cell according to any one of [6] to [9], wherein the thermal diffusion treatment is performed at 1,000 ° C. or lower.

  According to the present invention, the individual identification information portion of the cell is locally arranged with the minimum necessary size, so that the substrate surface is not damaged and the characteristics as a solar cell are not deteriorated. When the solar cell is caused to emit light by the light emission (EL) method, the individual identification information portion of the cell having a predetermined pattern is observed as a dark portion at a predetermined position on the silicon substrate, so that the individual identification of the solar cell is possible. Further, since the individual identification information part of the cell is usually not visible with the naked eye, the aesthetic appearance is not impaired.

It is a general-view figure which shows the structural example by the side of the light-receiving surface of the pn junction type photovoltaic cell used as the premise of the photovoltaic cell which concerns on this invention. It is a general-view figure which shows the structural example by the side of the back surface of the pn junction type photovoltaic cell used as the premise of the photovoltaic cell which concerns on this invention. It is sectional drawing which shows the structural example of the pn junction type photovoltaic cell used as the premise of the photovoltaic cell which concerns on this invention. It is a general-view figure which shows the structural example by the side of the back surface of the high efficiency solar cell used as the premise of the photovoltaic cell which concerns on this invention. It is sectional drawing which shows the structural example of the high efficiency solar cell used as the premise of the photovoltaic cell which concerns on this invention. It is sectional drawing which shows the structural example of the photovoltaic cell which concerns on this invention. It is sectional drawing which shows an example of the manufacturing method of the photovoltaic cell which concerns on this invention, (a) is the state which provided the metal impurity to the silicon substrate, (b) is the state which formed the individual identification information part of the emitter layer and the cell (C) shows a state in which an antireflection film and a back electrode are formed, and (d) shows a state in which a light receiving surface electrode is formed. It is a perspective view which shows the structural example of the jig | tool for individual identification information part formation of the cell used with the manufacturing method of the photovoltaic cell concerning this invention.

Below, the structure of the photovoltaic cell which concerns on this invention, and its manufacturing method is demonstrated.
FIG. 6 is a cross-sectional view showing a configuration example of a solar battery cell according to the present invention.
As shown in FIG. 6, the solar cell of the present invention includes a first conductivity type silicon substrate 601 and a conductivity type opposite to the first conductivity type provided on the light receiving surface side of the silicon substrate 601 (second conductivity type). An emitter layer 603 which is a high concentration selective diffusion layer, an antireflection film 605 provided on the emitter layer 603, a light receiving surface electrode 607 provided on the antireflection film 605, and a non-light receiving surface (back surface) of the silicon substrate 601. And a back surface electrode 606 provided on the non-light-receiving surface side of the silicon substrate 601 and a cell individual identification information portion 604 provided in a state where specific metal impurities are diffused in the silicon substrate 601.

  Here, the cell individual identification information portion 604 is a region observed as a dark portion by an electric field excitation light emission (EL) method, and is locally arranged in a predetermined pattern on the back surface of the silicon substrate 601.

  The electric field excitation light emission method (hereinafter referred to as EL method) is a method for detecting a light emission state when a forward voltage is applied to a silicon substrate having a pn junction and an electrode. For example, in the case of a silicon solar cell. The probe is pressed against the back surface bus bar electrode and the light receiving surface bus bar electrode, a voltage of several hundred mV to several V is applied, and light emission with a wavelength near 1,100 nm is detected by a CCD (Charge Coupled Device) camera or the like. .

  At this time, a portion where normal light emission is present in the silicon substrate 601 is observed as a bright portion, and a portion where the minority carrier lifetime of the silicon substrate 601 is low is observed as a dark portion where light emission is small.

  The cell identification information portion 604 is formed on the silicon substrate 601 with Fe, Au, Pt, Ni, S, Mn, Ag, Co, Zn, Cu, Ta, Mo, Nb, Zr, W, Ti, V, Cr, Al. It is preferable that any specific metal impurity such as the above is thermally diffused (metal contamination site), and Fe is suitable as the metal impurity used here. The individual identification information part 604 of the cell can be said to be an area where the silicon substrate 601 is intentionally contaminated.

  When a specific metal impurity such as iron (Fe) diffuses into silicon, the minority carrier lifetime decreases. Therefore, if an EL image is observed by diffusing specific metal impurities locally in the surface of the silicon substrate 601, an image in which only the individual identification information portion 604 of the cell becomes darker than the surroundings can be obtained.

  At this time, since the minority carrier lifetime of the cell individual identification information unit 604 is decreased, the characteristics of the solar battery cell may be decreased. However, the cell individual identification information unit 604 has a minimum necessary size. In this case, the cell characteristics do not deteriorate due to this. Specifically, the size of the individual identification information portion 604 of the cell on the substrate surface of the silicon substrate 601 is preferably 2 to 20 mm. If the size is less than 2 mm, pattern recognition by the EL method may be difficult, and if it exceeds 20 mm, the cell characteristics may be deteriorated due to the influence of the minority carrier lifetime reduction by the individual identification information unit 604 of the cell.

  In addition, it is preferable that the cell individual identification information portion 604 is formed on the silicon substrate 601 immediately below the electrode in order to suppress deterioration of cell characteristics, and it is particularly preferable that the cell individual identification information portion 604 is formed below the wide bus bar electrode. is there.

  In addition, it is preferable that the cell individual identification information portion 604 has a regular, substantially geometric shape such as a circle or rectangle on the substrate surface of the silicon substrate 601 for pattern recognition by the EL method.

As described above, the cell individual identification information portion 604 is observed as a point-shaped dark portion arranged in a predetermined pattern in the whole cell that shines brightly by the EL method. Can be used for displaying information related to the solar cell itself. In particular, in the case of mass production of solar cells, if the relationship between the presence / absence of the individual identification information portion 604 (dark portion) of a cell at a predetermined position on the silicon substrate 601 and the correspondence between numbers and characters are allocated in advance, the solar cells It is possible to display information as individual identification. For example, the arrangement pattern of the cell individual identification information part 604 may be changed for each hour, day, lot, etc. of solar cell production, and the maximum number of cell individual identification information parts 604 (dark parts) is 40. It is enough. That is, it is preferable that the number of the individual identification information parts 604 of a cell is 1-40.
Note that the cell individual identification information portion 604 is not normally visible to the naked eye, and thus does not impair the aesthetic appearance of the solar battery cell.

  The example of the manufacturing method of the photovoltaic cell of this invention is demonstrated based on FIG. Here, a case where a single crystal silicon substrate is used as an example of the manufacturing method will be described, but the same effect can be obtained by using not only single crystal silicon but also a polycrystalline silicon substrate as the silicon substrate. Moreover, this invention is not restricted to the photovoltaic cell produced with the following method.

(Preparation of substrate (FIG. 7A))
Slicing damage on the surface of an as-cut single crystal {100} p-type silicon substrate 601 having a specific resistance of 0.1 to 5 Ω · cm by doping high purity silicon with a group III element such as boron or gallium has a concentration of 5 to 60 Etching is performed using a high-concentration alkali such as sodium hydroxide or potassium hydroxide of mass%, or a mixed acid of hydrofluoric acid and nitric acid. The single crystal silicon substrate may be produced by either the CZ method or the FZ method, but the CZ method is preferred because it can be produced at a lower cost.

  Subsequently, minute unevenness called texture is formed on the substrate surface. Texture is an effective way to reduce solar cell reflectivity. The texture should be immersed for about 10 to 30 minutes in an alkali solution (concentration: 1 to 10% by mass, temperature: 60 to 100 ° C.) such as heated sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, sodium hydrogen carbonate, etc. Easy to make. In many cases, a predetermined amount of 2-propanol is dissolved in the solution to promote the reaction.

  After texture formation, washing is performed in an acidic aqueous solution of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or the like, or a mixture thereof. From an economic and efficient standpoint, washing in hydrochloric acid is preferred. In order to improve the cleanliness, 0.5 to 5 mass% hydrogen peroxide solution may be mixed in the hydrochloric acid solution and heated to 60 to 90 ° C. for washing.

  Next, in order to embody the configuration of the present invention, a metal impurity 602 is applied as a contamination source to the back surface (the surface opposite to the pn junction formation surface) of the silicon substrate 601 at a stage before the heat treatment described later.

  For the application of the metal impurity 602 to the substrate surface of the silicon substrate 601, a method of attaching the metal impurity 602 by bringing a metal member made of the specific metal impurity into contact with a predetermined position on the silicon substrate surface is simple and preferable. . For example, when the jig (printing machine) shown in FIG. 8 is used, the metal impurity 602 is applied by bringing the tip of a rod member 803 made of a specific metal impurity arranged in a predetermined pattern into contact with the silicon substrate 601. Is possible.

  The jig shown in FIG. 8 is provided with a base 801 in which openings 802 are provided in a plurality of rows and a plurality of columns at predetermined intervals (in FIG. 8, circular openings 802 are provided in 2 rows × 6 columns); And a cylindrical rod member 803 made of a specific metal impurity such as Fe inserted in the opening 802 and standing. According to this, by arranging the rod member 803 in an arbitrary opening 802, the rod member 803 can be contacted in an arbitrary pattern, and as a result, the cell's individual identification information section is arranged in an arbitrary pattern Is possible.

  Note that the base 801 has a shape corresponding to the substrate surface of the silicon substrate 601, and an opening 802 is provided at a position corresponding to a predetermined position (for example, an electrode formation position) of the silicon substrate 601 as a solar battery cell. It has been. For example, in FIG. 8, circular openings 802 are provided in 2 rows × 6 columns so as to correspond to the bus bar electrodes 101 in FIG. 1.

  Moreover, it is preferable that the front-end | tip part which contacts the board | substrate surface of the silicon substrate 601 of the rod member 803 has a geometric shape (circle in FIG. 8). This facilitates the recognition of the arrangement pattern of the individual identification information part of the formed cell.

(Formation of individual identification information portion of emitter layer and cell (FIG. 7B))
Next, an emitter layer (n ⁺ layer) 603 is formed by a vapor phase diffusion method using phosphorus oxychloride (for example, a heat treatment condition of 800 to 950 ° C. and a retention time of about 0 to 4 hours in a mixed gas atmosphere of nitrogen and oxygen). Form. In general silicon solar cells, it is necessary to form a pn junction only on the light-receiving surface, and in order to achieve this, heat treatment is performed in a state where two silicon substrates 601 are overlapped, and the pn junction is formed on the back surface. It is necessary to devise something that cannot be done. Further, the emitter layer 603 may be formed by applying a diffusing agent including a doping material such as phosphorus to only one surface of the silicon substrate 601 and performing heat treatment, without being limited to the vapor phase diffusion method.

  With this heat treatment, the emitter layer 603 is formed, and the metal impurities 602 are diffused into the silicon substrate 601 to form local cell individual identification information portions 604. By using such a method, the minority carrier lifetime can be reduced only at the contact point of the rod member 803. The individual identification information portion (metal contamination portion) 604 of the cell is recognized as a dot-like dark portion by observing by EL method after cell formation. In addition, since the minority carrier lifetime is lowered at the location of the individual identification information portion 604 of the cell, there is a concern that the cell characteristic may be lowered. However, as described above, a predetermined number of cells with a predetermined small size. When the individual identification information portion 604 is placed at a predetermined position, the cell characteristics are hardly deteriorated when the local minority carrier lifetime is reduced.

  In addition, since the diffusion process in this heat treatment process is high temperature, the silicon substrate 601 is usually transferred to a quartz boat or the like, and the rod member of the jig shown in FIG. By only providing a step of bringing 803 into contact, it is possible to apply (attach) metal impurities without extending the processing time.

(Glass layer removal, antireflection film and back electrode formation (FIG. 7C))
After the diffusion treatment, the glass formed on the surface is removed with hydrofluoric acid or the like, and an antireflection film 605 is formed on the light receiving surface side. The antireflection film 605, SiNx, SiO _2, magnesium fluoride, aluminum oxide, titanium oxide, tantalum oxide, zinc sulfide or the like is used, the film thickness (depending on the refractive index of the material) 50 to 150 nm approximately with sufficient A good anti-reflection effect. In the case of using a SiNx film, a film of about 100 nm is formed using a plasma CVD apparatus. As the reaction gas, monosilane (SiH ₄ ) and ammonia (NH ₃ ) are often mixed and used, but nitrogen can be used instead of NH ₃ , and the process pressure can be adjusted and the reaction gas diluted. Furthermore, when polycrystalline silicon is used for the substrate, hydrogen may be mixed into the reaction gas in order to promote the bulk passivation effect of the substrate.

In order to obtain high photoelectric conversion efficiency, it is effective to perform thin thermal oxidation before the CVD process. By processing the silicon substrate 601 in an oxygen atmosphere at 800 to 1,000 ° C. for a holding time of about 0 to 60 minutes, a SiO ₂ film of several to several tens of nm is formed. Since the thermal oxidation process is also performed at a high temperature, the silicon substrate 601 is usually transferred to a quartz boat or the like. Therefore, instead of forming the cell individual identification information portion 604 in the emitter layer 603 formation process described above, a rod is attached to the substrate surface of the silicon substrate 601 using, for example, a jig shown in FIG. The minority carrier lifetime can be reduced only at the contact point by bringing the tip of the member 803 into contact to attach the metal impurity 602 and performing thermal oxidation treatment. Also in this case, it is possible to recognize a dark portion of a predetermined arrangement pattern by observing by EL method after cell formation.

  Next, Al is formed as a back electrode 606 on almost the entire back surface of the silicon substrate 601. For the formation of the Al film, a PVD method such as a vapor deposition method or a sputtering method, or a screen printing method in which a paste obtained by mixing Al powder with an organic binder is printed using a screen plate is used. A film thickness of 1 to 10 μm is sufficient.

Next, a current-collecting bus bar electrode (not shown) is formed on the same surface of the silicon substrate 601. Silver (Ag), copper (Cu), platinum (Pt), and gold (Au) can be used as the material for the current collecting electrode, and these solid solutions may be used. Since it is necessary to keep the resistance small, Ag or Cu or a solid solution thereof is preferable. Similarly to the above, it can be formed by any of PVD methods such as vapor deposition and sputtering, and screen printing methods in which a paste obtained by mixing each metal powder with an organic binder is printed using a screen plate.
By performing heat treatment at a temperature of 500 to 900 ° C. for 5 to 30 minutes after film formation, the electrical contact property (contact resistance) between the Al electrode and the substrate is improved.

(Light-receiving surface electrode formation (FIG. 7D))
The light receiving surface electrode 607 is also formed by any one of a vapor deposition method, a sputtering method, and a screen printing method. In the case of the screen printing method, an Ag paste in which Ag powder and glass frit are mixed with an organic binder is screen-printed, and then the Ag powder is passed through the SiNx film by heat treatment (fire-through). Conduct.

  As described above, according to the method for manufacturing a solar cell of the present invention, the metal impurity 602 is locally applied to a predetermined portion of the silicon substrate 601 immediately before the heat treatment step, and the heat treatment is performed. However, it becomes possible to form the cell individual identification information portion 604 that can be observed as a pattern in which dark portions are arranged in a predetermined pattern by the EL method.

  From the viewpoint of reducing the number of steps, the back electrode 606 formation and the light receiving surface electrode 607 can be performed at once, and the order of formation such as forming the light receiving surface electrode 607 first can be changed.

  In the above example, the metal impurity application process may be performed immediately before the heat treatment process for forming the emitter layer 603 or before any process immediately before the thermal oxidation process. Alternatively, it may be performed immediately before the process of heating another silicon substrate 601 such as before the CVD process.

Further, in the above presents a configuration example was formed of Al on the entire back surface of the silicon substrate 601 as a back electrode 606, but protects the non-electrode portion and the back electrode 606 and the comb-shaped with SiNx film or SiO ₂ film The present invention is also applicable to the double-sided light receiving solar cell. According to the present invention, a double-sided light-receiving solar cell that does not impair the beauty can be supplied.

  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.

  In order to confirm the effectiveness of the present invention, the solar cell of the present invention (Example 1) shown in FIG. 6 and the solar cell of the normal configuration shown in FIG. 3 (Comparative Example 1) were prepared and compared. .

[Example 1]
After removing the damaged layer with a hot concentrated potassium hydroxide aqueous solution on six boron-doped {100} p-type as-cut silicon substrates having a thickness of 200 μm and a specific resistance of 1 Ω · cm, Dipping and texture formation were followed by washing in a hydrochloric acid / hydrogen peroxide mixed solution.
Next, the tip of the rod member 803 is brought into contact with the back surface of the silicon substrate using a jig in which a rod member 803 made of Fe (circular tip diameter 5 mm) shown in FIG. Reprinted with the back surfaces overlapped.
Next, the silicon substrate was heat-treated at 870 ° C. in a phosphorus oxychloride atmosphere to form an emitter layer (n ⁺ layer). The sheet resistance was about 36Ω. After the thermal diffusion treatment, the glass on the silicon substrate was removed with hydrofluoric acid, washed and dried.
After the above processing, a SiNx film was formed to a thickness of about 95 nm as a light-receiving surface antireflection film on a silicon substrate using a plasma CVD apparatus.
Next, Al paste was printed on almost the entire back surface of the silicon substrate by a screen printing method and dried on a hot plate at 200 ° C.
Subsequently, a back surface Ag electrode and a light receiving surface Ag electrode were sequentially formed by a screen printing method and dried. Thereafter, heat treatment was performed in an air atmosphere heated to 850 ° C. in a belt furnace to improve electrical contact between the silicon substrate and the electrode.

[Comparative Example 1]
In Example 1, after forming and cleaning the texture on the silicon substrate, metal impurities are not applied, and the back surface of the silicon substrate is transferred as it is to form an emitter layer. Otherwise, the same conditions as in Example 1 A solar battery cell was produced.

  The solar cell produced as described above could not be confirmed with the naked eye in appearance. However, as a result of observing light emission when a current of 6 amperes flows in the forward direction by the EL method, in Example 1, it corresponds to all the places to which the metal impurity (Fe) was added before the thermal diffusion treatment of the emitter layer. And a dark spot was confirmed. On the other hand, in Comparative Example 1, no dark spot was confirmed by the EL method.

Next, the electric characteristics at the time of irradiating pseudo solar light with a cell of 25 ° C., 100 mW / cm ² , and a spectrum AM of 1.5 global were measured. Table 1 shows the result (average value of 6 sheets).
In Example 1, although contaminants (specific metal impurities) were intentionally attached and diffused, since the individual identification information part (metal contamination part) of the formed cell was small, there was a decrease in solar cell characteristics. It was equivalent to Comparative Example 1.

101 Light-receiving-surface busbar electrode 102, 301, 501, 607 Light-receiving-surface electrode (finger electrode)
103, 203, 304, 403, 504, 601 Silicon substrate 201, 401 Back side bus bar electrode 202, 305, 606 Back side electrode 302, 502, 605 Antireflection film (passivation film)
303, 503, 603 Diffusion layer (emitter layer)
402, 506 Back finger electrode 505 Passivation film 602 Metal impurity (contamination source)
604 Cell individual identification information section (metal contamination location)
801 Base 802 Opening 803 Rod member

Claims (10)

A silicon substrate having a pn junction on one surface, a solar cell comprising an electrode comprising a bus bar electrode front and back surfaces are formed on each of the silicon substrate, and the pn junction formation surface of the silicon substrate A solar cell having a surface layer directly below the bus bar electrode on the opposite surface and a portion where a specific metal impurity is locally diffused as an individual identification information portion of a cell observed as a dark portion by an electric field excitation light emission (EL) method . The solar cell according to claim 1, wherein the metal impurity is Fe.   The number of the individual identification information part of the said cell is 1-40, The photovoltaic cell of Claim 1 or 2 characterized by the above-mentioned.   The solar cell according to any one of claims 1 to 3, wherein a size of the individual identification information portion of the cell on the surface of the silicon substrate is 2 to 20 mm. The solar cell according to any one of claims 1 to 4 , wherein the arrangement pattern of the individual identification information part of the cell indicates individual identification information of the solar cell. A silicon substrate having a pn junction on one surface, a method of manufacturing a solar cell comprising an electrode comprising a front and back surface bus bar electrodes formed on each of the silicon substrate, a specific metal impurities of the silicon substrate Thermal diffusion treatment is performed in a state of being attached to a position directly below the bus bar electrode on a surface opposite to the surface forming the pn junction, and the metal impurities are diffused locally on the surface of the surface of the silicon substrate. A method for manufacturing a solar cell, comprising forming an individual identification information portion of a cell observed as a dark portion by an electric field excitation light emission (EL) method on a silicon substrate surface. The method for manufacturing a solar battery cell according to claim 6 , wherein the metal impurity is Fe. The solar cell manufacturing method according to claim 6 or 7 , wherein the metal impurity is attached to the silicon substrate surface by bringing a member made of the metal impurity into contact with a predetermined position on the silicon substrate surface. Method. 9. The heat diffusion treatment according to claim 6 , wherein the thermal diffusion treatment is performed in combination with a heat treatment for forming a diffusion layer to be the pn junction or a thermal oxidation treatment before the formation of the antireflection film. Manufacturing method of solar cell. The method of manufacturing a solar battery cell according to any one of claims 6 to 9, wherein the thermal diffusion treatment is performed at 1,000 ° C or lower.