JP2015026665A - Reverse surface electrode type solar battery, solar battery module using reverse surface electrode type solar battery, and method of manufacturing reverse surface electrode type solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reverse surface electrode type solar battery having a mark for directivity confirmation which gives no mechanical damage to a substrate, and a method of manufacturing a reverse surface electrode type solar battery in which the mark can be formed without increasing the number of processes.SOLUTION: A reverse surface electrode type solar battery 1 has, on one surface of a semiconductor substrate of a first conductivity type, a first conductivity type impurity diffusion layer, a second conductivity type impurity diffusion layer, and a first electrode connected to the first conductivity type impurity diffusion layer and a second electrode connected to the second conductivity type impurity diffusion layer, and in one or more end regions of the semiconductor substrate, the first conductivity type impurity diffusion layer and the second conductivity type impurity diffusion layer are different in shape from other end regions.

Description

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

  In recent years, a solar cell that directly converts solar energy into electric energy has been rapidly expected as a next-generation energy source particularly from the viewpoint of global environmental problems. There are various types of solar cells, such as those using compound semiconductors or organic materials, but the mainstream is currently using silicon crystals.

  Currently, the most manufactured and sold solar cells have a structure in which electrodes are formed on a light receiving surface that is a surface on which sunlight is incident and a back surface that is the opposite side of the light receiving surface. However, in the solar cell having this structure, since there is reflection and absorption of light at the electrode on the light receiving surface, the incident sunlight is reduced by the area of the formed electrode. For this reason, a back electrode type solar cell in which an electrode is formed only on the back surface has been developed.

  FIG. 12 is a diagram schematically showing the structure of a conventional back electrode type solar cell 201 described in Patent Document 1. As shown in FIG. 12A is a plan view of the back surface of the solar cell 201, and FIG. 12B is a cross-sectional view taken along a line II in FIG. 12A.

  As shown in FIG. 12, the solar cell 201 includes a solar cell substrate 210. The solar cell substrate 210 includes a semiconductor substrate 215 and an n-type amorphous semiconductor layer 214n and a p-type amorphous semiconductor layer 214p that are respectively disposed in predetermined regions of the back surface 215a of the semiconductor substrate 215. The semiconductor substrate 215 has a back surface 215a and a light receiving surface 215b.

  The n-type amorphous semiconductor layer 214n and the p-type amorphous semiconductor layer 214p are formed in predetermined regions on the back surface 215a of the semiconductor substrate 215, respectively. Each of the n-type amorphous semiconductor layer 214n and the p-type amorphous semiconductor layer 214p is formed in a comb shape.

  A p-side electrode 217p is formed on the p-type amorphous semiconductor layer 214p. On the other hand, an n-side electrode 217n is formed on the n-type amorphous semiconductor layer 214n. Each of the p-side electrode 217p and the n-side electrode 217n has a comb-like shape. The p-side electrode 217p has a bus bar portion 217p1 and a plurality of finger electrode portions 217p2. The bus bar portion 217p1 is located at the edge portion 215A on the y1 side of the semiconductor substrate 215. Similarly, the n-side electrode 217n includes a bus bar portion 217n1 and a plurality of finger electrode portions 217n2. The bus bar portion 217n1 is located at the edge portion 215B on the y2 side of the semiconductor substrate 215.

  Thus, in the solar cell 201, the p-type region and the n-type region are formed on the back surface with high definition. For this reason, when manufacturing the solar cell 201, it is necessary to form the p-type region and the n-type region after accurately detecting the position of the semiconductor substrate 215.

  Therefore, two alignment marks 212a and 212b are provided on the edge 215B of the back surface 215a of the semiconductor substrate 215. More specifically, the alignment marks 212a and 212b are configured by recesses formed on the back surface 215a of the semiconductor substrate 215 located at a portion hidden by the bus bar portion 217n1 in the edge portion 215B. The alignment marks 212a and 212b can be formed by, for example, laser irradiation, etching, or mechanical processing. Further, the alignment marks 212a and 212b do not have to be concave portions, and for example, the alignment marks may be formed by forming another layer on the back surface of the semiconductor substrate.

  In the step of forming the n-type amorphous semiconductor layer 214n and the p-type amorphous semiconductor layer 214p, the alignment marks 212a and 212b are detected using detection means such as an imaging device, and n is determined based on the detection positions. A type amorphous semiconductor layer 214n and a p type amorphous semiconductor layer 214p are formed.

JP 2012-69881 A

  As shown in FIG. 12, the back electrode type solar cell has different structures in the vertical direction and the horizontal direction, and has directionality. Therefore, it is necessary to perform processing corresponding to this directionality in the manufacturing process of the back electrode type solar cell. For example, when a solar cell is extracted in the manufacturing process and then returned to the manufacturing process, it is necessary to put a mark for confirming the direction so that the direction can be recognized.

  Here, as described above, the alignment mark described in Patent Document 1 is detected using detection means such as an imaging device. Therefore, it may be a small mark that cannot be visually recognized. On the other hand, the directionality confirmation mark needs to be a mark having a size that can be easily seen visually compared to the alignment mark.

  However, when the mark for confirming directionality is constituted by a concave portion like the alignment mark described in Patent Document 1, mechanical damage is given to the substrate when the mark is formed. Therefore, there is a problem that the risk of cracking in the substrate increases. Furthermore, if the directionality confirmation mark is large, the damage becomes greater and the risk of cracking in the substrate further increases.

  In addition, as described above, the mark is formed by laser irradiation, etching, mechanical processing, etc., or by other layers, so a separate process for forming the mark is required, and the number of processes increases. As a result, there is a problem that productivity decreases.

  This invention is made | formed in view of said subject, and it aims at providing the back surface electrode type solar cell provided with the mark which does not give a mechanical damage to a board | substrate. Moreover, it aims at providing the manufacturing method of the back electrode type solar cell which can form a mark, without increasing the number of processes.

  In order to solve the above-described problem, according to one aspect of the present invention, a back electrode type solar cell according to the present invention includes a first conductivity type impurity diffusion layer on one surface of a first conductivity type semiconductor substrate, A first conductivity type impurity diffusion layer having a second conductivity type impurity diffusion layer, a first electrode connected to the first conductivity type impurity diffusion layer, and a second electrode connected to the second conductivity type impurity diffusion layer; In addition, the second conductivity type impurity diffusion layer has a shape different from that of the other end regions in one or more end regions of the semiconductor substrate.

  According to another aspect of the present invention, the first conductivity type impurity diffusion layer and the second conductivity type impurity diffusion layer are alternately formed in contact with each other. The above end regions may be wider than other end regions.

  According to another aspect of the present invention, the second conductivity type impurity diffusion layer may be shorter in one or more end regions of the semiconductor substrate than the other end regions.

  According to another aspect of the present invention, the region having a shape different from the other end region may be a mark for confirming the directionality of the back electrode type solar cell.

  According to another aspect of the present invention, the solar cell module according to the present invention uses the back electrode type solar cell of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the solar cell provided with the mark which does not give a mechanical damage to a board | substrate can be obtained. Moreover, the manufacturing method of the solar cell which does not increase the number of processes when forming a mark can be obtained.

It is the figure which showed typically the cross-section of the back electrode type solar cell concerning Example 1 of this invention. 1 is a diagram schematically showing the structure of the back surface of a back electrode type solar cell according to Example 1. FIG. FIG. 3 is a diagram showing a manufacturing process of a back electrode type solar cell according to Example 1; It is the figure which showed the mark concerning Example 2. FIG. It is the figure which showed the mark concerning Example 3. FIG. It is the figure which showed the mark concerning Example 4. FIG. It is the figure which showed typically the cross-section of the back electrode type solar cell concerning Example 5. FIG. It is the figure which showed typically the structure of the back surface of the back surface electrode type solar cell concerning Example 5. FIG. It is the figure which showed the mark concerning Example 6. FIG. It is the figure which showed the mark concerning Example 7. FIG. It is the figure which showed the mark concerning Example 8. FIG. It is the figure which showed typically the structure of the conventional back electrode type solar cell.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The contents shown in the drawings and the following description are merely examples, and the scope of the present invention is not limited to those shown in the drawings and the following description. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

<Embodiment 1>
First, Embodiment 1 of the present invention will be described using Examples 1 to 4.

Example 1
FIG. 1 is a diagram schematically showing a cross-sectional structure of a back electrode type solar cell 1 according to Example 1 of the present invention. An uneven shape 3 is formed on the light receiving surface side of the n-type silicon substrate 2. This is generally called a texture structure. The unevenness of the uneven shape 3 is on the order of μm. On the light receiving surface side of the concavo-convex shape 3, a silicon nitride film 4 serving as both a light receiving surface passivation film and an antireflection film is formed.

A back surface passivation film 5 is formed on the back surface of the n-type silicon substrate 2. On the back side of the n-type silicon substrate 2, n ⁺ layers 6 and p ⁺ layers 7 are alternately formed. The n ⁺ layer 6 is also called an n-type diffusion layer, and the p ⁺ layer 7 is also called a p-type diffusion layer. A pn junction is formed between n-type silicon substrate 2 and p ⁺ layer 7 and between n ⁺ layer 6 and p ⁺ layer 7. Further, an n-type electrode 8 is formed on the n ⁺ layer 6, and a p-type electrode 9 is formed on the p ⁺ layer 7. The n-type electrode 8 and the p-type electrode 9 form an electrode having a width of 80 to 100 μm by printing and baking a silver paste by an ink jet method or a screen printing method.

FIG. 2 is a diagram schematically illustrating the structure of the back surface of the back electrode type solar cell 1 according to the first example. The n-type electrode 8, the p-type electrode 9, and the back surface passivation film 5 are removed from the back electrode type solar cell 1, and the n ⁺ layer 6 and the p ⁺ layer 7 are exposed. The n ⁺ layer 6 and the p ⁺ layer 7 are formed in contact with each other. Both the n ⁺ layer 6 and the p ⁺ layer 7 have a substantially rectangular shape, and the n ⁺ layer 6 is connected to each other at the outer peripheral edge of the back surface of the back electrode type solar cell 1. The total area of the p ⁺ layer 7 is desirably 80% or more of the total area of the back surface. This is because a higher short circuit current can be obtained when the total area of the p ⁺ layer 7 having a conductivity type different from the n type that is the conductivity type of the silicon substrate is larger than the total area of the n ⁺ layer 6. Therefore, the p ⁺ layer 7 having a larger area is wider than the n ⁺ layer 6. On the other hand, considering the margin for alignment in printing for n-type electrode 8 on the n ⁺ layer 6, the width of the n ⁺ layer 6 is desirably 200μm or more. As described above, the back electrode type solar cell 1 has the directionality because the structures of the n ⁺ layer 6 and the p ⁺ layer 7 are different between the vertical direction and the horizontal direction.

The n ⁺ layer 6 may be separated in a direction perpendicular to the length direction. At that time, a p ⁺ layer 7 may be formed between the n ⁺ layers 6. Further, when the p ⁺ layers 7 are separated in the direction perpendicular to the length direction, the n ⁺ layers 6 may be formed between the p ⁺ layers 7.

Here, the right end of the p ⁺ layer 7, other than the p ⁺ layer 7 different top shapes, n ⁺ layer 10 of the quadrangular is present in the region of the p ⁺ layer 7. In this manner, a portion where the shape of the p ⁺ layer 7 is different from the other end region in the end region where the n-type silicon substrate 2 is provided is referred to as a mark 11. Further, the square n ⁺ layer 10 itself existing in the region of the p ⁺ layer 7 can be regarded as a mark.

  FIG. 3 is a diagram illustrating manufacturing steps of the back electrode type solar cell 1 according to the first example. Hereinafter, it demonstrates in order.

  First, as shown in FIG. 3A, a texture mask 21 such as a silicon nitride film or a silicon oxide film is formed on the back surface, which is the surface opposite to the light receiving surface of the n-type silicon substrate 2, by the CVD method. Alternatively, it is formed by sputtering or the like.

  Next, as shown in FIG. 3B, a texture structure made up of the concavo-convex shape 3 is formed on the surface to be the light receiving surface of the n-type silicon substrate 2 by etching. Etching is performed, for example, with a solution in which isopropyl alcohol is added to an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide and heated to 70 ° C. or higher and 80 ° C. or lower.

Next, the next step will be described with reference to FIG. In FIG. 3C, the back side of the n-type silicon substrate 2 is on the top. As shown in FIG. 3C, after removing the texture mask 21 formed on the back surface of the n-type silicon substrate 2, a silicon oxide film, for example, is formed on the entire back surface of the n-type silicon substrate 2 as a diffusion mask 22. Form using the method. Next, an etching paste 23 containing a component for etching the diffusion mask 22 is applied to a portion where the n ⁺ layer 6 and the n ⁺ layer 10 are to be formed on the diffusion mask 22 by inkjet or screen printing. Here, the etching paste 23 includes, for example, at least one selected from the group consisting of phosphoric acid, hydrogen fluoride, ammonium fluoride, and ammonium hydrogen fluoride as an etching component, and includes water, an organic solvent, and a thickener. Use the one containing. In the etching paste 23 applied in two places in FIG. 3C, the larger right region attempts to form the n ⁺ layer 6, and the smaller left region attempts to form the n ⁺ layer 10. It is a place to do.

Next, as shown in FIG. 3D, heat treatment is performed, and the diffusion mask 22 is pattern-etched. As a result, openings are formed in the diffusion mask 22 at locations where the n ⁺ layer 6 and the n ⁺ layer 10 are to be formed. Next, phosphorus ink 24 containing phosphorus is applied by inkjet or screen printing so as to cover the opening of diffusion mask 22. The phosphorus ink 24 includes, for example, a solvent, a thickener, and a silicon oxide precursor in addition to phosphorus.

Next, as shown in FIG. 3E, heat treatment is performed, and phosphorus is diffused from the phosphor ink 24 to form the n ⁺ layer 6 and the n ⁺ layer 10. Here, as described above, when the n ⁺ layer 10 itself is regarded as the mark 11, it can be said that the mark 11 is formed in this step.

  Thereafter, the diffusion mask 22 formed on the n-type silicon substrate 2, the glass layer formed by diffusing phosphorus in the diffusion mask 22, and the phosphor ink 24 after heat treatment are removed by hydrofluoric acid treatment.

Next, as shown in FIG. 3F, thermal oxidation with oxygen or water vapor is performed to form a silicon oxide film 25. At this time, as shown in FIG. 3F, the silicon oxide film 25 on the n ⁺ layer 6 and the n ⁺ layer 10 is formed to be thicker than that on the n-type silicon substrate 2. This is because the growth rate of the silicon oxide film by thermal oxidation differs depending on the type and concentration of impurities diffused in the silicon substrate. In particular, when the n-type impurity concentration is high, the growth rate is increased. For this reason, the thickness of the silicon oxide film 25 on the n ⁺ layer 6 and the n ⁺ layer 10, which have higher n-type impurity concentration than the n-type silicon substrate 2, is thicker than that on the n-type silicon substrate 2. Here, the surface concentration of phosphorus in the n ⁺ layer 6 and the n ⁺ layer 10 before thermal oxidation is 5 × 10 ¹⁹ / cm ³ or more, and the thermal oxidation treatment temperature range is 800 by thermal oxidation with oxygen. It is 800 to 950 ° C. by thermal oxidation with steam. For example, when thermal oxidation is performed with water vapor at 900 ° C., the thickness of the silicon oxide film 25 other than on the n ⁺ layer 6 and the n ⁺ layer 10 is 70 nm to 90 nm, and the silicon oxide film 24 on the n ⁺ layer 6 The film thickness was 250 nm to 350 nm.

Next, as shown in FIG. 3G, the silicon oxide film 25 other than on the n ⁺ layer 6 and the n ⁺ layer 10 of the n-type silicon substrate 2 is removed by etching. As indicated above, the silicon oxide film 25, ^{n +} since the thickly formed on the layer 6 and on the ^{n +} layer 10, ^{n +} layer 6 and the ^{n +} layer n-type silicon substrate 2 in 10 other regions Is exposed, and the silicon oxide film 25 is etched so that a thickness that functions as a diffusion mask for forming the p ⁺ layer remains on the n ⁺ layer 6 and the n ⁺ layer 10.

Next, a diffusion mask 26 such as a silicon oxide film is formed on the light receiving surface of the n-type silicon substrate 2. Further, boron ink 27 containing boron is applied on the back surface of the n-type silicon substrate 2 by ink jet or screen printing so as to cover a portion where the p ⁺ layer 7 is to be formed. The boron ink 27 includes, for example, a solvent, a thickener, and a silicon oxide precursor in addition to boron. Thereafter, the boron ink 27 is sintered.

Next, the next step will be described with reference to FIG. In FIG. 3H, the light receiving surface side of the n-type silicon substrate 2 is on the top. On the back surface of the n-type silicon substrate 2, boron is diffused from the boron ink 27 by heat treatment to form the p ⁺ layer 7. Thereby, a pn junction is formed. The boron surface concentration of the p ⁺ layer 7 is desirably 1 × 10 ¹⁹ / cm ³ or more. This is because if the surface concentration of impurities is too low, the contact resistance with the p-type electrode 9 increases. Here, as described above, in the case where the portion where the shape of the p ⁺ layer 7 is different from the other end region in the end region of the n-type silicon substrate 2 is regarded as the mark 11, the mark 11 is formed in this step. Can be said to be.

Next, as shown in FIG. 3I, the silicon oxide film 25 formed on the n-type silicon substrate 2, the diffusion mask 26, the glass layer formed by diffusing boron in the silicon oxide film 25, and the heat-treated film The boron ink 27 is removed by hydrofluoric acid treatment. Further, thermal oxidation is performed to form a back surface passivation film 5 made of a silicon oxide film on the back surface of the n-type silicon substrate 2. At this time, similarly to the step described with reference to FIG. 3F, the back surface passivation film 5 is formed on the n ⁺ layer 6 and the n ⁺ layer 10 to be thicker than on the p ⁺ layer 7. Be filmed.

  Next, as shown in FIG. 3J, a silicon nitride film 4 serving as both a light-receiving surface passivation film and an antireflection film is formed on the light-receiving surface of the n-type silicon substrate 2 by a CVD method.

Thereafter, patterning is performed on the back surface passivation film 5 formed on the back surface of the n-type silicon substrate 2 in order to form electrodes on the n ⁺ layer 6 and the p ⁺ layer 7 formed on the back surface side of the n-type silicon substrate 2. The patterning is performed by applying an etching paste by an ink jet method or a screen printing method, and performing a heat treatment.

Next, as shown in FIG. 3 (k), a silver paste is applied to a predetermined position on the back surface of the n-type silicon substrate 2 by a screen printing method and dried. Thereafter, an n-type electrode 8 is formed on the n ⁺ layer 6 and a p-type electrode 9 is formed on the p ⁺ layer 7 by firing.

  The back electrode type solar cell 1 provided with the mark 11 can be manufactured by the above manufacturing process.

  When the mark 11 is formed as described above, since the mark 11 can be formed without mechanically damaging the back electrode type solar cell 1, it is possible to prevent the n-type silicon substrate 2 from being cracked. It has the effect.

Moreover, according to the manufacturing method of said back surface electrode type solar cell 1, since the mark 11 can be formed simultaneously with the n ⁺ layer 6 at the process demonstrated using said FIG.3 (e), a process is carried out. There is an effect that the mark 11 can be formed without increasing.

  In the manufacturing process of the back electrode type solar cell 1 according to Example 1 described above, the mark 11 can be identified as follows.

First, in the step described with reference to the FIG. 3 (c), the etching paste 23 on the portion to be formed an n ⁺ layer 10 is from being applied, to be formed an n ⁺ layer 10 locations Can be easily identified visually.

Further, in the process described with reference to FIG. 3D and the process described with reference to FIG. 3E, light is applied only to the region where the pattern-etched diffusion mask 22 is formed. Interference color is seen. Thus, a portion of or at the n ⁺ layer 10 is to be formed an n ⁺ layer 10 is formed, it is possible to easily identify visually.

Further, in the process described with reference to FIG. 3F, there is a difference in film thickness of the silicon oxide film 25 on the n-type silicon substrate 2 and on the n ⁺ layer 6 and the n ⁺ layer 10. Therefore, the interference color when light is applied is different, and the n ⁺ layer 6 and the n ⁺ layer 10 and other regions look different colors. Accordingly, the position and shape of the n ⁺ layer 10 can be easily identified visually.

Further, in the process described with reference to FIGS. 3G and 3H, only the region where the silicon oxide film 25 remains, that is, the region where the n ⁺ layer 6 and the n ⁺ layer 10 are formed. And you can see the interference color when light is applied. Accordingly, the position and shape of the n ⁺ layer 10 can be easily identified visually.

Further, in the process described with reference to FIGS. 3 (i), 3 (j) and 3 (k) above, on the p ⁺ layer 7, on the n ⁺ layer 6 and on the n ⁺ layer 10, Since there is a difference in film thickness of the back surface passivation film 5, the interference color when light is applied is different, and the n ⁺ layer 6 and the n ⁺ layer 10 and other regions look different colors. Accordingly, the position and shape of the n ⁺ layer 10 can be easily identified visually. Furthermore, the n ⁺ layer 10 can be easily identified by the film thickness difference of the back surface passivation film 5 even after manufacturing.

Thus, in various manufacturing processes of the back electrode type solar cell 1 according to the example 1, the location where the n ⁺ layer 10 is to be formed or the n ⁺ layer 10, in other words, the mark 11 can be easily identified visually. It has the effect of being able to.

  In addition, as another means for forming the direction confirmation required mark, for example, in the electrode forming process described with reference to FIG. However, the electrode forming process is the final process of manufacturing, and the mark made of silver paste cannot be used for confirming the directivity in the previous process. In contrast, the mark 11 can be identified from the process described with reference to FIG. 3C as described above, that is, from an early stage of the manufacturing process.

  Next, another means for identifying the mark 11 will be described. As a solar cell evaluation technique, there are a PL (Photoluminescence) method and an EL (Electroluminescence) method. The PL method irradiates the solar cell with light, and then emits light emitted when the electron-hole pairs generated at the pn junction recombine from the surface side of the back electrode type solar cell 1 to a CCD camera or the like. It is the method of detecting and evaluating by. The EL method is a method in which a current is passed through a pn junction of a solar cell, and the light emitted thereby is detected and evaluated from the front surface side of the back electrode type solar cell 1 with a CCD camera or the like. In either method, light is emitted from the portion where the pn junction is formed in the solar cell. Therefore, it is possible to determine a region where light is not emitted due to a pn junction defect or the like.

In the case of the back electrode type solar cell 1 according to Example 1, a pn junction is formed between the n-type silicon substrate 2 and the p ⁺ layer 7. On the other hand, since n type silicon substrate 2 and n ⁺ layer 6 and n ⁺ layer 10 are both n type, no pn junction is formed. Therefore, when the light emitted from the back electrode type solar cell 1 is observed using the PL method or the EL method, the emitted light is observed from the region where the p ⁺ layer 7 is formed, and the n ⁺ layer 6 and It is not observed from the region where the n ⁺ layer 10 is formed. Therefore, for example, as shown in FIG. 2, the position and shape of the n ⁺ layer 10 formed in the p ⁺ layer 7 can be easily detected by the PL method or the EL method. That is, the mark 11 can be easily detected by the PL method or the EL method.

  Further, since the PL method or the EL method detects light emitted from the pn junction, the pn junction was formed not only after the production of the back electrode solar cell 1 but also during the production process. Later, the mark 11 can be detected.

  Next, a method for using the mark 11 will be described.

The mark 11 can be used, for example, in the following situation in the manufacturing process of the back electrode type solar cell 1. When some trouble occurs, the n-type silicon substrate 2 in the middle of the manufacturing process may be extracted and inspected, and then returned to the manufacturing process again. As described above, the back electrode type solar cell 1 has directionality because the structures of the n ⁺ layer 6 and the p ⁺ layer 7 are different in the vertical direction and the horizontal direction. For this reason, for example, if the n-type silicon substrate 2 extracted and inspected is returned to the manufacturing process in a direction different by 90 degrees, there is a problem that a manufacturing defect occurs due to an error in directionality. For this reason, in the manufacturing process of the back electrode type solar cell 1, it is necessary to perform processing in consideration of the directionality of the back surface structure of the back electrode type solar cell 1.

  On the other hand, since the back electrode type solar cell 1 according to Example 1 can visually confirm the directionality of the n-type silicon substrate 2 with the marks 11 as described above, it can be easily adjusted to the correct direction in the manufacturing process. Therefore, it is possible to prevent production defects. Thus, the mark 11 can be used as a mark for confirming the direction of processing in the manufacturing process of the back electrode type solar cell 1. Of course, you may confirm using PL method or EL method instead of visual observation.

  The mark 11 can also be used in a step of connecting a plurality of back electrode type solar cells 1 and sealing them with resin to produce a solar cell module. When connecting a plurality of back electrode type solar cells 1 by wiring, it is necessary to align the direction of each back electrode type solar cell 1. Also in this case, it is possible to easily confirm the orientation of the back electrode type solar cell 1 by visually identifying the mark 11 by the PL method or the EL method.

  Further, the mark 11 is formed on the back surface of the back electrode type solar cell 1. As described above, the mark 11 can be detected from the front surface side of the back electrode type solar cell 1 according to the PL method or the EL method. It is. For example, in a solar cell module manufactured by connecting a plurality of back electrode type solar cells 1 and sealing them with resin, usually only the surface of the back electrode type solar cell 1 can be confirmed. However, even in such a case, the mark 11 can be detected by the PL method or the EL method. As a result, for example, it is used in the following situation. After a solar cell module is manufactured using a plurality of back electrode type solar cells 1 and actually used, a problem of back electrode type solar cell 1 may become apparent. In such a case, the state of the malfunction of the back electrode type solar cell 1, for example, the presence or absence of cracking is inspected by the PL method or the EL method. At this time, by acquiring the position of the mark 11 together, analysis of the back electrode type solar cell 1 used in the solar cell module is associated with the direction of processing in each manufacturing process and the occurrence position of the defect. Can do. More specifically, for example, in a certain process, it is possible to analyze the relationship between the position where the jig for adjusting the position of the back electrode solar cell 1 contacts the back electrode solar cell 1 and the position where the defect occurs. It is.

In FIG. 2, the mark 11 is formed in the upper right portion of the back surface of the n-type silicon substrate 2, but may be formed in other portions. Further, although only one mark 11 is formed, a plurality of marks 11 may be formed. Further, the n ⁺ layer 10 forming the mark 11 has a quadrangular shape, but other shapes such as a triangular shape and a circular shape may be used. Further, the n ⁺ layer 10 forming the mark 11 may have a cross shape or an L shape.

  Next, other examples of marks will be described.

(Example 2)
FIG. 4 is a diagram illustrating marks according to the second embodiment. The second embodiment is a modification of the first embodiment. In FIG. 4, the two p ⁺ layers 7 at the right end are shorter than the other p ⁺ layers 7 and the upper n ⁺ layer 6 is wide. That is, there is a portion where the shape of the p ⁺ layer 7 is different from the other end regions in the end region of the n-type silicon substrate 2. This portion can be used as the mark 11a. Further, a portion where the n ⁺ layer 6 is greatly expanded can be regarded as the mark 11a. That is, the mark 11 a can be regarded as being formed by the n ⁺ layer 6.

FIG. 4 shows the case where the length of the two p ⁺ layers 7 at the right end is short, but the length of one p ⁺ layer 7 is short, or the length of three or more p ⁺ layers 7 is long. Similarly, when the length is short, it can be used as a mark.

Example 3
FIG. 5 is a diagram illustrating marks according to the third embodiment. The third embodiment is another modification of the first embodiment. In the upper right part of the back surface of the back electrode type solar cell 1 shown in FIG. 5, a part of the p ⁺ layer 7 is divided by the dividing region 12 b made of the n ⁺ layer 6, thereby forming a square p ⁺ layer 7 b. ing. That is, there is a portion where the shape of the p ⁺ layer 7 is different from the other end regions in the end region of the n-type silicon substrate 2. This portion can be used as the mark 11b. Further, the divided region 12b itself composed of the n ⁺ layer 6 can be regarded as a mark.

Further, in the lower right portion of the back surface of the back electrode type solar cell 1 shown in FIG. 5, a part of the p ⁺ layer 7 is divided by the divided region 12c made of the n ⁺ layer 6 to form a triangular p ⁺ layer 7c. Is formed. That is, there is a portion where the shape of the p ⁺ layer 7 is different from the other end regions in the end region of the n-type silicon substrate 2. This portion can be used as the mark 11c. Further, the divided region 12c itself made of the n ⁺ layer 6 can be regarded as a mark.

Note that, as described above, since the EL method causes light to flow through the pn junction of the solar cell to emit light, the p ⁺ layer 7b and the p ⁺ layer 7c emit light when the electrodes are connected and current flows. . On the other hand, in the case of the PL method, light is emitted even if electrodes are not connected to the p ⁺ layer 7b and the p ⁺ layer 7c.

Further, the p ⁺ layer 7b and the p ⁺ layer 7c in the mark 11b and the mark 11c have a quadrangular shape and a triangular shape, but may have other shapes.

  Moreover, in FIG. 5, although the mark 11b and the mark 11c are formed in the upper right part and lower right part of the back surface of the back electrode type solar cell 1, respectively, it can be used as a mark even if only one of them. .

Example 4
FIG. 6 is a diagram illustrating marks according to the fourth embodiment. The fourth embodiment is a further modification of the first embodiment. In the upper right part of the back surface of the back electrode type solar cell 1 shown in FIG. 6, a quadrangular protruding portion 13 d protrudes from the p ⁺ layer 7. That is, there is a portion where the shape of the p ⁺ layer 7 is different from the other end regions in the end region of the n-type silicon substrate 2. This portion can be used as the mark 11d.

Further, in the lower right portion of the back surface of the back electrode type solar cell 1 shown in FIG. 6, a triangular protrusion 13 e protrudes from the p ⁺ layer 7. That is, there is a portion where the shape of the p ⁺ layer 7 is different from the other end regions in the end region of the n-type silicon substrate 2. This portion can be used as the mark 11e.

Note that the mark 11d and the mark 11e can be regarded as forming a mark when a part of the n ⁺ layer 6 lacks a quadrangular shape or a triangular shape. That is, the mark can be regarded as being formed by the n ⁺ layer 6.

  In FIG. 6, the mark 11 d and the mark 11 e are respectively formed on the upper right part and the lower right part of the back surface of the back electrode type solar cell 1, but even one of them can be used as a mark. .

The various forms of marks formed on the back surface of the back electrode type solar cell 1 according to Embodiment 1 have been described above with reference to FIGS. 2, 4, 5, and 6. Each of these marks uses a portion where the shape of the p ⁺ layer 7 is different from the other end region in the end region of the n-type silicon substrate 2 as a mark. As described above, such a mark is easy to visually check in the manufacturing process of the back electrode type solar cell 1 according to the present embodiment due to the difference in film thickness of the silicon oxide film 25 formed by thermal oxidation and the presence or absence of the film. Can be identified. Further, such a mark can be easily identified visually by the film thickness difference of the back surface passivation film 5 formed by thermal oxidation. Further, as described above, such a mark can be identified by the PL method or the EL method even after the pn junction is formed on the back electrode type solar cell 1 according to the present embodiment. That is, the back electrode solar cell 1 according to the present embodiment is manufactured by forming a portion where the shape of the p ⁺ layer 7 is different from the other end region in the end region of the n-type silicon substrate 2 and using it as a mark. The mark can be easily identified both in the process and after the manufacture. Further, according to the PL method or EL method, any of these marks can be detected from the front surface side of the back electrode type solar cell 1.

In addition, since any of these marks is formed by the difference in the shape of the p ⁺ layer 7, it can be formed without causing mechanical damage to the n-type silicon substrate 2. It can prevent that a crack generate | occur | produces.

In addition, any of these marks is formed at the same time when the n ⁺ layer 6 and the n ⁺ layer 10 are formed in the process described with reference to FIG. 3 (e), or FIG. In the process described above, since the p ⁺ layer 7 is formed at the same time, the mark can be formed without increasing the number of processes.

In the present embodiment, the case where the silicon substrate is n-type has been described. However, a p-type silicon substrate can also be used. In this way, when the silicon substrate is p-type, an EL method or a PL method is used by forming a portion where the shape of the n ⁺ layer is different from the other end regions in the end region of the p-type silicon substrate. Can be identified.

  Further, the back electrode type solar cell 1 of the present embodiment can be manufactured by various manufacturing methods in addition to the manufacturing method disclosed above. In these manufacturing methods, it is possible to identify marks using the difference in thickness of silicon oxide films formed by thermal oxidation as in this embodiment.

<Embodiment 2>
Next, Embodiment 2 of the present invention will be described using Examples 5 and 6.

(Example 5)
The back electrode type solar cell 101 according to Example 5 of the present invention has a structure different from that of the back electrode type solar cell 1 according to Example 1 described above. Details will be described below.

  FIG. 7 is a view schematically showing a cross-sectional structure of a back electrode type solar cell 101 according to Example 5 of the present invention. An uneven shape 103 is formed on the light receiving surface side of the n-type silicon substrate 102. On the light receiving surface side of the concavo-convex shape 103, a silicon nitride film 104 serving as a light receiving surface passivation film and an antireflection film is formed.

A back surface passivation film 105 is formed on the back surface of the n-type silicon substrate 102. On the back surface side of the n-type silicon substrate 102, n ⁺ layers 106 and p ⁺ layers 107 are alternately formed. The n ⁺ layer 106 is also called an n-type diffusion layer, and the p ⁺ layer 107 is also called a p-type diffusion layer. A pn junction is formed between the n-type silicon substrate 102 and the p ⁺ layer 107. Further, an n-type electrode 108 is formed on the n ⁺ layer 106, and a p-type electrode 109 is formed on the p ⁺ layer 107.

FIG. 8 is a diagram schematically illustrating the structure of the back surface of the back electrode type solar cell 101 according to the fifth example. The n-type electrode 108, the p-type electrode 109, and the back surface passivation film 105 are removed from the back electrode type solar cell 101, and the n type silicon substrate 102, the n ⁺ layer 106, and the p ⁺ layer 107 are exposed. ing. The n ⁺ layers 106 and the p ⁺ layers 107 are formed alternately apart. Both the n ⁺ layer 106 and the p ⁺ layer 107 have a substantially rectangular shape. Between the n ⁺ layer 106 and the p ⁺ layer 107, the silicon substrate 102 is exposed.

Here, in the back electrode type solar cell 1 according to Example 1, the n ⁺ layer 6 and the p ⁺ layer 7 were alternately formed, but in the back electrode type solar cell 101 according to Example 5, , N ⁺ layers 106 and p ⁺ layers 107 are alternately formed.

Note that the n ⁺ layers 106 may be separated in a direction perpendicular to the length direction. At that time, the silicon substrate 102 may be exposed between the n ⁺ layers 106. Similarly, the p ⁺ layer 107 may be separated in a direction perpendicular to the length direction. At that time, the silicon substrate 102 may be exposed between the p ⁺ layers 107.

Here, the p ⁺ layer 107 at the right end is different from the other p ⁺ layers 107 in the upper shape, and the n-type silicon substrate is exposed in a square shape in the region of the p ⁺ layer 107. Part 114 is present. In this manner, a portion where the shape of the p ⁺ layer 107 is different from the other end regions in the end region of the n-type silicon substrate 102 is a mark 111. Further, the n-type silicon substrate exposed portion 114 itself can be regarded as a mark.

In FIG. 8, the p ⁺ layer 107 at the right end is shorter than the other p ⁺ layers 107, and the portion where the lower silicon substrate 102 is exposed is wide. That is, there is a portion where the shape of the p ⁺ layer 107 is different from the other end regions in the end region of the n-type silicon substrate 102. This portion can be used as the mark 111a.

As described above, since the mark 111 and the mark 111a are marks having different shapes in the p ⁺ layer 107, these marks are formed simultaneously with the formation of the p ⁺ layer 107.

In the case of the back electrode type solar cell 101 according to Example 5, a pn junction is formed between the n-type silicon substrate 102 and the p ⁺ layer 107. On the other hand, no pn junction is formed in the n-type silicon substrate exposed portion 114. For this reason, when the light emitted from the back electrode type solar cell 101 is observed using the PL method or the EL method, the emitted light is observed from the region where the p ⁺ layer 107 is formed and is exposed to the n-type silicon substrate. It is not observed from the part 114. Therefore, the mark 111 can be easily detected using the above-described PL method or EL method. The same applies to the mark 111a.

  In addition to the marks in the first embodiment, these marks are not only after the back electrode solar cell 101 is manufactured, but also after the pn junction is formed even during the manufacturing process. And EL method. Further, according to the PL method or the EL method, these marks can be detected from the front surface side of the back electrode type solar cell 101 as in the case of the marks in the first embodiment.

  In FIG. 8, the mark 111 is formed in the upper right portion of the back surface of the n-type silicon substrate 102, but may be formed in other portions. Further, although only one mark 111 is formed, a plurality of marks 111 may be formed. The same applies to the mark 111a.

Further, in the upper right portion of the back surface of the n-type silicon substrate 102 shown in FIG. 8, the portion where the silicon substrate 102 is exposed in the region of the p ⁺ layer 107 has a quadrangular shape. The shape may be a shape of a mold or an L shape.

  In FIG. 8, the mark 111 and the mark 111a are respectively formed on the upper right part and the lower right part of the back surface of the back electrode type solar cell 101. However, only one of them can be used as a mark. .

(Example 6)
FIG. 9 is a diagram illustrating marks according to the sixth embodiment. The sixth embodiment is a modification of the fifth embodiment. In the upper right part of the back surface of the back electrode type solar cell 101 shown in FIG. 9, a part of the p ⁺ layer 107 is divided by the dividing region 112 to expose the silicon substrate 102, and the rectangular p ⁺ layer 107 b is formed. Is formed. That is, there is a portion where the shape of the p ⁺ layer 107 is different from the other end regions in the end region of the n-type silicon substrate 102. This portion can be used as the mark 111b. Further, the divided region 112 itself can be regarded as a mark.

Further, in the lower right portion of the back surface of the back electrode type solar cell 101 shown in FIG. 9, a quadrangular protruding portion 113 protrudes from the p ⁺ layer 107. That is, there is a portion where the shape of the p ⁺ layer 107 is different from the other end regions in the end region of the n-type silicon substrate 102. This portion can be used as the mark 111d.

As described above, since the mark 111b and the mark 111c are portions having different shapes in the p ⁺ layer 107, these marks are formed at the same time when the p ⁺ layer 107 is formed.

The mark 111b and the mark 111c are not only after the back electrode solar cell 101 is manufactured, but also after the pn junction is formed even during the manufacturing process, as in the case of Example 5 above. It can be easily detected using the EL method or EL method. Note that, as described above, the EL method emits light by causing a current to flow through the pn junction of the solar cell. Therefore, the p ⁺ layer 107b emits light when an electrode is connected and a current flows. On the other hand, in the case of the PL method, light is emitted even when no electrode is connected to the p ⁺ layer 107b.

Further, the p ⁺ layer 7b in the mark 111b has a quadrangular shape, but may have other shapes.

  In FIG. 9, the marks 111 b and 111 c are formed on the upper right portion and the lower right portion of the back surface of the back electrode type solar cell 101, respectively, but only one of them can be used as a mark. .

(Example 7)
FIG. 10 is a diagram illustrating marks according to the seventh embodiment. The seventh embodiment is another modification of the fifth embodiment. Compared with Example 5 shown in FIG. 8, the positions of the n ⁺ layer 106 and the p ⁺ layer 107 are reversed. The right end of the ^{n +} layer 106 has different upper shapes and other ^{n +} layer 106, ^{n +} n-type silicon substrate exposed portion 114d of n-type silicon substrate in a square shape is exposed in the region of the layer 106 is there. In this manner, a portion where the shape of the n ⁺ layer 106 is different from the other end regions in the end region of the n-type silicon substrate 102 is a mark 111d. Further, the n-type silicon substrate exposed portion 114d itself can be regarded as a mark.

In FIG. 10, the n ⁺ layer 106 at the right end is shorter than the other n ⁺ layers 106, and the portion where the lower silicon substrate 102 is exposed is wide. That is, there is a portion where the shape of the n ⁺ layer 106 is different from the other end regions in the end region of the n-type silicon substrate 102. This portion can be used as the mark 111e.

As described above, since the mark 111d and the mark 111e are portions having different shapes in the n ⁺ layer 106, these marks are formed at the same time when the n ⁺ layer 106 is formed.

In the case of the back electrode type solar cell 101 according to Example 7 shown in FIG. 10, when the back surface passivation film 105 is formed of an oxide film by thermal oxidation, the back surface passivation film 105 is the same as in the first embodiment. Is formed thicker on the n ⁺ layer 106 than on the n-type silicon substrate 102. Due to the difference in film thickness, the interference color when light is applied is different, and the n ⁺ layer 106 and other regions appear to be different colors. Therefore, the positions and shapes of the marks 111d and 111e can be easily identified visually. Furthermore, in the manufacturing process of the back electrode type solar cell 101, when there is a step of using a silicon oxide film by thermal oxidation as a mask, it is easy to visually check due to the difference in film thickness of the silicon oxide film as in the first embodiment. The position and shape of the mark can be identified.

  In FIG. 10, the mark 111d is formed in the upper right portion of the back surface of the n-type silicon substrate 102, but may be formed in other portions. Further, although only one mark 111d is formed, a plurality of marks 111d may be formed. The same applies to the mark 111e.

Further, in the upper right portion of the back surface of the n-type silicon substrate 102 shown in FIG. 10, the portion where the silicon substrate 102 is exposed in the region of the n ⁺ layer 106 has a quadrangular shape, but a triangular shape, a circular shape, or a cross shape. The shape may be a shape of a mold or an L shape.

  In FIG. 10, the marks 111 d and 111 e are formed on the upper right portion and the lower right portion of the back surface of the back electrode type solar cell 101, respectively, but only one of them can be used as a mark. .

(Example 8)
FIG. 11 is a diagram illustrating marks according to the eighth embodiment. Example 8 is a combination of the marks of Example 6 and Example 7. The mark 111b and the mark 111c use a portion having a different shape in the p ⁺ layer 107 as a mark, and the mark 111d and the mark 111e use a portion having a different shape in the n ⁺ layer 106 as a mark. In this manner, marks may be formed on both the n ⁺ layer 106 and the p ⁺ layer 107.

  As described above, the mark 111b and the mark 111c can be easily detected using the PL method or the EL method. Further, as described above, the positions and shapes of the marks 111d and 111e can be easily identified visually by the film thickness difference of the back surface passivation film 105. Therefore, the mark according to the eighth embodiment can be detected by any of the above methods.

The various forms of marks formed on the back surface of the back electrode solar cell 101 according to the second embodiment have been described above with reference to FIGS. 8, 9, 10, and 11. In the marks according to Example 5, Example 6, and Example 8, a portion where the shape of the p ⁺ layer 107 is different from the other end regions in the end region of the n-type silicon substrate 102 is used as the mark. Further, in the marks according to Examples 7 and 8, a portion where the shape of the n ⁺ layer 106 is different from the other end regions in the end region of the n-type silicon substrate 102 is used as the mark. Each of these marks is the same as the mark in the first embodiment, and after manufacturing a solar cell module using a plurality of back electrode type solar cells 101, each back electrode type solar cell 101 is processed in each manufacturing process. It can be used for confirming the directionality.

In addition, since any of these marks is formed by the difference in shape of the p ⁺ layer 107 and / or the n ⁺ layer 106, it can be formed without causing mechanical damage to the n-type silicon substrate 102. It is possible to prevent the n-type silicon substrate 102 from being cracked.

In addition, since any of these marks can be formed simultaneously with the p ⁺ layer 107 and / or the n ⁺ layer 106, the mark can be formed without increasing the number of steps.

In the present embodiment, the case where the silicon substrate is n-type has been described. However, a p-type silicon substrate can also be used. In this way, when the silicon substrate is p-type, an EL method or a PL method is used by forming a portion where the shape of the n ⁺ layer is different from the other end regions in the end region of the p-type silicon substrate. Can be identified.

  The marks shown in the first and second embodiments are examples, and the position, number, shape, and the like of the marks are not limited to this. For example, the marks shown in the first and second embodiments are all formed in the end region of the silicon substrate, but may be formed inside the silicon substrate. However, it is easier to visually grasp the mark formed in the end region of the silicon substrate.

  In order to reliably determine the directionality of the n-type silicon substrate, it is preferable that the n-type silicon substrate is formed at a position, number, shape, or the like that is not rotationally symmetric at 90 degrees or 180 degrees. For example, it is preferable to form a mark at one place in the end regions near the four vertices of the n-type silicon substrate or to form marks near two vertices at both ends of a certain side.

  In the first and second embodiments, the mark is formed in the end region near the apex of the n-type silicon substrate, but may be formed in the other end region. For example, a mark may be formed near the center of a certain side of the n-type silicon substrate.

  In the first and second embodiments described above, the configuration and the like illustrated in the accompanying drawings are merely examples, and the present invention is not limited thereto, and may be changed as appropriate within the scope of the effects of the present invention. It is possible. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  The manufacturing method of the back electrode type solar cell and the back electrode type solar cell according to the present invention can be widely applied to the whole manufacturing method of the back electrode type solar cell and the back electrode type solar cell.

DESCRIPTION OF SYMBOLS 1,101 Back surface electrode type solar cell 2,102 n-type silicon substrate 3,103 uneven | corrugated shape 4,104 silicon nitride film 5,105 back surface passivation film 6,106 n ⁺ layer 7,7b, 7c, 107,107bp ⁺ layer 8, 108 n-type electrode 9, 109 p-type electrode 10, 110, 110a, 110b n ⁺ layers 11, 11a-e, 111, 111a-111e Marks 12b, 12c, 112 Dividing regions 13d, 13e, 113 Protruding portion 21 Texture mask 22 Diffusion mask 23 Etching paste 24 Phosphorous ink 25 Silicon oxide film 26 Diffusion mask 27 Boron ink 28 Silicon oxide film 29 Diffusion mask 30 Boron ink 53 Etching paste 114, 114d Exposed portion of n-type silicon substrate

Claims (5)

A first conductivity type impurity diffusion layer, a second conductivity type impurity diffusion layer, a first electrode connected to the first conductivity type impurity diffusion layer, and the second conductivity are formed on one surface of a first conductivity type semiconductor substrate. In the back electrode type solar cell having the second electrode connected to the type impurity diffusion layer,
The first conductivity type impurity diffusion layer and / or the second conductivity type impurity diffusion layer has a shape different from other end regions in one or more end regions of the semiconductor substrate. Electrode solar cell. The first conductivity type impurity diffusion layer and the second conductivity type impurity diffusion layer are formed in contact with each other alternately,
2. The back electrode type solar cell according to claim 1, wherein the first conductivity type impurity diffusion layer is wider in one or more end regions of the semiconductor substrate than in other end regions. 2. The back electrode type solar cell according to claim 1, wherein the second conductivity type impurity diffusion layer has a length shorter in one or more end regions of the semiconductor substrate than in other end regions. The back electrode solar cell according to claim 1, wherein the region having a shape different from that of the other end region is a mark for confirming the directionality of the back electrode solar cell.   A solar cell module using the back electrode type solar cell according to claim 1.