JP4144241B2 - Solar cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solar cell, and relates to, for example, a high-efficiency solar cell manufacturing technology, which is an effective technology for reducing the manufacturing cost of a polycrystalline silicon solar cell.
[0002]
[Prior art]
FIG. 7 is a schematic diagram of the front and back sides of a silicon solar cell used for conventional housing, etc. FIG. 7A is a schematic diagram of the front side of the silicon solar cell, and FIG. It is the schematic of the back surface side of a silicon solar cell. 8 is a cross-sectional view of the silicon solar cell taken along the line A1-A2 shown in FIG. 7A, and FIGS. 9 and 10 are cross-sectional structural views showing main manufacturing steps of the silicon solar cell shown in FIG.
[0003]
7 to 10, 101 is a p-type silicon substrate, 102 is a texture formed on the p-type silicon substrate 101, and 103 is an n layer formed between the p-type silicon substrate 101 and the texture 102. . 104 is an antireflection film formed on the texture 102, 110 is a sintered surface silver grid electrode formed so as to be connected to the n layer 103, and 111 is formed on the antireflection film 104. It is the paste for surface silver grid electrodes after screen printing.
[0004]
Reference numeral 112 denotes a surface silver bus electrode formed so as to be connected to the n layer 103. Reference numeral 120 denotes a sintered back aluminum electrode formed on the back surface side of the p-type silicon substrate 101, and reference numeral 121 denotes a back aluminum electrode paste after screen printing formed on the back surface of the p-type silicon substrate 101. 122 is a p + layer formed between the p-type silicon substrate 101 and the back aluminum electrode 120, 130 is a back silver bus electrode after sintering formed so as to be connected to the p + layer 122, and 140 is a front surface. Solder formed on the surface of the silver grid electrode 110.
[0005]
On the front side of the solar cell shown in FIG. 7A, an antireflection film 104 is usually provided on the p-type silicon substrate 101 in order to suppress the reflection of incident light in order to contribute as much sunlight as possible to power generation. Provided. Further, on the front side of the solar cell, a surface silver grid electrode 110 for locally collecting electricity generated in the silicon substrate 101 and a table for taking out the electricity collected by the surface silver grid electrode 110. A silver bus electrode 112 is disposed.
[0006]
Here, the front silver grid electrode 110 and the front silver bus electrode 112, which are the front electrodes of the solar cell, block sunlight incident on the front side of the solar cell, and therefore are arranged as small as possible on the front side of the solar cell. This is desirable from the viewpoint of improving the power generation efficiency of the solar cell.
[0007]
Therefore, considering that a large amount of sunlight is incident on the front side of the solar cell, for example, a comb-shaped grid electrode 110 and a bus electrode 112 as shown in FIG. 7A are arranged on the surface of the solar cell. It is common. Moreover, as an electrode material of the grid electrode 110 and the bus electrode 112, for example, a case where silver is the main component is common from the viewpoint of cost and performance.
[0008]
In the back side of the solar cell shown in FIG. 7B, a back aluminum electrode 120 is provided over a wide area in order to prevent the electricity generated on the back side from being reduced by a loss due to resistance, and power is generated by the back aluminum electrode 120. In order to collect electricity, a back silver bus electrode 130 is further arranged.
[0009]
In general, the back aluminum electrode 120 often uses an aluminum material in order to improve the power generation capability by the BSF (Back Surface Field) effect. In the case where the back silver bus electrode 130 functions as an electrical lead wire for extracting electricity generated by the back aluminum electrode 120, it is common to use a copper wire with solder. Here, the back aluminum electrode 120 is used. For example, a silver electrode is used as the back bus electrode with good adhesion processability.
[0010]
In general, a low-cost solar cell uses a silicon substrate to generate sunlight with a simple pn junction, and a p-type silicon substrate 101 having a thickness of several hundred μm is made of a group V element such as phosphorus (P). By performing diffusion or the like, an n layer 103 having a thickness of about several hundred nm is formed. Here, the p-type silicon substrate 101 may be either a single crystal or a polycrystal, but in the following description, a single crystal substrate having a (100) plane orientation will be described as an example.
[0011]
In this solar cell, a p-type silicon 101 substrate surface having a specific resistance of about 0.1 to 5 Ω · cm is provided with an n layer 103 and a texture 102 having a concavo-convex structure that confines light on the substrate 101 side, and antireflection is provided on the texture 102. A membrane 104 is disposed. A back aluminum electrode 120 is disposed on the back side of the substrate 101, and a p + layer 122 is provided in anticipation of a BSF (Back Surface Field) effect so that electrons in the p + layer 122 are not annihilated by an electric field having a band structure. The electron concentration is increased.
[0012]
The back aluminum electrode 120 is also expected to have a BSR (Back Surface Reflection) effect in which long-wavelength light passing through the silicon substrate 101 is reflected and reused for power generation. However, the back aluminum electrode 120 has a tendency that the warp of the silicon substrate 101 becomes remarkable, and accordingly, the substrate 101 is cracked. For this reason, the back aluminum electrode 120 is often removed after the P + layer 22 is formed by heat treatment in consideration of cracks in the substrate 101.
[0013]
Here, the reason why the silicon substrate 101 is warped will be described. When an aluminum (Al) film for the back aluminum electrode 120 is formed on the back surface of the silicon substrate 101, an Al—Si alloying reaction occurs between Si in the silicon substrate 101 and Al in the Al film. Thereafter, re-solidification at about 777 ° C. is performed to sinter the Al film to form the back aluminum electrode 120. By this heat treatment, a difference in thermal expansion occurs between the silicon substrate 101 and the back aluminum electrode 120 having different thermal expansion coefficients, and the silicon substrate 101 warps so as to be concave on the back aluminum electrode 120 side.
[0014]
Next, a manufacturing process of the solar cell shown in FIG. 8 will be described with reference to FIGS. 9 and 10 illustrate a solar cell manufacturing process with a small number of manufacturing steps in consideration of cost reduction. Here, the front silver grid electrode 110 and the front silver bus electrode 112 are made by adhering and drying silver paste on the antireflection film 104 by a screen printing method, and the back aluminum electrode 120 and the back silver bus electrode 130 are also attached by the screen printing method. dry.
[0015]
Then, each electrode 110,112,120,130 is formed by baking the front and back electrode paste simultaneously. By this firing, the front silver electrodes 110 and 112 pass through the antireflection film 104 and remain in the n layer 103. Further, the back aluminum electrode 120 and the silicon substrate 101 are melted and re-solidified by this baking, thereby forming a p + layer 122 between the back aluminum electrode 120 and the silicon substrate 101. Below, the manufacturing method of this solar cell is demonstrated concretely.
[0016]
First, a p-type silicon substrate 101 shown in FIG. 9A is used, and a damage layer on the surface of the silicon substrate 101 generated when slicing from a cast ingot is made, for example, several to 20 wt% caustic soda or carbonated caustic soda about 10 to 20 μm thick. After removal, anisotropic etching is performed on the surface of the silicon substrate 101 with a solution obtained by adding IPA (isopropyl alcohol) to a similar alkaline low-concentration solution, and the texture 102 is formed on the surface of the silicon substrate 101 so that the silicon (111) surface appears. It is formed (FIG. 9B).
[0017]
Subsequently, the n layer 103 is uniformly formed on the entire surface of the silicon substrate 101 by performing heat treatment at a temperature of about 800 to 900 ° C./several tens of minutes in a mixed gas atmosphere of phosphorus oxychloride (POCl 3), nitrogen, and oxygen, for example. . At this time, the range of sheet resistance in the n layer 103 formed on the surface of the silicon substrate 101 is about 30 to 80Ω / □, and good electrical characteristics as a solar cell can be obtained.
[0018]
Next, in order to protect the n-layer 103 on the light-receiving surface side required as the light-receiving surface, a polymer resist paste is attached by a screen printing method and dried so as to cover the n-layer 103 on the light-receiving surface portion. At this time, a resist mask is selectively formed so as to cover the n layer 103 in the light receiving surface portion, and the n layer 103 in a portion other than the light receiving surface portion is exposed.
[0019]
Thereafter, using a resist mask that covers the n layer 103 in the light receiving surface portion, the n layer 103 formed on the surface of the silicon substrate 101 other than desired (other than the light receiving surface portion) such as the back surface of the silicon substrate 101 is, for example, 20 wt% water. After selective removal by immersion in a potassium oxide solution for several minutes, the resist used as a mask is removed with an organic solvent (FIG. 9C). As a result, the n layer 103 in the light receiving surface portion remains, and the n layer 103 other than the light receiving surface portion is removed, and the silicon substrate 101 is exposed.
[0020]
Further, an antireflection film 104 made of a silicon oxide film, a silicon nitride film, a titanium oxide film, or the like is formed with a uniform thickness on the surface of the remaining n-layer 103 of the light receiving surface (FIG. 10A). For example, when the antireflection film 104 is formed of a silicon nitride film, a silicon oxide film is formed by plasma CVD using SiH 4 gas and NH 3 gas as raw materials at 300 ° C. or higher and under reduced pressure.
[0021]
The refractive index of the antireflection film 104 made of a silicon nitride film formed here is about 2 to 2.2, and the optimum thickness of the antireflection film 104 is about 70 to 90 nm. The antireflection film 104 made of the silicon nitride film thus formed functions as an insulator. Therefore, simply forming a surface electrode on the antireflection film 104 of the insulator operates as a solar cell. I can't let you. Therefore, processes such as wiring connection as described below are performed.
[0022]
Next, silver paste for forming the front silver grid electrode 110 and the front silver bus electrode 112 is deposited on the antireflection film 104 by a screen printing method and dried. Thus, the surface silver grid electrode paste 111 and the surface silver bus electrode paste are selectively formed on the antireflection film 104. FIG. 10B shows that the surface silver grid electrode paste 111 is formed on the antireflection film 104. Note that the paste for the front silver bus electrode is not shown in FIG.
[0023]
Further, when the back aluminum electrode 120 and the back silver bus electrode 130 are formed, similarly, the aluminum paste for forming the back aluminum electrode 120 and the silver paste for forming the back silver bus electrode 130 are formed by the screen printing method. Each is attached to and dried. Thus, the back aluminum electrode forming paste 121 and the back silver bus electrode forming paste are selectively formed on the back surface of the silicon substrate 101.
[0024]
FIG. 10B shows that the back aluminum electrode paste 121 is formed on the back surface of the silicon substrate 101. Note that the back silver bus electrode paste is not shown in FIG. In screen printing, a mesh having 200 to 400 meshes is usually used. Usually, the paste thickness before drying is about 10 to several tens of μm, but this paste thickness is reduced by several percent by drying or baking.
[0025]
Finally, the front and back electrode pastes including the front silver grid electrode paste 111, the front silver bus electrode paste, the back aluminum electrode paste 121 and the back silver bus electrode paste are simultaneously measured at about 600 ° C. to 900 ° C. Bake for about a minute. By this firing, while the antireflection film 104 is melted on the front side of the silicon substrate 101 by the glass material contained in the front silver grid electrode paste 111 and the front silver bus electrode paste including the front silver bus electrode paste. Furthermore, the silver material in the silver paste comes into contact with the silicon in the n layer 103 above the silicon substrate 101 to resolidify.
[0026]
By the above baking process, the front and back electrode paste is fired to form the front silver grid electrode 110, the front silver bus electrode 112, the back aluminum electrode 120, and the back silver bus electrode 130. FIG. 10C shows that the front silver grid electrode 110 and the back aluminum electrode 120 are formed. The front silver bus electrode 112 and the back silver bus electrode 130 are shown in FIG. Not shown in C).
[0027]
Further, the above-described firing step ensures conduction between the surface silver electrode 110 and the surface silver bus electrode 112 between the surface silver electrode and the silicon n layer 103. Such a process is called a fire-through method. Also, by this baking process, the back aluminum electrode paste 121 also reacts with the silicon in the silicon substrate 101 to form the back aluminum electrode 120, and the p + layer 122 is formed between the silicon substrate 101 and the back aluminum electrode 120. Is done.
[0028]
Here, what is important in the fire-through method is that the antireflection film 104 is formed with a thickness of about several tens of nm and the n layer 103 is formed only with a thickness of about several hundred nm. During firing, the glass in the silver paste generally reacts not only with the antireflection film 104 but also with the silicon in the n layer 103, and the glass and the silver electrodes 110 and 112 are fired so as to remain in the n layer 103. The temperature and time must be controlled.
[0029]
Similarly, in the manufacturing method in which the antireflection film 104 is removed only under and near the surface silver electrodes 110 and 112 in advance, and in the manufacturing method in which the antireflection film 104 is formed later, controllability during firing is also important. is there. When the firing temperature is low or the firing time is short, the contact between the silicon in the n layer 103 and the silver electrodes 110 and 112 is insufficient, resulting in a problem that the contact resistance increases.
[0030]
On the contrary, when the firing temperature is high or the firing time is long, the glass component and the silver electrodes 110 and 112 penetrate through the n layer 103, and the electrical characteristics of the solar cell are likely to be deteriorated. In addition, if the surface silver electrodes 110 and 112 are not evenly connected to the silicon in the n layer 103, the initial electrical characteristics of the solar cell deteriorate.
[0031]
Furthermore, even if the solar cell is sealed and modularized with resin, glass or the like, moisture that has passed through the sealing resin during long-term use reaches the solar cell, and the surface silver electrodes 110 and 112 and the silicon interface are connected. In some cases, the life of the solar cell may be shortened due to deterioration due to a reaction such as oxidation.
[0032]
Therefore, as one of the countermeasures, in order to improve the moisture resistance of the silver electrodes 110 and 112, the solar cell is immersed in a lead / tin eutectic solder melting bath at about 200 to 250 ° C. As shown, the surface silver electrodes 110 and 112 are coated with solder 140. Thereby, the moisture resistance in the surface silver electrodes 110 and 112 can be improved.
[0033]
FIG. 11 is a perspective view showing the overall structure of a conventional solar cell module, and FIG. 12 is a cross-sectional view of the solar cell module taken along line B1-B2 shown in FIG. In FIGS. 11 and 12, reference numeral 151 denotes a solar cell, 152 denotes a moisture-resistant back sheet in which PVF (polyvinyl fluoride) resin or the like disposed on the back side of the solar cell 151 is often used, and 153 denotes the solar cell 151 mutually. It is a solar cell interconnection tab wiring mainly composed of copper for connection.
[0034]
Reference numeral 154 denotes a horizontal tab wiring for interconnecting the solar cells 151, 155 denotes a plus extraction electrode of the solar cell module, and 156 denotes a minus extraction electrode of the solar cell module. Reference numeral 157 denotes a reinforced cover glass disposed on the front side of the solar cell 151, and reference numeral 158 denotes a solar cell sealing material (EVA: Ethylene) disposed between the moisture-resistant back sheet 152 and the reinforced cover glass 157 so as to protect the solar cell 151. -Vinyl-Acetate).
[0035]
Since the solar cell 151 is configured with a negative electrode on the light-receiving surface side and a positive electrode on the back surface side, in FIG. 11, the upper and lower sides of the solar cells 151 adjacent in the horizontal direction are interconnected by tab wiring 153 mainly composed of copper. Do. Similarly, the solar cell arrays that are connected in the horizontal direction are also electrically connected by the horizontal tab wire 154, and finally, electricity can be extracted by the plus extraction electrode 155 and the minus extraction electrode 156.
[0036]
In addition, since the solar cell module is required to have long-term reliability, as shown in FIGS. 11 and 12, the solar cell array prevents intrusion of rain and the like while transmitting sunlight to the outermost surface, falling objects, etc. It covers so that it may cover with the reinforced cover glass 157 provided with the function which absorbs an impact.
[0037]
A back sheet 152 is provided on the back side of the solar cell array. A gap between the solar cell 151 and the reinforced cover glass 157 or the back sheet 152 is filled with a sealing material 158. The sealing material 158 is generally made of a thermosetting resin having a high light transmittance such as EVA (Ethylene-Vinyl-Acetate). The EVA agent is preferably a sheet having good workability.
[0038]
Here, the manufacturing process of this conventional solar cell module will be described. First, the interconnection tab line 153 is connected to the solar cell 151 to produce a lateral solar cell array. Next, the horizontal tab wiring 154 and the positive and negative extraction electrodes 155 and 156 are connected to the solar cell array.
[0039]
Finally, the solar cell 151 is inserted with two sheets of EVA or the like, and further inserted with a reinforced cover glass 157 and a back sheet 152 arranged above and below the solar cell 151, and heated simultaneously with defoaming. As a result, a solar cell module having no gap as shown in FIG. 12 can be obtained.
[0040]
[Problems to be solved by the invention]
In the conventional silicon solar battery as described above, the required amount is more than the degree that the deterioration of the electric characteristics of the solar battery and the peel strength (adhesion strength) of the tab wiring 153 in FIG. The above silver paste was used for the front and back electrodes. Thus, since the silver paste more than necessary was used so that each characteristic of a solar cell might not be deteriorated, there existed a problem that the manufacturing cost of a photovoltaic cell increased.
[0041]
Therefore, the present invention can reduce the amount of silver paste used for the electrode while maintaining the cell performance without deteriorating each characteristic of the cell, and can reduce the manufacturing cost of the solar cell. The purpose is to provide.
[0042]
[Means for Solving the Problems]
Polycrystalline silicon solar cell according to the present invention is for converting light energy received by photovoltaic, disposed on the light receiving surface of the p-type silicon substrate to collect photovoltaic, table silver of silver The front silver bus electrode has a diameter of 0.23 mm and a pitch of 0.25 mm, and is arranged in a staggered pattern. This has a circular empty portion that does not use silver, and in the front silver bus electrode, the ratio of the area of the empty portion to the area of the front silver bus electrode including the empty portion is 6.3%.
[0043]
In addition, it has a silver back bus electrode made of silver that is arranged on the opposite side of the light receiving surface and collects photovoltaic power, and the back silver bus electrode is a circular space that does not use silver arranged in a staggered pattern In the back silver bus electrode, the ratio of the area of the empty portion to the area of the back silver bus electrode including the empty portion is 2.5%.
[0044]
Moreover, the diameter of the circular empty part arranged in a staggered pattern is 0.23 mm, and the pitch is 0.25 mm.
[0045]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a top view showing a surface electrode arrangement of a solar cell in the first embodiment, FIG. 2 is an enlarged detailed view of a front silver bus electrode portion in the first embodiment, and FIG. 3 is a back side of the solar cell in the first embodiment. FIG. 4 is an enlarged detailed view of the back silver bus electrode portion in the first embodiment. 1-4, 10 is a front silver grid electrode, 12 is a front silver bus electrode, 30 is a back silver bus electrode. The bus electrodes 12 and 30 have a function of collecting and outputting the photovoltaic power on the light receiving surface side of the solar cell that converts received light energy into photovoltaic power.
[0046]
As shown in FIGS. 1 to 4, in the present embodiment, it is the front and back that the circular punched pattern is arranged on the bus electrodes 12 and 30 in a staggered pattern without silver on the entire surface. This is a significant difference from the conventional one in which silver electrodes are arranged on the entire surface of the electrode. In the bus electrodes 12 and 30, in the silver used for the electrodes, a circular blanking pattern is partially arranged in a staggered pattern without silver, so that there is no space in the silver instead of the entire surface. A part is formed.
[0047]
The front silver electrodes 10 and 12 and the back silver electrode 30 shown in FIGS. 1 to 4 are formed by screen printing, but the required silver paste is adjusted by adjusting the shape of the blank pattern on the bus electrodes 12 and 30. The amount can be controlled. Thereby, the usage-amount of the silver paste used for the bus electrodes 12 and 30 can be reduced.
[0048]
Hereinafter, combinations of the three types of front and back electrodes that have been actually studied will be described. In FIG. 5, Conventional Example A is a solar cell having a conventional shape for both front silver and back silver electrodes (with silver electrodes on the entire surface). In FIG. In the shape, the back silver (with silver electrodes on the entire surface) is a conventional solar cell, and in FIG. 5, the present invention C is the blank pattern shape of FIG. This is a solar cell with a blank pattern shape, and the electrical characteristics, peel strength, and cell warpage amount of each solar cell were examined.
[0049]
FIG. 6 shows the usage reduction rate of the front and back silver pastes tested this time. The calculated value of the silver area reduction rate is obtained from the total area of the pattern and the area of the blank pattern. The measured values are obtained by measuring the weight of the silver paste used on the front and back surfaces of the cell for each of the conventional pattern and the punched pattern, and the difference between them. The reliability of reducing the amount of silver paste used is higher in the actual measurement than in the calculated value. As can be seen from FIG. 6, a silver paste reduction rate substantially equal to the actual measurement value was obtained for both the front surface and the back surface.
[0050]
In FIG. 5, Voc is an open circuit voltage, which is a voltage in a state where nothing is connected between the positive electrode and the negative electrode of the solar cell. In FIG. 5, Jsc is a short-circuit current density, which is a value obtained by connecting the positive and negative electrodes of a solar cell with conductive wires in a state where sunlight is incident, and dividing the current when short-circuited by the area of the solar cell. .
[0051]
In FIG. 5, FF is a fill factor and is expressed as a ratio of the product of the maximum open circuit voltage (Voc) and short circuit current density (Jsc) that can be supplied to a certain load. In FIG. 5, Eff is the conversion efficiency, which is obtained by multiplying the open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) described above, and represents the final solar cell performance. It is.
[0052]
As described above, the conventional example A shown in FIG. 5 is a case where both the front silver and the back silver electrode are in a conventional shape, and the present invention B is a case where the front silver is a cut pattern shape and the back silver is a conventional case. C is a case where both front silver and back silver have a blank pattern shape. In each of the conventional example A and the present invention B and C, the characteristics of the open circuit voltage Voc, the short circuit current Jsc, the fill factor FF, and the conversion efficiency Eff are not greatly different, and the possibility of reducing the amount of silver paste used for the front and back electrodes can be found. I found out.
[0053]
Moreover, the peeling strength was measured about the photovoltaic cell of the front and back electrode pattern of A, B, and C3 types in the said FIG. As a result, when the amount of the back silver paste used is reduced at this rate, the peel strength is slightly reduced, but this is not a problem level when modularized. Although the amount of cell warpage was also measured at 8 points in the substrate, the amount of warpage was not deteriorated even when the amount of front and back silver paste used was reduced at this rate.
[0054]
From the above results, even if the amount of the silver paste on the front and back electrodes is reduced at the ratio tested this time, the above characteristics are not deteriorated, and the manufacturing cost of the solar battery cell can be reduced. In the above embodiment, the case where a blank pattern without silver is provided only on the front silver and the case where a blank pattern is provided on both sides of the front silver and the back silver are shown as materials of the present invention. Even when only the back silver is provided, the amount of silver paste used in the electrode can be reduced while maintaining the performance of the cell, without deteriorating each characteristic of the cell, as in the case of only the front silver. The manufacturing cost of the solar cell can be reduced.
[0055]
【The invention's effect】
According to the polycrystalline silicon solar cell according to the present invention, to collect the photovoltaic disposed on the light receiving surface side, it comprises a front silver bus electrode made of silver, front silver bus electrode diameter pitch 0.23mm is It has a circular empty portion that does not use silver that is 0.25 mm and arranged in a staggered pattern, and in the front silver bus electrode, the ratio of the area of the empty portion to the area of the front silver bus electrode including the empty portion is by was 6.3%, without deteriorating the characteristics of the cell, while maintaining the performance of the cell can be reduced the amount of the silver paste on the light-receiving surface side electrode, polycrystalline silicon solar cells Manufacturing cost can be reduced.
[0056]
In addition, a back silver bus electrode made of silver, which is arranged on the opposite side to the light receiving surface side and collects photovoltaic power, has a diameter of 0.23 mm and a pitch of 0.25 mm. It has circular empty parts that do not use silver arranged in a staggered pattern, and in the back silver bus electrode, the ratio of the area of the empty part to the area of the back silver bus electrode including the empty part was 2.5% As a result, it is possible to reduce the amount of silver paste used for the electrodes on the light-receiving surface side and the back side while maintaining the cell performance without degrading the characteristics of the cell, thereby reducing the manufacturing cost of the polycrystalline silicon solar cell. can do.
[Brief description of the drawings]
FIG. 1 is a top view showing a surface electrode arrangement of a solar cell in a first embodiment.
FIG. 2 is an enlarged detailed view of a front silver bus electrode portion of the solar cell in the first embodiment.
3 is a top view showing the back electrode arrangement of the solar cell in the first embodiment. FIG.
4 is an enlarged detailed view of a back silver bus electrode portion of the solar cell in the first embodiment. FIG.
FIG. 5 is a diagram showing electrical characteristics, peel strength, and cell warpage in a conventional example material and in the present invention material.
FIG. 6 is a diagram showing a reduction rate of silver on the front and back of a cell when a blank pattern without silver is formed on the front and back surfaces of the cell.
FIG. 7 is a schematic view of the front and back sides of a silicon solar cell used for a conventional house or the like.
8 is a cross-sectional view of the silicon solar cell taken along line A1-A2 shown in FIG.
9 is a cross-sectional structure diagram showing main manufacturing steps of the silicon solar cell shown in FIG. 8. FIG.
10 is a cross-sectional structure diagram showing main manufacturing steps of the silicon solar cell shown in FIG. 8. FIG.
FIG. 11 is a perspective view showing the entire structure of a conventional solar cell module.
12 is a cross-sectional structure view of the solar cell module taken along line B1-B2 shown in FIG.
[Explanation of symbols]
10 front silver grid electrodes, 12 front silver bus electrodes, 30 back silver bus electrodes.

Claims (2)

In a polycrystalline silicon solar cell that converts received light energy into photovoltaic power,
a front silver bus electrode made of silver, arranged on the light receiving surface side of the p-type silicon substrate and collecting photovoltaic power ;
And a back aluminum electrode which is provided opposite the light-receiving surface side in the p-type silicon substrate,
The front silver bus electrode has a circular empty portion having a diameter of 0.23 mm and a pitch of 0.25 mm and using no silver arranged in a staggered pattern,
Wherein the front silver bus electrode, a polycrystalline silicon solar cell ratio is 6.3% of the area of the free portion to an area of the front silver bus electrode including the free portion. It is arranged on the opposite side to the light receiving surface side and has a back silver bus electrode made of silver that collects photovoltaic power,
The back silver bus electrode has a circular empty portion having a diameter of 0.23 mm and a pitch of 0.25 mm and using no silver arranged in a staggered pattern,
In the above Uragin bus electrodes, the ratio of the area of said free portion to an area of said Uragin bus electrode including a free portion is 2.5%, the polycrystalline silicon solar cell according to claim 1.

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