WO2017134782A1

WO2017134782A1 - Solar cell manufacturing method, solar cell, and solar cell manufacturing apparatus

Info

Publication number: WO2017134782A1
Application number: PCT/JP2016/053271
Authority: WO
Inventors: 土井　誠
Original assignee: 三菱電機株式会社
Priority date: 2016-02-03
Filing date: 2016-02-03
Publication date: 2017-08-10
Also published as: JP6541805B2; JPWO2017134782A1

Abstract

The purpose of the present invention is to form a low-cost electrode without deteriorating the characteristics of a solar cell. The present invention is provided with: a step for forming a pn junction on a semiconductor substrate, and forming a solar cell substrate 1S; and an electrode-forming step that includes an application step for applying a paste 4P to an electrode-forming surface of the solar cell substrate 1S, said paste containing a conductive material, i.e., an electrode material, and a firing step for firing the paste 4P thus applied. The present invention is characterized in that the application step includes a step for applying the paste 4P to the electrode-forming surface using a liquid applying apparatus, while controlling the discharge amount per hour from a discharge nozzle 103 that discharges the paste 4P, said liquid applying apparatus being provided with the discharge nozzle 103.

Description

Solar cell manufacturing method, solar cell and solar cell manufacturing apparatus

The present invention relates to a method for manufacturing a solar cell, a solar cell, and a solar cell manufacturing apparatus, and more particularly to formation of an electrode for a solar cell.

”Renewable energy has been popularized by the government's energy policy. In particular, solar power generation has become explosively popular due to the purchase policy in accordance with the Feed-in Tariff (FiT), which purchases the generated power at a fixed price. Appeared a lot.

However, this purchase amount is added to the charge when the public uses commercial power, and the purchase price is reviewed every year to reduce the burden, and a fundamental review of this system will eventually come. Conceivable. Nonetheless, solar power generation is a power generation method that does not emit carbon dioxide, and the cost of power generation will continue to be reduced by technological innovation, and there is no doubt that it will become popular especially if it is a high-performance and inexpensive solar cell. .

Regarding the production of a conventional solar cell, Patent Document 1 adopts the following procedure. First, an uneven structure called a texture for changing the reflection angle of sunlight on the surface of a substrate material such as silicon and taking reflected light into the substrate is formed by a technique such as etching. Next, a pn junction is formed by a technique such as diffusion, and an antireflection film made of a high refractive index thin film such as a silicon nitride film is formed on at least one surface of the substrate material in order to reduce reflection of sunlight by the light interference effect. To do. Next, a conductive paste such as a metal paste is applied on the antireflection film so as to have a desired pattern, and the paste is heated to melt the antireflection film with the glass contained in the paste, so that electrical connection with the substrate is achieved. Firing is performed for bonding, and an electrode is formed. Further, the substrate material is immersed in an etching solution for dissolving the glass component, and the glass component contained in the electrode is dissolved to reduce the electrical resistance of the electrode.

Also, for example, Patent Document 2 and Patent Document 3 disclose similar solar cell manufacturing methods.

It is extremely difficult to reduce the cost of solar cells and solar cell modules without reducing the cost of the constituent materials of solar cells, which occupy a large percentage in price. For example, it is necessary to review everything from the substrate material such as silicon as the base material to the materials used in each process, consumables, and the like. In particular, various efforts are being made to reduce the relative prices of electrode materials that occupy a large part of the cost.

The electrode material is generally called a paste, and is mainly composed of a conductive material made of metal powder, an inorganic material that is a glass component, an organic material that is a resin component, and an organic solvent. As described above, the paste is formed into a desired electrode shape by various printing methods such as a screen printing method, and the antireflection film is melted by a glass component contained in a heating process called baking to electrically connect the substrate material and the Bonding is performed to form an electrode.

As the conductive material, silver is usually used, but it is also a noble metal, is easily influenced by the market price, and is not cheap in price. However, the performance of solar cells is largely dependent on the electrode made of silver paste, and electrodes made of other materials are not the mainstream in the world. Therefore, manufacturers that develop, manufacture, and sell this paste are competing every day to determine how efficient solar cells can be manufactured with a small amount of paste, a small amount of silver, and so on. Currently.

Usually, on the surface of a solar cell, a thin grid electrode for collecting the generated current and a thick bus electrode for inter-substrate connection are arranged so as to be perpendicular to the grid electrode. Molding techniques are the mainstream. The high performance of the paste is the molding of a thin and high grid electrode, which is different from the molding required to reduce the thickness of the bus electrode, that is, to suppress the coating amount. Techniques for molding are being studied.

However, in order to form the grid electrode and the bus electrode independently by the conventional method, it is necessary to invest in a screen printing facility for one more unit. However, as long as the electrode paste to be used is not very inexpensive, the investment cannot be recovered. As described above, the electrode paste is not so inexpensive as to be profitable as described above.

As described above, in the conventional method for forming an electrode for a solar cell, the cost of the electrode paste to be used is expensive. Even when the electrode paste suitable for each of the grid electrode and the bus electrode is adopted, the same equipment is used. It was disadvantageous in terms of profitability to manufacture each of them together. Therefore, as long as the conventional screen printing method is used, it is extremely difficult to reduce the total manufacturing cost, and the price of the solar cell cannot be reduced.

Japanese Patent No. 4486622 Japanese Patent No. 4319006 Japanese Patent No. 4481869

Even if an electrode paste suitable for each of the bus electrode and the grid electrode is adopted to reduce the manufacturing cost of the solar cell, the amount of initial investment becomes large and the recovery becomes more difficult if the same screen printing method is used. was there. In addition, if a higher performance electrode paste is used with the conventional electrode forming method, the unit cost will increase even if the total amount of paste used is reduced, resulting in a problem that the material cost of the electrode paste cannot be reduced. .

The present invention has been made in view of the above, and an object thereof is to realize low-cost electrode formation without deteriorating the characteristics of a solar cell.

In order to solve the above-described problems and achieve the object, the present invention provides a process for forming a pn junction on a semiconductor substrate to form a solar cell substrate, and a paste containing a conductive material as an electrode material. And an electrode forming step including a coating step of coating the electrode forming surface of the substrate for use and a firing step of firing the applied paste. The application step includes a step of applying the paste to the electrode formation surface while controlling the application amount with the discharge amount per time from the discharge nozzle using a liquid application apparatus having a discharge nozzle for discharging the paste. It is characterized by.

According to the present invention, it is possible to realize low-cost electrode formation without deteriorating the characteristics of the solar cell.

The figure which shows the surface which is a light-receiving surface of a solar cell provided with the electrode formed by the electrode formation method of the solar cell concerning Embodiment 1 The figure which shows the back surface on the opposite side to a light-receiving surface about the solar cell shown in FIG. III-III sectional view of FIGS. 1 and 2 IV-IV sectional view of FIGS. 1 and 2 Schematic explaining the printing machine used for the electrode forming method of Embodiment 1 Schematic cross-sectional view of the stage portion of the printing press used in the electrode forming method of the first embodiment Schematic plan view of the stage portion of the printing press used in the electrode forming method of Embodiment 1 (A) And (b) is the top view and side view which show a pressure sensor The top view which shows the example of the board | substrate material which forms an electrode with the method of Embodiment 1 The top view which shows the other example of the board | substrate material which forms an electrode with the method of Embodiment 1 The schematic cross-sectional view of the portion where the light-receiving surface bus electrode is drawn and the surrounding area in the printer of the first embodiment Schematic cross-sectional view of the stage portion of the screen printer used for forming the light receiving surface grid electrode in the first embodiment Enlarged view of FIG. Table comparing the performance of the solar battery cell produced by the method of the comparative example and the performance of the solar battery of the first embodiment Comparison diagram comparing the weight of the paste applied to the light-receiving surface bus electrode of the solar battery cell produced by the method of the comparative example and the coating weight of the first embodiment. Comparative diagram showing relative values in the first embodiment when the manufacturing cost by the method of the comparative example is divided into three items of paste, printing mask, and printing machine and each is set to 1. Model sectional drawing explaining the procedure of the manufacturing method of the solar cell module by Embodiment 1 Model sectional drawing explaining the procedure of the manufacturing method of the solar cell module by Embodiment 1 Sectional drawing which shows the photovoltaic cell formed by the method of Embodiment 2. Schematic plan view of a stage portion of a printing press used in the electrode forming method of Embodiment 3

Hereinafter, embodiments of a solar cell according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment, In the range which does not deviate from the summary of this invention, it can change suitably. In the drawings shown below, the scale of each member may be different from the actual scale for easy understanding. The same applies between the drawings.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a surface that is a light-receiving surface of a solar cell including electrodes formed by the solar cell electrode forming method according to the first embodiment of the present invention. FIG. 2 is a diagram showing a back surface opposite to the light receiving surface of the solar cell shown in FIG. 3 is a sectional view taken along the line III-III in FIGS. 1 and 2, and FIG. 4 is a sectional view taken along the line IV-IV in FIGS.

The light receiving surface 1A of the solar battery cell 10 is provided with a light receiving surface electrode 4 as a first current collecting electrode including a light receiving surface grid electrode 4G and a light receiving surface bus electrode 4B. The light receiving surface grid electrode 4G and the light receiving surface bus electrode 4B are orthogonal to each other. Further, the back surface 1B of the solar battery cell 10 is provided with a back electrode 4 as a second collector electrode composed of a back surface aluminum electrode 5A and a back surface bus electrode 5B. The horizontal direction indicated by the arrow X in FIGS. 1 and 2 is the longitudinal direction of the light receiving surface grid electrode 4G, and the vertical direction indicated by the arrow Y in FIGS. 1 and 2 is the light receiving surface bus electrode 4B and the back surface bus electrode 4B. It is the longitudinal direction.

The present embodiment is characterized in that when the light-receiving surface bus electrode is formed, a paste including a conductive material as an electrode material is applied to the electrode forming surface of the substrate material without using a printing mask. In the coating process, the paste is applied using a liquid ejection device while controlling the amount of coating per hour while maintaining a constant pressure detected by a pressure sensor installed on the stage on which the substrate material is placed.

FIG. 3 is a cross-sectional view of the main part of the solar battery cell 10 according to the first embodiment of the present invention, and is a cross-sectional view taken along the line III-III in FIGS. FIG. 4 is a cross-sectional view of a main part of the solar battery cell 10 according to the first embodiment of the present invention, and is a cross-sectional view taken along the line IV-IV in FIGS. FIG. 3 is a cross section where the light receiving surface grid electrode 4G is not present, and FIG. 4 is a view illustrating a cross section where the light receiving surface grid electrode 4G is present. In the figure, the upper side is the light receiving surface 1A. In the solar cell 10, the n-type impurity diffusion layer 2 is formed on the upper surface of the p-type single crystal silicon substrate 1 by phosphorus diffusion to form a photoelectric conversion unit having a pn junction. An antireflection film 3 is formed on the upper side of the n-type impurity diffusion layer 2. On the antireflection film 3, a light receiving surface bus electrode 4B is provided. The antireflection film 3 under the light receiving surface bus electrode 4B is melted by baking, and the light receiving surface bus electrode 4B is in electrical contact with the n-type impurity diffusion layer 2. On the back surface 1B side of the p-type single crystal silicon substrate 1, a back aluminum electrode 5A and a back bus electrode 5B are provided. 3 shows a cross section along the longitudinal direction of the light receiving surface grid electrode 4G in the region between the adjacent light receiving surface grid electrodes 4G, the light receiving surface grid electrode 4G is not shown.

Next, a process for manufacturing the solar battery cell 10 shown in FIGS. 1 to 4 will be described. In addition, since the process demonstrated here is the same as the manufacturing process of the general photovoltaic cell using a silicon substrate, it does not show in particular in figure.

First, the p-type single crystal silicon substrate 1 is immersed in a heated aqueous solution of sodium hydroxide. As a result, the surface of the p-type single crystal silicon substrate 1 is etched, and a minute uneven structure is formed on the surface layer of the p-type single crystal silicon substrate 1.

Next, the p-type single crystal silicon substrate 1 is put into a thermal oxidation furnace and heated in the presence of phosphorus oxychloride (POCl ₃ ) vapor. As a result, phosphorus glass is formed on the surface of the p-type single crystal silicon substrate 1, phosphorus is diffused into the p-type single crystal silicon substrate 1, and an n-type impurity diffusion layer 2 is formed on the surface layer of the p-type single crystal silicon substrate 1. It is formed.

Next, after removing the phosphorus glass layer of the p-type single crystal silicon substrate 1 in a hydrofluoric acid solution, a silicon nitride film (SiN film) is formed on the n-type impurity diffusion layer 2 as the antireflection film 3 by, for example, plasma CVD. Form. The film thickness and refractive index of the antireflection film 3 are set to values that most suppress light reflection. Note that two or more layers having different refractive indexes may be stacked. The antireflection film 3 may be formed by a different film forming method such as a sputtering method.

Next, a paste mixed with aluminum is printed on the entire back surface 1B of the p-type single crystal silicon substrate 1 by screen printing.

Further, a paste mixed with silver is printed on the light-receiving surface 1A of the p-type single crystal silicon substrate 1 by comb-screen printing to form a light-receiving surface grid electrode 4G, and then the coating apparatus shown in FIGS. 5 and 6 The light-receiving surface bus electrode 4B is applied using After the light-receiving surface bus electrode 4B is applied, the light-receiving surface electrode 4 and the back electrode 5 are formed by performing a baking process. On the light-receiving surface 1A of the p-type single crystal silicon substrate 1, the antireflection film 3 under the light-receiving surface electrode 4 is melted by baking, and the light-receiving surface electrode 4 is in electrical contact with the n-type impurity diffusion layer 2. As described above, the solar cell shown in FIGS. 1 to 4 is manufactured.

Next, a method for forming the light-receiving surface bus electrode among the electrode forming methods for solar battery cells according to the present embodiment will be described. FIG. 5 is a schematic diagram illustrating a printing machine used in the electrode forming method of the present embodiment, and is used in a printing process for forming electrodes without using a printing mask. FIG. 6 is a schematic cross-sectional view of the stage portion. FIG. 7 is a schematic plan view of a stage portion of the printing machine, and FIGS. 8A and 8B are a top view and a side view showing a pressure sensor. In this printing process, the paste 4P is applied to the electrode forming surface of the substrate material without using a printing mask.

The pressure sensor 109 used in the present embodiment is a small pressure transducer that uses a strain gauge that has a bridge formed therein and has a small thin wall structure, and is a small device that detects a change in capacitance caused by strain. These pressure sensors 109 have a diaphragm-like shape in which pressure-sensitive portions 109a arranged at regular intervals are fixed to a diaphragm-like plate provided so as to face a cavity provided in a stage using a conductive adhesive. The output can be taken out through the wiring pattern 109b provided on the plate. Rather than disposing the pressure sensors 109 individually, a diaphragm-like plate is formed of a single crystal silicon substrate, and each pressure-sensitive portion of the pressure sensor and the wiring pattern are integrated on the silicon substrate using a thin film process. You may use what was formed.

9 and 10 are plan views showing examples of substrate materials for forming electrodes by the method of the present embodiment. As the substrate material, for example, a square shape shown in FIG. 9 or a rounded quadrangular shape in which the four corners of the square are arc shapes as shown in FIG. 10 is used. The one side M of the square shape shown in FIG. 9 and the one side equivalent width M of the rounded square shape shown in FIG. 10 are, for example, 156 mm.

As the substrate material, for example, a silicon wafer that is a thin plate-like silicon is used. The substrate material may be any material as long as the electrode can be formed by a usual screen printing process, and the substrate material used in the usual method. There is no difference between

As shown in FIG. 5, the printing machine according to the present embodiment includes a print head 101 including a liquid ejection unit 102 that ejects paste 4 </ b> P constituting an electrode material, and a pn junction that is a substrate material, that is, a solar cell substrate. And a stage 104 on which the formed p-type single crystal silicon substrate 1 is placed. A discharge nozzle 103 is provided at the tip of the liquid discharge unit 102, and the paste 4P adjusted to a desired viscosity is discharged from the discharge nozzle 103. The stage 104 is a so-called XY table, and coordinates can be designated by a signal from the control unit 105 and can be continuously scanned. The printing machine also includes a print head 101 for disposing the liquid discharge unit 102 above the stage 104. The print head 101 can also be scanned by a signal from the control unit 105.

The printing machine scans the stage 104 on which the liquid discharge unit 102 filled with the paste 4P arranged in the print head 101 and the solar cell substrate 1S are placed in accordance with a pre-programmed print pattern, and thereby for solar cells. The paste 4P is applied to the electrode forming surface of the substrate 1S. Here, the substrate 1S for solar cells refers to a substrate in which a pn junction is formed on the p-type single crystal silicon substrate 1 and an antireflection film 3 is formed.

FIG. 6 is an enlarged schematic cross-sectional view of the stage portion of the printing press. Here, a case where the light receiving surface bus electrode 4B is formed on the solar cell substrate 1S is taken as an example. When this embodiment is applied to the formation of the light receiving surface bus electrode 4B, the light receiving surface grid electrode 4G is formed in advance, or the light receiving surface grid electrode 4G is formed after the light receiving surface bus electrode 4B is formed. Further, when forming the light receiving surface grid electrode 4G, it may be formed by a screen printing method which is a conventional method conventionally used, or the electrode forming method of the present embodiment may be used.

In FIG. 6, the solar cell substrate 1 </ b> S is placed on the stage 104. The stage 104 is provided with a suction unit 108 that constitutes a suction mechanism 107 that performs air suction, and the solar cell substrate 1S is fixed to the stage 104 by exhausting the suction holes with a vacuum pump. Further, the stage 104 is provided with a plurality of pressure sensors 109 corresponding to the positions along the light receiving surface bus electrode 4B of the solar battery cell 10. The liquid discharge portion 102 disposed in the print head 101 is filled with the paste 4P, and the paste 4P provided at the tip of the liquid discharge portion 102 is pushed out from the discharge nozzle 103, whereby the electrode forming surface of the solar cell substrate 1S. A pattern of the light receiving surface bus electrode 4B programmed in advance is drawn on the light receiving surface 1A.

The liquid discharge unit 102 can control the application amount per hour by the control unit 105 of the printing press, and can apply uniformly and uniformly. The pressure sensed by the pressure sensor 109 provided in the stage 104 is fed back to the liquid ejection unit 102 through the control unit 105, and the coating amount is controlled so that drawing can be performed while always maintaining a constant pressure.

The material, size, and shape of the discharge nozzle 103 mounted on the liquid discharge unit 102 are properly selected depending on the line to be drawn. Typical materials used for the discharge nozzle 103 include metals such as stainless steel and resins such as polyethylene. Further, the nozzle diameter is selected according to the line width to be drawn, and the nozzle shape is selected from a normal round shape, a square shape, a branch nozzle, a multiple nozzle, a flat nozzle, and the like.

According to the present embodiment, the light-receiving surface grid electrode 4G is formed in advance by a screen printing method, and the solar cell substrate 1S subjected to the drying process is placed on the stage 104 and fixed by the suction unit 108. Next, the light receiving surface bus electrode 4B is drawn on the light receiving surface 1A of the solar cell substrate 1S so as to be orthogonal to the light receiving surface grid electrode 4G in accordance with a pre-programmed print pattern. In this embodiment, the width of the light-receiving surface bus electrode 4B is 1 mm, and the light-receiving surface grid electrode 4G is formed in advance, so that the applied nozzle has a high-density polyethylene tapered nozzle 0.8φ diameter. Thus, the light-receiving surface bus electrode 4B can be formed by supplying the paste 4P directly from the ejection nozzle 103 without using a printing mask.

FIG. 7 is a schematic view showing the surface of the stage 104 on which the pressure sensors 109 are arranged, and FIG. 6 corresponds to a CC section of FIG. In the present embodiment, twelve pressure sensors 109 are provided along the light receiving surface bus electrode 4B formation region R _4B, and suction portions 108 each including a suction hole are provided. The solar cell substrate 1S is fixed horizontally by the suction unit 108, and a plurality of pressure sensors 109 are arranged at regular intervals. Therefore, by measuring the output of the pressure sensor 109, the pressure resulting from the supply amount of the paste 4P for forming the light receiving surface bus electrode 4B is detected. The output of the pressure sensor 109 is fed back to the control unit 105, and the supply amount of the paste 4P from the discharge nozzle 103 is controlled.

FIG. 11 is a schematic cross-sectional view of a portion where the light-receiving surface bus electrode 4B is drawn and its periphery in the printer of the first embodiment. The paste 4P is discharged from the discharge nozzle 103 of the liquid discharge unit 102 while controlling the discharge amount per time, and the light receiving surface bus electrode 4B is drawn. At that time, the height of the discharge nozzle 103 of the liquid discharge unit 102 is controlled so as to be always constant at a pressure detected by the pressure sensor 109 installed on the stage 104 along the drawing position, for example, 0.9 kg / cm ^2. By doing so, it is possible to perform drawing while finely changing the discharge amount.

FIG. 12 is a schematic cross-sectional view of the stage portion of the screen printer used for forming the light-receiving surface grid electrode 4G in the present embodiment. In the screen printing process, the paste 4GP is applied to the electrode forming surface of the solar cell electrode 1S through the printing mask 202. FIG. 13 is an enlarged view of FIG. 12 and 13 includes a stage 104 on which the solar cell substrate 1S is placed, and the stage 104 includes a suction unit 108 for fixing the solar cell substrate 1S. The suction unit 108 fixes the solar cell substrate 1 </ b> S to the stage 104 by sucking air at the stage 104. The printing mask 202 includes a mask frame 203, warp yarns 200A, and weft yarns 200B, and includes a screen mesh 200 attached to the printing surface side of the mask frame 203 and a photosensitive emulsion 200S. In FIG. 13, the stage 104 and the mask frame 203 are omitted.

The printing machine applies the paste 4GP to the electrode formation surface of the solar cell substrate 1S through the printing mask 202 by scanning the squeegee 201 on the printing mask 202 on which the paste 4GP is placed. In the portion of the printing mask 202 covered with the photosensitive emulsion 200S, the paste 4GP is not allowed to pass, and the portion where the screen mesh 200 is exposed is allowed to pass the paste 4GP. The light receiving surface grid electrode 4G is formed by transferring onto the electrode forming surface.

The paste 4GP includes a conductive material that is an electrode material. Typical conductive materials used for the paste 4GP include metal materials such as gold, silver, copper, platinum and palladium. The paste includes one or more of these conductive materials.

In the electrode forming method of the first embodiment, it is possible to select the optimum pastes 4GP and 4P for the light receiving surface grid electrode 4G and the light receiving surface bus electrode 4B. In the present embodiment, it is possible to reduce the amount of coating required for the light-receiving surface bus electrode 4B. Incidentally, in the usual method, since the light receiving surface grid electrode 4G and the light receiving surface bus electrode 4B are collectively formed, the weight of the paste applied to the light receiving surface bus electrode 4B through the printing mask 202 is determined by the weight of the light receiving surface grid. It is determined by a mask specification for expressing the performance of the electrode 4G. On the other hand, in this embodiment, optimization can be achieved by forming each independently.

In addition, in the specification of the optimum paste for the light receiving surface bus electrode 4B, it is possible to express its function with a smaller amount of conductive material than the paste used in the light receiving surface grid electrode 4G because of the required performance. is there. That is, this is nothing but reducing the total price of the pastes 4GP and 4P. Therefore, by separately forming the light receiving surface grid electrode 4G and the light receiving surface bus electrode 4B, it is possible to reduce the cost from both sides in terms of coating amount and price.

On the other hand, in the comparative example, since the light receiving surface grid electrode 4G and the light receiving surface bus electrode 4B are normally formed in a lump, the specifications of the print mask 202 and the paste are set uniformly. However, the performance required for the light receiving surface grid electrode 4G and the light receiving surface bus electrode 4B is not the same. The former is to collect the current generated in the solar cell substrate 1S, and the latter is to flow the collected current through the tab wire. For this reason, it is excessive quality to use a paste adjusted to maximize the performance of the light receiving surface grid electrode 4G for the light receiving surface bus electrode 4B, which is expensive.

FIG. 14 is a table comparing the performance of the solar battery cell produced by the method of the comparative example and the performance of the solar battery of the first embodiment. Compared with the method of the comparative example, the voltage (Voc) was improved by ² mV, the current (Jsc) was improved by 0.2 mA / cm ^2, and the fill factor (FF) was reduced by 3/1000. As a result, the efficiency (Eff) was 0.1 %improves.

FIG. 15 is a comparative diagram comparing the weight of the paste applied to the light-receiving surface bus electrode 4B of the solar battery cell produced by the method of the comparative example and the applied weight of the first embodiment. In the paste 4P for the light-receiving surface bus electrode 4B used in the present embodiment, the amount of the conductive material contained is 30% of the amount of the conductive material contained in the paste for the light-receiving surface bus electrode 4B of the comparative example. Reduced.

In the method of the comparative example, the coating amount was 0.05 g, but in the method of the present embodiment, the coating amount was 0.012 to 0.034 g. In any case, the coating amount could be reduced as compared with the method of the comparative example. is there. Although the performance of the solar cell thus produced was lower than the method of the comparative example under condition 1 in FIG. 15, the results were equivalent to or higher than the method of the comparative example under

conditions

2 and 3, and in FIG. Even in the condition 3 according to the present embodiment shown, the amount of paste applied in the method of the comparative example is reduced by 30%, and this is achieved by the paste 4P obtained by reducing the conductive material by 30%.

FIG. 16 shows the relative value of the manufacturing cost by the method of the first embodiment when the manufacturing cost in the method of the comparative example is divided into three items of paste, printing mask, and printing machine and each is set to 1. FIG. In the present embodiment, the electrode manufacturing method of the present embodiment is applied to the light-receiving surface bus electrode 4B, and the conventional method is applied to the light-receiving surface grid electrode 4G. The paste is reduced in cost, and the printing mask is changed. None, printing presses are costly. However, under certain conditions, the introduction cost is recovered in about one year even when the printing press according to the present embodiment is additionally introduced by improving the output of the solar battery cell and reducing the cost and amount of use of the paste. After that, it will be profitable. In FIG. 16, the terminology is omitted such that the light receiving surface bus electrode paste is a light receiving surface bus paste, and the light receiving surface bus electrode printer is a light receiving surface bus printer.

The paste applied to the solar cell substrate 1S becomes an electrode by a process generally called firing. In the baking step, heat treatment is performed so that the peak temperature is 800 ° C. or lower, desirably 720 ° C. to 770 ° C. The heat treatment time in the firing furnace is generally within 2 minutes.

17 and 18 are schematic cross-sectional views for explaining the procedure of the method for manufacturing the solar cell module according to the present embodiment. First, a plurality of solar cells 10 having current collecting electrodes formed on the light receiving surface side and the back surface side are connected by tab wires 20. As shown in FIG. 17, the solar cell 10 with wiring is sandwiched between the translucent substrate 22 and the back sheet 23 via the

translucent resin members

21A and 21B, and these members are pressure-bonded. As shown in FIG. 18, the translucent resin member 21 in which the solar cell 10 with wiring is sealed, the translucent substrate 22, and the back sheet 23 are integrated. A solar cell module is produced. A solar battery module having high power generation efficiency can be obtained by using the solar battery cell 10 including the electrode formed by the above electrode forming method.

In this embodiment, a translucent resin member 21B is installed on the translucent substrate 22. On the translucent resin member 21B, the solar cell 10 with wiring is installed. In the solar cell 10 with wiring, the predetermined number of solar cells 10 shown in FIG. 1 are arranged in parallel, and the adjacent solar cells 10 are connected to each other by a tab wire 20 made of a conductive wire such as a soldered copper wire. To make. The solar cell 10 with wiring is installed on the translucent resin member 21B with the back surface of each solar cell 10 facing upward.

On the solar cell 10 with wiring, a translucent resin member 21A and a back sheet 23 are further installed. FIG. 18 shows a state in which the light-transmitting substrate 22, the light-transmitting resin member 21, the solar cell 10 with wiring, the light-transmitting resin member 21, and the back sheet 23 are stacked in order from the bottom of the figure. Yes.

It is desirable to use a vacuum thermocompression bonding device called a laminator for the heating and pressure bonding treatment in the production of the solar cell module. The laminator heats and deforms the translucent resin member 21 or the back sheet 23 and further thermosets them so as to integrate the solar cells in the translucent resin member 21.

The vacuum thermocompression bonding apparatus heats and crimps each member in a reduced pressure environment. Thereby, between the translucent board | substrate 22 and the translucent resin member 21, between the translucent resin member 21 and the photovoltaic cell 10 with wiring, between the photovoltaic cell 10 with wiring and the translucent resin member 21, With respect to any of the space between the light-sensitive resin member 21 and the back sheet 23, it is possible to prevent voids and bubbles from remaining and to press-bond each member with a uniform pressure.

The heating and pressure-bonding treatment in the vacuum thermocompression bonding apparatus is performed at a temperature of 200 ° C. or lower, preferably 150 ° C. to 200 ° C. It is assumed that the temperature in the heating and pressure bonding processes can be changed as appropriate depending on the material of the translucent resin member 21 and the like.

As the translucent substrate 22, for example, a glass substrate is used. The translucent board | substrate 22 should just be what can permeate | transmit sunlight, and is good also as what consists of materials other than glass. The translucent resin member 31 is one of resins such as ethylene vinyl acetate, polyvinyl butyral, epoxy, acrylic, urethane, olefin, polyester, silicon, polystyrene, polycarbonate, and rubber. Contains one or more. As long as the translucent resin member 21 can transmit sunlight, any material other than those listed here may be used.

As the back sheet 23, a sheet made of one or a plurality of resins such as polyester, polyvinyl, polycarbonate, and polyimide is used. The back sheet 23 may be made of any material other than those listed here as long as it has sufficient strength, moisture resistance and weather resistance for protecting the solar cell module. The back sheet 23 may be made of not only a resin material but also a composite material obtained by bonding metal foil materials in order to improve strength, moisture resistance, and weather resistance. Further, the back sheet 23 may be formed by laminating a metal material having a high reflectance or a translucent member having a high refractive index on the surface of the resin material by a film forming method such as vapor deposition. .

The end face of the solar cell module may be protected with a tape made of a resin material such as a rubber-based resin member in order to improve the adhesion of the laminating process and prevent intrusion of moisture and the like from the outside. As the rubber-based resin member, for example, a rubber material such as butyl rubber is used. Furthermore, the solar cell module may be provided with a frame surrounding the outer periphery in view of ease of handling as a structure. The frame is configured using a metal member such as aluminum or an aluminum alloy, for example.

This embodiment is very useful industrially because high-performance solar cells and solar cell modules can be obtained by a simple method without requiring expensive equipment.

According to the first embodiment, the cost for the printing mask becomes unnecessary by not using the printing mask. Moreover, a desired electrode can be formed by a system cheaper than a screen printer. In the electrode formation, the paste can be applied while controlling the amount of application per time, so that the necessary amount of paste can be discharged to the electrode formation position. This makes it possible to supply the necessary and sufficient paste to improve the characteristics and reduce the amount of paste to be supplied as a result. In other words, it is possible to form solar cell electrodes that combine cost reduction and efficiency improvement. And Further, the electrode forming method of the first embodiment is a simple and inexpensive method, and the design change can be made to the arrangement of the electrode pattern or the line width and thickness by replacing the conventional method or adding to the conventional method. Even if there is, it can be carried out immediately and a reliable electrode can be easily formed.

According to the present embodiment, as is clear from FIG. 4, the light receiving surface bus electrode 4B and the light receiving surface grid electrode 4G are not in contact with each other but are in contact with each other. In addition, it is possible to secure a battery area without increasing the light shielding region and to form a light receiving surface electrode excellent in current collection.

The light receiving surface grid electrode 4G is formed by screen printing, and only the light receiving surface bus electrode 4B is formed while controlling the discharge amount using the liquid discharge unit 102 without using a screen. Also, the liquid discharge unit 102 may be used to control the discharge amount.

In addition, although the application amount is controlled while measuring the weight after application using a pressure sensor, the pressure sensor is not essential if the discharge amount of the liquid discharge unit 102 can be controlled. Instead of the pressure sensor, the supply amount can be controlled by adjusting the scanning speed of the stage so that the supply amount can be adjusted and the supply amount can be controlled with higher accuracy. is there.

The control unit can efficiently draw the bus electrode while maintaining a highly accurate line width and position by controlling the supply amount of the paste from the discharge nozzle from 0.1 ml to 1 ml per minute. . In particular, the supply amount of the paste from the discharge nozzle is desirably controlled within a range of 0.1 ml to 0.3 ml per minute, and the bus electrode is drawn, thereby forming a highly accurate bus electrode without using a pressure sensor. Is realized. In the case of supplying paste without using a pressure sensor, it is possible to draw a highly accurate bus electrode pattern by controlling the supply amount with high accuracy from 0.1 ml to 1 ml per minute. In particular, by drawing the bus electrode pattern while controlling the supply amount of paste from the discharge nozzle, that is, the discharge amount, from 0.1 ml to 0.3 ml per minute, the supply amount of the bus electrode can be reduced by 30% of the conventional application amount. A pattern can be drawn. Therefore, it is possible to provide an electrode with high accuracy and a small amount of paste. Incidentally, under a certain condition, the coating amount of 0.012 g corresponds to that applied at about 0.1 ml / min, and the coating amount of 0.034 g corresponds to that applied at about 0.3 ml / min. Furthermore, as described above, the discharge amount can be finely adjusted by adjusting the height of the discharge nozzle. Even when a pressure sensor is used, more accurate control is possible by drawing the pattern of the bus electrode while controlling the discharge amount of paste from the discharge nozzle at a rate of 0.1 to 0.3 ml per minute. .

In addition, as shown in FIG. 7, the plurality of pressure sensors are arranged at regular intervals along the center line of the bus electrode formation region, thereby detecting the paste supply amount to the bus electrode with high accuracy. And reliable control becomes possible.

Embodiment 2. FIG.
Next, a method for forming a light-receiving surface bus electrode among the electrode forming methods for solar battery cells according to the second embodiment will be described. FIG. 19 is a cross-sectional view showing a solar battery cell formed by the method of the second embodiment. About a light-receiving surface and a back surface, it is the same as that of a solar cell provided with the electrode formed by the electrode formation method of the solar cell concerning Embodiment 1 of this invention shown in FIG.1 and FIG.2. 19 is a cross-sectional view corresponding to the III-III cross-sectional view of FIGS.

In the light receiving surface 1A of the solar battery cell, four through grooves V parallel to each other are provided in the bus electrode formation region, and the light receiving surface bus electrode 4B is provided in the through groove V. Since other configurations are the same as those of the solar cell of the first embodiment, description thereof is omitted here. In this printing process, the paste 4P is supplied and applied so as to fill the through grooves V formed on the electrode forming surface of the substrate material without using a printing mask.

The subsequent process is the same as that in the first embodiment. Also in the present embodiment, the light-receiving surface bus electrode 4B and the light-receiving surface grid electrode 4G filled in the through groove V are in contact with each other without climbing on each other.

With this configuration, it is possible to form a light-receiving surface electrode that can secure a battery area without waste of electrode material and increase the light-shielding area and has excellent current collecting performance, as compared with the first embodiment. Is possible.

Embodiment 3 FIG.
Next, a printing machine used in the method for forming the light-receiving surface bus electrode among the electrode forming methods for solar battery cells according to the third embodiment will be described. FIG. 20 is a schematic plan view of a stage portion of a printing machine used in the electrode forming method of the third embodiment. In the present embodiment, the pressure sensors 109 are arranged at regular intervals along the light receiving surface bus electrode formation region R _4B . The pressure sensor 109 is disposed so as to be positioned in the light receiving surface bus electrode formation region R _4B , and the detection value of the pressure sensor 109 that changes when the paste for forming the light receiving surface bus electrode 4B is supplied from the discharge nozzle is constant. The discharge amount is controlled so that The control of the discharge amount from the discharge nozzle 103 is performed by the control unit 105 of the coating apparatus as in the first embodiment shown in FIG.

The arrangement of the suction portion 108 and the pressure sensor 109, each consisting of a suction hole, is different from the stage portion of the printing press of the first embodiment shown in FIG. 7, and the other portions are the same as those of the first embodiment. Therefore, the description is omitted here.

According to the printer of the third embodiment, since the pressure sensors 109 are arranged at equal intervals along the center line of the light receiving surface bus electrode formation region R _4B , the supply amount can be controlled more reliably. It becomes.

The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

1 p-type single crystal silicon substrate, 1S substrate for solar cell, 2 n-type impurity diffusion layer, 3 antireflection film, 4 light receiving surface electrode, 4G light receiving surface grid electrode, 4B light receiving surface bus electrode, 5 back electrode, 5A back aluminum Electrode, 5B Back bus electrode, 10 Solar cell, 20 Tab line, 21, 21A, 21B Translucent resin member, 22 Translucent substrate, 23 Back sheet, 101 Print head, 102 Liquid ejector, 103 Discharge nozzle, 104 stage, 105 control unit, 107 suction mechanism, 108 suction unit, 109 pressure sensor, 4P paste, 203 mask frame, 200 screen mesh, 200S photosensitive emulsion, 201 squeegee, 200A warp, 200B weft, 202 printing mask.

Claims

Forming a pn junction on a semiconductor substrate to form a solar cell substrate;
A solar cell comprising: an application step of applying a paste containing a conductive material that is an electrode material to an electrode formation surface of the solar cell substrate; and an electrode formation step including a firing step of firing the applied paste. A manufacturing method comprising:
In the application step, the paste is applied to the electrode formation surface while controlling the application amount by the discharge amount per time from the discharge nozzle using a liquid application apparatus having a discharge nozzle for discharging the paste. The manufacturing method of the solar cell characterized by including a process.
The electrode forming step includes
Forming grid electrodes distributed on the electrode forming surface;
Forming a bus electrode that collects and collects the charges collected by the grid electrode,
The method of manufacturing a solar cell according to claim 1, wherein the step of forming the bus electrode includes a step of applying the paste using the liquid application device.
The step of forming the bus electrode includes the step of placing the paste on the solar cell substrate by a pressure sensor provided along a bus electrode formation region for forming the bus electrode of the stage for mounting the solar cell substrate. Measuring the pressure sensed during application;
The method for manufacturing a solar cell according to claim 2, further comprising: a control step of controlling the discharge amount from the discharge nozzle until a measurement value measured by the pressure sensor becomes constant.
The said application | coating process includes the process of controlling the said discharge amount from the said discharge nozzle between 0.1 ml per minute and 0.3 ml, The any one of Claim 1 to 3 characterized by the above-mentioned. A method for manufacturing a solar cell.
a solar cell substrate having a pn junction;
A first current collecting electrode formed on the first main surface of the solar cell substrate;
A solar cell comprising a second current collecting electrode formed on the first main surface or the second main surface of the solar cell substrate;
Of the first and second collector electrodes, a collector electrode formed on the light receiving surface side,
Grid electrodes distributed on the first main surface or the second main surface;
Collecting the charges collected by the grid electrode together, including a bus electrode having a thickness larger than the grid electrode,
The solar cell, wherein the grid electrode has a side surface in contact with a side surface of the bus electrode in a thickness direction.
The solar cell according to claim 5, wherein the grid electrode is formed of a material different from that of the bus electrode.
The solar cell according to claim 5 or 6, wherein the bus electrode is formed in a recess formed in the first or second main surface of the solar cell substrate.
A solar cell manufacturing apparatus provided with a liquid application device that applies a paste containing a conductive material as an electrode material to an electrode formation surface of a substrate material on an electrode formation surface of a solar cell substrate having a pn junction,
The liquid coating apparatus is
A stage for mounting the solar cell substrate;
A discharge nozzle for discharging the paste;
A solar cell manufacturing apparatus, comprising: a discharge control unit that controls a coating amount of the paste from the discharge nozzle per unit time.
The stage includes a plurality of pressure sensors arranged along a bus electrode formation region for forming a bus electrode,
The solar cell according to claim 8, wherein the discharge control unit controls the application amount so that a pressure detected when the pressure sensor applies the paste is constant. Manufacturing equipment.
The stage includes a suction portion including a suction hole for supporting the solar cell substrate;
The solar cell manufacturing apparatus according to claim 8 or 9, further comprising the plurality of pressure sensors arranged so as to avoid the adsorption portion.
The solar cell manufacturing apparatus according to claim 10, wherein the plurality of pressure sensors are arranged at regular intervals along a center line of the bus electrode formation region.
12. The solar cell according to claim 8, wherein the discharge control unit controls the discharge amount from the discharge nozzle between 0.1 ml and 0.3 ml per minute. Manufacturing equipment.