JPWO2018150598A1 - Method of manufacturing solar cell and solar cell - Google Patents

Abstract

In a method of manufacturing a solar cell, the method includes the step of applying a paste containing a conductive material which is an electrode material to the electrode forming surface of the solar cell substrate, and the coating step enables position control of the solar cell substrate. A substrate mounting process for mounting on the stage (104), a first direction control process for controlling the position of the stage (104) in the first direction, and a position of the stage (104) in the second direction orthogonal to the first direction Control the amount of paste applied to the electrode formation surface while controlling the amount of application per unit time of discharge from the discharge nozzle (103) using a liquid application device equipped with a discharge nozzle (103) for discharging paste. And a paste discharge process for applying.

Description

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

  With regard to the manufacture of a conventional solar cell, Patent Document 1 adopts the following procedure. First, on the surface of a substrate material such as silicon, the reflection angle of sunlight on the substrate surface is changed, and a concavo-convex structure called a texture for taking in reflected light into the substrate is formed by a method such as etching. Next, a pn junction is formed by a method such as diffusion, and in order to reduce reflection of sunlight by a light interference effect, an antireflective 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. Do. Next, a conductive paste, such as a metal paste, which is an electrode material, is applied on the antireflective film in a desired pattern, and the paste is heated to melt the antireflective film by the glass contained in the paste. Baking is performed to form an electrode by taking electrical contact with it. Furthermore, the substrate material is immersed in an etching solution that dissolves the glass component, and the glass component contained in the electrode is dissolved to reduce the electrical resistance of the electrode.

  The electrode material is generally called a paste, and is composed of a combination of a conductive material mainly composed of metal powder, an inorganic material which is a glass component, an organic material which 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 screen printing, and the antireflective film is melted with a glass component contained by a heating process called baking to obtain electrical conductivity with the substrate material. The junction is taken to form an electrode.

  Silver is usually used as the conductive material, but it is also a noble metal, is easily influenced by the market price, and is not inexpensive. However, the performance of the solar cell is largely attributable to the electrode made of this silver paste, and the electrode with other materials is not the mainstream of the world. Therefore, among manufacturers who develop, manufacture and sell this paste, how to produce solar cells with high efficiency with how small amount of paste and how small amount of silver is competing every day Is the current situation.

  Usually, on the surface of the solar cell, thin grid electrodes for collecting the generated current, and thick bus electrodes for connection between the substrates are disposed orthogonal to it, and these are collectively processed by the screen printing method. And molding methods are the mainstream. The improvement of the paste performance is the formation of a thin and high grid electrode, which is different from the thinness required for the bus electrode, that is, the molding which suppresses the coating amount. Therefore, in recent years, the grid electrode and the bus electrode are each independently made Methods for molding are being considered.

  Moreover, in the manufacturing method of the conventional solar cell module, a solar cell module is formed by joining the several photovoltaic cell by which the current collection electrode was formed in the light-receiving surface side and back surface side by a tab wire. On the light receiving side, the tab line is electrically and mechanically joined to the bus electrode. Therefore, as shown in Patent Document 2, the shape of the bus electrode is also studied from the viewpoint of the mechanical strength of the solar cell module.

Patent No. 4486622 Patent No. 4284368

  Although it is effective to reduce the amount of electrode paste used for the bus electrode in order to reduce the manufacturing cost of the solar cell, the problem is that if the amount of electrode paste used for the bus electrode is reduced, the bonding strength of the tab wire is reduced. there were.

  The present invention is made in view of the above, and an object of the present invention is to realize low-cost electrode formation on a solar cell without reducing the mechanical strength of the solar cell module.

  In order to solve the problems described above and to achieve the object, the method of manufacturing a solar cell according to the present invention comprises the steps of: forming a pn junction on a semiconductor substrate to form a solar cell substrate; And an electrode forming step including a coating step of applying a paste containing a conductive material to the electrode forming surface of the solar cell substrate, and a firing step of firing the applied paste. The coating process includes a substrate mounting process for mounting the solar cell substrate on a position controllable stage, a first direction control process for controlling the position of the stage in the first direction, and a stage orthogonal to the first direction. The paste is applied to the electrode forming surface while controlling the application amount by the discharge amount per time from the discharge nozzle using a liquid application device having a discharge nozzle for discharging the paste while controlling the position in the second direction And a paste discharging step.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to implement | achieve low-cost electrode formation in a photovoltaic cell, without reducing the mechanical strength of a solar cell module.

The figure which shows the surface which is a light-receiving surface of a photovoltaic cell provided with the electrode formed of the electrode formation method of the photovoltaic cell concerning Embodiment 1 The figure which shows the back surface on the opposite side to a light-receiving surface about the photovoltaic cell shown in FIG. V-V cross section of FIG. 1 and FIG. 2 WW sectional drawing of FIG. 1 and FIG. 2 Partial perspective view of the light receiving surface electrode of the solar battery cell according to the first embodiment Sectional drawing of the light-receiving surface electrode of the solar battery cell concerning Embodiment 1. Schematic diagram for explaining a printing machine used for the electrode forming method of Embodiment 1. A schematic cross-sectional view of a stage portion of a printing press used for the electrode forming method of Embodiment 1. A schematic cross-sectional view of a portion where the light receiving surface bus electrode is drawn and the periphery in the printing press of the first embodiment Flow chart of the coating process of Embodiment 1 A schematic cross-sectional view of a stage portion of a screen printing machine used to form a light receiving surface grid electrode in Embodiment 1. An enlarged view of FIG. 11 Table comparing the performance of the solar battery cell manufactured by the method of the comparative example and the performance of the solar battery cell of the first embodiment The comparison figure which compared the weight of the paste apply | coated to the light-receiving surface bus electrode of the photovoltaic cell produced by the method of the comparative example, and the application weight of Embodiment 1 Comparison chart showing the relative values in 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. A schematic cross-sectional view for explaining the procedure of the method of manufacturing a solar cell module according to Embodiment 1. A schematic cross-sectional view for explaining the procedure of the method of manufacturing a solar cell module according to Embodiment 1. Cross-sectional view of a solar cell according to a second embodiment Sectional drawing of the light-receiving surface electrode of the photovoltaic cell concerning Embodiment 2.

  Below, embodiment of the photovoltaic cell concerning this invention is described in detail based on drawing. The present invention is not limited by the embodiment, and can be appropriately changed without departing from the scope of the present invention. Further, in the drawings shown below, the scale of each member may be different from the actual one for easy understanding. The same applies to each drawing.

Embodiment 1
FIG. 1: is a figure which shows the surface which is a light-receiving surface of the photovoltaic cell 10 provided with the electrode formed of the electrode formation method of the photovoltaic cell concerning Embodiment 1 of this invention. The surface that is the light receiving surface is called the first main surface. FIG. 2: is a figure which shows the back surface on the opposite side to a light-receiving surface about the photovoltaic cell 10 shown in FIG. The back surface is called the second main surface. 3 is a V-V cross-sectional view of FIGS. 1 and 2, and FIG. 4 is a W-W cross-sectional view of FIGS. 1 and 2.

  A light receiving surface electrode 34 as a first current collection electrode, which is formed of a light receiving surface grid electrode 32 and a light receiving surface bus electrode 33, is provided on the light receiving surface 31 which is the first main surface of the solar battery cell 10. The light receiving surface grid electrode 32 and the light receiving surface bus electrode 33 are orthogonal to each other. Further, on the back surface 41 which is the second main surface of the solar battery cell 10, a back surface electrode 44 as a second current collection electrode including the back surface aluminum electrode 42 and the back surface bus electrode 43 is provided. The first direction which is the horizontal direction indicated by the arrow X in FIG. 1 and FIG. 2 is the longitudinal direction of the light receiving surface bus electrode 33, and the second direction which is the vertical direction indicated by the arrow Y in FIG. It is the longitudinal direction of the surface grid electrode 32. The direction perpendicular to the light receiving surface 31 is taken as the Z direction.

  FIG. 3: is principal part sectional drawing of the photovoltaic cell 10 concerning Embodiment 1 of this invention, and is VV sectional drawing in FIG. 1 and FIG. FIG. 3 is a view showing a cross section in which the light receiving surface bus electrode 33 exists. In the drawing, the upper side is the light receiving surface 31. FIG. 4: is principal part sectional drawing of the photovoltaic cell 10 concerning Embodiment 1 of this invention, and is WW sectional drawing in FIG. 1 and FIG. FIG. 4 is a view showing a cross section in which the light receiving surface bus electrode 33 does not exist. In the drawing, the upper side is the light receiving surface 31. FIG. 5 is an enlarged perspective view of an essential part of the light receiving surface electrode 34 according to the first embodiment of the present invention.

  The solar battery cell 10 has an n-type impurity diffusion layer 2 formed by phosphorus diffusion on the upper surface of a p-type single crystal silicon substrate 1 having a texture structure, and a photoelectric conversion portion is formed by a pn junction. An antireflection film 3 is formed on the light receiving surface side of the n-type impurity diffusion layer 2. A light receiving surface bus electrode 33 and a light receiving surface grid electrode 32 are provided on the antireflective film 3. The reflection preventing film 3 under the light receiving surface bus electrode 33 and the light receiving surface grid electrode 32 is melted by firing, and the light receiving surface bus electrode 33 and the light receiving surface grid electrode 32 are electrically joined to the n-type impurity diffusion layer 2 . In the solar battery cell 10, a pn junction may be formed by an n-type single crystal silicon substrate and a p-type impurity diffusion layer on the upper surface thereof.

  The light receiving surface electrode 34 provided on the light receiving surface 31 (first main surface) side of the p-type single crystal silicon substrate 1 extends in the X direction, which is the first direction, and a plurality of light receiving surface buses formed in parallel in the Y direction. An electrode 33 and a plurality of light receiving surface grid electrodes 32 extending in the Y direction which is a second direction orthogonal to the light receiving surface bus electrode 33 and formed in parallel to the X direction are provided. The light receiving surface bus electrode 33 has a low bus portion 35 whose height in a direction perpendicular to the light receiving surface 31 is lower than the height of the light receiving surface grid electrode 32, and a height in a direction perpendicular to the light receiving surface 31 is low. A high bus portion 36 which is higher than the height of the bus portion 35 is provided. A plurality of high bus portions 36 are provided in the X direction. The plurality of light receiving surface bus electrodes 33 are provided with high bus portions 36 at the same position in the X direction.

  A back surface electrode 44 provided on the back surface 41 (second main surface) side of the p-type single crystal silicon substrate 1 includes a back surface aluminum electrode 42 and a back surface bus electrode 43. The back surface bus electrodes 43 are provided in a dotted manner at positions corresponding to the light receiving surface bus electrodes 33. The position of the back surface bus electrode 43 in the Y direction is provided at the position where the center of the back surface bus electrode 43 in the Y direction is transparent to the light receiving surface bus electrode 33 through the Z direction perpendicular to the light receiving surface 31. The position of the back surface bus electrode 43 in the X direction is the position where the center of the back surface bus electrode 43 in the X direction is transparent to the light receiving surface 31 in the Z direction, which is perpendicular to the light receiving surface 31. Provided in

  The back surface aluminum electrode 42 is provided in the entire area other than the back surface bus electrode 43 of the back surface 41 so as to contact the back surface bus electrode 43 with, for example, an overlapping width of 0.1 mm to 0.9 mm.

  FIG. 3 shows a cross section along the longitudinal direction of the light receiving surface bus electrode 33, and the light receiving surface grid electrode 32 is not shown. On the other hand, FIG. 4 shows a cross section at the Y direction position where the light receiving surface bus electrode 33 is not provided, and the light receiving surface bus electrode 33 and the back surface bus electrode 43 are not shown.

  The solar battery cell 10 has, for example, a thickness of 200 μm, a width in the X direction of 156 mm, and a width in the Y direction of 156 mm. Four sets of light receiving surface bus electrodes 33 and back surface bus electrodes 43 are provided on the front and back surfaces of the solar battery cell 10 at an equal pitch of 39 mm. The light receiving surface bus electrodes 33 are, for example, 1 mm wide by 155 mm long, and four light receiving surface bus electrodes 33 are provided at regular intervals of 39 mm. The light receiving surface grid electrodes 32 have, for example, a width of 30 μm to 100 μm, a length of 154 mm, and a height of 10 to 20 μm, at equal intervals with the Y direction orthogonal to the X direction which is the longitudinal direction of the light receiving surface bus electrode 33 155 to 78 are provided at a pitch of 1 to 2 mm. A plurality of high bus portions 36 of the light receiving surface grid electrode 32 are provided at equal intervals with a length of 6 mm in the X direction.

  The back surface bus electrodes 43 have a width of 3 mm in the Y direction and a length 6 mm in the X direction, for example, 4 rows, 6 to 10, at positions corresponding to the light receiving surface bus electrodes 33 It is evenly provided at a pitch of 15 mm.

  A plurality of solar battery cells 10 are arranged side by side, and the light receiving surface bus electrode 33 of the solar battery cell 10 and the back surface bus electrode 43 of the adjacent solar battery cells 10 are electrically connected by the tab wire 20 Is formed. The tab wire 20 is formed by coating solder around the copper wire.

  FIG. 6 shows a cross-sectional view of the light receiving surface bus electrode 33 formed in the first embodiment. When the light receiving surface bus electrode 33 is applied by the method of the present embodiment, it is possible to form the light receiving surface bus electrode 33 with a very thin electrode thickness by reducing the applied amount, but the electrode is joined to the tab wire 20 In such a case, the mechanical strength of the joint becomes extremely low even if the joint can not be well soldered or joined.

  Therefore, as shown in FIG. 6, in the X direction which is the longitudinal direction of the light receiving surface bus electrode 33, the high bus portion 36 whose height in the direction perpendicular to the light receiving surface 31 is higher than the height of the low bus portion 35 is By providing and joining the tab wire 20 with the solder at the high bus portion 36, it is possible to obtain a solder joint with high mechanical strength of the joint. In FIG. 6, L1 is the length of the high bus portion 36 in the X direction, L2 is the length in the X direction at the center of the low bus portion 35, and L3 is the length in the X direction at the end of the low bus portion 35. It is. For example, L1 is provided at 8 mm in 6 mm, L2 at 12 mm in 7 places, and L3 at 11 mm in two positions at both ends.

  The height of the high bus portion 36 of the light receiving surface bus electrode 33 is desirably about the same as the height of the light receiving surface grid electrode 32. When the light receiving surface bus electrode 33 is formed after the light receiving surface grid electrode 32 is formed, even if the light receiving surface bus electrode 33 is formed higher than the light receiving surface grid electrode 32, it spreads in the Y direction at the time of paste application. It is difficult to form the light receiving surface bus electrode 33 whose height is higher than that of the grid electrode 32. On the other hand, when the height is lowered, bonding with the tab wire 20 becomes difficult. Therefore, by setting the height of the high bus portion 36 of the light receiving surface bus electrode 33 to the same level as the height of the light receiving surface grid electrode 32, electrode formation is easy and bonding with the tab wire 20 is facilitated. it can.

  The height of the low bus portion 35 of the light receiving surface bus electrode 33 is preferably higher than the height of the texture of the light receiving surface 31. The current collected by the light receiving surface grid electrode 32 connected to the low bus portion 35 flows from the low bus portion 35 to the high bus portion 36, and adjacent solar cells are formed by the tab wires 20 joined by the high bus portion 36. It flows to the cell. Therefore, when the electrical resistance of the low bus portion 35 increases, the resistance loss increases, and the output characteristics of the solar battery cell deteriorate. In particular, when the texture is formed on the light receiving surface 31, the electrical resistance tends to increase due to the unevenness of the texture. A light receiving surface bus electrode having a small electric resistance even if the surface has unevenness of texture by making the height of the low bus portion 35 of the light receiving surface bus electrode 33 higher than the height of the texture of the light receiving surface 31 33 can be obtained. The texture has a quadrangular pyramidal shape, and the size is, for example, about 3 μm per side of a square of the bottom and about 2 μm in height.

  If the height of the low bus portion 35 of the light receiving surface bus electrode 33 is increased, the amount of electrode paste used increases and the cost is increased. Therefore, it is desirable to lower the height within a range that does not significantly affect the electrical resistance. . Therefore, the height of the low bus portion 35 of the light receiving surface bus electrode 33 is desirably about 1/3 to 2/3 of the height of the light receiving surface grid electrode 32. It is most desirable to be about 1/2.

  Further, by providing a difference between the height of the high bus portion 36 of the light receiving surface bus electrode 33 and the height of the low bus portion 35, the thermal capacity of the high bus portion 36 is increased, and the tab wire 20 in the high bus portion 36 Bond strength can be increased. The height of the high bus portion 36 of the light receiving surface bus electrode 33 and the height of the low bus portion 35 preferably have a height difference of 5 μm or more.

  The length in the X direction of the high bus portion 36 of the light receiving surface bus electrode 33 increases cost as the length increases, while the peel strength decreases as the length decreases, so an appropriate length considering both of them It is desirable to choose The length of the high bus portion 36 in the X direction is preferably shorter than the length of the low bus portion 35 in the X direction. On the other hand, by setting the high bus portion 36 in at least one of the grids, it is possible to suppress a decrease in peel strength. For that purpose, it is desirable that the length of the high bus portion 36 in the X direction be twice or more the grid pitch. If the grid pitch is 1 mm, the length of the high bus portion 36 in the X direction is preferably 2 mm or more.

  The number of high bus portions 36 of the light receiving surface bus electrode 33 in the X direction increases the cost as the number increases, while the peel strength decreases as the number decreases, so an appropriate number is selected in consideration of both. Is desirable. Therefore, the number of high bus portions 36 in the X direction is preferably 6 to 10.

  The back surface bus electrodes 43 are provided in a dotted manner at positions corresponding to the high bus portions 36 of the light receiving surface bus electrodes 33. At the time of solder bonding between the solar battery cell 10 and the tab wire 20, the tab wire 20 on the back surface side, the solar battery cell 10, and the tab wire 20 on the light receiving surface side are laminated in order, and the tab wire on the light receiving surface side A junction is formed by heating with a lamp heater in a state where the upper portion 20 is pressed from above and in close contact with each other. Therefore, by providing the high bus portion 36 and the rear surface bus electrode 43 at corresponding positions, the tab bonding position is the same on the light receiving surface side and the rear surface side, and the tab wire 20 on the light receiving surface side is pressed from above At the same time, since the light receiving surface side and the back surface side can be brought into close contact with each other simultaneously, the solar battery cell 10 and the tab wire 20 can be easily joined.

  Next, the process for manufacturing the photovoltaic cell 10 shown to FIGS. 1-4 is demonstrated. The present embodiment is characterized in that the step of forming the light receiving surface bus electrode includes the step of applying a paste containing a conductive material which is an electrode material to the electrode forming surface of the substrate material without using a printing mask. In the coating process, a paste is applied using a liquid discharge device while controlling the coating amount per time.

  First, the p-type single crystal silicon substrate 1 is immersed in an aqueous solution of sodium hydroxide heated to about 90.degree. Thereby, the surface of the p-type single crystal silicon substrate 1 is etched, and a texture having a minute uneven structure is formed on the surface layer of the p-type single crystal silicon substrate 1. The texture has a quadrangular pyramidal shape, and the size is, for example, about 3 μm per side of a square of the bottom and about 2 μm in height. The surface of the p-type single crystal silicon substrate 1 is a (100) surface, and each surface of the quadrangular pyramid is a (111) surface.

  Next, the p-type single crystal silicon substrate 1 is put into a thermal oxidation furnace, and heated to about 800 ° C. to 900 ° C. in the presence of phosphorus oxychloride (POCl 3) vapor. Thus, phosphorus glass is formed on the surface of p-type single crystal silicon substrate 1 and phosphorus is diffused in p-type single crystal silicon substrate 1, and n-type impurity diffusion layer 2 is formed on the surface of 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 aqueous solution, a silicon nitride film (SiN film) is formed on the n-type impurity diffusion layer 2 as the antireflective film 3 by plasma CVD, for example. Form. The film thickness and the refractive index of the antireflective film 3 are set to values that most suppress light reflection. Note that films of two or more layers having different refractive indexes may be stacked. Further, the antireflective film 3 may be formed by a different film forming method such as a sputtering method.

  Next, a paste containing silver is printed by screen printing on the back surface 41 of the p-type single crystal silicon substrate 1 in the area where the back bus electrode 43 is to be formed, and a paste containing aluminum over the entire area other than the back bus electrode 43 Is printed on the entire surface by screen printing.

  Further, a paste containing silver is printed by screen printing on the light receiving surface 31 of the p-type single crystal silicon substrate 1 to form the light receiving surface grid electrode 32, and then using a coating apparatus shown in FIG. 7 and FIG. A light receiving surface bus electrode 33 is applied. After the light receiving surface bus electrode 33 is applied, a baking process is performed to form the light receiving surface electrode 34 and the back surface electrode 44. In the light receiving surface 31 of the p-type single crystal silicon substrate 1, the anti-reflection film 3 under the light receiving surface electrode 34 is melted by firing, and the light receiving surface electrode 34 electrically contacts the n type impurity diffusion layer 2. As described above, the solar battery cell 10 shown in FIGS. 1 to 4 is manufactured.

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

  Next, a method of forming the light receiving surface bus electrode in the method of forming an electrode of the solar battery cell according to the present embodiment will be described. FIG. 7 is a schematic view illustrating a printing machine used in the electrode forming method of the present embodiment, which is used in a printing process for forming an electrode without a printing mask. In this printing step, the paste 51 for the light receiving surface bus electrode 33 is applied to the electrode forming surface of the substrate material without passing through the printing mask.

  As a material of a substrate on which an electrode is formed by the method of the present embodiment, for example, a silicon wafer which is thin silicon is used. As the shape of the substrate, for example, a square shape or a square quadrilateral shape in which four corners of the square are arc-shaped is used. One side of the square shape and the side equivalent width of the rounded square shape are, for example, 156 mm. In addition, as long as a substrate material is a material which can form an electrode by a usual screen printing process, it is possible to use whichever material it is, and a substrate material used in a usual method There is no difference with it.

  As shown in FIG. 7, the printing machine according to the present embodiment includes a print head 101 having a liquid discharge portion 102 for discharging a paste 51 constituting an electrode material, and a pn junction which is a substrate material, that is, a solar cell substrate. And a stage 104 for mounting the formed p-type single crystal silicon substrate 1 thereon. A discharge nozzle 103 is provided at the tip of the liquid discharge unit 102, and the paste 51 adjusted to a desired viscosity is discharged from the discharge nozzle 103. The discharge amount per unit time of the paste 51 can be changed by a signal from the control unit 105. The stage 104 is an XY table movable in the X direction and the Y direction, and coordinates can be designated by a signal from the control unit 105 and can be moved continuously. The moving speed of the XY table can also be changed by a signal from the control unit 105. The printing press also includes a print head 101 for disposing the liquid discharger 102 above the stage 104. The print head 101 can also be moved in the Y direction and the Z direction by a signal from the control unit 105.

  The printing machine is a stage on which the liquid discharge unit 102 and the solar cell substrate 1S are placed while applying pressure to the liquid discharge unit 102 filled with the paste 51 disposed on the print head 101 according to a preprogrammed printing pattern. By moving 104, the paste 51 is applied to the electrode formation surface of the solar cell substrate 1S. Here, the solar cell substrate 1S refers to a p-type single crystal silicon substrate 1 on which a pn junction is formed and an antireflective film 3 is formed.

  The application process of applying the paste will be described in detail. FIG. 10 shows a flowchart of the coating process.

  First, a substrate mounting step S1 is performed in which the solar cell substrate 1S is mounted on the stage 104 with the light receiving surface bus electrode 33 in the longitudinal direction as the X direction.

  Next, the X direction (first direction) control step S2 of moving the liquid discharge unit 102 to the paste application start position which is the end of the light receiving surface bus electrode 33 by moving the stage 104 and the liquid discharge unit 102 is performed. Do.

  Next, a discharge nozzle lowering step S3 is performed in which the liquid discharge portion 102 is lowered in the Z direction to set the gap between the solar cell substrate 1S and the lower end of the discharge nozzle 103 to a suitable position for paste application. It is appropriate that the height of the lower end of the discharge nozzle 103 of the liquid discharge unit 102 be the same position as the height of the upper end of the light receiving surface grid electrode 32. If the height is low, the light receiving surface grid electrode 32 is scraped by the lower end of the discharge nozzle 103, which is inappropriate. On the other hand, if the distance between the solar cell substrate 1S and the lower end of the discharge nozzle 103 becomes large, the positional accuracy of the paste application decreases, which is inappropriate. Therefore, it is most appropriate to set the height of the lower end of the discharge nozzle 103 to the same position as the height of the upper end of the light receiving surface grid electrode 32.

  Next, a paste discharge step S4 of discharging the paste 51 onto the solar cell substrate 1S by moving the stage 104 in the X direction while applying pressure to the liquid discharge portion 102 and forming the light receiving surface grid electrode 32 is performed. . Here, at the position corresponding to the low bus portion 35 in the X direction, the height of the low bus portion 35 is reduced by lowering the pressure applied to the liquid discharge portion 102 as compared with the position corresponding to the high bus portion 36. Can be lower than the height of the high bus portion 36.

  That is, the discharge amount per time from the discharge nozzle 103 at the first position in the second direction which is the low bus portion 35 is set as the first discharge amount, and the discharge at the second position in the second direction which is the high bus portion 36. By setting the discharge amount per hour from the nozzle 103 to a second discharge amount larger than the first discharge amount, the height of the low bus portion 35 can be made lower than the height of the high bus portion 36.

  In addition, at the position corresponding to the low bus portion 35 in the X direction, the height of the low bus portion 35 can be increased by increasing the moving speed of the stage 104 compared to the position corresponding to the high bus portion 36. It may be lower than the height of 36. Further, both of the pressure applied to the liquid ejection unit 102 and the moving speed of the stage 104 may be controlled.

  That is, the moving speed of the stage 104 at the first position in the second direction which is the low bus portion 35 is taken as the first stage moving speed, and the moving speed of the stage 104 at the second position in the second direction which is the high bus portion 36 The height of the low bus section 35 can be made lower than the height of the high bus section 36 by setting the second stage moving speed lower than the first stage moving speed.

  Next, the liquid discharger 102 is raised in the Z direction, and a discharge nozzle lifting step S5 is performed in which the gap between the solar cell substrate 1S and the liquid discharger 102 is at a height position where both do not interfere.

  Next, an application completion determination step S6 is performed to determine whether the paste application has been completed. The paste application is completed by repeating the paste discharge for the number of light receiving surface bus electrodes 33.

  When the paste application is not completed, that is, in the case of No in the application completion determination step S6, the stage 104 and the liquid discharge unit 102 are moved in the Y direction to become the end of the adjacent light receiving surface bus electrode 33 An X direction (first direction) control step S2 of moving the liquid discharge unit 102 to the paste application start position is performed. Since the ends of the plurality of light receiving surface bus electrodes 33 are at the same position in the X direction, they can be moved to the end portions of the adjacent light receiving surface bus electrodes 33 only by moving in the Y direction.

  By repeating the paste discharging process as many times as the number of the light receiving surface bus electrodes 33 in this manner, the paste application to the light receiving surface bus electrode 33 is completed. After the completion of the paste application, a substrate removal step S7 for removing the solar cell substrate 1S coated with the paste from the stage 104 is performed.

  The coating process is completed by the substrate placement process, the first direction control process, the discharge nozzle lowering process, the paste discharge process, the discharge nozzle raising process, the application completion determination process, and the substrate removal process.

  FIG. 8 is a schematic cross-sectional view in which the stage portion of the printing press is enlarged. Here, the case where the light receiving surface bus electrode 33 is formed on the solar cell substrate 1S is taken as an example. When the present embodiment is applied to the formation of the light receiving surface bus electrode 33, the light receiving surface grid electrode 32 is formed in advance. When forming the light receiving surface grid electrode 32, it may be formed by the screen printing method which is a usual method conventionally used, or the electrode forming method of the present embodiment may be used. Alternatively, the light receiving surface grid electrode 32 may be formed after the light receiving surface bus electrode 33 is formed.

  In FIG. 8, the solar cell substrate 1S 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 position along the light receiving surface bus electrode 33 of the solar battery cell 10. The liquid discharge unit 102 disposed in the print head 101 is filled with the paste 51, and pressure is applied to the liquid discharge unit 102 to eject the paste 51 from the discharge nozzle 103 provided at the tip of the liquid discharge unit 102. Thus, the pattern of the light receiving surface bus electrode 33 programmed in advance is drawn on the light receiving surface 31 which is the electrode forming surface of the solar cell substrate 1S.

  The liquid discharge unit 102 can control the application amount per time by the control unit 105 of the printing press. Further, the pressure sensed by the pressure sensor 109 provided on the stage 104 is fed back to the liquid discharge unit 102 through the control unit 105, and the application amount can be controlled.

  The discharge nozzle 103 mounted on the liquid discharge unit 102 uses a material, a size, and a shape 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 also selected from ordinary round, square, branch nozzles, multiple nozzles, flat nozzles and the like.

  According to this embodiment, the light receiving surface grid electrode 32 is formed in advance by the screen printing method, and the solar cell substrate 1S subjected to the drying process is mounted on the stage 104 and fixed by the suction unit 108. Next, the light receiving surface bus electrode 33 is drawn on the light receiving surface 31 of the solar cell substrate 1S so as to be orthogonal to the light receiving surface grid electrode 32, in accordance with a preprogrammed printing pattern. In the present embodiment, the width of the light receiving surface bus electrode 33 is 1 mm, and the light receiving surface grid electrode 32 is formed in advance, so that the applied nozzle has a diameter of 0.8 .phi. Thus, the light receiving surface bus electrode 33 can be formed by supplying the paste 51 directly from the discharge nozzle 103 without using a print mask.

  FIG. 9 is a schematic cross-sectional view of a portion where the light receiving surface bus electrode 33 is drawn and the periphery thereof in the printing machine of the first embodiment. The paste 51 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 33 is drawn. At this time, by controlling the pressure of the liquid discharge unit 102 in accordance with the position to be drawn, it becomes possible to draw while changing the discharge amount finely.

  FIG. 11 is a schematic cross-sectional view of a stage portion of the screen printing machine used to form the light receiving surface grid electrode 32 in the present embodiment. In the screen printing step, the paste 52 for the light receiving surface grid electrode 32 is applied to the electrode forming surface of the solar cell substrate 1S via the printing mask 202. FIG. 12 is an enlarged view of FIG. The printing machine shown in FIGS. 11 and 12 includes a stage 104 on which the solar cell substrate 1S is mounted, 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 1S to the stage 104 by suction of air on the stage 104. The print mask 202 has a mask frame 203, warp yarns 200A, and weft yarns 200B, and includes a screen mesh 200 attached to the print surface side of the mask frame 203, and a photosensitive emulsion 200S. In FIG. 12, the stage 104 and the mask frame 203 are omitted.

  The printing machine applies the paste 52 to the electrode formation surface of the solar cell substrate 1S via the printing mask 202 by scanning the squeegee 201 on the printing mask 202 in a state in which the paste 52 is loaded. A portion of the printing mask 202 covered with the photosensitive emulsion 200S does not pass the paste 52, but passes the paste 52 at the portion where the screen mesh 200 is exposed. The image is transferred onto the electrode formation surface to form a light receiving surface grid electrode 32.

  Pastes 51 and 52 contain a conductive material which is an electrode material. Typical conductive materials used for pastes 51 and 52 include metal materials such as gold, silver, copper, platinum and palladium. Pastes 51 and 52 contain one or more of these conductive materials.

  In the electrode formation method of the first embodiment, it is possible to select pastes 51 and 52 optimum for light receiving surface grid electrode 32 and light receiving surface bus electrode 33. Further, in the present embodiment, it is also possible to reduce the coating amount required for the light receiving surface bus electrode 33. Incidentally, in the usual method, the batch formation is performed on the light receiving surface grid electrode 32 and the light receiving surface bus electrode 33, so the weight of the paste applied to the light receiving surface bus electrode 33 through the printing mask 202 is equal to the light receiving surface grid. It is decided by the mask specification for expressing the performance of the electrode 32. On the other hand, in the present embodiment, optimization can be achieved by forming each independently.

  Moreover, in the specification of the paste most suitable for the light receiving surface bus electrode 33, 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 32 because of the required performance. is there. That is, this is nothing but lowering the total price of the pastes 52 and 51. Therefore, by forming the light receiving surface grid electrode 32 and the light receiving surface bus electrode 33 independently of each other, cost reduction can be achieved from both sides in terms of coating amount and cost.

  On the other hand, in the comparative example, in order to form the light receiving surface grid electrode 32 and the light receiving surface bus electrode 33 generally collectively, the specifications of the printing mask 202 and the paste are uniformly set. However, the performance required for the light receiving surface grid electrode 32 and the light receiving surface bus electrode 33 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. Therefore, it is an excess quality to use the paste adjusted to express the performance of the light receiving surface grid electrode 32 to the maximum for the light receiving surface bus electrode 33, and the expensive one is also used in price.

FIG. 13 is a table comparing the performance of the solar battery produced by the method of the comparative example with the performance of the solar battery of the first embodiment. Compared with the method of the comparative example, the voltage (Voc) is improved by ² mV, the current (Jsc) is improved by 0.4 mA / cm ^2, and the curve factor (FF) is reduced by 1/100, so that the efficiency (Eff) becomes equivalent. .

  In addition, when the light receiving surface bus electrode 33 is formed without considering the thickness of the bonding portion in bonding strength, the strength of the conventional method can not be exceeded, but in the first embodiment, the thickness of the bonding portion is considered. As a result of changing to the above structure, a value equal to or higher than that of the comparative example was secured.

  FIG. 14 is a comparison diagram comparing the weight of the paste applied to the light receiving surface bus electrode 33 of the solar battery cell produced by the method of the comparative example with the applied weight of the first embodiment. The paste 51 for the light receiving surface bus electrode 33 used in the present embodiment has 30% of the amount of the conductive material contained therein compared to the amount of the conductive material contained in the paste for the light receiving surface bus electrode 33 of the comparative example. The degree is reduced.

  In the first embodiment, by changing the pressure applied to the liquid discharge portion 102 between the low bus portion 35 and the high bus portion 36, the flow rate of the paste to be discharged can be changed to change the height of the electrode. .

  Although the coating amount of 0.05 g in the method of the comparative example is 0.034 g in the method of the present embodiment, the coating amount can be reduced by about 30% as compared with the method of the comparative example. The performance of the solar battery cell produced by this becomes a result equivalent to the method of the comparative example, and is reduced by 30% from the application amount of the paste in the method of the comparative example, and this is a paste obtained by reducing the conductive material by 30%. 51 is achieved.

  FIG. 15 shows the relative values of the manufacturing costs 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 33, and the conventional method is applied to the light receiving surface grid electrode 32, the cost is reduced for paste, and the printing mask is changed. None, the cost of printing presses will increase. However, under certain conditions, the output cost of the solar cell and the cost and usage of the paste are reduced, and even if the printer according to the present embodiment is additionally introduced, the introduction cost is recovered in about one year, After that, it will make a profit. In addition, in FIG. 15, the light receiving surface bus electrode paste is a light receiving surface bus paste, and the light receiving surface bus electrode printing machine is a light receiving surface bus printing machine.

  FIG. 16 and FIG. 17 are schematic cross-sectional views for explaining the procedure of the method of manufacturing a solar cell module according to the present embodiment. First, the plurality of solar battery cells 10 in which the current collecting electrodes are formed on the light receiving surface side and the back surface side are connected by the tab wire 20. A state in which the solar battery cell 10 with the wiring is sandwiched between the light transmitting substrate 22 and the back surface sheet 23 via the light transmitting resin members 21A and 21B as shown in FIG. As shown in FIG. 17, the translucent resin member 21 in which the solar cells 10 with wiring are sealed, the translucent substrate 22, and the back surface sheet 23 are integrated by performing the heat treatment at The solar cell module is manufactured. By using the solar battery cell 10 provided with the electrode formed by the above electrode formation method, a solar battery module having high power generation efficiency can be obtained.

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

  According to the first embodiment, when the light receiving surface bus electrode 33 is formed, the cost for the printing mask becomes unnecessary by not using the printing mask. Also, the desired electrode can be formed by a system that is less expensive than a screen printer. In the electrode formation, since the paste can be applied while controlling the application amount per time, it is possible to discharge the originally necessary amount of paste to the electrode formation position. As a result, it is possible to supply sufficient paste necessary to improve the characteristics, and as a result, reduce the amount of paste supplied as compared with the prior art, that is, to form a solar cell electrode having both cost reduction and efficiency improvement. I assume. In addition, the electrode forming method according to the first embodiment is a simple and inexpensive method, and the design change in the arrangement, the line width, the thickness, and the like of the electrode pattern can be made by replacing the conventional method or adding to the conventional method. If there is, it can be implemented immediately and reliable electrode formation is easily possible.

  The light receiving surface grid electrode 32 was formed by screen printing, and only the light receiving surface bus electrode 33 was formed while controlling the discharge amount using the liquid discharge unit 102 without using the screen. Alternatively, the liquid discharge unit 102 may be used to control the discharge amount.

  Further, by controlling the discharge amount of the liquid discharge unit 102 and controlling the moving speed of the stage 104, it becomes easy to control the height of the light receiving surface bus electrode 33.

  Note that the control unit 105 efficiently draws the bus electrode while maintaining the line width and position with high accuracy by controlling the supply amount of the paste from the discharge nozzle 103 to 0.1 ml to 1 ml per minute. can do. In particular, the drawing amount of the paste from the discharge nozzle 103 is desirably controlled within the range of 0.1 ml to 0.3 ml per minute while drawing the bath electrode, thereby achieving high accuracy without using the pressure sensor 109. Bus electrode formation is realized. In the case of performing paste supply without using the pressure sensor 109, it becomes possible to draw a highly accurate bus electrode pattern by controlling the supply amount with high precision at 0.1 ml to 1 ml per minute. . In particular, by drawing the pattern of the bath electrode while controlling the supply amount of paste from the discharge nozzle 103, that is, the discharge amount, at 0.1 ml to 0.3 ml per minute, the supply amount of the conventional application amount is reduced by 30%. The pattern of the bus electrode can be drawn. Therefore, it is possible to provide an electrode with high accuracy and a small amount of used paste. Incidentally, under certain conditions, the application amount of 0.012 g corresponds to the application at about 0.1 ml / min, and the application amount of 0.034 g corresponds to the application at about 0.3 ml / min. Furthermore, as described above, the discharge amount can also be finely adjusted by adjusting the height of the discharge nozzle 103. In addition, even when using the pressure sensor 109, more accurate control is performed by drawing the pattern of the bus electrode while controlling the discharge amount of the paste from the discharge nozzle 103 at 0.1 ml to 0.3 ml per minute. Is possible.

  The method for forming a solar cell electrode according to the present invention includes the step of applying a paste containing a conductive material which is an electrode material to the electrode formation surface of a substrate material without using a printing mask. The liquid discharge device is moved by a drawing program for obtaining a desired electrode shape while controlling the amount of application with time, and the paste is applied.

  According to the present invention, by not using a print mask, the cost therefor is not necessary. Also, the desired electrode can be formed by a system that is less expensive than a screen printer. In the electrode formation, since the paste can be applied while controlling the application amount per time, it is possible to discharge the originally necessary amount of paste to the electrode formation position. As a result, it is possible to supply a sufficient amount of paste necessary to improve the characteristics, and as a result, to reduce the amount of paste to be supplied compared to the conventional method, and to form a solar cell electrode having both cost reduction and efficiency improvement.

  In addition, in manufacturing a solar cell module, when bonding a tab wire for inter-substrate connection to a solar battery cell, drawing for obtaining a desired electrode shape is possible in order to enable solder tab attachment with certainty at the bonding point. Since the liquid discharge apparatus can be moved in three dimensions by the program, a sufficient electrode thickness is secured at the bonding point, and there are no unevenness, unevenness, and blurring of the electrode thickness, and a sufficient value is obtained for the bonding strength. It becomes possible.

  The electrode forming method of the present invention is a simple and inexpensive system, and can be implemented by replacing the conventional method or adding to the conventional method.

  In the comparative example, in order to form the light receiving surface grid electrode 32 and the light receiving surface bus electrode 33 in a batch, the specifications of the printing mask and the paste 51 are set uniformly. However, the performances required for the light receiving surface grid electrode 32 and the light receiving surface bus electrode 33 are not the same. The former is to collect the current generated in the p-type single crystal silicon substrate 1, and the latter is to flow the collected current through the tab line. Therefore, using the paste 51, which is adjusted so as to maximize the performance of the light receiving surface grid electrode 32, for the light receiving surface bus electrode 33 is an excessive quality, and a cost-effective one is used.

  On the other hand, in the electrode forming method of the present embodiment, it is possible to select pastes 51 and 52 optimum for light receiving surface grid electrode 32 and light receiving surface bus electrode 33. Further, in the present embodiment, it is also possible to reduce the coating amount required for the light receiving surface bus electrode 33. This is because, in the comparative example, the weight of the paste 51 applied to the light receiving surface bus electrode 33 through the printing mask is determined by the mask specification for exhibiting the performance of the light receiving surface grid electrode 32. In the embodiment, by forming the light receiving surface grid electrode 32 and the light receiving surface bus electrode 33 independently, optimization can be achieved.

  Moreover, in the specification of the paste 51 most suitable for the light receiving surface bus electrode 33, it is possible to express the function with a smaller amount of conductive material than the paste 52 of the light receiving surface grid electrode 32 because of the required performance. It is. That is, this is nothing but lowering the price of the paste 51. Therefore, by forming the light receiving surface grid electrode 32 and the light receiving surface bus electrode 33 independently of each other, cost reduction can be achieved from both sides in terms of coating amount and cost.

Second Embodiment
Next, a solar battery cell according to Embodiment 2 will be described. The solar battery cell of Embodiment 2 differs from the solar battery cell of Embodiment 1 only in the light receiving surface bus electrode shape and the back surface bus electrode shape. The other configuration is the same as the solar battery cell of the first embodiment. FIG. 18 is a cross-sectional view of main parts of a solar battery cell 310 according to a second embodiment of the present invention, which corresponds to a V-V cross-sectional view in FIG. 1 and FIG. FIG. 18 is a view showing a cross section in which the light receiving surface bus electrode 333 exists. In the figure, the upper side is a light receiving surface 331.

  The solar battery cell 310 has an n-type impurity diffusion layer 302 formed by phosphorus diffusion on the upper surface of a p-type single crystal silicon substrate 301 having a texture structure, and a photoelectric conversion portion is formed by a pn junction. An antireflective film 303 is formed on the light receiving surface side of the n-type impurity diffusion layer 302. A light receiving surface electrode 334 as a first current collecting electrode, which comprises a light receiving surface bus electrode 333 and a light receiving surface grid electrode 32, is provided on the anti-reflection film 303. The light receiving surface bus electrode 333 and the antireflection film 303 under the light receiving surface grid electrode 32 are melted by firing, and the light receiving surface bus electrode 333 and the light receiving surface grid electrode 32 are electrically joined to the n-type impurity diffusion layer 302 .

  FIG. 19 is a cross-sectional view of the light receiving surface bus electrode 333 of the solar battery cell 310 according to the second embodiment of the present invention. In FIG. 19, L6 is the length in the X direction of the high bus portion 336, L7 is the length in the X direction at the central portion of the low bus portion 335, and L8 is the length in the X direction at the middle end of the low bus portion 335. , L9 is the length in the X direction at the end of the low bus portion 335. For example, six places of L6 6 mm, five places of L7 17 mm, two places of L8 5 mm, and two places of L9 5.5 mm are provided.

  A back surface electrode 44 provided on the back surface 41 (second main surface) side of the p-type single crystal silicon substrate 301 includes a back surface aluminum electrode 342 and a back surface bus electrode 343. The back surface bus electrodes 343 are provided in a dotted manner at positions corresponding to the high bus portions 336 of the light receiving surface bus electrodes 333. At the time of solder bonding between the solar battery cell 310 and the tab wire 20, the tab wire 20 on the back surface side, the solar battery cell 310, and the tab wire 20 on the light receiving surface side are laminated in order, and the tab wire on the light receiving surface side A junction is formed by heating with a lamp heater in a state where the upper portion 20 is pressed from above and in close contact with each other. Therefore, by providing the high bus portion 336 and the back surface bus electrode 343 at corresponding positions, the tab bonding position is the same on the light receiving surface side and the back surface side, and the tab wire 20 on the light receiving surface side is pressed from above. At the same time, since the light receiving surface side and the back surface side can be brought into close contact with each other simultaneously, the solar battery cell 310 and the tab wire 20 can be easily joined.

  With such a configuration, in the light receiving surface bus electrode 333 of the second embodiment, the high bus portion 336 is disposed denser at the substrate end than at the central portion of the substrate and sparser at the central portion of the substrate than at the substrate end. be able to. In the solar battery cell 310, most of the area on the back surface side is covered with the back surface aluminum electrode 342, and the thermal expansion coefficient of aluminum is larger than that of silicon constituting the substrate. And convex toward the light receiving surface and concave toward the rear surface. Here, in the second embodiment, by arranging the high bus portions 336 at a substrate end portion more densely than the central portion of the substrate, the number of junctions between the high bus portions 336 and the tab wires 20 at places where the deformation is large is increased. Can increase the bonding strength.

  The configuration shown in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and one of the configurations is possible within the scope of the present invention. Parts can be omitted or changed.

  1 p-type single crystal silicon substrate, 1S solar cell substrate, 2 n-type impurity diffusion layer, 3 anti-reflection film, 10 solar cell, 20 tab lines, 21, 21A, 21B translucent resin member, 22 translucent Substrate, 23 back surface sheet, 31 light receiving surface, 32 light receiving surface grid electrode, 33 light receiving surface bus electrode, 34 light receiving surface electrode, 41 back surface, 42 back surface aluminum electrode, 43 back surface bus electrode, 44 back surface electrode, 51 paste, 52 paste, DESCRIPTION OF SYMBOLS 101 print head, 102 liquid discharge part, 103 discharge nozzle, 104 stage, 105 control part, 107 suction mechanism, 108 suction part, 109 pressure sensor, 203 mask frame, 200 screen mesh, 200S photosensitive emulsion, 201 squeegee, 200A warp , 200B weft, 202 printing mask, 301 p type single Crystal silicon substrate, 302 n-type impurity diffusion layer, 303 antireflective film, 310 solar battery cell, 331 light receiving surface, 333 light receiving surface bus electrode, 334 light receiving surface electrode, 342 rear surface aluminum electrode, 343 rear surface bus electrode.

In order to solve the problems described above and to achieve the object, the method of manufacturing a solar cell according to the present invention comprises the steps of: forming a pn junction on a semiconductor substrate to form a solar cell substrate; And a step of forming a bus electrode including a coating step of applying a paste containing a conductive material to the electrode formation surface of the solar cell substrate, and a firing step of firing the applied paste. The coating process includes a substrate mounting process for mounting the solar cell substrate on a position controllable stage, a first direction control process for controlling the position of the stage in the first direction, and a stage orthogonal to the first direction. The paste is applied to the electrode forming surface while controlling the application amount by the discharge amount per time from the discharge nozzle using a liquid application device having a discharge nozzle for discharging the paste while controlling the position in the second direction And a paste discharging step.

The height of the low bus portion 35 of the light receiving surface bus electrode 33 is preferably higher than the height of the texture of the light receiving surface 31. The current collected by the light receiving surface grid electrode 32 connected to the low bus portion 35 flows from the low bus portion 35 to the high bus portion 36, and adjacent solar cells are formed by the tab wires 20 joined by the high bus portion 36. It flows to the cell 10 . Therefore, when the electric resistance of the low bus portion 35 increases, the resistance loss increases, and the output characteristics of the solar battery cell 10 deteriorate. In particular, when the texture is formed on the light receiving surface 31, the electrical resistance tends to increase due to the unevenness of the texture. A light receiving surface bus electrode having a small electric resistance even if the surface has unevenness of texture by making the height of the low bus portion 35 of the light receiving surface bus electrode 33 higher than the height of the texture of the light receiving surface 31 33 can be obtained. The texture has a quadrangular pyramidal shape, and the size is, for example, about 3 μm per side of a square of the bottom and about 2 μm in height.

Next, the p-type single crystal silicon substrate 1 is put into a thermal oxidation furnace, and heated to about 800 ° C. to 900 ° C. in the presence of phosphorus oxychloride (POCl ₃ ) vapor. Thus, phosphorus glass is formed on the surface of p-type single crystal silicon substrate 1 and phosphorus is diffused in p-type single crystal silicon substrate 1, and n-type impurity diffusion layer 2 is formed on the surface of p-type single crystal silicon substrate 1. It is formed.

Claims (8)

Forming a pn junction on a semiconductor substrate to form a solar cell substrate;
A solar cell comprising: an applying step of applying a paste containing a conductive material which is an electrode material to an electrode forming surface of the solar battery cell substrate; and a firing step of firing the applied paste A method of manufacturing a cell,
The application process is
A substrate mounting step of mounting the solar cell substrate on a stage whose position can be controlled;
A first direction control step of controlling the position of the stage in the first direction;
The liquid application device having a discharge nozzle for discharging the paste is used to control the position of the stage in the second direction orthogonal to the first direction, and the discharge amount per hour is applied from the discharge nozzle And D. a paste discharging step of applying the paste to the electrode forming surface while controlling the amount thereof. In the paste discharge step,
The discharge amount per time from the discharge nozzle at the first position in the second direction is taken as a first discharge amount.
The solar cell according to claim 1, wherein the discharge amount per time from the discharge nozzle at the second position in the second direction is a second discharge amount larger than the first discharge amount. Manufacturing method. In the paste discharge step,
Let the moving speed of the stage at the first position in the second direction be the first stage moving speed,
The moving speed of the stage at the second position in the second direction is set to a second stage moving speed slower than the first stage moving speed. Production method. In the first direction control step,
The method of manufacturing a solar cell according to any one of claims 1 to 3, wherein the position of the discharge nozzle in the first direction is controlled. Before the paste discharge process,
The method of manufacturing a solar cell according to any one of claims 1 to 4, further comprising the step of applying a plurality of grid electrode pastes in parallel to the second direction. a substrate for a solar cell having a pn junction;
A first electrode formed on a first main surface of the solar cell substrate;
And a second electrode formed on a second main surface of the solar cell substrate, wherein the solar cell includes:
The first electrode is
A bus electrode formed extending in a first direction of the first main surface;
And a plurality of grid electrodes formed in parallel to a second direction intersecting the bus electrode,
The bus electrode is
A low bus portion whose height in the direction perpendicular to the first main surface is lower than the height of the grid electrode;
What is claimed is: 1. A solar cell comprising: a high bus portion having a height in a direction perpendicular to the first main surface that is higher than a height of the low bus portion.   The solar cell according to claim 6, wherein the height of the high bus portion is equal to the height of the grid electrode.   The height of the said low bus part is below 1/2 of the height of the said high bus part, The photovoltaic cell of Claim 6 or 7 characterized by the above-mentioned.