CN112352320A - Solar cell and method for manufacturing solar cell - Google Patents

Solar cell and method for manufacturing solar cell Download PDF

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Publication number
CN112352320A
CN112352320A CN201980042980.2A CN201980042980A CN112352320A CN 112352320 A CN112352320 A CN 112352320A CN 201980042980 A CN201980042980 A CN 201980042980A CN 112352320 A CN112352320 A CN 112352320A
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China
Prior art keywords
substrate
hole
solder
aluminum electrode
solar cell
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CN201980042980.2A
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Chinese (zh)
Inventor
新井杰也
菅原美爱子
小林贤一
小宫秀利
松井正五
锦织润
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Circular Special Ratio Co Ltd
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Circular Special Ratio Co Ltd
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Publication of CN112352320A publication Critical patent/CN112352320A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
    • H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
    • H01L23/492—Bases or plates or solder therefor
    • H01L23/4924—Bases or plates or solder therefor characterised by the materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/10—Bump connectors ; Manufacturing methods related thereto
    • H01L24/12—Structure, shape, material or disposition of the bump connectors prior to the connecting process
    • H01L24/14—Structure, shape, material or disposition of the bump connectors prior to the connecting process of a plurality of bump connectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/10—Bump connectors ; Manufacturing methods related thereto
    • H01L24/15—Structure, shape, material or disposition of the bump connectors after the connecting process
    • H01L24/17—Structure, shape, material or disposition of the bump connectors after the connecting process of a plurality of bump connectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
    • H01L24/81—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a bump connector
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/02002—Arrangements for conducting electric current to or from the device in operations
    • H01L31/02005—Arrangements for conducting electric current to or from the device in operations for device characterised by at least one potential jump barrier or surface barrier
    • H01L31/02008—Arrangements for conducting electric current to or from the device in operations for device characterised by at least one potential jump barrier or surface barrier for solar cells or solar cell modules
    • H01L31/0201—Arrangements for conducting electric current to or from the device in operations for device characterised by at least one potential jump barrier or surface barrier for solar cells or solar cell modules comprising specially adapted module bus-bar structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention relates to a solar cell and a method for manufacturing the solar cell, which aims to directly weld to a part of a hole of an aluminum electrode (2) on the back surface of a substrate (1) and weld in a mode of protruding more than 0.1mm above the aluminum electrode (2) so as to improve conversion efficiency and obtain enough fixing strength. The structure of the invention is as follows: after an aluminum electrode (2) is formed on the whole back surface of a substrate (1), a hole is formed in a part of the electrode, or an aluminum electrode (2) with a hole formed in a part of the whole back surface of the substrate (1) is formed, welding is carried out on the substrate (1) in the hole, welding is carried out in a mode of protruding from the edge of the hole to the upper side of the aluminum electrode (2) by more than 0.1mm, and electrons flow in from the part of the substrate (1) in the welded hole and the part of the aluminum electrode (2) protruding from the edge of the hole by more than 0.1mm, so that the conversion efficiency of the solar cell is improved.

Description

Solar cell and method for manufacturing solar cell
Technical Field
The present invention relates to a solar cell and a method for manufacturing a solar cell, the solar cell forming a region for generating a high electron concentration when light is irradiated onto a substrate, and forming an insulating film which transmits light on the region, and forming a finger electrode on the insulating film, the finger electrode being a take-out port for taking out electrons from the region, the solar cell taking out electrons to the outside through the finger electrode, and soldering a lead wire to a portion of a hole formed in an aluminum electrode on the back surface of the substrate, and performing soldering so as to protrude from an edge of the hole by 0.1mm or more above the upper side of the aluminum electrode, so as to increase conversion efficiency and improve fixing strength of the lead wire on the back surface.
Background
Conventionally, in the design of solar cells (solar cells), it has been important to efficiently flow electrons generated in a solar cell to a connected external circuit. In order to achieve this, it is particularly important to reduce the resistance component of the portion connected from the battery to the outside, prevent the loss of generated electrons, and strongly fix the external terminals on the front and back surfaces.
For example, as shown in the well-known technique of fig. 6, a nitride film 32 is formed on the front surface (upper surface) of a silicon substrate 31, and on this, a paste (containing lead-containing glass) of finger electrodes (silver) 33 is Screen-printed (Screen printing) and sintered, and holes are punched in the nitride film 32 as shown in the figure to form the finger electrodes 33 for extracting electrons from the high electron concentration region to the outside. Next, the bus bar electrode (silver) 34 was produced by screen printing in a direction orthogonal to the finger electrodes 33 and firing. A solder ribbon (lead) 35 is soldered to the bus bar electrode (silver) 34 with a solder 36, and the solder ribbon 35 is firmly fixed to the silicon substrate 31.
Further, an aluminum electrode 37 is formed on the back surface (lower surface) of the silicon substrate 31, and a solder ribbon 39 is soldered and fixed thereto.
In addition, if the aluminum electrode 37 is formed on the entire back surface and the solder ribbon 39 is weak in soldering strength, a hole is first punched in a portion of this aluminum electrode 37 (a portion corresponding to the bus bar electrode 34 on the front surface), and here silver paste is screen-printed and sintered to form a silver portion 371, and the solder ribbon 39 is fixed to this silver portion 371 with solder 38 to obtain necessary fixing strength.
Disclosure of Invention
[ problems to be solved by the invention ]
However, if the aluminum electrode is formed on the entire back surface of the silicon substrate 31 and the solder ribbon 39 is soldered thereto in the above-described conventional technique, there is a problem that the solder ribbon 39 cannot be fixed to the silicon substrate 31 with sufficient strength.
In addition, there are the following problems: in order to prevent this, as shown in fig. 6, a portion of the aluminum electrode 37 must be punched and coated with silver paste and sintered, and then a solder ribbon 39 must be soldered thereto to obtain sufficient fixing strength.
[ means for solving the problems ]
The present inventors have found through experiments that a configuration and a method in which a solder ribbon (also referred to as a "solder wire") is fixed to a substrate with sufficient fixing strength and high conversion efficiency is obtained by directly soldering onto a portion of a hole of an aluminum electrode on the back surface of the substrate and performing soldering in such a manner as to slightly protrude from the edge of the hole onto the aluminum electrode.
Accordingly, the present invention provides a solar cell in which a region where a high electron concentration is generated when light is irradiated onto a substrate is formed, an insulating film through which light can pass is formed on the region, and a finger electrode which is an extraction port for extracting electrons from the region is formed on the insulating film, wherein the solar cell extracts electrons to the outside through the finger electrode and allows the electrons to flow in from the back surface of the substrate to form a circuit, wherein an aluminum electrode is formed on the entire back surface of the substrate, and then a hole is formed in a part of the electrode or an aluminum electrode having a hole formed in a part of the entire back surface of the substrate, and soldering is performed on the substrate inside the hole, and soldering is performed so as to protrude from the edge of the hole to the upper side of the aluminum electrode by 0.1mm or more, and the electrons flow in from the part of the substrate inside the soldered hole and the part of the aluminum electrode protruding from the edge of the hole by 0.1mm or more, respectively, thereby increasing the conversion efficiency of the solar cell.
At this time, the hole-formed portion of the aluminum electrode is a portion corresponding to the front extraction line.
Further, the welding is ultrasonic welding.
Further, the welding is performed only on the solder, or on the solder and the extraction line, or on the extraction line that has been previously welded.
In addition, soldering is performed in a state where the temperature of a portion to be soldered is preheated to a temperature at which solder melts or lower and room temperature or higher.
The solder contains one or more of zinc, aluminum, and silicon in tin.
The solder does not contain Pb, Ag, or Cu.
Further, the structure is: the welding is performed so as to protrude from the edge of the hole by 0.1mm or more above the aluminum electrode, and the welding is performed so as to protrude from the edge of the hole by 0.1mm or more and 3.0mm or less above the aluminum electrode.
[ Effect of the invention ]
As described above, the present invention realizes a structure and a method of directly soldering to a portion of a hole of an aluminum electrode on the back surface of a substrate, and performing soldering in such a manner that the edge of the hole slightly protrudes above the aluminum electrode, while fixing a take-out wire to the substrate with sufficient fixing strength, and obtaining high conversion efficiency.
Accordingly, the present invention can be directly soldered to a portion of the hole of the aluminum electrode on the back surface of the substrate, reduce the resistance value of the portion of the extraction line, and fix the substrate with sufficient fixing strength.
In addition, it has been experimentally confirmed that, when soldering is performed so as to protrude 0.1mm or more above the aluminum electrode from the edge of the hole of the substrate, electrons can be supplied to the substrate from the protruding and soldered aluminum electrode and the aluminum electrode connected thereto, thereby improving the conversion efficiency of the solar cell (refer to fig. 4 and 5).
Detailed Description
[ example 1]
FIG. 1 shows a block diagram of embodiment 1 of the present invention.
Fig. 1 is a side view showing the whole; fig. 1 (b) is an enlarged view of a main portion showing fig. 1 (a).
In fig. 1, a substrate (silicon substrate) 1 is a silicon substrate (single crystal, polycrystalline) on which a solar cell is to be formed.
The substrate back surface (Al)2 is the back surface of the substrate 1, and an aluminum electrode is formed on the entire back surface and then a part of the back surface is punched, or an aluminum electrode having a hole is formed on the entire back surface of the substrate 1.
The substrate heater 3 is a heater for preheating the substrate 1, and is heated to a temperature below a temperature at which solder melts and above room temperature when being soldered to the substrate 1, and has an automatic temperature adjustment mechanism.
The ABS solder 11 is a long strip-shaped soldering material having a shape such as a wire or a ribbon shape that facilitates supply of solder for soldering to the substrate back surface (aluminum electrode) 2. The solder material is an alloy containing tin (Sn) and one or more of zinc (Zn), aluminum (Al), and silicon (Si), and is free of lead (Pb), silver (Ag), and copper (Cu) (referred to as ABS solder 11). The melting point of the ABS solder 11 depending on these solder materials is generally in the range of about 150 ℃ to 350 ℃, and because it is determined by the formulation ratio of the materials, the melting temperature is calculated by experiment, and the most preferable preheating temperature of the melting temperature (temperature above room temperature at which the ABS solder 11 does not melt) is determined, and in addition, an appropriate temperature to be melted and soldered on the substrate 1 inside the hole in the substrate back surface 2 when the soldering tip 22 is heated and ultrasonic wave is applied is determined by experiment. Accordingly, ultrasonic welding can be performed as shown in photographs of parts (a), (b), and (c) of fig. 9, which will be described later, and the tensile strength at the time of welding the ribbon 22 can be increased, and the conversion efficiency of the solar cell can be further improved. In addition, the composition of the soldering material of the ABS solder 11 is added with an appropriate amount of tin (Sn) of 20 to 95 wt%, zinc (Zn), aluminum (Al), silicon (Si), and the like. As for these mixing ratios, the most preferable mixing ratio is determined by experiments according to the melting temperature, the ABS welding target such as the substrate or the solder ribbon.
The ABS solder material supply mechanism 12 is a mechanism for supplying the ABS solder 11 to the soldering tip 12 at a predetermined speed (a predetermined amount of solder, which will be described later) in accordance with the moving speed of the soldering tip 22 relative to the substrate 1.
The solder ribbon 13 is a portion of the substrate 1 having a via hole soldered to the back surface (aluminum electrode) 2 of the substrate or a portion which has been subjected to pre-soldering, and takes out a current or the like from the substrate 1 to the outside. In addition, as shown in part (a) of fig. 1, when the ABS solder 11 is supplied, the substrate 1 of the portion of the hole of the substrate back surface 2 is pre-soldered (ultrasonic-welded), and as shown in part (b) of fig. 1, when the solder ribbon 13 is supplied superposed on the ABS solder 11, the solder ribbon 13 is soldered (ultrasonic-welded) to the substrate 1 of the portion of the hole of the substrate back surface 2. In the case where the pre-welding has been performed, the weld tape is welded to the pre-welded portion in a general welding (no ultrasonic welding) in a later step. In addition, instead of supplying the ABS solder overlapping the solder ribbon 13, a solder ribbon with solder formed by soldering the ABS solder 11 to the solder ribbon 13 in advance may be used. In this case, the solder ribbon with solder needs to have the solder sufficiently soldered to the solder ribbon 13 in advance so that about 0.1mm or more of the solder protrudes from the edge of the hole onto the substrate back surface 2 (aluminum electrode).
The soldering iron 21 heats the soldering tip 22 to a predetermined temperature and supplies ultrasonic waves.
The soldering iron tip 22 is attached to the front end of the soldering iron 21, ultrasonic waves are applied to the parts to be soldered (the portion of the hole of the substrate back surface 2, etc.), and the molten ABS solder 11 is supplied and soldered.
The soldering iron heating power supply 23 supplies power to the soldering iron tip 22 to a predetermined temperature, and detects the temperature of a portion of the soldering iron tip 22 and has an automatic temperature adjustment mechanism.
The soldering iron ultrasonic power generating means 24 supplies ultrasonic waves from the soldering iron tip 22 to a portion to be soldered (a portion of a hole of the substrate back surface 2, etc.). The power of the ultrasonic wave (power source power) may be about 1 to 10W, and if the power is too low, an ultrasonic welding failure may occur, and if the power is too high, the film (aluminum electrode film, etc.) may be destroyed by the ultrasonic wave, and a welding failure may occur, and therefore, the most preferable power is determined by experiments. Usually 1 to several watts are used.
The moving mechanism 25 is a mechanism for automatically moving the soldering iron 21 at a predetermined speed, and in this case, is a mechanism for moving the soldering iron rightward at a predetermined speed. The predetermined speed is adjusted (by experimental adjustment, refer to fig. 4 and its description) in conjunction with the ABS solder material supply mechanism 12 for automatically supplying the ABS solder 11: the ABS solder 11 is soldered in such a manner that the ABS solder 11 protrudes from the edge of the hole of the substrate back surface 2 to about 0.1mm or more and usually within 3mm above the aluminum electrode of the substrate back surface 2.
Next, the operation of the configuration of fig. 1 will be described.
(1): the substrate (rectangular substrate of about 150 mm) 1 is placed on a stage (not shown) having a preliminary heater 3, and the temperature is adjusted to a temperature slightly lower than the melting temperature of the ABS solder 11 (the temperature is determined by experiment).
(2): the soldering iron 22 is heated to a predetermined temperature by the power supplied from the soldering iron heating power supply 23, and ultrasonic waves are generated by the soldering iron ultrasonic wave power generating means 24 and supplied to the soldering iron 22 (the heating temperature and the ultrasonic wave power are different depending on the material of the ABS solder 11, and are determined for each material by experiments).
(3): as shown in fig. 1 (a), while the ABS solder 11 is melted by the soldering tip 22, ultrasonic waves are supplied (in a lightly pressed state) to the substrate 1 at the hole portion of the substrate back surface (aluminum electrode) 2, and the soldering tip 22 is moved rightward in the drawing by the moving mechanism 25. At the same time, the ABS solder 11 is supplied from the ABS solder material supply mechanism 12 at a predetermined speed and moved so that the melted ABS solder 11 is soldered by protruding from the edge of the hole of the substrate back surface 2 to the substrate back surface (aluminum electrode) 2 by about 0.1mm or more (the moving speed of the soldering tip 22 and the supply amount of the ABS solder 11 are determined by experiments so as to satisfy these relationships, at this time, the heating temperature and the ultrasonic power are also adjusted together).
(4): as described above, as shown in part (a) of fig. 1, when only the ABS solder 11 is supplied, the ABS solder 11 is soldered onto the substrate 1 at the portion of the hole of the substrate back surface (aluminum electrode) 2, and is soldered onto the substrate back surface (aluminum electrode) 2 in such a manner as to protrude from the edge of the hole by about 0.1mm or more to about 3mm or less (refer to fig. 4).
(5): in the case of prewelding in (4), a solder ribbon is welded (ultrasonic-free welding using general welding) to the prewelded portion in the latter step, and this is taken out as a lead line to be connected to the outside.
(6): further, instead of (4) and (5), as shown in part (b) of fig. 1, in the case where the ABS solder 11 is supplied together with the solder ribbon 13 or in the case where the solder ribbon with solder is supplied, the ABS solder 11 is soldered to the substrate 1 of the portion with the punched hole of the substrate back surface (aluminum electrode) 2 and the ABS solder 11 is soldered in such a manner as to protrude from the edge of the hole to about 0.1mm or more to about 3mm or less on the substrate back surface (aluminum electrode) 2.
As described above, by pre-soldering the ABS solder 11 directly to the substrate 1 at the portion of the hole of the back surface (aluminum electrode) 2 of the substrate or soldering the solder ribbon 13 with the ABS solder 11, as will be described later, the efficiency of the solar cell can be improved, and by soldering the ABS solder 11 directly to the substrate 1 through the hole of the back surface substrate 2, the solder ribbon can be firmly fixed to the substrate 1.
In an example of practical implementation, the substrate heating temperature (preheat) is standardized to 180 ℃ and at least the upper limit temperature is 200 ℃ or lower (temperature at which the ABS solder does not melt or lower). If this temperature is exceeded, the substrate will be damaged. In this case, the soldering iron temperature was 400 ℃. Up to about 500 deg.c. This is adjusted by the moving speed of the soldering tip and the solder material supplying speed. The faster the speed, the higher the temperature. The ultrasonic output was 6 watts or less on the back side and 3 watts or less on the front side. The above conditions apply to solder materials having a melting point of about 217 c and a major material being an alloy of tin and zinc. Depending on the soldering material, the type of substrate, the moving speed of the tip, the solder supply amount, and the like, it is necessary to perform experiments on the preheating temperature, the tip (soldering iron) temperature, the tip moving speed, the solder supply speed, and the like to adjust to the most appropriate conditions so that good ultrasonic soldering can be performed.
Next, the operation of the configuration of fig. 1 will be described in detail in accordance with the sequence of the flowchart of fig. 2.
Figure 2 shows an operational description flow diagram of the invention (in its entirety).
In fig. 2, the step S1 is to prepare a Si substrate.
Step S2 is to perform surface treatment. This step is to form a nitride film on the silicon substrate (for example, N-type) prepared in step S1, and further, to form a pattern of finger electrodes, bus bar electrodes, and the like. In this step, as in the conventional example of fig. 6, a nitride film 32 is formed on the front surface side of a silicon substrate 31, and finger electrodes 33, bus bar electrodes 34, and the like are patterned.
Step S3 is to perform back processing. In this step, an Aluminum pattern is formed on the back surface of the silicon substrate, and an Aluminum electrode having a via hole is formed by using Aluminum paste (Aluminum paste) by screen printing, for example, on the entire back surface of the silicon substrate. Subsequently, the present invention proceeds to step S5.
Step S5 is sintering. This step is to collectively sinter the patterns formed by the surface treatment of the step S2 and the back surface treatment of the step S3.
As described above, the present invention may form finger electrodes, bus bar electrodes on the front surface side of the substrate and aluminum electrodes perforated on the back surface side in steps S1 to S3 and S5.
The step S6 is to perform measurement (1). This step can measure the electrical characteristics of the solar cell before ABS soldering using a probe before ABS soldering at step S7 (refer to the pre-soldering data of fig. 5).
And step S7 is ABS welding. This step directly welds ABS solder to the substrate 1 of the holed portion of the aluminum electrode of the Si substrate, and the welding is performed in such a manner as to protrude from the edge of the hole by about 0.1mm or more onto the aluminum electrode. Further, the solder ribbons 13 may be welded together (see fig. 1 (b)).
The step S8 is to perform measurement (2). This step can measure the electrical characteristics of the solar cell after the ABS soldering at step S7 (refer to the soldered data of fig. 5).
As described above, the nitride film is formed on the front surface of the Si substrate, and the finger electrodes, the bus bar electrodes, and the like are patterned, and the aluminum electrodes having the punched holes are patterned on the rear surface of the Si substrate and then collectively sintered, thereby forming these patterns.
On the other hand, conventionally, after the steps S1 to S3, a silver paste was further coated on the Si substrate in the step S4. In this case, in a part of the aluminum electrode having the punched holes formed in the back surface treatment in step S3, the silver paste is further screen-printed to form a silver pattern on the Si substrate inside the holes of the aluminum electrode. Further, as in the present invention, by performing the steps S5 to S8, a nitride film is formed on the front surface of the Si substrate, and a pattern of finger electrodes, bus bar electrodes, and the like is formed, and a silver pattern is formed inside the pattern of aluminum electrodes perforated on the back surface of the Si substrate, and a solder ribbon is soldered thereto to make an external take-out line, which can be firmly fixed to the substrate by the silver pattern.
FIG. 3 shows a detailed operation flowchart of the present invention. This step is a detailed flowchart of the ABS welding of step S7 of fig. 2.
In fig. 3, the step S11 is to preheat the substrate. In this step, the substrate 1 of fig. 1 is preheated by the substrate heater 3 in a state where the substrate 1 is placed on a stage not shown, and is heated to a temperature slightly lower than a temperature at which the ABS solder 11 melts.
In step S12, the tip is heated and ultrasonic waves are applied. In this step, the soldering iron 21 is supplied with power from the soldering iron heating power supply 23 of fig. 1, the soldering iron tip 22 is heated to a predetermined temperature, and the soldering iron ultrasonic power generation means 24 supplies ultrasonic waves of a predetermined output to the soldering iron tip 22.
The S13 step is supplying ABS solder. This step is to supply the ABS solder 11 in a line or ribbon shape between the solder tip 21 and the portion to be soldered at a predetermined speed from the ABS solder supply mechanism 12 of fig. 1. The ABS solder 11 is supplied in such a manner that it is supplied to the punched portion of the substrate back surface 2 and protrudes from the edge of the hole to about 0.1mm or more above the substrate back surface (aluminum electrode) 2 (see fig. 4, the supply amount is determined by experiment). As shown in fig. 1 (b), when the solder ribbon 13 is soldered, the solder ribbon 13 may be supplied so as to overlap with the ABS solder.
Step S14 is moving the soldering iron tip. This step moves the soldering tip 22 of fig. 1 with the moving mechanism 25 and to the right in fig. 1.
As described above, the soldering iron tip 22 may be moved to perform ultrasonic soldering so that the ABS solder 11 is soldered to the punched portion of the substrate back surface 2 and protrudes from the edge of the hole by about 0.1mm or more above the substrate back surface 2.
FIG. 4 is a photograph of an example of the present invention.
Part (a) of fig. 4 shows a photograph of the sample having a contact width of about 0.1mm, part (b) of fig. 4 shows a photograph of the sample having a contact width of about 0.5mm, and part (c) of fig. 4 shows a photograph of the sample having a contact width of about 1.0 mm. Here, examples of photographs are shown in which the ABS solder 11 is soldered so that the transverse ribbon in each photograph can just cover (about 0.1mm, 0.5mm, 1.0mm in projection) the ribbon hole of the rear substrate 2.
FIG. 4 (a-1), (b-1), and (c-1) show schematic side views of part (a), (b), and (c) of FIG. 4, respectively. The contact width is a projection amount from the edge of the hole onto the substrate back surface (Al)2, and shows examples of about 0.1mm, 0.5mm, and 1.0 mm.
As described above, a band-shaped hole is provided in the rear substrate (aluminum electrode) 2 formed on the substrate (Si)1, the ABS solder 11 is ultrasonically welded to a portion of the band-shaped hole (refer to portion (a) of fig. 1), or the solder ribbon 13 is superimposed on the ABS solder 11 and ultrasonically welded (refer to portion (b) of fig. 1), and the supply amount of the ABS solder 11 or the moving amount of the soldering iron 22 is adjusted to perform the ultrasonic welding so as to protrude from the edge of the hole to the rear substrate (aluminum electrode) 2 by about 0.1mm, 0.5mm, 1.0 mm.
Fig. 5 shows a measurement example of the present invention. This table shows examples of electrical characteristics of the solar cell measured before (before soldering) and after (after soldering) the ABS of the above-described part (a), (b) and (c) of fig. 4. Each measurement example shows an average value of ten measurement examples. Further, the electrical characteristics were measured by bringing the contact terminals into contact with the center portion of the strip-shaped hole of the substrate back surface (aluminum electrode) 2 of fig. 4 (the portion of the substrate 1 which was the center portion of the hole before soldering, and the portion of the solder which was the center portion of the soldered hole after soldering).
In fig. 5, the contact width of the part (a) corresponding to fig. 4 is about 0.1mm, the contact width of the part (b) corresponding to fig. 4 is about 0.5mm, and the contact width of the part (c) corresponding to fig. 4 is about 1.0 mm. Here, Isc represents a short-circuit current of the solar cell, Voc represents an open-circuit voltage of the solar cell, EFF represents a maximum efficiency of the solar cell, and FF represents a maximum efficiency/(VocxIsc) of the solar cell. "before soldering" is a numerical value before soldering the ABS solder, "after soldering" is a numerical value after soldering the ABS solder, and "variation" is a variation from before soldering to after soldering.
Here, the maximum Efficiency (EFF) is:
the variation of "one time" (contact width about 0.1mm) of the measurement example was-0.40;
the variation of "two times" (contact width about 0.5mm) of the measurement example was-0.18;
the amount of change in "three times" (contact width about 1.0mm) of the measurement example was-0.13;
it is found for the first time in this experiment that the variation in maximum efficiency from "before soldering" to "after soldering" is reduced as the contact width is increased, that is, the variation in maximum efficiency from "before soldering" to "after soldering" is reduced as the amount of protrusion of the ABS solder 11 from the edge of the hole of the aluminum electrode (substrate back surface) 2 onto the aluminum electrode 2 is increased to about 0.1mm, 0.5mm, 1.0 mm.
That is, by increasing the amount of protrusion of the ABS solder 11 from the edge of the hole of the aluminum electrode (substrate back surface) 2 onto the aluminum electrode 2 to about 0.1mm, 0.5mm, 1.0mm, a path for electrons to be emitted from a portion (0.1mm, 0.5mm, 1.0mm) of the protruding ABS solder 11 to the substrate 1 through the aluminum electrode is added (increased), corresponding to this portion, and the highest efficiency is improved.
Drawings
FIG. 1 is a view showing the structure of the first embodiment of the present invention.
Fig. 2 is a flowchart illustrating the operation of the present invention (overall).
FIG. 3 is a flowchart illustrating the detailed operation of the present invention.
FIG. 4 is a photograph of an example of the present invention.
Fig. 5 shows a measurement example of the present invention.
Fig. 6 is an explanatory diagram of a known technique.
Description of the reference numerals
1 base plate (silicon substrate)
2 back of base plate (aluminum)
3: substrate heater (preheating)
11 ABS solder
12 ABS welding material supply mechanism
21: soldering iron
22 soldering iron head
23, iron heating power supply
24 ultrasonic wave power generating mechanism for soldering iron
25, a moving mechanism.

Claims (9)

1. A solar cell forming a region where a high electron concentration is generated when light is irradiated onto a substrate and forming an insulating film through which light can pass on the region, forming a finger electrode on the insulating film, the finger electrode being an extraction port for extracting electrons from the region, the solar cell extracting the electrons to the outside through the finger electrode and flowing the electrons from a back surface of the substrate to form a circuit, wherein,
forming an aluminum electrode on the entire back surface of the substrate, forming a hole in a part of the electrode, or forming an aluminum electrode having a hole formed in a part of the entire back surface of the substrate, welding the substrate in the hole, and welding the aluminum electrode so as to protrude from the edge of the hole by 0.1mm or more above the aluminum electrode
Electrons are caused to flow into the substrate from the inside of the soldered hole and the aluminum electrode protruding by 0.1mm or more from the edge of the hole, respectively, thereby increasing the conversion efficiency of the solar cell.
2. The solar cell according to claim 1, wherein a portion of the aluminum electrode where the hole is formed is a portion corresponding to the take-out line of the front surface.
3. The solar cell of any of claims 1-2, wherein the welding is ultrasonic welding.
4. The solar cell according to any of claims 1 to 3, wherein the welding only welds the solder, or welds the solder to a take-out line, or welds a take-out line that has been pre-welded.
5. The solar cell according to any one of claims 1 to 4, wherein the soldering is performed in a state where a temperature of a portion to be soldered is preheated to a temperature below a temperature at which solder is melted and above room temperature.
6. The solar cell of any of claims 1-5, wherein the solder contains one or more of zinc, aluminum, silicon in tin.
7. The solar cell of claim 6, wherein the solder is free of Pb, Ag, Cu.
8. The solar cell according to any one of claims 1 to 7, wherein the welding performed to protrude from the edge of the hole by 0.1mm or more from the upper side of the aluminum electrode is performed to protrude by 0.1mm or more and 3.0mm or less from the upper side of the aluminum electrode.
9. A method of manufacturing a solar cell which forms a region where a high electron concentration is generated when light is irradiated onto a substrate, forms an insulating film through which light can pass on the region, forms a finger electrode on the insulating film, the finger electrode being an extraction port for extracting electrons from the region, extracts the electrons to the outside through the finger electrode, and flows the electrons from the back surface of the substrate to form a circuit,
the manufacturing method comprises forming an aluminum electrode on the entire back surface of the substrate, forming a hole in a part of the electrode, or forming an aluminum electrode with a hole formed in a part of the entire back surface of the substrate, welding the aluminum electrode on the substrate in the hole, and welding the aluminum electrode so as to protrude from the edge of the hole by 0.1mm or more above the aluminum electrode
Electrons are caused to flow into the substrate from the inside of the soldered hole and the aluminum electrode protruding by 0.1mm or more from the edge of the hole, respectively, thereby increasing the conversion efficiency of the solar cell.
CN201980042980.2A 2018-06-26 2019-06-22 Solar cell and method for manufacturing solar cell Pending CN112352320A (en)

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