TW202015246A - Solar cell and method for manufacturing solar cell - Google Patents

Abstract

The present invention relates to a solar cell and a method for manufacturing solar cell, with an objective of improving conversion efficiency and increasing the fixing strength of ribbons on the back surface, and eliminating Ag patterns between the ribbon and the substrate to prevent the conversion efficiency from being reduced and preventing conversion efficiency from being decreased due to temperature cycle test, by soldering the ribbon directly to a hole portion of an aluminum electrode on the back surface of the substrate with the ribbon slightly protruding over the aluminum electrode from the edge of the hole. A hole is formed in a part of an aluminum electrode after the aluminum electrode is formed on the entire back surface of the substrate, or an aluminum electrode in which a hole is formed in a portion of the entire back surface of the substrate is formed, and a ribbon is soldered after a solder is directly formed on the substrate inside the hole, or the ribbon is soldered directly to the substrate inside the hole, with the ribbon protruding over the aluminum electrode from the edge of the hole by 0.1mm or more.

Description

Solar cell and method for manufacturing solar cell

The present invention relates to a solar cell and a method of manufacturing a solar cell. The solar cell forms an area for generating a high electron concentration when light is irradiated on a substrate, and forms an insulating film that transmits light on the area. A finger electrode is formed on the finger electrode, which is an outlet for taking out electrons from the area. The solar cell takes out the electrons through the finger electrode to the outside and the ribbon (also called "bonding wire") Soldering to the part of the hole formed in the aluminum electrode on the back of the substrate, and welding is carried out in such a way that it protrudes from the edge of the hole above the upper side of the aluminum electrode by 0.1 mm, so as to increase the conversion efficiency and improve the fixing strength of the back side of the ribbon, And there is no Ag pattern between the solder tape and the substrate to prevent the reduction of conversion efficiency, and at the same time prevent the reduction of conversion efficiency due to temperature cycle testing.

Conventionally, in the design of solar cells, the focus has been on efficiently flowing electrons generated in solar cells to the connected external circuits. 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.

For example, as shown in the conventional technique of FIG. 11, on the front surface of the silicon substrate 31 (upper A nitride film 32 is formed on the surface), and the paste of the finger electrode (silver) 33 (containing lead-containing glass) is screen-printed and sintered on the nitrogen electrode as shown in the figure. A hole is formed in the chemical film 32 to form a finger electrode 33 for taking electrons from the high electron concentration region to the outside. Next, screen printing and sintering are performed in a direction orthogonal to the finger electrodes 33 to produce bus bar electrodes (silver) 34. A solder tape (lead) 35 is soldered to the bus bar electrode (silver) 34 with solder 36 to firmly fix the solder tape 35 to the silicon substrate 31.

In addition, an aluminum electrode 37 is formed on the back surface (lower surface) of the silicon substrate 31, and a solder tape 39 is soldered and fixed thereto.

In addition, if the aluminum electrode 37 is formed on the entire back surface and the soldering strength of the solder tape 39 is weak, a part of the aluminum electrode 37 (the portion corresponding to the bus bar electrode 34 on the front surface) is drilled first, and Here, the silver paste is screen-printed and sintered to form the silver portion 371, and the solder tape 39 is fixed with the solder 38 to obtain the necessary fixing strength.

However, when the aluminum electrode is formed on the entire back surface of the silicon substrate 31 and the solder tape 39 is soldered thereon, there is a problem that the solder tape 39 cannot be fixed to the silicon substrate 31 with sufficient strength.

In addition, there is a problem that in order to prevent this from happening, as shown in FIG. 11 above, it is necessary to first drill a hole in a part of the aluminum electrode 37 and apply silver paste on it and sinter it, and then solder the ribbon 39 Welded on it to obtain sufficient fixing strength.

Furthermore, as mentioned above, when a silver paste is applied to the hole formed in a part of the aluminum electrode 37 and sintered, and then the soldering tape 39 is welded thereon, since the silver pattern is fixed on the substrate and applied thereto Solder ribbon 39 is applied to allow electrons to flow in the path of the ribbon 39-silver pattern-substrate, so the conversion efficiency of the solar cell will be reduced, or even the conversion efficiency will be reduced due to TC (thermal cycling) test Phenomenon, we are looking forward to solving this problem.

The inventors found through experiments that soldering directly to a part of the hole of the aluminum electrode on the back of the substrate and soldering in a manner slightly protruding from the edge of the hole will increase the conversion efficiency and improve the fixing strength of the solder tape on the back, and There is no Ag pattern between the solder tape and the substrate to prevent the reduction of conversion efficiency, and at the same time to prevent the reduction of conversion efficiency due to temperature cycle testing.

Therefore, in the solar cell of the present invention, a region where high electron concentration is generated when light is irradiated on the substrate is formed, and a light-permeable insulating film is formed on the region, and a finger electrode is formed on the insulating film. The finger electrode It is an outlet for taking out electrons from the area. The solar cell takes out the electrons to the outside through finger electrodes and allows electrons to flow in from the back surface of the substrate to form a circuit, wherein aluminum electrodes are formed on the entire back surface of the substrate After that, a hole is formed in a part of the electrode, or an aluminum electrode with a hole is formed in a part of the entire back surface of the substrate, and the solder tape is welded after welding directly on the substrate inside the hole, or the solder tape is directly welded into the hole On the substrate, and soldered in such a way that the edge of the hole protrudes above the aluminum electrode by 0.1 mm or more, so that the electrons protrude from the portion of the substrate inside the welded hole and the aluminum electrode protruding from the edge of the hole by 0.1 mm or more Part of the inflow to increase the conversion efficiency, and between the ribbon and the substrate There is no Ag pattern to prevent the reduction of conversion efficiency and the reduction of conversion efficiency caused by temperature cycle test.

At this time, the portion of the aluminum electrode where the hole is formed corresponds to the lead wire (solder tape, lead) on the front.

In addition, the welding system is ultrasonic welding.

In addition, the soldering system performs soldering in a state where the temperature of the part to be soldered is preheated below the temperature at which the solder will melt and above the room temperature.

In addition, the solder contains at least one of zinc, aluminum, and silicon in tin, and does not contain Pb, Ag, or Cu.

In addition, the welder protrudes from the edge of the hole by 0.1 mm or more above the aluminum electrode and performs welding, and the welder protrudes from the upper side of the aluminum electrode by 0.1 mm or more and 3.0 mm or less.

As described above, the present invention realizes welding a part of the hole of the aluminum electrode directly on the back surface of the substrate, and welding is performed in a manner of slightly protruding from the edge of the hole above the aluminum electrode to increase conversion efficiency and improve The structure and method of the fixed strength of the backside solder tape and no Ag pattern between the solder tape and the substrate to prevent the reduction of conversion efficiency and the reduction of conversion efficiency due to temperature cycle testing.

In this way, the present invention directly welds to a part of the hole of the aluminum electrode on the back of the substrate, reduces the resistance value of the part of the solder tape and is fixed to the substrate with sufficient fixing strength.

In addition, it has been confirmed through experiments that when welding is performed in such a way that the edge of the hole of the substrate protrudes above the aluminum electrode by 0.1 mm or more, the aluminum electrode that has been protruded and welded can be connected to this The connected aluminum electrode supplies electrons to the substrate to improve the conversion efficiency of the solar cell (refer to Figure 9 and Figure 10).

In addition, by soldering the soldering tape directly to the hole of the aluminum electrode on the back of the substrate, there is no Ag pattern between the soldering tape and the substrate to prevent the reduction of the conversion efficiency, and at the same time, the conversion efficiency due to the temperature cycle test can be prevented. (Refer to Figure 6).

1‧‧‧ substrate (silicon substrate)

2‧‧‧Back of substrate (silver electrode)

3‧‧‧Substrate heater

11‧‧‧ABS solder

12‧‧‧ABS welding material supply organization

21‧‧‧soldering iron

22‧‧‧Iron tip

23‧‧‧soldering iron heating power supply

24‧‧‧Sonic iron power generating mechanism

25‧‧‧Moving mechanism

31‧‧‧Si substrate

32‧‧‧Nitride film

33‧‧‧ finger electrode

34‧‧‧Bus electrode

35‧‧‧Solder tape

36‧‧‧Solder

37‧‧‧Aluminum electrode

38‧‧‧ solder

39‧‧‧Solder tape

371‧‧‧ Silver part

Fig. 1 is a structural diagram of a first embodiment of the invention.

Fig. 2 is a flowchart (overall) of the operation of the present invention.

Fig. 3 is a flowchart for explaining the detailed operation of the present invention.

FIG. 4 is an example of an IV curve between the present invention and the conventional one.

Figure 5 is a TC test example of the present invention.

Figure 6 is an example of the TC test results of the present invention.

Fig. 7 is a flowchart for explaining the operation of the present invention (2 of the whole).

Fig. 8 is a flowchart (2) illustrating the detailed operation of the present invention.

Figure 9 is an example of a sample photograph of the present invention.

Fig. 10 is a measurement example of the present invention.

Fig. 11 is an explanatory diagram of conventional technology.

[Example 1]

Fig. 1 is a structural diagram of a first embodiment of the invention.

Figure 1 (a) is a side view showing the whole; Figure 1 (b) is an enlarged view of the main part showing part (a) of Figure 1;

The substrate (silicon substrate) in Fig. 1 is a silicon substrate (single crystal, polycrystalline) for forming a solar cell.

The back surface of the substrate (Al) 2 is the back surface of the substrate 1 in which an aluminum electrode is formed on the entire back surface and a part of the substrate 1 is drilled, or an aluminum electrode with holes is formed on the entire back surface of the substrate 1.

The substrate heater 3 is a heater for preheating the substrate 1, and when soldered to the substrate 1, it is preheated to a temperature below the temperature at which the solder will melt and above the room temperature, and it has an automatic temperature adjustment mechanism.

The ABS solder 11 is a strip-shaped solder material, which has a shape such as a strip shape or a strip shape that facilitates the supply of solder for soldering to the back surface (aluminum electrode) 2 of the substrate. The soldering material is an alloy containing at least one of zinc (Zn), aluminum (Al), and silicon (Si) in tin (Sn), and does not contain lead (Pb), silver (Ag), or copper (Cu) ( Call it ABS solder 11). The melting point of the ABS solder 11 depending on these soldering materials is usually in the range of about 150°C to 350°C. Because it is determined by the blending ratio of the materials, the melting temperature is calculated by experiment and the optimal melting temperature is determined Preheating temperature (temperature above room temperature where ABS solder 11 will not melt), furthermore, it is experimentally determined that when the soldering iron tip 22 is heated and ultrasonic waves are applied, it will melt and solder the substrate 1 inside the hole in the substrate back 2 On the right temperature. As a result, ultrasonic welding as shown in the photographs (a), (b), and (c) of FIG. 9 described later can be performed, the tensile strength when welding the welding tape can be improved, and the solar cell can be further improved Conversion efficiency. In addition, the composition of the solder material of the ABS solder 11 is appropriately added with 20 to 95 wt% of tin (Sn), 3 to 60 wt% of zinc (Zn), aluminum (Al), silicon (Si) and other additives. Regarding these mixing ratios, the best mixing ratio is determined by experiment and according to the melting temperature, the substrate or the ABS welding object such as the soldering tape.

The ABS solder material supply mechanism 12 is a mechanism for supplying the ABS solder 11 to the soldering iron head 22 at a predetermined speed (a certain amount of solder, which will be described later) according to the moving speed of the soldering iron head 22 relative to the substrate 1.

The soldering tape 13 is welded to the part of the substrate 1 with holes drilled on the back side (aluminum electrode) 2 of the substrate or the part that has been pre-welded, and the current is taken out from the substrate 1 to the outside, or electrons are allowed to flow in. Also, as shown in FIG. 1(a), when the ABS solder 11 is supplied, the substrate 1 that is pre-soldered (ultrasonically welded) to the hole on the back surface 2 of the substrate is shown in FIG. 1(b) when When overlapping the ABS solder 11 to supply the solder tape 13, the solder tape 13 is soldered (ultrasonically welded) to the substrate 1 at the part of the hole on the back surface 2 of the substrate. In the case where pre-welding has been done, the welding tape is welded to the pre-welded part by general welding (non-sonic welding) in the subsequent steps. In addition, a solder ribbon with solder may be used instead of the case where the ABS solder is overlapped with the solder ribbon 13 and the solder ribbon is formed by soldering the ABS solder 11 to the solder ribbon 13. In this case, the solder tape with solder needs to be soldered to the solder tape 13 with a thick enough thickness so that about 0.1 mm or more solder protrudes from the edge of the hole onto the back surface 2 (aluminum electrode) of the substrate.

The soldering iron 21 heats the soldering iron head 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, applies ultrasonic waves to the parts to be soldered (portions of holes in the back surface 2 of the substrate, etc.), and supplies the melted ABS solder 11 and performs soldering.

The soldering iron heating power supply 23 supplies power so that the soldering iron tip 22 reaches a predetermined temperature, and detects the temperature of a part of the soldering iron tip 22 and has an automatic temperature adjustment mechanism.

The soldering iron ultrasonic power generating mechanism 24 supplies ultrasonic waves from the soldering iron head 22 to the part to be soldered (the part of the hole of the back surface 2 of the substrate, etc.). Ultrasonic power (power supply power) can be about 1 to 10W. If the power is too weak, poor ultrasonic welding will occur. If the power is too strong, the membrane (aluminum electrode, etc.) will be destroyed by ultrasonic waves, but poor welding may occur. Therefore, through experiments to determine the best power. It is usually carried out using 1 to several watts.

The moving mechanism 25 is a mechanism that automatically moves the soldering iron 21 at a predetermined speed. In this case, it is a mechanism that moves to the right at a predetermined speed. The predetermined speed is adjusted in conjunction with the ABS solder material supply mechanism 12 for automatically supplying the ABS solder 11 (adjusted through experiments) so that the ABS solder 11 protrudes from the edge of the hole on the back surface 2 of the substrate to the aluminum electrode on the back surface 2 of the substrate The ABS solder 11 is soldered in a manner of about 0.1 mm or more and usually within 3 mm.

Next, the operation of the structure of FIG. 1 will be described.

(1): Place the substrate (a rectangular substrate of approximately 150 mm) 1 on a table (not shown) with a pre-heater 3, and adjust the temperature to a temperature slightly lower than the melting temperature of the ABS solder 11 (the temperature is passed (Experimentally determined).

(2): The power supply from the soldering iron heating power supply 23 heats the soldering iron head 22 to a predetermined temperature, and the ultrasonic power generating mechanism 24 of the soldering iron generates ultrasonic waves and supplies the ultrasonic waves to the soldering iron head 22 (heating temperature, ultrasonic power system) It differs according to the material of the ABS solder 11, so each material is determined through experiment).

(3): As shown in FIG. 1 (a), while the ABS solder 11 is melted with a soldering iron tip 22, ultrasonic waves are supplied (under light pressure) to the part of the hole on the back of the substrate (aluminum electrode) 2 The substrate 1 moves the soldering iron head 22 to the right in the figure by the moving mechanism 25. At the same time, the ABS solder material supply mechanism 12 supplies the ABS solder 11 at a predetermined speed and moves it so that the The melted ABS solder 11 is soldered by protruding from the edge of the hole in the back surface 2 of the substrate to the back surface (aluminum electrode) 2 of about 0.1 mm or more (the moving speed of the soldering iron tip 22 and the supply amount of the ABS solder 11 are determined by experiments Satisfy these relationships. At this time, the heating temperature and ultrasonic power must also be adjusted together).

(4): As described above, as shown in FIG. 1 (a), when only ABS solder 11 is supplied, the ABS solder 11 is soldered to the substrate 1 at the part of the hole on the back surface (aluminum electrode) 2 of the substrate, and Solder to the back of the substrate (aluminum electrode) 2 by protruding from the edge of the hole by approximately 0.1 mm to approximately 3 mm (refer to Figure 9).

(5): In the case of (4) when pre-welding is done, the welding ribbon is welded to the pre-welded part in the later step (using general welding without ultrasonic welding), and it is connected to the outside Of the lead.

(6): In addition, instead of (4) and (5), as shown in FIG. 1 (b), when the ABS solder 11 is supplied with the solder tape 13 or when the solder tape with solder is supplied, Solder the ABS solder 11 to the back surface of the substrate (aluminum electrode) 2 with a hole in the substrate 1 and apply ABS solder so that it protrudes from the edge of the hole on the back surface of the substrate (aluminum electrode) 2 by about 0.1 mm to about 3 mm 11 Perform welding.

As described above, by directly pre-soldering the ABS solder 11 to the part of the hole of the back surface (aluminum electrode) 2 of the substrate or soldering the solder tape 13 with the ABS solder 11, as will be described later, the efficiency of the solar cell can be improved And the ABS solder 11 is directly soldered to the substrate 1 through the hole on the back surface 2 of the substrate, and the soldering tape can be firmly fixed to the substrate 1.

Moreover, in an example of actual implementation, the substrate heating temperature (preheating) is standardized to 180°C, and at least the upper limit temperature is 200°C or lower (below the temperature at which the ABS solder does not melt). If the substrate exceeds this temperature, it will be destroyed. In this case, the temperature of the soldering iron is 400°C. Up to about 500℃. This is adjusted by the moving speed of the soldering iron head and the welding material supply speed. The faster the speed, the higher the temperature. Regarding ultrasonic output, the back is 6 watts or less and the front is 3 watts or less. The above conditions apply to welding materials with a melting point of about 217°C and the main material being tin and zinc alloys. Depends on the soldering material, the type of substrate, the moving speed of the soldering iron head, the amount of solder supply, etc., must be preheating temperature, soldering iron (soldering iron) temperature, soldering iron head moving speed, solder supply speed, etc., to adjust to the most suitable Conditions so that good ultrasonic welding can be performed.

Next, the operation of the structure of FIG. 1 will be described in detail in accordance with the sequence of the flowchart of FIG. 2.

Fig. 2 is a flowchart (overall) of the operation of the present invention.

In the second figure, the Si substrate is prepared in step S21.

Step S22 is a surface treatment. This is to form a nitride film on the silicon substrate (for example, N-type) prepared in step S21, and in addition, a pattern of finger electrodes, bus bar electrodes, and the like is formed. This is similar to, for example, the conventional FIG. 11 in which a nitride film 32 is formed on the front side of the silicon substrate 31, and patterns of finger electrodes 33, bus bar electrodes 34, and the like are formed.

Step S23 is to perform the back side processing. In this step, an aluminum pattern is formed on the back surface of the silicon substrate. For example, an aluminum paste with aluminum paste is formed on the entire back surface of the silicon substrate by screen printing. Subsequently, the invention proceeds to step S25.

Step S25 is sintering. This is to sinter the pattern formed by the surface treatment in step S22 and the back surface treatment in step S23 in total.

As described above, in the present invention, in steps S21 to S23 and S25, finger electrodes and bus bar electrodes can be formed on the front surface of the substrate, and aluminum electrodes with holes drilled on the back surface can be formed.

Step S26 is to solder the ribbon with ABS solder. In this step, the soldering tape 13 is directly soldered to the substrate 1 of the aluminum electrode of the Si substrate 1 with ABS solder, and soldering is performed by protruding from the edge of the hole to the aluminum electrode by about 0.1 mm or more .

Step S27 is to measure (2). This step is to measure the electrical characteristics of the solar cell after ABS welding the welding tape 13 in step S26 (to be explained later using FIG. 3).

On the other hand, in the past, after steps S21 to S23, the silver paste was further applied to the substrate in step S24, sintered in step S25, and soldered with lead-containing solder (tin and lead) in step S27. The tape is soldered to the silver, the solder tape is firmly fixed to the substrate through the silver pattern, and measurement (2) is performed in step S28 to measure the electrical characteristics of the solar cell.

Fig. 3 is a flowchart for explaining the detailed operation of the present invention. This is a detailed flowchart of the measurement (2) in step S28 of FIG. 2.

In Figure 3, S31 is measured before the TC (thermal cycle) test (2-1). This step is the substrate in steps S26 (welding the ribbon with the ABS solder of the present invention) and S27 (soldering the ribbon with lead-containing solder to the conventional Ag, soldering with lead-free solder without ribbon) in Figure 2 Measure before the TC test (2-1). The measurement items are Isc, Voc, FF, EFF, etc. shown in Figure 4 to Figure 6 and Figure 10.

Step S32 is TC500 (500 hour/24 hour cycle). In this step, as shown in Figure 5 described later, the substrate 1 of the test object (steps S26 and S27 in Figure 2) is placed in a high-temperature/low-temperature test device, and as shown in the figure, the temperature is changed in a 24-hour cycle / Humidity, continuous testing for 500 hours. In this test, as shown in the graph of Figure 5, the test is performed within the range shown in Figure 5.

‧Temperature: -25.4℃ to 86.6℃

‧Humidity: 4.8 to 100%

Step S33 is a measurement (2-2). This step is to measure the electrical characteristics of the solar cell on the substrate 1 after testing the TC500 in step S32 (refer to FIG. 6).

Step S34 is to proceed to TC1000. This step is a 1000-hour/24-hour cycle test, which is longer than the TC500 of step S32 (refer to Figure 5).

Step S35 is to measure (2-3). This step is to measure the electrical characteristics of the solar cell on the substrate 1 after testing the TC1000 in step S34 (refer to FIG. 6).

As described above, for the substrate 1 completed in accordance with the flowchart of FIG. 2 (the present invention, the conventional with/without solder ribbon), the measurement before the thermal cycle test (2-1 ), after the measurement of TC500 (2-2), or even after the measurement of TC1000 (2-3). The results are shown schematically in Figures 4 and 6.

FIG. 4 is an example of an IV curve between the present invention and the conventional one. The horizontal axis represents the output voltage V of the solar cell, and the vertical axis represents the output current I of the solar cell. Here, by measuring the IV characteristics of the present invention and the conventional solar cell completed according to the flowchart of FIG. 2, a curve as shown in the figure will be obtained.

Here, the ABS is a solar cell according to the present invention, in which the welding ribbon is welded by the ABS method, and is completed in steps S21 to S23, S25, and S26 of the above-mentioned FIG. 2.

The Ref is a conventional solar cell in which the solder ribbon is soldered to Ag with lead-containing solder, and is completed in steps S21 to S25 and S27 in the above-mentioned FIG. 2.

When comparing the IV curve of the ABS of the present invention and the conventional Ref, it can be clearly judged from FIG. 4 that the ABS of the present invention is slightly larger than the Ref that soldered the ribbon to Ag with leaded solder.

Figure 5 is a TC test example of the present invention. Here, the horizontal axis represents time (h), the left end is 0 hours, and the right end is 1000 hours. The left side of the vertical axis represents temperature (°C), and the right side of the vertical axis represents humidity (%rh).

In Figure 5, the TC test environment is shown at the bottom right.

As mentioned above, the time 0 at the left end is the time point when the test is started, and the temperature change and humidity change are recorded, as shown by the curve in the figure. Here, the above-mentioned TC500 and TC1000 are tested according to the flow chart of the third figure above. By measuring the electrical characteristics of the substrate (solar cell) under test, the results shown in Figure 6 can be obtained according to the graph.

Figure 6 is an example of the TC test results of the present invention. Here, the substrates tested in the environment of the above-mentioned FIG. 5 are shown schematically (ABS solder of the present invention-Ag-free, conventional lead-containing solder, with solder ribbon, conventional lead-containing solder, solder-free ribbon) The three types of electrical characteristics. TC0 is the measurement result (2-1) before the test (refer to step S31 in Figure 3). TC500 is the measurement result (2-2) after the TC500 test (refer to step S33 in FIG. 3 of FIG. 3). TC1000 is the measurement result (2-3) after the test of TC1000 (refer to step S35 in Figure 3).

The Ref_A on the left has no solder tape (conventional lead-containing solder with Ag), as shown in the figure, a silver paste is applied to the hole portion of the aluminum electrode (back surface of the substrate) 2 formed on the back surface of the substrate 1 and Sinter to form a silver pattern, and do not solder the ribbon.

The central Ref_B series has a solder ribbon (the former leaded solder, with Ag), as shown in the figure, The silver paste is applied to the hole portion of the aluminum electrode (back surface of the substrate) 2 formed on the back surface of the substrate 1 and sintered to form a silver pattern, and a solder ribbon is welded.

The ABS on the right has a solder tape (ABS solder of the present invention, without Ag), as shown in the figure, the solder tape is directly soldered to the hole of the aluminum electrode (back surface of the substrate) 2 formed on the back surface of the substrate 1 with ABS solder No silver paste is applied and sintered to form a silver pattern.

‧About TC1000: Compare the three parties of EFF (conversion efficiency) (Ref_A, Ref_B, ABS), you will get the following measurement results as shown

‧Ref_A is -0.94%,

‧Ref_B is -1.17%,

‧ABS is -0.58%.

That is to say, regarding EFF (conversion efficiency), the ABS of the present invention has the smallest reduction in conversion efficiency even after the TC1000 test, and it has been confirmed through experiments that it is coated with silver paste on the conventional substrate and sintered to form The silver pattern, and compared with the case where the soldering tape is welded to the silver pattern, the reduction in conversion efficiency is about twice less.

Secondly, in the framework of FIG. 1 and in conjunction with FIGS. 7 to 10, the substrate 1 directly soldered to the inside of the hole formed in the back surface (aluminum electrode) 2 of the substrate will be described in detail in sequence with FIGS. Steps for soldering to protrude from the edge of the hole over the back surface (aluminum electrode) 2 of the substrate by 0.1 mm or more to improve conversion efficiency.

The operation of the structure of FIG. 1 will be described in detail according to the sequence of the flowchart of FIG. 7.

Fig. 7 is a flowchart for explaining the operation of the present invention (2 of the whole).

In FIG. 7, the S1 step is provided with a Si substrate.

Step S2 is a surface treatment. In this step, a nitride film is formed on the silicon substrate (for example, N-type) included in step S1, and patterns of finger electrodes, bus bar electrodes, and the like are formed. This is similar to, for example, the conventional FIG. 11 in which a nitride film 32 is formed on the front side of the silicon substrate 31, and patterns of finger electrodes 33, bus bar electrodes 34, and the like are formed.

The step S3 is to perform backside processing. In this step, an aluminum pattern is formed on the back surface of the silicon substrate. For example, a screen printed on the entire back surface of the silicon substrate is used to form a holed aluminum electrode with aluminum paste. And, the invention proceeds to step S5.

Step S5 is sintering. This step is to jointly sinter the pattern formed by the surface treatment in step S2 and the back treatment in step S3.

As described above, in the present invention, in steps S1 to S3 and S5, finger electrodes and bus bar electrodes can be formed on the front side of the substrate, and holed aluminum electrodes can be formed on the back side.

Step S6 is to measure (1). In this step, the electrical characteristics of the solar cell before ABS welding can be measured with a probe before the ABS welding in step S7 (refer to the data before welding in Figure 10).

Step S7 is ABS welding. In this step, ABS solder is directly soldered to the substrate 1 of the Si electrode's aluminum electrode with a holed portion, and soldering is performed in such a manner that it protrudes from the edge of the hole to about 0.1 mm or more on the aluminum electrode. In addition, the welding tape 13 may be welded together (refer to FIG. 1 (b)).

Step S8 is to measure (2). In this step, the electrical characteristics of the solar cell can be measured after the ABS welding in step S7 (refer to the data after welding in Figure 10).

As described above, a nitride film is formed on the front surface of the Si substrate and is formed There are patterns of finger electrodes, bus bar electrodes, etc., and patterns of aluminum electrodes with holes drilled on the back surface of the Si substrate are sintered together to form these patterns.

On the other hand, in the past, after steps S1 to S3, a silver paste was further applied on the Si substrate in step S4. This is a part of the aluminum electrode in which the hole is formed on the back surface process of step S3, a silver paste is further screen-printed, and a silver pattern is formed on the Si substrate inside the hole of the aluminum electrode. And, like the present invention, by performing steps S5 to S8, a nitride film is formed on the front surface of the Si substrate, and patterns of finger electrodes, bus bar electrodes, etc. are formed, and a hole is drilled on the back surface of the Si substrate A silver pattern is formed inside the aluminum electrode, and a solder ribbon is welded here to make an external lead, so that the external lead can be firmly fixed to the substrate through the silver pattern.

Fig. 8 is a flowchart (2) illustrating the detailed operation of the present invention. This step is a detailed flow chart of ABS welding in step S7 of Figure 7.

In Fig. 8, step S11 is to preheat the substrate. This step is to preheat the substrate 1 with the substrate heater 3 in a state where the substrate 1 of FIG. 1 is placed on a machine not shown, and heat the temperature to a temperature slightly lower than the temperature at which the ABS solder 11 will melt.

In step S12, the iron tip is heated and ultrasonic waves are applied. This step supplies power to the soldering iron 21 from the soldering iron heating power supply 23 of FIG. 1, heats the soldering iron head 22 to a predetermined temperature, and causes the soldering iron ultrasonic power mechanism 24 to supply the predetermined output ultrasonic wave to the soldering iron head 22.

Step S13 is to supply ABS solder. In this step, the ABS solder material supply mechanism 12 of FIG. 1 supplies the linear or ribbon ABS solder 11 between the soldering iron tip 22 and the portion to be soldered at a predetermined speed. The amount of ABS solder 11 is supplied in such a way that it is supplied to the backside 2 of the substrate with a hole drilled and protrudes from the edge of the hole over the backside (aluminum electrode) 2 of the substrate by about 0.1 mm or more Carry out the supply (refer to Figure 9, the supply is determined by experiment). Moreover, as shown in FIG. 1(b), when soldering the solder ribbon 13, it is only necessary to supply the solder ribbon 13 so as to overlap with the ABS solder.

Step S14 is to move the tip of the soldering iron. In this step, the moving mechanism 25 moves the soldering iron tip 22 in FIG. 1 and moves to the right in FIG. 1.

As described above, the ABS solder 11 can be soldered to the portion of the back surface 2 of the substrate where the hole is drilled and protruding from the edge of the hole by approximately 0.1 mm or so, the soldering iron tip 22 can be moved to perform ultrasonic soldering.

Figure 9 is an example of a sample photograph of the present invention.

Figure 9(a) shows a sample photo with a contact width of about 0.1mm, Figure 9(b) shows a sample photo with a contact width of about 0.5mm, and Figure 9(c) shows a sample photo with a contact width of about 1.0mm . Here, the figures show that the ABS solder is soldered in such a way that the horizontal strips in each photo can be just covered (protrusion amount is about 0.1 mm, 0.5 mm, 1.0 mm) on the strip holes on the back surface 2 of the substrate 11 photo examples.

(A-1), (b-1), and (c-1) of FIG. 9 show schematic side views of (a), (b), and (c) of FIG. 9, respectively. The contact width is the amount of protrusion from the edge of the hole to the back surface of the substrate (Al) 2, and shows examples of about 0.1 mm, 0.5 mm, and 1.0 mm.

As described above, in the substrate back surface (aluminum electrode) 2 formed on the substrate (Si) 1, a band-shaped hole is provided, and the ABS solder 11 is ultrasonically soldered to the part of the band-shaped hole (refer to the first (a) Figure), or superimposing the soldering tape 13 on the ABS solder 11 and performing ultrasonic welding (refer to FIG. 1(b)), and adjusting the supply amount of the ABS solder 11 or the moving amount of the soldering iron head 22 to remove the hole Ultrasonic welding is performed by protruding the edge to the back of the substrate (aluminum electrode) 2 by about 0.1 mm, 0.5 mm, and 1.0 mm.

Fig. 10 is a measurement example of the present invention. This table shows an example of measuring the electrical characteristics of solar cells before welding (before welding) and after welding (after welding) of ABS in Figure 9(a), Figure 9(b) and Figure 9(c) above. . Each measurement example shows the average value of ten measurement examples. In addition, the measurement is such that the contact terminal is in contact with the center portion of the strip-shaped hole on the back surface (aluminum electrode) 2 of FIG. The central part of the solder part) to measure electrical characteristics.

In Figure 10, the measurement example is one, two and three times, which correspond to Figure 9 (a), the contact width is about 0.1mm, (b) the contact width is about 0.5mm, (c) the contact width is about 1.0mm. Here, Isc represents the short-circuit current of the solar cell, Voc represents the open-circuit voltage of the solar cell, EFF represents the maximum efficiency of the solar cell, and FF represents the maximum efficiency of the solar cell/(VocxIsc). "Before soldering" means the value before soldering ABS solder, "After soldering" means the value after soldering ABS solder, and "Change" means the amount of change from before soldering to after soldering.

Here, the maximum efficiency (EFF) is:

‧The amount of change of "one time" (contact width about 0.1mm) of the measurement example is -0.40;

‧Measurement example "secondary" (contact width about 0.5mm) change amount is -0.18;

‧The variation of "three times" (contact width about 1.0mm) of the measurement example is -0.13;

With the increase of the contact width, the maximum efficiency change from "before soldering" to "after soldering" is reduced, that is, in this experiment, it is found for the first time that with the ABS solder 11 from the aluminum electrode (back side of the substrate) 2 The amount of protrusion of the edge of the hole onto the aluminum electrode 2 is increased to about 0.1mm, 0.5mm, 1.0mm, which reduces the amount of change from "before welding" to "after welding" for maximum efficiency.

That is, the amount of protrusion of the aluminum electrode 2 from the edge of the hole of the aluminum electrode (back side of the substrate) 2 to the aluminum electrode 2 by ABS solder 11 is increased to about 0.1 mm, 0.5 mm, 1.0 mm, and the addition (increase) allows the electrons to protrude from the A part (0.1mm, 0.5mm, 1.0mm) of the ABS solder 11 is transmitted through the aluminum electrode to the path of the substrate 1, and the highest efficiency is improved corresponding to this part.

1‧‧‧ substrate

2‧‧‧Back of substrate

3‧‧‧Substrate heater

11‧‧‧ABS solder

12‧‧‧ABS welding material supply organization

13‧‧‧Solder tape

21‧‧‧soldering iron

22‧‧‧Iron tip

23‧‧‧soldering iron heating power supply

24‧‧‧Sonic iron power generating mechanism

25‧‧‧Moving mechanism

Claims (7)

A solar cell forms an area where high electron concentration is generated when light is irradiated on a substrate, and an insulating film through which light is transmitted is formed on the area, and finger electrodes are formed on the insulating film. The finger electrodes are used for In the extraction port for extracting electrons from the aforementioned area, the solar cell extracts the aforementioned electrons to the outside through the finger electrode, and flows the aforementioned electrons from the back of the substrate to form a circuit, wherein, After forming an aluminum electrode on the entire back surface of the substrate, a hole is formed in a part of the electrode, or an aluminum electrode with a hole is formed in a portion of the entire back surface of the substrate, and soldering is directly performed on the substrate inside the hole Welding the welding tape, or welding the welding tape directly to the aforementioned substrate inside the hole, and welding so as to protrude 0.1 mm or more from the edge of the hole above the upper side of the aluminum electrode, Electrons flow from the part of the substrate inside the soldered hole and the part of the aluminum electrode projecting more than 0.1 mm from the edge of the hole to increase the conversion efficiency, and there is no Ag pattern between the solder tape and the substrate to prevent The reduction of conversion efficiency, and prevent the reduction of conversion efficiency caused by temperature cycle test. The solar cell as described in item 1 of the scope of the patent application, wherein the part of the aluminum electrode in which the hole is formed is the part corresponding to the take-out line on the front side. The solar cell according to any one of items 1 to 2 of the patent application scope, wherein the aforementioned welding is ultrasonic welding. The solar cell according to any one of claims 1 to 3, wherein the soldering is performed in a state where the temperature of the part to be soldered is preheated to a temperature below the temperature at which the solder will melt and above the room temperature. The solar cell according to any one of claims 1 to 4, wherein the solder contains at least one of zinc, aluminum, and silicon in tin, and does not contain Pb, Ag, or Cu. The solar cell according to any one of claims 1 to 5, wherein the edge of the hole protrudes above the aluminum electrode by 0.1 mm or more for welding, and protrudes above the aluminum electrode by 0.1 mm or more And the welding is less than 3.0mm. A method of manufacturing a solar cell, which forms a region that generates high electron concentration when light is irradiated on a substrate, and forms a light-permeable insulating film on the region, and forms a finger electrode on the insulating film, The finger electrode system is used to take out electrons from the area. The solar cell takes the electrons to the outside through the finger electrodes and flows the electrons from the back of the substrate to form a circuit. In this manufacturing method, after forming an aluminum electrode on the entire back surface of the substrate, a hole is formed in a part of the electrode, or an aluminum electrode formed with a hole in a portion of the entire back surface of the substrate is formed on the substrate inside the hole Welding the welding tape directly after welding, or welding the welding tape directly to the aforementioned substrate inside the hole, and welding so as to protrude from the edge of the hole above the upper side of the aluminum electrode by 0.1 mm or more, Electrons flow from the part of the substrate inside the soldered hole and the part of the aluminum electrode projecting more than 0.1 mm from the edge of the hole to increase the conversion efficiency, and there is no Ag pattern between the solder tape and the substrate to prevent The reduction of conversion efficiency, and prevent the reduction of conversion efficiency caused by temperature cycle test.

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