JP4221479B2 - Method for manufacturing thin film solar cell module - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a thin film solar cell module in which a plurality of unit cells are connected in series or in parallel.
[0002]
[Prior art]
Photoelectric conversion device using non-single crystal film, especially thin film of amorphous (amorphous) silicon (a-Si), polycrystalline silicon or microcrystalline silicon, which is a silicon-based non-single crystal thin film, is formed by plasma discharge. The thin film photoelectric conversion device thus produced is particularly expected in application to a large area thin film solar cell for electric power because it can be manufactured at a low cost at a low temperature with a large area as compared with a single crystal silicon device.
[0003]
Conventional thin-film solar cells generally use a glass substrate described later. In recent years, research and development of flexible solar cells using plastic films has been promoted and put into practical use in terms of weight reduction, workability, and mass productivity. Furthermore, the thing using the film substrate which carried out the insulation coating to the flexible metal material is also developed. Taking advantage of this flexibility, mass production became possible by a roll-to-roll method or a stepping roll method.
[0004]
In the above thin film solar cell, a first electrode (hereinafter also referred to as a lower electrode), a photoelectric conversion layer composed of a thin film semiconductor layer, and a second electrode (hereinafter also referred to as a transparent electrode) are laminated on an electrically insulating film substrate. A plurality of photoelectric conversion elements (or cells) are formed. By repeating electrically connecting the first electrode of a certain photoelectric conversion element and the second electrode of the adjacent photoelectric conversion element, the first electrode of the first photoelectric conversion element and the second electrode of the last photoelectric conversion element Can output the voltage required for For example, in order to obtain an alternating current of 100 V as a commercial power source by alternating current with an inverter, the output voltage of the thin-film solar cell is desirably 100 V or higher, and actually several tens or more elements are connected in series.
[0005]
Such a photoelectric conversion element and its series connection are formed by forming an electrode layer and a photoelectric conversion layer, patterning each layer, and a combination procedure thereof. As an example of the configuration and manufacturing method of the solar cell, the applicant of the present application has proposed a so-called SCAF (Series Connection through Apertures on Film) type thin film solar cell, which is described in, for example, JP-A-10-233517. Yes.
[0006]
FIG. 6 is a perspective view showing a simplified configuration of the SCAF type thin-film solar cell for easy understanding of the structure. In FIG. 6, the unit photoelectric conversion element 62 formed on the surface of the substrate 61 and the connection electrode layer 63 formed on the back surface of the substrate 61 are completely separated into a plurality of unit units, and are formed by shifting the separation positions. ing. For this reason, the current generated in the photoelectric conversion layer 65, which is an amorphous semiconductor portion of the element 62, is first collected in the transparent electrode layer 66, and then on the back surface through the current collecting holes 67 formed in the transparent electrode layer region. It leads to the connection electrode layer 63, and further to the outside of the transparent electrode layer region of the element adjacent to the element through the connection hole 68 for series connection formed outside the transparent electrode layer region of the element in the connection electrode layer region. The extended lower electrode layer 64 is reached, and both elements are connected in series.
[0007]
A simplified manufacturing process of the thin film solar cell is shown in FIGS. Using the plastic film 71 as a substrate (step (a)), a connection hole 78 is formed in this (step (b)), and a first electrode layer (lower electrode) 74 and a third electrode layer (connection electrode) are formed on both sides of the substrate. After (part) 73 is formed (step (c)), a current collecting hole 77 is formed at a position away from the connection hole 78 by a predetermined distance (step (d)). There is a step of patterning the lower electrode by laser processing the first electrode layer (lower electrode) 74 into a predetermined shape between the step (c) and the step (d). Omitted.
[0008]
Next, the semiconductor layer 75 to be a photoelectric conversion layer and the transparent electrode layer 76 to be the second electrode layer are sequentially formed on the first electrode layer 74 (step (e) and step (f)), and the third A fourth electrode layer (connection electrode layer) 79 is formed on the electrode layer 73 (step (g)). Thereafter, a thin film on both sides of the substrate 71 is separated using a laser beam to form a series connection structure as shown in FIG.
[0009]
In FIG. 7, the connection between the transparent electrode layer 76 and the fourth electrode layer 79 in the current collecting hole h2 is shown in two layers by overlapping each other, but in FIG. Are shown as one layer.
[0010]
FIG. 5 is a diagram schematically showing the configuration of the thin-film solar cell shown in FIG. 6 in a simplified and enlarged view for convenience of explanation of the present invention. FIG. 5 (a) is a plan view, and FIG. ) Shows an XX cross-sectional view in FIG.
[0011]
In FIG. 5, the same components as those in FIG. In FIG. 5, the connection electrode layer 63 is composed of two layers, a first connection electrode layer (third electrode layer) and a second connection electrode layer (fourth electrode layer), as described in FIG. Further, the cutting part 1h corresponds to the above-mentioned separation line, and the patterning ruled line part for the connection electrode layer and the cutting part 1g show the patterning ruled line part for the photoelectric conversion part on the substrate surface.
[0012]
In addition, the said thin film solar cell is normally insulated and protected and used as a module. As a solar cell module, in order to seal a thin film solar cell formed on an electrically insulating film substrate with an electrically insulating protective material, on both the light receiving surface side and the non-light receiving surface side of the solar cell. Those provided with a protective layer are known.
[0013]
FIG. 8 shows a side sectional view of an example of a schematic structure of a solar cell module.
[0014]
In FIG. 8, a solar cell 21 has a plurality of solar cell elements connected in series or in parallel, and is provided with a surface protection member 22 such as a glass plate on the light receiving surface side, and on both surfaces of aluminum foil on the back surface side. Back surface protection member 23 such as a moisture-proof protection sheet to which fluorinated ethylene (trade name: Tedlar, manufactured by DuPont) is bonded is provided, and EVA (ethylene-vinyl acetate copolymer resin), which is excellent in adhesive sealing property and inexpensive. It is heat-sealed and sealed with an adhesive resin sealing material 24. The thickness of EVA is, for example, 0.4 mm on both the light receiving surface side and the non-light receiving surface side.
[0015]
Further, the solar cell 21 has internal lead wires 25 and 26 electrically connected to the positive (+) and negative (−) electrodes, and the internal lead wires 25 and 26 are bonded and fixed to the back surface protection member 23. The terminal box 27 is guided through the back surface protection member 23 and is electrically connected to the core wires 29 and 30 of the cable 28 as an external lead wire inside the terminal box 27. Forming.
[0016]
The surface protection member 22 may be made of an organic material such as a translucent acrylic resin plate or a polycarbonate resin plate in addition to an inorganic material such as a glass plate. Further, as the back surface protection member 23, in addition to the resin containing the metal foil, an organic film alone such as a fluorine-based film, a composite material obtained by bonding an organic film and a metal foil, or a metal such as a metal plate or a glass plate・ Inorganic materials may be used.
[0017]
Next, the structure of a single-sided thin film solar cell in which a thin film solar cell is formed on one side of a glass substrate and an outline of the manufacturing process will be described. FIG. 4 shows an example of a manufacturing process of a series connection structure typically used in a glass substrate single-sided thin film solar cell. (A)-(f) of Drawing 4 shows the following, respectively. That is, (a) is a cross-sectional view of a state in which the first electrode layer 52 is formed on the glass substrate 51.
FIG. 5B is a cross-sectional view of the first electrode layer 52 laser patterned on the line 53.
(C) is a sectional view in which the photoelectric conversion layer 54 made of amorphous silicon or the like is formed in (b).
(D) is sectional drawing which carried out the laser patterning by the line 55 in (c).
(E) are cross-sectional views to form a transparent electrode layer 56, such as SnO ₂ in (d).
(F) is sectional drawing of the state which patterned the transparent electrode layer and the photoelectric converting layer collectively with the line 57, and completed the serial structure.
[0018]
By the process as described above, a glass substrate type solar cell in which a plurality of unit cells are electrically connected in series is formed. Also in this case, when modularized, it is sealed with an adhesive resin sealing material and is electrically protected.
[0019]
In the case of a glass substrate type solar cell, in the configuration shown in FIG. 4, 52 may be a transparent electrode layer and 56 may be a first electrode layer. That is, in this case, a transparent electrode layer is first formed on a glass substrate, and a photoelectric conversion layer and a first electrode layer (back electrode layer) are formed thereon.
[0020]
[Problems to be solved by the invention]
By the way, in the manufacturing method of the said conventional thin film solar cell module, there existed the following problems.
[0021]
In the film forming process, there is a problem that pinholes are generated due to dust or the like adhering to the substrate, and the first electrode (lower electrode) and the transparent electrode are electrically short-circuited. The cause of this problem is presumed to be that the transparent electrode is also extended and formed in the pinhole at the time of forming the transparent electrode layer. Electrical isolation (removal of the local short-circuit portion and insulation) can be achieved by applying a reverse bias voltage of several volts to the substrate. The reason is presumed that the transparent electrode in the pinhole is incinerated and removed by the generation of Joule heat due to the reverse bias voltage application process.
[0022]
For example, a reverse bias of 4 to 8 V is applied. As the applied voltage, first, a voltage of about 2 V is applied, and the leakage current for each unit cell is measured. A reverse bias is applied again to a cell having a leak current value of 10 to 20 mA or more at a voltage of about 4 to 8 V to burn out the leak point. After the reverse bias is applied, the initial characteristics of the solar cell are measured with white light and an intensity of 1 SUN (100 mW / cm ² ) in a solar simulator. Thereafter, the process proceeds to a laminating process of an adhesive resin sealing material and a protective layer, and modularization is performed.
[0023]
Normally, the reverse bias voltage application process improves the unit cell characteristics, but if there are too many pinholes or large pinholes, there are cells that cannot be recovered even if the voltage application process is performed. It was found that a new leak occurred after the laminating process. In particular, in the case of a high-current thin-film solar cell, the unit cell area increases (since the generated current is proportional to the unit cell area), the number of pinholes increases in proportion to the area, Therefore, the probability that such a pinhole that cannot be recovered remains high.
[0024]
In addition, if a large pinhole exists in the unit cell, the current that flows during the voltage application process concentrates on the large pinhole part, so other small pinholes cannot be recovered by the voltage application process, and the leakage current is expected. Sometimes did not go down to the level.
[0025]
Even if such unrecoverable pinholes remain in the unit cell, after modularization, the terminals of each unit cell of the thin-film solar cell are covered with the adhesive resin. Cannot be applied. Further, even if a reverse bias is applied to the entire thin film solar cell forming the series connection structure, a voltage is applied to a normal cell, and the voltage cannot be selectively applied to the leak point. Therefore, after the modularization, the initial characteristics of the solar cell whose characteristics are deteriorated cannot be recovered, and this problem has been a factor of reducing the manufacturing yield of the thin film solar cell module.
[0026]
The present invention has been made to solve the above-described problems, and an object of the present invention is to prevent the performance of the thin film solar cell from being deteriorated due to a local short circuit in the unit cell. An object of the present invention is to provide a method for manufacturing a thin-film solar cell module that improves the performance and the manufacturing yield.
[0027]
[Means for Solving the Problems]
In order to solve the above-described problem, in the present invention, a thin film of a first electrode layer, a photoelectric conversion layer, and a transparent electrode layer is laminated on the surface of a substrate having electrical insulation, and a ruled line is formed by patterning on a unit portion. Form a plurality of rectangular unit thin film solar cells (unit cells), electrically connect these unit cells in series, and provide protective layers on the light-receiving surface side and non-light-receiving surface side, and seal with adhesive resin It is a manufacturing method of the thin film solar cell module sealed with a material, Comprising: The following processes are included (invention of Claim 1).
1) A step of applying a reverse bias voltage to each unit cell after forming the plurality of unit cells and before sealing with an adhesive resin sealing material.
2) After applying the adhesive resin sealing material, forward bias voltage application processing is performed in which a current of ² SUN · min to 20 SUN · min (1 SUN = 100 mW / cm ² ) flows in the forward direction of each unit cell. The process to perform.
[0028]
As an embodiment of the invention of claim 1, the inventions of claims 2 to 5 below are preferable. That is, in the manufacturing method according to claim 1, the process of passing a current in the forward direction is a light irradiation process to the unit cell (invention of claim 2). Further, in the manufacturing method according to claim 1 or 2, the current value flowing in the forward direction is 0.5 times or more the short-circuit current value when the unit cell is irradiated with 1 SUN of light (invoice). Item 3).
[0029]
Furthermore, in the manufacturing method according to claim 1, the forward bias voltage application process is a voltage application process by a power source, and the power source is a pulse power source (invention of claim 4). Further, in the manufacturing method according to any one of claims 1 to 4 , the thin-film solar cell is cooled at the time of the forward bias voltage application process, and the surface temperature thereof is set to 25 ° C. or less (claim 5). Invention).
[0030]
[0031]
The operational effects of the above inventions will be generally described below. For example, when 1 SUN of light is applied to elements having a series connection structure, a certain current flows in all unit cells, and a voltage is generated respectively. FIG. 2 is a schematic diagram for explaining voltage-current characteristics (VI characteristics) when the leak levels of the a-Si / a-Si tandem cells are different.
As shown in FIG. 2, when 1 SUN light irradiation is performed, a voltage of 1.5 to 2 V is applied to a normal unit cell (non-defective cell).
[0032]
In FIG. 2, a small leak cell with a relatively small level of leak has a voltage substantially equal to this applied to each unit cell, so that the leak point can be burned out. However, in the case of a large leak cell having a relatively large level, the generated voltage becomes 1 V or less, and the leak point cannot be burned out. Therefore, it is effective to remove a large leak in advance by reverse bias processing.
[0033]
The current flowing in the forward direction is 0.5 times or more, preferably 2 times or more the short-circuit current value when light irradiation is performed, as in the invention of claim 4. Further, as in the invention of claim 5, the product of the processing time and the current value, that is, the product of the light irradiation intensity and the irradiation time is 2 SUN · min or more, preferably 20 SUN · min or more, and the light irradiation intensity is 2 SUN or more.
[0034]
Further, when the solar cell is irradiated with light, as in the invention of claim 7, cold air is blown so that the temperature of the light receiving surface of the solar cell is at least 25 ° C. or less, preferably 10 ° C. or less. It is desirable to provide a cooling mechanism on the table on which the camera is installed. This is to prevent the temperature-dependent open circuit voltage from being lowered as much as possible. FIG. 3 shows a schematic diagram of the VI characteristics when the cell temperature (T) is changed. As shown in this figure, when the temperature is relatively high, T2 is open compared to the relatively low temperature T1. The voltage drops. When the open circuit voltage is lowered, the voltage applied to each unit cell is lowered, and as a result, the short-circuit removing effect is reduced.
[0035]
Further, as in the sixth aspect of the invention, it is also preferable to apply a bias in the forward direction using a pulse power supply. The reason for using the pulse power source is to prevent the open circuit voltage from being lowered as much as possible when the solar cell is heated by Joule heat when a current flows through the solar cell.
[0036]
In order to irradiate a large area solar cell with light, a large facility is required. However, the advantage of the method of injecting current from an external power source such as a DC power source or a pulse power source is larger than that of light irradiation. It is in the point that it can be processed in a relatively short time without the need for equipment.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
(Example 1)
As a first embodiment, an example in which light irradiation is applied to the removal of a short-circuit portion will be described. As described above, a thin film solar cell using a-Si as a photoelectric conversion layer was formed on a plastic substrate by plasma CVD, and each unit cell was electrically separated by laser patterning. Then, after laminating with an EVA resin for the purpose of reinforcing against bending and bending, a reverse bias of 4 to 8 V was applied to remove a large leak point.
[0038]
As the applied voltage, a voltage of about 4V is first applied, the leakage current of each unit cell is measured, and a reverse bias is applied again to a cell having a leakage current value of 10 to 20 mA or more at a voltage of about 6 to 8V. And the leak point was removed. After applying the reverse bias, the initial characteristics of the solar cell were measured with a white light and an intensity of 1 SUN in a solar simulator.
[0039]
Then, the following modularization process was performed. The module was a glass cover module. (1) The solar cell electrode portion is wired so that the solar cell and the outside can be electrically connected. (2) After wiring, place a resin such as ETFE / EVA on the front and back sides so as to cover the entire solar cell except for the wiring part, and laminate using a laminator. After that, the excess outer periphery is cut with a cutter. (3) As a terminal box mounting step, the module is bonded and fixed to the terminal box using an adhesive. After the main wiring shaping, solder connection with the terminal board in the terminal box, and after curing the adhesive, attach the terminal box cover and complete the module. (4) Perform a characteristic test with white light and intensity of 1 SUN (100 mW / cm ² ). The value of the characteristic test at this time is set as the characteristic value “after modularization” in FIG.
[0040]
The thin-film solar cell module completed by the above process has a small leak in each unit cell after the laminating process, and the characteristics are deteriorated. The characteristic deterioration due to leakage varies depending on the unit cell, but is about 2 to 20%. As described above, even if a reverse bias is applied to the terminal of the module in this state, the voltage is only applied to the normal unit and not to the leaking unit. In order to solve this, the following light irradiation treatment was performed.
[0041]
The module after fabrication was irradiated with white light with an intensity of ² SUN (200 mW / cm ² ) for 10 minutes using a continuous light irradiation device, and then subjected to a characteristic test with white light and 1 SUN (100 mW / cm ² ). . The value of the characteristic test at this point is defined as the characteristic value after “light irradiation (2 SUN, 10 minutes)”.
[0042]
FIG. 1 is a diagram showing experimental results for 17 modules related to the effect of light irradiation of (2SUN, 10 minutes), and the “after modularization” and “after light irradiation (2SUN, 10 minutes)”. The generated power (W) is shown on the vertical axis. In FIG. 1, the remarkable point is that the variation in cell characteristics of 17 modules is smaller in “After light irradiation (2 SUN, 10 minutes)” than in “After modularization”. is there. The reason for this is that, after modularization, cells with large leaks have reduced leakage due to light irradiation and output has increased, while cells with relatively small leaks have had lower output due to light degradation peculiar to a-Si. Conceivable.
[0043]
As shown in FIG. 1, although the above-mentioned light degradation is somewhat observed, the generated power value is raised as a whole due to the effect of reducing the leakage due to light irradiation, and practically reaches the module shipping allowable level. In FIG. 1, when the good / bad judgment line of the produced solar cell is set to 4.2 W, for example, in the initial generated power, the initial generated power after “modularization” is 6 out of the total 17 solar cell modules. The individual is determined to be defective, and the non-defective product rate is about 64%. However, if the generated power after “light irradiation (2 SUN, 10 minutes)” is selected according to the above-mentioned good / bad judgment criteria, there is no defective product among all the 17 solar cell modules, and the good product rate is 100%.
[0044]
In the case of the embodiment of FIG. 1, (light intensity) × (light irradiation time) = 2 SUN × 10 minutes = 20 SUN · minute, but 2 SUN that is 0.5 times or more the short-circuit current value at 1 SUN.・ Characteristic recovery effect was seen even in minutes. The light source is not necessarily white light, and monochromatic light having a wavelength at which the solar cell absorbs light and generates power can be used instead.
[0045]
(Example 2)
In the solar cell module manufactured in the same procedure as in Example 1, the characteristic value after “modularization” is measured with white light / intensity of 1 SUN using a solar simulator, and then a current flows in the forward direction in the solar cell terminal portion. A direct-current power source was attached to the solar cell, and a forward bias was applied for several seconds to several tens of seconds after adjusting the current corresponding to the short-circuit current (about 100 mA) measured in “after modularization” to flow through the solar cell.
[0046]
At this time, the module was air-cooled so that the temperature of the solar cell would not rise due to Joule heat. As a result, a result almost similar to the result shown in FIG. 1 could be obtained. Further, as a current value, even when a current value (about 50 mA) about 0.5 times the short-circuit current measured in “after modularization” was passed, the effect of characteristic recovery was observed.
[0047]
Also, a bias was applied in the forward direction using a pulse power supply instead of a DC power supply. As a result of injecting current into the solar cell using the pulse power source, almost the same result as in Example 1 could be obtained.
[0048]
【The invention's effect】
According to the present invention, as described above, the first electrode layer, the photoelectric conversion layer, and the transparent electrode layer are stacked on the surface of the substrate having electrical insulation, and the unit portion is patterned and rectangular by the ruled lines. A plurality of unit thin film solar cells (unit cells) are formed, the unit cells are electrically connected in series, protective layers are provided on the light receiving surface side and the non-light receiving surface side, and sealed with an adhesive resin sealing material. A method for producing a thin film solar cell module,
1) a step of applying a reverse bias voltage to each unit cell after forming the plurality of unit cells and before sealing with an adhesive resin sealing material;
2) After applying the adhesive resin sealing material, forward bias voltage application processing is performed in which a current of ² SUN · min to 20 SUN · min (1 SUN = 100 mW / cm ² ) flows in the forward direction of each unit cell. To include a process to be performed,
It is possible to prevent the performance of the thin film solar cell from being deteriorated due to a local short circuit in the unit cell, and to improve the performance of the thin film solar cell and the production yield.
[Brief description of the drawings]
FIG. 1 is a diagram showing experimental results related to the effect of light irradiation according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining voltage-current characteristics when cell leakage levels are different. FIG. FIG. 4 is a diagram showing an example of a configuration process of a conventional glass substrate single-sided solar cell. FIG. 5 is a diagram showing a schematic configuration of a conventional SCAF type thin film solar cell. FIG. 7 is a perspective view showing a schematic configuration of a conventional SCAF type thin film solar cell. FIG. 7 is a schematic diagram showing a manufacturing process of a conventional SCAF type thin film solar cell. FIG. 8 is an example of a schematic structure of a conventional solar cell module. Side sectional view [Explanation of symbols]
21: Solar cell, 22: Surface protection member, 23: Back surface protection member, 24: Adhesive resin sealing material, 25, 26: Internal lead wire, 27: Terminal box, 31: Solar cell module, 51, 61, 71 : Substrate, 52, 64, 74: first electrode layer (lower electrode layer), 54, 65, 75: photoelectric conversion layer, 56, 66, 76: transparent electrode layer, 63: connection electrode layer, 67, 77: collection Electrode hole, 68, 78: connection hole, 73: third electrode layer, 79: fourth electrode layer.

Claims (5)

A thin film of a first electrode layer, a photoelectric conversion layer, and a transparent electrode layer is laminated on the surface of a substrate having electrical insulation, and a plurality of rectangular unit thin film solar cells (unit cells) are formed by ruled lines by patterning on a unit portion. A thin-film solar cell module that is individually formed, electrically connected in series with each other, provided with a protective layer on the light-receiving surface side and the non-light-receiving surface side, and sealed with an adhesive resin sealing material It is a method, Comprising: The manufacturing method of the thin film solar cell module characterized by including the following processes.
1) A step of applying a reverse bias voltage to each unit cell after forming the plurality of unit cells and before sealing with an adhesive resin sealing material.
2) After applying the adhesive resin sealing material, forward bias voltage application processing is performed in which a current of ² SUN · min to 20 SUN · min (1 SUN = 100 mW / cm ² ) flows in the forward direction of each unit cell. The process to perform. 2. The method of manufacturing a thin-film solar cell module according to claim 1, wherein the process of passing a current in the forward direction is a light irradiation process on the unit cell . 3. The manufacturing method according to claim 1 , wherein the current value to flow in the forward direction is 0.5 times or more of a short-circuit current value when the unit cell is irradiated with 1 SUN of light. Manufacturing method of thin film solar cell module. 2. The method of manufacturing a thin film solar cell module according to claim 1 , wherein the forward bias voltage application process is a voltage application process by a power source, and the power source is a pulse power source . 5. The thin film according to claim 1 , wherein the thin film solar cell is cooled during the forward bias voltage application process, and the surface temperature thereof is 25 ° C. or lower. Manufacturing method of solar cell module.

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