JP5852396B2 - Solar cell inspection method - Google Patents

Description

  The present invention relates to a solar battery inspection method for inspecting a solar battery including at least one solar battery cell.

  A silicon type solar cell is known as a method of utilizing solar energy. The manufacturing process of the solar cell affects whether or not it has the target power generation capacity. Therefore, it is important to evaluate the performance of the power generation capacity that is produced by the manufactured solar cell.

  As a method for evaluating the performance of a solar cell, a method using measurement of output characteristics by a solar simulator is known (see Patent Document 1). As a method different from this, there is a method in which current is applied in the forward direction to the solar battery cell to cause the current to flow in the forward direction, causing an electroluminescence (EL) action, and determining the quality of the solar battery cell from the light emitting state. Yes (see Patent Document 2). However, since Patent Document 2 determines whether or not the light is good only by the brightness of the emitted light from the solar battery cell, even if there is a crack, it is determined that the product is non-defective if the brightness is a predetermined value or more. However, if there is a crack, the power generation capability of the solar cell may be suddenly reduced, so it should be determined as a defective product.

  Patent Document 3 describes a technique for identifying a defective portion by flowing a forward current through a solar cell and photographing a temperature distribution. When a current is passed through the solar cell, for example, the contact resistance of the defective connection portion of the wiring increases, and thereby the defective connection portion generates heat.

  Patent Document 4 was filed on April 9, 2010 by the present applicant, and the contents of the application are as follows. This is an inspection apparatus and an inspection method capable of determining a defect in the absence of silicon, a defect due to residual stress remaining in a silicon substrate, and a defect due to contamination of impurities using Raman spectroscopy. In addition, the inspection device inspects solar cells more accurately by simultaneously using an EL inspection device that inspects defects by photographing EL emission light, a thermo inspection device that applies a thermographic image, and a Raman inspection device. It is also an inspection device.

JP2007-88419 WO2006 / 059615 JP-A-8-37317 Japanese Patent Application 2010-090110 Japanese Patent No. 4235685

  However, although the conventional inspection apparatus and inspection method can improve the accuracy of the solar cell inspection, there is a problem that the quality state of the module after all the manufacturing processes cannot be sufficiently confirmed. There is also a problem that the inspection result cannot be reflected in the manufacturing conditions.

  Furthermore, although an inspection result can be obtained, there is a problem that an optimum manufacturing condition is not known for solar cell modules of various standards or specifications. Therefore, once production starts under certain manufacturing conditions, a large amount of production is continued thereby, and a large number of defective products are generated.

  The present invention has been made in view of the above circumstances, and can accurately determine the quality of a solar cell module, reflect the inspection results, and obtain optimum manufacturing conditions for various solar cell modules. It aims at providing the inspection method of the solar cell which can do.

  In order to achieve the above object, a solar cell inspection method according to the present invention is characterized by the following configuration.

The method for inspecting a solar cell according to a first aspect of the present invention includes a production step for producing a solar cell under one manufacturing condition, an inspection step for inspecting a solar cell produced in the production step, and the result of the inspection step. A determination step of determining whether a state of the solar cell matches a preset performance of the solar cell; and, when the state of the solar cell does not match the preset performance of the solar cell, the production step If the manufacturing condition is changed, the production process, the inspection process and the determination process are performed again, and the re-judgment process is performed again. And a production condition determining step for determining as a condition suitable for the production process.
According to the method for inspecting a solar cell of the first invention, the quality of the solar cell can be accurately determined from the result of the solar cell inspection. In addition, since the manufacturing conditions suitable for one solar cell can be known, the yield can be greatly improved. Furthermore, it is possible to prevent a large number of defective products from being generated.

According to a second invention, in the first invention, the inspection step includes a thermo imaging inspection, an EL imaging inspection, and a Raman spectroscopic inspection.
According to the second invention, the solar cell can be more accurately inspected, and the accuracy of the manufacturing conditions is improved.

The third invention is characterized in that, in the second invention, the thermo imaging inspection, the EL imaging inspection, and the Raman spectroscopic inspection review at least one inspection condition using at least two inspection results.
According to the third invention, the accuracy of inspection of the solar cell is further improved.

A fourth invention is characterized in that in the first to third inventions, a numbering step of assigning a number to a solar cell produced after the production condition determining step is included.
According to the fourth aspect of the invention, it becomes possible to follow-up observation of aged deterioration of a solar cell produced under certain manufacturing conditions, and to elucidate the cause of quality deterioration.

According to a fifth invention, in the first to fourth inventions, the inspection step is provided after a laminating step in a production step.
According to the fifth aspect of the present invention, the inspection and the manufacturing conditions can be reviewed as a process of the production process placed in the production line.

The figure which shows the structure of the solar cell panel of test object. The top view which looked at one photovoltaic cell from the light-receiving surface. The figure which shows the post-process of solar cell production. The figure which shows the inspection process of the solar cell of this invention in detail. The figure which shows the correlation of the test result of EL imaging | photography inspection, and the test result of thermo imaging | photography inspection. The figure which shows the correlation of the test result of EL imaging | photography test | inspection, and the test result of a Raman spectroscopic test | inspection. The figure explaining the aged deterioration of a solar cell.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<1> Configuration of Solar Cell Panel The solar cell panel 10 as an inspection target handled by the inspection apparatus of the present embodiment will be described. 1A and 1B are diagrams showing a configuration of a solar cell panel 10 of a device to be inspected, where FIG. 1A is a plan view and FIG. 1B is a cross-sectional view thereof.

  As shown in the plan view of FIG. 1A, a plurality of rectangular solar cells 18 are connected in series by lead wires 19 to form a string 15. And what connected the string 15 by the multi-column lead wire 19 and connected the electrodes 16 and 17 to both ends becomes the solar cell panel 10 as a test object. The string 15 in which the solar cells 18 are connected by the lead wires 19 is manufactured by a device called a wiring machine. This is performed while pressing the lead wire 19 against the solar battery cell 18 and heating it. This process affects the connection of the lead wire 19 and the solar battery cell. If the pressing force against the lead wire is too high, it will cause a crack in the solar cell, and if it is too small, it will cause a connection failure.

  The solar cell panel 10 is manufactured as follows. First, as shown in FIG. 1 (b), a filler 13 is placed on a cover glass 11 serving as a transparent protective layer disposed on the lower side, and a plurality of strings 15 connected in series thereon are connected to a plurality of column lead wires. Are connected to each other, a filler 14 is disposed thereon, and finally a back material 12 made of an opaque material is disposed. As the fillers 13 and 14, EVA resin (ethylene vinyl acetate) is used. Thereafter, the component members laminated as described above are pressed in a state of being heated in a vacuum by a laminating apparatus, whereby the EVA resin is melted and cross-linked to be laminated.

  The solar cell to be inspected according to the present invention is not limited to the solar cell panel 10 described above, but only one solar cell 18 or a string 15 in which a plurality of solar cells 18 are linearly connected. Also included. Moreover, it can be set as an inspection object in any state before and after the laminating process. However, a product in the form of a solar cell panel is most desirable in order to obtain the effect of determining the quality of the solar cell aimed at in the present invention and elucidating the cause of the quality deterioration of the solar cell.

  FIG. 2 is a plan view of one solar battery cell 18 as viewed from the light receiving surface. In the solar battery cell 18, a bus bar 18 a which is an electrode for taking out electricity is printed on the surface of a thin plate-like silicon semiconductor. In addition, a fine conductor called a finger 18b is printed on the surface of the silicon semiconductor in a direction perpendicular to the bus bar in order to efficiently collect current in the bus bar.

<2> Solar cell production process The solar cell production process includes a pre-process for processing silicon from an ingot to produce solar cells, and a solar cell product through processes such as attaching lead wires to the solar cells. It is divided into the following processes. In general, the pre-process and the post-process are performed at different locations.

FIG. 3 is a diagram showing a post-process of solar cell production, and the post-process will be described with reference to FIG.
First, a solar cell and a lead wire are connected using a wiring machine to produce a string. A string in which a plurality of strings are connected is placed on a glass with a sealing material placed thereon, and a sealing material and a backsheet are laid up on the sealing material. Then, it progresses to a lamination process and is processed into a solar cell panel. Then, after trimming, a terminal box is attached to the electrode of the solar cell module. Then, the production process is completed when the frame is attached after sealing to prevent the entry of moisture and the like from the outside. Further, after the final inspection, it is shipped as a finished product.

  In the present invention, when the state of the solar cell does not match the preset performance at the time of the final inspection, the manufacturing conditions of the production process are reviewed, and the reviewed production process is applied again to the production process and the solar cell Production is carried out again. The review of the manufacturing conditions is repeatedly performed until the performance of the produced solar cell matches the preset performance. As a result, even if the best production method of a solar cell varies depending on the size of the solar cell, the material of the part to be used, the type of machine used, etc., the manufacturing conditions that best suit the production of the solar cell are selected. Can be obtained quickly.

  On the other hand, when the performance of a solar cell manufactured under a certain manufacturing condition matches a preset performance, the current manufacturing condition is determined as a condition compatible with the current solar cell production. The determined manufacturing condition is registered as the current manufacturing condition for producing the solar cell.

  Solar cells produced under the manufacturing conditions are shipped with numbers. Here, the number is set as a number corresponding to the manufacturing conditions of the production process of the solar cell. Various information such as the size of the solar cell can be given together with the manufacturing conditions. It is sufficient if the above numbers and manufacturing conditions correspond to each other. Later, each solar cell corresponds to a solar cell and its manufacturing conditions, and the solar cell is utilized by statistical analysis of the corresponding information. The cause of deterioration over time can be grasped. Accordingly, it is possible to track the history of a solar cell that has been used for a long time, and it becomes possible to elucidate the cause of quality deterioration and to identify the cause process of quality deterioration.

  The wiring machine and the laminating apparatus are processes that have the most influence on the life and quality of solar cells, and the inspection method of the present invention is not only inspected in the final process of the post-process, but also performed anywhere after the laminating process. Also good. For example, an inspection process may be provided as any one of the production processes after the lamination process.

<3> Solar Cell Inspection Method FIG. 4 is a diagram showing the solar cell inspection process in detail. First, the solar cell inspection method according to the embodiment includes a thermo imaging inspection method, an EL inspection method, and a Raman spectroscopic inspection method. The three inspection devices for each inspection are described in Patent Document 4 filed on April 9, 2010 by the present applicant, and thus the description thereof is omitted.

  The solar cell that has completed at least the laminating process is carried into a solar cell inspection device (S1), and then an electric current is applied to the inspection device to start the inspection (S2). The inspection is divided into three inspections, and a thermo inspection (S3), an EL inspection (S4), and a Raman spectroscopic inspection (S5) are performed.

  First, the thermography inspection will be described. The camera shutter is compensated so as not to depend on the brightness of the image (S31), and shooting is performed (S32). Investigate the presence or absence of fever spots in the captured images. When there is no heat generation spot and heat is generated uniformly, it means that there is no defective connection part of the wiring. However, when heat generation spots are confirmed in the image, there is a defective connection portion of the wiring, and the heat generation portion spreads due to power generation during use, which adversely affects the life of the solar cell. As described above, the exothermic spots are confirmed (S35), and if there are many exothermic spots, the production process is changed and the production process is performed again. When there are many heat spots, a characteristic value such as the area of the heat spot can be set as a threshold value. In the case of thermography inspection, the desired manufacturing condition or the threshold value of the judgment can be changed depending on the size of the solar cell, the material of the specific component used, the type of manufacturing equipment used, etc. If the characteristic value exceeds a certain threshold, it is better to review the conditions of the production process.

  The EL imaging inspection will be described. Light is emitted by the EL action due to the current applied to the solar cell (S41). The emitted light is photographed to inspect the presence or absence of defects (finger disconnection, dark area, crack) in the solar cell (S43). If there are cells with many finger breaks, the power generation capacity may be accelerated, and if there are cracks or dark areas (including chips), the cracks or dark areas may expand due to daily expansion / contraction. There is. As described above, the EL emission light is photographed and judged, and if all of the conditions of no finger disconnection, no crack, and no dark area are not satisfied, the manufacturing conditions are reviewed and changed (S44). Repeat the production process under certain conditions. In the case of EL imaging inspection, desirable manufacturing conditions or criteria for judgment vary depending on the size of the solar cell, the material of the component used specifically, the type of manufacturing equipment used, etc., but there are finger breaks, cracks, and dark areas. If it exceeds a certain level, it is recommended to review the production process conditions. As a method for determining finger breakage, cracks, and dark areas, the method described in Patent Document 5 can be used, and detailed description thereof is omitted.

  The Raman spectroscopic inspection will be described. When a spectrum is obtained by irradiating a laser beam having a known wavelength to the measurement unit and scattering the obtained light to obtain a spectrum, the focus is adjusted to a focal position at which the spectrum intensity indicating the silicon structure is maximized. The Raman spectroscopic measurement is performed by this method (S51), and the peak intensity and half width are calculated (S52). If the half width is narrow, it is judged that the crystallinity of silicon is good, but if it is wide, it is judged that the crystallinity is bad. If the crystallinity is good, the power generation performance is high, and if the crystallinity is bad, the power generation performance tends to be low. If this index is used, the quality of power generation can be evaluated by looking at the crystallinity.

  As a result of Raman spectroscopic inspection, the value of the coordinate in the height direction (hereinafter abbreviated as Z-axis) of the focal position where the spectral intensity is the maximum is compared. Indicates not. When the laminate of the filler and the cell is heated and pressed by the laminating apparatus, the cell position is kept constant if the filler is uniformly melted and the appropriate pressure condition can be maintained. However, if the processing conditions are poor, cell cracks and microcracks occur, or if the melt flow of the filler becomes non-uniform, the cell position will shift. If the cell position changes extremely, it is necessary to change the conditions of the production process (S53).

A method for reviewing the conditions of the production process after thermographic inspection, EL inspection, and Raman spectroscopic inspection have been performed will be described with reference to FIG.
FIG. 5 is a diagram showing the correlation between the inspection result of the EL imaging inspection and the inspection result of the thermo imaging inspection, and the horizontal axis increases as the result of the thermo imaging inspection increases (as it goes to the right), and there is no heating spot and the wiring connection portion The vertical axis indicates the better state as the result of the EL imaging inspection becomes larger (as it goes up), and there are no defects such as cell cracks and microcracks, and the solar cell state is better. Then, it is determined that both the vertical and horizontal axes should be increased. In most production processes, there is a trade-off between EL imaging inspection and thermo imaging inspection. For example, in the case of a wiring machine, the wiring connection portion improves as the pressing force of the lead wire increases. However, when the pressing force increases, there is a high possibility that a captured image of EL emitted light becomes dark due to a defect in the cell.

FIG. 6 is a diagram showing a correlation between the inspection result of the EL imaging inspection and the Raman spectroscopic inspection apparatus. The larger the horizontal axis is as a result of the EL imaging inspection (the more toward the right), the fewer defects such as cell cracks and microcracks. The solar cell is in good condition, and the vertical axis indicates that there is no cell misalignment as the Z-axis misalignment value obtained as a result of Raman inspection becomes smaller (upward).
Here, as a method for evaluating the deviation of the cell position, for example, there is the following method. In other words, when the distance from the glass of the cell at the four corners of the solar cell module and the glass of the cell at the center is measured, This indicates that the laminating conditions are inappropriate.
It is judged that the larger the vertical and horizontal axes, the better. However, most production processes show a trade-off relationship between EL imaging inspection and Raman inspection. By the way, in the case of a laminating apparatus, if the laminating apparatus is in an appropriate condition, the cell position is constant, the bubbles of EVA resin are eliminated, and the state of the solar cell without defects such as cell cracks and micro cracks by EL imaging inspection is good. Become. However, when the pressurization condition is extremely inappropriate, cell cracks occur. When the pressurization condition is inappropriate, cell cracks do not occur, but the cell position shifts. In this case, it is appropriate to change the manufacturing conditions by adjusting the pressurizing conditions of the laminating apparatus so that no bubbles are observed and no cell cracking or cell displacement.

  FIG. 7 is a diagram for explaining aged deterioration of a solar cell, in which the horizontal axis indicates the number of years of use and the vertical axis indicates the amount of power generation. As shown in FIG. 7, an ideal solar cell is such that the amount of power generation does not change even when the number of years of use increases. However, the amount of power generation gradually decreases as time passes. It is presumed that the degradation pattern 1 in which the power generation amount gradually decreases with the passage of time is due to micro unit defects such as silicon electrode material and silicon crystal structure and macro unit defects such as wiring connection. Degradation pattern 2 in which the amount of power generation decreases rapidly in the period of 15 to 20 years after the start of use is due to the corrosion and corrosion caused by moisture intrusion into the solar cell in accordance with the defects of micro units and defects of macro units. Presumed to be the result of overlapping disconnections.

  Furthermore, by applying the inspection method of the present invention with reference to such a power generation failure deterioration pattern, it becomes possible to specify an unsuitable process for the production process of the solar cell to be inspected. For example, in the case of the degradation pattern 2, it can be determined that there is a problem in the peripheral sealing process of the solar cell in FIG. Based on this, it is possible to review the conditions of the peripheral sealing process. If a statistical analysis is performed while comparing the deterioration pattern and its production conditions, the manufacturing conditions that cause a certain deterioration can be specified. By utilizing this, traceability analysis can be performed, manufacturing conditions can be improved, and a long life without any malfunction of the solar cell can be realized.

10 Solar panel 11 Cover glass (transparent protective layer)
12 Back material 13, 14 Filler 15 String 16, 17 Electrode 18 Solar cell 19 Lead wire 18a Bus bar 18b Finger

Claims (4)

A production process for producing solar cells under one manufacturing condition;
An inspection process for inspecting the solar cell produced in the production process;
A determination step of determining whether or not the state of the solar cell obtained by the result of the inspection step matches a preset performance of the solar cell;
If the state of the solar cell does not match the preset performance of the solar cell, the one manufacturing condition of the production process is changed, and the re-determination step of performing the production step, the inspection step, and the determination step again. ,
When the state of the solar cell matches a preset performance of the solar cell, a production condition determining step for determining the one manufacturing condition as a condition that matches the production process;
I have a,
The inspection step includes a thermo imaging inspection, an EL imaging inspection, and a Raman spectroscopic inspection. The solar cell inspection method according to claim 1, wherein at least two inspection results are used to review one manufacturing condition in the thermo imaging inspection, the EL imaging inspection, and the Raman spectroscopic inspection. . Inspecting a solar cell according to claim 1 or 2, characterized in that contained numbering applying a number solar cells produced after the production condition determination process. The inspection process inspecting a solar cell according to any one of claims 1 to 3, characterized in that it is provided after the lamination step in the production process.

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