JP3762013B2 - Manufacturing method of integrated thin film photoelectric conversion device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing an integrated thin film photoelectric conversion device, and more particularly to a water washing step after the photoelectric conversion device is in a state where it can generate photovoltaic power.
[0002]
[Prior art]
In recent years, solar cells, which are photoelectric conversion devices that directly convert solar energy into electrical energy, have been put into practical use. Crystalline solar cells using single crystal silicon, polycrystalline silicon, etc. It has already been put into practical use as a solar cell for use. On the other hand, amorphous silicon-based thin-film solar cells are attracting attention as low-cost solar cells because they can be produced directly on an insulating substrate and require a small amount of raw materials for their production and large-area integrated solar cells. ing. However, amorphous thin-film solar cells are still in the development stage for outdoor use, and research and development are being carried out to develop them for outdoor use based on the results of power supply applications for consumer devices such as calculators that are already in widespread use. It is being advanced.
[0003]
In the manufacture of a thin film solar cell, a desired structure is formed by a manufacturing process including an appropriate repetition or combination of a thin film deposition step by a CVD method or a sputtering method and a patterning step by a laser scribing method or the like. Usually, an integrated structure in which a plurality of photoelectric conversion cells are electrically connected in series on a single insulating substrate is adopted. For example, a power solar cell for outdoor use exceeds 0.4 m × 0.4 m. A large area substrate is used.
[0004]
FIG. 5 is a schematic cross-sectional view showing the structure of such an integrated thin film solar cell. In each drawing of the present application, the dimensional relationship is appropriately changed for clarity of the drawing and does not reflect the actual dimensional relationship, while the same reference numerals represent the same parts. In the integrated thin film solar cell 1 of FIG. 5, a first electrode layer 3, a semiconductor photoelectric conversion layer 5 made of amorphous silicon, and a second electrode layer 7 are sequentially stacked on an insulating substrate 2, and a semiconductor is formed by patterning. The photoelectric conversion cells adjacent to each other on the left and right sides are electrically connected in series via the connection opening groove 6 provided in the layer 5. As the first electrode layer 3, a transparent conductive film such as tin oxide (SnO ₂ ), zinc oxide (ZnO), indium tin oxide (ITO) is generally used, and as the second electrode layer 7, silver (Ag) is used. Metal films such as aluminum (Al) and chromium (Cr) are used.
[0005]
The integrated thin film solar cell 1 having the structure shown in FIG. 5 is generally manufactured by the following method. First, a transparent conductive film such as SnO ₂ , ZnO, or ITO is deposited on the glass substrate 2 as the first electrode layer 3, and the first electrode layer 3 is separated into a plurality of regions corresponding to a plurality of photoelectric conversion cells. In addition, the lower electrode separation groove 4 is formed by a laser scribing method. That is, these lower electrode separation grooves 4 extend linearly in a direction perpendicular to the paper surface of FIG. Then, an amorphous silicon semiconductor photoelectric conversion layer 5 including a pin junction is deposited using a plasma CVD method so as to cover the first electrode layer 3 separated into a plurality of regions. In the semiconductor layer 5, connection opening grooves 6 for electrically connecting the photoelectric conversion cells adjacent to the left and right in series are formed by a laser scribing method. These connection opening grooves 6 also extend linearly in a direction perpendicular to the paper surface of FIG. Subsequently, a single layer or multiple layers of a metal film such as Ag, Al, Cr, etc. is deposited as the second electrode layer 7 so as to fill the connection grooves 6 and cover the semiconductor layer 5. Similar to the case of the first electrode layer 3, the upper electrode separation groove 8 is formed by a laser scribing method so as to separate the second electrode layer 7 into a plurality of regions corresponding to the plurality of photoelectric conversion cells. These upper electrode separation grooves 8 also extend linearly in a direction perpendicular to the paper surface of FIG. 5 and preferably have a depth reaching the first electrode layer 5. In this way, an integrated thin film solar cell as shown in FIG. 5 is completed.
[0006]
In general, in the manufacture of an integrated thin film solar cell as shown in FIG. 5, when forming the transparent electrode 3 on the light incident side or the back metal electrode 7 on the opposite side, the end face or the bottom face of the insulating substrate 2. A transparent conductive material or metal material wraps around and adheres. For this reason, even if the individual photoelectric conversion cells to be integrated are separated from each other on the upper surface of the substrate, they are electrically connected to each other through the transparent conductive material or metal material attached to the substrate end surface or the lower surface of the substrate. The output characteristics of the are reduced.
[0007]
In order to improve this problem, as shown in the plan view of FIG. 6, the cell integration region including the back surface metal electrode 7 and the upper separation groove 8 of the integrated thin film solar cell and the peripheral region 10 along the periphery thereof. A peripheral separation groove 9 as an insulating line that electrically isolates and from each other is produced by a photolithography method or the like. That is, by forming the peripheral separation groove 9, a short circuit between the photoelectric conversion cells due to the transparent conductive material or metal material adhering to the substrate end surface or the substrate lower surface is prevented, and the output characteristics, insulation characteristics, and Withstand voltage characteristics are improved. The peripheral separation groove formed by photolithography generally has a width in the range of 0.1 mm to 1.0 mm, and the cell integration region and the peripheral region 10 are electrically separated by this scribe line. In FIG. 6, 12 stages of cells connected in series are illustrated for the sake of clarity, but in actuality, more stages of cells can be formed.
[0008]
After such a peripheral separation groove 9 is formed, before the back surface metal electrode 7 of the integrated solar cell is sealed, water cleaning is performed for the purpose of cleaning the integrated solar cell. During such water washing, the integrated solar cell generates light by receiving light in the manufacturing process chamber and generates electromotive force. Here, the integrated solar cell for practical use has, for example, 63 cell integration stages, and has an open circuit voltage of about 0.85 V per stage. That is, the potential difference between the positive electrode side and the negative electrode side of such an integrated solar cell is about 53V.
[0009]
In the state where there is a potential difference of about 53 V between the positive and negative electrodes in this way, as shown in FIG. 7, if the water droplet 11 adheres to any cell so as to cover a part of the insulating line 9a in the cleaning process. The peripheral region 10 is short-circuited with the cell of the stage to which the water droplet 11 is attached, and becomes equal to the potential of the cell of the stage (In FIG. 7, the width of the peripheral separation groove 9a is enlarged for clarity of the drawing. Has been shown). As a result, the cell has a higher potential than the peripheral region 10 between the cell on the positive electrode side of the water droplet 11 and the peripheral region 10. On the other hand, between the cell on the negative electrode side of the water droplet 11 and the peripheral region 10, the peripheral region 10 has a higher potential than the cell.
[0010]
Subsequently, if another new water droplet 12 or 13 adheres so as to cover the insulating line 9a as shown in FIG. 8 in a state where there is such a potential difference, there is a potential difference in these water droplets 12 and 13. Therefore, for example, silver migration occurs from the silver metal electrode layer from the low potential side to the high potential side between the peripheral region 10 and the cell, and the dendritic silver crystals 14 and 15 grow. The rate at which such silver migration occurs is such that when an ion path such as a water droplet is formed, if the electric field strength is several hundred V / mm, the growth rate is a large value close to 0.1 mm / second. Become. In this way, metal migration occurs from the metal electrode layer in the cleaning process, and insulation failure occurs between the cell integration region and the peripheral region 10.
[0011]
In the actual water washing step, the integrated solar cell 1 is transported into the cleaning chamber by a conveyor, so that when water washing is started, splashes of water from the front adhere to the integrated solar cells. Then, as described with reference to FIG. 8, the water droplets due to such splashes cause metal ion migration in the peripheral separation groove 9a. Moreover, since the growth rate of the dendritic metal crystal due to this migration is sufficiently high, the potential difference between the cell and the peripheral portion 10 is reduced before the entire integrated solar cell is covered with water and all the cells have the same potential. As a result, a metal dendritic short-circuit path is formed by metal migration. In other words, the cell integrated region and the peripheral region are made conductive by ion migration from the metal electrode layer, which causes the output characteristics, insulating characteristics, and withstand voltage characteristics of the integrated solar cell to deteriorate.
[0012]
[Problems to be solved by the invention]
In view of the problems of the prior art as described above, the present invention enables a cleaning process that does not cause a short circuit due to ion migration in the peripheral separation groove of the integrated thin film photoelectric conversion device, thereby providing output characteristics and insulation. An object of the present invention is to provide a method for manufacturing an integrated thin film photoelectric conversion device having excellent characteristics and withstand voltage characteristics.
[0013]
[Means for Solving the Problems]
According to one aspect of the present invention, there is provided a method of manufacturing an integrated thin film photoelectric conversion device including a stacked body including a first electrode layer, a semiconductor photoelectric conversion layer, and a second electrode layer sequentially stacked on an insulating substrate. At least one of the first electrode layer and the second electrode layer includes a metal layer, and the stacked body is separated into a photoelectric conversion cell integrated region and a peripheral region by a peripheral separation groove, and the cell integrated region forms a plurality of photoelectric conversion cells. And a method for manufacturing an integrated thin film photoelectric conversion device in which at least some of the plurality of cells are electrically connected in series, and the plurality of cells connected in series in the water washing step of the photoelectric conversion device The positive electrode and negative electrode cells of the cells or the cells close to them and the peripheral region are not completely separated by the peripheral separation groove but are electrically short-circuited. It is characterized by removing the electrical short circuit by forming a complete peripheral isolation trench in between the cells or cell and the peripheral region close to their negative.
[0014]
According to another aspect of the present invention, there is provided a method for manufacturing an integrated thin-film photoelectric conversion device, in the water washing step of the photoelectric conversion device, the positive electrode and negative electrode cells of a plurality of cells connected in series or cells close to them The region is electrically short-circuited by a conductor, and the electrically short-circuited conductor is removed after the water washing step is completed.
[0015]
The method for manufacturing an integrated thin film photoelectric conversion device according to still another aspect of the present invention is characterized in that in the water washing step of the photoelectric conversion device, water washing is performed in a water washing chamber shielded from light.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
In the following, various examples corresponding to various embodiments of the present invention will be described.
[0018]
Example 1
First, as in the case of FIG. 5, the transparent electrode layer 3, the semiconductor photoelectric conversion layer 5, and the back metal electrode layer 7 were formed on the substrate 2. At this time, a glass substrate having an area of 910 mm × 455 mm and a thickness of 4 mm was used as the substrate 2. A transparent conductive film layer 3 was formed on the glass substrate 2 by a thermal CVD method. The transparent conductive film layer 3 was divided into a plurality of strip-shaped regions by irradiating the second harmonic of a YAG laser having a wavelength of 0.53 μm from above to form the scribe line 4.
[0019]
Next, a first mixed gas containing monosilane, methane and diborane, monosilane and hydrogen are contained under a substrate temperature of 200 ° C. and a reaction pressure of 0.5 to 1.0 Torr so as to cover the transparent electrode layer 3. The p-type, i-type and n-type amorphous semiconductors are obtained by decomposing the second mixed gas and further the third mixed gas containing monosilane, hydrogen and phosphine in this order in a capacitively coupled glow discharge decomposition apparatus. The layers were laminated. In the pin semiconductor layer 5, the connection groove 6 was formed by irradiating the laser beam through the glass substrate 2 so as not to damage the transparent electrode 3.
[0020]
Subsequently, a 300 nm thick silver layer was formed as the metal layer 7 by sputtering. An upper electrode separation groove 8 was formed in the silver layer 7 and the semiconductor photoelectric conversion layer 5 by using a photolithography method. Thus, an integrated amorphous silicon solar cell in which a plurality of photoelectric conversion cells are connected in series on the substrate 2 was formed.
[0021]
Thereafter, as shown in FIG. 1, in order to separate the cell integration region and the peripheral region 10, peripheral isolation grooves 9 and 9a were formed by photolithography. However, the peripheral edge separation groove 9a is partially interrupted so that the positive electrode end cell and the negative electrode end side cell and the peripheral region 10 have the same potential. That is, the cells on the positive electrode end side and the negative electrode end side are continuous with the peripheral region 10 by the minute region 10a where the peripheral separation groove 9a is interrupted.
[0022]
As a result, the cell integration region and the peripheral region 10 are electrically connected, and the cells in each stage between the two short-circuit regions 10a and the peripheral region 10 have the same potential. Thereafter, positive and negative output extraction electrodes were provided at both ends of the integrated solar cell. As these extraction electrodes, copper foil plated with solder was used, and adhesion to the glass substrate was performed by an ultrasonic soldering method.
[0023]
Thus, water cleaning was performed for the purpose of cleaning the surface of the back metal electrode 7 with the minute short-circuit region 10a left. After washing with water, drying is performed, and the micro short-circuit region 10a that has electrically connected the peripheral region 10 and the positive and negative electrodes of the cell integration region is newly cut using photolithography or laser, and then the output of the integrated thin-film solar cell Properties and insulation properties were measured.
[0024]
Using the method including the water washing step of Example 1 described above, 28 integrated thin film solar cell samples were produced. On the other hand, as a comparative example, 54 samples manufactured through the water washing process under the same conditions as in Example 1 except that the minute short-circuit region 10a as shown in FIG. 1 was not left were produced. . When the output characteristics and the insulation characteristics were compared in the integrated thin film solar cells according to Example 1 and the comparative example, there was no significant difference in the output characteristics. However, regarding the insulation characteristics, the sample according to Example 1 had a resistance of 1 MΩ or more between the cell integration region and the peripheral region, and no insulation failure was observed. Forty-three sheets had a low resistance of less than 1 MΩ, and insulation failure was observed. Moreover, in any of the samples of the comparative examples in which the insulation failure was observed, the insulation failure was caused by the silver crystal pass by migration.
[0025]
(Example 2)
The integrated thin film solar cell in Example 2 was also produced basically in the same manner as in Example 1. However, the integrated solar cell in Example 2 does not include the minute short-circuit region 10a left as in Example 1, and the peripheral separation groove 9 completely separates the cell integrated region from the peripheral region 10. ing. On the other hand, in Example 2, the lead wire 10b as shown in FIG. 2 was soldered so that the positive electrode side cell, the negative electrode side cell, and the peripheral region had the same potential. In this state, the water washing step was performed in the same manner as in Example 1 and dried, and then these lead wires 10b were removed, and the output characteristics and insulation characteristics of the laminated thin film solar cell were measured. As a result of examining the 50 integrated thin-film solar cells that had undergone the water washing step according to Example 2, the output characteristics were not significantly different from those of the comparative example described above. The solar cell also has a sufficient resistance of 1 MΩ or more between the cell integration region and the peripheral region, and no insulation failure was found.
[0026]
Example 3
FIG. 3 is a schematic cross-sectional view for explaining a water washing step of the integrated thin-film solar cell according to Example 3.
[0027]
The water washing process according to Example 3 is shown in FIG. 6 of the prior art as well as the solar cell in the state shown in FIG. 1 of Example 1 and the solar cell in the state shown in FIG. 2 of Example 2. It can also be preferably used for washing a solar cell in a wet state.
[0028]
The water washing apparatus 20 </ b> A shown in FIG. 3 includes a plurality of water washing chambers 21. A drying chamber 22 is provided following the plurality of washing chambers 21. The drying chamber 22 may be provided with a hot air dryer as represented by an arrow 22a, for example. The integrated thin film solar cell 1 is conveyed by the conveyor 23, passed through the plurality of water washing chambers 21, and then dried in the drying chamber 22. In the washing chamber 21, a washing spray (not shown) from above may be provided, and in addition to this, a washing spray (not shown) from below may be provided. The conveyor 23 may be a mesh or ladder. A curtain 24 made of, for example, a rubber or polymer sheet cut into a strip shape may be provided at the boundary between the water washing chamber 21 and the drying chamber 22.
[0029]
These washing chamber 21 and drying chamber 22 are surrounded by a light shielding guard 25 that blocks light. Therefore, if the integrated thin film solar cell is washed with water in the water washing apparatus as shown in FIG. 3, the photovoltaic cell will not generate photovoltaic power during the washing process, so any of the peripheral separation grooves 9 Even if water droplets partially adhere to the position, there is no potential difference between the cell integration region and the peripheral region, so that a short circuit due to ion migration does not occur.
[0030]
Regarding Example 3, 16 integrated solar cells as shown in FIG. 6 were manufactured under the same manufacturing conditions as in Example 1. These 16 solar cells were subjected to a water washing step as shown in FIG. 3 and then measured for insulation characteristics. However, none of the 16 solar cells caused insulation failure due to the occurrence of ion migration.
[0031]
(Example 4)
FIG. 4 is a schematic cross-sectional view showing a water washing apparatus used in the water washing process according to the fourth embodiment. The water washing apparatus 20B of FIG. 4 is similar to that of FIG. 3, but the light shielding guard 25 is not provided. Instead, an additional fountain nozzle 26 is provided in front of the first flush chamber 21.
[0032]
In the washing step according to FIG. 4 of the fourth embodiment, as in the case of FIG. 3 of the third embodiment, it can be preferably used for the washing of the integrated thin film solar cell according to the prior art as shown in FIG. .
[0033]
In the water washing method as shown in FIG. 4, the fact that the solar cell 1 has been conveyed immediately below the fountain nozzle 26 in the previous stage where the integrated solar cell 1 is conveyed into the first water washing chamber 21 is indicated. Detected by a sensor or the like (not shown), water is jetted from the fountain nozzle 26 at that moment, and the entire region of the peripheral separation groove 9 is instantaneously and simultaneously wetted. That is, even if the integrated solar cell 1 receives light and generates an electromotive force, the entire region of the peripheral separation groove 9 is wetted at the same instant, so the entire cell integrated region and the peripheral region 10 Are instantaneously at the same potential. As a result, since there is no potential difference in the wet peripheral separation groove 9, ion migration does not occur, and the cell integrated region and the peripheral region are not short-circuited by the metal dendrite.
[0034]
Basically, 14 integrated solar cells as shown in FIG. 6 were manufactured under the same manufacturing conditions as in Example 1, and the water washing step as shown in FIG. 4 was performed. No integrated solar cell was found that had an insulation failure due to the occurrence of ion migration.
[0035]
In the above embodiments, an integrated photoelectric conversion device in which a transparent electrode, a semiconductor photoelectric conversion layer, and a metal electrode are sequentially stacked on a transparent insulating substrate has been described. For example, a metal electrode is formed on a stainless steel substrate having an insulating film. Needless to say, the manufacturing method of the present invention can also be applied to an integrated photoelectric conversion device in which a semiconductor photoelectric conversion layer and a transparent electrode are sequentially laminated.
[0036]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent an insulation failure due to metal ion migration in the washing process of an integrated thin film solar cell having a peripheral separation groove, and to manufacture an integrated thin film solar cell free from current leakage. A method of obtaining can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing a state of an integrated thin film solar cell in a water washing process according to a first embodiment of the present invention.
FIG. 2 is a schematic plan view showing a state of an integrated thin film solar cell in a water washing process according to a second embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view showing an example of a washing apparatus that can be used in a washing process according to a third embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view showing a water washing apparatus that can be used in a water washing process according to a fourth embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view showing the structure of an integrated thin film photoelectric conversion device.
FIG. 6 is a schematic plan view showing an integrated thin film solar cell according to the prior art.
FIG. 7 is a schematic plan view showing a state in which local water droplets are attached on a peripheral separation groove of an integrated thin film solar cell according to the prior art.
FIG. 8 is a schematic plan view showing a state in which a metal dendrite has grown in a peripheral separation groove of an integrated thin film solar cell according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Integrated thin-film solar cell 2 Transparent insulating substrate 3 Transparent electrode 4 Lower electrode separation groove 5 Semiconductor photoelectric conversion layer 6 Connection opening groove 7 Back surface metal electrode 8 Upper electrode separation groove 9, 9a Perimeter separation groove 10 Perimeter region 10a Micro short-circuit area 11, 12, 13 Water drop 14, 15 Metal dendrites 20A, 20B Flushing device 21 Flushing chamber 22 Drying chamber 22a Hot air dryer 23 Conveyor 24 Rubber or polymer strip curtain 25 Light shielding guard 26 Fountain nozzle

Claims (3)

A stack including a first electrode layer, a semiconductor photoelectric conversion layer, and a second electrode layer sequentially stacked on an insulating substrate, wherein at least one of the first and second electrode layers includes a metal layer; The stacked body is separated into a photoelectric conversion cell integrated region and a peripheral region by a peripheral separation groove, and the cell integrated region is divided so as to form a plurality of photoelectric conversion cells, and at least a part of the plurality of cells is formed. A method of manufacturing an integrated thin film photoelectric conversion device electrically connected in series,
In the water washing step of the photoelectric conversion device, a positive electrode and a negative electrode cell among the plurality of cells connected in series or a cell close thereto and the peripheral region are not completely separated by the peripheral separation groove. It is shorted electrically,
An integrated thin film characterized in that the electrical short circuit is removed by forming a complete separation groove between the positive electrode and negative electrode cells or cells close thereto and the peripheral region after the water washing step is completed. A method for manufacturing a photoelectric conversion device. A stack including a first electrode layer, a semiconductor photoelectric conversion layer, and a second electrode layer sequentially stacked on an insulating substrate, wherein at least one of the first and second electrode layers includes a metal layer; The stacked body is separated into a photoelectric conversion cell integrated region and a peripheral region by a peripheral separation groove, and the cell integrated region is divided so as to form a plurality of photoelectric conversion cells, and at least a part of the plurality of cells is formed. A method of manufacturing an integrated thin film photoelectric conversion device electrically connected in series,
In the water washing step of the photoelectric conversion device, a positive electrode and a negative electrode cell among the plurality of cells connected in series or a cell close thereto and the peripheral region are electrically short-circuited by a conductor,
A method of manufacturing an integrated thin film photoelectric conversion device, wherein the conductor to be short-circuited is removed after completion of the water washing step. A stack including a first electrode layer, a semiconductor photoelectric conversion layer, and a second electrode layer sequentially stacked on an insulating substrate, wherein at least one of the first and second electrode layers includes a metal layer; The stacked body is separated into a photoelectric conversion cell integrated region and a peripheral region by a peripheral separation groove, and the cell integrated region is divided so as to form a plurality of photoelectric conversion cells, and at least a part of the plurality of cells is formed. A method of manufacturing an integrated thin film photoelectric conversion device electrically connected in series,
The method of manufacturing an integrated thin film photoelectric conversion device, wherein in the water washing step of the photoelectric conversion device, water washing is performed in a water washing chamber shielded from light.

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