JP2009135544A - Thin film solar battery, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film solar battery for which the need of transparent electrode layer work accompanying the heat distortion of a film substrate is eliminated and a manufacturing cost is reduced, and to provide a manufacturing method thereof. <P>SOLUTION: In the SCAF type thin film solar battery, a cell end under electrode process line 10a for patterning is provided on the outer side end along the serial connection direction of a photoelectric conversion part, and a photoelectric conversion layer 4 and a transparent electrode layer 5 are provided on the outer side of the cell end under electrode process line 10a extending to the side end of the photoelectric conversion part. Further, for a connection electrode layer, the region of a prescribed dimension width from the side end is removed from the back surface of the substrate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thin film solar cell in which a plurality of unit cells are connected in series on the surface of a flexible substrate having electrical insulation, and a method for manufacturing the same.

An amorphous semiconductor film such as amorphous silicon formed by glow discharge decomposition of a source gas is easily grown because of vapor phase growth, and is expected as a photoelectric conversion film for a low-cost solar cell. Such a thin film solar cell is provided with a transparent electrode such as a SnO ₂ film or a ZnO film on the side on which sunlight is incident. However, since such a transparent electrode has a large sheet resistance, there is a problem that a power loss due to a current flowing through the transparent electrode increases.
Therefore, conventionally, the solar cell is divided into a plurality of solar cells (unit cells), and a series connection structure is employed in which the divided unit cells are electrically connected to adjacent unit cells. On the other hand, in the thin film solar cell described in Patent Document 1, a hole is formed in the insulating substrate on the light incident side, and the transparent electrode layer is connected to the connection electrode layer on the back surface of the substrate using this hole. The distance of the path of the current flowing through the transparent electrode layer having a high sheet resistance is shortened, so that it can be configured as a low voltage, high current type without being divided into unit solar cells with limited dimensions. As a result, it was possible to obtain a thin-film unit solar cell with a low Joule loss and an increased effective power generation area by reducing the dead space.
Further, an exposed region of the connection electrode layer under the photoelectric conversion layer is formed in a part of the unit solar cell, and the separated connection electrode layer connected to the conductor penetrating the substrate is connected to the adjacent unit solar cell. By connecting to the electrode layer, a series connection structure can be easily formed. The thin film solar cell having such a structure is called a SCAF (Series Connection through Apertures on Film) type thin film solar cell, and is formed by forming an electrode layer and a photoelectric conversion layer, patterning each layer, and a combination procedure thereof. . An example of the configuration and manufacturing method of the thin film solar cell is described in, for example, Patent Document 2 filed by the applicant of the present application.

FIG. 3 is a perspective view showing a simplified configuration of the SCAF type thin film solar cell for easy understanding of the structure. In FIG. 3, the unit photoelectric conversion element 62 formed on the front 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.
The 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.

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, the 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.
Since the third electrode layer and the fourth electrode layer are electrically at the same potential, they may be treated as a single connection electrode layer for convenience of explanation.
Furthermore, Patent Document 3 discloses a configuration aimed at increasing the effective area ratio of power generation, which is different from the configuration of the SCAF type thin film solar cell. That is, Patent Document 3 states that “a lower electrode layer connected through a through hole (referred to as a back electrode layer in Patent Document 3) and a connection electrode layer are formed, and then an amorphous semiconductor layer is formed on the lower electrode layer. In this case, the extension of the amorphous semiconductor layer extends to the periphery of the through hole on the back surface of the substrate, and even if the transparent electrode layer is formed in the through hole by this extended amorphous semiconductor layer, the connection electrode layer is short-circuited. Thus, a thin film solar cell is disclosed in which the entire area of the transparent electrode layer can be prevented and the effective area ratio of power generation is increased (refer to Patent Document 3 for details).

FIG. 2 is slightly different from that disclosed in Patent Document 3, but the conventional improved SCAF in which the effective area ratio of power generation is increased by adopting a structure in which the amorphous semiconductor layer is insulated by an extension portion. An example of a structure of a thin film solar cell is shown. 2A is a plan view seen from the light-receiving surface side of the thin-film solar cell, FIG. 2B is a plan view seen from the non-light-receiving surface side, and FIG. 2C is a cross-sectional view taken along the line aa in FIG. 4 (d) is a cross-sectional view taken along the line bb in FIG. 2 (a).
The thin-film solar cell shown in FIG. 2 has a configuration in which the effective area ratio of power generation is increased by extending the photoelectric conversion layer and the transparent electrode layer to the side end of the photoelectric conversion unit. It is done as follows. For example, the connection hole 7 is formed in the substrate 1 made of a plastic film, the lower electrode layer 2 made of metal is formed on the surface, and the third electrode layer 3 as the connection electrode layer made of metal is formed on the back surface. Open. Therefore, although the extension part of the lower electrode layer 2 and the 3rd electrode layer 3 is formed in the inner wall of the connection hole 7, these electrode layers are not formed in the current collection hole 8. FIG.
Next, laser processing is performed on the lower electrode layer 2 to form a unit electrode lower electrode processing line 9a and a cell end lower electrode processing line 10a. Subsequently, a photoelectric conversion layer 4 made of amorphous silicon (a-Si), amorphous silicon germanium (a-SiGe) or microcrystalline silicon having a pin structure is formed on the lower electrode layer 2 by plasma CVD. At this time, the photoelectric conversion layer 4 is formed by simultaneously wrapping around the current collecting holes 8 and the inner walls and the outer peripheral portions of the connection holes 7 on the back surface of the substrate.

Subsequently, the transparent electrode layer 5 is formed by sputtering. Here, since the wraparound to the back surface of the substrate is less in the transparent electrode layer 5 than in the photoelectric conversion layer 4, the transparent electrode layer 5 is short-circuited with the electrode layer around the connection hole 7 and the current collecting hole 8. Absent. Next, a fourth electrode layer 6 as a connection electrode layer is formed in a state where the periphery of the connection hole 7 is covered with a line mask. Thereby, the transparent electrode layer 5 is connected to the fourth electrode layer 6 through the current collecting holes 8.
Next, the unit electrode transparent electrode processing line is formed so that the processing width is made narrower than the lower electrode processing line 9a between unit cells and the cell end lower electrode processing line 10a from above the transparent electrode layer 5, and these lines are traced. 9b and cell edge transparent electrode processing line 10b are formed. At this time, if the transparent electrode processing line protrudes from the lower electrode processing line, the transparent electrode layer 5 and the lower electrode layer 2 are electrically connected by the photoelectric conversion layer 4 whose surface is alloyed, and leakage occurs. Is required. Finally, laser processing is performed on the connection electrode layer to form the inter-unit cell connection electrode processing line 11 and the cell end connection electrode processing line 12 to complete the series connection structure.

JP-A-6-342924 Japanese Patent Laid-Open No. 10-233517 JP-A-8-186279

By the way, the improved SCAF structure thin film solar cell shown in FIG. 2 has the following problems.
As described above, the transparent electrode layer processing lines between the columns and at the ends need to be processed so as not to protrude and trace the lower electrode layer, and high accuracy is required. Furthermore, since a high-temperature photoelectric conversion layer and transparent electrode layer film forming process with a film forming temperature of 200 to 300 ° C. is inserted between the lower electrode layer processing and the transparent electrode layer processing, thermal deformation of the substrate occurs. Normally, a line processed into a rectangle is distorted into a parallelogram, and the angle at that time is 0 to 0.001 rad. For example, when a 1 m square solar cell is manufactured, the positional displacement due to distortion into a parallelogram is 1 mm at the maximum, which is larger than the lower electrode processing line width of several μm. Therefore, in order to manufacture such a large area solar cell, it is necessary to perform angle correction at the time of processing the transparent electrode layer, the control is complicated, the apparatus cost is increased, and the alignment time is increased, resulting in a decrease in throughput. There was a problem.
An object of the present invention is to solve the above-mentioned problems, that is, the problem of insulation failure accompanying thermal deformation of the substrate. In particular, when a transparent electrode layer processing line is provided, a thin-film solar cell and a method for manufacturing the same that eliminates the need for angle correction at the time of processing the transparent electrode layer due to thermal distortion of the film substrate and reduces the manufacturing cost are provided. It is in.

In order to solve the above-mentioned problem, according to the invention of claim 1, the first electrode layer as the lower electrode layer is formed on the surface of the substrate having electrical insulation without providing the cell edge transparent electrode processing line, photoelectric conversion A photoelectric conversion portion formed by sequentially laminating a layer and a transparent electrode layer (second electrode layer), and a third electrode layer and a fourth electrode layer as connection electrode layers formed on the back surface of the substrate, and the photoelectric conversion The unit and the connection electrode layer are patterned into unit parts while being shifted from each other, and are adjacent to each other by being patterned on the surface through the connection hole and the current collection hole formed in the photoelectric conversion layer forming region. In the thin film solar cell in which the photoelectric conversion portions (unit cells) are electrically connected in series, the first electrode layer is electrically connected to the outer end portion along the serial connection direction of the photoelectric conversion portion by the photoelectric conversion layer. To insulate Cell pattern lower electrode processing line for patterning of the above, and the photoelectric conversion layer and the transparent electrode layer are provided outside the cell end lower electrode processing line, extending to the side end of the photoelectric conversion unit, Furthermore, the connection electrode layer is formed by removing a region having a predetermined width from the side end from the back surface of the substrate (invention of claim 1).
This can solve the problem of insulation failure caused by thermal strain of the film substrate.
In this way, when the cell edge transparent electrode processing line is not provided, the transparent electrode layer and the connection electrode layer are close to each other through the film substrate, so that migration of the electrode may occur during actual use and cause insulation failure. However, in order to avoid this, the connection electrode layer is completely removed from the side end portion as described above. In the case where the fourth electrode layer as the connection electrode layer is formed sufficiently narrower than the third electrode layer as in the example shown in FIG. 2, only the third electrode layer may be removed. .

As an embodiment of the removal processing width, the invention of claim 2 is suitable. That is, in the thin film solar cell according to claim 1, the predetermined dimension width of the region where the connection electrode layer is removed is at least 0.5 mm.
Moreover, as a manufacturing method of the said thin film solar cell, the invention of the following Claim 3 thru | or 4 is preferable. That is, in the method for manufacturing a thin-film solar cell according to claim 1 or 2, the cell end lower electrode processing line is formed by laser processing (invention of claim 3). Furthermore, it is a manufacturing method of the thin film solar cell of any one of the said Claim 1 thru | or 3, Comprising: The area | region where the said connection electrode layer is removed is laser processing, processing by an ultrasonic vibrator, and sandblast processing It is formed by any of the above methods (invention of claim 4). In particular, processing by an ultrasonic vibrator or sandblast is preferable because wide processing can be easily performed.

According to the present invention, as described above, in the SCAF type thin film solar cell, the first electrode layer is electrically insulated by the photoelectric conversion layer at the outer end portion along the serial connection direction of the photoelectric conversion unit. A cell end lower electrode processing line for patterning is provided, and the photoelectric conversion layer and the transparent electrode layer are provided outside the cell end lower electrode processing line so as to extend to the side end of the photoelectric conversion unit. Furthermore, since the connection electrode layer is formed by removing a region having a predetermined width from the side edge from the back surface of the substrate (invention of claim 1),
The problem of insulation failure due to thermal deformation of the substrate can be solved.
The cell end lower electrode processing line is formed by laser processing, and the connection electrode layer is removed by any one of laser processing, processing by an ultrasonic vibrator, and sand blast processing. In the case of the present invention, since the cell edge transparent electrode processing line processing itself is unnecessary, the apparatus cost is reduced and the throughput is improved. Furthermore, weather resistance improves as a result of the suppression of moisture intrusion into the film. As described above, a low-cost and highly reliable solar cell can be provided.

Configuration diagram of a thin film solar cell according to an embodiment of the present invention Structure diagram of thin film solar cell related to conventional improved SCAF configuration The perspective view which shows schematic structure of a SCAF type thin film solar cell The figure which shows the outline of the manufacturing process of a SCAF type thin film solar cell

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of a thin film solar cell according to the first embodiment of the present invention, FIG. 1 (a) is a plan view seen from the light receiving surface side of the thin film solar cell, and FIG. 1 (b) is a non-light receiving surface. FIG. 1C is a sectional view taken along the line aa in FIG. 1A, and FIG. 1D is a sectional view taken along the line bb in FIG. 1A.
In FIG. 1, the same functional members as those in FIG. The basic difference between FIG. 1 and FIG. 2 is that the cell end transparent electrode processing line 10b and the cell end connection electrode processing line 12 are not provided, but a partial region of the third electrode layer 3 (the h portion in FIG. 1). ) Is completely removed to provide the cell end connection electrode layer removal region 12a.
Next, although the manufacturing procedure of the solar cell shown in FIG. 1 partially overlaps with the description of FIG. 2, it will be described below. After forming a connection hole 7 in a substrate 1 made of a heat-resistant plastic film such as polyimide or aramid by punching and forming a lower electrode layer 2 made of metal on the surface and a third electrode layer 3 made of metal on the back surface, Open the current collecting hole 8. Accordingly, the extension portions of the lower electrode 2 and the third electrode layer 3 are formed on the inner wall of the connection hole 7, but these electrode layers are not formed inside the current collection hole 8. Next, laser processing is performed on the lower electrode layer 2 to form a lower electrode processing line 10a between unit cells and a cell end lower electrode processing line 10a while maintaining an orthogonal or arbitrary angle thereto.

Subsequently, the substrate 1 is carried into a stepping roll type film forming apparatus, and the photoelectric conversion layer 4, the transparent electrode layer 5, and the fourth electrode layer 6 are formed. At this time, the photoelectric conversion layer 4 is made of amorphous silicon (a-Si) having a pin structure, amorphous silicon germanium (a-SiGe), or microcrystalline silicon, and is formed at a substrate temperature of 200 to 300 ° C. by plasma CVD. The transparent electrode layer 5 is made of ITO, SnO ₂ , ZnO or the like, and the fourth electrode layer 6 is made of Ni, Cu or the like, and each is formed at a temperature of 150 to 250 ° C. by sputtering or vapor deposition. . At this time, at the same time, the photoelectric conversion layer 4 is formed so as to go around the back surface of the substrate as described above. Since the transparent electrode layer 5 has less wraparound to the back surface than the photoelectric conversion layer 4, the transparent electrode layer 5 is not short-circuited with the electrode layer around the connection hole 7 and the current collection hole 8. The fourth electrode layer 6 is formed in a state where the periphery of the connection hole 7 is covered with a line mask. Thereby, the transparent electrode layer 5 is connected to the fourth electrode layer 6 through the current collecting holes 8.
Next, image recognition is performed for each lower electrode processing line 9a between unit cells, and a transparent electrode processing line 9b between unit cells is formed so as to be traced.
Since the transparent electrode layer 5 and the third electrode layer 3 as the connection electrode layer are close to each other through the thickness of the film substrate 1, there is a possibility that migration of the electrode occurs in actual use and causes insulation failure. In order to avoid this, a partial region of the third electrode layer 3 at least 0.5 mm or more from the end (the h portion in FIG. 1) is completely removed. As this removal method, it is preferable to perform a wide processing of 0.5 mm or more, for example, 1 mm or more by laser, ultrasonic vibrator or sandblasting, and finally cut the processing line.
According to this embodiment, since the lower electrode processing line near the end of the cell surface is covered with the a-Si film, there is an effect of improving weather resistance by blocking the ingress of moisture into the film substrate. .

  1: substrate, 2: first electrode layer (lower electrode layer), 3: third electrode layer, 4: photoelectric conversion layer, 5: second electrode layer (transparent electrode layer), 6: fourth electrode layer, 7: Connection hole, 8: Current collecting hole, 9a: Lower electrode processing line between unit cells, 9b: Transparent electrode processing line between unit cells, 10a: Cell end lower electrode processing line, 10b: Cell end transparent electrode processing line, 11: Unit cell connection electrode processing line, 12: cell end connection electrode processing line, 12a: cell end connection electrode layer removal region.

Claims (4)

A photoelectric conversion portion formed by sequentially laminating a first electrode layer, a photoelectric conversion layer, and a transparent electrode layer (second electrode layer) as a lower electrode layer on the surface of an electrically insulating substrate, and formed on the back surface of the substrate A third electrode layer and a fourth electrode layer as connection electrode layers are provided, and the photoelectric conversion portion and the connection electrode layer are patterned into unit portions while being shifted from each other, and formed in the photoelectric conversion layer formation region In the thin film solar cell formed by electrically connecting in series the unit photoelectric conversion parts (unit cells) adjacent to each other on the surface through the connection hole and the current collecting hole,
A cell end lower electrode processing line for patterning for electrically insulating the first electrode layer by the photoelectric conversion layer is provided at an outer end along the series connection direction of the photoelectric conversion unit, and the photoelectric conversion unit The conversion layer and the transparent electrode layer are provided outside the cell end lower electrode processing line so as to extend to the side end of the photoelectric conversion unit, and the connection electrode layer is a region having a predetermined dimension width from the side end. Is removed from the back surface of the substrate.   2. The thin film solar cell according to claim 1, wherein a predetermined dimension width of a region where the connection electrode layer is removed is at least 0.5 mm.     3. The method for manufacturing a thin-film solar battery according to claim 1, wherein the cell edge lower electrode processing line is formed by laser processing.   4. The method of manufacturing a thin film solar cell according to claim 1, wherein the region where the connection electrode layer is removed is any one of laser processing, processing by an ultrasonic vibrator, and sand blast processing. 5. A method for producing a thin-film solar cell, characterized by being formed by any of the methods.

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