JP6000315B2 - Photovoltaic element manufacturing method - Google Patents

Description

  The present invention relates to a photovoltaic device, a solar cell module using the photovoltaic device, a photovoltaic power generation system, and a method for manufacturing a photovoltaic device.

  In the heterojunction type photovoltaic element, an amorphous semiconductor layer having the same conductivity type as the semiconductor substrate is formed on one surface of the semiconductor substrate, and the other surface of the semiconductor substrate is opposite to the semiconductor substrate. A non-crystalline semiconductor layer having another conductivity type is formed, and a transparent conductive film is laminated on each semiconductor layer. Note that an intrinsic amorphous semiconductor layer may be formed on both surfaces of the semiconductor substrate before the above-described semiconductor layer is formed.

  This photovoltaic element exhibits high passivation performance by terminating dangling bonds present at the interface between the semiconductor substrate and the semiconductor layer with hydrogen. However, when the thermal history after forming the semiconductor layer exceeds 200 degrees, hydrogen that terminates the dangling bonds is desorbed. Therefore, it is not possible to use the fire-through method used in general silicon-based solar cells. Can not. For this reason, as described above, it is necessary to laminate a transparent conductive film on each semiconductor layer. The transparent conductive film in the photovoltaic element plays two roles of current collection up to the collector electrode and antireflection film.

  FIG. 10 shows an equivalent circuit of the photovoltaic element. As shown in FIG. 10, in the photovoltaic device, the series resistance Rs is brought close to 0Ω, and the parallel resistance Rsh is made extremely high (close to infinity) to increase the output characteristics of the photovoltaic device. It becomes.

  By the way, when forming a transparent conductive film, since a manufacturing method such as sputtering or CVD is used, the transparent conductive film goes around not only the surface of the semiconductor layer but also the side surfaces of the semiconductor layer and the substrate. In this case, the transparent conductive film on the semiconductor layer exhibiting one conductivity type and the transparent conductive film on the semiconductor layer exhibiting another conductivity type are in electrical contact. As a result, the parallel resistance Rsh of the photovoltaic element is reduced, the leakage current is increased, and the output characteristics of the photovoltaic element are deteriorated. Therefore, as a technique for avoiding such electrical contact, edge isolation using laser light or the like is generally known (see Patent Document 1).

Japanese Patent No. 3349308

  However, as in Patent Document 1, it is necessary to introduce dedicated equipment in order to perform edge isolation, which has been a factor of increasing costs. In Patent Document 1, a collector electrode is formed on a semiconductor layer of another conductivity type, and a back electrode is formed on the semiconductor layer of one conductivity type. In this case, the interface of each layer from the semiconductor substrate to the back electrode is in ohmic contact. Further, the transparent conductive film on the side where the collector electrode is formed extends to the side surface of the semiconductor substrate, and the transparent conductive film and the semiconductor substrate are in ohmic contact. Here, the ohmic contact is not only an ohmic contact that provides electrical conduction in accordance with Ohm's law, but even if there is a potential barrier above the valence band or below the conductor, its height is the thermal energy. Also included are contacts that can conduct electricity similar to ohmic contacts, such as when they are low compared to or when their width is narrow enough to allow carriers to penetrate through the tunnel effect. For this reason, there is a problem in that leakage current is generated due to ohmic conduction between the transparent conductive film on the side where the collector electrode is formed and the back electrode through the semiconductor substrate.

  Therefore, the present invention pays attention to the above problem, and reduces the ohmic conduction between the transparent conductive film on the side where the collector electrode is formed and the back electrode, thereby suppressing the leakage current and realizing high efficiency. An object of the present invention is to provide an electromotive force element, a solar cell module using the same, and a solar power generation system. Another object of the present invention is to provide a photovoltaic device manufacturing method for manufacturing the above-described photovoltaic device without passing through post-processes such as edge isolation.

  In order to achieve the above object, a photovoltaic device according to the present invention includes, firstly, a one-conductivity-type crystalline semiconductor substrate and a one-conductivity-type layered on the first main surface of the semiconductor substrate. An amorphous first semiconductor layer, a first transparent conductive film stacked on the first semiconductor layer, and an amorphous second semiconductor of another conductivity type stacked on a second main surface of the semiconductor substrate And a second transparent conductive film laminated on the second semiconductor layer, wherein the second transparent conductive film is on the inner side of the periphery of the main surface of the second semiconductor layer. The collector electrode is provided in the region, the collector electrode is provided on the first transparent conductive film, and the back electrode is provided on the second transparent conductive film.

  In the above configuration, the first transparent conductive film in which the collector electrode is disposed serves as a sunlight receiving surface. Further, with the above configuration, the second transparent conductive film stacked on the second semiconductor layer is not in contact with the semiconductor substrate, and the second electrode of the other conductivity type and the second electrode of the semiconductor substrate Non-ohmic conduction is established between each layer formed on the main surface side. Therefore, even if the first transparent conductive film laminated on the first semiconductor layer wraps around the side surface of the semiconductor substrate and further to the side surface of the second semiconductor layer, it is between the first transparent conductive film and the back electrode. Does not become ohmic conduction due to the presence of the second semiconductor layer. Accordingly, a highly efficient photovoltaic device is obtained by suppressing leakage current from the first transparent conductive film to the back electrode.

Second, the first transparent conductive film extends from the peripheral edge of the first semiconductor layer to the side surface thereof and covers the side surface of the semiconductor substrate.
With the above configuration, it is possible to increase the current collection efficiency of carriers from the first semiconductor layer of the first transparent conductive film while maintaining a state in which leakage current from one transparent conductive film to the back electrode is suppressed.

Third, an intrinsic amorphous semiconductor layer is provided between the semiconductor substrate and the first semiconductor layer and between the semiconductor substrate and the second semiconductor layer, respectively. Features.
With the above configuration, the recombination loss of carriers can be reduced and the conversion efficiency of the photovoltaic element can be increased.

A solar cell module according to the present invention includes the above-described photovoltaic element.
With the above configuration, the leakage current from the first transparent conductive film to the back electrode is suppressed, and a highly efficient solar cell module is obtained.

The photovoltaic power generation system according to the present invention includes the above-described solar cell module.
Leakage current from the first transparent conductive film to the back electrode is suppressed to provide a highly efficient solar power generation system.

  On the other hand, in the method of manufacturing a photovoltaic device according to the present invention, an amorphous first semiconductor layer of one conductivity type is stacked on a first main surface of a crystal semiconductor substrate of one conductivity type, and the semiconductor A laminated body obtained by laminating an amorphous second semiconductor layer of another conductivity type on the second main surface of the substrate is disposed on a substrate holder, and the laminated body has a surface on which the second semiconductor layer is laminated. The substrate holder is disposed toward the substrate holder, and the substrate holder is previously formed with an opening that exposes the surface of the stacked body on which the second semiconductor layer is stacked, leaving a peripheral portion thereof, The transparent conductive film material is supplied toward the main surface of the first semiconductor layer in a state where the laminated body is disposed on the substrate holder, the first transparent conductive film is stacked, and the transparent conductive film material is formed through the opening. Is supplied toward the main surface of the first semiconductor layer to laminate a second transparent conductive film. Wherein the first transparent conductive film to form a collecting electrode, method of producing a photovoltaic element characterized by forming a back surface electrode on the second transparent conductive film.

  By the above method, the substrate holder can be used as a mask for shielding only the periphery of the second semiconductor layer against the material of the second transparent conductive film. Therefore, the second transparent conductive film is not laminated on the periphery of the second semiconductor layer covered with the mask, and the second transparent conductive film does not contact the first transparent conductive film. Therefore, the above-described photovoltaic element can be manufactured without going through a post-process such as edge isolation.

  According to the photovoltaic device, the solar cell module using the photovoltaic device, and the photovoltaic power generation system according to the present invention, it is possible to suppress leakage current from the first transparent conductive film disposed on the collector electrode side to the back electrode. it can. Moreover, according to the method for manufacturing a photovoltaic element according to the present invention, the above-described photovoltaic element can be manufactured without going through a post-process such as edge isolation.

It is a schematic diagram (sectional drawing) of the photovoltaic device of this embodiment. It is a schematic diagram (back view) of the photovoltaic device of this embodiment. It is a schematic diagram (front view) of the manufacturing apparatus of the photovoltaic element of this embodiment. It is a schematic diagram (plan view) of a photovoltaic device manufacturing apparatus of the present embodiment. It is a schematic diagram (sectional drawing) which shows before lamination | stacking of the transparent conductive film in the manufacturing apparatus of the photovoltaic element of this embodiment. It is a schematic diagram (cross-sectional view) which shows after lamination | stacking of the transparent conductive film in the manufacturing apparatus of the photovoltaic element of this embodiment. It is a schematic diagram (sectional drawing) of the photovoltaic element of a comparative example. It is a figure which shows the dark current characteristic of an Example and a comparative example. It is a figure which shows IV characteristic of an Example and a comparative example. It is a figure which shows the equivalent circuit of a photovoltaic device.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .

  1 and 2 are schematic views (cross-sectional view, back view) of the photovoltaic element of this embodiment. The photovoltaic element 10 of this embodiment uses a single crystal silicon substrate 12 (semiconductor substrate) of one conductivity type (n-type). The first main surface 12a of the silicon substrate 12 has an intrinsic (i-type) amorphous i-type silicon layer 14 (semiconductor layer), a single-conductivity type (n-type) amorphous layer. An n-type silicon layer 16 (first semiconductor layer), a first transparent conductive film 18 made of ITO (Indium Tin Oxide), and the like, and a collector electrode 20 are laminated in that order. Therefore, the first main surface 12a side of the silicon substrate 12 is a sunlight receiving surface.

  On the other hand, an intrinsic (i-type) amorphous (amorphous) i-type silicon layer 22 (semiconductor layer) and other conductivity type (p-type) amorphous are formed on the second main surface 12b of the silicon substrate 12. A p-type silicon layer 24 (second semiconductor layer), a second transparent conductive film 26 made of ITO or the like, and a back electrode 28 are laminated in that order.

  The i-type silicon layers 14 and 22, the n-type silicon layer 16, and the p-type silicon layer 24 can be grown by a plasma CVD method using a silicon compound such as silane. Of these, diborane or the like may be added to the silicon compound when the n-type silicon layer 16 is grown, and phosphine or the like may be added to the silicon compound when the p-type silicon layer 24 is grown. Moreover, the 1st transparent conductive film 18 and the 2nd transparent conductive film 26 can be made to grow by the below-mentioned sputtering method.

  The dust collection electrode 20 and the back electrode 28 can be formed by a printing technique using a conductive paste. As a material for the back electrode 28, it is preferable to use a conductive paste such as silver, nickel, copper, aluminum, or carbon. On the other hand, although not shown, the collector electrode 20 needs to be formed in a comb shape in order to reduce the light shielding rate with respect to the first transparent conductive film 18 to reduce the current-carrying area. For this reason, in order to make it a good conductor in a state where the energization area is small, it is preferable to use a highly conductive silver paste as the material of the collector electrode 20.

  As shown in FIGS. 1 and 2, the first transparent conductive film 18 is laminated on the n-type silicon layer 16 (FIG. 1), but protrudes from the periphery of the n-type silicon layer 16 and is n-type. The side surface of the silicon layer 16, the side surface of the silicon substrate 12, the side surface of the i-type silicon layer 22, and the side surface of the p-type silicon layer 24 are extended.

  On the other hand, the second transparent conductive film 26 is laminated on the p-type silicon layer 24, but the peripheral edge of the main surface of the p-type silicon layer 24 (the peripheral edge of the main surface of the i-type silicon layer 22 and the silicon substrate 12. Is formed in a region slightly inward from the peripheral edge of the main surface.

  With the above configuration, the second transparent conductive film 26 laminated on the p-type silicon layer 24 is not in contact with the silicon substrate 12, and the back electrode 28 and the silicon substrate are formed by the p-type silicon layer 24 of another conductivity type. Non-ohmic conduction is established between each layer formed on the second main surface 12b side of the twelve. Therefore, as shown in FIG. 1, even if the first transparent conductive film 18 stacked on the n-type silicon layer 16 wraps around the side surface of the silicon substrate 12 and further to the side surface of the p-type silicon layer 24, There is no ohmic conduction between the transparent conductive film 18 and the back electrode 28 due to the presence of the p-type silicon layer 24. Therefore, the leakage current from the first transparent conductive film 18 to the back electrode 28 is suppressed, and the photovoltaic element 10 becomes highly efficient.

  The first transparent conductive film 18 extends from the periphery of the n-type silicon layer 16 to its side surface and covers the side surface of the silicon substrate 12. Thereby, the current collection efficiency of carriers from the n-type silicon layer 16 of the first transparent conductive film 18 can be increased while maintaining a state in which the leakage current from the first transparent conductive film 18 to the back electrode 28 is suppressed.

  Further, an i-type silicon layer 14 is provided between the silicon substrate 12 and the n-type silicon layer 16, and an i-type silicon layer 22 is provided between the silicon substrate 12 and the p-type silicon layer 24. Thereby, the recombination loss of a carrier can be reduced and the conversion efficiency of the photovoltaic element 10 can be improved.

  3 and 4 are schematic views (a front view and a plan view) of the photovoltaic device manufacturing apparatus of the present embodiment. 5 and 6 are schematic views (cross-sectional views) showing the transparent conductive film before and after lamination in the photovoltaic device manufacturing apparatus of this embodiment.

  The manufacturing apparatus 100 (sputtering apparatus) for the photovoltaic element 10 of this embodiment is for growing the first transparent conductive film 18 and the second transparent conductive film 26. In the manufacturing apparatus 100, a substrate holder 102 on which the stacked body 13 is placed is disposed in a chamber (not shown). Here, the stacked body 13 is formed by laminating the i-type silicon layer 14 and the n-type silicon layer 16 in this order on the first main surface 12a of the silicon substrate 12, and the i-type silicon layer 22 and p on the second main surface 12b. The type silicon layers 24 are stacked in this order. In the chamber, cylindrical targets 106 and 108 obtained by sintering a transparent conductive film material are disposed at positions above and below the substrate holder 102, respectively. Here, the substrate holder 102 can be moved by the driving mechanism 103 from the position facing the one target 106 to the position facing the other target 108.

  Each of the targets 106 and 108 has a hollow cylindrical shape. Magnets 109 are disposed inside the targets 106 and 108, respectively. When power is supplied from a high voltage power supply for glow discharge, high density discharge plasma is formed by being confined by magnetic lines generated by the magnets 109. . For this reason, ions generated in the high-density discharge plasma are irradiated and the materials of the targets 106 and 108 are blown off and reach the laminate 13. On the other hand, the targets 106 and 108 rotate around a cylindrical axis. Thereby, in the chamber, the position where the material of the targets 106 and 108 is flipped is substantially fixed, but the position where the material is flipped off on the cylindrical surface of the targets 106 and 108 is moved by rotation. In the figure, the material of the target 106 scatters from the target 106 arranged at the upper part toward the upper surface of the substrate holder 102 (laminated body 13), and the substrate holder 102 (laminated body) from the target 108 arranged at the lower part. The material of the target 108 is scattered toward the lower surface of 13).

  At the position where the stacked body 13 of the substrate holder 102 is placed, an opening 104 that is similar to the outer shape of the stacked body 13 (silicon substrate 12) and slightly smaller than the stacked body 13 is formed. Only the peripheral edge is supported by the substrate holder 102. As a result, the peripheral edge of the stacked body 13 is shielded (masked) against the material blown off from the target 108, the remaining part is exposed by the opening 104, and the material flipped off from the target 108 is deposited.

  As shown in FIG. 5, in this embodiment, the stacked body 13 is mounted on the substrate holder 102 with the second main surface 12 b of the silicon substrate 12, that is, the surface on which the p-type silicon layer 24 is formed facing the opening 104. Put. Further, as shown in FIG. 6, in the present embodiment, the first transparent conductive film 18 is laminated on the first main surface 12a side, and the second transparent conductive film 26 is laminated on the second main surface 12b side. The order is arbitrary. 3 and 4, the transparent conductive film is laminated on each side, but the targets 106 and 108 may sandwich the laminated body 13 at the same time, and the transparent conductive film may be laminated on both sides simultaneously.

  Then, after laminating the first transparent conductive film 18 and the second transparent conductive film 26, the collector electrode 20 is formed on the first transparent conductive film 18, and the back electrode 28 is formed on the second transparent conductive film 26. 1 and 2 are formed.

  Through the above process, the substrate holder 102 can be used as a mask that shields only the periphery of the p-type silicon layer 24 from the material of the second transparent conductive film 26. Therefore, the second transparent conductive film 26 is not laminated on the periphery of the p-type silicon layer 24 covered with the mask, and the second transparent conductive film 26 does not contact the first transparent conductive film 18. Therefore, the photovoltaic element 10 can be manufactured without passing through post-processes such as edge isolation.

[Example]
A manufacturing process of the photovoltaic device 10 of the present embodiment will be described. First, a square single crystal n-type silicon substrate 12 having a side of 156 mm was prepared. Then, an amorphous i-type silicon layer 14 and an amorphous n-type silicon layer 16 are sequentially stacked on the first main surface 12a of the silicon substrate 12 by plasma CVD, and the second main surface 12b is stacked. An amorphous i-type silicon layer 22 and an amorphous p-type silicon layer 24 were sequentially stacked.

  Next, the first transparent conductive film 18 and the second transparent conductive film 26 are laminated by sputtering. At that time, as the targets 106 and 018, a cylindrical sintered body of ITO containing 3 wt% of tin (Sn) was used. Further, a square opening 104 having a side of 152 mm was formed in the substrate holder 102, and the silicon substrate 12 was placed in the substrate holder 102 so as to cover the opening 104.

  Here, if the opening 104 is excessively widened, the silicon substrate 12 is displaced, and the first transparent conductive film 18 and the second transparent conductive film 26 are in electrical contact locally. Conversely, if the opening 104 is made too narrow, the substantial power generation area becomes narrow. Therefore, the size of the opening 104 when using the 156 mm square silicon substrate 12 is preferably 150 mm square to 155 mm square. At this time, the mask region (non-deposition region) of the second transparent conductive film 26 has a rectangular ring shape having a width of 0.5 mm to 3 mm inside from the periphery of the silicon substrate 12.

  The thickness of each layer is about 200 μm for the silicon substrate 12, about 10 nm for the i-type silicon layer 14 and the n-type silicon layer 16, the i-type silicon layer 22, the p-type silicon layer 24, the first transparent conductive film 18, and the first transparent conductive film 18. 2 The transparent conductive film 26 is about 100 nm.

  In the embodiment, since the silicon substrate 12 is 156 mm square and the opening 104 is 152 mm square, the mask region (non-deposition region) for the second transparent conductive film 26 has a width of 2 mm from the periphery of the silicon substrate 12 to the inside thereof. It became the rectangular ring shape which has. On the other hand, the first transparent conductive film 18 was laminated on the n-type silicon layer 16 so as to wrap around the side surface of the silicon substrate 12. Thereafter, the collector electrode 20 was formed on the first transparent conductive film 18 and the back electrode 28 was formed on the second transparent conductive film 26 by a printing technique using a conductive paste.

  In FIG. 7, the schematic diagram (sectional drawing) of the photovoltaic element of a comparative example is shown. In the embodiment, the stacked body 13 is arranged on the substrate holder 102 so that the p-type silicon layer 24 faces the opening 104. However, in the comparative example, the n-type silicon layer 16 faces the opening 104 in the stacked body 13. Thus, the laminate 13 was placed on the substrate holder 102 to form the photovoltaic element 11. In the comparative example, the second transparent conductive film 26 laminated on the p-type silicon layer 24 wraps around the side surface of the silicon substrate 12, and the first transparent conductive film 18 laminated on the n-type silicon layer 16 has the opening 104 (mask ) In a region slightly inside the periphery of the n-type silicon layer 16. Then, the back electrode 28 was formed on the first transparent conductive film 18, and the collector electrode 20 was formed on the second transparent conductive film 26. Therefore, in the photovoltaic element 11, the 2nd transparent conductive film 26 side turns into a light-receiving surface of sunlight.

  FIG. 8 shows dark current characteristics of Examples and Comparative Examples, and FIG. 9 shows IV characteristics of Examples and Comparative Examples. In FIG. 8, the horizontal axis represents the applied voltage (V) between the collector electrode 20 and the back electrode 28, and the vertical axis represents the dark current (A) flowing through the photovoltaic elements 10 and 11. FIG. 9 shows the measurement of open circuit voltage, short circuit current, and load characteristics by irradiating the photovoltaic elements 10 and 11 with light to generate electromotive force.

As shown in FIG. 8, when the applied voltage is 0.6 V or more, there is almost no difference between the example and the comparative example. However, when the applied voltage is 0.6 V or less, there is a difference between them. At 0.3 V, the dark current of the example is about 1/10 lower than the dark current of the comparative example . At 1V, the voltage drops to about 1/50.

  In the comparative example, ohmic conduction occurs between the silicon substrate 12 and the back electrode 28. Further, the second transparent conductive film 26 laminated on the p-type silicon layer 24 wraps around the side surface of the n-type silicon layer 16 (FIG. 7), and both are in ohmic conduction. Therefore, the second transparent conductive film 26 and the back electrode 28 are in ohmic conduction. Therefore, as shown in FIG. 8, in the comparative example, the dark current (leakage current) in the low bias region cannot be suppressed as compared with the example, and the current during light irradiation is also dark as shown in FIG. The output is lower than that of the embodiment by the amount of current, and the output characteristics are inferior to those of the embodiment.

  A solar cell module can be constructed by, for example, arranging a plurality of photovoltaic elements 10 of the present embodiment in an array on a panel and connecting them in parallel. Moreover, a solar power generation system can be constructed by arranging a plurality of solar cell modules outdoors (roof).

  Although the i-type silicon layer 14 is laminated on the first surface 12a of the silicon substrate 12 and the i-type silicon layer 22 is laminated on the second surface 12b, it is sufficient for reasons such as low carrier recombination loss. If a high conversion efficiency can be obtained, these may be omitted.

Photovoltaic element realizing high efficiency by suppressing leakage current by reducing ohmic conduction between transparent electrode on the side where collector electrode is formed and back electrode, and solar cell module using the same Can be used as a solar power generation system. Moreover, it can utilize as a manufacturing method of the photovoltaic element for manufacturing the above-mentioned photovoltaic element, without passing through post processes, such as edge isolation.

DESCRIPTION OF SYMBOLS 10 ......... Photovoltaic element, 12 ......... Silicon substrate, 13 ......... Laminated body, 12a ......... First main surface, 12b ......... Second main surface, 14 ......... i-type silicon Layer, 16 ... n-type silicon layer, 18 ... first transparent conductive film, 20 ... collector electrode, 22 ... i-type silicon layer, 24 ... p-type silicon layer, 26 ... Second transparent conductive film 28... Back electrode 100... Manufacturing apparatus 102... Substrate holder 104... Opening 106.

Claims (1)

An amorphous first semiconductor layer of one conductivity type is stacked on a first main surface of a crystalline semiconductor substrate of one conductivity type, and an amorphous of another conductivity type is deposited on the second main surface of the semiconductor substrate. A laminated body obtained by laminating the second semiconductor layer is placed on a substrate holder,
The stacked body is arranged with the surface on which the second semiconductor layer is stacked facing the substrate holder side,
In the substrate holder, an opening is formed in advance to expose the surface of the stacked body on which the second semiconductor layer is stacked, leaving a peripheral portion thereof,
In a state where the laminate is disposed on the substrate holder, the material of the transparent conductive film is supplied toward the main surface and the side surface of the first semiconductor layer to stack the first transparent conductive film, and the transparent conductive material is passed through the opening. Supplying a film material toward the main surface of the second semiconductor layer, and laminating a second transparent conductive film;
Forming a collector electrode on the first transparent conductive film;
A method of manufacturing a photovoltaic element, comprising forming a back electrode on the second transparent conductive film.

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