WO2015189878A1

WO2015189878A1 - Solar cell and method for manufacturing same

Info

Publication number: WO2015189878A1
Application number: PCT/JP2014/003159
Authority: WO
Inventors: 金子　哲也; 宏野毛; 愛子佐藤; 公彦斉藤; 近藤　道雄
Original assignee: 国立大学法人福島大学; 独立行政法人産業技術総合研究所
Priority date: 2014-06-13
Filing date: 2014-06-13
Publication date: 2015-12-17
Also published as: JPWO2015189878A1

Abstract

Disclosed is an invention of a solar cell. The solar cell is provided with: a semiconductor substrate (10); an intrinsic first amorphous semiconductor layer (1); a second amorphous semiconductor layer (2) containing an impurity; a first electrode (11) that is disposed on the whole one surface on the second amorphous semiconductor layer (2); an intrinsic third amorphous semiconductor layer (3); a fourth amorphous semiconductor layer (4) containing an impurity; and a second electrode (12) that is disposed on the fourth amorphous semiconductor layer (4). The first amorphous semiconductor layer (1) has a comb shape. The third amorphous semiconductor layer (3) has a comb shape that engages with the first amorphous semiconductor layer (1). A part of the third amorphous semiconductor layer (3) overlaps the first electrode (11) in a plan view.

Description

Solar cell and manufacturing method thereof

The present invention relates to a solar cell and a manufacturing method thereof. More specifically, the present invention relates to a solar cell having a back electrode type heterojunction structure and a manufacturing method thereof.

In recent years, solar cells having a heterojunction structure have been proposed. For example, Japanese Patent Publication No. 4-130671 discloses an example of a solar cell having a heterojunction structure. Also, the literature `` Mikio Taguchi, Akira Terakawa, Eiji Maruyama and Makoto Tanaka, Obtaining a HigherVoc in HIT cells', Progress in Photovoltaics: Research and Applications, Vol.13,481-488, 2005 '' Another example is disclosed. In these solar cells, an amorphous silicon layer and an electrode are arranged on one surface of the n-type single crystal silicon substrate and the opposite surface, respectively.

In a solar cell having a heterojunction structure, light is received from the main surface side of the n-type single crystal silicon substrate, and power is generated by generating excess carriers in the n-type single crystal silicon substrate. The electric power generated at this time can be taken out by the two electrodes which are electrically paired.

Here, in the structure in which the electrode and the amorphous silicon layer are arranged on the main surface serving as the light receiving surface as in the aspect described in the above-mentioned document, since these absorb light, the n-type single crystal silicon substrate As a result, the number of photons incident on the light source decreases and the power generation efficiency decreases. In view of this, a solar cell having a back electrode type heterojunction structure in which an amorphous silicon layer of a different type and a pair of electrodes are arranged on the back surface opposite to the light receiving surface has been proposed.

For example, Japanese Patent Publication No. 2003-298078 discloses a solar cell having such a structure. Also, the documents `` Meijun Lu, Ujjwal Das, Stuart Bowden, Steven Hegedus and RobertBirkmire, Opt'Optimization of interdigitated back contact silicon heterojunctionsolar cells: tailoring hetero-interface band structures while maintainingsurface passics , 326-338, 2011 "discloses another example. Japanese Patent Publication No. 2013-168605 discloses another example. Japanese Patent Publication No. 2013-131586 discloses another example. Japanese Patent Publication 2005-101151 discloses another example. Another example is disclosed in International Patent Publication No. WO2010 / 113750. Another example is disclosed in Japanese Patent Publication No. 2009-200267. In addition, another example is disclosed in US Pat. No. US8525018.

However, these disclosed solar cells cannot efficiently extract holes that are minority carriers generated in the n-type single crystal silicon substrate, or leak current between the electrodes is likely to be generated. The power generation efficiency cannot be improved sufficiently.

The invention of the solar cell is disclosed below. The solar cell
A semiconductor substrate of one conductivity type having a light receiving surface and a back surface;
An intrinsic first amorphous semiconductor layer disposed on the back surface of the semiconductor substrate and having a comb shape;
A second amorphous semiconductor layer that is disposed on the first amorphous semiconductor layer and includes an impurity having a conductivity type different from that of the semiconductor substrate;
A first electrode disposed on the entire surface of the second amorphous semiconductor layer;
An intrinsic third amorphous semiconductor layer which is disposed on the back surface of the semiconductor substrate and has a comb shape which meshes with the first amorphous semiconductor layer and partially overlaps the first electrode in plan view; ,
A fourth amorphous semiconductor layer including an impurity disposed on the third amorphous semiconductor layer and including an impurity having the same conductivity type as the semiconductor substrate;
And a second electrode disposed on the fourth amorphous semiconductor layer.

An invention of a method for manufacturing a solar cell is disclosed below. The manufacturing method of the solar cell is as follows:
Forming an intrinsic first amorphous semiconductor layer on the back surface of the one-conductivity-type semiconductor substrate having a light-receiving surface;
Forming a second amorphous semiconductor layer containing an impurity having a conductivity type different from that of the semiconductor substrate on the first amorphous semiconductor layer;
Forming a first electrode on the second amorphous semiconductor layer;
Etching the first amorphous semiconductor layer, the second amorphous semiconductor layer, and the first electrode into a comb shape on the back surface of the semiconductor substrate;
Forming an intrinsic third amorphous semiconductor layer including the portion of the semiconductor substrate exposed by the etching on the back surface of the semiconductor substrate provided with the first electrode;
Forming a fourth amorphous semiconductor layer containing an impurity having the same conductivity type as that of the semiconductor substrate on the third amorphous semiconductor layer;
The third amorphous semiconductor layer and the fourth amorphous semiconductor layer are engaged with the first electrode, and a part of the third amorphous semiconductor layer is the first electrode. Etching into a comb shape overlapping in plan view,
Forming a second electrode on the fourth amorphous semiconductor layer.

According to the invention of the solar cell, since the first electrode is arranged on the entire surface of the second amorphous semiconductor layer, carriers can be efficiently taken out. improves.

According to the invention of the solar cell manufacturing method, a solar cell with high power generation efficiency can be easily manufactured with high accuracy.

It is typical sectional drawing which shows 1st Embodiment of a solar cell. It is a schematic plan view which shows a part of back surface of 1st Embodiment of a solar cell. It is typical sectional drawing which shows 2nd Embodiment of a solar cell. It is a schematic plan view which shows a part of back surface of 2nd Embodiment of a solar cell. FIG. 5 is composed of FIGS. 5A to 5J. FIG. 5 is a schematic cross-sectional view showing the manufacturing method of the first embodiment of the solar cell. FIG. 5A shows the state after the first electrode is formed. FIG. 5B shows a state after the mask for etching the first electrode is formed. FIG. 5C shows the state after the first electrode has been etched. FIG. 5D shows the situation after the mask has been removed. FIG. 5E shows a state after the fourth amorphous semiconductor layer is formed. FIG. 5F shows a state after the mask for etching the fourth amorphous semiconductor layer is formed. FIG. 5G shows a state after the fourth amorphous semiconductor layer is etched. FIG. 5H shows the situation after the mask is removed. FIG. 5I shows the state after the second electrode and the collector electrode are formed. FIG. 5J shows the state after the antireflection layer is formed. FIG. 6 is configured from FIGS. 6A to 6D. FIG. 6 is a schematic cross-sectional view showing the manufacturing method of the second embodiment of the solar cell. FIG. 6A shows the state after the first electrode has been etched. FIG. 6B shows the state after the insulator layer 9 is formed. FIG. 6C shows a state after the fourth amorphous semiconductor layer is etched. FIG. 6D shows the state after the second electrode and the collector electrode are formed. In 1st Embodiment of a solar cell, the relationship between the separation distance of an electrode and the conversion efficiency (relative value) of a solar cell when hole mobility (micro | micron | mu) in amorphous silicon is made into 2 types is shown. It is a graph.

In this specification, terms are defined as follows. Crystalline semiconductors include single crystal semiconductors and polycrystalline semiconductors. Amorphous semiconductors include amorphous semiconductors and microcrystalline semiconductors. An intrinsic amorphous semiconductor is an amorphous semiconductor that is not intentionally doped with impurities. Intrinsic amorphous semiconductors include amorphous semiconductors containing impurities that are inherently contained in semiconductor raw materials or impurities that are naturally mixed in the manufacturing process. The plan view means that the solar cell is viewed from the back side in a direction perpendicular to the surface of the semiconductor substrate unless otherwise specified.

[First Embodiment]
FIG. 1 shows a first embodiment of a solar cell. FIG. 2 shows a part of the back surface of the first embodiment of the solar cell. The reason why it is a part of the back surface is that a part of the comb shape is shown. Actually, the comb shape may have a larger number of comb teeth. In FIG. 1, a direction S perpendicular to the substrate to be viewed in plan is indicated by an arrow. In FIG. 1, the direction P in which light travels is indicated by a white arrow. This solar cell is a solar cell having a back electrode type heterojunction structure.

The solar cell includes a semiconductor substrate 10, a first amorphous semiconductor layer 1, a second amorphous semiconductor layer 2, a first electrode 11, and a third amorphous semiconductor layer. 3, a fourth amorphous semiconductor layer 4, and a second electrode 12. The semiconductor substrate 10 has a light receiving surface 10a and a back surface 10b. The semiconductor substrate 10 is of one conductivity type. The first amorphous semiconductor layer 1 is disposed on the back surface 10 b of the semiconductor substrate 10. The first amorphous semiconductor layer 1 is an intrinsic amorphous semiconductor layer. The first amorphous semiconductor layer 1 has a comb shape. The second amorphous semiconductor layer 2 is disposed on the first amorphous semiconductor layer 1. The second amorphous semiconductor layer 2 exhibits a conductivity type different from that of the semiconductor substrate 10. The second amorphous semiconductor layer 2 is an amorphous semiconductor layer containing impurities. The first electrode 11 is disposed on the entire surface of the second amorphous semiconductor layer 2. The third amorphous semiconductor layer 3 is disposed on the back surface 10 b of the semiconductor substrate 10. The third amorphous semiconductor layer 3 is an intrinsic amorphous semiconductor layer. The third amorphous semiconductor layer 3 has a comb shape that meshes with the first amorphous semiconductor layer 1. The third amorphous semiconductor layer 3 partially overlaps the first electrode 11 in plan view. The fourth amorphous semiconductor layer 4 is disposed on the third amorphous semiconductor layer 3. The fourth amorphous semiconductor layer 4 has the same conductivity type as that of the semiconductor substrate 10. The fourth amorphous semiconductor layer 4 is an amorphous semiconductor layer containing impurities. The second electrode 12 is disposed on the fourth amorphous semiconductor layer 4.

In the present embodiment, the first collector electrode 5 is disposed on the first electrode 11. A second collector electrode 6 is disposed on the second electrode 12. The second electrode 12 is separated from the first electrode 11 in plan view.

In the semiconductor substrate 10, the light receiving surface 10a is a surface that receives light. The light receiving surface 10a is also called a light incident surface. The light receiving surface 10a is defined as a main surface. The back surface 10b is a surface opposite to the light receiving surface 10a.

The semiconductor substrate 10 is a thin-plate semiconductor substrate. The semiconductor substrate 10 has a p-type or n-type conductivity type. One conductivity type means either p or n. The semiconductor substrate 10 is preferably n-type. The semiconductor substrate 10 is made of crystalline silicon, a compound semiconductor, or other semiconductor material that can be formed into a plate shape. Examples of crystalline silicon include single crystal silicon and polycrystalline silicon. Examples of the compound semiconductor include GaAs and InP. As the semiconductor substrate 10, an n-type single crystal silicon substrate is preferably used.

The thickness of the semiconductor substrate 10 is not particularly limited. The thickness of the semiconductor substrate 10 is preferably 10 to 200 μm from the viewpoint of member cost and handling.

The semiconductor substrate 10 preferably has a texture structure on one or both sides of the semiconductor substrate 10 from the viewpoint of improving efficiency. Since the texture structure can sufficiently confine incident light, an improvement in efficiency can be expected. The texture structure may be a minute uneven structure, for example. The minute uneven structure may have periodicity. Of course, the texture structure is not essential.

In the semiconductor classification, an intrinsic semiconductor corresponds to i-type. The semiconductor containing impurities may be n-type or p-type.

Hereinafter, an example using the n-type semiconductor substrate 10 will be mainly described. Of course, a p-type semiconductor substrate 10 may be used, and in that case, the structure can be understood if n-type and p-type are interchanged in the following description.

The first amorphous semiconductor layer 1 is an i-type amorphous semiconductor layer. The first amorphous semiconductor layer 1 has a comb shape in plan view. The second amorphous semiconductor layer 2 is a p-type amorphous semiconductor layer. The second amorphous semiconductor layer 2 has a comb shape in plan view. The comb shape of the first amorphous semiconductor layer 1 and the comb shape of the second amorphous semiconductor layer 2 may coincide with each other. The first electrode 11 is a p-type electrode. The first electrode 11 constitutes a back electrode. The first electrode 11 has a comb shape in plan view. The comb shape of the second amorphous semiconductor layer 2 and the comb shape of the first electrode 11 may coincide with each other. That is, the first amorphous semiconductor layer 1, the second amorphous semiconductor layer 2, and the first electrode 11 can have the same comb shape.

In the example of FIG. 1, the second amorphous semiconductor layer 2 is disposed on the entire surface of the first amorphous semiconductor layer 1. It can be said that the second amorphous semiconductor layer 2 covers the first amorphous semiconductor layer 1. The first electrode 11 is disposed on the entire surface of the second amorphous semiconductor layer 2. It can be said that the first electrode 11 covers the second amorphous semiconductor layer 2. The first electrode 11, the first amorphous semiconductor layer 1, and the second amorphous semiconductor layer 2 are aligned at the ends. The first amorphous semiconductor layer 1 and the second amorphous semiconductor layer 2 do not protrude from the first electrode 11. Therefore, the contact area between the first electrode 11 and the second amorphous semiconductor layer 2 becomes larger. As described above, when the first electrode 11 is provided on the entire surface of the second amorphous semiconductor layer 2, holes that are minority carriers generated in the semiconductor substrate 10 can be efficiently extracted to the outside. . Thereby, the power generation efficiency is improved.

The third amorphous semiconductor layer 3 is an i-type amorphous semiconductor layer. The third amorphous semiconductor layer 3 has a comb shape in plan view. The fourth amorphous semiconductor layer 4 is an n-type amorphous semiconductor layer. The fourth amorphous semiconductor layer 4 has a comb shape in plan view. The comb shape of the third amorphous semiconductor layer 3 and the comb shape of the fourth amorphous semiconductor layer 4 may be the same. The second electrode 12 is an n-type electrode. The second electrode 12 constitutes a back electrode. The second electrode 12 has a comb shape in plan view. The comb shape of the second electrode 12 may be a comb shape having a narrower width than the comb shape of the fourth amorphous semiconductor layer 4. That is, the width of the comb-shaped comb teeth of the second electrode 12 is smaller than the width of the comb-shaped comb teeth of the third amorphous semiconductor layer 3 and the fourth amorphous semiconductor layer 4. Good.

In the example of FIG. 1, the fourth amorphous semiconductor layer 4 is disposed on the entire surface of the third amorphous semiconductor layer 3. It can be said that the fourth amorphous semiconductor layer 4 covers the third amorphous semiconductor layer 3. The third amorphous semiconductor layer 3 is placed on the first electrode 11. The third amorphous semiconductor layer 3 and the first electrode 11 are in contact with each other. The third amorphous semiconductor layer 3 is arranged so as to bridge adjacent comb teeth of the first electrode 11. The fourth amorphous semiconductor layer 4 is placed on the first electrode 11 following the shape of the third amorphous semiconductor layer 3. The fourth amorphous semiconductor layer 4 is arranged so as to bridge adjacent comb teeth of the first electrode 11. The ends of the third amorphous semiconductor layer 3 and the fourth amorphous semiconductor layer 4 are aligned.

The fourth amorphous semiconductor layer 4 has a flat portion 4a. The flat portion 4 a is a flat portion of the fourth amorphous semiconductor layer 4 that is not placed on the first electrode 11. The flat portion 4 a may be a portion where the surface of the fourth amorphous semiconductor layer 4 is formed in parallel with the surface of the semiconductor substrate 10. In the flat portion 4 a, there is no deformation of the fourth amorphous semiconductor layer 4 to be placed on the first electrode 11.

The second electrode 12 is preferably disposed on the flat portion 4a. The second electrode 12 is preferably arranged so as not to protrude from the flat portion 4a. The second electrode 12 does not have to be formed in a portion where the fourth amorphous semiconductor layer 4 is placed on the first electrode 11. By arranging the second electrode 12 on the flat portion 4a, the leakage current between the electrodes is reduced.

It is preferable that the first collector electrode 5 is disposed on the first electrode 11. Thereby, it becomes easy to take out an electric current. The first collector electrode 5 is disposed on a portion of the first electrode 11 that is not covered with the third amorphous semiconductor layer 3 and the fourth amorphous semiconductor layer 4. The edge of the first collector electrode 5 is located inside the edge of the first electrode 11. The first collector electrode 5 is not in contact with the third amorphous semiconductor layer 3 and the fourth amorphous semiconductor layer 4. Thereby, the occurrence of leakage current is suppressed. The first collector electrode 5 may have a comb shape. In the present embodiment, the first collector electrode 5 can be configured as a p-type collector electrode.

It is preferable that the second collector electrode 6 is disposed on the second electrode 12. Thereby, it becomes easy to take out an electric current. The second collector electrode 6 is preferably disposed on the entire surface of the second electrode 12. The second collector electrode 6 may have a comb shape. The comb shape of the second electrode 12 and the comb shape of the second collector electrode 6 may be the same shape. In the present embodiment, the second collector electrode 6 can be configured as an n-type collector electrode.

In the present embodiment, the first electrode 11 and the first collector electrode 5 on the p-type second amorphous semiconductor layer 2 constitute a positive electrode. The second electrode 12 and the second collector electrode 6 on the n-type fourth amorphous semiconductor layer 4 constitute a negative electrode.

The first amorphous semiconductor layer 1 and the third amorphous semiconductor layer 3 have a comb shape that meshes with each other. The second amorphous semiconductor layer 2 and the fourth amorphous semiconductor layer 4 have a comb shape that meshes with each other. The first electrode 11 and the second electrode 12 have a comb shape that meshes with each other. The first collector electrode 5 and the second collector electrode 6 have a comb shape that meshes with each other. Here, a combination of the second amorphous semiconductor layer 2 and the first electrode 11 is defined as a p-type structure, and the fourth amorphous semiconductor layer 4, the second electrode 12, Is defined as an n-type structure, it can be said that the p-type structure and the n-type structure have a comb shape that meshes with each other. The comb shape is a shape having a plurality of comb teeth extending linearly and a base portion connected to the plurality of comb teeth. The interdigitated comb shape is a shape in which two comb-shaped comb teeth are arranged between one comb-shaped comb teeth. This shape may be a shape in which one comb-shaped comb tooth and the other comb-shaped comb tooth are alternately arranged. The two comb-shaped bases can be arranged on opposite sides of each other. However, as shown in FIG. 1, a part of the third amorphous semiconductor layer 3 and the fourth amorphous semiconductor layer 4 are part of the first amorphous semiconductor layer when viewed in plan. The first amorphous semiconductor layer 2 and the first electrode 11 are overlapped. Therefore, there is no portion where the back surface 10b of the semiconductor substrate is directly exposed, and the surface recombination of carriers can be suppressed to improve efficiency.

Fig. 2 shows the comb shape. FIG. 2 shows a comb shape in which the first collector electrode 5 and the second collector electrode 6 are engaged with each other. The comb shape of the first collector electrode 5 includes a base portion 5B and a plurality of comb teeth 5A. The comb shape of the second collector electrode 6 includes a base portion 6B and a plurality of comb teeth 6A. Other layers of the comb shape will also be understood from this figure. However, in the first to fourth amorphous semiconductor layers, the interdigitated comb shapes partially overlap each other. Since the p-type amorphous semiconductor and the corresponding electrode, and the n-type amorphous semiconductor and the corresponding electrode are in a comb shape, the carriers generated by light reception are efficiently extracted to the outside. be able to.

The width of the comb teeth of the second amorphous semiconductor layer 2 is preferably larger than the width of the comb teeth of the fourth amorphous semiconductor layer 4. Thereby, minority carriers can be efficiently taken out over a wide area. Since the second amorphous semiconductor layer 2 has a conductivity type different from that of the semiconductor substrate 10, the efficiency is increased by increasing the area of the second amorphous semiconductor layer 2. The second amorphous semiconductor layer 2 becomes n-type when the n-type semiconductor substrate 10 is used, and becomes p-type when the p-type semiconductor substrate 10 is used. The width of the comb teeth is a length in a direction perpendicular to the direction in which the comb teeth extend. In FIG. 2, the width W5 of the comb teeth 5A of the first collector electrode 5 and the width W6 of the comb teeth 6A of the second collector electrode 6 are shown. 1 and 2, each layer (first electrode 11, second electrode 12, first amorphous semiconductor layer 1, second amorphous semiconductor layer 2, third amorphous system). The width of the comb teeth of the semiconductor layer 3 and the fourth amorphous semiconductor layer 4) will be understood. The width of the comb teeth of the second amorphous semiconductor layer 2 is preferably 1.2 times or more, more preferably 2 times or more than the width of the comb teeth of the fourth amorphous semiconductor layer 4. The above is more preferable. Similarly, the width of the comb teeth of the first electrode 11 is preferably larger than the width of the comb teeth of the second electrode 12. The width of the comb teeth of the first collector electrode 5 is preferably larger than the width of the comb teeth of the second collector electrode 6. FIG. 2 shows a relationship in which the width W5 of the comb teeth 5A of the first collector electrode 5 is larger than the width W6 of the comb teeth 6A of the second collector electrode 6. The width of the comb teeth of the first electrode 11 is not particularly limited, but may be in the range of 100 to 5000 μm, for example. The width of the comb teeth of the second electrode 12 is not particularly limited, but may be in the range of 10 to 1000 μm, for example.

In the present embodiment, the first electrode 11 and the second electrode 12 are separated from each other in plan view. That is, the first electrode 11 and the second electrode 12 do not overlap in plan view. It can be said that the comb teeth of the second electrode 12 are accommodated between the comb teeth of the first electrode 11. In FIG. 1, the distance at which the first electrode 11 and the second electrode 12 are separated is indicated by a separation distance D. The separation distance D is preferably larger than the total thickness of the third amorphous semiconductor layer 3 and the fourth amorphous semiconductor layer 4. Thereby, the leak current is easily reduced.

The separation distance D between the first electrode 11 and the second electrode 12 is preferably 10 μm or more and 100 μm or less. When the separation distance D is 100 μm or less, the series resistance with respect to the majority carriers decreases, and thus the efficiency is further improved. Further, when the separation distance D is 10 μm or more, the leakage current between the electrodes is easily reduced.

Each amorphous semiconductor layer (first to fourth amorphous semiconductor layers) is preferably composed of a hydrogenated amorphous semiconductor containing silicon. This is common to all of i-type, p-type and n-type. Examples of the amorphous semiconductor include amorphous silicon, amorphous silicon carbide, and amorphous silicon germanium. Of course, the amorphous semiconductor layer is not limited to these materials, and may be composed of other amorphous semiconductors. The amorphous semiconductor layer may be composed of other thin film semiconductors. When the first amorphous semiconductor layer 1 and the third amorphous semiconductor layer 3 are formed of the same material, their boundary portions may be ambiguous.

Examples of impurities in the p-type amorphous semiconductor layer include B (boron), Al, and Ga (gallium). This impurity is preferably a group III element. B (boron) is preferably used as the impurity. Examples of impurities in the n-type amorphous semiconductor layer include P (phosphorus), As (arsenic), and Sb (antimony). This impurity is preferably a group V element. P (phosphorus) is preferably used as the impurity.

The first electrode 11 may be a transparent electrode. The second electrode 12 may be a transparent electrode. These electrodes can be formed of, for example, a transparent metal oxide. The first electrode 11 and the second electrode 12 can be made of, for example, ITO (indium tin oxide), SnO ₂ (tin oxide), or ZnO (zinc oxide). The first electrode 11 and the second electrode 12 may be formed of the same material or may be formed of different materials. The first collector electrode 5 and the second collector electrode 6 may be made of metal. The first collector electrode 5 and the second collector electrode 6 can be made of, for example, Ag (silver), Al (aluminum), Cu (copper), or Au (gold). The first collector electrode 5 and the second collector electrode 6 are preferably made of Ag. The first collector electrode 5 and the second collector electrode 6 may be formed of the same material or different materials. In the case where an ohmic contact with the fourth amorphous semiconductor layer 4 can be formed and the diffusion of the electrode material does not affect, the second electrode 12 may be made of metal. In that case, the second electrode 12 may have the function of a collecting electrode, and the second collecting electrode 6 may be omitted. Thereby, the layer structure becomes easier.

The thickness of each amorphous semiconductor layer (first to fourth amorphous semiconductor layers) is not particularly limited, but may be in the range of 1 to 50 nm, for example. For example, the thickness of these amorphous semiconductor layers is about 10 nm. The thicknesses of the first electrode 11 and the second electrode 12 are not particularly limited, but may be in the range of 10 to 200 nm, for example. For example, the thickness of these electrodes is about 70 nm. The thickness of the first collector electrode 5 and the second collector electrode 6 is not particularly limited, but may be in the range of 100 to 1000 nm, for example. For example, the thickness of these collector electrodes is about 200 nm.

As shown in FIG. 1, an intrinsic amorphous semiconductor layer 7 is preferably disposed on the light receiving surface 10 a (main surface) of the semiconductor substrate 10. Thereby, carrier recombination on the main surface side surface is suppressed, and the efficiency of power generation is improved. The amorphous semiconductor layer 7 may be an i-type amorphous semiconductor layer. The amorphous semiconductor layer 7 is defined as a main surface amorphous semiconductor layer. The amorphous semiconductor layer 7 is preferably disposed on the entire main surface of the semiconductor substrate 10. The amorphous semiconductor layer 7 functions as a passivation film. The amorphous semiconductor layer 7 is preferably composed of a hydrogenated amorphous semiconductor containing silicon. Examples of the amorphous semiconductor include amorphous silicon, amorphous silicon carbide, amorphous silicon oxide, and amorphous silicon nitride. The thickness of the amorphous semiconductor layer 7 is not particularly limited, but may be in the range of 1 to 50 nm, for example. For example, the thickness of the amorphous semiconductor layer 7 is about 10 nm.

An antireflection layer 8 is preferably disposed on the amorphous semiconductor layer 7. Thereby, reflection of light is suppressed and light becomes easy to enter. The amorphous semiconductor layer 7 is preferably formed of a material that absorbs little incident light. The antireflection layer 8 can be formed of, for example, silicon nitride. The thickness of the antireflection layer 8 is not particularly limited, but may be, for example, in the range of 30 to 2000 nm. For example, the thickness of the antireflection layer 8 is about 70 nm.

A single layer having the functions of the amorphous semiconductor layer 7 and the antireflection layer 8 may be disposed on the light receiving surface 10 a of the semiconductor substrate 10. For example, silicon nitride or aluminum nitride can have such a function. Alternatively, an additional layer may be provided between the amorphous semiconductor layer 7 and the antireflection layer 8. The additional layer may be composed of, for example, an amorphous semiconductor layer doped with impurities forming the surface electric field layer, or a dielectric layer having a fixed charge.

The solar cell described above efficiently takes out minority carriers generated in the semiconductor substrate 10 by disposing the first electrode 11 over the entire surface of the second comb-shaped amorphous semiconductor layer 2. be able to. In addition, the electrode can be formed with the maximum area allowed by the processing accuracy. Then, the influence of series resistance due to in-plane conduction in the amorphous semiconductor layer is reduced. Therefore, the conversion efficiency of the solar cell is improved.

[Second Embodiment]
FIG. 3 shows a second embodiment of the solar cell. FIG. 4 shows a part of the back surface of the second embodiment of the solar cell. The reason why it is a part of the back surface is that a part of the comb shape is shown. Actually, the comb shape may have a larger number of comb teeth. In FIG. 3, a direction S perpendicular to the substrate to be viewed in plan is indicated by an arrow. In FIG. 4, the direction P in which light travels is indicated by a white arrow. In FIG. 4, the edge part 11a of the 1st electrode 11 is shown with the dashed-two dotted line. In FIG. 4, the region where the insulator layer 9 is disposed is indicated by hatching. In FIG. 4, the edge of the insulator layer 9 closer to the second electrode 12 is indicated by a broken line. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

The second embodiment includes an insulator layer 9 disposed between the first electrode 11 and the third amorphous semiconductor layer 3. This point is different from the first embodiment. Other configurations may be the same as those of the first embodiment.

The insulator layer 9 has a function of electrically insulating the layers. The insulator layer 9 suppresses contact between the first electrode 11 and the third amorphous semiconductor layer 3. The insulator layer 9 straddles the edge 11 a of the first electrode 11. The insulator layer 9 is disposed on the back surface 10 b of the semiconductor substrate 10 and is placed on the first electrode 11. The insulator layer 9 is in contact with the semiconductor substrate 10. The insulator layer 9 is in contact with the first electrode 11. The insulator layer 9 covers the end portion of the first electrode 11. The insulator layer 9 covers the side surface of the second amorphous semiconductor layer 2. The insulator layer 9 covers the side surface of the first amorphous semiconductor layer 1. By the insulator layer 9, the first amorphous semiconductor layer 1, the second amorphous semiconductor layer 2, and the first electrode 11 are connected to the third amorphous semiconductor layer 3 and the fourth non-crystalline semiconductor layer 3. It is electrically insulated from the crystalline semiconductor layer 4. In FIG. 3, one edge of the insulator layer 9 is drawn so as to coincide with the edge of the third amorphous semiconductor layer 3 and the edge of the fourth amorphous semiconductor layer 4. However, the edges do not necessarily coincide with each other, and the edge of the third amorphous semiconductor layer 3 and the edge of the fourth amorphous semiconductor layer 4 exist on the insulator layer 9. If you do. The presence of the insulator layer 9 reduces the leakage current between the electrodes. Insulator layer 9 facilitates electrical separation between the p-side electrode and the n-side electrode, so that the leakage current between the electrodes becomes very small. Therefore, the power generation efficiency is improved, and a solar cell with good characteristics can be obtained.

As shown in FIG. 4, the insulator layer 9 has a meandering shape in plan view. Since the insulator layer 9 is disposed along the shape of the edge of the comb teeth of the first electrode 11, it has a meandering shape.

The insulator layer 9 can be formed of an insulating material. The insulating material may be an inorganic material or an organic material. Examples of the material for the insulator layer 9 include silica, silicon nitride, alumina, and polyimide. The insulator layer 9 may be transparent, translucent, or opaque. The thickness of the insulator layer 9 is not particularly limited, but may be in the range of 5 to 200 nm, for example. The thickness of the insulator layer 9 is, for example, about 70 nm.

In the present embodiment, since the insulator layer 9 is present, the occurrence of leakage current can be suppressed even if the separation distance D between the first electrode 11 and the second electrode 12 is less than 10 μm. Therefore, the separation distance D may be less than 10 μm. For example, the second electrode 12 may be provided at a portion where the fourth amorphous semiconductor layer 4 is raised because the fourth amorphous semiconductor layer 4 is placed on the first electrode 11. Further, the first electrode 11 and the second electrode 12 may overlap with each other in plan view, and the separation distance D may be eliminated. However, considering the patterning accuracy of the electrodes, it is preferable that there is a separation distance D. The separation distance D is preferably 1 μm or more and 100 μm or less.

[Method for manufacturing solar cell]
Hereinafter, the manufacturing method of a solar cell is demonstrated.

FIG. 5 is a cross-sectional view showing an example of the method for manufacturing the solar cell of the first embodiment. FIG. 5 is composed of FIGS. 5A to 5J.

The method for manufacturing a solar cell includes the following steps:
Forming the first amorphous semiconductor layer 1;
Forming the second amorphous semiconductor layer 2;
Forming the first electrode 11;
Etching the first amorphous semiconductor layer 1, the second amorphous semiconductor layer 2 and the first electrode 11 into a comb shape;
Forming a third amorphous semiconductor layer 3;
Forming a fourth amorphous semiconductor layer 4;
Etching the third amorphous semiconductor layer 3 and the fourth amorphous semiconductor layer 4 into a comb shape;
Forming the second electrode 12;

Further explanation will be given below.

First, the semiconductor substrate 10 is prepared. An example of the semiconductor substrate 10 is an n-type single crystal silicon substrate. The semiconductor substrate 10 is cleaned, transported into a vacuum chamber, and heated. As a result, moisture adhering to the surface of the substrate is removed. Hereinafter, an example in which an n-type semiconductor substrate is used will be described. However, if a p-type semiconductor substrate is used, the n-type and p-type of each material may be interchanged.

Next, SiH ₄ (silane) gas is introduced into the vacuum chamber, and the first amorphous semiconductor layer 1 is formed on the back surface 10b (surface opposite to the light receiving surface 10a) of the semiconductor substrate 10 by PECVD. Form. This is a step of forming the first amorphous semiconductor layer 1. The first amorphous semiconductor layer 1 can be formed of i-type amorphous silicon. The first amorphous semiconductor layer 1 does not contain impurities. The first amorphous semiconductor layer 1 is intrinsic. Next, SiH ₄ gas, H ₂ (hydrogen) gas and B ₂ H ₆ (diborane) gas are introduced into the vacuum chamber, and the _second amorphous semiconductor layer 1 is formed on the first amorphous semiconductor layer 1 by PECVD. An amorphous semiconductor layer 2 is formed. This is a step of forming the second amorphous semiconductor layer 2. The second amorphous semiconductor layer 2 can be formed of p-type amorphous silicon. The second amorphous semiconductor layer 2 contains impurities. Impurities are doped. Next, the first electrode 11 is formed by sputtering, MOCVD (metal organic chemical vapor deposition), or printing. This is a step of forming the first electrode 11. The first electrode 11 can be formed of, for example, ITO or ZnO.

FIG. 5A shows a state after the first electrode 11 is formed. Here, as can be seen from FIG. 5A, the first amorphous semiconductor layer 1, the second amorphous semiconductor layer 2 and the first electrode 11 are not patterned on the semiconductor substrate 10, It is provided in layers.

Subsequently, as shown in FIG. 5B, an etching resist material is applied in a comb shape on the first electrode 11, and the etching resist material is solidified. As an etching resist material, a photoresist, pigment ink, polyimide, or the like may be used as long as it is a material that can be printed with high accuracy, has etching resistance, is easily peeled off after etching, and has little contamination. The etching resist material can be applied by a printing method. Examples of the printing method include an inkjet printing method and a screen printing method. An etching resist layer 21 is formed from the etching resist material. Then, as shown in FIG. 5C, the semiconductor substrate 10 on which the etching resist layer 21 is formed is immersed in an etching solution, and the first electrode 11, the second amorphous semiconductor layer 2, and the first amorphous semiconductor layer 10 are immersed. The portion of the quality semiconductor layer 1 that is not covered with the etching resist layer 21 is removed. This etching is wet etching. As the etching solution, for example, a mixed solution of an NH ₄ F (ammonium fluoride) aqueous solution and an H ₂ O ₂ (hydrogen peroxide) aqueous solution is used. Etching may be performed by dry etching. Examples of dry etching include reactive ion etching using SF ₆ (sulfur hexafluoride), NF ₃ (nitrogen trifluoride), CF ₄ (carbon tetrafluoride), and the like. Thereafter, as shown in FIG. 5D, the etching resist layer 21 is removed with a resist removing material. As the resist removing material, for example, acetone is used. Accordingly, the first amorphous semiconductor layer 1, the second amorphous semiconductor layer 2, and the first electrode 11 are patterned into a comb shape. A series of these steps is a step of etching the first amorphous semiconductor layer 1, the second amorphous semiconductor layer 2, and the first electrode 11 into a comb shape.

Then, by introducing SiH ₄ gas into the vacuum chamber, by PECVD, the first electrode 11, and, on the back surface 10b of the semiconductor substrate 10 exposed by the etching, the third amorphous-based semiconductor layer 3 Form. This is a step of forming the third amorphous semiconductor layer 3. The third amorphous semiconductor layer 3 can be formed of i-type amorphous silicon. The third amorphous semiconductor layer 3 does not contain impurities. The third amorphous semiconductor layer 3 is intrinsic. The third amorphous semiconductor layer 3 is laminated so as to include a portion between the comb teeth from which the first electrode 11 is separated.

Next, SiH ₄ gas, H ₂ gas and PH ₃ (phosphine) gas are introduced into the vacuum chamber, and the fourth amorphous semiconductor layer 4 is formed by PECVD. This is a step of forming the fourth amorphous semiconductor layer 4. The fourth amorphous semiconductor layer 4 can be formed of n-type amorphous silicon. The fourth amorphous semiconductor layer 4 contains impurities. Impurities are doped. The fourth amorphous semiconductor layer 4 is laminated so as to include a portion between the comb teeth from which the first electrode 11 is separated.

FIG. 5E shows a state after the fourth amorphous semiconductor layer 4 is formed. Here, as can be seen from FIG. 5E, the third amorphous semiconductor layer 3 and the fourth amorphous semiconductor layer 4 are provided in layers on the back side of the semiconductor substrate 10 without being patterned. It has been.

Subsequently, as shown in FIG. 5F, an etching resist material is applied in a comb shape on the fourth amorphous semiconductor layer 4 to solidify the etching resist material. As an etching resist material, a photoresist, pigment ink, polyimide, or the like may be used as long as it is a material that can be printed with high accuracy, has etching resistance, is easily peeled off after etching, and has little contamination. The etching resist material can be applied by a printing method. Examples of the printing method include an inkjet printing method and a screen printing method. An etching resist layer 22 is formed from the etching resist material. Then, as shown in FIG. 5G, the semiconductor substrate 10 on which the etching resist layer 22 is formed is immersed in an etching solution, and the fourth amorphous semiconductor layer 4 and the third amorphous semiconductor layer 3 are formed. Then, the portion not covered with the etching resist layer 22 is removed. This etching is wet etching. As the etching solution, for example, a mixed solution of an HF (hydrofluoric acid) aqueous solution and an H ₂ O ₂ (hydrogen peroxide) aqueous solution is used. Etching may be performed by dry etching. Examples of dry etching include reactive ion etching using SF ₆ (sulfur hexafluoride), NF ₃ (nitrogen trifluoride), CF ₄ (carbon tetrafluoride), and the like. Etching is performed so as not to etch the first electrode 11 and the layer closer to the semiconductor substrate 10 than the first electrode 11. As a result, the first electrode 11 is exposed. Thereafter, as shown in FIG. 5H, the etching resist layer 22 is removed by a resist removing material. As the resist removing material, for example, acetone is used. As a result, the third amorphous semiconductor layer 3 and the fourth amorphous semiconductor layer 4 are patterned into a comb shape. A series of these steps is a step of etching the third amorphous semiconductor layer 3 and the fourth amorphous semiconductor layer 4 into a comb shape.

Next, the second electrode 12 is formed in a pattern on the fourth amorphous semiconductor layer 4. This is a step of forming the second electrode 12. The second electrode 12 is formed in a comb-shaped pattern. The second electrode 12 can be formed by applying an ink containing an electrode material by a printing method and performing a heat treatment. Examples of the printing method include an inkjet printing method and a screen printing method.

The second electrode 12 is formed apart from the first electrode 11. The second electrode 12 can be formed on the flat portion 4 a of the fourth amorphous semiconductor layer 4. As described above, the distance D between the second electrode 12 and the first electrode 11 is preferably 10 μm or more in order to suppress a short circuit between the electrodes and a leakage current. The separation distance D is preferably 100 μm or less in order to reduce the direct resistance of majority carriers to electrons.

Next, the first collector electrode 5 and the second collector electrode 6 are formed in a comb shape. The first collector electrode 5 is formed on the first electrode 11. The second collector electrode 6 is formed on the second electrode 12. The first collector electrode 5 and the second collector electrode 6 are formed in a comb-shaped pattern that meshes with each other. The first collector electrode 5 and the second collector electrode 6 can be formed by applying a metal material by a printing method. Examples of the printing method include an inkjet printing method and a screen printing method. The first collector electrode 5 and the second collector electrode 6 are made of, for example, Ag (silver). The first collector electrode 5 and the second collector electrode 6 are preferably formed simultaneously. Thereby, the manufacturing process is simplified. FIG. 5I shows the state after the collector electrode is formed.

Note that the second electrode 12, the first collector electrode 5, and the second collector electrode 6 may be formed by patterning other than the printing method. For example, they can be patterned and formed by a sputtering film forming method using a mask. Alternatively, for example, after a layer is formed on one surface, an etching resist material may be formed in a patterned meandering shape, and may be patterned in a comb shape by wet etching.

When the ohmic contact with the fourth amorphous semiconductor layer 4 can be formed and the diffusion of the electrode material does not affect, the second electrode 12 is made of the material of the second collector electrode 6 described above. May be formed. In that case, the second electrode 12 can be formed on the fourth amorphous semiconductor layer 4 when the first collector electrode 5 is formed. At this time, the second collector electrode 6 may be omitted. This structure may be a structure in which the second electrode 12 also has the second collector electrode 6.

After the collector electrode is formed, the light receiving surface 10a (main surface) of the semiconductor substrate 10 is cleaned, the semiconductor substrate 10 is placed in a vacuum chamber, SiH ₄ gas is introduced into the vacuum chamber, and the light receiving surface is formed by PECVD. An amorphous semiconductor layer 7 is formed on 10a. The amorphous semiconductor layer 7 can be formed of i-type amorphous silicon. Next, the antireflection layer 8 is formed on the amorphous semiconductor layer 7 by sputtering, for example. Thus, it is preferable to have a step of forming the amorphous semiconductor layer 7 on the light receiving surface side. Further, it is preferable to have a step of forming the antireflection layer 8. It should be noted that the amorphous semiconductor layer 7 and the antireflection layer 8 are appropriately formed before the formation of the first amorphous semiconductor layer 1 or after the formation of the second electrode 12 and before the formation of the collector electrode. May be formed.

Thus, the solar cell of the first embodiment shown in FIG. 5J is obtained.

In the above manufacturing method, the patterning of the amorphous semiconductor layer is performed by etching. Therefore, impurity contamination from the mask is prevented as in the case of patterning the amorphous semiconductor layer using a mask when forming the amorphous semiconductor layer. Thereby, deterioration of the solar cell characteristics is prevented. In addition, the n-type structure and the p-type structure can be arranged with high accuracy so as not to have an excessive gap while maintaining electrical isolation in a comb shape that is engaged with each other. In addition, when the etching mask is formed by using the printing method, the manufacturing process is simplified and the yield is improved, so that the manufacturing cost can be reduced compared to the photolithography method, for example.

Hereinafter, a method for manufacturing the solar cell of the second embodiment will be described.

FIG. 6 is a cross-sectional view showing an example of a method for manufacturing the solar cell of the second embodiment. FIG. 6 is configured from FIGS. 6A to 6D. The figure common to FIG. 5 and the figure understandable from FIG. 5 are omitted.

The method for manufacturing a solar cell according to the second embodiment includes a step of forming the insulator layer 9. Other than that may be the same as the manufacturing method of the solar cell of the first embodiment.

The step of forming the insulator layer 9 is performed after the step of etching the first amorphous semiconductor layer 1, the second amorphous semiconductor layer 2, and the first electrode 11. FIG. 6A corresponds to FIG. 5D. After performing the step of forming the insulator layer 9 after FIG. 6A, the insulator layer 9 is formed at the end portion of the first electrode 11 as shown in FIG. 6B. The insulator layer 9 is formed so as to straddle the boundary between the first electrode 11 and the portion of the semiconductor substrate 10 exposed by etching. The insulator layer 9 has a meandering shape along the comb-teeth edge 11 a of the first electrode 11. The insulator layer 9 can be formed by a printing method. By forming the insulator layer 9 by a printing method, unlike a normal sputtering method or PECVD method, the physical impact can be reduced and formed at a low temperature, so that an amorphous semiconductor layer (amorphous silicon layer) is formed. Damage and modification are suppressed, and the solar cell efficiency is improved. For example, the insulator layer 9 is formed by applying the material of the insulator layer 9 in a pattern by a printing method and heating. The heating is preferably performed at a temperature of 200 ° C. or lower. Firing is performed by heating. Examples of the printing method include an inkjet printing method and a screen printing method. Further, a patterning method other than the printing method may be employed. For example, the insulator layer 9 can be formed by patterning by a sputtering film forming method using a mask. Alternatively, for example, the insulating layer 9 may be patterned by wet etching after an etching resist material is formed in a patterned meandering shape after a layer is formed on one surface.

After the formation of the insulator layer 9, as shown in FIG. 6C, the third amorphous semiconductor layer 3 and the fourth amorphous semiconductor layer 4 are formed and patterned. Thereafter, as shown in FIG. 6D, the first collector electrode 5 and the second collector electrode 6 are formed. Finally, by forming the amorphous semiconductor layer 7 and the antireflection layer 8, the solar cell shown in FIG. 3 is obtained.

Thus, when the insulator layer 9 is formed, electrical separation between the n-type electrode and the p-type electrode can be increased, and therefore, a highly efficient solar cell in which leakage current is suppressed is manufactured. Can do.

[Example 1]
Regarding the solar cell of the first embodiment, the influence of the distance between the first electrode 11 and the second electrode 12 on the characteristics of the solar cell was examined by computer simulation. The semiconductor substrate 10 was an n-type single crystal silicon substrate. The amorphous semiconductor layers (on the first to fourth and main surfaces) were all amorphous silicon layers. The first amorphous semiconductor layer 1 and the third amorphous semiconductor layer 3 (i-type amorphous silicon layer) have a thickness of 5 nm and an electron concentration of 1 × 10 ¹⁵ cm ⁻³ . . The second amorphous semiconductor layer 2 (p-type amorphous silicon layer) had a thickness of 5 nm, a comb tooth width of 1.5 mm, and a carrier concentration of 5 × 10 ¹⁸ cm ⁻³ . The fourth amorphous semiconductor layer 4 (n-type amorphous silicon layer) had a thickness of 5 nm and a carrier concentration of 8 × 10 ¹⁸ cm ⁻³ . The amorphous semiconductor layer 7 (i-type amorphous silicon layer) on the light receiving surface had a thickness of 5 nm and an electron concentration of 1 × 10 ¹⁵ cm ⁻³ .

Here, the width of the portion where the second amorphous semiconductor layer 2 and the fourth amorphous semiconductor layer 4 overlap in a plan view is 20 μm. This width is equal to the width at which the first electrode 11 and the third amorphous semiconductor layer 3 are in contact. The width of the second electrode 12 was 200 μm.

The mobility of electrons in the n-type amorphous silicon layer was 5 cm ² / Vs. the hole mobility of the p-type amorphous silicon layer (.mu.p) was duplicate of 0.3 cm ² / Vs and 0.0001 cm ² / Vs. The reason for the two types is that the mobility of holes cannot be accurately determined. The semiconductor substrate 10 (n-type single crystal silicon substrate) had a carrier concentration of 5 × 10 ¹⁶ cm ⁻³ and a carrier lifetime of 5 ms. Other physical parameters are Djicknoum Diouf, Jean-Paul Kleider, and Christophe Longeau, `` Two-Dimensional Simulations of Interdigitated Back Contact Silicon Heterojunctions Solar Cells '', Wilfred GJHMvan Sark, Lars Korte, and Francesco Roca (Eds.), “Physics and Technology of Amorphous-Crystalline Heterostructure Silicon Solar Cells ”(Springer, Berlin, 2012), Chapter 15. ATLAS manufactured by SILVACO was used for the simulation.

FIG. 7 shows the distance between the first electrode 11 and the second electrode 12 (electrode separation distance D) and the sun in the hole mobility (μp) in two types of p-type amorphous silicon layers. It is a graph which shows the relationship with the relative conversion efficiency of a battery. The graph is normalized with respect to the maximum value.

In the graph of FIG. 7, when the hole mobility (μp) is 0.3 cm ² / Vs, the electrode separation distance is 10 μm, the conversion efficiency is maximum, and the hole mobility (μp) is 0. At 0001 cm ² / Vs, the electrode separation distance is 20 μm, and the conversion efficiency is maximum. If the electrode separation distance is smaller than these maximum values, the conversion efficiency is considered to decrease because the leak current between the electrodes increases. Further, if the distance between the electrodes becomes too small, there is a possibility of short circuit. Taking into account variations in the processing accuracy of the electrodes, the electrode separation distance is preferably 10 μm or more. In the graph, the conversion efficiency gradually decreases as the electrode separation distance increases. This is presumably because the series resistance to electrons which are majority carriers in the semiconductor substrate 10 (n-type single crystal silicon substrate) increases. From the graph, it can be seen that when the separation distance D exceeds 100 μm, the conversion efficiency decreases by 2% or more in relative value. Therefore, the electrode separation distance is preferably 100 μm or less. Such a tendency is considered to be the same when the width, thickness, carrier concentration and the like of the amorphous silicon layer are changed. That is, when the distance between the electrodes is 10 μm or more and 100 μm or less, a solar cell with good characteristics with a small leakage current between the electrodes can be obtained. These dimensions are within the processing accuracy that can be realized by a simple patterning method such as a printing method, and the manufacturing cost and the manufacturing time can be reduced.

[Example 2]
About the solar cell of 2nd Embodiment, the influence which insertion of the insulator layer 9 has on the characteristic of a solar cell was investigated by simulation of the computer. The calculation parameters and method were the same as in Example 1. The surface recombination velocity at the interface between the semiconductor substrate 10 and the insulator layer 9 was 10 cm / s.

As a result, the leakage current between the electrodes is reduced by inserting the insulator layer 9, the open-circuit voltage and the fill factor are improved, and the conversion efficiency is increased by about 5% compared to the case without the insulator layer 9. It has been shown. Further, when the width of the insulator layer 9 in contact with the semiconductor substrate 10 was changed from 10 μm to 100 μm, the conversion efficiency was reduced within 5%. Thus, the arrangement of the insulator layer 9 makes it possible to obtain a solar cell with good characteristics with a small leakage current between the electrodes. The dimension of the insulator layer 9 is within the patterning accuracy that can be handled by the printing method. That is, these dimensions are within the processing accuracy that can be realized by a simple patterning method such as a printing method, and the manufacturing cost and the manufacturing time can be reduced.

[Comparison with conventional example]
Japanese Patent Publication No. 2013-168605 discloses a solar cell. However, in this solar cell, the p-type electrode is formed only on a part of the p-type amorphous silicon layer. Therefore, holes that are minority carriers in the semiconductor substrate cannot be efficiently extracted to the outside. The same applies to Japanese Patent Publication No. 2013-131586. On the other hand, in the solar cell of the present disclosure, since the p-type electrode can be formed on the entire surface of the p-type amorphous semiconductor layer (amorphous silicon layer), holes that are minority carriers in the semiconductor substrate are efficiently used. It can be taken out well and efficiency is improved.

Japanese Patent Publication No. 2005-101151 discloses a solar cell. In this document, a structure in which a p-type electrode is formed on one surface of a p-type amorphous silicon layer is disclosed as a second embodiment. However, this solar cell does not have a comb shape in which the p-type silicon layer and the n-type silicon layer are engaged with each other, the p-type electrode is covered with the silicon layer, and the n-type electrode Is formed in a deformed portion of the silicon layer. With this structure, a leak current is likely to occur. On the other hand, the solar cell of this indication can make it difficult to generate the leak current between electrodes compared with the structure of this literature.

Patent Cooperation Treaty International Publication No. WO 2010/113750 discloses solar cells. This solar cell has an insulator layer. However, even in this solar cell, the p-type electrode is formed only on a part of the p-type amorphous silicon layer. Therefore, holes that are minority carriers in the semiconductor substrate cannot be efficiently extracted to the outside. The same applies to Japanese Patent Publication No. 2009-200267.

US Patent US8525018 discloses a solar cell. This solar cell has an insulator layer and a p-type electrode formed on one surface of a p-type amorphous silicon layer. However, since the insulator layer is also disposed between the p-type amorphous silicon layer and the semiconductor substrate, holes that are minority carriers cannot be taken out at this portion. On the other hand, in the solar cell of the present disclosure, the insulator layer can have a structure that is not disposed between the p-type amorphous semiconductor layer (amorphous silicon layer) and the semiconductor substrate. Are efficiently extracted to the outside, and the efficiency is improved.

Claims

A semiconductor substrate of one conductivity type having a light receiving surface and a back surface;
An intrinsic first amorphous semiconductor layer disposed on the back surface of the semiconductor substrate and having a comb shape;
A second amorphous semiconductor layer that is disposed on the first amorphous semiconductor layer and includes an impurity having a conductivity type different from that of the semiconductor substrate;
A first electrode disposed on the entire surface of the second amorphous semiconductor layer;
An intrinsic third amorphous semiconductor layer which is disposed on the back surface of the semiconductor substrate and has a comb shape which meshes with the first amorphous semiconductor layer and partially overlaps the first electrode in plan view; ,
A fourth amorphous semiconductor layer including an impurity disposed on the third amorphous semiconductor layer and including an impurity having the same conductivity type as the semiconductor substrate;
And a second electrode disposed on the fourth amorphous semiconductor layer.
The first electrode and the second electrode are separated in a plan view,
The solar cell according to claim 1, wherein a distance between the first electrode and the second electrode is 10 μm or more and 100 μm or less.
The solar cell according to claim 1, further comprising an insulator layer disposed between the first electrode and the third amorphous semiconductor layer.
Forming an intrinsic first amorphous semiconductor layer on the back surface of the one-conductivity-type semiconductor substrate having a light-receiving surface;
Forming a second amorphous semiconductor layer containing an impurity having a conductivity type different from that of the semiconductor substrate on the first amorphous semiconductor layer;
Forming a first electrode on the second amorphous semiconductor layer;
Etching the first amorphous semiconductor layer, the second amorphous semiconductor layer, and the first electrode into a comb shape on the back surface of the semiconductor substrate;
Forming an intrinsic third amorphous semiconductor layer including the portion of the semiconductor substrate exposed by the etching on the back surface of the semiconductor substrate provided with the first electrode;
Forming a fourth amorphous semiconductor layer containing an impurity having the same conductivity type as that of the semiconductor substrate on the third amorphous semiconductor layer;
The third amorphous semiconductor layer and the fourth amorphous semiconductor layer are engaged with the first electrode, and a part of the third amorphous semiconductor layer is the first electrode. Etching into a comb shape overlapping in plan view,
And a step of forming a second electrode on the fourth amorphous semiconductor layer.
The method further comprises a step of forming an insulator layer so as to straddle a boundary portion between the first electrode etched into a comb shape and the back surface of the semiconductor substrate exposed by etching the first electrode. Item 5. A method for producing a solar cell according to Item 4.
6. The step of etching the first amorphous semiconductor layer, the second amorphous semiconductor layer, and the first electrode includes forming an etching mask by a printing method. The manufacturing method of the solar cell of description.